Patent Application
20110120979
The present invention relates to a mash seam welding method and apparatus in which two metal plates are placed to overlap each other at their end portions, and the overlapping portions are pressed by a pair of upper and lower electrode wheels and continuously welded together by applying a welding current to the overlapping portions, followed by joining the metal plates.
A mash seam welder employs a welding method as below. Two metal plates are placed to overlap each other at their end portions. The overlapping portions are pressed by a pair of electrode wheels and continuously welded together by applying a welding current thereto. At the same time, the joint portion softened by being heated to high temperature is rolled by the electrode wheels to reduce the thickness of the joint portion. However, this welding method cannot roll the joint portion to a level corresponding to the base material thickness. There is a problem in that the thickness of the joint portion is increased to approximately 120% to 160% of the thickness of the base material (the metal plate), which forms a step between the joint portion and the base material.
The following method is proposed as a method of reducing the thickness of the joint portion. A pair of pressure rollers is installed adjacently to and on one side of a pair of upper and lower electrode wheels. Before mash seam welding, the overlapping portions of the metal plates are rolled by the pressure rollers by moving a base frame supporting the electrode wheels and the pressure rollers in a pressure roller preceding direction. After the completion of the rolling, the metal plates overlapping each other are made slightly away from each other to reduce the thickness of the joint portion. Thereafter, the overlapping portion is pressed by the electrode wheels by moving the base frame in the opposite direction and is continuously subjected to mash seam welding by applying welding current thereto. Further, the joint portion is rolled by the pressure rollers to reduce its thickness. See Patent Documents 1 and 2.
In order to reduce the thickness of a joint portion subjected to mash seam welding and to reduce tack time, a method and apparatus are proposed as below. First and second pairs of upper and lower pressure rollers are installed adjacently to and on both sides of a pair of upper and lower electrode wheels. Overlapping portions of metal plates are rolled by the first pressure rollers by moving a base frame supporting the electrode wheels and the pressure rollers in one first roller preceding direction. Thereafter, the rolled portion is pressed by the pair of electrode wheels following the pressure rollers and is continuously subjected to mash seam welding by applying welding current thereto. Further, the joint portion is rolled by the second pressure rollers following the electrode wheels to reduce its thickness. See Patent Document 1 and Patent Document 2.
If two metal plates made to overlap each other are joined to each other by a mash seam welding method, a molten-solidified portion called a nugget is formed at a thickness-wise central portion of the metal plates gripped by the pair of electrode wheels. The greater a difference in thickness between metal plates is, the more a joint interface is away from the thickness-wise central portion of the metal plates made to overlap each other. Therefore, since there is a problem in that the joint interface deviates from the nugget and joint strength decreases, it is necessary to limit a thickness ratio between metal plates to be joined to each other.
In order to alleviate restriction on a thickness ratio between metal plates to be joined to each other, the following means is proposed. A contact area between each of electrode wheels and material is set to roughly equalize the respective thicknesses of the metal plates after mash seam welding, so that a nugget is formed at a joint interface to increase an allowable joint thickness ratio. See Patent Document 3.
The mash seam welder employs the welding method as below. The two metal plates are made to overlap each other. The overlapping portions are pressed by the pair of electrode wheels and continuously welded together by applying a welding current thereto. At the same time, the joint portion heated to high temperature to be softened is rolled by the electrode wheels to reduce the thickness thereof. Therefore, the electrode wheels perform, through their rolling, most of plastic working used for reducing the thickness of joint materials. The plastic flow of the joint portion reduced in thickness prevails in the rolling direction of the electrode wheels. However, the joint portion has a relationship of a continuous body with the base material of the metal plate adjacent thereto. Therefore, the plastic flow in the rolling direction is restrained by the base material. Consequently, the joint portion cannot be rolled to the thickness of the base material. The thickness of the joint portion based on the mash seam welding method is increased to approximately 120% to 160% of the thickness of the base material (the metal plate). Since the joint portion and the base material are different in thickness from each other, a step having a high stress concentration factor is formed at the joint portion. If stress is applied to the joint portion, then the joint portion disadvantageously will have a significantly reduced strength. In other words, there is a problem in that this limits the application range of mash seam welding. In addition, there are problems in that a steep step scratches a work roll on a steel plate process line and productivity and yield are lowered.
For example, the joint portion of the mash seam welder is stepwise increased in thickness to approximately 120% to 160% of a base material. If the mash seam welder is applied to a cold rolling equipment having large total rolling reduction as it is, therefore, the step portion of the joint portion is interfolded into the base material in a cracked manner. Consequently, an effective cross-sectional area is reduced at the joint portion, called strip, of the metal plate. This increases a tensile stress with respect to the tensile force applied during cold rolling. In addition, the leading end of the step interfolded in a cracked manner becomes a singular stress field, which drastically increases fracture probability. This poses a problem as below. Since an inexpensive small-sized mash seam welder cannot be applied to cold rolling equipments having large total rolling reduction, the cold rolling equipments have to use a flash butt welder or a laser beam welder, which is expensive and large-sized.
A mash seam welder that can inexpensively join together steel plates having different thicknesses and material strengths is applied to tailored blanks. However, the mash seam welder cannot be applied to the joining of a portion where a joint portion increased in thickness leads to a problem with forming performance and of a portion where a problem of stress concentration resulting from the step defined at the joint portion occurs. Therefore, an expensive laser beam welder has to be applied to the tailored blanks.
An inexpensive mash seam welder is applied as a joining machine for making production processes continuous, to production lines such as a continuous annealing line, a galvanizing line and the like in steel production for the purpose of an improvement in yield and in productivity. However, as described above, the mash seam welding increases the thickness of the joint portion to form the steep step. When the joint portion passes through a skin pass rolling mill, therefore, the following operating method is employed in order to prevent a work roll from being scratched and to prevent the step defined at the joint portion from being mark-transferred onto the work roll. A line speed is lowered before and after the skin pass rolling mill and the work roll of the rolling mill is opened or a rolling force is lowered. This poses a problem of lowering productivity and yield.
Of the conventional methods described in Patent Document 1 and Patent Document 2, the former method can reduce the thickness of the joint portion to approximately 110% of the thickness of the base material. In the former method, after the completion of the rolling, the metal plates made to overlap each other are made slightly away from each other to reduce the thickness of the joint portion. Thereafter, the joint portion is subjected to mash seam welding and further is rolled by the pressure rollers. However, if the distance between the ends of the metal plates made away from each other is too large, a dent is formed near the joint portion due to the rolling of the pressure rollers before the welding. If the distance is not enough, the increased amount of thickness of the joint portion is increased. Because of this, an optimum range of a set amount of distance exists only at a pinpoint. That is to say, robustness is poor. Therefore, it is difficult to stably ensure joint strength with high quality.
