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系统研究了LF+VD精炼工艺、钢锭模设计、氩气保护浇注工艺、大型钢锭高温扩散工艺、锻造工艺、淬火工艺及高温回火工艺等因素对718钢大型预硬化模块材料纯净度和硬度均匀性的影响规律。结果显示:LF和VD精炼过程中炉渣碱度分别保持在3.5～4.0和3.0～3.5,精炼后钢中w[S]控制到0.003%,T[O]为12×10-6;28t钢锭模尾锥形状和入口倒角优化设计后,尾部夹杂废品率由6.81%降低到1.55%;通过试验确定氩气流量按4～8m3/h控制;大型钢锭高温扩散后,模块低倍组织的偏析和硬度偏差分别由≤3.0级和≤5.0HRC提高到≤2.0级和≤3.5HRC;采用FM法代替平砧拔长,模块低倍组织疏松和超声波探伤检验分别由≤3.0级和C/d提高到≤2.0级和D/d;采用水-空控时淬火和电加热回火炉回火对规格为650mm×1 080mm的模块进行预硬化处理,模块横断面硬度偏差≤3.5HRC。
The effects of LF + VD refining process, ingot mold design, argon protection pouring process, high-temperature ingot diffusion process, forging process, quenching process and high temperature tempering process on the purity and hardness of 718 steel pre-hardened module The law of sexual influence. The results show that the basicity of slag in LF and VD refining process is kept at 3.5-4.0 and 3.0-3.5, respectively. After refining, w [S] is controlled to 0.003% and T [O] is 12 × 10-6; 28t ingot mold Tail cone shape and the entrance chamfer optimization design, tail waste rejection rate decreased from 6.81% to 1.55%; determined by the test argon flow 4 ~ 8m3 / h control; large ingot high temperature diffusion, the module microstructure segregation and The hardness deviation was increased from ≤3.0 and ≤5.0HRC to ≤2.0 and ≤3.5HRC, respectively. The FM method was adopted to replace the anvil drawing. The low magnification of module and the ultrasonic testing were improved from ≤3.0 and C / d to ≤2.0 and D / d; pre-hardened with a water-air quenching and electric heating tempering furnace tempering the module with a specification of 650mm × 1 080mm, the module cross section hardness deviation ≤ 3.5HRC.