| The oil industry plays an important role in our national economy. Oil well pipe is an important and must be used material in petroleum and natural gas exploration. As the strategic of oil drilling industry shifts from east to west and coastal。 The exploration become more and more difficult, oil well pipe have to face even more critical conditions, On "Twelve Five" period, Tarim touch and the Sichuan-Chongqing region is still the main battlefield of China’s oil and gas drilling, the reservors of these areas are deep and generally sulfur oil and gas fields, H2S and CO2easily lead sulfide stress cracking and hydrogen-induced cracking, so the development of high-strength corrosion-resistant oil well pipes imperative.This paper combines the Baoji Petroleum Steel Pipe Co., Ltd, and its new "ERW pipe+hot-strentch reduceing+heat treatment+tube processing"production line. Based on carbon-manganese steel to add the right amount of Cr, Mo and and other alloying elements detailed study of the chemical composition and thermal tension reduction, quenching, tempering system parameters on the high-grade oil well pipes microstructure and mechanical properties of the impact. The main conclusion in the following:(1) Low carbon content is difficult to guarantee the strength and hardness, high carbon content easy to make cracks increased sensitivity,will harm to the welding,;The strong degree of increased significantly increased as the molybdenum content and plastic toughness slightly lower. If the Mo content is low will case low hardenability, especially to subsequent the corrosion test, but the high Mo content will increase the cost, in summary the carbeon content is intend to be0.20%and the Mo content is intend to be0.40%.(2)The austenitizing organization at different quenching temperature is typical Lath martensite, as the the austenitizing temperature rises, the austenite grain tended to grow up, austenitizing temperature has little effect on the martensite lath width, the area of martensite packet significantly elevating with the austenitizing temperature increasing, the grain size of austenite is smaller on the quick induction heating than ordinary slow heating.(3)The austenite grain is equiaxed after reheat quenching, there are several different orientation of martensite lath in a prior austenite grain interior. The strong degree of experimented steel significantly reduced with the tempering temperature rose in the process of tempering, plasticity and toughness also improved in this process. When quenching at880℃and620℃tempering holding90min show that the optimum mechanical properties in reheating quenching-tempering process (σ0.2=704MPa、 σb=827MPa,δ=18%、CV=47J).(4)The morphology of austenite was flat elongated along the rolling direction after direct quenching, there are some relatively small secondary lathes between motherboard lather; By contrast direct quenching-tempering process and reheating quenching-tempering process shows that:the strong degree of the former higher than the latter, plasticity and toughness is inversely laws in the same heat treatment conditions. When quenching at880℃and650℃tempering holding90min show that the optimum mechanical properties in direct quenching-tempering process(σ0.2=745MPa、σb=855MPa、δ=23%、CV=33J).According to the above research results we determine the chemical composition of C95grade oil well pipes:0.20%C、0.26%S、0.80%Mn、1.00%Cr.0.40%Mo; And optimization of the heat treatment process is reheating quenching-tempering process to quenching at880℃and620℃tempering holding90min, have optimum mechanical and which meet the standard of API. |
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