High Carbon Alloy Steels with Multiple Types of Ultra-fine Carbides and Their Characteristics

Under normal forging and annealing conditions, there are different ultra fine carbides (M3C, M23C6, M7Cj, M6C and MC) in high carbon alloy steels when alloy composition design is carried out properly. On the basis of carbides transformation orderliness, the alloy composition design of the high carbon alloy steels is conducted by phase-equilibrium thermodynamic calculation for Fe-Cr-W-Mo-V-C system. The nucleation and growth of new carbides, dissolution of previous partial carbides in these steels during annealing process, all these lead to ultra-fine distribution of carbides. Due to different crystal structures of carbides and different thermodynamics as well dynamics parameters of the carbides dissolution and precipitation, the range of quenching temperature of these steels is widened, and the good temper-resistance is obtained. The characteristics of heat treatment process and microstructure variance, and the carbides transformation for different temperature are explained by the phase-equilibrium component satisfactorily. Their bend and yield strength, flexibility and toughness all are advanced markedly comparing with that of kindred steels. Results of the applications have proved that the microstructure of ultra-fine carbides in these steels played importance roles in the enhancement of edginess and fatigue crack resistance of the die and knives.

The micro structure of high carbon low alloy steel for easy drawing

For better processing performance of high carbon low alloy steel wire rod,an investigation about the influence of cementite lamellar spacing on wire 'easy drawing' performance is completed.It is pointed out that too thin cementite lamellar spacing(<80 um) reduces the strain hardening level of wire drawing, and reduce the torsion performance of drawn wire at same time.For the wire or wire rod from industrial production,compared with the micro-structure with troostite,the micro-structure with sorbite or sorbite mixed with pearlite is more suitable to the drawing process with high reduction ratio.

High-temperature mechanical properties of near-eutectoid steel

The high-temperature mechanical properties of near-eutectoid steel were studied with a Cleeble-1500 simu- lation machine. Zero strength temperature （ZST）, zero ductility temperature （ZDT）, hot ductility curves, and strength curves were measured. Two brittle zones and one plastic zone were found in the temperature range from the melting point to 600℃. Embrittlement in zone I is caused by the existence of liquid film along dendritic interfaces. Ductility loss in zone Ⅲ mainly results from precipitates and inclusions as well as S segregation along grain boundaries. Pearlite transformation also accounts for ductility deterioration in the temperature range of 700-600℃. Moreover, the straightening temperature of the test steel should be higher than 925℃ for avoiding the initiation and propagation of surface cracks in billets.

Microstructure evolution of an ultra-high strength metal alloy with tempering temperature

Optical microscopy (OM) and transmission electron microscopy (TEM) were used to investigate the effect of tempering temperature on the experimental extra-high carbon steels. It is found that tempering reaction can reduce austenite content and influence the stability of the austenite. As-normalized microstructure is a mixture of twinned martensite and retained austenite. Tempered at 250 °C for 2 h, lath martensite can occasionally be found nearby the diffusionally decomposed austenite area. It also is found that tempering at 650 °C for 2 h, nanoparticles of carbides precipitate in the martensite and decomposed austenite. © The Nonferrous Metals Society of China and Springer-Verlag Berlin Heidelberg 2012.

Age-hardening of surface aged hardening alloy

Steel T8 treated by plasma surface decarburizing was alloyed by the Xu Tec process with Co,W and Mo. An alloyed layer of Fe Co W Mo with low carbon content was formed on the surface of the high carbon steel, thus an advanced gradient composite was produced. The specimens then were treated by the solution and aging treatments. The characteristics of age hardening of the alloying layer were studied. The hardness of the surface layer increases from HV200 to HV1 200 after the solution treatment at 1 190 ℃ and aging at 400 ℃ for 30 min. The results show that the surface aged high speed steel possesses not only high surface hardness, but also enough bulk strength. [

A Transmission Electron Microscopy Study of Plate Martensite Formation in High-carbon Low Alloy Steels

The martensitic microstructures in two high-carbon low alloy steels have been investigated by classical and automated crystallographic analysis under a transmission electron microscope. It is found that the martensitic substructure changes from consisting mostly of transformation twins for 1.20 mass% carbon （C） steel to both transformation twins and planar defects on {101}M for 1.67 mass% C steel. In the 1.67 mass% C steel it is further found that small martensite units have a rather homogeneous substructure, while large martensite units are more inhomogeneous. In addition, the martensite units in both steels are frequently found to be of zigzag patterns and have distinct crystallographic relationships with neighboring martensite units, e.g. kink or wedge couplings. Based on the present findings the development of martensite in high-carbon low alloy steels is discussed and a schematic of the martensite formation is presented. Moreover, whether the schematic view can be applied to plate martensite formation in general, is discussed.

