Patent Application
20240318272
This application relates to a quenching apparatus, a method for quenching, a method for manufacturing a cold rolled steel sheet, and a method for manufacturing a coated steel sheet. More particularly, the application relates to a quenching apparatus that facilitates, for increasing versatility of manufacturing conditions, switching between a condition of performing quenching and a condition of not performing the quenching in a continuous annealing facility that performs annealing while a metal sheet continuously passes therethrough.
When steel sheets and other metal sheets (metal sheet products) are manufactured, in a continuous annealing facility that anneals metal sheets while causing the metal sheet to continuously pass therethrough, the quality of the material is made up by, for example, heating and then cooling the metal sheets so as to cause phase transformation.
Today, in the automobile industry, for the purpose of crash safety and reduction of the weight of a car body, demand for thickness-reduced high-tensile steel sheets increases. To manufacture the high-tensile steel sheets, a technique of rapidly cooling the steel sheets is important. As one of techniques with which a cooling rate of the steel sheets is the highest, a water quenching method is known. In the water quenching method, in order to efficiently perform water quenching in a stabilized manner, it is required to remove a steam film generated on the surface of a steel sheet by injecting, at the same time when the heated steel sheet is immersed in water, cooling water to the steel sheet through quench nozzles provided in the water. Meanwhile, there is also a demand for a steel sheet for which the water quenching is not required. To efficiently manufacture the both, it is required that whether to perform the water quenching be switched in a single manufacturing facility so as to manufacture both of the steel sheet for which the water quenching is required and the steel sheet for which the water quenching is not required in the single manufacturing facility.
For example, a cooling apparatus is proposed in Patent Literature 1. In this cooling apparatus, cooling water injection nozzles are provided in multi-stages in immersion water that cools a heated strip, and headers of the nozzles are set independent from each other and disposed so as to be spaced from each other in a traveling direction of the strip. With this configuration, gaps are formed between the nozzle headers, and a jet of cooling water caused to strike a surface of the strip to be cooled is caused to flow to the rear side of the headers through the gaps between the headers. This prevents side flows that would otherwise be generated with the related-art multi-stage nozzles, and uniformity in cooling in the sheet width direction is achieved.
However, in the cooling apparatus described in Patent Literature 1, when the condition of performing the water cooling with the cooling water injection nozzles in the immersion water is switched to the condition of not using the immersion water, the cooling water injection nozzles undergo thermal deformation due to thermal radiation from the heated strip and atmosphere. Thus, significantly time-consuming work is required for opening a furnace and removing the cooling water injection nozzles from the apparatus. This causes a problem in that the productivity is significantly degraded.
To address this, a technique has been proposed in Patent Literature 2. According to this technique, reflectors that are formed of a metal sheet or a heat insulating material and that suppress radiation and thermal conduction from a steel strip are provided between water injection nozzles and the steel strip, and, when a steel strip high-temperature condition under which the steel strip is not cooled with the water injection nozzles is changed to a quenching condition under which the steel strip is cooled with the water injection nozzles, a cooling gas is supplied to the water injection nozzles from a cooling gas supplying section. In removing the water from the steel strip after the quenching, the steel strip is pressed with a pair of pressure rolls installed so as to be shifted from each other in the longitudinal direction of the steel strip while a pair of slit nozzles are moved close to the steel strip and a gas is injected to remove the water.
However, there also is a problem with the method described in Patent Literature 2 in that the temperature of the reflectors increases and the reflectors undergo thermal deformation due to the high temperature.
The disclosed embodiments have been made to solve the problems as described above, and the object of the disclosed embodiments is to provide a quenching apparatus. In a case where quenching in which a metal sheet heated in, for example, a continuous annealing facility is immersed in a cooling medium is performed, this quenching apparatus produces a good cooling effect on the metal sheet. In addition, in a case where the quenching in which the metal sheet is immersed in the cooling medium is not performed, this quenching apparatus can prevent thermal deformation of the apparatus. Furthermore, this quenching apparatus facilitates switching between a condition of performing the quenching and a condition of not performing the quenching.
The inventors have diligently studied to solve the problems as described above and, as a result, obtained the following findings and conception.
