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日本日立公司开发了一种耐海水、高强度、高韧性并且焊接性优良的15Cr—6Ni—2Mo—Nb— V—N马氏体铸钢,其化学成分(wt％)C0.02～0.07、Si0.2～0.6、Mn0.3～08、Ni4.5～6.8、Cr15. 2～16.5、Mo1.8～2.8、Nb0.05～0.3和/或V0.05～0.3、N0.055～0.09、余为Fe和杂质。因为Ni能有效地增加淬透性提高钢强度,形成残余奥氏体而增加韧性并提高焊接性,少于4.5％效果不足而多于6.8％则使强度降低,故限定为4.5～6.8％;Cr是提高淬透性并赋予钢耐海水性的重要元素,少于15.2％效果不足而多于16.5％则由于析出δ—铁素体而脆化;Mo能提高钢强度和耐海水性,但超过2.8％时会使钢的韧性降低;Nb的V是提高钢的耐蚀性、强度和韧性的重要元素,但超过0.3％反而会损害韧性;N是提高强度、耐蚀性和韧性的有效元素,但超过0.09％时因容易在铸件中形成气孔反而会损害韧性。因此规定了上述成分范围。
Japan’s Hitachi has developed a 15Cr-6Ni-2Mo-Nb-V-N martensitic cast steel resistant to seawater, high strength, high toughness and excellent weldability with a chemical composition (wt%) C0.02 to 0.07, Si0.2 to 0.6, Mn0.3 to 08, Ni4.5 to 6.8, Cr15.2 to 16.5, Mo1.8 to 2.8, Nb0.05 to 0.3 and / or V0.05 to 0.3, N0.055 to 0.09, The remainder is Fe and impurities. Because Ni can effectively increase the hardenability of steel to improve the strength, the formation of retained austenite to increase toughness and improve weldability, less than 4.5% of the effect of less than 6.8% will make the strength decreased, it is limited to 4.5 to 6.8%; Cr is an important element for improving hardenability and imparting seawater resistance to steel. Less than 15.2% of the effect is insufficient and more than 16.5% is embrittled by the precipitation of δ-ferrite. Mo improves the strength and seawater resistance of steel. However, Above 2.8%, the toughness of the steel is reduced. Nb is an important element that improves the corrosion resistance, strength and toughness of the steel. Exceeding 0.3% of the steel deteriorates the toughness. N is effective in improving strength, corrosion resistance and toughness Element, but more than 0.09% due to the formation of pores in the casting but will adversely affect the toughness. Therefore, the above-mentioned composition range is stipulated.