JPH0686024B2 - Aluminum clad steel sheet manufacturing method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing an aluminum clad steel sheet by a hot rolling joining method.

(Prior Art and Problems to be Solved) A so-called aluminum clad steel plate in which a steel plate is clad with an aluminum plate is being used in various fields as a metal material having a composite function such as mechanical properties, corrosion resistance, and electrical properties. Conventionally, it is manufactured by an explosive pressure bonding method of bonding by utilizing explosive energy of explosives or a rolling bonding method of pressure bonding by rolling.

However, the explosive pressure bonding method has a high manufacturing cost and is not suitable for manufacturing an inexpensive clad steel plate.

On the other hand, the rolling joining method is suitable for the production of inexpensive clad steel sheets, and the method of applying diffusion annealing after cold-welding the laminated material and the base material with a rolling roll, or hot rolling after heating both metals The method is the mainstream.

However, in the former cold rolling joining method, large reduction of joining is required, and there is a restriction on rolling ability. On the other hand, the latter hot-rolling joining method has the advantage that the rolling reduction during rolling can be significantly reduced compared to cold rolling, but since an oxide film is easily formed at the joining interface, the joining strength is reduced. Tend to occur.

In the latter hot rolling joining method, when stainless steel is used as the base material, the surface property (passive film) peculiar to stainless steel is taken into consideration and pure aluminum is previously spray-coated on the stainless steel side. There is also a method (Japanese Patent Application Laid-Open No. 1-266981) in which an assembling material of the steel and the laminated material is heated and then hot rolled.
However, even if the surface to be joined on the stainless steel side is spray-coated in advance, not only the oxidation of the surface to be joined cannot be completely prevented, but also the aluminum plate and the steel sheet are directly rolled as they are due to the interposition of the sprayed layer. It is difficult to obtain high bonding strength because metal bonding cannot be performed and bonding is mainly mechanical bonding. Therefore, there is a problem in terms of cost, such as further diffusion annealing is required to increase the bonding strength.

An object of the present invention is to solve the above problems associated with the latter hot rolling joining method, and to provide a method capable of inexpensively producing an aluminum clad steel sheet that has good joining properties and can be imparted with high shear strength. Is.

(Means for Solving the Problem) In order to achieve the above object, the inventors of the present invention have conducted extensive research to find manufacturing conditions capable of imparting good bonding characteristics, and as a result, found the manufacturing method of the present invention. It was.

That is, the present invention, aluminum or aluminum alloy as a composite material, in producing a clad steel plate having a carbon steel or a low alloy steel as a base material, a composite in which the direct bonding material is laminated on the joining scheduled surface of the base material, After heating the surface to be joined to over 150 ° C to 350 ° C or less, make sure that the total reduction rate R (%) of the laminated material part satisfies the relation of R ≧ -0.2T + 90 depending on the temperature T (° C). The gist of the invention is to provide a method for producing an aluminum clad steel sheet, which comprises rolling the steel sheet under a condition that a rolling finish temperature is 150 ° C. or higher, together with rolling reduction.

The present invention will be described in more detail below.

(Operation) The most characteristic point of the present invention is to keep the surfaces to be joined clean just before joining in order to obtain good joining properties by high-performance ultrasonic flaw detection and high shear strength. The point is that the reduction of the reduction ratio necessary for metal-bonding the steel is performed, and further, the strength of the composite material portion near the bonding interface is increased by rolling.

(I) As a method for keeping the planned joining surface clean, after cleaning the base material steel surface by polishing or the like, the temperature of the planned joining surface is 350 ° C or less in order to suppress the oxidation of the base material steel during heating. I found that it was effective. If the temperature exceeds 350 ° C., the oxidation becomes remarkable at the joint interface, and even if it is rolled at a large reduction rate, the oxide film remains continuously without being broken, which adversely affects the joint strength, which is not desirable.

(Ii) In order to increase the strength of the laminated material portion near the bonding interface,
It is effective to perform rolling in a temperature range lower than the softening / annealing temperature of aluminum or an aluminum alloy, which is lower than 350 to 400 ° C., so as to impart a working strain to the laminated material.

From both viewpoints (i) and (ii), the temperature reached by the heating on the planned joining surface is limited to 350 ° C. or less. However, if the temperature to reach the planned joining surface is 150 ° C. or less, oxidation of the base steel can be prevented, but sound joining properties cannot be obtained by rolling, which is not desirable.

Therefore, the temperature to be reached on the joint surface due to heating is 150
Over 350 ℃ and below.

Note that this heating may be performed in the air, under vacuum, or in a reducing or inert atmosphere. In the case of the heating by the latter mode, oxidation of the surfaces to be bonded is suppressed as compared with the case of in the air, so that the bondability is improved and a higher shear strength can be obtained.

(Iii) It is necessary to destroy the oxide film on the joining surfaces of the respective metals and to eliminate the microvoids at the joining interface in order to metallically bond the joining material and the base material.
That is, the laminated material is directly laminated on the joining surface of the base steel, but even if the joining surfaces of both metals are heated to the above temperature of 150 to 350 ° C., it is impossible to completely prevent oxidation on the high temperature side. It cannot be done, and a thin oxide film is formed. However, by selecting a predetermined rolling reduction during rolling, it is possible to destroy the oxide film to this extent, give a new surface, and eliminate microvoids at the interface to be joined.

