Abstract

The decarburization behavior of a spring steel 60Si2MnA at 700 °C to 900 °C was examined. It was observed that after holding for 20 minutes in 20 pct H₂O-N₂, thick ferrite layers developed within 750 °C to 877 °C with a maximum thickness of about 100 μm observed at 805 °C to 825 °C, while the ferrite layers were much thinner at 900 °C and 700 °C. Carbon permeability analysis and theoretical calculation were conducted to assess the possibility of forming a ferrite layer. In the permeability analysis, several factors were considered: (1) carbon concentration at the steel surface, which was very likely determined by reaction equilibrium between FeO and dissolved carbon in steel, (2) carbon solubility in ferrite which had a maximum value at about 715 °C, and (3) carbon diffusivity in the ferrite phase. In the ferrite layer thickness calculation, the contribution from carbon diffusion in the austenite phase was also taken into account. While the carbon permeability analysis and ferrite layer thickness calculation showed good successes in predicting the pattern of ferrite layer thickness change with temperature, under the assumption of FeO-ferrite equilibrium the calculated ferrite layer thicknesses at 780 °C to 840 °C did not match the observed values well. Factors contributing to the discrepancy were discussed.

中文翻译：

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在700°C至900°C下在20 Pct H 2 ON 2中使60Si2MnA脱碳

摘要

研究了弹簧钢60Si2MnA在700°C至900°C下的脱碳行为。据观察，在20保持20分钟后PCTħ ₂ O-N ₂，内750℃发展到877℃，约100的最大厚度厚铁氧体层μ在805°C至825°C时观察到m，而在900°C和700°C时，铁素体层更薄。进行了碳渗透性分析和理论计算，以评估形成铁素体层的可能性。在渗透性分析中，考虑了几个因素：（1）钢表面的碳浓度，这很可能是由FeO和钢中溶解的碳之间的反应平衡决定的；（2）在铁素体中的碳溶解度的最大值约为715°C，以及（3）铁素体相中的碳扩散率。在铁素体层厚度的计算中，还考虑了碳在奥氏体相中扩散的贡献。尽管碳渗透率分析和铁素体层厚度计算在预测铁素体层厚度随温度变化的模式方面取得了成功，但在FeO-铁素体平衡的假设下，计算得出的780°C至840°C的铁素体层厚度不符合观察值很好。讨论了导致差异的因素。