热处理对高压气瓶用34CrMo4H钢力学性能的影响

Effect of heat treatment on mechanical properties of 34CrMo4H steel for high-pressure cylinders

研究了不同淬火温度、回火温度、回火时间、冷却方式、预处理工艺对气瓶用34Cr Mo4H高强度钢力学性能的影响。结果表明,随淬火温度的提高,其抗拉强度增大,冲击韧度和伸长率降低;随回火温度的提高,其抗拉强度降低,伸长率增大,在540~570℃回火时冲击韧度表现为变化不明显,然后随回火温度的提高而增大。油淬或水淬,其强度、冲击韧度基本一致,但油淬的伸长率比水淬高2%;随回火时间的延长,其强度降低,冲击韧度值增大,伸长率在回火时间为2 h时最大,然后随回火时间的延长或缩短,逐步降低。最佳的热处理工艺为840~900℃淬火,水或油淬＋570~610℃回火1~2.5 h,可以获得符合ISO 9809-2：2010标准和设计要求的力学性能;在最终调质处理前增加870℃正火预处理,可进一步改善34Cr Mo4H钢的塑韧性。

Effects of quenching temperature,tempering temperature and time,cooling method and pretreatment process on mechanical properties of 34 Cr Mo4H high-pressure cylinders steel were studied. The results show that the tensile strength increases,the impact value and percentage of elongation reduce with increase of quenching temperature. The tensile strength reduces,percentage of elongation increases with increase of tempering temperature,impact value is almost the same when tempering temperature is between 540-570 ℃,but then increases with increase of tempering temperature. Under oil quenching or water quenching,the strength and impact value are almost the same,but the percentage elongation by oil quenching is 2% higher than water quenching. The strength reduces,impact value increases with extension of tempering time,the percentage of elongation is highest for tempering time of 2 h,and then reduces with extension or short of tempering time.The optimum heat treatment process consists of heating at 840-900 ℃ and then water or oil quenching,tempering at 570-610 ℃ for 1-2. 5 h.The 34 Cr Mo4H steel can obtain the specified properties with this process which meet the requirements of ISO 9809-2： 2010 standard and design requirement. Normalizing at 870 ℃ as pre-heat treatment can further improve the plasticity and toughness of the steel.