50t电炉-LF-VD流程生产SAE8620H齿轮钢淬透性的控制

对影响采用50 t电炉-LF-VD工艺生产SAE8620H齿轮钢的淬透性的冶金因素进行分析;重点关注生产过程中化学成分C含量的变化规律,分析工艺过程对化学成分C含量的控制精度的影响因素并进行研究优化。通过实施设计子钢号化学成分、缩窄化学成分控制范围、对工艺关键位置加强全过程控制等措施后,钢中Mn、Cr、Ni均控制在较窄的范围内,w(C)波动控制在0.03%以内,从而较好地控制了SAE8620H齿轮钢淬透性和淬透性带宽。     

基于Deform的带状组织对齿轮钢淬火变形影响数值模拟

运用相变仪对SAE8620H齿轮钢试样的淬火膨胀性能进行测定,研究了带状组织对钢各向异性的影响,通过Deform软件并考虑材料的各向异性参数来模拟带状组织对齿轮钢淬火性能的影响。结果表明,含有带状组织的SAE8620H钢淬火时膨胀量呈现明显各向异性,且垂直于轧制方向的膨胀量明显大于平行轧制方向,4×10 mm试样横向和纵向膨胀量相差11μm,而有限元模拟表明齿轮钢淬火后横纵向试样膨胀量相差13μm,实测值和模拟值比较吻合。     

SAE8620H齿轮钢末端淬透性控制研究

通过现场试验,研究了结晶器电磁搅拌强度对齿轮钢成分均匀性的影响。结果表明:采用合适的MEMS参数,能够改善连铸坯横截面成分偏析,控制钢的末端淬透性带宽,SAE8620H齿轮钢的圆钢横截面碳偏析指数由原来的0.92~1.08降至0.97~1.04;末端淬透性带宽由8 HRC降至5 HRC,实现了淬透性窄带化,满足了客户对齿轮钢淬透性带宽的需求。     

齿轮钢SAE8620 H高温变形行为及热加工图

通过高温压缩试验研究齿轮钢SAE8620H在950~1100℃、应变速率0.01~10 s-1条件下的高温变形行为.该合金钢的流动应力符合稳态流变特征,流变应力随变形温度升高以及应变速率降低而减小,其本构方程可以采用双曲正弦方程来描述.基于峰值应力、应变速率和温度相关数据推导出SAE8620H高温变形激活能Q=280359.9 J·mol-1.根据变形量40%和60%下应力构建该齿轮钢的热加工图,通过热加工图中耗散值及流变失稳区确定其热变形工艺参数范围.SAE8620H钢在在变形程度较小时宜选取低的应变速率进行成形,而在变形程度大时则要选取低温低应变速率或者高温高应变速率.      

美标SAE8620H齿轮钢的研制

莱钢特钢厂通过采取精料、电炉冶炼全程泡沫渣、LF精炼和VD真空脱气等措施,生产出的SAE8620H钢具有淬透性带窄、纯净度高、晶粒细小均匀、表面质量优良等优点,完全能够满足高性能汽车齿轮的需要.     

齿轮钢XC-01等温退火工艺对组织性能的影响

渗碳齿轮钢等温退火处理可以获得均匀、稳定的组织和硬度,对下游客户的冷锻加工性能有显著改善,提高了加工精度,并能减少齿轮最终渗碳淬火热处理变形。介绍了冷锻加工用渗碳齿轮钢的退火工艺、技术及产品性能。     

渗碳齿轮代表性试样心部硬度的研究

介绍了宝钢工程技术公司渗碳齿轮代表性试样心部硬度出现的问题,分析了影响心部硬度的因素,提出了相应的改进措施.     

