时效温度对马氏体时效钢及时效不锈钢延迟断裂倾向的影响

发布时间：2018-02-24 03:44

  本文关键词： 马氏体时效钢 时效温度 延迟断裂倾向 缺口敏感性　出处：《钢铁研究总院》2015年硕士论文　论文类型：学位论文

【摘要】：氢致静载延迟断裂是载荷低于设计许可应力的一种突发性断裂,其后果往往是灾难性的,马氏体时效钢重载构件曾发生过较多的事故,为此许多研究学者对比研究了马氏体时效(不锈)钢欠时效、峰时效和过时效处理在H2、饱和H2S溶液等氢环境下延迟断裂行为,证明欠时效处理后氢致延迟断裂抗力最低。然而,马氏体时效(不锈)钢可容忍的极限氢含量极低,在正常的冶炼和热加工后是否发生氢致延迟断裂未进行过研究,本文研究了时效温度对马氏体时效(不锈)钢延迟断裂抗力的影响。研究选用18Ni350马氏体时效钢和Cr-Ni-Mo-Ti马氏体时效不锈钢棒材,以及2.0mmm厚冷轧带材,原材料经双真空冶炼,氢含量不高于2.0ppm,时效温度(420～540℃)覆盖了欠时效、峰时效和过时效。采用缺口拉伸试验,对比拉伸位移速率0.15mm/min(快拉伸)和0.0015～0.005mm/min(慢拉伸)的断裂强度,并用此评价氢致延迟断裂倾向,研究主要得到下述结果：18Ni350马氏体时效钢420。C和450℃欠时效态强度较低,但缺口敏感性较高,氢含量低于1.Oppm情况下仍表现出较高的氢致延迟断裂倾向；480℃时效强度略低于510℃峰时效,但缺口敏感性较低,缺口抗拉强度高出峰时效100MPa以上；540℃过时效强度下降,但未降低缺口敏感性,尽管氢含量不变,480～540℃时效未表现出氢致延迟断裂倾向。Cr-Ni-Mo-Ti马氏体时效不锈钢棒材缺口快拉伸(0.15mm/min)在480～500℃时效出现强度峰值；氢含量不高于2.0ppm情况下,420℃和440℃欠时效发生氢致延迟断裂,但460～520℃时效则未表现出氢致延迟断裂倾向。Cr-Ni-Mo-Ti马氏体时效不锈钢冷轧带材在440～520℃之间时效光滑拉伸强度下降,而热轧带材在480-500℃之间时效出现强度峰；另一方面,冷轧变形增大过时效倾向,因此冷轧变形具有增强时效动力学作用。冷轧变形显著提高时效后的强度,但并未增大缺口敏感性,尤其是460℃以上时效,冷轧带材缺口敏感性指数接近于热轧带材。尽管冷轧带材强度提高230～460MPa,但480℃以上时效后并未表现出延迟断裂倾向,证明冷变形是提高马氏体时效不锈钢强度的可靠方法。
[Abstract]:Hydrogen induced static load delayed fracture is a kind of sudden fracture whose load is lower than the design allowable stress, and its consequence is often catastrophic. There have been many accidents in maraging steel heavy load members. For this reason, many researchers have comparatively studied the delayed fracture behavior of martensite aged (stainless) steel under H _ 2, H _ 2S saturated H _ 2S solution and peak aging treatment. It is proved that the hydrogen delayed fracture resistance is the lowest after underaging treatment. The tolerable limit hydrogen content of maraging (stainless) steel is very low. Whether hydrogen induced delayed fracture occurs after normal smelting and hot working has not been studied. In this paper, the effect of aging temperature on the delayed fracture resistance of martensite aging steel (stainless steel) is studied. 18Ni350 maraging steel and Cr-Ni-Mo-Ti maraging stainless steel bar and 2.0 mm thick cold rolled strip are used in the study, and the raw materials are smelted in double vacuum. The underaging, peak aging and overaging were covered with hydrogen content of not more than 2.0 ppm. The tensile strength of 0.15mm / min (fast tension) and 0.00155mm / min (slow tension) were compared with the tensile displacement rate of 0.15mm / min (fast tension) and 0.00155mm / min (slow tension) respectively, and the tendency of hydrogen induced delayed fracture was evaluated by this method. The main results are as follows: 420.C and 450 鈩，

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