Of the conventional methods described in Patent Document 1 and Patent Document 2, the method in which pressure rollers are installed on both sides of the electrode wheels and rolling before welding, welding and rolling after welding are continuously performed by moving the base frame in one direction has a problem in that the thickness of the joint portion cannot sufficiently be reduced. Specifically, the metal plates are gripped by the clamp devices so that an overlapping amount during the mash seam welding may not be deviated, and is restrained in the direction perpendicular to the welding direction by the clamp devices. Therefore, the rolling by the pressure rollers after the welding has a limitation on an amount of plastic flow in the direction perpendicular to the welding line and mainly allows metal to plastically flow in the roller-traveling direction. Similarly to the rolling by the electrode wheels during the mash seam welding described above, the plastic flow of the rolled portion by the pressure rollers are restrained by the base material so that extension is significantly limited. Therefore, the joint portion cannot be reduced in thickness to the thickness of the base material. In the rolling by the pressure rollers, the volume of the joint portion whose thickness has been reduced by the rolling is absorbed by being made to plastically flow in the longitudinal direction of the joint portion to increase the length of the joint portion. This causes an extension difference between the base material and the joint portion elongated by the pressure rollers, which poses a problem in that the joint portion is bent or deformed in a wavelike fashion.
Because of these situations, it has been said that it is difficult for the conventional mash seam welding method to perform the joining along while suppressing an increase in the thickness of the joint portion so as not to form the step between the joint portion and the base material. Therefore, a mash seam welding method has been desired that stably reduce the increased amount of thickness and step gradient of a joint portion and provides a high degree of joint strength.
On the other hand, in the mash seam welding, a nugget is formed at the thickness-wise central portion of two metal plates pressed by a pair of electrode wheels. If the two metal plates have a large different thickness, there is a problem in that a portion where a nugget is formed deviates from a joint interface, which lowers the joint strength. In fact, a thickness ratio between two metal plates to be joined is limited to approximately 1:1.5 or lower and the mash seam welding is not applied to the thickness ratio higher than such a thickness ratio.
The following method has been proposed as a method of solving such a problem. As disclosed in Patent Document 3, a pair of electrode wheels are installed rotatably around corresponding axes parallel to each other, and in such electrode wheels, a contact area on the side of a thick metal plate is made smaller than that of the electrode wheel on the side of a thin metal plate. This roughly equalizes the thicknesses of the metal plates after mash seam welding. However, to quantitatively control a difference in thickness between the two metal plates, the overlapping portions of the metal plates have to be disposed at the ends of the electrode wheels. For example, if a metal plate with a thickness of 2 mm is joined to a metal plate with a thickness of 3 mm, the overlapping amount of the metal plates generally corresponds to the thickness of the metal plate. Therefore, the contact width between the electrode wheel and the material is approximately 2 to 3 mm. If the joint portion is disposed at a barrel end of the electrode wheel and surface pressure between the electrode wheel and the material is maintained at a required accuracy, there is a problem as below. A clearance between vertically operating electrode wheel frames, a clearance between electrode wheel bearings, and a wear volume of the electrode wheel have to be controlled at a level of as high as approximately 0.2 to 0.3 mm. In this way, positioning accuracy in the joint-width direction has to be increased. Additionally, there is a problem in that also clamp devices which determine the position of the metal plate require a high degree of rigidity and accuracy, resulting in the installation being increased in size and in cost. Further, there is still a problem as below. Even if the nugget can be formed at the central portion of the joint interface, the thickness of the joint portion cannot be made as thick as that of the base material. Therefore, there is a limitation on application of this mash seam welding to a portion for which fatigue strength is required.
A first object of the present invention is to provide a mash seam welding method and apparatus which allow a reduction in the step gradient of a joint portion of two metal plates and can ensure a high degree of joint strength.
A second object of the present invention to provide a mash seam welding method and apparatus that can form a nugget formed by mash seam welding, at a joint interface to improve joint strength and can increase an allowable joint difference-thickness ratio with a relatively simple and inexpensive configuration in the case where metal plates having different thicknesses are joined to each other.
A first invention to solve the above-mentioned problems is characterized in that in a mash seam welding method in which two metal plates are placed to overlap each other at their end portions, and the overlapping portions are pressed by a pair of upper and lower electrode wheels and continuously welded together by applying a welding current to the overlapping portions, followed by joining the metal plates, respective axes of the electrode wheels are tilted in a horizontal plane in respective directions opposite to each other with respect to a straight line perpendicular to a welding line defined on the overlapping portions of the two metal plates, and then the electrode wheels are positively driven to thereby join the two metal plates.
As described above, the axes of the electrode wheels are tilted and the two metal plates are joined to each other while the electrode wheels are positively driven. A shearing force in a direction perpendicular to the welding line is applied to the overlapping portions of the metal plates. This applies the shear deformation in the same direction to the overlapping portions. Plastic flow in the direction perpendicular to the welding line occurs in addition to the plastic flow in the direction of the welding line provided by rolling of the conventional electric wheels. The plastic flow in the direction perpendicular to the welding line significantly reduces the increased amount of thickness of the overlapping portions (the joint portion) after the joining. Consequently, immediately thereafter, the joint portion is rolled by the pressure rollers to further reduce the increased amount of thickness of the joint portion, thereby significantly reducing the step gradient. Because of the reduced step gradient, the stress concentration factor can be reduced and a high degree of joint strength can be ensured.
If the two metal plates have different thicknesses, the tilt angles of the axes of the electrode wheels are adjusted according to the thicknesses of the metal plates. The reduced amount of thickness of each metal plate at the overlapping portions is adjusted. The metal plates are joined to each other so that the nugget is not deviated from the joint interface. In this way, the stress concentration factor is reduced due to the reduced step gradient, and in addition thereto, the nugget is formed at the joint interface, and this can drastically improve the joint strength of the joint portion and can increase an allowable joint difference-thickness amount to increase the flexibility of operation. Additionally, because of only the configuration in which the pair of electrode wheels is tilted and positively driven, the mash seam welding method can be realized with a relatively simple and inexpensive configuration.
