JPH0677857B2 - Clad steel plate manufacturing method - Google Patents

Description

The present invention relates to a method for producing a clad steel plate.

Since carbon steel is inexpensive and has good mechanical, thermal, and electrical properties, it has long been used for a very wide range of applications. However, carbon steel has a fatal drawback that it rusts or corrodes in a short time when used as it is. On the other hand, stainless steel has significantly better corrosion resistance than carbon steel, so it solves the problems of corrosion and rust prevention, but other properties such as thermal conductivity are quite different from those of carbon steel. Moreover, it is not always easy to completely replace stainless steel. Furthermore, since stainless steel is considerably more expensive than carbon steel, it must be said that it is difficult in terms of resources and economy.

As a method for solving these problems, clad steel having a surface of stainless steel and a central portion of carbon steel is used. For the clad steel, a carbon steel that matches the target properties is used for the base metal, and by using environmentally compatible stainless steel on the surface, a material that has excellent corrosion resistance and that satisfies the target properties is obtained. Therefore, it is relatively widely used in chemical devices.

The present invention relates to a method for producing such a clad steel technically easily and inexpensively.

(Prior Art) There are roughly two types of methods for producing a clad steel sheet. That is, it is a so-called cast-in method in which compounding is performed at the molten steel level and a method of joining at the solid phase level.

A method of performing compounding at a molten steel level is, for example, a method in which carbon steel as a base material is installed in a mold and molten steel of a stainless steel as a mating material is poured into the molten steel to form a clad steel sheet by rolling. -151623, JP-A-57-134258
And JP-A-58-32544. This method
Although the joining itself is relatively easy, there are drawbacks that it is difficult to set the conditions of the subsequent rolling process depending on the combination, or even if the overall plate thickness is constant, the thickness of the laminated plate varies greatly.

Solid-state level joining methods include cold pressure welding methods, methods in which the mating surfaces are vacuumed by welding the end faces, and hot welding is performed. Various proposals have been made depending on gender. In addition, the joining surface by the method properly selected by the combination of the materials is good without any problems in practical use, but if it is attempted to simplify the joining method, it becomes impossible immediately and the joining property is considerably high. It is a method with severe conditions. For example, in the case of a clad steel plate of carbon steel and stainless steel, almost no cold joining can be expected, so that Japanese Patent Laid-Open Nos. 48-45465 and 54-54
-24260 and Japanese Patent Laid-Open No. 57-190792, most of them are joined together hot. The clad steel plate obtained by solid-phase bonding is a material that has practically no problems in that the thickness accuracy and bondability are good, and subsequent manufacturing processes can be applied. However, especially in the case of hot pressure welding, at least the mating surfaces need to be evacuated or an inert atmosphere is required, so the cost cannot be reduced, and it is not always easy to take advantage of the features of clad steel that is inexpensive. Not in a situation. Therefore, the stainless clad steel plate manufactured by such a method is only used for special applications such as high-grade pans, which make use of the corrosion resistance of stainless steel and the good thermal conductivity of carbon steel.

Further, for the purpose of facilitating the joining at the solid phase level, a method of welding the mating surfaces and then rolling is proposed, but the cost advantage has not been utilized yet.

In the case of solid phase bonding, for example, JP-A-55-48468
JP-A-57-109588, JP-A-57-112985 and JP-A-5
A method using an intermediate medium contacting material such as 7-192256 has been proposed. The role of the intermediate contact material in these inventions is
This is to promote diffusion into the base material composite material by melting the intermediate medium contact material. However, in these inventions as well, as described in the specification, it is necessary to block the atmosphere from the interface between the intermediate medium contact material and the base material or the composite material. For this reason, for example, Japanese Patent Laid-Open No. 57-109588 requires that the environment be a vacuum of 1 Torr or less, and Japanese Patent Laid-Open No. 57-112985 proposes to cover the interface with a flux.
Therefore, even if the bonding property can be improved by using the intermediate medium contact material, the cost cannot be reduced because the vacuum is still required for the work.

