热处理对含铬低碳钢组织与性能的影响  

Effect of heat treatment on microstructure and mechanical properties of low carbon chromium steel

作　　者：李国宝[1] 田世永[1] 王勇[1] 

机构地区：[1]济钢集团有限公司,山东济南250101

出　　处：《金属热处理》2012年第5期46-49,共4页Heat Treatment of Metals

摘　　要：研究了低碳含铬钢950℃淬火后650℃回火,不同的保温时间下,Cr对低碳合金钢调质后性能的影响,并和不加Cr相同成分的钢作了对比。研究发现,当保温时间以2.5 min/mm计算时,加Cr钢的力学性能低于不加Cr同成分的钢,金相组织观察发现Cr能够有效提高低碳合金钢的淬透性,淬火后即使钢板的心部也能获得贝氏体组织,为后续的回火做好组织准备。然而在回火后容易形成M23C6及M7C3碳化物,其稳定性较差,容易聚集长大,且形态为条状,拉伸时容易弯曲破裂,严重破坏钢板的连续性,降低钢板的强度及塑性。对不同回火保温时间的含Cr钢的二次相粒子析出行为研究发现,以1 min/mm计算保温时间时,没有发现含Cr碳化物的析出,但随着保温时间的增加,Cr钢中的含Cr碳化物快速析出,并迅速长大,尤其是以3 min/mm计算保温时间下,含Cr碳化物尺寸已经达到了300 nm。因此对含Cr低碳合金钢,必须采用合适的调质工艺,适当缩短回火保温时间,以降低碳化物的聚集长大,避免回火后强度和塑性的同时降低。Effect of Cr on microstructure and mechanical properties of the low carbon alloy steel containing Cr was investigated under different holding time tempered at 650 ℃ after quenching at 950 ℃ and compared with that of the steel with similar chemical composition without adding Cr. The results show the mechanical properties of the steel containing Cr are lower than that of the steel without Cr when the tempering time calculated by 2.5 min/mm. Cr can improve the hardenability of the steel obviously, as a result, the center of steel can obtain bainite structure preparing for tempering, but Cr can form carbide as M7 C3 or M23 C7 in tempering process. These carbides are unstable and easily coarsening, their strip shapes destroy the continuity of steel, which resulting the decrease of strength and toughness. Precipitation behavior of carbides in the steel containing Cr was investigated under different tempering time. Carbides in the steel containing Cr is not observed when temper holding time calculated by 1 min/mm, however, they precipitate and grow up quickly with the increase of holding time, and the size of carbides grows up to 300 nm when holding time calculated by 3 min/mm. So a suitable quenching and tempering process should be adopted for the low carbon alloy steel containing Cr through controlling the tempering time in order to restrain aggregation and growth of carbides and prevent the decrease of strength and toughness after tempering.

关 键 词：低碳合金钢 调质 淬透性 碳化物 

分 类 号：TG142.1[一般工业技术—材料科学与工程]