A second invention to solve the above-mentioned problems is characterized in that in the mash seam welding method according to the first invention, the respective axes of the electrode wheels are each tilted with respect to the straight line perpendicular to the welding line so that respective travel-directional portions of the electrode wheels face in the horizontal plane toward an extending direction of the metal plate with which the electrode wheels first come into contact, for joining the two metal plates.
With this, it is possible to prevent the ends of the metal plates at the overlapping portions from biting into and scratching the electrode wheels when the electrode wheels travel on the overlapping portions along with the progress of the welding. Consequently, it is possible to prevent spattering attributable to such scratches from occurring during the welding.
A third embodiment to solve the above-mentioned problems is characterized in that in the mash seam welding method according to the first or second invention, the two metal plates have different thicknesses, and a tilt angle of the axis of the electrode wheel on a side where a metal plate has a larger thickness is made greater than that of the axis of the electrode wheel on the side where a metal plate has a smaller thickness.
As described above, the tilt angle of the axis of the electrode wheel on the side where the metal plate has a larger thickness is made greater. This increases the reduced amount of thickness of the metal plate on the larger thickness side and makes it roughly equal to the reduced amount of thickness of the metal plate having a smaller thickness. In this way, the metal plates are joined to each other so that the nugget is formed at the joint interface, which can improve joint strength.
A fourth invention to solve the above-mentioned problems is characterized in that in the mash seam welding method according to any one of the first to the third invention, at least one of processes before the start of the welding of the overlapping portions and after the completion of the welding of the overlapping portions selects a first setting in which the pair of electrode wheels are brought into contact with each other or a second setting in which the pair of electrode wheels are not brought into contact with each other or are brought into contact with each other at a light load compared with the pressing force during the welding, and in the first setting the pair of electrode wheels is made non-driven and in the second setting the pair of electrode wheels is made driven.
This can prevent an excessive thrust force from being applied to the upper and lower electrode wheels, thereby elongating the operating lives of the bearings for the electrode wheels. Further, the wear of the upper and lower electrode wheels is suppressed, leading to a reduction in running cost.
A fifth invention to solve the above-mentioned problems is characterized in that in the mash seam welding method according to any one of the first to the fourth invention, after the two metal plates have been joined to each other by the mash seam welding, respective axes of a pair of pressure rollers are tilted in a horizontal plane with respect the straight line perpendicular to the welding line, and a step defined at the joined portion is rolled in a traveling direction of the pressure rollers by positively driving the pressure rollers.
As described above, the respective axes of the pair of upper and lower pressure rollers are tilted and the joint portion is rolled while the pair of pressure rollers are positively driven. Therefore, similarly to the case where the respective axes of the pair of upper and lower electrode wheels are tilted, a shearing force in a direction perpendicular to the welding line is applied to the joint portion. This applies the shear deformation to the joint portion. Shear flow in the direction perpendicular to the welding line significantly reduces the increased amount of thickness of the joint portions. Consequently, during both the mash seam welding by the electrode wheels and the rolling by the pressure rollers, the increased amount of thickness is reduced by the shear deformation in the direction perpendicular to the welding line. In the joining of the metal plates having the same thickness, the joint portion can surely be rolled to a thickness corresponding to the base material thickness of the metal plate and thereby the step is smoothed. In the joint portion of the metal plates having different thicknesses, the step can be smoothed and the step gradient can significantly be reduced. Consequently, the stress concentration factor can more reliably be reduced to ensure a high degree of joint strength compared with the case where only the axes of the electrode wheels are tilted.
A sixth invention to solve the above-mentioned problems is characterized in that in the mash seam welding method according to the fifth invention, the respective axes of the pressure rollers are each tilted with respect to the straight line perpendicular to the welding line so that respective travel-directional portions of the pressure rollers face in a horizontal plane toward a direction opposite to an extending direction of the metal plate concerning a metal material with which the pressure rollers first come into contact, and the step defined at the joint portion is rolled in the traveling direction.
This can prevent the step portion from being interfolded into the base material of the metal plate. Therefore, it is possible to prevent a crack-like defect (non-welded defect) formed when the step portion is interfolded into the base material. Thus, the quality of the joint portion is enhanced.
A seventh invention to solve the above-mentioned problems is characterized in that in a mash seam welding apparatus in which two metal plates are placed to overlap each other at their end portions, and the overlapping portions are pressed by a pair of upper and lower electrode wheels and continuously welded together by applying a welding current to the overlapping portions, followed by joining the metal plates, the electrode wheels are installed in such a manner that axes of the electrode wheels are tilted in a horizontal plane in respective directions opposite to each other with respect to an axis perpendicular to a welding line defined on the overlapping portions of the two metal plates.
With this, in the mash seam welding method according to the first invention, a manufacturing facility can be provided that can achieve the following. The step gradient of the joint portion of the two metal plates can be reduced. Therefore, the stress concentration factor can be reduced and a high degree of joint strength can be ensured. In addition, if the two metal plates have different thicknesses, with a relatively simple and inexpensive configuration a nugget formed by the mash seam welding is formed at the joint interface to increase the joint strength, thereby increasing an allowable joint difference-thickness amount.
An eighth invention to solve the above-mentioned problems is characterized by, in the mash seam welding apparatus according to the seventh invention, including a mechanism for independently tilting in a horizontal plane each of the respective axes of the electrode wheels with respect to the axis perpendicular to the welding line.
With this, the mash seam welding apparatus can be provided that can easily set properly an optimum tilt angle according to the thickness of each of the metal plates and covers a wide difference-thickness range of the thicknesses of the metal plates.
A ninth invention to solve the above-mentioned problems is characterized by, in the mash seam welding apparatus according to the seventh or eighth invention, including a pair of upper and lower pressure rollers for rolling a joint portion of the metal plates joined by the mash seam welding; wherein the pressure rollers are installed in such a manner that axes of the pressure rollers are tilted in a horizontal plane with respect to the axis perpendicular to the welding line of the joint portion.
With this, in the mash seam welding method according to the fifth invention, a manufacturing facility can be provided that can achieve the following. During both the mash seam welding by the electrode wheels and the rolling by the pressure rollers, the increased amount of thickness of the joint portion is reduced by the shear deformation in the direction perpendicular to the welding line. In the joint portion of the metal plates, the step can be smoothed and the step gradient can significantly be reduced. Consequently, the stress concentration factor can more reliably be reduced and a high degree of joint strength can be ensured.
