P20塑料模具钢预硬化热处理工艺的研究

通过金相显微镜、扫描电镜和维氏硬度计,对P20塑料模具钢进行了显微组织观察和硬度测定,研究了在淬火温度、淬火介质、回火温度等不同预硬化热处理工艺参数条件下得到的组织及其硬度变化规律。结果表明:随着回火温度升高,水淬和空淬钢组织中的板条马氏体和贝氏体逐渐减少,铁素体增加并长大,碳化物增多,硬度逐渐降低,板条间的薄片状M/A组元、铁素体中较高的位错密度以及细小碳化物保证了水淬钢在620℃回火时具有较高的硬度,最终确定了保证该钢种最佳预硬化效果的工艺参数。     

热处理对Ti微合金钢组织性能的影响

采用OM、SEM、拉伸及冲击试验等方法,对比研究了淬火温度对Ti微合金高强钢组织和性能的影响。结果表明,热处理后钢获得板条马氏体组织,随着淬火温度的升高,奥氏体化越充分,碳化物及合金元素溶解充分,强硬度增加;当加热温度过高,碳化物聚集长大,晶粒度过大,降低强硬度;冲击功随淬火温度升高则呈现下降趋势,即韧性降低。     

细晶强化和位错强化对中锰马氏体钢的强化作用

 研究了碳和锰含量对淬火中锰马氏体钢的位错密度、残余奥氏体含量、晶粒尺寸等组织结构以及室温力学性能的影响。借助于SEM、EBSD、TEM和XRD表征了材料的微观组织,探讨了马氏体钢的强化机制。结果表明:随着碳含量增加,淬火中锰钢的位错密度和残余奥氏体体积分数逐渐增加,板条束和板条块尺寸逐渐细化,大角晶界百分数逐渐增加,强度逐渐升高;增加锰含量能够提高马氏体钢的位错密度和抗拉强度。分析认为,位错强化和细晶强化是淬火中锰马氏体钢的主要强化机制。马氏体板条尺寸是马氏体抗拉强度的结构控制单元,而原奥氏体晶粒尺寸则是马氏体屈服强度的结构控制单元。     

退火工艺对 AMS 6308钢硬度及组织的影响

利用扫描电镜、透射电镜和硬度测试等方法研究了不同退火工艺对 AMS 6308钢硬度及组织的影响。结果表明,提高退火温度,马氏体板条内位错密度降低,M6 C 的尺寸逐渐增加,硬度下降,但在750℃以上退火,进入二相区,空冷后产生二次马氏体,硬度回升。延长退火时间,马氏体板条回复逐渐充分,硬度开始下降较快,16 h后组织变化不明显,M6 C 的含量变化不大,硬度变化也不大。退火软化程度主要受板条内位错密度的下降以及M6 C 的粗化控制。推荐退火温度选择700~720℃,退火时间不低于16 h,720℃退火软化效果最佳。     

奥氏体化温度对30Cr3SiMnNiWMo钢组织性能的影响

试验研究了860～980℃奥氏体化处理对30Cr3SiMnNiWMo钢(%:0.28C、0.74Mn、1.04Si、2.70Cr、1.15Ni、0.45Mo、1.04W、0.07V、0.05Al)组织以及260℃回火后钢的力学性能的影响。结果表明,30Cr3SiMnNiWMo钢860～920℃淬火组织中存在大量M6C碳化物,对回火钢的韧性不利;950℃淬火后,钢中M6C碳化物基本溶解,原奥氏体晶粒开始长大,回火后钢的强度降低;30Cr3SiMnNiWMo钢经920℃1h油淬+260℃2h回火可以获得具有少量残余奥氏体和未溶碳化物的板条马氏体组织,并具有优良的强韧性(Rm=1680 MPa, Rp0.2=1330 MPa,A=13%, Z=58.5%, AKU=85 J) 。     

回火温度对07MnMoVR钢微观组织的影响

研究了07MnMoVR钢910℃保温1 h淬火后,不同的回火温度对微观组织的影响。试验钢在回火过程中伴随着铁素体回复与再结晶及碳化物的聚集长大。回复过程中板条贝氏体板条合并,位错密度降低,并重新排列形成条状或网状分布。当回火温度高于600℃时,铁素体再结晶形成位错密度很低的等轴铁素体取代淬火组织中的板条铁素体晶粒。析出的碳化物逐渐与铁素体脱离共格关系而迅速聚集长大并粗化。本文对07MnMoVR钢在不同回火温度下贝氏体转变、残余奥氏体的分解和碳化物的转变等规律的研究结果,为现场制定合理的回火工艺制度提供了重要的理论依据。     

