JPH02121785A - Manufacture of aluminum clad steel plate - Google Patents

Abstract

PURPOSE:To increase joining strength and to improve product yield by forming composition of Al-steel-steel-Al, fixing the tip in the longitudinal direction and then rolling the composition at the heating temperature above the specific temperature and below the Al melting temperature and at >=10% draft of Al for one pass. CONSTITUTION:An Al thermally sprayed coating is formed on the surface of a steel plate and the composition of Al-steel-steel-Al is assembled and a steel plate and an Al plate of the tip in the longitudinal direction of the composition are calked and fixed by rivets. Rolling is carried out at >=350 heating temperature and below the Al melting temperature and at >=10% draft of Al for one pass at least as rolling conditions. Since the Al thermally sprayed coating is formed on the surface of the steel plate, the steel plate surface is prevented from being oxidized for a period of time till being rolled with the Al plate. While the composition being assembled, heated and rolled, the need for special consideration to prevent the steel surface from being oxidized is eliminated and mass production can be carried out. In addition, the joining strength is increased and crosswise curvature of Al is slight and the product yield can be improved.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to the production of aluminum clad steel sheets, and more specifically, to manufacturing aluminum clad steel sheets with high bonding strength and good product yield using a rolling bonding method. It relates to a manufacturing method.

(Conventional technology and issues to be solved) The so-called aluminum clad steel plate, which is a steel plate clad with an aluminum plate,
It is being used in a variety of fields as a metal material with multiple functions such as mechanical properties, corrosion resistance, and electrical properties. Conventionally, it has been bonded by explosive crimping, which uses the explosive energy of explosives, or by rolling. Manufactured by rolling joining method etc.

However, the explosive crimping method has a high manufacturing cost and is not suitable for manufacturing clad steel sheets at low cost.

On the other hand, the rolling joining method is inexpensive and suitable for manufacturing rad steel plates.

Roll joining methods include a method in which a laminate and a steel plate are superimposed, heated, and hot rolled, and a method in which they are cold rolled without heating.

Generally, when manufacturing clad steel plates with a thickness of 8 mm or more by the rolling joining method, a hot rolling method is adopted, but when directly joining steel sheets and aluminum plates by hot rolling, the oxidation of the steel sheet It is necessary to try to prevent this. For example, Japanese Patent Application Laid-Open No. 58-47584 discloses that after forming a film layer of zinc or a zinc-based alloy on at least the mating surfaces of the steel plate and aluminum plate on the steel plate side by hot dipping or electroplating, , a method of joining the two by rolling has been proposed. However, in the case of this method, as is clear from the examples disclosed in the same publication,
Since the melting temperature of zinc is 419℃, the heating temperature is 30℃.
The temperature is as low as 0-350℃. Therefore, when rolling a clad steel plate with a thickness of 8 +++ m or more, a large degree of workability cannot be obtained, so heating in such a low temperature range may cause joint defects or cracks may occur in the aluminum plate during rolling.

In addition, a brittle alloy layer is formed in the plating layer, resulting in low bonding strength.Furthermore, with the conventional rolling bonding method, rolling causes lateral bending in the aluminum, resulting in a reduction in product yield. .

The present invention has been made in order to solve the problems in the prior art described above, and is an aluminum clad steel plate that has high bonding strength even when the plate thickness is 8 mm or more, has a high product yield, and has a good shape. The purpose of this invention is to provide a method for manufacturing the same at low cost.

(Means for Solving the Problems) In order to achieve the above object, the present inventors searched for a protective film that has a high anti-oxidation effect on steel sheets and does not form a harmful embrittlement layer, and in addition, We conducted extensive research to find manufacturing conditions that would provide high strength and would not cause horizontal bending of the aluminum plate.

