Patent Application
20160320128
The present invention relates to a steel sheet heating method and a steel sheet heating apparatus for heating a steel sheet.
Hot press molding, which is increasingly employed as, for example, a method for molding a steel sheet such as the material of an automobile component using a high-tensile steel sheet, can mold a steel sheet in a stage of low deformation resistance by molding it at high temperature, and furthermore can provide a component etc. with high strength and high shape accuracy by press molding without causing molding defects such as deformation after molding, by hardening by quenching based on rapid cooling using the jetting of cooling water.
In such a hot press molding method, press molding is performed such that a steel sheet is heated at a prescribed temperature, for example 700° C. to 1000° C., in a heating furnace before press molding and then the steel sheet is conveyed to a hot press molding apparatus.
As the technology of heating thus using a heating furnace, conventionally, a mechanism in which a steel sheet is heated by heaters provided in, for example, an upper portion and a lower portion of the interior of a furnace while the steel sheet is horizontally supported by rollers and conveyed by the rollers in the furnace has commonly been used (Patent Literature 1).
Patent Literature 1: JP 2009-155691A
However, in the conventional technology mentioned above, since a steel sheet is conveyed by rolling rollers, the steel sheet may meander in the furnace. Furthermore, the rollers constitute a shield, and the radiation efficiency is poor and rapid heating is difficult. In addition, it is necessary to roll the rollers constantly even at times other than conveyance in order to soak the rollers so that they are not thermally deformed, and the energy efficiency is poor. Moreover, due to the thermal shock near the entrance of the furnace and the thermal stress produced by the unevenness of heating, there has been a concern that the roller will be degraded or damaged. If the roller is damaged, the operation of the furnace stops. Furthermore, for a surface-plated steel sheet, there have been concerns that the plating material will adhere to the roller in the melting temperature range and further the plating material adhering to the roller will adhere to the steel sheet again.
The present invention is made in view of these points, and an object of the present invention is to solve the issues mentioned above by a manner in which a steel sheet is brought into a furnace and is heated in a state of being fixedly supported in the vertical direction, instead of the conventional manner in which a steel sheet is conveyed in a furnace while being horizontally supported by rollers.
In order to achieve the above object, the present invention provides a steel sheet heating method that heats a steel sheet to be pressed before hot press molding, the steel sheet heating method including: bringing the steel sheet into a heating furnace including a heater on an inside surface of the heating furnace in a state where the steel sheet is supported in a vertical direction while an unnecessary portion of the steel sheet that becomes unnecessary after molding is fixedly supported by a support member; and performing heating at a prescribed temperature in the heating furnace, then taking the steel sheet out of the heating furnace, and after that removing the unnecessary portion.
The “after that” herein is not limited to the time immediately after being taken out of the heating furnace, and may be the time of performing hot press molding after the taking-out.
Examples of the “fixed support” in the present invention include holding the unnecessary portion mentioned above with a clamp and hanging the unnecessary portion by locking it with the support member. It is preferable that the steel sheet be fixedly supported at two or more places. This is because the steel sheet can thereby be prevented from bending when the steel sheet has a long-length shape, for example. When the steel sheet has a long length, for example when the length in the longitudinal direction of the steel sheet is more than 1 m, the steel sheet is preferably fixedly supported at both ends thereof.
According to the present invention, since a steel sheet is heated in the heating furnace in a state of being fixedly supported in the vertical direction by the support member, there is no harmful effect like conventional ones occurring in relation to the use of rollers, and the radiation efficiency is good and also the energy efficiency is good. Furthermore, by the fixed support in the vertical direction by means of the support member, the bending of the steel sheet can be suppressed. Here, the unnecessary portion that becomes unnecessary after molding refers to a portion that becomes unnecessary as a product after the steel sheet is molded. The “fixedly supporting the unnecessary portion by means of the support member” refers to fixedly supporting the whole or part of the unnecessary portion by means of the support member.
In the method, the steel sheet may be moved in a vertical direction in the heating furnace.
Furthermore, tension may be applied to the steel sheet fixedly supported.
