JPS591079A - Production of clad steel - Google Patents

Abstract

PURPOSE:To produce a clad steel having high quality at a low cost and with high efficiency, by heating and melt-sticking an Ni powder layer and a corrosion- or heat-resistant metallic powder layer placed superposedly on a base material. CONSTITUTION:For example, Ni powder is placed at a specified thickness on a low alloy steel material 1 to form an Ni powder layer 2. For example, stainless steel powder is placed at a specified thickness on the layer 2 to form a stainless steel powder layer 3. The layer 2 and the layer 3 are heated and melted by, for example, a high-frequency induction heating method so as to be welded by fusion to the base material, whereby the product of the stainless steel clad steel interposed with the layer 4 between the stainless steel layer 5, which is a cladding material, and the base material 1 is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing clad steel with improved quality and productivity.

In stainless clad steel sheets manufactured by rolling a base material of carbon steel or low alloy steel with, for example, stainless steel as a clad material, the C clad material in the base material is heated during heat treatment during the manufacturing process. There is a problem in that the quality of stainless clad steel sheets deteriorates due to the diffusion of As a countermeasure against this, in general, N
A method of interposing an i-layer at the interface to prevent the diffusion of C in the base material into the clad material and thereby prevent quality deterioration of the clad steel sheet has been used. Conventionally, the method of interposing a Ni layer between the base material and the cladding material is to apply Ni plating on the base material.
The common method was to layer cladding material on top of that. However, with the method of interposing the Ni layer with Ni plating as described above, the thickness of the Ni plating can only be about 50μ at maximum, and it is difficult to secure a sufficient thickness to prevent C diffusion. In the plating operation, it is difficult to obtain a uniform thickness distribution of the Ni layer, so thin portions inevitably occur, resulting in an insufficient effect of preventing diffusion of C in the base material into the cladding material.

In addition, the conventional manufacturing method for clad steel is to apply Ni plating on the base material in advance as described above, and then layer a clad material, such as stainless steel, either by overlaying one volume or by explosive bonding. It is customary to manufacture them by assembling them together and then, for example, hot-rolling them to bring them into close contact. In such conventional assembly-rolling manufacturing methods, the manufacturing process is complicated, as it takes time to assemble the clad material and the base material, and it also requires a process to process the product into the desired size and shape after hot rolling. Due to extremely low productivity, it was difficult to respond to orders with various specifications from customers. In other words, for example, in order to order various cladding steel plates with different thicknesses, it is necessary to prepare cladding steel plates with different thicknesses in advance, but due to low productivity, it is necessary to prepare the above preparations in advance. It takes a long time to prepare the product, and it also takes time to process it into the desired shape and dimensions once the preparation is complete, making it difficult to manufacture ordered products in a short period of time and making it impossible to meet delivery deadlines. This is a problem like this.

The object of the present invention is to solve the above-mentioned problems at once, and provide a method for manufacturing clad steel that can produce clad steel with excellent quality and with high productivity.

The present inventors have focused on the fact that various metal powders can be obtained at low cost due to metal spraying, which makes it easy to coat the surface of a base material with dissimilar metals, and the recent spread of equipment that can produce metal powder in large quantities. However, various experiments and research have been conducted in order to develop a manufacturing method that can produce clad steel at low cost and solve the above problems by effectively utilizing such thermal sprayed metals and metal powders as cladding materials. As a result, the following facts were discovered.

That is, a Ni layer is formed by placing Ni powder on a base material of carbon steel or low-alloy steel, and then, for example, stainless steel powder is placed on top of this to form a stainless steel layer. By heating and fusing two metal layers using, for example, a high-frequency induction heating method, stainless clad steel of the desired quality can be obtained much more easily than with the conventional assembly-rolling method, and the manufacturing process is simplified. is achieved. Furthermore, by appropriately adjusting the thickness and distribution of the Ni powder when placing it, a Ni intervening layer with an appropriate thickness and uniform distribution is formed, and this Ni layer transfers carbon from the base material to the cladding material.
Since diffusion can be reliably prevented, it is also possible to obtain stainless clad steel of superior quality compared to products made by conventional methods. If you use a method such as rolling to finish the product, the above Ni
The area required for placing the powder and stainless steel powder is small, which reduces the labor involved in placing the metal powder, and also enables mass production of stainless clad steel, further reducing manufacturing costs. discovered.