A tenth invention to solve the above-mentioned problems is characterized by, in the mash seam welding apparatus according to the ninth invention, including a mechanism for independently tilting in a horizontal plane the respective axes of the pressure rollers with respect to the straight line perpendicular to the welding line.
With this, a joining apparatus can be provided that can easily set properly an optimum tilt angle and covers a wide difference-thickness range of the thicknesses of the metal plates.
According to the present invention, when the metal plates are joined to each other by the mash seam welding method, the respective axes of the pair of upper and lower electrode wheels are tilted and the two metal plates are joined to each other while the electrode wheels are positively driven. Therefore, the increased amount of thickness of the joint portion can significantly be reduced by the shear deformation in the direction perpendicular to the welding line and the step gradient can significantly be reduced. Consequently, the stress concentration factor can be reduced and a high degree of joint strength can be ensured.
According to the present invention, if the two metal plates have different thicknesses, the tilt angles of the axes of the electrode wheels are adjusted according to the thicknesses of the metal plates. Therefore, the nugget can be formed at the joint interface, which improves the joint strength and increases the allowable joint difference-thickness amount to improve the flexibility of operation. Additionally, the above can be achieved with a relatively simple and inexpensive configuration in which only the pair of electrode wheels are tilted and positively driven.
According to the present invention, the step gradient of the joint portion of the metal plates is reduced and the step defined at the joint portion is smoothed. Therefore, the stress concentration factor of the joint portion can be reduced and a high degree of joint strength can be ensured. This produces the following effects as described below: the application range of the mash seam welding is enlarged; the work roll on a steel plate work line can be prevented from being scratched; and productivity and yield are increased.
More specifically, the present invention can reduce the step gradient of the joint portion subjected to the mash seam welding and smooth the step defined at the joint portion, which can reduce the stress concentration factor and a high degree of joint strength can be ensured. Therefore, in a cold rolling process for the steel product plant, a work roll can be prevented from being scratched during the cold rolling as the next process and anti-tension performance can be improved. Thus, the mash seam welding can be applied to the cold rolling process to which it has not heretofore been applied.
Also in tailored blanks, it has been avoided to apply the mash seam welding to a portion that requires fatigue strength due to stress concentration on the step defined at the joint portion. However, the step gradient is reduced and the steps are smoothed, which alleviates stress concentration to improve press formability. Thus, an expensive laser beam welder can be replaced with the inexpensive mash seam welder.
In a production line such as a continuous annealing line, galvanizing line or the like, the contact angle (stress concentration factor) between the work rolls of a skin pass rolling mill and the joint portion can be reduced. Consequently, the contact surface pressure between the work roll and the material can be reduced. It is possible, therefore, to prevent the scratching of the work roll and the mark transfer of the joint portion without lowering a line speed. Thus, productivity and yield can be improved.
Further, according to the present invention, the respective axes of the electrode wheels are tilted in the directions opposite to each other in the horizontal plain. Therefore, during the joint by the electrode wheels, the shearing force applied to the joint portion cancels the force transmitted to the clamp devices. This can prevent the buckling of the metal plate portion between the clamp device and the joint portion during the joint of the metal plates having a smaller thickness. Consequently, a relatively wide space can be ensured between the clamp device and the joint portion, which can alleviate restriction on the arrangement of the electrode wheels, pressure rollers and their related installations.
Embodiments of the present invention will hereinafter be described with reference to the drawings. A metal plate of the embodiments is described taking a cold rolling for steel product plant as an example.
Referring to
The carriage frame 9 is provided with support rollers 54 on its bottom portion. In addition, the carriage frame 9 can be shifted on a base plate 55 via the support rollers 54 in a direction (welding direction) perpendicular to two metal plates 5, 6 to be joined to each other. The entry side clamp device 7 includes a pair of upper and lower clamp members 7a, 7b, upper and lower pressing cylinder devices 7c, 7d, and a support frame 7e. The clamp members 7a and 7b are supported by the upper and lower pressing cylinder devices 7c and 7d, respectively, in the support frame 7e. The delivery side clamp device 8 includes a pair of upper and lower clamp members 8a, 8b, upper and lower pressing cylinder devices 8c, 8d, and a support frame 8e. The clamp members 8a and 8b are supported by the upper and lower pressing cylinder devices 8c and 8d, respectively, in the support frame 8e. The support frames 7e, 8e are supported on the base plate 55.
The mash seam welding apparatus includes a pair of upper and lower electric motors 61, 62 for drivingly rotating the corresponding electrode wheels. The pair of upper and lower electric motors 61, 62 is mounted on the corresponding lateral surfaces of the electrode wheel pressing device 10 and of the mounting block 51. The electric motors 61, 62 are connected to the corresponding rotating shafts of the electrode wheels 1, 2 via e.g. corresponding chain and sprocket mechanisms 67. Thus, the rotative power of the electric motors 61, 62 is transmitted to the corresponding electrode wheels 1, 2.
The electrode wheel pressing device 10 is provided with a tilting mechanism 27 (
Referring to
When the metal plates 5, 6 are to be joined to each other, the respective end portions of the metal plates 5, 6 are placed to overlap each other. In this state, the metal plates 5, 6 are gripped and positionally fixed by the corresponding clamp members 7a, 7b; 8a, 8b of the entry side and delivery side clamp devices 7, 8. Then, the carriage frame 9 is shifted in the welding direction by a drive device such as a cylinder device 57 or the like installed on the base plate 55. This relatively shifts the pair of upper and lower electrode wheels 1, 2 and the pair of upper and lower pressure rollers 3, 4 supported by the carriage frame 9 with respect to the metal plates 5, 6. In this way, joining and pressurizing are continuously performed. In this case, the overlapping portions L of the metal plates 5, 6 are gripped by the pair of upper and lower electrode wheels 1, 2, and the electrode wheels 1, 2 are pressed against the overlapping portions L of the metal plates 5, 6 by the electrode wheel pressing device 10. While the electrode wheels 1, 2 are positively drivingly rotated by the respective electric motors 61, 62, a welding current is allowed to flow into the electrode wheels 1, 2 to generate resistance heat. Thus, welding (mash seam welding) is performed. Then, the overlapping portions L are welded by the electrode wheels 1, 2. Immediately thereafter, the joint portion (the welded portion) J of the metal plates 5, 6 is gripped by the pair of upper and lower pressure rollers 3, 4, and then the pressure rollers 3, 4 are pressed against the joint portion J by the pressure roller pressing device 11 to thereby roll the joint portion J of the metal plates 5, 6.
