Tube Billet Heating Defects and Its Prevention

Hot-rolled seamless steel pipe from the tube to the product generally requires two heating, which perforated tube before and after heating and rolling blank pipe diameter at a given pre-heating; production of cold-rolled (pull) when the pipe requires the use of an intermediate annealing to eliminate the residual stress; steel for some special requirements, in order to improve the mechanical properties of steel pipe and improving organizational and process performance, but also its heat treatment. Common tube (pipe) heating tube defects uneven heating, oxidation, decarbonization, heating cracks, overheating, over-burning.

Heated front perforated tube, and its purpose is to improve the ductility; reduce deformation resistance steel; provide good microstructure is rolling. There annular furnace tube furnace, reheating furnace, inclined hearth furnaces and car bottom furnace. Given the shortage of pipe diameter before reheating, which aims to increase the temperature of the tube and a uniform shortage and improve the ductility of steel, control its microstructure, create favorable conditions for the mother pipe sizing and ensure the mechanical properties of steel. Common type reheating furnace stepping furnace, continuous roller hearth reheating furnace, the furnace hearth oblique, inductive reheating furnace. Cold-rolled (pull) reheating hardening mainly to eliminate, reduce deformation resistance. Common annealing furnace is mainly used in reheating furnace, car bottom furnace, continuous roller hearth furnace. In the production of seamless steel tubes, annular furnace and reheating furnace is currently the most widely used; electric induction furnace is also being developed; inclined hearth heating furnace because the quality is not high, labor-intensive and tend to be eliminated. Continuous roller hearth furnace is mainly used in cold-rolled (pull) the heat treatment of steel; car bottom furnace suitable for smaller batches, heat treatment time is longer heating and insulation thick-walled alloy steel pipe; protective gas continuous roller hearth furnace is mainly used in steel surface requires heat treatment and cold finished steel without oxidation (pull) during the pickling process annealing.