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(一)起源与钢的成分过去五十多年来,工业界不断应用以18%Cr-8%Ni为基础的304型不锈钢的经验指出:这种不锈钢以及它的一些变种,如304L(低碳)、316(加钼)、316 L(低碳)、321(加钛)、347(加铌)等、从成分看来是平衡得很好的。它们不但在广泛的环境介质中满足了抗腐蚀性能的要求,而且还有较好的加工性能和焊接性能。要想在抗还原性酸腐蚀和在NaCl溶液中抗氯化物应力腐蚀断裂方面取得显著的改进,则钢的成分必须作较大的变更,例如将镍含量提高到35%,并加入3.5%的铜。然后这样大量而费钱地增加镍对合金抗氯化物点腐蚀和缝隙腐蚀的能力并无显著有益的效果。
(I) Origin and Composition of Steel Over the past 50+ years, the industry has continually applied the experience of Type 304 stainless steel based on 18% Cr-8% Ni. This type of stainless steel and some of its variants, such as 304L Carbon, 316 (plus molybdenum), 316L (low carbon), 321 (plus titanium), 347 (plus niobium), etc., appear to be well balanced from the ingredients. They not only meet the requirements of corrosion resistance in a wide range of environmental media, but also have better processing performance and welding performance. To achieve significant improvements in antireduction acid corrosion and chloride stress corrosion cracking resistance in NaCl solutions, the composition of the steel must be greatly changed, for example by increasing the nickel content to 35% and adding 3.5% copper. There is then no significant beneficial effect of such a large amount of cost-intensive addition of nickel to the ability of the alloy to resist chloride and crevice corrosion.