Referring to
In the present embodiment as described above, the pair of upper and lower electrode wheels 1, 2 is arranged in such a manner that their axes 17, 18 are tilted in the horizontal plane in the respective directions opposite to each other with respect to a straight line (a straight line in a direction perpendicular to the welding line) perpendicular to the welding line of the overlapping portion L. The mash seam welding is performed while the electrode wheels 1, 2 are positively driven by the respective electric motors 61, 62.
In this way, a shearing force 14 is applied to the overlapping portions L in the direction of the straight line Y perpendicular to the welding line (the joint line) X, i.e., in the direction perpendicular to the welding line, as well as in the rolling direction (the travelling direction of the electrode wheels 1, 2 and the pressure rollers 3, 4). Shear deformation by this shearing force 14 promotes the plastic flow in the direction perpendicular to the welding line. This significantly reduces the thickness of the joint portion (the increased amount of thickness of the joint portion). Consequently, immediately thereafter, the joint portion J is rolled out by the pressure rollers 3, 4 to further reduce the increased amount of thickness of the joint portion J to a thickness corresponding to the thickness of the base material, i.e., of the metal plates, which can significantly reduce the step-gradient. Because of the reduced step-gradient, a stress concentration factor is reduced, thereby ensuring a high degree of joint strength.
The operation in which the plastic flow (metal flow) in the direction perpendicular to the welding line is promoted by tilting the respective axes 17, 18 of the pair of upper and lower electrode wheels 1, 2 is described in detail by use of
Referring to
As described above, the pair of electrode wheels 1, 2 is positively driven by the respective electric motors 61, 62 with the respective axes 17, 18 of the electrode wheels 1, 2 tilted with respect to the straight line Y perpendicular to the welding line X. At the same time, the overlapping portions L are welded while being pressed. The shearing force 14 is applied to the overlapping portions L in the direction perpendicular to the welding line. Thus, the thickness of the joint portion of the overlapping portions L is reduced. The shearing force 14 depends on the deformation resistance of the material; therefore, the higher the deformation resistance is, the more a thrust force 13 applied to the electrode wheels 1, 2 from the corresponding metal plates 5, 6 is increased. If the thrust force 13 is increased as described above, there arise problems in that the electrode wheels 1, 2 and their bearings are reduced in operating life and the entire device is enlarged because of setting a holding force for the thrust force 13.
In the present embodiment, the thrust force 13 due to the tilt of the respective axes 17, 18 of the electrode wheels 1, 2 described above occurs during the heating welding (mash seam welding) of the overlapping portions L. During the mash seam welding, the temperature in the vicinity of the joint portion rises up to approximately 1000° C. to 1400° C. although depending on the thickness of the metal plates. Thus, it is presumed that the temperature of the joint portion J rises up to a level higher than such temperatures. In contrast, if the deformation resistance of the metal plates 5, 6 depends on the material temperature and the temperature of the joint portion J is approximately 1000° C. to 1400° C., the deformation resistance is extremely low (see
The direction of the tilt angle α of the pair of upper and lower electrode wheels 1, 2 can be set in two ways.
A first setting method is as below. As illustrated in
Referring to
The present embodiment employs the second setting method. The reason is as follows.
In general, the material of the electrode wheels 1, 2 is applied with a copper-based material with high electric conductivity. The copper-based material has a problem of being inferior in material strength to the joining material. The respective axes 17, 18 of the pair of electrode wheels 1, 2 may be tilted so that the respective traveling-directional portions 1A, 2A of the electrode wheels 1, 2 face in the horizontal plane toward the corresponding directions opposite to the extending directions of the metal plates with which the electrode wheels 1, 2 first come into contact. In addition, the shearing force 14 may be applied to the metal plates 5, 6 from the respective electrode wheels 1, 2 in the direction from the respective end portions 5A, 6A of the metal plates 5, 6 to the respective extending directions of the metal plates 5, 6. In such a case, the electrode wheels 1, 2 travel in the direction in which the electrode wheel surfaces bite into the corresponding corners of the end portions 5A, 6A of the metal plates 5, 6, along with the progress of the welding. This poses a new problem in that the electrode wheel surfaces are scratched by the corners of the joining material. In such a case, current density locally concentrates between the electrode wheels 1, 2 and the material, which causes spattering and significantly reduces the operating life of the electrode wheel.
In contrast to this, the respective axes 17, 18 of the pair of electrode wheels 1, 2 may be tilted so that the respective traveling-directional portions 1A, 2A of the electrode wheels 1, 2 face in the horizontal plane toward the corresponding extending directions of the metal plates with which the electrode wheels 1, 2 first come into contact. In addition, the upper shearing force 14 may be applied to the metal plates 5, 6 from the respective electrode wheels 1, 2 in the direction from the respective extending sides of the metal plates 5, 6 to the respective end portions 5A, 6A thereof. In such a case, it is possible to prevent the electrode wheels 1, 2 from being scratched due to biting into the corners of the end portions 1A, 2A of the metal plates 1, 2 and to apply the shearing stress toward the metal plates 5, 6.
The tilt angle α of the axes 17, 18 of the electrode wheels 1, 2 is set according to the thicknesses of the metal plates 5, 6. Qualitatively, the tilt angle α is set to a small value if the thicknesses of the metal plates are small; the tilt angle α is set to a larger value as the thicknesses of the metal plates become larger. As illustrated in
In mash seam welding, as illustrated in
In the present invention, as illustrated in
The tilt angles α1, α2 are set according to the thickness-difference amount so as to apply the shear deformation necessary to reduce thickness-difference. With this setting, the nugget N can be formed on the joint interface. The thickness-difference ratio can be increased without lowering the joint strength. The increased amount of thickness of the overlapping joint portion J can be reduced to reduce the restriction in terms of operation. Joint quality encountered when the metal plates having different thicknesses are joined to each other can be enhanced.
Conventional mash seam welding has heretofore been performed while the electrode wheels 1, 2 roll the overlapping portions from their end portions. In such a case, as illustrated in
The tilt angles of the axes of the electrode wheels 1, 2 may be fixed. However, it is preferred that the tilt angles be variable to any angle.