(Problems to be Solved by the Invention) A common drawback of the conventional methods described above is that the cost is inevitably high. It is presumed that the cause of this is that the casting method requires a lot of steps, and that the solid phase bonding method requires that the mating surfaces be evacuated.

The present invention aims at performing solid phase bonding in air to form a clad to reduce the cost. For this reason, an intermediate medium contact material that can greatly improve the bondability was used.

It has been recognized that solid phase bonding in atmospheric air is not successful because of the presence of oxides on the mating surfaces. The point of the present invention is to complete the technique of removing oxides at the interface and not generating oxides in bonding in the atmosphere.

(Means for Solving Problems) It is important for the present inventors to remove the atmosphere from the interface in order to prevent oxides from forming on the mating surfaces, and for that purpose, non-oxidizing substances other than the atmosphere are required. It was considered that the air layer filled with the resin and a slightly remaining air layer could be achieved by extruding the filling material. Based on this idea, as a result of various studies on non-oxidizing substances, it was found that it can be achieved by a low melting point substance such as molten metal. That is, since the mating surface is not a perfectly smooth surface in the strict sense, even if the intermediate medium contact material is inserted, if it is a solid, air will always remain even if simply mated. However, if the work of filling a liquid substance and extruding it is performed, even if a non-contact portion is formed on the mating surface and the air phase remains, it is possible to expel the air at the same time as the filling material. Examples of the intermediate medium contact material sandwiched between the mating surfaces include metallic copper and Ni—P alloy when stainless steel is used as a matrix material of carbon steel.

Based on the above idea, a new method for producing a clad steel plate has been established. That is, in the present invention, in the production of a clad steel plate whose base material is steel, a compound such as a metal or a metal salt having a lower melting point than the base material and the laminated plate is sandwiched between the base material and the laminated plate as an intermediate contact material, A method for producing a clad steel sheet, which comprises rolling at least one pass at a temperature equal to or higher than the melting point of the medium contact material and at a reduction ratio of 20% or more, and extruding and joining the melted intermediate medium contact material. A method for producing a clad steel sheet, which comprises using stainless steel as a medium contact material with metallic copper, rolling it at a temperature of 1050 ° C. or higher for one pass or more, and extruding the molten metallic copper for joining.

Next, the behavior of the clad material manufacturing process according to the present invention will be described with reference to FIG.

In the production of the clad material by the method of the present invention,
As shown in the drawing, first, a laminated plate 1 and a low melting point metal or the like 2 used as an intermediate medium contact material are stacked on a base material 3 in a sandwich form, and the ends are partially fixed by welding or the like. In this state, the intermediate medium contact material is heated to a temperature higher than the melting point of the intermediate medium contact material to melt the intermediate medium contact material.
Then, before the intermediate medium contact material solidifies, at least one pass of reduction is applied to extrude excess molten metal or the like from the end. As a result, a minimum amount of intermediate medium contact material sufficient to fill the unevenness of the surface remains on the mating surface, and the mating material without oxide and the base material are pressure-welded to the surface, so that both are easily bonded. It will be. Furthermore, when a reduction is applied, an extra intermediate medium contact material is extruded. As a result, the air layer slightly remaining at the interface is extruded simultaneously with the extruded intermediate medium contact material. Further, when the intermediate medium contact material is solidified, it is pressed down with the intermediate medium contact material sandwiched, but most of them are bonded as the area of the new surface of the mating material and the base material increases due to the reduction. In addition, when the low melting point metal used as an intermediate medium contact material can form a solid solution with the base material or the bonding material, the low melting point metal left slightly at the interface is either the base material or the bonding material, or both. As a solid solution, it will not exist as a simple substance and will be bonded more firmly.

Next, the limiting conditions of the present invention will be described.

Since the intermediate medium contact material needs to be melted at the interface between the solid phase base material and the laminated material, it is limited to be lower than the melting point of the base material or the laminated material.

In order to extrude the surplus intermediate medium contact material from the end portion by the reduction, the intermediate medium contact material needs to be melted, so that the reduction is limited before the intermediate medium contact material is solidified.

