Technology of preparation of a continuous cast billet from stainless steels for rolling on a pipe rolling unit with a continuous mill with controlled-moving beading

The growing demand for seamless pipes made from corrosion-resistant austenitic steel grades is driving the continuous improvement of pipe rolling technologies. The use of continuous casting machines for the production of seamless pipes has long been constrained by the presence of characteristic defects. However, the high economic efficiency of the use of continuous casting machines stimulated the development and improvement of the technology of their production. The article presents a technological scheme for the preparation of a continuously cast billet from stainless steel grades of austenitic class for rolling on an injection molding machine with a continuous mill with a controlled-moveable mandrel. Using the QForm 3D software package, a computer simulation of the piercing process of both a hollow continuous-cast and a solid forged billet was carried out. Based on the results obtained, it was concluded that for rolling pipes made of steel 08-12X18H10T, it is necessary to use a hollow continuous-cast billet. To ensure complete removal of axial looseness (central porosity and axial cracks) of cast metal, a technique for selecting the appropriate drill is proposed. To exclude the application of defects from a sharp edge to the piercing mandrel along the front end of the workpiece between its end and the inner hole, it is proposed to make a rounding. The problem of increasing the wear resistance of pierced mandrels is solved by using a special chemical composition in combination with a special surface treatment of the working cone - the creation of corrugation. The Volzhsky Pipe Plant has done a great job of mastering the smelting and casting of billets of such steels, as well as their preparation and rolling under TPA 159-426 conditions. The proposed technology for the preparation of NLZ steel grades 08-12X18H10T completely eliminates all the drawbacks of the cast metal structure and makes it possible to obtain long special-purpose pipes of high quality inner and outer surfaces with the required set of operational properties.