热处理工艺对低碳齿轮钢带状组织评级的影响

试验分析了3种低碳齿轮钢(20Cr Mn Ti H、20Cr Mo H和SAE8620H)在正火、完全退火、等温退火等工艺处理后带状组织的变化情况,结果显示低碳齿轮钢在不同热处理制度下的带状组织存在明显差异。完全退火处理后钢材带状组织级别较热轧状态偏高;正火处理与等温退火处理后钢材的带状级别与热轧状态无明显差别。不易产生贝氏体组织的Cr-Mn-Ti系低碳齿轮钢,可以在热轧状态或正火处理后进行带状组织评级;Cr-Mo系和Cr-Ni-Mo系低碳齿轮钢,应进行完全退火或等温退火处理消除贝氏体等非平衡态组织后再进行带状组织评级。     

钒对高温渗碳SCM420H齿轮钢组织和淬透性的影响

对高温渗碳SCM420H齿轮钢进行了钒微合金化处理,并对钢中组织及淬透性进行了研究。结果表明：SCM420H齿轮钢中V含量和N含量应控制范围分别在0.03%～0.05%和0.012%～0.018%。MN(M=Ti,V)在966℃时析出并在559℃时向M(C,N)发生转化,常温时的M(C,N)质量百分数约为0.049%。将加热温度控制在1 200℃±20℃,在预热段（室温升至850℃左右）加热时间控制在120 min内,在940～980℃高温渗碳保温6 h后,圆钢的带状组织控制在1.5～2级,奥氏体晶粒稳定在7.5～8级,M(C,N)主要为能起到钉扎晶界、细化奥氏体晶粒的纳米级球状V(C,N)。将连铸结晶器电磁搅拌强度参数调整为150 A,2.5 Hz,铸坯拉速为0.85 m/min,浇铸过热度为15～30℃,碳含量偏差值可控制在0.01%,碳含量的均匀化有利于淬透性的窄带化控制,钒微合金化后,试样的淬透性硬度值（HRC）最高为37,最低为35,淬透性带宽硬度值（HRC）≤3。     

齿轮钢晶粒尺寸对淬透性的影响

以20CrNiMoH齿轮钢为实验对象,研究了齿轮钢不同晶粒尺寸对其淬透性的影响。在同一棒料上截取端淬试样,经925、950、980、1 000和1 050℃等不同奥氏体化温度处理后开展末端淬火实验,结果发现经不同奥氏体化温度处理的试样淬透性能差距较大。进一步研究发现,20CrNiMoH齿轮钢试样淬透性能的不一致主要源自于不同试样晶粒尺寸的差别。20CrNiMoH齿轮钢试样经不同奥氏体化温度处理后,晶粒尺寸和长大趋势不同,晶粒尺寸长大会推迟过冷奥氏体相变发生,从而保持奥氏体的稳定性,提高齿轮钢的淬透性。此外还定量研究了20CrNiMoH齿轮钢晶粒度等级同淬透性硬度的关系,发现20CrNiMoH钢晶粒度级别提高1级,J5、J9和J15处端淬硬度值分别下降约1.9HRC、4.0HRC和1.3HRC,J9处端淬硬度受晶粒度的影响最为显著。     

含硫齿轮钢SAE8620H热轧棒材夹杂物

 以EAF电炉—LF精炼炉—VD真空精炼炉—LF精炼炉—CC连铸工艺流程生产含硫齿轮钢SAE8620H热轧棒材,利用光学显微镜、扫描电镜和能谱仪分别对棒材横纵截面的边缘部位、1/2半径处和中心部位的夹杂物进行了检测,综合分析了夹杂物的尺寸、数量、分布以及形貌和成分。结果表明：含硫齿轮钢SAE8620H热轧棒材中的夹杂物主要有单独硫化锰和核心主要是Al2O3和MgO-Al2O3,外围是MnS或者（Ca、Mn）S的氧硫复合夹杂物;从边缘到中心,夹杂物总数递增,氧硫复合夹杂物比例递减;棒材横截面上夹杂物大部分小于2μm,长宽比小于3;棒材纵截面上夹杂物平均长度为11μm,边缘部位夹杂物平均长度较中心部位短3μm,纺锤状夹杂物的比例占30%。     

耐磨钢厚度截面组织性能演变规律

摘要：利用OLYMPUS GX71光学显微镜、场发射扫描电镜Quanta450和JEM2100F型透射电镜等手段对60mm厚淬火态以及淬火+回火态耐磨钢厚度截面组织性能演变规律进行了研究。结果表明，淬火态耐磨钢厚度截面呈表层硬度高、心部硬度低的梯度分布，回火后表层和心部呈现相反的变化趋势，心部/表面硬度比从70%升至93%，1/4处和心部冲击功降低。厚度截面组织和析出相的差异影响固溶强化和析出强化效果，是性能演变的本质原因，提高淬火冷却速度，改善淬火态厚度截面均匀性是提高性能均匀性和优化应用性能的根本方法。     

