Abstract:

Rational experiments based on Taguchi methods were designed according to the characteristics of difficult-to-machine material 0Cr18Ni9 stainless steel.Work hardening was discussed from the micro-hardness and microstructure.Micro-hardness distribution of the machined sub-surfaces was
got with the Vickers hardness measurement.And an empirical formula was established
for predicting the yield strength with hardness.
Microstructure of the hardened layer was observed with scanning electron microscopy.
The results show serious hardening that the degree of work hardening is more than
150%,and the depth of machining affected zone is more than 100μm.The yield strength
 follows a similar trend as that of the measured value of micro-hardness.Metallographic
observation shows that sub-hardened layer consists of the thermal-force influenced layer
and the force influenced layer,while the thermal-force influenced layer contains defects,
and it is easy to peel off. These results indicate that great changes have happened in the surface and subsurface after turning, and it is important to use reasonable cutting parameters to reduce cutting forces and cutting temperature and then reduce work hardening.

Key words: Austenite stainless steel, work hardening, micro-hardness, yield strength, microstructure

摘要：

针对难加工材料不锈钢0Cr18Ni9的特点，设计了合理的正交切削试验方案，从显微硬度与微观结构两方面研究加工硬化现象。借助维氏硬度计测量了车削加工后硬化层的硬度沿层深的分布，同时建立了利用硬度预测屈服强度的经验公式，再利用扫描电镜观察硬化层的微观结构。结果表明，硬化层的硬化程度在150%以上，切削影响层厚度在100μm以上，加工硬化现象严重，硬化层的屈服强度沿层深分布与硬度沿层深分布的趋势相同;金相观察发现，硬化层分为热力耦合影响层、力影响层，其中热力耦合影响层存在缺陷，很容易剥落。这些结果说明，车削表面在切削高温与力的作用下发生了很大的变化，采用合理的切削参数减小切削力、降低切削温度是减轻加工硬化程度的有效途径。
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关键词: 奥氏体不锈钢, 加工硬化, 显微硬度, 屈服强度, 微观结构