According to another aspect, the present invention provides a steel sheet heating apparatus that heats a steel sheet to be pressed before hot press molding, the steel sheet heating apparatus including: a heating furnace capable of accommodating the steel sheet in a vertical state; and a conveyance apparatus that allows the steel sheet to pass through a conveyance path of the heating furnace in a state of being supported in a vertical direction by a support member. The heating furnace includes the conveyance path of the steel sheet formed between side walls facing each other and a heater that is provided on at least one surface of the side walls and heats the steel sheet. The conveyance apparatus includes the support member that fixedly supports an unnecessary portion of the steel sheet that becomes unnecessary after molding and a moving mechanism that moves the support member along a rail provided from above an upstream side of an entrance to above a downstream side of an exit of the heating furnace.
In this case, a vertical drive mechanism that moves the support member in a vertical direction may be further included.
In addition, a shearing mechanism that shears the unnecessary portion on the downstream side of the exit of the heating furnace may be further included.
Furthermore, a mechanism that applies tension to the steel sheet fixedly supported may be further included.
According to the present invention, there is no harmful effect like conventional ones occurring in relation to the use of rollers when a steel sheet to be pressed is heated before hot press molding, and the radiation efficiency is good and also the energy efficiency is good. Furthermore, a steel sheet to be pressed can be heated more uniformly than in the past.
Hereinbelow, embodiments of the present invention are described.
As the heater 15, for example, an electric heater, a far-infrared heater, a near-infrared lamp, an induction heating means, or the like may be used. Although in the embodiment the heater 15 is provided individually on both surfaces of the side wall bodies 12 and 13, the heater 15 may be provided only on one side wall surface depending on the type, size, shape, etc. of the steel sheet.
A conveyance apparatus 20 of the steel sheet heating apparatus 1 according to the embodiment includes a forward rail housing 21 provided from above the entrance 10a side of the heating furnace 10 (the back side of the drawing) to above the exit 10b side of the heating furnace 10 (the front side of the drawing) and a backward rail housing 22 provided parallel to the forward rail housing 21. Each of the forward rail housing 21 and the backward rail housing 22 is supported by support columns 23. A support member moving path 24a and a support member moving path 24b in a curved line form in a planar view, which serve also as a horizontal rail, are stretched between the ends of the forward rail housing 21 and the backward rail housing 22.
The forward rail housing 21 and the backward rail housing 22 basically have the same configuration; a detailed description thereof is given as follows based on the forward rail housing 21 shown in
A support member 30 in the embodiment is supported directly by the rail body 21c. As shown in
The rail running member 33 includes an engaging unit 33a engaging with the chain conveyor 21b and a running unit 33c provided with rollers 33b capable of running the rail body 21c mentioned above. The cylinder 34 is fixed to the bracket 31 a, and a rod member 34a that extends and contracts by the operation of the cylinder 34 is suspended below the bracket 31a and has a support body 34b at its lower end. Therefore, the support body 34b moves vertically by the operation of the cylinder 34.
As shown in
In the example of the embodiment, the extension members Ka and Kb are in a T-shaped configuration, and the inside thereof is notched to form the locking portions 36; but instead, as shown in
Instead of thus supporting the steel sheet K by hanging the steel sheet K between the support bodies 34b and 34b of the hanging members 31 and 32 using the extension members Ka and Kb, for example, a clamping mechanism (not shown) that clamps the extension members Ka and Kb may be provided in the hanging members 31 and 32, and thus the extension members Ka and Kb may be clamped to fixedly support the steel sheet K in the vertical direction.
As shown by the broken line of
Referring to
In the embodiment, as described above, the support member moving path 24a and the support member moving path 24b are stretched between the ends of the forward rail housing 21 and the backward rail housing 22, and the hanging members 31 and 32 of the support member 30 that has been located on the backward rail housing 22 side can be moved to the forward rail housing 21 side, that is, to the entrance 10a side of the heating furnace 10, via the support member moving path 24b.
Furthermore, the hanging members 31 and 32 of the support member 30 that has been located on the forward rail housing 21 side, i.e. on the exit 10b side of the heating furnace 10, can be moved to the backward rail housing 22 side via the support member moving path 24a. For the hanging members 31 and 32 to be inserted into the furnace, heat-resistant steel or the like with high heat resistance and thermal shock properties is used; and the hanging members 31 and 32 may be protected with a heat insulating material, which should usually be considered as a means for protecting the furnace equipment, and may be provided with a flow path inside and use a cooling means based on a cooling medium such as cooling water or air.
