Dissimilar metal joint including flame-retardant magnesium alloy layer

#The present invention relates to a dissimilar metal joint in which two or more layers of different types of metal materials are joined, wherein at least one layer is composed of a magnesium alloy having flame retardation.

#There is a growing demand for lightweight materials for use in transport equipment such as aircraft, railway cars or automobiles in an attempt to reduce fuel consumption by reducing weight. There is a particularly strong demand for multimaterialization in which suitable lightweight materials are used at suitable locations corresponding to the characteristics of each material.

#Among such lightweight materials, magnesium is expected to be used as a transport equipment structure based on its light weight. In particular, flame-retardant magnesium alloys are alloys in which flame retardation of the magnesium alloy has been improved by the addition of calcium, for example, and are expected to be used as a structure for railway cars and the like.

#FIG. 1 is a schematic diagram showing one example of a dissimilar metal joint of the present embodiment. In the diagram, t indicates the total thickness of the joint.

#FIG. 2 is a schematic diagram of explosive welding.

#FIGS. 3(a) to 3(g) indicate examples of forms of the dissimilar metal joint of the present embodiment.

#The following provides a detailed explanation of embodiments of the present invention.

#A first embodiment is a dissimilar metal joint for a transport equipment structure in which two or more layers of different types of metal materials are joined, wherein, at least one layer of the two or more layers of metal materials is composed of a flame-retardant magnesium alloy, another layer is composed of a metal or alloy selected from the group consisting of aluminum alloy, titanium alloy, stainless steel and steel, and the two or more layers of different types of metal materials are mutually joined over the entire surface of joining surfaces that respectively overlap.

#In the present description, “flame-retardant magnesium alloy (or magnesium alloy having flame retardation)” refers to magnesium alloy that has been alloyed for the purpose of increasing ignition temperature. Although the ignition temperature of ordinary, general-purpose magnesium alloy (specific examples of which include AZ31, AZ61 and AZ91) is roughly 500° C. to 600° C., any magnesium alloy having an ignition temperature higher than this may be referred to as flame-retardant magnesium alloy. A flame-retardant magnesium alloy (or magnesium alloy having flame retardation) preferably has an ignition temperature that is 100 K or more higher (600° C. or higher), more preferably 150 K or more higher (650° C. or higher), and even more preferably 200 K or more higher (700° C.) than general-purpose magnesium alloy. The ignition temperature of flame-retardant magnesium alloy is preferably higher than the melting point thereof. If it is necessary to measure the ignition temperature of an alloy for which the ignition temperature is unknown, ignition temperature can be confirmed by differential thermal analysis (DTA).