That is, in the related-art quenching of a metal sheet (for example, a steel sheet), a steam film generated on the surface of the metal sheet is removed by a striking pressure of water injected from the water injection nozzles so as to uniformly perform the quenching. However, when the condition is switched to a condition of not using the water injection nozzles, the water injection nozzles, reflectors, and the like undergo thermal deformation. Accordingly, when the steam film generated on the surface of the metal sheet can be removed by a different apparatus that can suppress thermal deformation without using the water injection nozzles, the reflectors, or the like, it is not required to open the furnace of the annealing facility in switching between the condition of performing the quenching and the condition of not performing the quenching. Thus, thermal deformation of the water injection nozzles and the like can be suppressed.
The disclosed embodiments are based on the findings and the conception as described above and have features as described below.
[1] A quenching apparatus that cools a metal sheet, the apparatus including
[2] In the quenching apparatus according to [1], the rolls are rotated in a reverse direction to a running direction of the metal sheet.
[3] The quenching apparatus according to [1] or [2] is installed on an exit side of a soaking furnace of a continuous annealing facility.
[4] A method for quenching with which a metal sheet is cooled by using a quenching apparatus including a bath that contains a cooling medium in which the metal sheet is immersed.
In a case where quenching in which the metal sheet is immersed in the cooling medium is performed, the method includes the steps of
[5] In the method for quenching according to [4], the rolls are rotated in a reverse direction to a running direction of the metal sheet.
[6] In a method for manufacturing a cold rolled steel sheet, the metal sheet is the cold rolled steel sheet, and the cold rolled steel sheet that has been annealed is quenched with the method for quenching according to [4] or [5].
[7] In a method for manufacturing a coated steel sheet, a coating treatment is performed on the steel sheet obtained with the method for manufacturing a cold rolled steel sheet according to [6].
[8] In the method for manufacturing a coated steel sheet according to [7], the coating treatment is one treatment selected from an electrogalvanizing treatment, a hot-dip galvanizing treatment, and a hot-dip galvannealing treatment.
According to the disclosed embodiments, the quenching apparatus is provided as follows. In the case where quenching in which the metal sheet heated in, for example, the continuous annealing facility is immersed in the cooling medium is performed, this quenching apparatus produces a good cooling effect on the metal sheet. In addition, in the case where the quenching in which the metal sheet is immersed in the cooling medium is not performed, this quenching apparatus can prevent thermal deformation of the apparatus. Furthermore, this quenching apparatus facilitates switching between the condition of performing the quenching and the condition of not performing the quenching.
According to the disclosed embodiments, for the metal sheet (for example, the steel sheet) heated in the continuous annealing facility that performs annealing while causing the metal sheet to continuously pass therethrough, when switching between the condition of performing the quenching and the condition of not performing the quenching is performed, the need for the following work is dropped: opening the furnace of the continuous annealing facility; removing members that is disposed in the bath of the quenching apparatus for preventing thermal deformation caused by thermal radiation from the metal sheet; and installing the reflectors to prevent thermal deformation in the bath. Accordingly, the switching is facilitated. Thus, both the metal sheet required to be quenched and the metal sheet not required to be quenched can be manufactured with a single quenching apparatus with high productivity.
Furthermore, thermal deformation caused by thermal radiation from the metal sheet can be suppressed.
An embodiment will be described below with reference to the drawings. However, the disclosure is not intended to be limited to the embodiment described below.
As illustrated in
As illustrated in
In
Preferably, the rolls 4 (the rolls 4a and the rolls 4b) are disposed at positions where the outer periphery of the rolls are in contact with the metal sheet 1. In this case, the most significant effect can be obtained.
When the quenching is performed, the rolls 4 (the rolls 4a and the rolls 4b) rotate at a peripheral speed higher than or equal to a running speed of the metal sheet 1. More specifically, the peripheral speed of the rolls 4 is preferably a relative speed higher than or equal to 1.0 times the running speed of the metal sheet 1. When the peripheral speed of the rolls 4 is a relative speed lower than 1.0 times the running speed of the metal sheet 1, agitating performance reduces. Thus, the effect of removing the steam film from the surfaces of the metal sheet 1 is not sufficiently obtained, and accordingly, the effect of cooling the metal sheet 1 is not sufficiently obtained. Furthermore, the peripheral speed of the rolls 4 is preferably a relative speed lower than or equal to 3.0 times the running speed of the metal sheet 1. When the peripheral speed of the rolls 4 is a relative speed lower than or equal to 3.0 times the running speed of the metal sheet 1, generation of flaws on the surface of the metal sheet 1 is easily suppressed.
