LOW-CARBON METALLURGICAL CONCEPTS FOR SEAMLESS OCTG PIPE
Seamless pipes are available with wall gages of up to 100 mm and outer diameters up to around 700 mm.Such pipes are typically used for oil country tubular goods as well as for structural applications.Due to market requirements the demand for high strength grade seamless pipes is increasing.Many applications need high toughness in addition to high strength.The different rolling processes applied in production depend on wall gage and pipe diameter.The continuous mandrel mill process is used to produce smaller gages and diameters; plug mill processing covers medium gages and diameters; Pilger mill processing allows producing larger diameters and heavy wall gage.In all these processes only a limited degree of thermo-mechanical rolling can be achieved.Therefore strengthening and toughening by severe grain refinement employing a conventional niobium-based microalloying concept is not easily achievable.Accordingly,high strength and toughness seamless pipe is typically produced via a quench and tempering process route.This route however is costly and above that often constitutes a capacity bottleneck in the mill.Innovative low-carbon alloy concepts however do allow producing strength up to grade X70 at very high toughness directly off the rolling plant,i.e.,without quench and tempering treatment.Due to the low carbon content also welding is much facilitated.The paper reveals the metallurgical principles,which are based on appropriate niobium and molybdenum alloying.Additionally the paper demonstrates how heavy gaged seamless pipes up to 70 mm wall thickness can be produced based on a low-carbon Nb-Mo approach using quench and temper treatment.
seamless pipe acicular ferrite toughness TMCP Q&T air cooling
Hardy Mohrbacher
NiobelCon bvba 2970 Schilde,Belgium
国际会议
Energy Materials 2014(第一届能源材料国际会议)
西安
英文
673-678
2014-11-04（万方平台首次上网日期，不代表论文的发表时间）