JP2000280020A - Manufacture of hot rolling steel band - Google Patents

Abstract

PROBLEM TO BE SOLVED: To omit a hot steel band annealing, acid pickling process and a cold rolling process by cutting or grinding the whole surface of front, rear faces of a rough rolled sheet bar from the surface to a given thickness or more. SOLUTION: A Cr contained steel slab 11 which contains Cr 5 wt.% or more by continuous casting is heated at a heating furnace 21 and is rough rolled at a hot rough rollers row 22 for making a sheet bar 12. Scale of the sheet bar 12 is completely eliminated by cutting the whole surface of the sheet bar 12 front, rear faces by 10 μm or more with a sheet bar surface cutting device 23. A front tail end of the sheet bar 12 is cut by a crop shear 24 and a finish rolling is performed at a hot finish rolling rollers row 26 without applying a descaling. After it is cooled with a cooling device 27, a winding device 28 takes up the bar so as to obtain a hot rolled stainless steel band 13 of a thin scale. A cutting depth on the sheet bar 12 front, rear faces is preferable to be within 1 mm in view of a yielding loss, an abrasion of a moving blade and a stability.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for producing a steel sheet containing 5% by weight or more of Cr
The present invention relates to a method for producing a hot-rolled steel strip of a Cr-containing steel containing Cr.

[0002]

2. Description of the Related Art Normally, stainless steel such as SUS430 and SUS304 and heat-resistant steel such as SUH409 contain 5% by weight or more of chromium. The obtained slab is heated in a heating furnace, high-pressure water is sprayed on a sheet bar obtained by performing rough rolling, descaling is performed, and then finish rolling is performed to form a hot-rolled steel strip.

[0003] Then, the hot-rolled steel strip is subjected to annealing and pickling in a hot-rolled steel strip annealing and pickling step (HAP) dedicated to Cr-containing steel, and further cold-rolled, followed by a finish annealing and pickling step. (CA
In P), finish annealing and pickling are performed to produce a cold-rolled steel strip. This cold-rolled steel strip of Cr-containing steel is used for various kitchen appliances,
Used in fields such as automotive parts.

[0004] As described above, for example, a hot-rolled stainless steel strip is passed through a hot-rolled steel strip annealing / pickling step (HAP) and a cold rolling step, so that the hot-rolled stainless steel strip is annealed and pickled. Cold rolled stainless steel strip is shipped as a product, but in this modernized hot rolling equipment line, hot rolled steel strip with a thinner thickness than before It is possible to manufacture a steel strip having a thickness of 0.8 mm to 1.2 mm which cannot be manufactured without a conventional cold rolling process.

[0005] However, the hot-rolled stainless steel strip has a large scale when hot-rolled as it is, and when it is annealed and pickled in the finish annealing / pickling step (CAP), the line speed is reduced by pickling. Because the speed is controlled, the tonnage of the hot-rolled stainless steel strip that has been annealed, pickled and cold-rolled is significantly reduced compared to annealing and pickling, resulting in reduced production capacity. For this reason, a cold rolled stainless steel strip has not been replaced with a thin hot rolled stainless steel strip.

In addition, even if a thin hot-rolled stainless steel strip having a large scale is to be treated in a hot-rolled steel strip annealing / pickling step (HAP), the hot-rolled steel strip annealing / pickling line is descaled by strong pickling. Therefore, there is a problem that unevenness is generated on the surface of the steel strip after pickling, and a quality level equivalent to that of the cold-rolled stainless steel strip cannot be obtained. Therefore, an attempt has been made to further reduce the scale thickness of the hot-rolled stainless steel strip by further increasing the pressure of the descaling by high-pressure water before hot finish rolling, but to reduce the scale of the hot-rolled stainless steel strip so much. There was a problem that it could not be reduced.

[0007]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to eliminate the above-mentioned problems of the prior art, and omit the hot-rolled steel strip annealing / pickling step (HAP) and the cold rolling step. It is an object of the present invention to provide a method for producing a hot-rolled strip of Cr-containing steel with a possible thin scale.