Although the rotation direction of the rolls 4 (the rolls 4a and the rolls 4b) is not limited, for more efficiently improving the agitating performance for agitating the steam film on the surface of the metal sheet 1, the rolls 4 are preferably rotated in a reverse direction to the running direction of the metal sheet 1 (see
Furthermore, a roll diameter of the rolls 4 (the rolls 4a and the rolls 4b) is preferably greater than or equal to 50 mm. When the roll diameter is smaller than 50 mm, bending is likely to occur in the rolls 4 due to a reaction force from the metal sheet 1. Furthermore, the roll diameter of the rolls 4 (the rolls 4a and the rolls 4b) is preferably smaller than or equal to 250 mm. When the roll diameter is smaller than or equal to 250 mm, the agitating performance is improved. Thus, the effect of removing the steam film from the surface of the metal sheet 1 is more improved, and accordingly, a better effect of cooling is easily obtained.
Although the number of rolls disposed in the bath 5 is not limited, it is required that at least a pair of rolls be disposed such that the metal sheet 1 is interposed between the pair of rolls. Furthermore, a plurality of rolls are preferably disposed on each of the front surface side and the rear surface side of the metal sheet 1. With this configuration, the steam film can be more uniformly and more reliably removed, and accordingly, stable cooling power is obtained. In order to obtain the same cooling power on the front and rear surfaces of the metal sheet 1, the numbers of rolls disposed on the front surface side and the rear surface side of the metal sheet 1 are preferably the same, and each of the rolls disposed on the front surface side is preferably paired with a corresponding one of the rolls disposed on the rear surface side. The number of rolls to be disposed is preferably greater than or equal to three pairs. When the number of rolls to be disposed is greater than or equal to three pairs, the steam film on the surface of the metal sheet 1 can be more uniformly and more reliably removed, and accordingly, stable cooling power is easily obtained. Although an upper limit of the number of rolls 4 to be disposed is not particularly defined, the number of rolls to be disposed is preferably smaller than or equal to ten pairs. When the number of rolls to be disposed is smaller than or equal to ten pairs, it is preferable in terms of the cost. The rolls may be in contact or not in contact with each other. The quenching apparatus according to the disclosed embodiments agitates the cooling medium (the liquid) with the rolls to obtain the effect of removing the steam film from the surface of the metal sheet, and accordingly, obtain a better effect of cooling on the metal sheet. Thus, it is not required that cooling water injection nozzles be installed in the bath of the quenching apparatus.
Regarding the material of the rolls 4 (the rolls 4a and the rolls 4b), it is sufficient that the rolls 4 (the rolls 4a and the rolls 4b) be formed of a material that has strength to withstand the reaction force of the metal sheet 1. Examples of the material of the rolls 4 include, for example, SUS304, SUS310, ceramic, and so forth.
As illustrated in
In
As described above, in the quenching apparatus 11 according to the present embodiment, the distances between the rolls 4 (the rolls 4a and the rolls 4b) and the metal sheet 1 can be changed depending on the condition whether the quenching is performed (
The disclosed embodiments are preferably applied to a method for manufacturing a steel sheet. In particular, when the quenching apparatus according to the disclosed embodiments is installed on the exit side of a soaking furnace of a continuous annealing facility through which steel sheets of different steel types continuously pass, the quenching apparatus can be more effectively used. Furthermore, the quenching apparatus can also be used for shape correction of the metal sheet by adjusting installation positions of the rolls and disposition relationship with the metal sheet running in the bath of the quenching apparatus.
Examples of the above-described steel sheet include a cold rolled steel sheet, and a hot-dip galvanized steel sheet, an electrogalvanized steel sheet, a hot-dip galvannealed steel sheet, and the like that are made by performing a surface treatment on the cold rolled steel sheet. The disclosed embodiments are preferably applied to a method for manufacturing a cold rolled steel sheet in which an annealed cold rolled steel sheet is quenched and to a method for manufacturing a coated steel sheet in which the cold rolled steel sheet is further subjected to a coating treatment. The coating treatment is at least one treatment selected from an electrogalvanizing treatment, a hot-dip galvanizing treatment, a hot-dip galvannealing treatment, and the like. The disclosed embodiments are not limited to examples of manufacturing steel sheets but are applicable to manufacturing of metal sheets in general other than steel sheets.
