JPS6167581A - Manufacture of aluminum covered steel sheet - Google Patents

Abstract

PURPOSE:To improve the workability of an Al covered steel but by making a zinc base metal or a tin base metal adhere in advance to only an Al plate or both the Al plate and a steel sheet on the joint surface of both the plates, and executing the pressure welding. CONSTITUTION:An Al plate is plated by substituting zinc or tin and Al by an alkaline zinc water solution or an alkaline tin water solution, and a zine base metal or a tin base metal is made to adhere to the Al plate. Subsequently, at a surface temperature of 50-300 deg.C, these Al plate and steel sheet are welded by pressure and joined by a reduction rate of about <=10%. In this case, the zinc base metal or the tin base metal can be made to adhere in advance to only the Al plate. According to this method, the metal which has been made to adhere to the Al plate or both the Al plate and the steel sheet forms a diffusion layer at a low temperature, therefore, a large joint strength is obtained by a low reduction rate. Also, owing to a low rolling reduction joint, softening becomes unnecessary, and the cover is not peeled off. Accordingly, the workability is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for manufacturing aluminum-coated steel sheets.

Conventional technology Aluminum-coated steel sheets have been developed, for example, in Japanese Patent Application Laid-open No. 58-1.
It is manufactured by a so-called cold pressure welding method as disclosed in Japanese Patent No. 41882 and the like.

Problems to be Solved by the Invention However, in this cold welding method, the pressure ratio of the steel plate is several 1.
Since it becomes 0% or more, it is necessary to soften the steel plate at a temperature of 500 to 600°C after pressure welding. However, at this temperature, iron and aluminum form a thick alloy layer, and such thick alloy layers are usually extremely brittle.
When processing an aluminum-coated steel sheet with a thick alloy layer that is likely to peel off during processing, the coating will separate, so such surface-treated steel sheets are unsuitable for processing, and are not suitable for use as surface-treated steel sheets. will be restricted. That is, aluminum-coated steel sheets manufactured by the conventional cold pressure welding method have their own limitations in their uses.

Means for Solving the Problems The present inventors have conducted various studies in order to solve the problems of the prior art. By attaching a predetermined amount of zinc-based metal or tin-based metal to the joint surfaces of both the side and the steel plate side, it becomes possible to join the aluminum plate and the steel plate even if the rolling reduction of the steel plate is 10% or less. Along with this, we have developed a manufacturing method that has the excellent effect of omitting softening annealing after pressure welding.

That is, the present invention involves bonding an aluminum plate and a steel plate to each other to produce an aluminum-coated steel plate.
Or, after adhering a zinc-based metal or a 5i-based metal to the joint surfaces of both the aluminum plate and the steel plate,
This is a method for manufacturing an aluminum coated steel plate, which is characterized by press-welding these aluminum plates and steel plates.

action The present invention will be explained in detail below.

First, the steel plate to which the present invention is directed refers to a steel plate made of ordinary mild steel, structural steel, low-alloy or high-alloy high-strength steel, stainless steel, etc., and has a thickness suitable for normal use.

Further, the aluminum plate refers to a metal plate whose main component is A9, and which has a thickness suitable for normal use.

Next, the main point of the present invention is to attach zinc-based metal or tin-based metal to the joint surfaces of aluminum plates or aluminum plates and steel plates, respectively, and then connect these aluminum plates and steel plates. It is about joining. The l111 lead-based metal referred to here refers to a metal or alloy whose main component is metal Zn, with subcomponents such as Fe, Mg,
It can contain one or more metals such as Ni and Sn. Furthermore, the term "tin-based metal" refers to a metal or alloy whose main component is metal Sn, and which can contain Pb and Zn as subcomponents.

Next, the reason why it is necessary to attach a zinc-based metal or a tin-based metal in advance to the press-welded joint surface of an aluminum plate and a steel plate will be described.

In order to join two types of metal plates by pressing down, it is necessary to form an extremely thin diffusion layer at the joint. The same applies when joining an aluminum plate and a steel plate. However, since aluminum has a dense oxide layer on its surface,
A diffusion layer cannot be formed with iron at a low rolling reduction rate.

However, if the metal that forms the diffusion layer adheres to the aluminum plate and the steel plate at the temperature during pressure welding, the aluminum plate and the steel plate can be joined at a low rolling reduction ratio.

Zn and Sn have a high diffusion rate at room temperature, and if metals containing these metals as main components are attached to steel plates and aluminum plates, it becomes possible to pressure-weld the aluminum plate and the steel plate with a low rolling reduction rate. .

Here, the reason why the metals to be deposited are limited to zinc-based metals and tin-based metals will be explained.

The first requirement for these metals is that the diffusion layer can be formed at around room temperature.

Second, it is easy to attach to aluminum plates and steel plates by plating.

Thirdly, it is cheap enough to be used industrially.

For example, since Na is a low melting point metal, it is thought that it is easy to form a diffusion layer, but it is difficult to plate it. Gu and Ni-based metals also do not form a diffusion layer at room temperature, and it is not impossible to plate Bi and Pb, but it is not easy.