In the embodiment, a shearing mechanism 40 that shears the extension members Ka and Kb of the steel sheet K that has undergone the heating by the heating furnace 10 and is located on the exit 10b side of the heating furnace 10 while being supported by the hanging members 31 and 32 of the support member 30 is provided on the exit 10b side of the heating furnace 10.
The shearing mechanism 40 includes a pair of shearing apparatuses 41 and 42. The shearing apparatuses 41 and 42 have the same structure; for example, a detailed description of the shearing apparatus 42 is given as follows: the shearing apparatus 42 includes a base 43 and shearing members 44 and 45 provided perpendicular to the base 43 and facing each other. The shearing members 44 and 45 move along the base 43 by means of a drive mechanism (not shown), and can come close to and go away from each other freely. Blades 44a and 45a are provided on the facing surface sides of the shearing members 44 and 45, respectively.
Therefore, by the shearing members 44 and 45 coming close together, by means of the blades 44a and 45a thereof, the extension members Ka and Kb of the steel sheet K supported between the hanging members 31 and 32 can be sheared.
A conveyance robot 50 including an articulated arm that holds the steel sheet K supported by the hanging members 31 and 32 of the support member 30 may be placed on the exit 10b side of the heating furnace 10. The conveyance robot 50 has the function of setting two clamp-type chucks 52 and 52 to ON or OFF by the rotational movement operation of a handle 51. The conveyance robot 50 includes a moving mechanism (not shown) that can move from the position on the exit 10b side of the heating furnace 10 freely, and can convey the held steel sheet to a hot press molding apparatus described later.
The steel sheet heating apparatus 1 according to the embodiment is configured in the above manner; next, a steel sheet heating method using the steel sheet heating apparatus 1 is described.
First, the steel sheet K to be molded by hot press molding is supported at the hanging members 31 and 32 of the support member 30 located on the forward rail housing 21 side, on the entrance 10a side of the heating furnace 10. Then, tension is applied to the supported steel sheet in the horizontal direction by the tension application mechanism 39 shown in
In this state, the drive mechanism of the forward rail housing 21 is put into operation to drive the chain conveyor 21b, and thereby the hanging members 31 and 32 of the support member 30 supporting the steel sheet K are moved to the heating furnace 10; and the steel sheet K is heated to a prescribed temperature, for example 700° C. to 1000° C., by the heaters 15 in the heating furnace 10. At this time, the cylinders 34 of the hanging members 31 and 32 may be put into operation to extend and contract the rod members 34a, and thus the steel sheet K supported at the hanging members 31 and 32 can be moved in the vertical direction.
After the steel sheet K is heated to the prescribed temperature, the chain conveyor 21 b of the forward rail housing 21 is driven, and thus the hanging members 31 and 32 of the support member 30 supporting the steel sheet K are taken out of the heating furnace 10 and are moved to the space on the exit 10b side of the heating furnace 10. The steel sheet K may be heated in the heating furnace 10 while being conveyed constantly, or may be heated in a state of being stationary in the heating furnace 10.
After the hanging members 31 and 32 of the support member 30 supporting the steel sheet K have stopped in a prescribed position in the space on the exit 10b side of the heating furnace 10, the conveyance robot 50 is brought close to the steel sheet K, and the steel sheet K is held by the chucks 52 and 52. After that, the tension applied to the steel sheet K the tension application mechanism 39 is released; and the shearing apparatuses 41 and 42 are put into operation, and the extension members Ka and Kb of the steel sheet K supported between the hanging members 31 and 32 are sheared by the shearing members 44 and 45. Thus, the conveyance robot 50 enters a state of supporting the steel sheet K from which the extension members Ka and Kb, which are unnecessary portions after molding, have been removed.
