JPS61283403A - Hot rolling method for clad steel - Google Patents

Abstract

PURPOSE:To decrease the camber during rolling and to decrease the deviation in the thickness of a cladding metal by forcibly cooling the material surface on the side where the hot deformation resistance is small just prior to hot rolling to maintain the surface temps. of the cladding metal and base metal in a specific range. CONSTITUTION:The material surface on the side where the hot deformation resistance is small is forcibly cooled just prior to the hot rolling of a clad steel consisting of different materials. A difference of 50-150 deg.C is generated in the surface temps. of the cladding metal and the base metal by such cooling treatment. The thickness deviation at the transverse end and the longitudinal end is decreased when the materials are rolled in this state. The camber after the rolling is suppressed to about <=100mm.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for hot rolling clad steel plates made of different materials having different hot deformation resistances.

(Prior art) There are various methods for manufacturing double-layer clad plates, but in the method for manufacturing clad steel that goes through a hot rolling process from a slab, the heat of the laminated material and base material is reduced during hot rolling. Due to the difference in deformation resistance, large warpage occurred due to the difference in elongation.

In addition, at the end of the steel plate, only the side with low deformation resistance elongates well, resulting in parts that are not clad steel, and even in the cladding part, the side with high deformation resistance becomes locally thick, creating so-called unsteady parts.

Conventionally, in order to solve these problems, methods have been used in advance, such as thinning the end of the slab on the side of the material that has greater resistance to hot deformation, or attaching restraining plates to the end of the slab (Japanese Patent Application No. 1983). -149635) was being carried out.

(Problems to be Solved by the Invention) When hot-rolling a clad steel slab made of a composite material and a base material that have different hot deformation resistances, the difference in deformation resistance causes the slab to warp significantly. It was hitting between the rollers and reducing efficiency. Furthermore, due to the difference in deformation resistance between the laminated material and the base material, there will be areas where the material with high deformation resistance becomes extremely thick locally as the material with low deformation resistance stretches, which may cause problems with corrosion resistance. Due to strength guarantee issues, some parts were not made into products, resulting in poor yields.

In addition, the methods of thinning the end of a slab made of a material with high resistance to hot deformation in advance or attaching restraining plates to the end of the slab require a large amount of work and increase costs.

(Means for Solving the Problems) The present invention provides a method for hot rolling clad steel made of different materials with different hot deformation resistances. This is a method for hot rolling clad steel, which is characterized in that rolling is performed by forced cooling and with a surface temperature difference of 50 to 150°C between the laminated material and the base material.

(Function) When the above-mentioned base material and composite material are hot-rolled, a portion where the cladding ratio is not constant (
The unsteady portion (hereinafter referred to as unsteady portion) occurs within several passes immediately after the start of rolling. Therefore, in the present invention, the slab is cooled immediately before rolling.

The temperature difference will be explained. Figure 2 shows the relationship between material temperature and hot deformation resistance of each material.
41) and stainless steel (SU
S 304, etc.) or copper alloy (C7060P, etc.), a temperature difference of 100° C. or more is required to obtain the same deformation resistance. However, as a result of various experiments, the present inventor found that
It was found that a lower limit of the temperature difference of 50°C or more is sufficient. Figure 1 shows SM 4 using SOS 304 as a laminating material.
1 For clad steel when B is used as the base material, the difference between the unsteady part and the normal part (part with a constant cladding ratio) when the surface temperature difference is varied, that is, the thickness deviation of the unsteady part. As can be seen from this figure, when the temperature difference becomes 50° C. or more, the deviation decreases.

Regarding the upper limit, the temperature difference was limited to 50 to 150°C because if an attempt was made to create a temperature difference of 150°C or more, the overall temperature would drop during cooling of the slab, making rolling impossible.

Furthermore, regarding the cooling range, there was no need to cool the inside of the material, which has low deformation resistance, and it was sufficient to cool only the surface.

That is, in the case of normal rolling, the surface portion is well elongated in the initial stage, and as the plate thickness decreases, the overall elongation gradually increases.

This is because the slab itself has a temperature distribution (deformation resistance distribution) in the thickness direction. Therefore, if the surface is cooled immediately before rolling, the purpose can be sufficiently achieved.

(Example) In order to compare the method of the present invention and the conventional method, the base material is S
M 41 [+, the steel type with SOS 316 L as the laminated material was rolled to the same product size using materials with the same slab size.

The heating temperature of the slabs was 1220°C x 511r in both cases, and in the conventional method, the upper and lower surfaces were descaled immediately before rolling so that the temperature difference between the upper and lower surfaces was 20°C.

On the other hand, the present invention uses single-sided descaling to cool the entire slab surface on the SM 41 B side of the base material immediately before rolling,
The rolling temperature was 60°C lower than that of the stainless steel side.

After rolling, samples were taken from the ends of the steel plate in the width direction and length direction, and the deviation in the thickness of the laminated material was investigated. The results are shown in FIGS. 3 and 4. In the conventional method, the deviation at the end in the middle direction is 1. Q+n, the deviation of the ends in the longitudinal direction is 2.2 Tsuru. In contrast, in the method of the present invention, the deviation Q at the end in the middle direction is 2 mm, and the deviation Q at the end in the longitudinal direction is 7 m.
m, showing a remarkable effect.

Further, the warpage after rolling, which occurred in the conventional method by more than 300 am, could be suppressed to less than 100 am by the method of the present invention.

Although this embodiment has been explained using a stainless steel clad plate, the present invention is not limited thereto, and is effective in manufacturing all clad steel plates having different hot deformation resistances.

(Effects of the Invention) As described above, according to the present invention, the warpage during rolling of a clad steel plate can be significantly reduced, and the deviation in the thickness of the laminated material can be greatly improved.

[Brief explanation of drawings]

Figure 1 is a diagram showing the surface temperature difference and unsteady part thickness deviation of the material, Figure 2 is a diagram showing the material temperature and hot deformation resistance of various materials, and Figure 3a is a diagram showing the middle direction end by the conventional method. FIG. 3b is a diagram showing the relationship between the distance from the center end and the thickness of the laminated material according to the method of the present invention, and FIG. FIG. 4B is a diagram showing the relationship between the distance from the longitudinal end and the thickness of the laminated material according to the method of the present invention, and FIG. 4b is a diagram showing the relationship between the distance from the longitudinal end and the thickness of the laminated material according to the method of the present invention. . Figure 1 2040 60 f30 1001201401601
130 ZOOA face late age bald (0C) 700 1300'? 00 1000
f100 Oomitozuki Rido (0C) Fig. 3a Width 1'i1 End ◆＼Ra Q distance (m star) Fig. 3b

Claims (1)

[Claims] 1. In a method of hot rolling clad steel made of different materials with different hot deformation resistances, just before rolling, only the material surface on the side with smaller hot deformation resistance is forcibly cooled, and the surfaces of the mating material and the base material are cooled. A method for hot rolling a clad steel plate, characterized by rolling with a temperature difference of 50 to 150°C.