JPH06126473A - Manufacture of aluminum clad steel sheet - Google Patents

Abstract

PURPOSE:To establish a low-cost and stable mass producing means for an aluminum clad steel sheet that has a sufficient joining strength and also good formability. CONSTITUTION:In the case of manufacturing the clad sheet by overlapping, rolling and pressing a carbon steel sheet and an aluminum (including aluminum alloy) sheet, the carbon steel sheet is heated to 170 deg. to 250 deg.C and while this steel sheet is overlapped with the aluminum sheet heated to 300 deg. to 500 deg.C to perform the joining and rolling in the temperature of the carbon steel sheet at least in 170 deg.C, the time during which the carbon steel sheet is in the state of >=170 deg.C is limited within 2 minutes to perform the joining and rolling. Or, after this joining and rolling, the press-contacting clad sheet is further applied with a heat treatment with a heating temperature of 250 deg. to 450 deg.C for a holding time of >=5 minutes.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an aluminum clad steel sheet which is a composite material of carbon steel and aluminum (including aluminum alloy).

[0002]

2. Description of the Related Art Aluminum / carbon steel clad plate, which has both the characteristics of "aluminum", which has good corrosion resistance and light weight, and "carbon steel", which has high strength and high formability and is inexpensive, has recently been used as a building material. Besides, it is also important as a material for reaction plates of linear motors, and its use is becoming more and more widespread, as its use is being considered as part of measures to reduce the weight of automobiles. .

By the way, such an aluminum clad steel plate in which carbon steel and aluminum are compounded is industrially called "cold" in which a heated and heated aluminum material plate is superposed on a carbon steel material plate at room temperature and bonded and rolled. It was generally manufactured by the "inter-rolling method".

However, in the above method in which only the aluminum material plate is heated and superposed on the carbon steel plate at room temperature and pressure-bonded, when the aluminum material plate is thin, for example, 1.5 mm or less, Even if the stacking is done just before the rolling mill, the temperature drop of the contact surfaces of both materials becomes large and it becomes impossible to achieve sufficient joining. There was a problem that the curing became large. In this way, work-hardened clad products are prone to "cracking" and "breaking" when they are subjected to forming processing such as "deep drawing" and "overhanging", so it must be said that they are not suitable for molding. .

It is possible to adjust the work-hardened material by softening and annealing it if it is a "single material".
In the case of an aluminum clad steel plate, since the melting point of aluminum is low, when the carbon steel is heated to a temperature at which it softens, the aluminum melts, and thus soft annealing is difficult to apply. In particular, in the case of joint rolling by the cold rolling method, the reduction ratio required for pressure bonding is very high, and the work hardening of the obtained product is much larger, so that it is not suitable as a forming material.

In view of the above, it is an object of the present invention to establish a low-cost and stable mass-production means of an aluminum clad steel sheet which has a sufficient joint strength and exhibits good formability. It was

[0007]

Means for Solving the Problems The inventors of the present invention have made extensive studies in order to achieve the above object, and have been able to obtain the following findings. a) In order to manufacture an aluminum clad steel sheet with high joint strength and less work hardening by the rolling method which is excellent in terms of mass productivity, keep the joint surface temperature of both carbon steel and aluminum material during joint rolling as high as possible. Is important, and it is necessary to raise not only the temperature of the aluminum material plate but also the temperature of the carbon steel material plate.

B) However, in the past, heating a carbon steel material plate in an air atmosphere causes a scale on the surface (joint surface), which leads to a decrease in bonding strength. It was thought that this was not the case, but even when the carbon steel sheet is heated to a temperature that enables "reduction of the rolling reduction" that leads to the reduction of work hardening and sufficient bonding strength is obtained, until it is rolled If the time during which the carbon steel sheet is kept at a high temperature above a specific temperature is limited for a short time, the scale growth is small even in the atmosphere, and the joining is not hindered.

The present invention has been completed after further studies based on the above findings and the like. "A carbon steel plate and an aluminum (including aluminum alloy) plate are superposed and rolled and pressure-bonded to produce a clad plate. When doing, 1 carbon steel plate
Heat to 70-250 ℃, this steel plate and 300-500 ℃
While the carbon steel sheet is superposed with the heated aluminum sheet and the joint rolling is carried out in a temperature state where the temperature of the carbon steel sheet does not fall below 170 ° C., the carbon steel sheet until heated and rolled is 1
The joining rolling is performed while limiting the time in the temperature state of 70 ° C. or more to 2 minutes or, after this joining rolling, the pressure temperature of the crimped clad plate is 250 to 450 ° C. and the holding time is 5 minutes. By performing the above heat treatment, it is possible to stably manufacture an aluminum clad steel sheet having high bonding strength and good formability ”.