[0008]

According to the present invention, a Cr-containing steel slab containing at least 5% by weight of Cr obtained by continuous casting is heated in a heating furnace and rough-rolled to finish the sheet bar. In producing a hot-rolled steel strip by rolling, the entire surface of the front and back surfaces of the sheet bar is cut or ground by a depth of 10 μm or more from the surface.

Further, the cutting or grinding depth is 1 mm.
It is preferably within the range.

[0010]

FIG. 2 is a layout diagram of a row of hot rolling equipment to which the present invention is applied, 21 is a heating furnace, 22 is a row of hot rough rolling mills, and 23 is a sheet bar having a rotary blade. Surface cutting device. 24 is a crop shear, 25 is a descaling device before hot finish rolling using high-pressure water, 26 is a row of hot finish rolling mills, 27 is a cooling device, and 28 is a winding device. The row of hot rough rolling mills 22 includes coarse rolling mills (E1, E2, E3, E4) and rough horizontal rolling mills (R1, R2,
R3, R4). The hot finishing rolling mill train 26 has seven finishing horizontal rolling mills.

As shown in FIG. 3, the sheet bar surface cutting device 23 includes a rotating blade 23b having a width exceeding the sheet width of the sheet bar 12, and a rotating blade 23b approaching and separating from the sheet bar 12. Cylinder 23a to move in the direction of rotation, spindle 23c connected to rotary blade 23b, and spindle 23c
And a drive motor 23e connected to the distribution gear 23d.

An embodiment of the present invention will be described with reference to an example in which a hot-rolled stainless steel strip is manufactured using this hot-rolling equipment. The stainless steel slab 11 is obtained by continuously casting molten steel adjusted to a predetermined component using a continuous casting mold. This continuously cast stainless steel slab 11
Is heated to a predetermined temperature in the heating furnace 21 and then extracted on a line of a row of hot rolling equipment. The extracted slab 11 is subjected to rough rolling by a row of hot rough rolling mills 22 to obtain a sheet bar 12.

The present invention is characterized in that the entire surface of the front and back surfaces of the sheet bar 12 is cut by 10 μm or more by the sheet bar surface cutting device 23 so that the scale of the sheet bar 12 to be subjected to finish rolling is almost completely removed. . Then the seat bar
Cut the 12 tail end with crop shear 24,
Ku things subjected to descaling by hot finish rolling before descaling device 25 to 12 is subjected to finish rolling in the hot finish rolling mill train 26, after cooling by the cooling device 27, wound in the winding device 28, heat It is possible to produce a thin-scale hot-rolled stainless steel strip 13 which can omit the rolled steel strip annealing / pickling step (HAP) and the cold rolling step.

Before the finish rolling of the present invention, the sheet bar 12
The reason for cutting the entire front and back surfaces of the front and back is that if the entire front and back surfaces of the hot-rolled stainless steel strip 13 after finish rolling are cut,
Since the length is longer than the sheet bar 12, the efficiency is poor.On the other hand, if the entire front and back surfaces of the sheet bar 12 are cut before performing the rough rolling, scale is generated in the rough rolling process. This is because the scale thickness of the hot-rolled stainless steel strip 13 cannot be reduced.

The entire surface of the front and back surfaces of the sheet bar 12 is
The reason for cutting 10 μm or more is that if the grinding amount on the entire surface of the front and back surfaces of the sheet bar 12 is less than 10 μm in depth, the scale thickness of the hot-rolled stainless steel strip 13 becomes 1.0 μm or more. This is because the pickling step (HAP) and the cold rolling step cannot be omitted. In addition, the depth of grinding of the front and back surfaces of the sheet bar 12 is set at 1 from the viewpoint of yield loss for cutting the entire front and back surfaces of the sheet bar 12, wear of the rotary blade, and grinding stability.
It is preferably within mm.

