Improving the technology used to make welded carbon-steel tubes

Abstract

Electric-welded tubes made of carbon steels are less expensive, have a better-quality surface, and have more accurate dimensions than equivalent seamless tubes. An efficient method has been proposed for making the distribution of the strains and residual stresses in such tubes more uniform about their perimeter (and reducing the stress level in general). The method employs cold reduction in the final passes of the forming mill, which has a closed pass. Similar reductions are also made in the welding and guide stands. The authors constructed a model to control the voltage on the induction coil, and they determined the dependence of temperature in the welding zone on the length of the edges in the welding gap. The introduction of new tube-production methods and equipment developed as part of this research has made it possible to master the industrial production of new types of special-use tubes, tubes with fewer or no internal burrs, and tubes with stronger welds, better mechanical characteristics, and other improved quality indices.