JP2617062B2 - Temper rolling method for metal strip - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an automobile, a railway vehicle,
An object of the present invention is to propose a temper rolling method for obtaining a metal band having a surface hardened layer suitable for use as an exterior member, a sliding member, or a spring material of a building material, an electric appliance, or the like. In recent years, steel sheets for the above applications have excellent workability such as pressing, bending, drawing, punching and shearing, as well as abrasion resistance and scratch resistance of the steel sheet surface without impairing these properties. It is also desired to improve the shearing burr resistance and the like.

[0002]

2. Description of the Related Art Conventionally, a method of controlling the hardness of a steel sheet in temper rolling involves a method in which the work hardening characteristics of a steel type of the steel sheet are grasped in advance, and a reduction ratio for obtaining a predetermined hardness is selected. Used. Furthermore, in addition to the above, there is also known a method of controlling the temperature and rolling speed of a steel sheet during rolling for the purpose of improving the accuracy. In these methods, the hardness is uniformly controlled without distinction between the inside and the surface layer of the steel sheet. Not only to provide a surface hardened layer, but naturally, the surface hardened layer is hardened. There was no control over the pod depth.

Therefore, as described above, surface hardening suitable for improving abrasion resistance, scratch resistance and shearing resistance without impairing the workability of a press or the like required for this type of steel sheet. No layers could be applied.

[0004]

SUMMARY OF THE INVENTION The present invention proposes a temper rolling method capable of providing a surface hardened layer, which cannot be obtained by the above-mentioned conventional method, and appropriately controlling the hardness and depth thereof. By doing so, it is intended to obtain a steel sheet having excellent wear resistance, scratch resistance, shearing resistance and the like.

[0005]

SUMMARY OF THE INVENTION According to the present invention, a tempered rolling of a steel strip is performed by appropriately selecting the surface roughness of the rolling roll and the roll diameter, and by appropriately combining them. It has been found that the surface hardness and the depth of the surface hardened layer can also be controlled.

[0006] That is, the gist of the present invention is that the surface roughness Ra of the rolling roll is set to 0.3 µ
This is a temper rolling method characterized by having a diameter of 20 mm or more and 3.0 μm or less and a diameter of 20 mm or more and 160 mm or less.

[0007]

According to the present invention, as described above, pressing, bending,
Without impairing workability such as punching and shearing, with the aim of performing a temper rolling to provide a suitable surface hardened layer to improve wear resistance, scratch resistance and shear burr resistance, In the temper rolling for this purpose, it is necessary to appropriately select the surface roughness of the rolling roll and the roll diameter.

The reason for limiting the surface roughness range of the temper roll and the roll diameter range will be described below. Rolling roll of appropriate roll diameter, surface roughness Ra 0.3 μ
If it is more than m, a surface hardened layer is formed on the steel sheet. And Ra
As is further increased, the surface hardness increases while the hardness at the center in the thickness direction is kept constant. However, if Ra is increased unnecessarily, a stable surface hardened layer cannot be obtained. Therefore, from the viewpoint of the manifestation of the effect and the practicality as a product plate, the surface roughness Ra is 0.3 μm or more,
The range is 3.0 μm or less.

On the other hand, an effective surface hardened layer can be obtained by setting the roll diameter of the roll having the above surface roughness range to 160 mm or less. Then, as the roll diameter is further reduced, the hardness of the surface hardened layer increases while the hardness of the center portion in the thickness direction is kept constant, and the depth of the surface hardened layer becomes shallower. However, as a work roll of a wide-width rolled material, if the roll diameter is less than 20 mm, the diameter is too small and operation becomes difficult. Therefore, the diameter of the rolling roll is
The range is 20mm or more and 160mm or less.

As described above, when performing temper rolling, the surface roughness and the diameter of the rolling roll are selected, and by appropriately combining them, the hardness distribution in the thickness direction of the steel sheet at the center in the sheet thickness direction is obtained. A surface hardened layer whose slope descends from the surface of the plate to the center while keeping the surface constant, and the hardness of the surface and the depth of the surface hardened layer can be controlled, and workability such as pressing Without impairing the surface resistance, it is possible to obtain a steel sheet having a surface hardened layer effective for improving wear resistance, scratch resistance, and shearing burrs.