For the above reasons, zinc-based metals and tin-based metals are suitable as the metal to be adhered to the joint surface. In this case, it is necessary to attach the zinc-based metal or the tin-based metal to at least the joint surface on the aluminum plate side. Since aluminum plates are covered with a dense oxide layer, aluminum plates and steel plates coated with zinc or tin form a diffusion layer that creates a stronger bond through pressure welding than aluminum plates and steel plates. It turns out. Furthermore, if a zinc-based metal or a tin-based metal is attached to the joining surface of the steel sheets, it will be easier to form a diffusion layer than when a bare steel sheet is pressure-bonded to an aluminum sheet to which these metals are attached, and the aluminum sheet and the steel sheet will be bonded together. further increases the bond strength.

In this case, JP-A-58-'3358, in which metals such as zinc and tin are applied only to the steel plate side and the aluminum plate is bonded, is used.
Although the technique disclosed in Publication No. 8 is known, it is reported that sufficient bonding strength cannot be obtained even when pressure welding in such steps because the surface of the aluminum plate is covered with a dense oxide layer. As described later, the effects of the present invention can be obtained by coating the surface of metallic aluminum with zinc or tin while removing the aluminum oxide layer.

An effective means for attaching a zinc-based metal or a tin-based metal to an aluminum plate is displacement plating of zinc or tin with aluminum using an alkaline zinc aqueous solution (zinc acid aqueous solution) or an alkaline tin aqueous solution (stannic acid aqueous solution).

Further, the means for attaching the zinc-based alloy or tin-based metal to the steel plate may be electroplating, hot-dip plating, or vapor deposition.

The amount of these metals deposited on each joint surface of the aluminum plate and the steel plate is preferably 0.5 g/m' or more; if it is less than 0.5 g/lr+', the effect is poor. On the other hand, even if the bonding force is increased to more than 20 g/m', the bonding force increases, but the effect is saturated.

When a zinc-based or tin-based metal is applied and pressure-bonded in this manner, a diffusion layer is easily formed as described above, so that a good bonding state and condition can be obtained at a low rolling reduction rate. That is, in this case, a rolling reduction ratio of 10% or less is sufficient for the steel plate. If it exceeds 10%, softening annealing of the steel plate is required, or by keeping the rolling reduction at 10% or less, the annealing can be omitted, which has a great practical effect.

In addition, the plate temperature during pressure welding is preferably 50 to 300°C at the interface temperature between the aluminum plate and the steel plate. If it is less than 50°C, the bonding force is small, and if it exceeds 300°C, the dissimilar metal and the steel plate or aluminum plate are thick alloys. Forms a layer and reduces bonding strength.

Next, the effects of the present invention will be explained in more detail with reference to Examples.

Example Table 1 shows the types of aluminum plates and steel plates, and the relationship between the plating conditions at the bonding interface and the bonding strength. In the table, Nos., 1, and 2 are comparative examples, and Nos.
is small).

In No. 1, the aluminum plate is not plated, so the aluminum plate and the steel plate are not joined.

In NO.2, the steel plate is galvanized, but the aluminum plate is not plated, so the joint strength is low at 3, g/25mm.

On the other hand, N003 achieved high bonding strength by applying zinc plating to the aluminum plate.

N094 is a steel plate subjected to electrolytic Zn-Xl plating and an aluminum plate subjected to displacement Zn plating.
Even higher bonding strength than 003 was obtained.

In No. 5, a hot-dip galvanized steel sheet produced on a Sendzima one-way hot-dip galvanizing line was used as the steel sheet, and a tin-plated aluminum sheet was pressure-welded to this. In this case, since the aluminum plate is thin (O, Imm), it was broken in the non-peel adhesive strength test (J 15K8854), which means that the aluminum plate has sufficient bonding strength to the steel plate.

In No. 6, a cold-rolled steel plate was used as the steel plate, and a tin-plated aluminum plate was used. The bonding strength is 4kg/25mm, which is lower than No. 5, but it is possible to bond.

No. 7 is the amount of ZnHM relative to the aluminum plate: 0.3
g/+TT', and the bonding strength is lower than that of N005, but greater than that of N081.2.

In addition, the bonding strength (bonding force) between the above aluminum plate and steel plate
The measurement is based on JISK6854 (for adhesives < flI
J? The test was carried out in accordance with C-Visual Strength Test Method).

Effects of the Invention As is clear from the examples below, the present invention makes it possible to obtain an aluminum-coated steel sheet with good workability, and has extremely high industrial utility value.

Claims (2)

[Claims] (1) When an aluminum plate and a steel plate are joined together to produce an aluminum-coated steel plate, a zinc-based metal or a tin-based metal is applied to the joining surface of the aluminum plate in advance, and then the aluminum plate is pressure-welded to the steel plate. A method for manufacturing aluminum-coated steel sheets. (2) When joining an aluminum plate and a steel plate to each other to produce an aluminum-coated steel plate, a zinc-based metal or a tin-based metal is applied to each joining surface of the aluminum plate and the steel plate in advance, and then these are pressure-welded. A method for producing an aluminum-coated steel sheet, characterized by: