以中碳钢42CrMo为试验钢,通过建立300mm×400 mm连铸大方坯凝固传热模型,确定合理压下区间4#～7#辊压下量分别为"1 mm-2 mm-3 mm-1mm",并进行工业试验.试验结果表明,轻压下工艺对铸坯凝固各组织占比影响不大,但可明显改善中心致密性和偏析.铸坯芯部最大疏松点尺寸由1106 μm×608 μm缩小至600 μm×334μm,横截面上碳偏析指数范围由0.889 ～ 1.095缩小至0.962 ～ 1.064.轻压下工艺可有效改善铸坯内部质量.

通过不同的热处理制度:800、820℃低温淬火+600℃回火,880℃+860℃两次淬火+600℃回火和860℃一次淬火+600℃回火,对40CrMnMo钢进行热处理试验,并研究了三种热处理工艺对40CrMnMo试验钢组织和性能的影响。结果表明,三种热处理工艺的试验钢抗拉强度相近（936～951 MPa）,组织为回火马氏体+铁素体,采用800、820℃低温淬火+600℃回火热处理工艺,试验钢的冲击功最高（65～69J）。

某公司生产的高强度弹簧钢60Si2CrVAT圆棒材,出厂之前检测力学性能时发现部分试样抗拉强度及屈服强度满足标准要求,但断面收缩率及断后伸长率指标均明显低于标准要求.利用体视显微镜及扫描电子显微镜(SEM)对力学性能异常试样断裂原因进行了分析.结果表明,性能不合格试样属于异常断裂,试样制备过程中表面产生加工硬化、甚至出现微裂纹是引起拉伸试样异常断裂的主要原因.改善样坯热处理后的加工方式可消除此类异常断裂现象.

With taking the technology measures such as increasing Mn content in steel from 1. 55% ~ 1.65% to 1,75% 〜1. 85% , replacing 0. 20% ~0. 25% Ni in steel by 0. 25% 〜0. 35% Cr, adding 0. 01 % ~0. 04% Ti for microalloying, controlling [ N] ≤80 x 10-6and [O] ≤15 x 10-6by RH vacuum treatment, decreasing casting secondary cooling water rate from 0. 11 L/kg to 0. 08 L/kg and modifying water distribution ratio to increase temperature of bloom at outlet from 620 ~ 680 ℃ to 700 ~ 750 °C , bloom cooling with shielding and bar products slow cooling, the production cost of R3 grade mooring chain steel is reduced, the longitudinal cracks of 350 mm x 470 mm cast bloom are eliminated and the strength and the toughness at -20 ℃ of products all meet the requirement of standard.

The Φ140 mm bar of steel(0.21C,1.45Mn,1.44Cr,1.21Ni,0.49Mo,0.07Nb) for R4 offshore mooring chain was produced at Daye Steel by 60 t EBT arc furnace-70 t LF refining+RH vacuum degassing-3 strand 350 mm×470 mm billet caster-850 primary mill blooming-750 semi-continuous mill rolling process.The results showed that with LF refining for 45 min,feeding Al wire and Ca-Si wire deoxidizing,then ≤66.65 Pa RH vacuum degassing for 20min + soft argon blowing for ≥ 10 min,the oxygen content in finished products of steel for offshore mooring chain was 14.8×10~(-6),nitrogen content 69.8×10~(-6),hydrogen content 1.2×10~(-6),segregation and porosity rating were 0.5,inclnsion rating 0~1,impact energy at(-40) ℃ ≥100 J and each index met the requirement of standard.

分析和研究了105炉SCM318H、SCM322H、SCM420KC、SCM822H、SCr420K等汽车用低碳齿轮钢的20tLFVD精炼终渣碱度、终Al含量和真空时间对钢中氧含量的影响。实践操作结果表明,采用白渣操作,控制终渣碱度不低于3,终Al含量≥0.22%、真空处理时间不低于25min,可使低碳齿轮钢的氧含量稳定地≤15×10-6,平均氧含量为11.58×10-6。