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本文研究了18Cr2Ni4WA钢的中温块状铁素体组织(α_m)、贝氏体(B)及其分别与马氏体混合组织(α_m+M)、(B+M)的强韧性及抗疲劳裂纹扩展的性能。研究指出: 低温回火条件下,α_m的强韧性低于B及M,且α_m的存在降低了(α_m+M)混合组织强韧性。但(α_m+M)的疲劳裂纹扩展门槛值△K_(th)随α_m量增加而提高。各种组织因素对疲劳裂纹亚临界扩展速率无明显影响。(B+M)的塑性随B量增加呈线性上升。当B<40%时,B的存在有助于(B+M)强度的提高;B>40%后,才逐渐出现下降的趋势。室温冲击时,B比(B+M)具有较高的韧性;当试验温度低于-40℃后,出现相反的结果。α_m及B具有较高的抗回火性。高温回火条件下,单一α_m的σ_(0.2)略有提高。(α_m+M)及(B+M)的σ_b随α_m或B量的增加呈线性上升。无论回火温度高或低,α_m的存在均降低(α_m+M)的屈强比;而B的存在,只有当其体积分量超过80%以后,屈强比才出现明显下降。当冲击温度高于-80℃时,α_m及B的存在分别降低(α_m+M)及(B+M)的强韧性;但冲击温度低于-80℃后,却出现相反结果。
In this paper, the toughness and fatigue crack resistance of α Cr, bainite (B) and mixed mixed martensite (α_m + M) and (B + M) in 18Cr2Ni4WA steel were studied. Extended performance. The results show that the toughness of α_m is lower than that of B and M under the conditions of low temperature tempering, and the existence of α_m reduces the toughness of (α_m + M) mixed microstructure. However, the fatigue crack growth threshold △ K_ (th) of (α_m + M) increases with the increase of α_m. Various organizational factors have no significant effect on the subcritical fatigue crack growth rate. The plasticity of (B + M) increased linearly with the increase of B content. When B <40%, the presence of B contributes to the increase of (B + M) intensity; When the impact at room temperature, B than (B + M) has a higher toughness; when the test temperature is below -40 ℃, the opposite result. α_m and B have a higher anti-tempering. Under the conditions of high temperature tempering, σ_ (0.2) of a single α_m slightly increased. (α_m + M) and (B + M) σ_b increases linearly with the increase of α_m or B. No matter the tempering temperature is high or low, the existence of α_m decreases (α_m + M) yield ratio; while the presence of B only shows a significant decrease in yield ratio when its volume fraction exceeds 80%. When the impact temperature is higher than -80 ℃, the presence of α_m and B decreases the strength and toughness of (α_m + M) and (B + M) respectively. However, the opposite result occurs when the impact temperature is lower than -80 ℃.