JPS63123584A - Manufacture of clad material - Google Patents

Abstract

PURPOSE:To manufacture the clad material of excellent quality having no crack by an explosive welding by coarsening a grain prior to overlapping the plate stock of a super plastic material and after its explosive welding to the plate stock of a steel material returning the grain of the super plastic material to a fine original nature by hot treatment. CONSTITUTION:The plate stock 2 by a super plastic material is heated within the range not exceeding the transformation point thereof in advance prior to overlapping it on the plate stock 1 of a steel material and the grain is subjected to coarsening by slowly cooling it thereafter. The plate stock 2 of the super plastic material whose grain is coarsened and the plate stock 1 of steel material are overlapped and the joining of the both is performed by an explosive welding. The laminated structure completing the explosive welding is then re-heated up to the temp. beyond the transformation point of the super plastic material and by rapidly cooling it thereafter the plate stock 2 of the super plastic mate rial is returned to the original nature of the grain being fine. The intensity against the big variation in the distorsion speed is improved by the part where the grain is coarsened and the generation of a crack at the joining time can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a method for manufacturing a laminated material having a laminated structure of a plate made of superplastic material and a plate made of steel.

``Conventional Technology J Laminated materials (also called cladding materials) are made by overlapping and bonding sheets of different metals together, and can provide advantages that cannot be had with individual metal sheets.

Recently, in order to obtain a material with properties such as earthquake resistance and shock absorption, there has been interest in the above-mentioned laminated material in which a plate made of superplastic material and a plate made of steel are joined together.

By the way, in order to increase the bonding strength between the plates that make up the laminated material, it is necessary to create atomic bonds at the interfaces between the plates. Up until now, the manufacturing methods for the laminated materials have been casting, forging, etc. Various methods using rolling have been studied, but recently a method has been developed that involves simply joining together stacked plates by explosive bonding, with the aim of shortening the time required to join the plates together. It has come to be the subject of research.

``Problems to be Solved by the Invention'' However, in order to obtain a laminated material made by laminating the above-mentioned superplastic plate and steel plate, it was attempted to simply overlap the two plates and join them by explosive bonding. Then,
A problem occurred in which cracks occurred in the plate material made of superplastic material.

The inventor of the present application conducted the following analysis regarding the occurrence of such a problem.

When joining stacked plates together, distortion occurs at the interface between the plates, but since bonding by explosion bonding is instantaneous, there is less distortion during bonding compared to other joining methods such as rolling. Progression speed of the resulting strain (hereinafter referred to as strain rate)
becomes very large.

However, superplastic materials generally have fine crystal grains,
Therefore, it is vulnerable to deformation with large strain rates.

Therefore, when explosive bonding is applied as a means of joining plates made of superplastic material, the strain rate exceeds the allowable limit, and an unreasonable load is applied to the superplastic plate itself, resulting in cracking. .

This invention was made based on the above-mentioned analysis, and involves joining a plate made of a superplastic material and a plate made of a steel material by explosive bonding. To provide a method for manufacturing a laminate material that can obtain a laminate material of excellent quality without causing any problems.

"Means for Solving the Problems" The method for manufacturing a laminated material according to the present invention is a method for manufacturing a laminated material that has a laminated structure of a plate made of superplastic material and a plate made of steel, and has fine crystal grains. Plate materials made of superplastic materials are made by heating the superplastic material in advance within a range that does not exceed its transformation point, and then cooling it slowly to coarsen the crystal grains. The plate material made of the above-mentioned steel material and the plate material made of the above-mentioned steel material are overlapped and the two are joined by explosion bonding, and the laminated structure that has completed the explosion bonding is reheated to a temperature higher than the transformation point of the superplastic material, and then The method is characterized in that the plate material made of the superplastic material is returned to its original state with fine crystal grains by rapid cooling.

"Function" In the method for manufacturing a laminated material according to the present invention, the superplastic material plate is heated within a range not exceeding its transformation point before being superimposed on the steel plate material, and then slowly cooled. The crystal grains are coarsened.For this reason, the superplastic material plate used when superimposed on the steel plate has different properties from the original superplastic material, which has fine crystal grains. , the strength against deformation with a large strain rate is improved, and this improvement can prevent the occurrence of cracks during bonding due to explosive bonding.

