Study on hardenability of large cross-sectional high strength medium-Mn forged steels

The hardenability of two large cross sectional high strength medium Mn forged steels were investigated using Jominy tests and nonlinear equation calculation model, and the effect of Mn element was discussed. The results show that the hardness of the steels is not less than 48HRC and 50HRC at a distance of 50mm from the quenching end, respectively, and keeps no decreasing trend. Moreover, the distance holding martensitic volume fraction of 50% in the steels is more than 1000mm and 3000mm based on the nonlinear equation calculation model, respectively. The addition of Mn improves the hardenability which meets the requirements for high hardenability of large cross-sectional components. In addition, the effects of annealing treatments on the tensile properties of the steels were investigated using uniaxial tensile tests at room temperature. Excellent combinations of tensile strength and total elongation are obtained through the annealing treatment at 600℃×4h, which is due to the occurrence of austenite reverse transformation, lowering the stability of austenite, thus, resulting in TRIP effect during the tensile deformation.     

75Cr1钢淬火硬度不均匀原因分析与改进措施

通过用户生产现场和实验室淬火试验对比,对厚规格75Cr1钢板（厚度≥8 mm）淬火硬度不均匀问题进行了研究。结果表明, 75Cr1厚钢板淬火硬度不均匀的主要原因是淬火时采用的普通32号机械油冷却能力较差,导致淬火后显微组织中除马氏体外还出现大量屈氏体。使用相同淬火介质,75Cr1钢板厚度越小淬火后硬度越容易均匀;淬火介质冷却能力越强,钢板淬火后硬度也越容易均匀。据此提出,对于厚75Cr1钢板,使用冷却能力更强的淬火介质或者调整75Cr1钢的化学成分提高其淬透性,均能使其淬火后硬度均匀。     

硼在钢中的作用及应用

通过对大量文献的归纳总结,就B对钢的淬透性、韧性、耐磨性影响机理及应用作了简要概述,当B含量在0.005%~0.0030%时淬透性较好,为保证B对淬透性的有效作用,常采用铝、钛降氧、固氮的方法;分析了B含量、加入方式、分布、热处理以及合金的复合作用等对韧性改善的作用;也分析了热处理和合金化对含B钢耐磨性的影响,认为B元素在钢中的应用前景广阔。     

薄板坯中钢微合金化对其性能的影响

从理论分析结果来看,钒、钛、铌、硼等微合金元素都能够满足在薄板坯连铸连轧上的生产,但其作用机理及强化强度受到其本身特性及工艺条件的影响而不同;钒、铌、钛可以通过细化晶粒和沉淀强化来提高强度,对抑制再结晶能力,表现为铌>钛>钒,而硼主要表现能显著提高钢的淬透性,硼微合金钢深加工方面性能显著。     

转炉-矩形坯连铸生产20CrMnTiH齿轮钢工业试验

本溪钢铁集团有限公司采用"铁水脱硫预处理→复吹转炉冶炼→LF→RH→矩形坯连铸→热送步进式加热炉→24架高刚度短应力线连轧机组→保温→精整包装"的工艺路线成功地试生产了20CrMnTiH齿轮钢.其产品Φ90～180 mm齿轮钢化学成分均达到窄范围控制指标,各项物理检验指标完全满足技术条件要求.     

关于干硬性混凝土试件制作方法的探讨

为了使干硬性混凝土试件制作更具有代表性,从制作过程中的密度控制、振动层数、振动时间与混凝土28天的标养强度的相关关系中,找出适合于干硬性混凝土试件的制作方法．     

淬透性细化分级8620H钢的热处理性能研究

通过对化学成分的微调实现8620H钢种的低、高淬透性分级,并研究其在副箱中间轴上的应用。结果可知,在相同的热处理工艺下,相较于低淬透性8620H钢副箱中间轴,高淬透性8620H2钢具有更深的有效硬化层深度和更高的心部硬度。此外,低淬透性8620H钢副箱中间轴的热处理工位节拍时间为25.5 min,而高淬透性8620H2钢工位节拍时间可缩短至20.5 min。但是,需要注意的是,在开发8620H2钢高淬透性零件的热处理工艺时,应综合考虑热处理的技术指标和热处理后的齿部精度。     

Cr-Ni-Mo系齿轮钢端淬过程模拟及淬透性预测

通过端淬试验测定了20Cr、20CrMo和20CrNiMo钢的淬透性曲线,分析了合金元素对淬透性的影响。利用Abaqus软件和Maynier组织预测模型,对3种成分钢的淬透性曲线进行了模拟计算。结果表明,20Cr、20CrMo和20CrNiMo 3种齿轮钢的淬透性依次降低;试验测定值与模拟计算值基本吻合,表明此种方法可以用来预测齿轮钢的淬透性曲线。     

ON THE HARDENABILITY OF AN INTERCRITICALLY HEAT TREATED MICROALLOYED STEEL

Dual phase steel has become an important engineering material to be used in structural and automotive applications due to its good combination of strength, ductility, and formability. In this study, hardenability of a low carbon and microalloyed steel was investigated by using the standard Jominy End Quench Test at four different quenching temperatures. Three steel specimens were quenched from the intercritical region at 737°C, 754°C, and 779°C separately, whereas one of them was tested at 900°C, in the fully austenitic region. After finishing the Jominy test, metallographic examination of the samples was carried out to see the variation in the microstructure through the length of the steel. And also, hardness measurements were made through the length of the samples. Results brought out that there was a strong decrease in the hardness of the tested samples after a depth of 5 mm from the quenched end.     

硅、锰对中碳CRMo低合金钢淬透性和耐磨性的影响

中碳CrMo低合金钢作为一种耐磨材料广泛应用于球磨机衬板,但因其淬透性有限,限制了其在大型衬板上的使用,通过研究硅,锰含量对中碳CrMo低合金钢淬透性的影响,发现适当设计硅,锰含量可使该钢种的耐磨性大大提高。