JPS6386817A - Production of stainless clad steel - Google Patents

Abstract

PURPOSE:To prevent the diffusion of carbon from a high carbon steel to stainless steel and to prevent the development of cracking in the high carbon steel at the time of cold rolling by coating Ni film having the specific thickness on joining face in the three layer clad steel, to hot-roll and heat-treating at the limited condition after winding t the specific temp. CONSTITUTION:In the production of three layer stainless clad steel using carbon tool steel as core material and stainless steel as claded material, the Ni film is coated on the joining face at 0.2-1% of clad steel thickness after clading as the thickness thereof, to hot-roll and wind, so that the coil temp. becomes to 600-650 deg.C. Next, the hot-rolled strip is heat-treated at the inside of range, encircled by the coordinates A, B, C, D, E, F, H, H in the coordinate putting the heating temp. and holding time as coordinate axes respectively. In succession, it is cold-rolled. In this way, the stainless clad steel can be produced from a large ingot or slab.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing stainless clad steel, and more particularly to a method for manufacturing stainless clad steel that suppresses carbon diffusion and movement at joint surfaces and prevents cracks in the core material during cold rolling.

[Conventional technology]

When high carbon steel and stainless steel ε4 having a low carbon content are used as clad steel, there is a problem that carbon diffuses and moves from the high carbon steel to the stainless steel during the heat treatment process. When carbon diffusion and movement occurs in stainless steel clad steel for cutlery, there are problems such as deterioration of sharpness, reduction in corrosion resistance of stainless steel, and decrease in commercial value due to unclear joint interface.

Technologies for preventing this diffusion and movement of carbon include, for example, Metal Surface Technology Overview (February 20, 1971, published by Nikkan Kogyo Shimbun),
(page 1097).

This is done before joining high carbon steel and stainless steel.
Electroplating the cuff. (b) A metal layer consisting of 5 to 40% Cr, 16 to 5% Ni, etc. is inserted between high carbon steel and stainless steel before they are joined.

These methods of inserting plating or metal layers on the joint surfaces are effective to some extent, but if you want to get good results when using large steel ingots or large slabs, it is necessary to increase the thickness of the plating or metal layer. It needs to be quite thick,
This caused the problem of rising prices. In addition, it is difficult to plate large steel ingots or large slabs thickly and uniformly, and in the case of thick plating, there is a problem with the adhesive strength with the base material, and there is a concern that it may peel off during cold rolling.

In addition, cladding rust in which the core material is high carbon steel and the mating material is stainless steel is manufactured by casting or assembled slabs, but it is also a big problem that the high carbon steel core material cracks during cold rolling. there were.

[Problem that the invention seeks to solve]

The purpose of the present invention is to provide a method for manufacturing stainless steel clad Sη that can solve the problems of the prior art described above, prevent carbon diffusion from high carbon 1i1 to stainless steel, and prevent cracks in high carbon steel during cold rolling. It is on offer.

[Means and operations for solving the problems] The gist of the present invention is as follows.

That is, in a method for manufacturing three-layer stainless clad steel in which the core material is carbon tool rust hook material 5KI-5K5 and the mating material is stainless steel, the material thickness after joining on the joint surface is 02~
The drawing shows the process of providing a 1% thick Nl film, the hot rolling process in which the coil winding temperature is in the range of 600 to 500°C, and the heating temperature and holding time before cold rolling as the coordinate axes. A stainless steel product comprising the step of heat-treating a hot-rolled steel strip at a heating temperature and holding time within a range surrounded by the following coordinates A, B, C, D, E, F, G, and H. This is a method for manufacturing clad steel.

Coordinates Heating temperature (℃) Holding time (minutes) A
700
3B 750
2C7501 D 800
1E 850
1F 8
00 2G
800 3H
7503 As mentioned above, it is effective to provide a Ni film to prevent carbon diffusion and movement at the joint surface, but in the present invention, the Ni film thickness is reduced as much as possible by limiting the manufacturing conditions, and the cost is reduced. We aimed to reduce the That is, a Ni film having a thickness of 02 to 1% of the material thickness when installed is provided on the bonding surface. For example, when manufacturing a clad steel plate from a 100 mm thick slab, plating is performed to a thickness of 200 to 1000 μm or Ni foil is charged.