In addition, in the present invention, the laminated structure that has been joined by explosion bonding is reheated to a temperature higher than the transformation point of the superplastic material, and then rapidly cooled, so that the plate material made of the superplastic material has crystal grains. Since the superplastic material returns to its original fine state, the original characteristics of the superplastic material are not impaired, and a high-quality laminate material can be obtained.

"Example" An embodiment of this invention will be described below.

FIG. 1 shows a laminate manufactured according to the present invention.

This laminated material is made by overlapping and joining plate material 2 made of superplastic material on both sides of plate material 1 made of steel material, and the superplastic material is an alloy of zinc (Zn) and aluminum (i).
A material with an aluminum content of 22% was selected.

This laminated material is manufactured by the following method.

Plate material 2 made of superplastic material originally has fine crystal grains, but when manufacturing a laminated material, before stacking it on plate material I made of steel material, it must be heated within a range that does not exceed its transformation point. The crystal grains are coarsened by heating and then cooling slowly. In the case of the superplastic material used in this example, the eutectoid transformation point is approximately 275°C.
Therefore, the heating temperature was set in the range of 250 to 270°C, and heating was continued at this temperature for about 10 hours or more.

Next, the above-mentioned plate material 2 made of a superplastic material with coarsened crystal grains and the plate material I made of a steel material are placed on top of each other, and the two are joined by explosive bonding. Various operations for explosive bonding are performed in the same way as in the conventional case.

Next, the laminated structure that has undergone explosion bonding is reheated to a temperature higher than the transformation point of the superplastic material, and then rapidly cooled to form the plate material 2 made of the superplastic material with fine crystal grains. return to its original state. In this example case,
The heating temperature was set at 280 to 300°C, and the cooling was performed by rapidly cooling to room temperature using water.

According to the method described above, the plate material 2 made of superplastic material when superimposed on the plate material l made of steel material is different in properties from the original superplastic material with fine crystal grains, and the crystal grains are coarsened. The strength against deformation with a large strain rate is improved accordingly, and this improvement can prevent the occurrence of cracks during bonding due to explosive adhesion.

In fact, when heat treatment was performed as shown in the example, no cracking occurred at all.

In addition, in the manufacturing method of this embodiment, the laminated structure that has been bonded by explosion bonding is reheated to a temperature equal to or higher than the transformation point of the superplastic material, and then rapidly cooled to form an areal superplastic material. Since the plate material 2 is returned to its original state with fine crystal grains, the original properties of the superplastic material are not impaired, and a high-quality laminate material can be obtained.

When the vibration absorbing properties and soundproofing properties of the laminated material manufactured by the method of one example were tested, good results were obtained.

It should be noted that the superplastic material to which this invention can be applied is not limited to one example of surface properties. Similar effects can be obtained for superplastic materials of other compositions by selecting the heating temperature according to their transformation points.

Further, the number of layers to be laminated is not limited to the example, and can be changed as appropriate depending on the application.

"Effects of the Invention" As is clear from the above explanation, in the method for manufacturing a laminated material according to the present invention, a plate made of a superplastic material is heated within a range that does not exceed its transformation point before being superimposed on a plate made of a steel material. Then, the crystal grains are coarsened by cooling slowly. Therefore, the properties of the superplastic material plate used when superimposed on the steel material plate material are different from the original superplastic material, which has fine crystal grains, and the strength against deformation at large strain rates is increased by the coarser crystal grains. This improvement makes it possible to prevent cracks from occurring during bonding due to explosive bonding.

Further, in the present invention, the laminated structure that has been joined by explosion bonding is reheated to a temperature higher than the transformation point of the superplastic material, and then rapidly cooled to form a plate material made of the superplastic material with crystal grains. Since the superplastic material returns to its original fine state, the original properties of the superplastic material are not impaired, and a high-quality laminate material can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a laminate manufactured by the present invention. l・2・・・・・・Plate material.

Claims (1)

[Claims] A method for manufacturing a laminated material having a laminated structure of a plate made of a superplastic material and a plate made of a steel material, in which the plate made of the superplastic material with fine crystal grains is heated in advance within a range that does not exceed its transformation point, After that, the crystal grains are coarsened by slow cooling, and the plate made of the superplastic material with the coarsened crystal grains and the plate made of the above-mentioned steel are overlapped and the bonding between the two is made by explosion bonding. The laminated structure that has undergone explosion bonding is reheated to a temperature higher than the transformation point of the superplastic material, and then rapidly cooled to return the superplastic material to its original state with fine crystal grains. A method for producing a laminated material characterized by returning it.