As a result, an aluminum sprayed coating that is the same as that of the aluminum plate of the first laminated material is formed on the steel plate, and an aluminum plate with the same width or narrow width as the steel plate is stacked on the aluminum sprayed coating side. A composite with a four-layer structure or a two-layer structure of aluminum and steel is made, and when hot rolling this composite, the aluminum plate at the rear end of the composite is substantially restrained and hot rolled under predetermined conditions. It was discovered that by doing so, horizontal bending of aluminum can be prevented and aluminum and steel can be firmly crimped together, and the present invention has been made based on this finding.

That is, in the method for producing an aluminum clad steel sheet according to the present invention, two steel plates each having an aluminum sprayed coating formed on the surface of the IIl plate are laminated so that the sprayed coating side is the front and back surfaces, and the aluminum clad steel plate is laminated on the front and back surfaces of the IIl plate. Cleaned aluminum plates with the same width or narrow width as the steel plate are stacked to form a composite with a four-layer structure of aluminum-steel-steel-aluminum, or an aluminum thermal spray coating is formed on the surface of the steel plate, and then the same width as the steel plate is formed. Width or narrow cleaned aluminum plates are stacked to form a two-layer aluminum-steel composite.

The longitudinal end of the composite is heated after fixing the aluminum plate and the steel plate, and then when this composite is rolled, the longitudinal rear end of the composite is restrained, and the rolling conditions are: (1) heating temperature of 350°C or higher; , below the melting temperature of aluminum; (2) rolling is performed so that the rolling reduction of aluminum is 10% or more in at least one pass;

The present invention will be explained in more detail below.

(Function) First, the present invention is characterized in that a steel plate on which an aluminum sprayed coating is formed on the surface of the steel plate is used as the aluminum clad steel plate material.
In the case of a layered structure, a laminated steel plate is used in which two steel plates are laminated so that the thermal spray coating side is the front and back sides, and an aluminum plate is placed on the outside of this laminated steel plate. It is important to use a composite with a layered structure.

Furthermore, in the case of a two-layer structure, it is important to stack an aluminum plate on the thermal spray coating side to form a composite with a 2N structure.

This protects the new surface of the steel with an aluminum spray coating, which prevents oxidation of the steel plate until the aluminum and steel are crimped together. During rolling, this coating and the oxide film on the surface of the aluminum plate prevent plastic deformation. It is broken by the load (rolling load) and the new surfaces of the two are joined together, making crimping easier and helping to obtain an aluminum clad steel plate with good flatness.

Further, since the melting temperature of the aluminum spray coating is almost the same as the melting point of the aluminum plate, the heating temperature can be sufficiently high, making it possible to firmly bond aluminum and steel.

Furthermore, in the case of a four-layer structure, the reason why aluminum is placed on the outer layer is to suppress the amount of plastic deformation of the inner layer steel to a small extent and give large plastic deformation to the aluminum plate, resulting in the occurrence of warping after crimping. can be effectively suppressed.

Note that the steel plate or laminated steel plate may be made of any appropriate material and thickness depending on the desired composite function of the aluminum-clad steel plate.

As the aluminum plate, pure aluminum or an aluminum alloy of an appropriate composition and thickness can be used depending on the desired composite function.

Another feature of the present invention is that during hot rolling, the rear end of the composite in the longitudinal direction, that is, the aluminum plate at the rear end, is substantially rolled by side guides, pinch rolls, tension pads, etc. on the entry side of the rolling machine. The key point is that it has a composite structure that can be rolled while being restrained.

In aluminum-steel rolling, the steel undergoes almost no deformation, and only the aluminum undergoes deformation, so the difference in the thickness of the material steel plate in the width direction affects the amount of deformation at the width position of the aluminum plate.
This causes horizontal bending in aluminum after rolling. Measures to prevent this include making the thickness of the raw steel plate uniform and using a minus-crown rolling roll, but it is difficult to reliably prevent horizontal bending of aluminum with these measures alone.