The present invention is based on such knowledge, and its gist is that N
i Form a Ni layer by thermal spraying or placing Ni powder, and further form the metal layer on the Ni layer by thermal spraying a corrosion-resistant and/or heat-resistant metal or placing the metal powder, and then A method for manufacturing clad steel, which is characterized in that a corrosion-resistant and/or heat-resistant metal layer is heated and fused, or if necessary, further heated and processed.

The method of the present invention will be explained in detail below based on the drawings.

An example of the method for producing clad steel according to the present invention is shown in the order of steps as follows.

1st step ↓ 2nd step The above-mentioned 1st to 3rd steps are steps showing the method for producing clad steel as set forth in claim 1 of the present invention, and steps 4c to 4th are steps as set forth in claim 2. This is a process showing the method for producing the described clad steel.

That is, in the first step, for example, a low alloy steel material (1) whose surface has been cleaned, as shown in the cross-sectional view of FIG.
For example, place Ni powder to a certain thickness to form a Ni powder layer (2).
form. Next, in the second step, as shown in FIG. For the formation of the Ni1 stainless steel powder layer, N
Instead of placing i powder and stainless steel powder, Ni thermal spraying and stainless steel thermal spraying may be used.

Next, in the third step, as shown in FIG. 1(/'3), the Ni powder layer (2) and the stainless steel powder layer (3) are heated and melted by, for example, a high frequency induction heating method and welded to the base material. Then, the Ni layer (4) is replaced with the clad stainless steel layer (
5) and the base metal (1) is a stainless clad steel product.

In the fourth step, the stainless clad steel obtained in the third step is further heated and processed by rolling, forging, pressing, etc.
As shown in FIG. 1), this is a process of finishing a stainless clad steel plate consisting of, for example, a base steel plate (6), a Ni plate (7), and a stainless steel plate (8).

As the clad material used in the method of the present invention, for example, SUS
Ferritic stainless steel such as 430.5US429.5US405, 5US316.5US304.5US
Austenitic stainless steel such as 301, Cr stainless steel, etc., and the type of steel is not particularly limited.
Depending on the use of the clad steel, it may be selected as appropriate from among those having either or both of corrosion resistance and heat resistance.

The above-mentioned high-frequency induction heating method is suitable as the heating method in the third step, but any heating method other than the above may be used as long as it can locally heat only the steel surface and fuse the metal powder layer. Any heating method may be used, and there are no particular limitations.

The manufacturing method in steps 1 to 3 above is a method of producing a product by directly welding the clad material to the base material, and is mainly used for products with a small surface area or products whose surface is not flat. This method is suitable for In addition, the manufacturing method of the first to fourth steps is a method in which the Ni powder and stainless steel powder placed on the base material are fused and then further hot rolled etc. are added to finish the product. Since the area for placing the stainless steel powder is small and mass production is possible, costs can be reduced compared to the methods of the first to third steps described above, and it is suitable for manufacturing mass-produced products.

As mentioned above, the method of the present invention is a simple process of placing Ni and corrosion-resistant and/or heat-resistant metal powders on a base material of carbon steel or low alloy steel and heating and melting them to produce a desired type of clad steel. It is also possible to mass-produce using hot rolling, etc. if necessary, making it extremely easy to respond to orders with various specifications from customers. Regarding the Ni layer interposed between the material and the base material, according to the method of the present invention, it is possible to form a uniformly distributed Ni layer with a desired thickness by adjusting the amount of Ni powder placed on the stainless clad steel. The diffusion of C in the base material into the cladding material can be reliably prevented, resulting in improved quality.

Next, the effects of the present invention will be explained based on Examples.Example 1 A hot rolled steel sheet having the components shown in Table 1 was descaled to make it a base material, and Ni powder (average particle size of approximately 6
8μ) so that it is 1 piece thick, and
A surface Ni layer is formed, and SUS 316I# stainless steel powder (average particle size approximately 55μ) is placed on the Ni layer to a thickness of 15TMn, and then the Ni layer and the stainless steel layer are heated by high frequency induction heating to melt them. In this way, sample material (2) of the present invention example was obtained. Further, the sample material (1) was further hot-rolled to obtain a sample material (2) of the present invention. For comparison, a hot-rolled steel plate similar to the above was coated with Ni coating (50μ thick) according to the conventional assembly-rolling method, and then a 15mm thick SUS plate was coated on top of it.
After stacking and assembling 316L stainless steel sheets, the sheets were hot-rolled to form a stainless steel clad steel sheet to obtain sample material (2) as a comparative example.