淬火工艺对马氏体高强钢组织和性能的影响

摘要：采用拉伸、冲击、金相、电子背散射衍射、透射电镜、X射线衍射等试验手段,研究了在线直接淬火+回火（DQT）与离线再加热淬火+回火（RQT）工艺对马氏体高强钢组织性能的影响。结果表明,2种试验钢组织均为板条马氏体,RQT试验钢原奥氏体晶粒及板条束呈等轴状,板条块较短,板条较宽,DQT试验钢原奥氏体晶粒呈扁平状,板条束贯穿整个晶粒,板条块呈细长状,板条宽度较小;位错强化是DQT试验钢强度较RQT高的主要原因;板条束为控制DQT和RQT试验钢韧性的最小单元;DQT试验钢大角晶界比例较低,其具有较大的马氏体板条束尺寸以及更高的位错密度,断裂应力较低,低温韧性较差。     

高强韧性海洋平台用E550钢板生产工艺研究

介绍了E550钢板的主要生产工艺和技术难点,通过理论分析设计了E550的成分体系,采用Thermal-Calc和经验公式,获得了其热力学相图和相变点温度等热力学数据。根据E550的热力学特性,设计了两阶段轧制工艺,精轧的终轧温度控制在再结晶温度附近,利用奥氏体再结晶充分细化晶粒。淬火奥氏体化温度选择为920℃,回火温度设计为630℃,利用碳化物的析出强化效果和缺陷密度变化的位错强化获得良好的强韧性匹配。50 mm厚钢板的淬火态1/4厚度处的微观组织为马氏体,中心的组织为马氏体和少量贝氏体的混合物。回火热处理后,马氏体板条界面减少,碳化物在马氏体板条界面析出,钢板1/4到中心的组织均匀化。30和50 mm厚E550钢板的力学性能达到了船级社标准要求,并有较大的富裕量。热输入能量为15和50 kJ/cm焊接后,钢板具有良好的强度性能,熔合线和热影响区的冲击功较高。     

热处理工艺对20Cr1Mo1VTiB螺栓钢组织及性能的影响

为了优化20Cr1Mo1VTiB螺栓钢的热处理工艺,采用SEM、TEM和力学性能测试等手段,研究了热处理工艺对该钢组织及性能的影响。结果表明,20Cr1Mo1VTiB钢热处理态组织为贝氏体,主要强化相为VC与针状M3C相。随着淬火温度的提高,VC逐渐溶解,固溶强化作用增加,室温和高温强度上升、韧性下降。在较低温度下回火,贝氏体板条位错密度高、组织应力大,强度高、韧性差;提高回火温度,VC逐渐长大,基体逐渐发生回复,室温和高温强度降低,韧性显著升高。1 030℃淬火+720℃回火后,20Cr1Mo1VTiB钢体现出良好的强韧性匹配。     

热处理工艺对海洋工程用高强度耐低温H型钢组织及性能影响

摘要：以热轧耐低温H型钢为研究对象,采用光学显微镜、扫描电镜、透射电镜分析和力学性能测试等手段,研究了完全淬火和亚温淬火对试验钢微观组织和力学性能的演变规律。结果表明,试验型钢经780℃亚温淬火+600℃回火处理后,形成回火索氏体+铁素体的网状组织;试验型钢900℃淬火+600℃回火处理后,转变得到具有马氏体位向的回火索氏体,碳化物分布更加细小均匀,位错密度下降。2种热处理工艺制备H型钢综合力学性能优良,屈服强度均达到500MPa以上,900℃淬火+600℃回火处理后钢的屈服强度和抗拉强度更高。-40℃低温冲击韧性比热轧状态下出现大幅度提高,随着淬火温度升高冲击功更加稳定。     

Cu元素对AMS6308钢抗回火性能的影响

 为研究Cu元素对AMS6308钢耐温性的影响,采用SEM、TEM、EBSD、相分析和力学性能测试等手段,研究了不同回火温度下,AMS6308钢(含2%Cu)与不含Cu对比试验钢的组织与力学性能,探讨AMS6308钢中Cu元素对提高抗回火性能的作用。结果表明,随着回火温度提高,AMS6308钢强度先升后降,450 ℃出现峰值,并且整个回火温度区间强度均高于无Cu钢。400 ℃以下温度回火,Cu元素提高整体强度与抗回火性能,主要依靠固溶强化、增加M₆C相的析出强化、细晶强化3种方式的共同作用,主要强化机制是M₆C相析出强化。400 ℃以上温度回火,Cu元素主要依靠ε-Cu相的析出强化,提高强度与抗回火性能。ε-Cu相通过与位错的交互作用,产生强烈的沉淀强化,并在更高回火温度下,使钢保持较为完整的板条结构。     

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.     

Relationship Among Microstructure and Properties and Heat Treatment Process of Ultra-High Strength X120 Pipeline Steel

 The variation of heat treatments including directed quenching and tempering off-line after controlled rolling (DQT) and quenching off-line and tempering off-line after controlled rolling (RQT) with microstructure and mechanical properties of a low-carbon microalloyed steel was compared and analyzed. For DQT, the quenched steel was obviously banded microstructure, with increasing tempering temperature, lath martensite coarsened, the cusp carbide precipitated at grain boundaries, the yield strength fluctuated slightly, and the fracture-separation was obvious. The impact toughness was better in the steel tempered at 500 ℃ for 1 h. In RQT, with increasing tempering temperature, lath martensite degenerated, intragranular and intergranular finer precipitations with smaller than 30 nm precipitated and grew up and were distributed dispersedly, the stripe-like carbides were distributed at grain boundaries, and the yield strength and tensile strengthen decreased obviously. The impact toughness of RQT process was much better than that of DQT process, and the comprehensive mechanical properties were better for the steel tempered at 500 ℃ for 1 h of RQT process.     

