合金元素對射出成形不銹鋼切削性之影響

Abstract

金屬粉末射出成形316L不銹鋼，已廣泛地用來製造形狀複雜與抗腐蝕之零件，然而不銹鋼材料加工硬化速率高、熱傳導係數低與熱膨脹係數大之特性，大大地降低了不銹鋼的切削性，並且粉末燒結之零件含有孔隙，會在切削過程當中造成刀具之振動而加速刀具之磨耗，影響刀具壽命；MnS常被用來添加於不銹鋼中來改善切削性，但是MnS的添加卻會造成不銹鋼的抗腐蝕性降低，有鑑於傳統粉末冶金業界以316LSC與304LSC系不銹鋼來改善切削性與抗腐蝕性，其化學組成含有2wt% Cu與1wt% Sn，但射出成形原料供應商卻尚未提供此類合金粉末，因此本實驗嘗試添加MnS、Cu、Bronze粉於射出成形316L不銹鋼中以比較其切削性，並且觀察其抗腐蝕性。 實驗結果得知添加Cu於316L不銹鋼中可以降低切削力，而以3wt%的添加量為最佳；以裂解氨氣氛燒結之316L不銹鋼也可降低切削力，但抗腐蝕性較差；Cu添加於316L不銹鋼中可減少碳化鉻與氮化鉻的生成，因而能提升不銹鋼的抗腐蝕性。添加Bronze時切削性佳卻弱於添加3wt% Cu之效果，但抗腐蝕性較佳，這是因為Bronze含有Sn的成分，Sn可有效地阻止氮與鉻的結合而減少氮化鉻的生成。

The metal injection molded 316L stainless steels are good in corrosion resistance but they are faced with many difficulties in machining compared with carbon steel. The reason is that work-hardening speed is high and thermal conductive is low. In this research, we improve the machinability of stainless steel by add Cu, MnS, Bronze element. The experimental result shows that adding Cu can reduce the cutting force of the 316L stainless steel, and the best adding amount is 3wt%Cu. The associated ammonia sintering atmosphere can reduce the cutting force, but it is relatively bad corrosion resistance. The best corrosion resistance is bronze alloyed stainless steel because tin provides a barrier to both nitrogen and chromium diffusion.