In this article the manufacturing method and characteristics of the double wall brazed tube with inner helix groove are given The effect of the parameters of inner helix groove on the heat transfer efficiency is investigated The effect of inner helix groove must be considered when strip width,sizing roll pass,mandrel diameter and sizing force are to be determine

The factors affecting on forming quality of tube has been found by simultaneous multipoint measurement of forming process of double wall brazed tube, and a control model of forming quality has been established.

This article analyses manufacture process and preheating process of galvanized welded pipe with plastic coating,proposes mathematic model for preheating process and obtains calculation formula for preheating temperature.

Forming process of quadruple-layer brazed steel tubes is characterized by large elastic-plastic deformation,which involves both nonlinear geometrical and material conditions.