稀土合金化对高碳高合金工模具钢的影响

莱氏体共晶碳化物粗大不均是严重影响高碳高合金工模具钢使役性能的不利因素。除了改变凝固冷却条件调控莱氏体共晶碳化物以外,国内外在利用稀土合金化手段改善共晶碳化物的形貌与分布方面也进行了大量研究,来提高高碳高合金工模具钢的热加工性能与韧性。本文简要介绍了高碳高合金工模具钢的生产工艺现状,阐述了高碳高合金工模具钢稀土合金化的研究进展,对比总结了稀土合金化研究现状中稀土元素的添加技术与添加量。另外,重点梳理了稀土合金化对高碳高合金工模具钢组织与性能的影响。最后,展望了稀土高碳高合金工模具钢的工业化生产与应用。

精炼钢水造渣分级管控的研究与应用

结合不同钢种精炼造渣特点和钢水进精炼期间不同的生产条件,以普碳低合金钢HRB400E系列、优质碳素高碳钢65#系列以及板坯普碳钢Q235B系列为例进行研究,在原先精炼造渣的基础上进一步实施精炼钢水顶渣造渣分级管控,通过对不同钢种、不同硫含量等条件下精炼造渣分级管控措施的落实,实现精炼造渣效率有效提升、钢材质量稳步提高、精炼系统成本有效降低,进一步推动炼钢系统精细化管理向好、向深发展。

Q235和Q345材料的异型管弯曲成型质量的仿真研究

由于管坯不同材料的力学特性的差异、热硬化指数、厚向异性系数以及延伸率都不同,使得不同强度钢材在弯曲成型过程中出现各种质量问题。为判断不同材料下不同截面大小的异型管弯曲不同角度成型时对管坯质量的影响,建立了Q235和Q345两种材料弯曲30°~90°的12种工况下的有限元模型。研究结果表明:同一截面尺寸的不同材料,对管坯中面高度缩减率和壁厚减薄率影响规律一致;不同截面尺寸大小的同一材料,其最大中面高度缩减率和最大壁厚减薄率数据相差甚大;临界弯曲角度为60°,超出临界弯曲角度,管坯截面尺寸小且大角度弯曲时,其最大壁厚减薄率呈急速加大趋势,此时严重影响管坯成型质量。

二次碳化物特征调控及其对高碳高合金马氏体钢耐磨性的影响

二次碳化物的尺寸、含量对高碳高合金马氏体钢的力学性能及耐磨性有着重要影响.本文采用扫描电子显微镜、透射电子显微镜和磨粒磨损实验等手段,研究了高碳高合金马氏体钢锻造及球化退火过程中二次碳化物的演变行为及其对高碳高合金马氏体钢力学性能及耐磨性的影响.结果表明:球化退火显著增加了锻造空冷态实验钢中二次碳化物的含量及尺寸;在奥氏体化过程中,二次碳化物通过钉扎晶界显著细化了奥氏体晶粒,同时二次碳化物的存在降低了马氏体中合金元素固溶量,进而有效提升了实验钢的冲击韧性.高硬度的微米级二次碳化物配合高韧性马氏体基体可有效阻碍磨粒切削并减轻磨损表面的微观断裂,进而提升实验钢的耐磨性.

Effect of Austempering–Partitioning on the Bainitic Transformation and Mechanical Properties of a High-Carbon Steel

The 1.1C-1.5Si-1.1Mn1.4Cr-0.5Mo-0.6Al-0.6Co （in wt%） steel was treated, respectively, by isothermal austempering process and newly developed austempering-partitioning-tempering process （A-P-T）. After austempering at 250, 280 and 300 ℃ for 38, 20 and 10 h, respectively, the sample microstructures were composed of bainitic ferrite plates and film-like retained austenite with thicknesses between 60 and 150 nm. The highest tensile strength of 2003 MPa and hardness value of 53.9 HRC were obtained for the steel after austempering at 250 ℃ for 38 h, resulting from the combining effect of super-saturated martensite decarburization and stabilization of bainitic formation. After A-P-T treating （heated at 300 ℃ for 8 h following water cooling, and then heated at 300 ℃ for 2 h following air cooling）, bamboo leaf-like martensite, primary and secondary bainites and retained austenite were observed. The thickness of the secondary bainitic ferrite plates formed during partitioning is much smaller than that of the primary bainite formed during 300 ℃ austempering. Samples subjected to A-P-T treatment showed improvement in ductility compared to that subjected to austempering.

