亞共析石墨化易切削鋼的組織及力學性能

亞共析石墨化易切削鋼的組織及力學性能Microstructure and Mechanical Property of Graphitized Hypoeutectoid Free Cutting Steel

石墨易切削鋼是順應易切削鋼無鉛、低硫這一發展趨勢而提出的。本文分別對經過石墨化處理、固溶處理的亞共析石墨化易切削鋼的組織、性能進行了測試、分析。結果表明，在石墨化處理后，其組織主要是由石墨和鐵素體組成；石墨粒子不僅在晶界上析出，而且也在晶內析出；其分布較均勻，平均尺寸小于10μm，大小均勻；屈強比低(0.59~0. 63) ,可表現出較高的冷成形性能；在固溶處理后，鋼中以石墨形式存在的碳完全消失，性能可以恢復到石墨化處理前的水平，屈強比增大到0.75~0.77，可以滿足機械結構用鋼對屈強比的要求。

Development of low-sulfur and Pb-free free cutting steel is significant because the use of S or Pb free-cutting steel can result in serious pollution. The hypoeutectoid graphitized free cutting steel was proposed. In this paper microstructure of the steel(after graphitization and solution treatment) was observed using OM and SEM，mechanical properties were tested using universal material testing machine.The results show that after graphitization treatment microstructure of tested sample consist of graphite and ferrite,the graphites homogeneously distributed in grains and at grain boundaries, size of the graphite was less than 10μm, the yield ratio of the steel was low(0.59~0.63), this shows that tested sample has high cold formation. After solution treatment graphite in tested sample disappeared，the yield ratio of the steel was 0.75~0.77，this could meet common demand of the yield ratio of steel for machine structure purpose.

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