PURPOSE: To equalize the average plate thickness of each clad steel plate and each plate inner thickness by making the upper side base material of a composite thicker in a prescribed ratio than the lower side base material, heating it uniformly by covering the upper face with a heat retaining cover having a specified thickness, and rolling it by removing the cover immediately before its rolling.
CONSTITUTION: A separating material 3 is placed in the gap of separating surfaces 12 of two pieces of composite materials 2, and thereafter, each composite material is welded. Also, they are prepared so that the thickness of the upper side base material becomes thicker in the prescribed ratio than that of the lower side base material, joint surfaces 11 of the upper and lower base base materials 1 are opposed to each other, and between them, the composite material is placed through an insert metal 4 for reinforcing the junction. Next, the gas absorbing substance 5 of Zr, Ti, etc. is inserted into the gap of a frame material 6 and the composite material 2, and the shield-welding of the frame material 6 and the composite material 2 is executed. Thereafter, a forced exhaust is executed from a pipe 8. In a state that the upper face of this composite is covered with the heat retaining cover of ≥1mm thickness, the composite is heated uniformly to a temperature being below the melting point of each material. Immediate before rolling, the cover is removed and hot rolling is executed, and a clad steel plate is formed by cutting the periphery thereof.
MATSUOKA MASANORI
OE KENICHI
SHIBATA MITSUAKI