The thickness of the Ni film is limited to 0.2% or more of the material thickness at the time of bonding.If it is less than 0.2%, carbon diffusion and movement cannot be completely prevented even when combined with the manufacturing conditions of the present invention described later. This is because it cannot be prevented and, for example, when finishing under a layer, the bonding boundary is not clear and the commercial value decreases. Moreover, if it exceeds 1%, poor adhesion between the core material and the laminate material tends to occur.

Being able to reduce the Ni film thickness is extremely advantageous when manufacturing from large steel ingots or large slabs.

That is, if the bonding area becomes large, it is difficult to manufacture a film with a constant thickness, and a locally thick film may lead to poor adhesion.

Next, the steel strip is wound in a temperature range of 600 to 500°C during hot rolling, but the control of this winding temperature is due to the carbon diffusion prevention effect of the N1 film provided on the joint surface and the large reduction rate during cold rolling. It is set to prevent cracks in the core material when

The coiling temperature and cold rolling rate of the hot rolled steel strip were varied to investigate the cold rolling rate that caused cracks in the core material, and the results were used in the second study.
Shown in the figure. The conditions for each display in FIG. 2 are as follows.

O mark: Cold rolling rate at which cracks begin to occur in the core material when the hot rolled steel strip is heat treated (750°C x 1 minute), but there is no decarburization of the high carbon steel at the joint.

・Mark: Cold rolling rate at which cracks begin to form in the core material when hot-rolled steel strip is heat treated (750°C x 1 minute), but there is decarburization with high carbon ≦4 at the joint.

×: Cold rolling rate that causes cracks in the core material when the hot-rolled collar is not heat-treated.

To prevent carbon diffusion from the core material to the cladding material, use Ni1f.
The larger the thickness of i, the more effective it is, but if the hot-rolling temperature exceeds 600°C, even if the thickness of the Ni film on the joint surface is about 2% of the material thickness, as shown in Figure 2. As shown in the figure, since the diffusion and movement of carbon cannot be prevented, the upper limit was set at 600°C.

If the hot-rolling coiling temperature is less than 500°C, even if the hot-rolled steel strip is heat-treated, the softening will not be sufficient, and as shown in Figure 2, cracks will occur in the high carbon steel at a cold rolling reduction of about 30%. , set the lower limit to 5
The temperature was 00°C.

Next, regarding the heat treatment of the hot rolled steel strip before cold rolling, the relationship between heating temperature and holding time is shown in FIG. The conditions for each display in FIG. 1 are as follows.

O mark: No cracks in the core material and no decarburization at the joints up to a cold rolling rate of 70%.

× mark: There is no crack in the core material during cold rolling, but decarburization occurs at the joint.

Δ mark: When cold rolling reaches 30 to 40%, cracks occur in the core material, but there is no decarburization at the joint.

In the present invention, from the results shown in FIG. 1, the coordinates A, B, , C, and D in FIG. 1 are applied to the hot rolled steel strip before cold rolling.

Heat treatment is performed at a heating temperature and holding time within the shaded range surrounded by E, F, G, and H. Note that the values of each coordinate are as follows.

Coordinates Heating temperature ('C) Holding time (minutes) A
700 3B
750 2C7501 D 800 1E
850 1F 800
2G 800
3H7503 Figure 1 shows that if the heating temperature and holding time of heat treatment are outside the lower limit, if the core material of the hot rolled steel strip is not sufficiently softened and the cold rolling rate is high, cracks will occur in the core material. It can be seen that when the upper limit of is exceeded, diffusion and movement of carbon occurs at the bonding surface. Therefore, in the present invention, the heating temperature and holding time are adjusted to the coordinates A, B, C, D, E, F in FIG.
,,G.