稀土合金化高碳耐磨钢连续冷却转变曲线的建立及组织转变

采用金相显微镜、场发射扫描电镜和淬火膨胀仪研究稀土合金化高碳耐磨钢不同冷却速度条件下的转变组织、相变临界点和不同冷却速度下过冷奥氏体的连续冷却转变曲线(CCT曲线)。结果表明:相变临界点为Ac_(1)为742.6℃,Ac_(3)为816.5℃,Ms为307.0℃。当冷却速度小于0.4℃/s时,显微组织为少量铁素体+珠光体;当冷却速度为0.4℃/s时,显微组织为单相伪共析珠光体;当冷却速度大于0.5℃/s时,显微组织逐渐向马氏体转变;冷却速度高于4℃/s时,钢中仅有马氏体+残余奥氏体组织。

高速钢/结构钢双金属复合材料界面研究

采用镶铸法 ,以液固结合的方式制备了高碳钒系高速钢 /结构钢双金属复合材料。研究了不同结合条件下 ,双金属复合材料界面结构及形态。试验结果表明 ,镶铸是靠外层合金带入的过热热量来获得界面结合的 ,当外材与芯材在体积比大于 8.0的条件下 ,才有可能获得界面结合 ,其界面结合为扩散结合。复合材料界面结构由芯材扩散层、激冷凝固层、方向性生长层和胞状晶粒层组成。外层材料凝固时有明显的方向性生长 ,其液固相线推移速度对在液固结合条件下外层材料的凝固组织具有明显影响。当外材与芯材体积比为 1.2 5时 ,外层材料的凝固速度最快 ,出现了棒状伪共晶组织 ,随体积比的增长 。

低合金钢高浓度渗碳的组织与性能

探讨了低合金钢在８２０ ℃～８６０ ℃固体高浓度渗碳的工艺及其组织与性能。结果表明，高浓度渗碳工艺可在钢的表面形成大量细粒状、弥散分布的碳化物，使钢具有高硬度、高耐磨性。

碳含量对腐蚀条件下低碳高合金钢冲击磨损性能的影响

在冲击、腐蚀磨损条件下,对不同碳含量的新型衬板用低碳高合金钢的磨损行为进行比较,采用金相显微镜、扫描电子显微镜和X射线衍射仪观察分析合金组织、其亚表层金相组织及冲击腐蚀磨损表面形貌,对合金组织和在腐蚀环境下的冲击磨损机制进行探讨.结果表明:与含碳量为0.16%、0.25%的低碳高合金钢相比,碳含量为0.21%的低碳高合金钢在腐蚀环境下具有最佳的抗冲击磨损性能,其磨损机制以疲劳剥层为主.

铌微合金化高碳钢的连续冷却转变

在Geeble 1500热/力模拟试验机上测定了铌微合金化高碳钢与普通高碳钢变形后的连续冷却转变曲线,分析比较了它们的组织演变规律。实验结果表明,与普通高碳钢相比,含铌高碳钢的转变温度较高,A+P两相区的温度范围较大(在所测定的冷速下,温度范围均在100℃以上),且在相同冷速下,先共析铁素体的数量明显增多,而奥氏体晶粒较小。在本实验条件下,当冷速大于10℃/s时,含铌高碳钢转变后的珠光体片层间距较小;在冷速大于30℃/s时,其基体中出现贝氏体组织。

锰含量对衬板用低碳高合金钢组织和性能的影响

用光学金相显微镜、衍射仪及显微硬度计,研究了锰含量对衬板用低碳高合金钢组织和性能的影响。结果表明,当锰含量由2.0%增加到3.0%时,合金的退火态组织由上贝氏体+屈氏体转变为马氏体,淬火回火后均为单相板条马氏体组织。随锰含量的增加,硬度稍有增大,冲击韧度下降,均匀耐腐蚀性有所降低。含锰量为2%的低碳高合金钢达到了矿山用衬板的使用要求,从成本考虑,是更经济的。

V、N微合金化对高碳钢82B性能的影响

研究了V和V、N微合金化高碳钢82B固溶加热连续冷却和高温热变形连续冷却后的强韧性。结果表明,固溶加热连续冷却后,82B钢随钒含量的增加,强度增加、塑性降低,塑性主要受索氏体片层间距的影响。经高温热变形连续冷却后,与未热变形的相比,试验钢的强度和塑性均显著提高,索氏体团显著细化,钒氮同时加的82B钢强韧性最高,热变形连续冷却后性能提高的原因主要是索氏体团的细化和V(CN)的形变诱导析出。