Effect of grain size on hardenability of gear steel

The effect of different grain sizes of gear steels on hardenability was researched based on the 20CrNiMoH experimental steel. The quenching samples cut from one same bar were quenched after austenitizing treatment by different austenitizing temperature (925, 950, 980, 1000 and 1050??).The results show that their hardenability are very different. By further study,it??s found that the inconsistency of hardenability of 20CrNiMoH gear steel specimens is mainly due to the difference of grain sizes. The grain sizes and their growth trend of 20CrNiMoH gear steel specimens are different when their austenitizing temperatures are different, and the growth of grain sizes will delay the transformation of subcooled austenite, which can maintain stability of austenite and improve the hardenability of gear steel. The relationship between grain sizes and hardenability of 20CrNiMoH gear steel is also studied quantitatively. It??s found when the grain size level of 20CrNiMoH steel increases by one grade, the hardness of J5, J9 and J15 decrease by 1. 9HRC, 4. 0HRC and 1. 3HRC, respectively, and the hardness of J9 is most affected.     

氮含量对10B21冷镦钢Φ12 mm线材淬火硬度的影响

10B21冷镦钢（/%:0.18~0.23C,≤0.10Si,0.60~0.90Mn,≤0.030P,≤0.035S,0.0008~0.0030B,≥0.02A1）的生产流程为50t顶底复吹转炉-LF-280 mm×325 mm连铸坯-连轧成Φ12 mm材。通过检测得出,当钢中氮含量为0.0046%时,该钢淬火后的HRC硬度值为41~43,而当钢中氮含量为0.0081%时,其淬火后HRC硬度值为21~27,小于技术条件要求HRC值38。通过试验得出Ti/N≤8时,随Ti/N增加,钢中硼的收得率显著增加,如钢中氮含量0.0046%时,Ti/N为7.4,硼收得率达90%,钢中氮含量0.0081%时,Ti/N为4.3,硼的收得率不到70%,造成钢中B含量低,淬火后HRC值降低。通过改进BOF和LF操作,使钢中氮含量控制在0.005%以下（0.0039%~0.0041%）,Ti/N为7.5~8.1,钢材心部淬火HRC值为40~42,达到用户要求。     

高强度船体钢淬火工艺下截面组织与性能均匀性

采用SEM、TEM、EBSD等方法研究了35mm规格船用高强度钢淬火态的截面微观组织特征及精细结构,对其截面不同位置力学性能的对应关系进行了分析。结果表明,35mm淬火态钢板的截面效应明显,距离表面小于8mm时,截面硬度随着距表面距离的增大而减小;在8~17mm范围内,截面硬度处在一个稳定的下平台;在17~18mm范围内,截面硬度出现峰值。心部的抗拉强度和屈服强度均较钢板表面降低了40MPa以上,且心部-80℃冲击功稳定性比表面差。显微组织、板条宽度、有效晶粒尺寸、位错密度等的差异是表面性能优于心部的主要原因。钢板心部大量硬质MA岛存在、中心偏析带及大量非金属夹杂物导致硬度峰值和低温冲击性能的不稳定。     

硼对60 mm厚Q690D钢淬透性和力学性能的影响

 通过端淬试验、[Z]向硬度测试、显微组织和力学性能分析,研究了硼对60 mm厚Q690D钢淬透性和力学性能的影响。试验结果表明：微量固溶硼可显著提高60 mm厚Q690D钢的淬透性;和无硼的试验钢相比,含硼试验钢板厚1/4处的淬火组织由马/贝复相变成板条马氏体,淬火、回火态横截面上[Z]向最大硬度差分别由9、 5HRC降低到4、3HRC,提高了[Z]向硬度的均匀性,同时含硼试验钢淬火、回火态的强度和韧性得到提高。     

