Abstract: Taking 9Ni steel plate as the object of analysis， the different heat treatment processes of 9Ni steel plate in the head manufacturing process were simulated in the laboratory， and the properties of the test plate in hot-formed state，hot-formed state+QT state，hot-formed state+NNT state and the corresponding post-welded stress relieving state were investigated respectively.The results show that： 20 mm thick 9Ni steel test plate after 930 ℃ high-temperature hot forming，the base material structure was completely destroyed，its reverse austenite basically disappeared，the yield strength decreased by 100 MPa，and the maximum impact energy absorbed at -196 ℃ was only 10 J，it must be re-heat treated to restore the mechanical properties. After hot forming， the mechanical properties of the test plate were restored using the NNT process. Compared with the QT recovery process， the -196 ℃ impact absorption energy， room temperature yield strength， and room temperature tensile strength were significantly lower. The reason for this was that the NNT process test plate contained significantly lower content of inverted austenite than the QT process test plate. Therefore， the mechanical properties restored by QT process were good and stable. After the elongation cold deformation of 2.5%-7.5%， when the aging treatment temperature reached 250 ℃， the average aging sensitivity coefficient of 20 ℃ and-196 ℃ shock absorption energy was 0.62% to 10%， and the aging sensitivity of the base material was low；When the aging treatment temperature reached 540 ℃， the average aging sensitivity coefficient was 13.93% to 30.63%. Although the aging sensitivity of the base material slightly increased， the impact absorption energy showed a small decrease， but all were greater than 180 J. The surplus of impact absorption energy of the base material was still relatively large.

Key words: 9Ni Steel Plate, Hot Forming, Post-welded, Stress Relief, Reverse Austenite, Impact Energy Absorption

摘要： 以9Ni钢板为分析对象，在实验室模拟9Ni钢板在封头制造过程中的不同热处理工艺，分别对热成型态、热成型态+QT态、热成型态+NNT态及与之对应的焊后消应力态试板性能进行了研究。结果表明，20 mm厚9Ni钢试板经过了930 ℃高温热成型后，母材组织被完全破坏，其逆变奥氏体基本消失，屈服强度下降100 MPa，-196 ℃冲击吸收能量最高仅10 J，必须重新热处理以恢复力学性能。热成型后的试板利用NNT工艺进行力学性能恢复，与QT工艺恢复性能相比，-196 ℃冲击吸收能量、室温屈服强度、室温抗拉强度均明显偏低，其原因在于NNT工艺试板所含逆变奥氏体含量明显低于QT工艺试板。因此，经QT工艺恢复的力学性能良好、稳定。试板经过2.5%~7.5%的伸长冷变形后，当时效处理温度达250 ℃时，20、-196 ℃冲击吸收能量平均时效敏感系数为0.62%～10%，母材的时效敏感性低；当时效处理温度达540 ℃时，平均时效敏感系数为13.93%～30.63%，母材的时效敏感性虽略有升高，冲击吸收能量出现了小幅度降低，但均大于180 J，母材冲击吸收能量富余量仍较大。

关键词: 9Ni钢板, 热成型, 焊后, 消应力, 逆变奥氏体, 冲击吸收能量