On the other hand, when rolling a composite aluminum plate while restraining its rear end 1, for example, an aluminum plate that is wider than or the same width as the steel plate is joined to this aluminum plate, and the joined aluminum is rolled along the side guide. Rolling is not only to restrain the deviation of the aluminum plate in the width direction of the composite with the side guides, but also to apply backward tension to the aluminum plate, which eliminates the deviation in the width direction of the aluminum plate and ensures Can prevent horizontal bending of aluminum plates. Therefore, it is important to make the width of the aluminum plate of the rolling material equal to or narrower than the steel plate from the tip to the rear end in order to uniformly apply the rear tension from the rear end to the aluminum plate during rolling.

The aluminum plate at the longitudinal rear end of the composite can be restrained by pinch rolls, tension pads, etc. on the entry side of the rolling mill, or by side guides if the steel plate and aluminum plate are the same width. Alternatively, the aluminum plate can be restrained by joining an aluminum plate having a width wider than the steel plate or the same width and an appropriate length to the rear end of the aluminum plate, and sandwiching both sides of the joined aluminum plate with side guides. Of course, in the case of a composite where the width of the aluminum plate is narrower than that of the steel plate, when restraining it with a side guide, an aluminum plate that is wider than or the same width as the steel plate is joined to the rear end of the aluminum plate, and this joining It is best to restrain the aluminum plate by sandwiching both sides of the aluminum plate with side guides.

Note that the longitudinal end portion of the composite is fixed by caulking the steel plate and the aluminum plate with rivets or the like.

Next, it goes without saying that the heating temperature during rolling should be lower than the melting temperature of aluminum, but if it is lower than 350°C, a large rolling reduction will be required for aluminum-steel crimping, so the capacity of the rolling mill will be limited. Not only will this result in exceeding the limit, but also cracks may occur in the aluminum plate, which is undesirable. Therefore, a suitable heating temperature is in the range of 350°C or higher and lower than the melting temperature of aluminum.

Further, the rolling reduction ratio is a particularly important condition in the present invention, and it is necessary that the rolling reduction ratio of aluminum be 10% or more in at least one pass. This is because it is an indispensable element for completely collapsing the thin oxide film that has formed on the joint surface of aluminum and steel by utilizing the plastic flow of aluminum, and then immediately crimping the aluminum and steel. Rolling ratio is 10
If it is less than %, the bonding strength will be extremely reduced and should be avoided.

In addition, in the case of an aluminum-steel two-layer structure, it is possible to obtain an aluminum clad steel sheet with good flatness equivalent to that of the 4M structure by rolling with one warp mitigation measure (different circumferential speed rolling). It is possible. Of course, even if such measures are not taken, no uncrimped portions will occur.

Next, examples of the present invention will be shown.

(Example) A steel plate and an aluminum plate with the details shown below were prepared, an aluminum spray coating with a thickness of 50 to 300 μm was formed on the surface of the steel plate, and a composite was assembled under the conditions shown in Table 1. After fixing the steel plate and aluminum plate with rivets, the material was heated, sandwiched between side guides on the entry side of the rolling mill, and rolled along the side guides.

Details of steel plate and aluminum plate Material of steel plate: 5S41 Size (+o+a): 25t x 685mm x 5500 Q Material of aluminum plate: Industrial pure aluminum Size (mm): 8t x 6
25w x 5000 Q or 8t x 685w
500 (l Q) The obtained material was examined for horizontal bending of the aluminum, as well as the presence or absence of non-bonded parts using ultrasonic flaw detection (UST).The shear strength was also examined.The results are also listed in Table 1. .

The horizontal bending of the aluminum was determined by measuring the water system from the tip to the rear end of the width end of the aluminum part of the obtained aluminum clad steel plate, and measuring the maximum distance between the water system and the aluminum.

As is clear from Table 1, examples of the present invention Ha 1 to Nu4
In both cases, no non-bonded parts were observed, the bonding strength was as high as 5.0 kgf/llm2 or more, and the horizontal bending of the aluminum part was slight. In addition, the present invention example Nc 4
It has a two-layer structure of aluminum and steel.

