Mandrel-free dual-mode pipe drawing process
Due to the uneven distribution of deformation of the single-mode seamless pipe without mandrel, the pipe will burst after drawing. The mandrel-free dual-mode extubation was born.
The coreless dual-mold drawing adopts the principle of reverse tension drawing, that is, the drawing force of the first mold forms a reverse tension on the metal in the second mold during drawing, so the axial direction in the second mold The tensile stress increases and the radial compressive stress decreases, thereby improving the uneven distribution of deformation, reducing harmful residual stress and further controlling the wall thickness. Dual-mode drawing has been used in various drawing methods such as long mandrel, short mandrel, floating mandrel, and no mandrel. It strengthens the cold drawing process, improves product quality and reduces costs. However, for a long time, the lack of theoretical analysis of the process of dual-die drawing has made the advantages of dual-die drawing not fully utilized, which has affected its application.
For this reason, in 1984, the production experiment and technical discussion were carried out on double-die drawing. Through experiments, the effect of double-die drawing on the tube wall thickness was studied; the effect of double-die on the unevenness of pipe deformation; the double-die on drawing force And the influence of power consumption; a new type of combined outer mold for dual-mold drawing.
Experiments show that the coreless dual-mold drawing has the following advantages compared with single-mode drawing: increased pass deformation and increased productivity by about 70%; reduced the unevenness of seamless pipe deformation and improved metal plasticity The residual stress is reduced, and the bending of the steel pipe is reduced; the required deformation work is small, which can save 10% to 15% of power consumption; the pipe wall does not thicken after drawing, and the loss of the pipe head is reduced. In 1992, stainless steel pipes were drawn by dual-die without mandrel, the stress state of the deformation zone was analyzed, and the wall thickness of stainless steel pipe drawn by single-die and double-die was measured, which further proved the above conclusion. , It is more effective than single-mode drawing to reduce the wall.