Incidentally, FIG. 1 is a graph for explaining "an example of temperature transition of carbon steel sheet until joining rolling" according to the present invention.

[0011]

According to the method of the present invention, the carbon steel blank is heated to 170 to 250 ° C. prior to the joint rolling. If the heating temperature is lower than 170 ° C., the carbon steel having a temperature of 170 ° C. or higher during the joint rolling is heated. Since the temperature of the material plate cannot be secured, the temperature of the joint surface with the aluminum material plate is low, and the reduction rate required for bonding is extremely large, and the work hardening of the product clad material is remarkable and the desired formability is obtained. Cannot be secured. The upper limit of the heating temperature is set to 250 ° C., because the surface is rapidly oxidized at a temperature higher than 250 ° C.
The reason for this is that a sufficient amount of bonding strength cannot be obtained.

The "time during which the carbon steel sheet material is in a temperature state of 170 ° C. or more before being heated and rolled" is limited to 2 minutes or less because the high temperature state is a long time of more than 2 minutes. This is because if the temperature is maintained for a long time, surface oxidation proceeds and the scale grows to hinder the bonding.

On the other hand, the heating temperature of the aluminum material plate prior to the joining rolling is set to 300 to 500 ° C. If the heating temperature is less than 300 ° C., the rolling reduction necessary for joining also becomes high, and It should be avoided as it causes a large amount of work hardening and deteriorates the moldability of the product. Also, 500 ℃
If the aluminum material is heated to a temperature higher than 1, the material becomes too soft and difficult to handle, and the bondability deteriorates. Therefore, the upper limit of the heating temperature must be suppressed to 500 ° C.

For the aluminum clad steel sheet obtained by the joint rolling under the above conditions, 250 to 450 ° C.
It is preferable to carry out a heat treatment for 5 minutes or more. By this heat treatment, interdiffusion between aluminum and carbon steel is promoted and higher joint strength is exhibited.

In this case, the heating (heat treatment) temperature is 250 ° C.
If it is less than the above, the rate of mutual diffusion is low and the heat treatment takes too long. On the other hand, if heated to a temperature higher than 450 ° C., the mutual diffusion proceeds too much to form an intermetallic compound, and conversely decreases the bonding strength. Therefore, the heating temperature is 250-4
Although the temperature is set to 50 ° C., it is preferably adjusted to 300 to 400 ° C.

If the heating and holding (heat treatment) time in the above heat treatment is less than 5 minutes, sufficient interdiffusion cannot be achieved and the intended purpose cannot be achieved. Therefore, it is necessary to set it to 5 minutes or more. However, heat treatment for more than 90 minutes leads to deterioration of work efficiency, and mutual diffusion may proceed too much, leading to a decrease in bonding strength. Therefore, the heat retention time is preferably 5 to 90 minutes. .

Next, the present invention will be described more specifically by way of examples.

【Example】

<Example 1> First, a pure aluminum coil (equivalent to A1050) having a thickness of 1.2 mm and a width of 250 mm and a thickness of 0.3
A carbon steel coil (SPCC equivalent material) having a width of 230 mm and a width of 230 mm was prepared.

Next, using these materials, joint rolling was carried out in the processing line shown in FIG. 2 to carry out a production test of an aluminum clad steel plate. That is, in FIG. 2, the carbon steel plate 1 and the pure aluminum plate 2 are rewound and the polishing brush 3,
After the joint surface is roughened and activated by brushing with 3, the pure aluminum plate 2 is heated by the induction heating coil 4
On the other hand, the carbon steel plate 1 is heated by energizing the energization heating pinch rolls 5 and 6. continue,
The heated carbon steel plate 1 and the pure aluminum plate 2 are superposed on each other, bonded and rolled by a rolling mill 7, and then wound as an aluminum clad steel plate 8. The rolling conditions at this time were as shown in Table 1.

[0019]

[Table 1]

As is clear from the results shown in Table 1, when the joining rolling is performed according to the conditions specified in the present invention, an aluminum clad steel sheet having a sufficiently excellent joined state and good formability is obtained. However, when the joining and rolling conditions do not satisfy the conditions specified in the present invention (comparative example)
It can be seen that the performance of the obtained aluminum clad steel sheet is not sufficient. The "temperature transition pattern of carbon steel sheet until joining and rolling" according to the comparative example was classified and illustrated in FIGS. 3, 4 and 5, respectively.