Similar to the inventive example of the 4-layer structure, good characteristics were obtained.

On the other hand, in Comparative Example &5 in which the surface of the steel plate was subjected to hot-dip aluminization, the bonding strength was low. In Comparative Example Nα6, in which the surface of the steel plate was thermally sprayed with aluminum, but the heating temperature exceeded the upper limit of the range of the present invention, part of the aluminum was eroded during heating. In addition, in Comparative Example Nα7, the heating temperature did not reach the lower limit of the range of the present invention, and the entire surface was not bonded.
Moreover, cracks appeared in some of the aluminum. Comparative example N
α8 is.

The rolling reduction of the aluminum plate did not reach the lower limit of the range of the present invention, there were many non-bonded parts, and the shear strength was significantly lower than the value of the example of the present invention. Comparative example Nα9 is an example in which the width of the aluminum plate is wider than the steel plate from the tip to the rear end, and comparative example Nα10 is an example in which the width of the aluminum plate is narrower than the steel plate from the tip to the rear end, but at the rear end. This is an example in which no restraint treatment was applied to the aluminum parts, and large lateral bending occurred in the aluminum products obtained in all comparative examples.

[Margins below f] (Effects of the Invention) As detailed above, according to the present invention, since an aluminum spray coating is formed on the surface of the steel plate, the surface of the steel plate is not oxidized until it is crimped to the aluminum plate. You can prevent this from happening. Therefore, during composite assembly and heating,
No special consideration is required to prevent oxidation on the surface of the steel sheet during rolling, the manufacturing process is simplified, and continuous mass production is possible. Furthermore, since the assembly, heating, and rolling are performed under specific conditions, the bonding strength is high, and the horizontal bending of the aluminum is slight, so the product yield is excellent. In particular, the method according to the invention provides a plate thickness of 8III1
Suitable for manufacturing one or more thick aluminum clad steel plates.

Patent applicant: Kobe Steel, Ltd. Representative Patent Attorney Takashi Nakamura

Claims (4)

[Claims] (1) Two steel plates with an aluminum sprayed coating formed on the surface of the steel plates are stacked so that the sprayed coating side is the front and back sides, and on the front and back sides, cleaned aluminum with the same width or narrower width as the steel plate is placed. The plates are stacked to form a composite with a four-layer structure of aluminum-steel-steel-aluminum, and the tip of the composite in the longitudinal direction is heated after fixing the aluminum plate and the steel plate. While restraining the rear end, rolling conditions [
1) A method for producing an aluminum-clad steel sheet, which comprises rolling at a heating temperature of 350° C. or higher and lower than the melting temperature of aluminum; and [2] rolling at a rolling reduction of 10% or higher for aluminum in at least one pass. (2) Forming an aluminum spray coating on the surface of the steel plate,
On top of this, a cleaned aluminum plate of the same width or narrow width as the steel plate is stacked to form a composite with an aluminum-steel two-layer structure, and the longitudinal end of the composite is heated after fixing the aluminum plate and the steel plate. Then, when rolling this composite, while restraining the rear end in the longitudinal direction of the composite, the rolling conditions were [1] heating temperature was 350°C.
℃ or higher and lower than the melting temperature of aluminum; [2] A method for manufacturing an aluminum clad steel sheet, characterized in that rolling is performed so that the rolling reduction of aluminum is 10% or higher in at least one pass. (3) The longitudinal rear end of the composite is restrained by pinching the aluminum plate with either pinch rolls or tension pads on the entry side of the rolling machine.
The method described in. (4) To restrain the rear end of the composite in the longitudinal direction, an aluminum plate that is wider than or the same width as the steel plate is joined to the rear end of the aluminum plate, and the joined aluminum plate is placed in a side guide on the entry side of the rolling mill. 3. The method according to claim 1, wherein the material is sandwiched and rolled while being rolled along side guides.