According to the present invention, the scale before the finish rolling can be almost completely removed by cutting the entire surface of the front and back surfaces of the sheet bar 12 by 10 μm or more by the sheet bar surface cutting device 23 before performing the finish rolling. It is not necessary to perform descaling with high-pressure water in the descaling device 25 before hot finish rolling. When descaling with high-pressure water is not performed, the high-pressure water pump that supplies high-pressure water can be stopped, thereby achieving an energy saving effect. However, from the sheet bar surface cutting device 23,
If the sheet bar passing speed is so low that the generation of oxide scale is concerned while the sheet bar is conveyed to the hot finishing mill train 26, descaling with high-pressure water may be performed.

Here, as shown in FIG. 3, in the sheet bar surface cutting device 23, a rotary blade 23b having a length exceeding the sheet width of the sheet bar is driven by a drive motor 23e via a spindle 23c and a distribution gear 23d. At the same time, since the cylinder 23a is moved toward and away from the sheet bar 12 by the cylinder 23a, the entire front and back surfaces of the sheet bar 12 can be cut by a predetermined amount.

In the above description, it has been described that the entire surface of the front and back surfaces of the sheet bar 12 is ground using the rotary blade. However, instead of the rotary blade, a sheet bar surface polishing apparatus using a rotary grindstone is installed and the sheet bar is polished. The entire front and back surfaces of the 12 may be polished.

[0019]

EXAMPLE The stainless steel slab 11 used in this example was used.
Is a continuously cast ferritic stainless steel with a thickness of 200 mm and a width of 1300 mm (C: 0.07 wt%, Si: 0.3 wt%, Mn: 0.1 wt%, Cr:
17wt%). This continuously cast stainless steel slab
11 was soaked at 1200 ° C. for 2 hours in a heating furnace 21 shown in FIG. Slabs extracted11
The sheet bar 12 was subjected to rough rolling to obtain a sheet bar 12 having a thickness of 30 mm.

In the example of the present invention, before the finish rolling, the entire front and back surfaces of the sheet bar 12 are cut to a depth of 1 mm by the sheet bar surface cutting device 23 in the range from the front end (the front end to the center in the longitudinal direction). On the other hand, in the range from the rear end side of the sheet bar 12 (from the rear end to the center in the length direction), the entire front and back surfaces are 10
μm was cut. Then, the leading end of the sheet bar 12 is cut with a crop shear 24, and without subjecting the sheet bar 12 to descaling of high-pressure water by the descaling device 25 before hot finish rolling, at a finishing inlet temperature of 1000 ° C. After finish rolling and cooling by a cooling device 27, the roll was wound by a winding device 28 to produce a hot-rolled stainless steel strip 13 having a thickness of 1.0 mm.

Next, in the finish annealing / pickling step (CAP), finish annealing / pickling was performed to obtain a hot rolled stainless steel strip after the finish annealing / pickling. When the change of the scale thickness of this invention example was examined, as shown in FIG.
The scale thickness of the sheet bar 12, which was 10 μm on the delivery side, was changed to the descaling apparatus 25 before hot finish rolling on both the front end side of the sheet bar 12 cut by 1 mm depth and the rear end side of the sheet bar 12 cut by 10 μm depth. 0.3 μm on the inlet side of the steel, and 1.5 μm on the outlet side of the descaling unit 25 before hot finish rolling.
After hot finish rolling, the hot rolled stainless steel strip 13 that had been cooled and wound up had a scale thickness of 0.7 μm.

Further, the surface condition and material of the hot-rolled stainless steel strip after finish annealing and pickling of this invention were examined, and the surface quality and material of the conventional cold-rolled stainless steel strip described below were examined. Was equivalent to In the conventional example, a slab having the same components and dimensions as those of the invention example was soaked in a heating furnace 21 at 1200 ° C. for 2 hours, and then rough-rolled into a sheet bar 12 having a thickness of 30 mm. Without grinding, finish rolling is performed at 1000 ° C. on the finishing inlet side to obtain a hot-rolled stainless steel strip having a thickness of 2.0 mm. The hot-rolled stainless steel strip is annealed and pickled in a hot-rolled stainless steel strip ( HAP) annealing and pickling and cold rolling to a thickness of 1.0 mm, and finish annealing and pickling in the finish annealing and pickling process (CAP) to form a cold rolled stainless steel strip. is there.

