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图1所示的高强度螺栓是用LJ16Mn普通低合金钢制成的,经激烈淬火及低温回火处理,得到低碳马氏体组织。对机械性能的要求是:σ_b≥100kgf/mm~2;σ_(0.2)≥80kgf/mm_2;δ_6≥9%,ψ≥30%。过去曾采用盐炉加热,900～920℃,10～15%NaCl水溶液淬火,200℃回火处理这种螺栓,处理后表层有2～3mm厚淬硬层。但在大批生产中,为了提高生产效率,并将热处理工序安排在螺栓生产流水线上,实现生产过程机械化,我们对这种螺栓进行了中频感应加热淬火的研究。一、中频感应加热设备
The high-strength bolts shown in Fig. 1 are made of LJ16Mn ordinary low-alloy steel and are subjected to intense quenching and tempering at a low temperature to obtain a low-carbon martensite structure. The requirements of the mechanical properties are: σ_b ≥ 100kgf / mm ~ 2; σ_ (0.2) ≥ 80kgf / mm_2; δ_6≥9%, ψ≥30%. In the past, it was heated in a salt furnace at 900-920 ° C and quenched with 10-15% NaCl aqueous solution and tempered at 200 ° C. The treated surface had 2 ~ 3mm thick hardened layers. However, in a large number of production, in order to improve production efficiency, and the heat treatment process is arranged in the bolt production line to mechanize the production process, we conducted a research on this kind of bolt by IF induction heating and quenching. First, the IF induction heating equipment