70 pieces of each test piece cut from the above sample materials ■～■
After heat treatment at 0°C for 20 hours, the thickness of the carburized layer formed on the clad material side was measured from the microstructure of the clad interface of each test piece. The results are shown in Table 2.

Table 2 As shown in Table 2, a carburized layer was observed in the cladding material in the comparative sample material ■ because the Ni layer was thin.
In the sample material (■) of the present invention example, almost no carburized layer was observed, and it was predicted that the method of the present invention would be more effective in improving the corrosion resistance of clad steel.

Example 2 With the same ingredients as shown in Table 1 above, 250 x 240
A slab with a width of 0 x 10,000 m + a length of n is used as the base material, and on one side of the descaling round, Ni powder (average particle size of about 68 μm) is applied to a thickness of 1 mm according to the method of the present invention in the same manner as in Example 1. A layer of SUS is formed on the Ni layer.
After forming a stainless steel layer by applying 316L stainless steel powder (average particle size approximately 55μ) to a thickness of 15 in the same manner, the Ni layer and the stainless steel layer are heated by high frequency induction heating to melt and form a matrix. This was then hot-rolled to a thickness of 20mm to form a product, which was used as the test material of the present invention.For comparison, welded the same material as above to one side of the base material slab. , according to the conventional assembly-rolling method, a 50μ thick Ni plating was applied, and a 151μ thick Ni plating was applied on top of that.
After assembling 111H SUS 316L stainless steel plates, they were hot rolled to a thickness of 920M and finished into a product, which was used as a comparative sample material.

The above two sample materials were subjected to intergranular corrosion tests and pitting potential tests to investigate their corrosion resistance.

The intergranular corrosion test was conducted based on the corrosion test method specified in JISGO575.

The pitting potential test was conducted by immersing the test piece in artificial seawater at 60°C and determining the state of pitting corrosion by measuring the potential using an SCE electrode.

The results of each of the above tests are summarized in Table 3.

In the upper table of Table 3, the ○ mark for intergranular corrosion test indicates that there is no intergranular cracking, Δ
The mark indicates a slight occurrence of grain boundary cracking.

As shown in Table 3, all of the test materials of the method of the present invention had no grain boundary cracks in the intergranular corrosion test, and showed extremely good results in the pitting potential test of 209 = vs 217 = v. It was shown that the method of the present invention has a remarkable effect on improving corrosion resistance compared to the conventional assembly-rolling method.

As is clear from the above description, the method for manufacturing clad steel of the present invention involves heating and fusing the Ni powder layer and the corrosion-resistant and/or heat-resistant metal powder layer placed on the base material, or further It can be carried out by a simple method of hot working, and high-quality clad steel can be manufactured at low cost and with high efficiency, so it is highly effective in improving the quality of clad steel and reducing costs.

[Brief explanation of drawings]

FIGS. 1(a) to 1(a) are cross-sectional views illustrating the manufacturing process of the method of the present invention. 1: steel material, 2: Ni powder layer, 3: stainless steel powder layer,
4: Ni layer, 5: stainless steel layer, 6: steel plate. 7: Ni plate, 8 Ni stainless steel plate 1st Figure 11! 1 1st Figure 421-

Claims (2)

[Claims] (1) Form a Ni layer on the base material carbon steel or low alloy steel by Ni thermal spraying or placing Ni powder, and then
After forming the metal layer by thermal spraying a corrosion-resistant and/or heat-resistant metal or placing the metal powder on the layer, the N
A method for manufacturing clad steel, which comprises heating and fusing the i-layer and the above-mentioned corrosion-resistant and heat-resistant metal layer. (2) Form a Ni layer on the base material of carbon steel or low alloy steel by spraying Ni or placing Ni powder, and then spraying a corrosion-resistant and/or heat-resistant metal or placing the metal powder on the Ni layer. After forming the metal layer, the Ni layer and the corrosion-resistant and/or heat-resistant metal layer are heated and fused, and then further heated and processed. Production method.