不同热处理工艺对35CrMo钢应力腐蚀敏感性影响的研究

【作者】 冯朋飞；

【导师】 李春福；

【作者基本信息】 西南石油大学 ， 材料学， 2011， 硕士

【摘要】 本文通过对石油设备及井下工具常用钢低合金高强度35CrMo钢进行热处理来改善材料的组织结构性能及晶粒尺度。并借助慢应变速率拉伸(SSRT)实验,结合现代微观分析方法,在以不同充氢电流密度进行动态电化学充氢的环境下研究组织结构及晶粒尺度对35CrMo钢应力腐蚀敏感性的影响。随着近几十年来,对酸性油气田以及高含H2S油气田开发增加的局面,增强了石油设备及井下工具发生应力腐蚀或滞后开裂的可能性,因此研究该钢种应力腐蚀或滞后开裂行为对油气田开发过程中安全问题具有重要的意义。试验结果表明：35CrMo钢抗应力腐蚀或滞后开裂敏感性随着动态电化学充氢电流密度的增加而降低；35CrMo钢经过完全淬火+亚温淬火+高温回火可以把晶粒度细化到10.8μm,晶粒度级别为10.0-10.5级,且在动态充氢电流密度为150mA/cm2和200mA/cm2时还具有很好的强塑性,其断裂强度分别为570MPa、580MPa,延伸率分别为15.5%、15.0%,以及断面收缩率分别为38.96%、33.27%；35CrMo钢在经过亚温淬火+高温回火后可以得到显微组织结构细小、均匀的回火索氏体和未溶铁素体,这不仅能提高35CrMo钢的力学综合性能,而且通过增加组织中氢陷阱的相对量以及均匀性,达到提高35CrMo钢抗应力腐蚀或滞后开裂性能的目的；35CrMo钢抗应力腐蚀或滞后开裂敏感性均随组织均匀化及晶粒尺度的细化而提高,改善组织均匀化及细化晶粒是提高35CrMo钢抗应力腐蚀敏感性的一种有效途径。更多还原

【Abstract】 The main aim of this thesis is to improve the microstructure of materials and the grain size through the heat treatment process of high-strength low alloy 35CrMo steel which is common component of oil equipments and downhole tools. An experiment is conducted in the paper to study the influence of the grain size and the microstructure of materials on the stress corrosion cracking susceptibility of 35CrMo, through dynamic electrochemical charging in different current density, slow strain rate tension technique (SSRT) and modern microscopic analysis method. In recent decades, the extensive explorations of acidic oil and gas field or high H2S oil and gas field increased the possibility of stress corrosion cracking in oil equipment or down hole tools. Therefore, the research on 35CrMo steel’cracking caused by the stress corrosion or lag cracking is extremely significant for the safety of oilfield development process.The results show:The susceptibility of 35CrMo steel resistance stress corrosion lag cracking reduced with the increase of dynamic electrochemical charging current density 35CrMo steel grain size could be refined into 10.8μm and the grain grade was 10.0-10.5 at completely quenching and sub-temperature quenching and high temperature tempering process. Meanwhile, under the dynamic hydrogen charging and the dynamic electrochemical charging current density was 150mA/cm2 and 200mA/cm2,35CrMo steel is a very plastic and the fracture strength was 570MPa.580MPa, the elongation rate was 15.5%、15.0%, and reduction area of crosssection was 38.96%、33.27%. Fine and uniform tempering sorbite and undissolved ferrite micro structure will be derived from 35CrMo steel through sub-quenching temperature and high tempering tempering process. Under that condition, it will not only enchance the comprehensive mechanical performance of 35CrMo steel, but also increase the hydrogen traps’relative amount and enhance its uniformity, through which enhance the sussceptibility of 35CrMo steel resistance stress corrosion cracking. The susceptibility of 35CrMo steel resistance stress corrosion lag cracking was enhanced with the increasing refinement of grain size. Therefore, it can be seen that grain refinement is an effective way to enhance the susceptibility of 35CrMo steel resistance stress corrosion lag cracking.更多还原