The Quality Control And Component Technology Optimization Of AG80 Non Hardening And Tempering Steel For Oil Pipe

Against prominent problem which lie in domestic oil-well pipe, bonding actual refining, continuous metal casting and rolling condition which Ansteel have, proceed research of N80 series oil pipe for heat proof oil pipe. According to property expect of N80 series oil pipe, proceed component design, induction furnace refining in lab, thermal simulation test, rolling and cooling in control test, develop AG80 no hardening and tempering steel for oil pipe which adopting metallographical micro-analysis, SEM and TEM analysis and mechanical property analysis and so on, make analysis for flow which appear in surface of seamless pipe, find the course which create flow, and make measure in order to reducing flow. There are some conclusion mainly in this paper.(1) this is chemical component of AG80 oil pipe: C: 0.26-0.30%, Si: 0.40-0.60%, Mn: 1.50-1.70%, P≤0.020%, S≤0.015%, V: 0.008-0.15%, Ti≤0.02%, N: 0.008-0.012%o(2) after component optimization and rolling in control, according to technological process of converter→LF→continuous metal cast square billet of 280x380mm→get round billet ofφ130mm,φ185mm by continuous metal cast→roll pipe of seamless factory, by which, the strength and plastic property cater to seventh version quest from API Spec 5CT, and property fluctuation is small. Dynamic ductility of AG80 heat insulation oil pipe from all gauge end product cater to norm quest.(3) what is the reason for flaw creating on surface of seamless pipe which is strengthen by V,N microalloy treating, the reason is that there are flaw lie in crude material billet. There are some measures for reducing flaw in seamless pipe surface of N80-V steel: control charge temperature rationally; strengthen deoxidation by adding in Al; make deoxidation by VD treatment; promote V precipitate in transgranular by adding in Ti properly; adjust cooling waterline, abate cooling strength; adopt high rate of extension; make production in 2# continuous metal cast which in better state; make heat rolling to cast billet after underline cooling; improve heating temperature of continuous rolling cast billet, define minimum finished rolling temperature. (4) in the case of approaching actual deforming amount distribution when produce steel pipe in seamless MPM continuous rolling, the lower the temperature, the thinner the granular, the thinner the structure; it can refine austenite granular to roll and size in the case of fast cooling, and the lower the finished temperature the better the thin result; it exist limit to refine F+P structure by refining austenite granular which is controlled by rolling in controlled process.