Here, the scale thickness of the hot-rolled stainless steel strip 13 of the conventional example was 3.0 μm. On the other hand, in the comparative example, a slab having the same components and dimensions as those of the invention example was 12
After soaking at 00 ° C. × 2 hours, the sheet bar 12 was roughly rolled to obtain a sheet bar 12 having a thickness of 30 mm. The front and back surfaces of the sheet bar 12 were not ground, but were subjected to finish rolling at a finishing inlet temperature of 1000 ° C. Thickness 1.
Manufactured with 0 mm hot rolled stainless steel strip. Next, in the finish annealing / pickling step (CAP), annealing and pickling were performed at the same line speed as in the invention example to obtain a hot-rolled stainless steel strip after finish annealing / pickling.

When the change in the scale thickness of the comparative example was examined, as shown in FIG.
On the exit side, the same 10 μm sheet bar as the invention example
The scale thickness of 12 was 10 μm on the entry side of the hot finish rolling descaling device 25 because the front and back surfaces of the sheet bar were not cut by the sheet bar surface cutting device 23, On the delivery side, the thickness was 10 μm, which was thicker than that of the invention, and the scale thickness of the hot-rolled stainless steel strip 13 that was cooled after finish rolling was 3.0 μm.

Further, when the surface condition and the material of the hot-rolled stainless steel strip after annealing and pickling of the comparative example were examined, the scale was left unreliable. From the above results, before performing the finish rolling of the present invention, by cutting the entire surface of the front and back surfaces of the sheet bar by 10 μm or more, a hot-rolled stainless steel strip having a thinner scale thickness than that of the comparative example without grinding is obtained. It can be seen that it can be obtained.

Further, the surface condition and material of the hot-rolled stainless steel strip after finish annealing and pickling of the invention example were the same as the surface quality and material of the conventional cold-rolled stainless steel strip. It can be seen that the steel strip annealing / pickling step (HAP) and the cold rolling step can be omitted. In the above embodiment, an example in which the present invention is applied to the production of a hot-rolled stainless steel strip is shown, but the present invention is also applied to the production of a hot-rolled steel strip of Cr-containing steel such as SUH409. it can.

[0027]

As described above, according to the present invention,
A thin-scale hot-rolled steel strip which can omit the hot-rolled steel strip annealing / pickling step (HAP) and the cold rolling step can be manufactured.

[Brief description of the drawings]

FIG. 1 is a graph showing the effect of reducing the scale thickness according to the present invention.

FIG. 2 is a layout diagram showing a row of hot rolling equipment to which the present invention is applied.

FIG. 3 is a schematic configuration diagram of a sheet bar surface cutting device used in the present invention.

[Explanation of symbols]

 11 Slab 12 Sheet bar 13 Hot rolled stainless steel strip 21 Heating furnace 22 Hot rough rolling mill line 23 Sheet bar surface cutting device 23a Cylinder 23b Rotary blade 23c Spindle 23d Distribution gear 23e Drive motor 24 Crop shear 25 Before hot finish rolling Descaling device 26 Hot finishing mill train 27 Cooling device 28 Winding device

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Atsushi Yuki 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba F-term in the Chiba Works, Chiba Works (reference) 4E002 AA07 AD02 AD04 BD02 BD08 BD10 BD20 CB08

Claims (1)

[Claims] 1% by weight or more obtained by continuous casting
The Cr-containing steel slab containing Cr is heated in a heating furnace, and the sheet bar obtained by performing rough rolling is subjected to finish rolling to produce a hot-rolled steel strip. A method for producing a hot-rolled steel strip, wherein the hot-rolled steel strip is cut or ground to a depth of 10 μm or more from a steel sheet.