PURPOSE: To prevent the generation of the crack while working the explosive pressure welding, and to manufacture the composite matallic sheet of excellent quality, by previously holding the metallic material, being readily causable the low temperature brittleness, at a specified temperature, and then, by carrying out the explosive pressure welding, at manufacturing the composite metallic sheet.

CONSTITUTION: The metallic material like as low alloy steel, copper alloy, etc., being readily causable the low temperature brittleness, is previously heated to 35W 75°C (cracks are generated under 35°C, and the handling is difficult above 75°C which is then useless), by the hot air heater, etc.; and then, the explosive pressure welding is carried out. Thus manufactured clad steel is free from the cracking. As a result of study in detail on many results of actual production, it is discovered that all materials of the clad steel have a tendency to hardly cause the crack in the summer season as compared with the winter season; this invention is accomplished depending on this discovery. The defect of the conventional method, like as the danger of explosion due to the high temperature heating of the steel material, the difficulty in handling, etc., is dissolved, and the clad steel of excellent quality can be manufactured.