Referring to
Additionally, the tilting mechanism 27 is provided with an angle sensor 86 for detecting the tilt angle of the upper electrode wheel 1. Before the start of joining, the tilt angle controller 85 obtains angle information corresponding to the thicknesses of the metal plates 5, 6 from the upper controller 71 and sets the tilt angle. In addition, the tilt angle controller 85 controls the drive of the electric motor 84 by use of the signal of the angle sensor 86 to allow the tilt angle of the electrode wheel 1 to agree with the setting angle. In this case, a control model is previously constructed with respect to the relationship between the respective thicknesses of the metal plates 5, 6 and the corresponding electrode wheels 1, 2. The upper controller 71 assembles a database based on the control model and gives an angle to be set to the tilt angle controller 85 as needed. In this way, an optimum tilt angle can easily be set as needed in accordance with the respective thicknesses of the metal plates 5, 6. An allowable difference-thickness ratio of joint materials can be increased. In addition, the nugget N of the difference-thickness joint portion can surely be formed at the center of the joint interface. Therefore, a high-quality joint portion can be realized with an inexpensive device configuration. The angle sensor 86 may be a sensor that detects the rotational angle of the rotating shaft 81 as shown in the figure and may be an encoder detecting the rotational angle of the electric motor 84.
Alternatively, the respective thicknesses of the metal plates 5, 6 are measured by a detecting means such as e.g. the laser distance meter 75 mentioned earlier or the like before the welding by the electrode wheels 1, 2. An angle to be set is given to the tilt angle controller 85 on the basis of the setting information of the database from the measured thicknesses. Thus, the tilt angle is controlled on a real-time basis.
In cold rolling for steel production and press forming including tailored blanks, high stress is applied to the joint portion in the work process after the joining. Specifically, if steps S exist at a joint portion J between the metal plates 5, 6 as illustrated in
In a skin pass rolling step for example, a joint portion joined in a joint step which is a step anterior to rolling has been rolled by a skin pass rolling mill in the past. In such a case, as illustrated in
The present embodiment described above produces the following effects.
1. The pair of electrode wheels 1, 2 is positively driven by the corresponding electric motors 61, 62 with the respective axes 17, 18 of the pair of upper and lower electrode wheels 1, 2 tilted to thereby join metal plates 5, 6. Therefore, the shearing force in the direction perpendicular to the welding line X is applied to the overlapping portions L of the two metal plates 5, 6. This applies the shear deformation in the same direction to the overlapping portions L. The plastic flow in the direction perpendicular to the welding line X occurs in addition to the plastic flow in the direction of the welding line resulting from the conventional rolling of the electrode wheels. The plastic flow in the direction perpendicular to the welding line X significantly reduces the increased amount of thickness of the overlapping portions (the joint portion) J after the joining. Consequently, the joint portion J is rolled by the pressure rollers 3, 4 immediately thereafter to further reduce the increased amount of thickness of the joint portion to a level corresponding to the base material thickness of the metal plates. Thus, the step gradient can be significantly reduced. Since the step gradient is reduced, the stress concentration factor can be reduced to ensure a high degree of joint strength.
If the two metal plates 5, 6 are different in thickness from each other, the tilt angles of the axes of the electrode wheels 1, 2 are adjusted according to the thicknesses of the metal plates 5, 6. This adjusts the reduced amount of thickness of each of the metal plates at the overlapping portions L. Therefore, the metal plates 5, 6 are joined to each other so that the nugget N may not deviate from the joint interface. Thus, the formation of the nugget N on the joint interface in addition to the reduction in stress concentration factor due to the reduction in step gradient can dramatically improve the joint strength of the joint portion. An allowable joint difference-thickness amount can be increased to improve the flexibility of the operation. Additionally, because of only the configuration in which the pair of electrode wheels 1, 2 are positively driven with the axes thereof tilted, the mash seam welding apparatus can be realized with the relatively simple and inexpensive configuration.
The joint portion J of the metal plates 5, 6 is rolled to a level corresponding to the base material thickness of the metal plates to significantly reduce the step gradient. This can reduce the stress concentration factor of the joint portion, which ensures a high degree of joint strength. Thus, the following effects can be provided. The mash seam welding can widely be applied to a cold rolling process and tailored blanks to which the mash seam welding have not heretofore been applied. The work roll on the steel plate work line can be prevented from being scratched. Productivity and yield can be improved.
That is, in the present embodiment, the step gradient of the joint portion subjected to the mash seam welding is reduced to reduce the stress concentration factor of the joint portion, which can ensure a high degree of joint strength. Therefore, in the cold rolling process for steel product line, it is possible to prevent the work roll from being scratched during the cold rolling as the next step and to improve anti-tension performance. Thus, the mash seam welding can be applied to the cold rolling process to which it has not heretofore been applied.
Also in tailored blanks, because of stress concentration on the step defined at the joint portion, the application of the mash seam welding to a portion requiring fatigue strength has been avoided. However, because of the reduced step gradient, the stress concentration is alleviated and press forming performance is improved. Therefore, an expensive laser beam welder can be replaced with the inexpensive mash seam welder.
In a continuous annealing line, and a production line including galvanizing line or the like, the contact angle (stress concentration factor) between the work rolls of a skin pass rolling mill and the joint portion can be reduced. Consequently, the contact surface pressure between the work roll and the material can be reduced. It is possible, therefore, to prevent the scratching of the work roll and the mark transfer of the joint portion without lowering a line speed. Thus, productivity and yield can be improved.
2. The two metal plates 5, 6 are joined to each other while the respective axes 17, 18 of the pair of electrode wheels 1, 2 are each tilted with respect to the straight line perpendicular to the welding line X so that the respective traveling-directional portions 1A, 2A of the pair of electrode wheels 1, 2 face in the horizontal plane toward the corresponding extending directions of the metal plates with which the electrode wheels 1, 2 first come into contact. Therefore, when the electrode wheels 1, 2 travel on the overlapping portions L along with the progress of the welding, it is possible to prevent the end portions 5A, 6A of the metal plates 5, 6 at the overlapping portion L from biting into the corresponding electrode wheels 1, 2 to scratch the electrode wheels 1, 2. As a result, it is possible to prevent the occurrence of spattering during the welding due to such scratches.
3. If the two metal plates 5, 6 are different in thickness from each other, the tilt angle of the axis of the electrode wheel on the side where one of the metal plates 1, 2 has a larger thickness is made greater than that on the side where the other of the metal plates 1, 2 has a smaller thickness. Therefore, the reduced amount of thickness of the metal plate having a larger thickness can be increased to substantially agree with that of the metal plate having a smaller thickness. Thus, the nugget N can be formed on the joint interface, which can increase joint strength and increase an allowable joint difference-thickness amount.
