HXN5型机车柴油机曲轴校直后应力消除方案优化

HXN5型内燃机车用6 000马力中速柴油机合金钢制造的曲轴热处理技术要求与以往所熟悉的机车柴油机合金钢曲轴有很大的不同,它的预备热处理要求采用喷雾正火加高温回火,最终表面热处理采用氮化.曲轴成品要求全长最大跳动量不超过0.06 mm,这个要求高于以往制造的机车柴油机曲轴.通过对锻钢曲轴消除应力的机理的探讨,提出了应力消除的最佳方案,并据此对校直后消除应力的工艺方案进行了试验研究.结果表明:曲轴消除应力热处理保温温度采用在正常热处理的回火温度以下20℃是合适的;采用雾冷正火后校直,再进行回火的工艺安排是可行的.通过工艺优化,解决了该型曲轴在校直后由于应力消除不彻底而造成的变形超差问题.

Optimization of the Stress Relief Operation for Crankshaft of HXN5 Locomotive Diesel after its Straightening Process

Quite different from the conventional crankshaft for locomotive diesel,the alloy steel crankshaft on the 6000HP medium speed diesel engine for HX_N5 diesel locomotive requires a spray normalizing and high temperature tempering as pre - heattreatment and a nitriding process as the final surface heat treatment. The allowable Max.runout of a finished crankshaft at whole length is no more than 0.06mm,which is stricter than the requirements on conventional locomotive diesel crankshaft.By studying the mechanism of stress relief for a forged steel crankshaft,a preferred stress relief process is developed,which is subsequently allied to stress relief testing for crankshaft after straightening process.Testing results indicate that it is applicable and practical to perform crankshaft straightening after a fine spray normalizing,followed by a tempering process when the holding temperature for stress relief treatment is kept at 20℃below the normal tempering temperature.The deformation deviation of a crankshaft due to incomplete stress relief after its straightening is eliminated by means of process optimization.