| 摘要 |
PURPOSE:To secure the superior close adhesiveness between the fitting surfaces of the outer and inner pipe members by purging the air in the inside space of the outer pipe member by the N2 gas which is not harmful for the close adhesiveness, in the manufacture of a double pipe billet through the shrink fitting of a cylindrical inner pipe member into a cylindrical outer pipe member. CONSTITUTION:An outer pipe member 1 is fixedly supported in erection form onto a supporting board 6 in a cylindrical body 5, and N2 gas is supplied into the inside space S of the outer pipe member 1 from the lower edge side through a feeding hole 8 inside the supporting board, and an inner pipe member 2 is fitted from the upper edge side and shrink-fitted. A heating apparatus 7 is installed in the peripheral direction in the upper part of the cylindrical body 5, and heats the outer pipe member 1. N2 gas is supplied not only into the inside space of the outer pipe member but into the part between the cylindrical body 5 and the outer pipe member 1 from the lower part, and the N2 gas purging effect in the inside space S is improved. Though the N2 gas is charged in substitution for air into the fitting surface between the inner and outer pipe members 2 and 1, the superior close adhesiveness between the fitting surfaces of the both pipes can be secured, since N2 gas solid-solved into metal structure.
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