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本文研究了淬火温度对4330M钢在蒸馏水中的应力腐蚀裂纹扩展速率的影响。实验表明,淬火温度从870℃上升到1100℃时,裂纹扩展速率da/dt显著下降(相差一个数量级);从1100℃上升到1200℃时,裂纹扩展速率da/dt却稍提高,在1100℃处,da/dt有一最小值。断口分析表明,随淬火温度升高,应力腐蚀的断裂方式有所改变,870,1000℃淬火的试样系沿晶断裂,而1100,1200℃淬火试样则是穿晶准解理断裂。用饱和苦味酸溶液腐蚀显示奥氏体晶界,通过奥氏体晶界腐蚀沟槽深度估算出杂质磷在奥氏体晶界的平衡偏聚浓度,它和淬火加热温度之间的关系符合Mclean的平衡偏聚理论。磷在奥氏体晶界的偏聚是造成应力腐蚀裂纹扩展速率da/dt变化的主要原因。采用杂质原子偏聚和氢对脆性断裂影响的理论,对各种实验现象加以解释,并认为杂质原子在晶界偏聚和氢共同作用的氢脆断口是沿晶断裂型,而单纯氢起作用的氢脆断口是穿晶准解理断裂型。
In this paper, the effect of quenching temperature on the stress corrosion crack growth rate of 4330M steel in distilled water was studied. The experimental results show that the crack growth rate da / dt decreases obviously (by an order of magnitude) when the quenching temperature increases from 870 ℃ to 1100 ℃, while the crack growth rate da / dt slightly increases from 1100 ℃ to 1200 ℃. At 1100 ℃ At, da / dt has a minimum value. Fracture analysis shows that with the increase of quenching temperature, the stress corrosion cracking mode is changed. The samples hardened at 870 and 1000 ℃ are intergranular fracture, while those at 1100 and 1200 ℃ are transcrystalline quasi-cleavage fracture. Corrosion with saturated picric acid solution shows austenite grain boundaries, and the equilibrium segregation concentration of impurity phosphorus in austenite grain boundaries is estimated by the depth of austenite grain boundary corrosion groove. The relationship between quenching temperature and quenching temperature is in accordance with Mclean Balance theory of balance. The segregation of phosphorus in austenite grain boundaries is the main reason for the change of da / dt of stress corrosion cracking. Based on the theory of the impurity segregation of atoms and the effect of hydrogen on the brittle fracture, various experimental phenomena are explained, and it is considered that the hydrogen-brittle fracture of impurity atoms in the grain boundary segregation and hydrogen interaction is the intergranular fracture type, while the pure hydrogen acts Hydrogen brittle fracture is a transcrystalline quasi-cleavage fracture type.