<Example 2> Two kinds of aluminum clad steel sheets prepared in Example 1 (test numbers 5 and 14 in Table 1) were degreased and washed, and then heat treated under the conditions shown in Table 2. Was applied. Then, after the heat treatment, a torsion test was performed to investigate the bondability and formability of the aluminum clad steel plate.

In the torsion test, a test piece having a width of 5 mm and a length of 150 mm as shown in FIG. 6 (the plate thickness is as rolled) was sampled, and the gripped portions at both ends of 20 mm are shown in FIG. It was sandwiched by a chuck of a torsion tester and twisted 4 times, and then twisted back 8 times in the opposite direction.

Here, the evaluation points of the bondability and formability by the torsion test are as follows. Bonding Since peeling occurs when the bonding is weak, the bondability can be evaluated by the presence or absence of peeling. That is, the weaker the joint, the lesser the twisting rotation, the easier the peeling will be, even if the joint can withstand the twisting in one direction, the more likely it is to peel in the opposite direction. Therefore, if it can withstand twisting (4 times) and untwisting (8 times), the bondability is sufficiently high and it can withstand considerable processing. If the number of twists in formability increases, the elongation of the material also increases, so if work hardening is large and annealing is insufficient, rupture occurs even if peeling does not occur due to twisting. Therefore, the moldability can be evaluated by this.

Therefore, the best evaluation is "no peeling / breakage", and the next is "breakage", which has high bondability but slightly poor formability.
Therefore, "peel" with low bondability is the worst. The results of this investigation are shown in Table 2 together with the heat treatment conditions.

[0025]

[Table 2]

As is clear from the results shown in Table 2, according to the method of the present invention, an aluminum clad steel sheet excellent in bondability and formability can be obtained, whereas the heat treatment conditions satisfy the conditions specified in the present invention. Test number 29,3 not met
The intermetallic compound F which is brittle in the clad steel sheets related to 1, 32 and 33
Since e ₂ Al ₅ and Fe ₄ Al ₁₃ were generated at the interface, peeling occurred during the heat treatment.

[0027]

[Summary of Effects] As described above, according to the present invention, industrially useful effects such as stable mass production of aluminum clad steel plates having high joint strength and excellent formability can be obtained. Be done.

[Brief description of drawings]

FIG. 1 is a graph illustrating “an example of temperature transition of a carbon steel material sheet before joining and rolling” according to the present invention.

FIG. 2 is an explanatory diagram related to a production line of an aluminum clad steel plate used in an example.

FIG. 3 is a graph illustrating an example of “a temperature transition pattern of a carbon steel material sheet before joining and rolling” according to a comparative example.

FIG. 4 is a graph illustrating another example of the “temperature transition pattern of the carbon steel sheet until joining and rolling” according to the comparative example.

FIG. 5 is a graph illustrating still another example of the “temperature transition pattern of the carbon steel sheet until the joining and rolling” according to the comparative example.

FIG. 6 is an explanatory diagram of a torsion test piece.

FIG. 7 is an explanatory diagram of a torsion test by a torsion tester.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Carbon steel plate 2 Aluminum plate 3 Polishing brush 4 Induction heating coil 5 Current heating pinch roll 6 Current heating pinch roll 7 Rolling machine 8 Aluminum clad steel plate

Claims (2)

[Claims] 1. When a carbon steel plate and an aluminum plate are superposed and rolled and pressure-bonded to manufacture a clad plate, the carbon steel plate is heated to 170 to 250.degree.
While the carbon steel sheet is superposed with the aluminum sheet heated to 00 ° C. and the joint rolling is performed in a temperature state in which the temperature of the carbon steel sheet does not fall below 170 ° C., the temperature of the carbon steel sheet before heating to rolling is 170 ° C. or more. A method for producing an aluminum clad steel sheet, characterized in that the time in the state is limited to within 2 minutes. 2. When manufacturing a clad plate by laminating a carbon steel plate and an aluminum plate and rolling and pressing them, the carbon steel plate is heated to 170 to 250 ° C. and this steel plate and 300 to 5
While the carbon steel sheet is superposed with the aluminum sheet heated to 00 ° C. and the joint rolling is performed in a temperature state in which the temperature of the carbon steel sheet does not fall below 170 ° C., the temperature of the carbon steel sheet before heating to rolling is 170 ° C. or more. The aluminum is characterized in that after the bonding and rolling is performed while the time in the state is limited to 2 minutes or less, the pressure-bonded clad plate is subjected to heat treatment at a heating temperature of 250 to 450 ° C. and a holding time of 5 minutes or more. Manufacturing method of clad steel sheet.