Examples of the disclosed embodiments are described. However, the disclosure is not intended to be limited to the examples described below.
In the present examples, a cooling apparatus used after high-tensile steel sheets having a thickness of 0.8 to 2.3 mm had undergone a treatment in a continuous annealing facility was changed. Specifically, according to the present examples, examples are described in which a quenching apparatus was installed on the exit side of the continuous annealing facility, the above-described high-tensile steel sheets were annealed in the continuous annealing facility, and, after that, a steel sheet (coil) of a tensile strength target of 780 to 1470 MPa and a steel sheet (coil) of a tensile strength target of 340 to 590 MPa were manufactured with the same quenching apparatus.
As a related-art example, a quenching apparatus described in Patent Literature 2 was installed on the exit side of the continuous annealing facility. In order to obtain the mechanical properties of the steel sheet of a tensile strength target of 780 to 1470 MPa, the quenching (water quenching) was performed with the above-described quenching apparatus, and 200 pieces of the coil of a tensile strength target of 780 to 1470 MPa were manufactured. Then, 200 pieces of the coil of a tensile strength target of 340 to 590 MPa were manufactured. In so doing, since the water quenching was not required, water in the water bath of the above-described quenching apparatus was discharged, reflectors for protection were installed for water injection nozzles installed in the water bath. The steel sheets having undergone continuous annealing were run in the water bath of the quenching apparatus in this state, and 200 pieces of the coil of a tensile strength target of 340 to 590 MPa were manufactured. As a result, the reflectors underwent thermal deformation.
As a comparative example, the above-described quenching apparatus 11 (excepting that the rolls 4 (the rolls 4a and the rolls 4b) were forcibly fixed so as not to rotate) was installed on the exit side of the continuous annealing facility. In order to obtain the mechanical properties of the steel sheet of a tensile strength target of 780 to 1470 MPa, the quenching (water quenching) was required. Accordingly, water was poured into the water bath 5 as illustrated in
As an Example, the above-described quenching apparatus 11 was installed on the exit side of the continuous annealing facility. In order to obtain the mechanical properties of the steel sheet of a tensile strength target of 780 to 1470 MPa, the quenching (water quenching) was required. Accordingly, water was poured into the water bath 5 as illustrated in
In example 1, the rotation directions of the steel sheet and the rolls 4 (the rolls 4a and the rolls 4b) were set to be the same, and the rolls were rotated at a peripheral speed 2.0 times the steel sheet running speed (when the steel sheet was 1000 mm/s, the roll peripheral speed was 2000 mm/s; the peripheral speed of the rolls was a relative speed 2.0 times the running speed of the metal sheet 1). Under these conditions, when 200 pieces of the coil of a tensile strength target of 780 to 1470 MPa were manufactured, a good cooling effect was obtained, and the target strength was achieved in all the pieces of the coil. Then, continuously, 200 pieces of the coil of a tensile strength target of 340 to 590 MPa were manufactured in a state in which the rolls 4 (the rolls 4a and the rolls 4b) were spaced from the steel sheet by 500 mm in the horizontal direction and the water was discharged from the water bath 5 as illustrated in
In example 2, the rotation directions of the steel sheet and the rolls 4 (the rolls 4a and the rolls 4b) were set to be reverse to each other, and the rolls 4 (the rolls 4a and the rolls 4b) were rotated at the peripheral speed that is the same as the steel sheet running speed (when the steel sheet was 1000 mm/s, the roll peripheral speed was 1000 mm/s; the peripheral speed of the rolls 4 was a relative speed 2.0 times the running speed of the metal sheet 1). Under these conditions, when 200 pieces of the coil of a tensile strength target of 780 to 1470 MPa were manufactured, a good cooling effect was obtained, and the target strength was achieved in all the pieces of the coil. Then, continuously, 200 pieces of the coil of a tensile strength target of 340 to 590 MPa were manufactured in a state in which the rolls 4 (the rolls 4a and the rolls 4b) were spaced from the steel sheet by 500 mm in the horizontal direction and the water was discharged from the water bath 5 as illustrated in
| Number | Date | Country | Kind |
|---|---|---|---|
| 2021-125060 | Jul 2021 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2022/021485 | 5/26/2022 | WO |