回火工艺对COST-FB2转子钢组织与性能的影响

摘要：利用OM、SEM和TEM等手段研究了回火工艺对COST FB2转子钢的显微组织与力学性能的影响,结果表明：570℃一次回火后,马氏体板条内有杆状Fe3C和细小颗粒状的MX,板条界有少量颗粒状碳化物析出;700℃二次回火后,板条内杆状Fe3C和板条界上颗粒状碳化物消失或转变成M23C6型碳化物。经570℃一次回火,COST FB2转子钢试样的强度较高,冲击功较低,再经700℃回火强度略有降低,冲击功增加。经不同温度的2次回火的调整,COST FB2转子钢试样获得了较好的强韧性配合。     

热处理对2 000 MPa超高强度不锈钢组织和性能的影响

 运用Thermal-calc热力学软件、光学显微镜（OM）、扫描电子显微镜(SEM)、透射电子显微镜(TEM)等手段研究了热处理工艺对一种新型的超高强度不锈钢微观组织及力学性能的影响。结果表明,经过固溶处理后钢的基体为高密度位错的板条马氏体组织;强度随着时效温度的升高而逐渐升高,在520～540 ℃时可达到2 000 MPa,且冲击吸收功在540 ℃时达到最大值37 J。此时在板条马氏体上析出大量、细小、弥散以μ相为主的第二相,同时在板条与板条界面上有块状的逆转变奥氏体生成,这是该钢具有超高强度与高韧性的主要原因。     

回火温度对淬火后30MnB5热成形钢组织与性能影响

将30MnB5热成形钢进行淬火和回火处理,利用扫描电镜、透射电镜、能谱仪和拉伸性能检测等方法研究了不同回火温度后的显微组织和力学性能变化.经200℃保温2 min回火后热成形钢的综合力学性能最佳,抗拉强度为1774 MPa,总伸长率为8%,强塑积达14 GPa·%以上,该性能满足热成形后作为汽车结构件的使用要求;并且随着回火温度的升高,力学性能呈非单调性变化.200℃低温回火后,主要为板条马氏体和ε碳化物,位错密度略有降低,析出的ε碳化物粒子呈针状分布在马氏体板条内,长度方向大小为100 nm左右,并与位错发生钉扎作用.随着回火温度的升高,板条马氏体发生回复和再结晶,板条边界逐渐模糊,并向等轴状铁素体转变,位错密度显著降低,ε碳化物逐渐向低能态的近球形渗碳体转变并粗化至200 nm左右,对位错的钉扎作用也随之减弱.      

钴和钼对高钴铬钼轴承钢组织及力学性能影响

通过性能测试和组织观察,研究了钴和钼两种元素对高钴铬钼轴承钢组织和力学性能的影响规律。结果表明,钴和钼元素质量分数降低及匹配改变会使试验钢的综合力学性能降低。试验钢的淬火及回火组织为板条马氏体+残余奥氏体,在钴和钼元素的影响下,Cr_(eq)、Ni_(eq)差值变大,致使试验钢组织中残余奥氏体减少,产生δ-铁素体。并且,碳化物由质量分数1.17%的颗粒状M6C改变成质量分数低于0.15%的针状M_2C。试验钢的强度主要受碳化物影响,而在碳化物质量分数低于0.15%时,w(Co)/w(Mo)的值越小,位错密度越高,则试验钢的强度越高。试验钢的韧性主要受δ-铁素体影响,δ-铁素体面积分数大于6.3%,则试验钢会产生脆性,面积分数小于1.1%则试验钢的韧性较好。     

Microstructure Evolution and Mechanical Properties of HR3C Steel during Long-term Aging at High Temperature

Microstructure evolution and the changes in mechanical properties of HR3 Csteel during long-term aging at650,700 and 750℃ were investigated.The precipitated phases of the aging steel included M23C6 carbides,Z-phase and a trace amount of Nb(C,N).The M23C6 carbides were distributed mainly at the grain boundary,while Z-phase was mainly inside the grains.Amounts of both M23C6 carbides and Z-phase during the aging process increased with increasing aging period and temperature.Coarsening of M23C6 carbides was influenced significantly by aging time and temperature,while the size of the Z-phase was relatively less affected by the aging time and temperature,which had a steady strengthening effect.Coarsening of the M23C6 carbides was the main reason for the decline in high temperature yield strength during long-term aging at 750℃.The M23C6 carbides were linked into a continuous chain along the grain boundary which accounted for the decrease of toughness during aging.