After that, as shown in
Thus, by the embodiment of the present invention, the steel sheet K is brought into and heated by the heating furnace 10 including the heaters 15 on the surfaces of the side wall bodies 12 and 13 in a state where the steel sheet K is fixedly supported in the vertical direction via the extension members Ka and Kb, which are unnecessary portions that become unnecessary after press molding, by the hanging members 31 and 32 of the support member 30; therefore, as compared with a conventional system in which a steel sheet is heated while being supported in a horizontal state by rollers, firstly, the steel sheet K can be heated more uniformly than in the past without the steel sheet K meandering. Furthermore, since there is no shield between the heater 15 and the steel sheet K, the heat from the heater 15 can be given to the steel sheet K with good efficiency, and the radiation efficiency is good and more rapid heating than in the past is possible. In addition, since at times other than heating there is no need to put the support member 30 in movement, the energy efficiency is better than in the past. In addition, since rollers are not used, there is no possibility of shutdown due to damage to rollers.
Furthermore, in the embodiment described above, since the support body 34b supporting the steel sheet K can be moved vertically by putting the cylinder 34 of the support member 30 into operation, the heating unevenness can be suppressed by putting the cylinder 34 into operation to move the steel sheet K in the vertical direction while the steel sheet K is located in the heating furnace 10, and thereby more uniform heating can be made. Therefore, also heating unevenness in the vertical direction due to the arrangement of heaters 15 and the variation in heating output characteristics can be prevented.
Furthermore, in the embodiment described above, since the steel sheet K to be heated is fixedly supported in the vertical direction via the extension members Ka and Kb by the hanging members 31 and 32 of the support member 30 and, in particular, is fixedly supported at two places of both ends, the steel sheet K does not bend even when the steel sheet K has a shape long in the horizontal direction. Furthermore, since tension is applied to the steel sheet K to be heated in the horizontal direction by the tension application mechanism 39, the deformation due to the reduction in rigidity and the thermal expansion of the steel sheet K during heating can be suppressed.
Furthermore, since the extension members Ka and Kb of the steel sheet K used when the steel sheet K is fixedly supported in the vertical direction are unnecessary portions that become unnecessary after press molding, the steel sheet K itself can be heated uniformly in whole. Moreover, in the case where the steel sheet K is a plated steel sheet, even when it is heated in the melting temperature range, there is no concern that the molten plating material will adhere to the steel sheet K again.
In the embodiment described above, since the extension members Ka and Kb are, immediately after heating, sheared and removed in the steel sheet heating apparatus 1 by the shearing mechanism 40 installed in the steel sheet heating apparatus 1, the extension members Ka and Kb, which are unnecessary portions, can be removed in a state of high temperature and low strength, and there is no influence on the shape, quality, and performance of the product after molding. The extension members Ka and Kb left on the hanging members 31 and 32 of the support member 30 after shearing may be collected to a collection box or the like via a chute (not shown) or the like. In the case where the press mold can be provided with a shearing mechanism, the extension members Ka and Kb may be sheared and removed simultaneously with the pressing in the hot press molding apparatus 60.
The hanging members 31 and 32 of the support member 30 after the steel sheet K is conveyed by the conveyance robot 50 in the above way may be moved to the backward rail housing 22 side through the support member moving path 24a and then moved to the entrance 10a side of the heating furnace 10 through the support member moving path 24b, and the steel sheet K to be processed next may be set at the hanging members 31 and 32 of the support member 30 again in a prescribed position on the entrance 10a side of the heating furnace 10.
As is clear from
Furthermore, in the embodiment described above, the movement of the hanging members 31 and 32 of the support member 30 is based on the chain conveyor 21b installed in the forward rail housing 21 and the backward rail housing 22, and an arrangement in which the drive mechanism is installed outside the heating furnace 10 and the forward rail housing 21 does not receive radiant heat directly from the opening of the heating furnace as shown in
The preferred embodiment(s) of the present disclosure has/have been described above with reference to the accompanying drawings, whilst the present disclosure is not limited to the above examples. A person skilled in the art may find various alterations and modifications within the scope of the appended claims, and it should be understood that they will naturally come under the technical scope of the present disclosure.
The present invention is useful for the heating of a steel sheet before the steel sheet is molded by hot press molding.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2014-015536 | Jan 2014 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2015/051832 | 1/23/2015 | WO | 00 |