4. At least one of the processes before the start of welding of the overlapping portions L and after the completion of the welding of the overlapping portions L selects the first setting or the second setting. In the first setting the pair of electrode wheels 1, 2 is brought into contact with each other. In the second setting the pair of electrode wheels 1, 2 is not brought into contact with each other or the electrode wheels 1, 2 are brought into contact with each other at a light load compared with the pressing force during the welding. In the first setting the pair of electrode wheels 1, 2 is made non-driven but in the second setting it made driven. Therefore, it is possible to prevent the excessive thrust force from being applied to the upper and lower electrode wheels 1, 2. Thus, the operating lives of the upper and lower electrode wheel can be elongated. Further, the wear of the upper and lower electrode wheels 1, 2 can be suppressed to reduce running cost.
5. The pair of electrode wheels 1, 2 is installed in such a manner that their axes 17, 18 are tilted in the horizontal plane in the respective directions opposite to each other with respect to the axis Y perpendicular to the welding line X defined in the overlapping portions L of the two metal plates 5, 6. Therefore, the step gradient of the joint portion of the two metal plates can be reduced as described above so that the high degree of joint strength can be ensured. In addition, the nugget N formed by the mash seam welding is formed at the joint interface with a relatively simple and inexpensive configuration to improve the joint strength. Thus, manufacturing installations that increase the allowable joint difference-thickness amount can be provided.
6. The mechanism 27 is installed which independently tilts in the horizontal plane the respective axes 17, 18 of the pair of electrode wheels 1, 2 with respect to the axis Y perpendicular to the welding line X. Therefore, the optimum tilt angle can easily be set properly according to the thicknesses of the metal plates 1, 2. In addition, the mash seam welder can be provided which has the wide difference-thickness range of the thicknesses of the metal plates 1, 2.
Another embodiment of the present invention will be described with reference to
In the embodiment described above, as in the past the pair of upper and lower pressure rollers 3, 4 is pressure rollers that can be rotated around the respective axes parallel to each other. In addition, the joint portion after the mash seam welding is rolled by the pressure rollers 3, 4. Although the joint portion is even rolled as mentioned above, the following effects as described above can be produced by the mash seam welding being performed with the respective axes 17, 18 of the pair of upper and lower electrode wheels 1, 2 tilted. The reduced thickness effect of the welded portion (the joint portion) subjected to the mash seam welding is large. The step gradient of the joint portion J between the metal plates 5, 6 can significantly be reduced to reduce the stress concentration factor of the joint portion, thereby ensuring a high degree of joint strength. In the present embodiment, the joint portion is rolled by the pair of upper and lower pressure rollers with their axes tilted in addition to the pair of upper and lower electrode wheels. In this way, the joint portion is surely rolled to a level corresponding to the base material thickness of the metal plates, which makes it possible to smooth steps.
Referring to
In the present embodiment, the pair of upper and lower electrode wheels 1, 2 is installed as described in the above-embodiment in such a manner that their axes 17, 18 are tilted in the horizontal plane in the respective directions opposite to each other with respect to the straight line perpendicular to the welding line of the overlapping portions L of the two metal plates 5, 6. The mash seam welding is performed while positively driving the electrode wheels 1, 2 by the corresponding electric motors 61, 62. As illustrated in
The respective axes 17, 18 of the pair of upper and lower electrode wheels, 1, 2 and the respective axes 15, 16 of the pair of upper and lower pressure rollers 3, 4 are tilted as described above. Because of this, both the mash seam welding by the electrode wheels 1, 2 and the rolling by the pressure rollers 3, 4 provide thickness-reducing action promoting the plastic flow in the direction perpendicular to the welding line. Thus, the steps S of the joint portion J can surely be rolled to a level corresponding to the base material thickness so as to be smoothed.
In the joining by conventional electrode wheels 1, 2 whose axes are not tilted, the plastic flow in the direction perpendicular to the welding line is limited by clamp devices. In this case, force transmitted from the joint portion to the grip portions of the clamp devices occurs. Therefore, if metal plates having small thicknesses are jointed to each other, there is a possibility that buckling occurs at the joint portion and at the metal material portion of the grip portion. In order to prevent the buckling, the clamp device needs only to be disposed extremely close to the joint portion. In such a case, a space between the clamp device and the joint portion is narrowed, which poses a problem as below. The arrangement of the electrode wheels, the pressure rollers, and their related installations is restricted. This impairs the flexibility of installation arrangement.
In the present embodiment, the respective axes 17, 18 of the electrode wheels 1, 2 are tilted in the directions opposite to each other in the horizontal plane. Therefore, during the joining by the electrode wheels 1, 2, the shearing force 14 applied to the joint portion J cancels the forces transmitted to the clamp devices 7, 8. Therefore, even if the clamp devices 7, 8 are not disposed immediately close to the joint portion J, it is possible to prevent the buckling of the metal plate during the joint of the metal plates having a smaller thickness. Consequently, a relatively wide space can be ensured between the clamp devices 7, 8 and the joint portion J. Thus, it is possible to alleviate the restriction on the arrangement of the electrode wheels 1, 2, the pressure rollers 3, 4 and their related installations (e.g. electric motors 61 to 64, chain and sprocket mechanisms 67, 68, tilting devices, etc.).
The details of the action in which the plastic flow in the direction perpendicular to the welding line is promoted by tilting the respective axes 15, 16 of the pair of upper and lower pressure rollers 3, 4 are the same as those in the case of the electrode wheels 1, 2 described with
The respective directions of the tilt angles α of the pair of upper and lower pressure rollers 3, 4 can be set in two ways similarly to the case of the electrode wheels 1, 2.
The first setting method is as below. As illustrated in
The second setting method is such that the pressure rollers 3, 4 are tilted reversely to those of the first setting method as illustrated in
The present embodiment employs the first setting method. The reason is as below.
Even if the pair of upper and lower pressure rollers 3, 4 is tilted by the second setting method, the steps S are subjected to plastic flow due to the shearing force 14 so that they can be smoothed. However, this case poses another problem as below. As illustrated in
The tilt angle (corresponding to the tilt angle α in
As described above, the axes 15, 16 of the pair of pressure rollers 3, 4 are each tilted with respect to the straight line Y perpendicular to the welding line X. The pair of pressure rollers 3, 4 are positively driven by the corresponding electric motors 63, 64 to thereby roll the steps S of the joint portion J. In this way, the shearing force in the direction perpendicular to the welding line is applied to the joint portion J to smooth the steps S. The shearing force depends on the deformation resistance of material. Therefore, the higher the deformation resistance is, the more the thrust force 13 applied to the pressure rollers 3, 4 from the metal plates 5, 6 is increased. If the thrust force 13 is increased as described above, the operating lives of the pressure rollers 3, 4 and of the bearings thereof are shortened and the holding force for the thrust force 13 is set, which poses a problem in that the entire apparatus is enlarged.
