| 摘要 |
1.A mandrel for extending the internal pipe in the process of forming ribs on bimetallic pipes with the application of the initial compressive stresses of the external pipe, characterized in that it consists of an alignment element (1) with the diameter lesser than the internal diameter of the external pipe (2), a cylinder-shaped or cone-shaped working part (3) converging towards the end of the internal pipe (2) and diameters lesser than or equal to the external diameter of the internal pipe (2), and a front part (4) with the diameter exceeding the maximum diameter of the working part (3), so that at the end of the working part (3) an orifice (5) can be created, and the diameter of the front part (4) is lesser than the diameter of the base of the ribs being formed.<IMAGE>
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