| 摘要 |
PURPOSE:To improve the resistance to internal pressure of a pipe by suppressing the lowering of adhesion due to the generation of weldline by a method wherein a plurality of supporting plates, which support a male mold in a female mold, are divided in the circumferential direction into inside supporting plates and outside supporting plates and, in addition, the positions of the inside supporting plates and of the outside supporting plates are arranged out of phase so as to locate one at middle angle of the space intervals of the other. CONSTITUTION:A plurality of supporting plates, which concentrically support a male mold in a female mold, are divided in the circumferential direction into inside supporting plates 3a and outside supporting plates 3b. Because weldlines W are generated in forms after the arrangements of the supporting plates 3a and 3b and a ring 4, radial weldlines W are divided into two in such a manner that their positions mutually locate at middle angle of the space intervals of their opposite positions. Consequently, the length of the weldline W directing from inside to outside is made longer than that of the weldline of a pipe, which is shaped by the conventional method. Because the area of the weldline part is large, the strength against the rapture due to inner pressure is enhanced in proportion to the area of the weldline part and consequently the resistance to internal pressure of a pipe P is improved. |