In the present embodiment, the pair of upper and lower pressure rollers 3, 4 is disposed adjacently to the pair of upper and lower electrode wheels 1, 2 in the carriage frame 9. The joining and pressing are continuously performed by moving the carriage frame 9 in the welding direction. Although depending on the thickness of the metal plates 5, 6, the temperature in the vicinity of the joint portion rises up to approximately 1000° C. to 1400° C. immediately after the joint portion is passed between the electrode wheels. Thus, it is presumed that the temperature of the joint portion J rises up to a level higher than such temperatures. Since the joining and pressing are continuously performed, the temperature of the joint portion J during the pressing by the pressure rollers 3, 4 can easily be increased to approximately 300° C. or higher or 500° C. or higher by use of the residual heat of the joint portion J produced by the welding. Thus, the installation can be downsized.
The upper and lower pressure rollers 3, 4 having the respective tilted axes 15, 16 can be allowed to have the same setting as in the case of the electrode wheels described with
Also the present embodiment can employ the same control system as that of the previous embodiment described with
The same tilting device as in the case of the electrode wheels described with
Incidentally, in the embodiment described above, the electrode wheel pressing device 10 having the tilting mechanism 27 and the pressure roller pressing device 11 having the tilting mechanism 27 are disposed in one and the same carriage frame 9. However, even if they are disposed in corresponding separate frames, the function of the present invention will not be impaired.
The embodiment described above can produce the following effects in addition to the effects 1 to 6 in the previous embodiment.
1-A. The pair of pressure rollers 3, 4 is positively driven by the corresponding electric motors 63, 64 with the respective axes 15, 16 of the pair of upper and lower pressure rollers 3, 4 tilted to thereby roll the metal plates 5, 6, similarly to the case where the respective axes 17, 18 of the pair of upper and lower electrode wheels 1, 2 are tilted, the shearing force in the direction perpendicular to the welding line X is applied to the joint portion J. This applies the shear deformation to the joint portion J. The plastic flow in the direction perpendicular to the welding line X significantly reduces the increased amount of thickness of the joint portion. Consequently, during both the mash seam welding by the electrode wheels 1, 2 and the rolling by the pressure rollers 3, 4, the shear deformation in the direction perpendicular to the welding line X reduces the increased amount of thickness of the joint portion J. In the case where the metal plates having the same thickness are joined to each other, the joint portion J can surely be rolled to a level corresponding to the base material thickness of the metal plates and the steps can be smoothed. At the joint portion of the metal plates having different thicknesses, the steps can be smoothed or the step gradient can significantly be reduced. As a result, the stress concentration factor can be reduced more surely to ensure a high degree of joint strength compared with the case where only the respective axes of the electrode wheels 1, 2 are tilted.
The step gradient of the joint portion J of the metal plates 5, 6 is reduced or the steps S of the joint portion J are smoothed. This can reduce the stress concentration factor of the joint portion, which can ensure a high degree of joint strength. Thus, the following effects can be more ensured. The mash seam welding can widely be applied to a cold rolling process and tailored blanks to which the mash seam welding has not heretofore been applied. The work roll on the steel product line can be prevented from being scratched. Productivity and yield can be improved.
1-B. The respective axes 15, 16 of the pair of upper and lower pressure rollers 3, 4 are tilted in the directions opposite to each other in the horizontal plane. During the rolling by the pressure rollers 3, 4, the shearing force 14 is applied to the upper surface side and lower surface side of the joint portion J in opposite directions. The upper and lower forces transmitted to the clamp devices 7, 8 cancel each other. Thus, it is possible to prevent the buckling of the metal plate during the joint of the thin metal plates without disposing the clamp devices 7, 8 immediately close to the joint portion J. As a result, a relatively wide space can be ensured between the clamp devices 7, 8 and joint portion J, which can alleviate restriction on the arrangement of the electrode wheels 1, 2, the pressure rollers 3, 4 and their related installations (e.g., the electric motors 61 to 64, the chain and sprocket mechanisms 67, 68, the tiling mechanisms 27, etc.).
2. The respective axes 15, 16 of the pair of pressure rollers 3, 4 are each tilted with respect to the straight line Y perpendicular to the welding line X so that the respective traveling-directional portions 3A, 4A of the pair of pressure rollers 3, 4 face in the horizontal plane toward the corresponding directions opposite to the extending direction of the metal plate 5 concerning the metal material with which the pressure rollers 3, 4 first come into contact. In addition, the joint portion is rolled while applying the shearing force from the steps S of the joint portion J of the metal plates 5, 6 in the extending direction of the metal plate 5 concerning the metal material with which the pressure rollers 3, 4 first come into contact. Therefore, it is possible to prevent the step portion from being interfolded into the base material of the metal plates 5, 6. This can prevent crack-like defects (non-welded defects) from occurring when the step portion is interfolded into the base material.
3. The pair of pressure rollers 3, 4 is further provided which rolls the joint portion J of the two metal plates 5, 6 having been joined by the mash seam welding. In addition, the pressure rollers 3, 4 are installed in such a manner that their axes 15, 16 are tilted in the horizontal plane with respect to the straight line Y perpendicular to the welding line X. Therefore, the step gradient of the joint portion of the two metal plates 5, 6 can be reduced so that the high degree of joint strength can be ensured. In addition, the nugget N formed by the mash seam welding is formed at the joint interface with a relatively simple and inexpensive configuration to increase the joint strength. Thus, manufacturing installations that increase the allowable joint difference-thickness amount can be provided.
4. The mechanisms are provided which independently tilt in the horizontal plane the respective axes 15, 16 of the pair of pressure rollers 3, 4 with respect to the straight line Y perpendicular to the welding line X. Therefore, the joining apparatus can be provided which can easily set the optimum tilt angle properly according to the step amount and has the wide difference-thickness range of the thicknesses of the metal plates.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2008/062633 | 7/11/2008 | WO | 00 | 2/8/2011 |