It was limited to the range surrounded by H.

Further, FIG. 3 shows the relationship among heating temperature, holding time, and cold rolling rate at which cracks begin to appear in the core material during cold rolling.

As described above, the present invention achieves carbon diffusion movement on the joint surface by combining the thickness of the Ni film on the joint surface, the coiling temperature of the steel strip during hot rolling, and the heat treatment of the hot rolled steel strip under appropriate conditions. This can prevent cracks in the core material during cold rolling.

In addition, Ac, which aims to achieve uniform refinement of conventional high carbon steel, is maintained at a temperature just below the transformation point for a long time,
The transformation point or Ac, a heat treatment method of heating to a temperature just above the transformation point and then slow cooling, or a method of quenching and tempering polished special strip steel in a continuous furnace, etc., are all different from the present invention in their purpose and configuration 1 operation. .

〔Example〕

Charcoal tension tool steel j] material SK3 as core material, stainless steel mSO34
10 as a laminating material, thickness 100 with a cladding ratio of 35%
A three-layer clad slab of mm was produced.

)'' A raw tool S1 2 on the surface of the stainless steel tsuba in contact with the material
After performing N1 plating with a thickness of 00 μm, it was assembled into a G cladding. The assembled slab was heated to 1200°C, then hot rolled into a 3-inch thick steel strip and wound into a coil at a temperature of 600-509°C. Next, this hot-rolled steel strip is passed through a continuous annealing pickling line.
Heat treatment at 00° C. for 2 minutes, shot peening and pickling were performed, followed by cold rolling to one thickness. As a result of investigating the clad cold-rolled steel sheet of this example of the present invention, it was confirmed that there was no decarburization in the core material at the joint surface and that there were no cracks in the core material.

On the other hand, for comparison, a three-layer clad slab of the same type was hot-rolled under the same conditions and wound into a coil at a temperature of 750 to 650°C. Although there were no cracks in the core material, carbon diffusion and movement occurred at the joint surface.
Similarly, no cracks occurred in the core material, but the joint surface 8, carbon diffusion and movement took place).

〔Effect of the invention〕

As is clear from the above embodiments, the present invention has a material thickness of 0.2 mm on the joint surface when manufacturing three-layer stainless clad steel.
A Ni film with a thickness of ~1% is provided, and the thickness is 600 ~ 50 by hot rolling.
By winding the coil in a temperature range of 0°C and then performing heat treatment under limited conditions to prevent the diffusion of carbon on the bonding surface and the occurrence of cracks in the core material during cold rolling, costs are significantly reduced compared to conventional methods. It also made it possible to manufacture stainless clad steel from large steel ingots and slabs.

[Brief explanation of the drawing]

Figure 1 is a relationship diagram showing the relationship between the heating degree and holding time during heat treatment of hot-rolled steel strips and cracks in the core material of cold-rolled steel strips and the presence or absence of decarburization at joints. Figure 3 shows the relationship between the coiling temperature and the cold rolling rate that causes cracks in the core material during cold rolling. FIG. 3 is a diagram showing the relationship with the cold rolling reduction that starts to occur.

Claims (1)

[Claims] (1) In a method for manufacturing three-layer stainless clad steel in which the core material is carbon tool steel SK1 to SK5 and the mating material is stainless steel, the thickness of the material after joining is 0.2 to 1
The process of providing a Ni film with a thickness of 6% and the coil winding temperature of 6%.
The following coordinates A, B, C, D, E, F, G, H in the drawing with the coordinate axes of the hot rolling process with a temperature range of 00 to 500 ° C, and the heating temperature and holding time before cold rolling, respectively. A method for producing stainless clad steel, comprising the steps of: heat-treating a hot-rolled steel strip at a heating temperature and holding time within the enclosed range. Coordinates Heating temperature (℃) Holding time (minutes) A 700 3 B 750 2 C 750 1 D 800 1 E 850 1 F 800 2 G 800 3 H 750 3