JPH04339579A - Production of steel sheet/aluminum clad material - Google Patents

Abstract

PURPOSE:To provide the clad material which is free from harmful intermetallic compds. and oxides at the joint boundary and has good workability. CONSTITUTION:A galvanized steel sheet and aluminum are rolled at 10 to 30% rolling reduction margin of the thickness of the aluminum on the inlet side in a heating time of >=2 minutes and within 50 minutes at >=470 deg.C and <=530 deg.C in the process for production of cladding the aluminum or aluminum alloy by rolling on the galvanized steel sheet.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a steel plate/aluminum clad material having good cold workability.

0002

BACKGROUND OF THE INVENTION At present, ordinary steel/aluminum clad materials have already been commercialized. These materials are lighter and have better thermal conductivity than ordinary steel of the same thickness, and are used in food containers such as pots and automobile exterior panels. Most of these are manufactured by applying diffusion annealing after intense cold compression. Due to this strong reduction, ordinary steel is reduced by about 20 to 30%, and aluminum is reduced by about 60%. Aluminum is annealed through subsequent diffusion annealing and its workability is restored, but ordinary steel is hardly annealed and cannot be made with good cold workability. There is also a method of manufacturing ordinary steel/aluminum cladding in a warm manner, but it requires rolling in a non-oxidizing atmosphere in order to obtain a strong bond, resulting in a very high cost.

[0003] JP-A-58-47584 discloses rolling bonding of aluminum onto a coating layer of a zinc-based alloy. In the method shown in this example, bonding is performed by applying a reduction of about 50% at 350° C., which is below the melting point of zinc. This method is superior in that clad rolling can be carried out in a warm oxidizing atmosphere and the cost is not very high, but since the rolling reduction is large, work hardening of the steel is inevitable. Therefore, it has little advantage in terms of cold workability compared to a clad made by cold joining steel and aluminum.

0004

[Problems to be Solved by the Invention] In the prior art, it is difficult to join steel plates/aluminum clad materials without work hardening. The present invention provides a method for manufacturing steel/aluminum clad materials that obtains high bonding strength by clad rolling with a reduced rolling reduction of the steel sheet in order to obtain lightweight clad steel sheets with good cold workability at low cost. .

[0005]

[Means for Solving the Problems] The gist of the present invention is to provide a manufacturing method for cladding a galvanized steel sheet with aluminum or an aluminum-based alloy by rolling.
Heating at 30°C or less and for a time within the ranges a, b, c, and d in Figure 1, and the reduction rate of aluminum is 10% to 30%.
A method of manufacturing a steel plate/aluminum clad material, which comprises rolling.

[0006]

[Operation] Figure 1 shows the range of heating conditions during clad rolling. The melting point of zinc is about 419°C. Above this temperature, zinc will melt, but as long as the surface of the iron is coated even in the molten state, the iron will not be oxidized at this stage. 470 from melting point
Although the zinc is molten up to ℃, it has a high viscosity and is not squeezed out even when rolled, leaving molten zinc at the interface, similar to the presence of lubricating oil, and not being joined. When heated for a longer time than the shaded areas a, b, c, and d in Figure 1 at a temperature of 470°C or higher and 550°C or lower, the plated zinc melts, iron diffuses into it, and an iron-zinc intermetallic compound is formed. occurs. This intermetallic compound causes peeling after clad rolling. If heated above 550°C, the rigidity of the aluminum alloy will become insufficient, making it impossible to obtain the pressure necessary for joining, and the diffusion of iron into the zinc will become extremely active, causing molten zinc to quickly form between the iron and zinc metals. The bond is not strong due to the formation of compounds. When heated for a shorter time than the shaded range at a temperature of 470° C. or higher and 550° C. or lower, a large amount of highly viscous zinc that is insufficiently melted remains, so that almost no bonding occurs.

One of the features of the present invention is that zinc is melted and rolled while squeezing out the molten zinc before iron-zinc intermetallic compounds are formed. When rolled in this way, the iron and aluminum are sealed by molten zinc and come into direct contact without being exposed to air. This prevents iron oxidation from occurring during rolling. This makes it possible to reduce the rolling reduction required for bonding to about 10% of the Al plate thickness. Note that the remaining zinc contributes to strong bonding if it is not alloyed with iron.

FIG. 2 shows the relationship between the rolling reduction of a galvanized steel sheet and the uniform elongation of the clad material with respect to the rolling reduction of aluminum. Due to the above mechanism, a rolling reduction ratio of 10% or more is required due to changes in the Al plate thickness. The rolling reduction rate is 10 to 30 depending on the change in Al plate thickness.
%, even though the reduction ratio of the galvanized steel sheet is as small as 5% or less, the galvanized steel sheet is firmly bonded to the aluminum, and the uniform elongation of the obtained cladding material is as high as about 30%. When the rolling reduction ratio in terms of Al plate thickness becomes 30% or more, the rolling reduction ratio of the galvanized steel sheet increases, and the uniform elongation of the cladding material decreases accordingly.

[0009]

[Example] A rolling experiment was conducted within the range shown in the figure using hot-dip galvanized steel sheets with a thickness of 0.6 mm and a plating thickness of 20 μm as the outer sides and 3 mm thick industrial pure aluminum A1050 on the inside. Despite being heated above the melting point of zinc under the conditions of heating to 475°C, 500°C, and 525°C,
The bonding strength was strong. Under these conditions, no peeling occurred in the rolled sample in a 90° bending and 90° bending test with a punch radius of 10 mm. . When a tensile test was conducted, a clad steel plate with uniform elongation of about 30% and good workability was obtained under conditions within this range. The rolling reduction rate in this rolling is approximately 5% for the upper and lower steel plates and approximately 25% for the aluminum inside.

0010

According to the present invention, it is possible to obtain an aluminum clad steel sheet at a relatively low cost, which is free from harmful intermetallic compounds and oxides at the bonding interface and has good cold workability.

[Brief explanation of drawings]

FIG. 1 is a chart of heating conditions during clad rolling.

FIG. 2 is a chart showing the relationship between the rolling reduction rate of galvanized steel sheet, the rolling reduction rate of aluminum, and the uniform elongation of cladding material.

Claims (1)

[Claims] Claim 1: A manufacturing method in which a galvanized steel sheet is clad with aluminum or an aluminum-based alloy by rolling, in which the galvanized steel sheet and aluminum are clad with 47
0°C or more and 530°C or less, and a, b, c, d in Figure 1
Heating for a time within the range of 10 at a rolling reduction rate of aluminum
A method for manufacturing a steel plate/aluminum clad material, which comprises rolling up to 30%.