This reduction can be achieved with just one pass, and 2
Although there is no obstacle even if the number of passes is greater than or equal to the number of passes, it is not possible to obtain a sufficient quality as a clad steel even if they are not joined or if they are joined unless they are added.

Further, if the reduction rate is less than 20%, the extrusion of the intermediate contact material is insufficient and the removal of the residual air layer is incomplete, so the reduction was limited to 20% or more.

When the laminated material is stainless steel, metallic copper is suitable for the intermediate medium contact material, but since it is necessary to reduce the temperature at 1050 ° C or higher in order to extrude the molten copper, at least one pass or more is required. The reduction was limited to 1050 ° C or higher.

(Operation) As described above, it has become possible to manufacture clad steel without using vacuum. By eliminating the need for a vacuum, expensive equipment such as vacuum pumps and vacuum tanks is no longer required, and the process of making a vacuum is eliminated, and since the work can be performed in an atmospheric environment, the manufacturing is significantly simplified. Become.

Further, the clad steel according to the present invention has no difference in quality from the clad steel produced by utilizing the vacuum of the conventional method, and no non-bonded portion was observed at the interface. When stainless clad steel was produced using metallic copper as an intermediate contact material, the Cu content near the interface increased, and it was presumed that Cu was solid-solved in both of the base metal composites and diffused. However, no deterioration of the quality of the clad steel was observed, including the bondability of the interface.

INDUSTRIAL APPLICABILITY The present invention is suitable for producing a clad steel using carbon steel as a base material and stainless steel as a bonding material, and Cu as an intermediate medium contact material.
Or Ni-P alloy can be used. However, the method of the present invention can be easily applied by appropriately selecting the intermediate medium contact material even if the joining material is another steel or metal alloy.

(Example) A 3.9 mm SUS304 hot-rolled and annealed steel sheet as a bonding material, a 0.7 mm-thick copper sheet having a purity of 99.9% or more as an intermediate contact material, and a 120 mm thick containing 0.01% C as a base material Carbon steel slabs were stacked in a sandwich shape, and about half of the four sides were welded and fixed. Surface roughness of these materials (Hma
x) was 5 μm or less and mechanically finished before assembling.
Then, it was heated to 1150 ° C., a single pass of 23% reduction was performed at 1090 ° C., and then rolled between 1030 ° C. and 770 ° C. until the total plate thickness became 4 mm. As a result, molten metallic copper was extruded from the portion not welded and fixed in the first pass. However, rolling was completed without peeling. The produced clad steel had no change in the bondability of the interface, the quality of the clad steel, and the mechanical properties of the good-tolerance base material of the laminated material.

As a comparison, when rolling was performed in the same manner as above without using an intermediate medium contact material, the part that was not welded and fixed peeled off in the first pass and completely peeled off in the third pass, making it impossible to produce clad steel. It was

(Effect of the Invention) According to the present invention, it becomes possible to manufacture a clad steel without physically creating a vacuum. As a result, the production of clad steel is technically easy and the cost is low, so only the necessary parts can be used by clad using an expensive composite material. It's a big one.

[Brief description of drawings]

FIG. 1 is a view for explaining the assembling of a raw material before rolling for producing a clad steel by the method of the present invention.

Claims (2)

[Claims] 1. In the production of a clad steel plate whose base material is steel, a compound such as a metal or a metal salt having a melting point lower than that of the base material and the laminated plate is sandwiched between the base material and the laminated plate as an intermediate medium contact material to form an intermediate medium. A clad steel sheet characterized by being rolled at least one pass at a temperature not lower than the melting point of the contact material and at a reduction ratio of not less than 20%, and extruding and joining the molten intermediate medium contact material together with the air present between the base material and the laminated plate. Production method 2. The method for producing a clad steel sheet according to claim 1, wherein stainless steel is used as the bonding material, and metallic copper is used as the intermediate medium contact material, and the material is rolled for one or more passes at a temperature of 1050 ° C. or higher.