[0011]

[Example] C: 0.06 wt%., Si: 0.5 wt.
%, Mn: 1.0 wt%, Cr: 18.2 wt%, Ni: 9.0 wt%, P:
A continuous cast slab containing 0.04 wt% and S: 0.002 wt% is subjected to hot rolling, cold rolling and intermediate annealing according to a conventional method, and then temper rolling is performed by changing the surface roughness of the roll and the roll diameter. subjected to a product plate SUS 304 * 1 / 2H plate thickness 0.20 mm, it was investigated thickness direction of the hardness (H _V) distribution from the plate surface.

First, the diameter of the roll surface was fixed at 40 mm, and the surface roughness of the roll was A: 0.05 μm (comparative example), B: 0.5 μm (applicable example), and C: 2.0 μm (applicable example). FIG. 1 shows the hardness distribution in the thickness direction of the obtained steel sheet. The roll surface roughness Ra 0.0
5 μm is a value usually used for the BA finish temper rolling of a cold rolled stainless steel strip.

As is apparent from FIG. 1, the comparative example of A is
Although there is almost no difference in hardness between the surface and the inside, a hardened layer is seen in the conforming examples of B and C. In these conforming examples, the internal hardness is not different from A, but the surface hardness is high, and C having a large roll surface roughness Ra has a high surface hardness, and the surface hardened layer is deep. Has become. Therefore, these results indicate that the roll surface roughness Ra
It is shown that by increasing the surface hardness, the hardness of the surface can be increased while the hardness of the central part of the steel sheet is kept constant, and the depth of the surface hardened layer can be increased.

The larger the roll surface roughness Ra is,
It is presumed that the higher steel sheet surface hardness promotes work hardening microscopically.

Next, the surface roughness Ra of the rolling roll is set to 0.6.
D: 40 mm (conforming example) E: 80 mm (conforming example) F: 160 mm (conforming example) FIG. 2 shows the hardness distribution.

As is apparent from FIG. 2, the internal hardness does not change, but as the roll diameter decreases, the surface hardness increases and the depth of the hardened surface layer decreases. That is,
These results indicate that the surface hardness and the depth of the hardened layer can be adjusted not only by the roll surface roughness but also by the roll diameter.

Furthermore, the above-mentioned rolling roll, namely, C: Ra 2.0 μm, diameter 40 mm (applicable example) F: Ra 0.6 μm, diameter 160 mm (applicable example) FIG. 3 shows the hardness distribution of the obtained steel sheet in the thickness direction. As is apparent from FIG. 3, the combination of different roll surface roughness and roll diameter results in completely different surface hardness and depth of the case hardened layer while having the same internal hardness.

As described above, by appropriately combining the roll surface roughness and the roll diameter, the surface hardness, the depth of the hardened layer, and the distribution of the hardness in the thickness direction can be properly selected. In addition, this method can simultaneously impart different surface hardness, surface hardened layer depth, and hardness distribution in the thickness direction to the front and back of the steel sheet.

The depth of the hardened surface layer of the steel sheet in the present invention is at most up to several tens of μm, and such a hardened layer depth impairs workability such as pressing, bending, drawing, punching and shearing. Never.

[0020]

According to the present invention, in temper rolling, by appropriately selecting the surface roughness and roll diameter of the rolling roll and combining them, a surface hardened layer is imparted to the steel sheet, and the surface hardness and surface hardening are improved. It also controls the depth of the layer, the steel sheet temper rolled by the method of the present invention,
While having excellent workability, it has high abrasion resistance, scratch resistance, and shear burr resistance, and can exert its effect independently on the front and back of the steel sheet,
It can be advantageously used for automobiles, railway vehicles, other exterior members, sliding members or spring materials.

[Brief description of the drawings]

FIG. 1 is a graph showing a hardness distribution in a thickness direction of a steel sheet obtained by temper rolling in which the surface roughness of a rolling roll is changed.

FIG. 2 is a graph showing a hardness distribution in a thickness direction of a steel sheet obtained by temper rolling in which the diameter of a rolling roll is changed.

FIG. 3 is a graph showing a hardness distribution in a thickness direction of a steel sheet obtained by temper rolling with different combinations of the surface roughness of the roll and the roll diameter.

Claims (2)

(57) [Claims] 1. A temper rolling method in which a temper rolling of a metal strip has a surface roughness Ra of the rolling roll of 0.3 μm or more and 3.0 μm or less, and a diameter of 20 mm or more and 160 mm or less. 2. The temper rolling method according to claim 1, wherein one or both of the surface roughness Ra and the diameter of the upper and lower rolls are different during the temper rolling of the metal strip.