Smelting technology of non-quenched and tempered N80 steel by BOF-LF-VD

The smelting of non-quenched and tempered N80 steel for oil well piping by basic oxygen furnace (BOF) in Angang was investigated by systematic process design,laboratory experiments,industrial test and manufacturing production. Instead of conventional quenching and tempering process,the chemical composition of the steel was designed by V and N microalloying. Then the smelting process and the process control points of the steel for mass production in Angang steel were determined,especially the regression equation of endpoint carbon content,oxygen content and temperature under actual conditions as well as the VD dynamic model of increasing nitrogen by bottom-blowing. Analysis results of data measured from continuous production show that the non-quenched and tempered smelting process is stable,the chemical composition and metallurgical process were reasonable,moreover the mechanical properties and service performance can meet the specific requirements of oil well pipe production and the standard of API Spec 5CT.