Microstructure and Mechanical Properties of Martensitic Stainless Steel 6Crl5MoV

 Martensitic stainless steel containing Cr of 12% to 18% (mass percent) are common utilized in quenching and tempering processes for knife and cutlery steel. The properties obtained in these materials are significantly influenced by matrix composition after heat treatment, especially as Cr and C content. Comprehensive considered the hardness and corrosion resistance, a new type martensitic stainless steel 6Cr15MoV has been developed. The effect of heat treatment processes on microstructure and mechanical properties of 6Cr15MoV martensitic stainless steel is emphatically researched. Thermo-Calc software has been carried out to thermodynamic calculation; OM, SEM and TEM have been carried out to microstructure observation; hardness and impact toughness test have been carried out to evaluate the mechanical properties. Results show that the equilibrium carbide in 6Cr15MoV steel is M23C6 carbide, and the M23C6 carbides finely distributed in annealed microstructure. 6Cr15MoV martensitic stainless steel has a wider quenching temperature range, the hardness value of steel 6Cr15MoV can reach to HRC 608 to HRC 616 when quenched at 1060 to 1100 ℃. Finely distributed carbides will exist in quenched microstructure, and effectively inhabit the growth of austenite grain. With the increasing of quenching temperature, the volume fraction of undissolved carbides will decrease. The excellent comprehensive mechanical properties can be obtained by quenched at 1060 to 1100 ℃ with tempered at 100 to 150 ℃, and it is mainly due to the high carbon martensite and fine grain size. At these temperature ranges, the hardness will retain about HRC 592 to HRC 616 and the Charpy U-notch impact toughness will retain about 173 to 20 J. A lot of M23C6 carbides precipitated from martensite matrix, at the same time along the boundaries of martensite lathes which leading to the decrease of impact toughness when tempered at 500 to 540 ℃. The M3C precipitants also existed in the martensite matrix of test steel after tempered at 500 ℃, and the mean size of M3C precipitates is bigger than that of M23C6 precipitates.     

Study on microstructure and mechanical properties of martensitic stainless steel 6Cr15MoV

Martensitic stainless steel containing 12%-18%Cr have high hardness due to high carbon content. These steels are common utilized in quenching and tempering processes for knife and cutlery steel.The properties obtained in these materials are significantly influenced by matrix composition after heat treatment,especially as Cr and C content.Comprehensive considered the hardness and corrosion resistance,a new type martensitic stainless steel 6Cr15MoV has been developed.This study emphatic researches the effect of heat treatment processes on microstructure and mechanical properties of 6Cr15MoV martensitic stainless steel.Thermo-Calc software has been carried out to thermodynamic calculation;optical microscope（OM）,scanning electronic microscope（SEM） and transmission electron microscope（TEM） have been carried out to microstructure observation;hardness and impact toughness test have been carried out to evaluate the mechanical properties.Results show that the equilibrium carbide in 6Cr15MoV steel is M₂₃,C₆ carbide,and finely distributed of M₂₃C₆ carbides can be observed on annealed microstructure of 6Cr15MoV stainless steel.6Cr15MoV martensitic stainless steel has a wider quenching temperature range,the hardness value of steel 6Cr15MoV can reach to 60.8 -61.6 HRC when quenched at 1060 - 1100℃.Finely distributed carbides will exist in quenched microstructure,and effectively inhabit the growth of austenite grain.With the increasing of quenching temperature,the volume fraction of undissolved carbides will decrease.The excellent comprehensive mechanical properties can be obtained by quenched at 1060-1100℃with tempered at 100-150℃,and it is mainly due to the high carbon martensite and fine grain size.At these temperature ranges,the hardness will retain about 59.2-61.6 HRC and the Charpy U-notch impact toughness will retain about 17.3-20 J.The morphology of impact fracture surface of tested steel is small dimples with a small amount of cleavage planes.The area of cleavage planes increases with the increasing of tempering temperature.     

热处理对40CrMnSiB低合金超高强度钢组织和性能的影响

采用OM、SEM、JMatPro7.0分析技术,研究了热处理工艺(860～950℃淬火+200～400℃回火)对新型中碳40CrMnSiB低合金超高强度钢(0.41C,0.84Cr,0.76Mn,1.44Si,0.006B)微观组织及力学性能的影响。结果表明:920℃淬火和300℃回火钢的力学性能达到最佳强韧性匹配,即抗拉强度为1 943 MPa、屈服强度为1 931 MPa、延伸率为9%、断面收缩率为39.5%、冲击吸收功为44J、HRC硬度值为52.7。