Nonoxidative heat treatment of stainless steel pipes with process oil residues

Abstract

1. Methods of joint nonoxidative heat treatment and removal of residues of process oil from the surface of rolled stainless steel products without subjecting them to special chemical treatment are based on burning out the oil residues with the required access of oxygen, either by the thermal decomposition of these residues and removing them in the gaseous state by evacuation of the furnace chamber, or by blowing a protective gas through it. 2. Complete removal of the residues of process oil from the surface of stainless steel pipes, a light and clean surface, and also the required anticorrosion properties of products heat-treated in hydrogen furnaces are attained when the dew point of hydrogen is changed from \t-30\dgC in heating to 400\2-500\dgC to \t-65\dgC in heating to 900\2-1100\dgC. For processing in continuous furnaces it is recommended to ensure specific hydrogen supply equal to 10–30 m3 SPP·h−1/m2 at a heating rate of 200–300 deg/min, and in compartment-type furnaces 0.6–5.0 m3 SPP·h−1/m2 at a heating rate of 50–100 deg/min. 3. Application of the joint technology that includes removal of oil residues and heat treatment makes it possible to reduce operating costs, improve the quality of the pipes, and reduce capital expenditures on equipment for the chemical treatment of the pipes.