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通过研制加氮强化的奥氏体不锈钢,而发展了一批在性能上完全不同于常规的 AISI300系列不锈钢的材料,它们具有重要的实用性能。元素氮有多种非常重要的功用,它不仅使钢的室温性能获得强化,而且,氮的添加也提高了钢在负温度下的屈服强度。在可产生点蚀的腐蚀介质中,氮(如钼和铬)可以提高钢的耐侵蚀性能。在允许用氮合金化钢中,添加小于6%的镍或添加硅可以提高钢的抗穿晶应力腐蚀开裂能力。添加氮,可以阻止碳的迁移,因此,即使是碳含量为0.06%的钢,其焊缝区也很少有碳化物沉淀析出。在四种商业合金中都应用了这些引人注目的特性,使得每种合金的特别重要的性能都达到了最佳值。用于四种成分母材焊接的填料敷层需要调整其成分,以便在奥氏体基体中出现铁素体组织。为了最大限度地降低气孔的发生率,还降低了氮含量。使其产生两相组织所添加的氮含量通常足以获得与母材等强的焊接件。在气焊中,为了防止因母材含量高而产生气孔,需要采用诸如降低焊接速度或重熔工艺一类的特殊措施。
Through the development of nitrogen-enriched austenitic stainless steels, a number of materials that are completely different in performance from conventional AISI 300 series stainless steels have been developed and have important practical properties. Elemental nitrogen has many important functions that not only enhance the room temperature properties of steel, but also increase the yield strength of steel at negative temperature. Nitrogen, such as molybdenum and chromium, can improve the erosion resistance of steel in corrosive media that can generate pitting corrosion. Addition of less than 6% nickel or addition of silicon to nitrogen-alloyed steels may increase the resistance of the steel to transgranular stress corrosion cracking. The addition of nitrogen prevents the migration of carbon, so that even in steels with a carbon content of 0.06%, there is very little carbide precipitation in the weld zone. These compelling features have been applied to all four commercial alloys, resulting in the optimal performance of each alloy’s particularly important properties. The filler coating used for the welding of the four constituents of the base metal needs to be adjusted for its composition so that the ferrite structure appears in the austenitic matrix. In order to minimize the occurrence of stomata, the nitrogen content is also reduced. The resulting nitrogen content added to the two-phase structure is generally sufficient to obtain weldments that are as strong as the base metal. In gas welding, in order to prevent the occurrence of porosity due to the high content of the base metal, special measures such as lowering the welding speed or remelting process are required.