PURPOSE: To reduce the crop loss of clad material and to improve a yield by fitting a hollow outer material for cladding and an inner material for cladding of which one end is stepped in the same external shape to the outer material for cladding and hot extruding so as to be taken the other stepped end side of the inner material as the back end of the direction of hot extrusion.
CONSTITUTION: An outer material 4 for cladding (stainless steel) is taken as a hollow cylinder, the inner material 5 for cladding (common steel) is taken as a stepped solid cylinder and a billet 10 for the extrusion of clad section is formed by fitting them. At that time, the inside diameter of the outer material 4 is approximately conformed to the outside diameter at the small diameter part of the inner material, the outside diameter of the outer material 4 is conformed to the outside diameter at large diameter part of the inner material 5 and the length of the outer material 4 and the length of small diameter part of the inner material 5 are conformed. Under that configuration, the billet 10 for the extrusion of clad section is hot extruded from the small diameter side of the inner material 5 with a die 6. Thus the outer material 4 doesn't remain in the crop part after the cutting-off position 7, so the yield is improved.
KAMEMURA YOSHIKI
KOBAYASHI NORIO