Here is an example of a basic experiment. First, after grinder polishing to No. 80, SS41 (base material steel) whose surface was cleaned by wire brushing was directly laminated with 8mm thick A1050P (aluminum composite material) to make a two-layer composite, and various Was heated to the temperature of 1, and 1-pass rolling was performed at various reduction ratios. Ultrasonic testing (JI
S G0601) and the bondability was evaluated by observing the microstructure of the bond interface. Here, in a metal-metal combination in which the high temperature resistance of the laminated material is significantly different from that of the base material steel, focusing on the fact that the amount of deformation of the laminated material with the smaller deformation resistance greatly affects the bondability, Using the rolling reduction as an index, the relationship between the bondability and the ultimate temperature of the joining surface due to the heating temperature and the rolling reduction in the laminated material part was obtained. The results are shown in FIG.

According to FIG. 1, in order to obtain a sound bondability, according to the temperature of the planned joining surface in the range (150 to 350 ° C.) shown above,
The following relational expression R ≧ -0.2T + 90 where R: total reduction of the laminated material (%) T: reduction necessary to satisfy the ultimate temperature (° C) of the surface to be joined by heating I know there is.

However, in the low-pressure ratio region (the lower left side of R = -0.2T + 90 in the figure) at a low temperature that does not satisfy the above relational expression, even if it is determined to be a bond in the ultrasonic flaw detection test, oxides that are continuous at the bond interface And micro voids remain, and further non-bonded portions are generated, which is not desirable.

Further, at a rolling finish temperature of less than 150 ° C, it becomes difficult to secure sound weldability by metal joining between the laminated material and the base material steel in the as-rolled state.
It must be 0 ° C or higher.

There are no particular restrictions on other manufacturing conditions, such as the materials and dimensions of the aluminum or aluminum alloy composite material and the base materials, carbon steel and low alloy steel, and the laminating mode (one side or both sides).

The method of coating the steel sheet with pure aluminum in advance by thermal spraying or the like is not included in the present invention. The reason is that, in the method of the present invention, an aluminum plate or an aluminum alloy plate and a carbon steel plate or a low alloy steel plate are directly opposed to each other without interposing a coating material, and the assembly materials are opposed to each other. From the viewpoint of suppressing softening of the laminated material (adding processing strain), the heating temperature of the laminated material is set to 350 ° C. or lower, and
Since both materials can be directly metal-bonded by rolling in the rolling ratio range of the laminated material portion shown in the figure, a clad steel sheet having a high shear strength equivalent to that of the laminated material can be obtained. This is because the interposition of the coating material also hinders metal bonding.

Further, in the present invention, carbon steel and low alloy steel are targeted as the base steel, but stainless steel belonging to high alloy steel is not targeted. Since stainless steel has a strong passivation film on the surface at the stage of material and is different from carbon steel and low alloy steel having a black skin that is easily broken on the surface, this surface property causes the method of the present invention. In some cases, it is difficult to prevent the formation of a passive film and destroy it, and diffusion annealing or the like is required after rolling to increase the bonding strength, which is not economical.

Next, examples of the present invention will be described.

(Example) An aluminum plate and a carbon steel plate having the specifications shown below were prepared, and after the aluminum plate surface was grinder-polished to No. 80, a composite was directly placed on one surface of the steel plate cleaned by performing wire brushing to produce a composite. The material was heated under the conditions shown in Table 1 and rolled.

Details of carbon steel plate and aluminum plate Carbon steel plate material: SS41 〃 Dimensions (mm): 22t x 340w x 2500l Aluminum plate: A1050P, A1100P 〃 Dimensions (mm): 8t x 340w x 2500l Ultrasonic flaw detection on the obtained material The bondability and the shear strength of the bonding interface were examined by the test (JIS G0601). The results are also shown in Table 1.

In Table 1, Comparative Example No. 3 has a total rolling reduction R of the laminated material portion.
Satisfies (-0.2T + 90) or more, but the temperature reached on the planned joining surface by heating exceeds 350 ° C.
Is an example in which the temperature reached on the joining surface due to heating is 350 ° C or less, but the total reduction ratio R in the laminated material part is below (-0.2T + 90). In any case, the bondability by ultrasonic flaw detection is good. However, the shear strength is low.

Comparative Example No. 5 was a case where the rolling finish temperature was lower than 150 ° C., and a non-bonded portion was generated.

On the other hand, in each of the examples of the present invention, a non-bonded portion is not generated and the shear strength is higher than that of the comparative example.
When the microstructure of the bonded interface in the materials of the examples of the present invention was observed, no microvoids were found.

(Effect of the invention) As described in detail above, according to the present invention, it is possible to impart good bondability and high shear strength in the production of an aluminum clad steel sheet by the hot rolling bonding method,
Moreover, the manufacturing cost is low.

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between the bondability, the ultimate temperature of the surface to be bonded due to heating, and the rolling reduction of the laminated material portion.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-1-266981 (JP, A) JP-A-63-303687 (JP, A) JP-A-63-157774 (JP, A)

Claims (2)

[Claims] 1. When manufacturing a clad steel plate using aluminum or an aluminum alloy as a composite material and carbon steel or a low alloy steel as a base material, a composite obtained by directly laminating a composite material on the joining surface of the base material is joined. After heating the planned surface to over 150 ℃ to 350 ℃ or less, the total rolling reduction R
(%) Is rolled according to the temperature T (° C) so as to satisfy the relation of R ≧ -0.2T + 90, and is rolled under the condition that the rolling finish temperature is 150 ° C or higher. Steel plate manufacturing method. 2. The method according to claim 1, wherein the surfaces to be joined of the composite are heated in a vacuum, a reducing atmosphere or an inert atmosphere.