奥氏体化温度对微硼耐磨钢组织性能的影响

采用力学性能测试、金相分析及TEM微观结构分析,研究了淬火温度及保温时间对低合金耐磨钢显微组织和力学性能的影响,并通过端淬试验研究了奥氏体化温度对淬透性的影响.结果表明:在830～910℃温度范围内,淬透性随奥氏体化温度升高而提高,当奥氏体化温度超过910℃时,钢板淬透性降低.850℃保温30～45 min的亚温淬火组织中,存在尺寸为1μm左右的高缺陷铁素体弥散分布,使钢板韧性得到提高;910℃保温45～60 min完全淬火后,钢板具有良好的强韧性;奥氏体温度超过930℃以及延长保温时间都会使原始奥氏体晶粒粗化,导致钢板韧性降低.     

97#钢板热成形工艺组织与力学性能研究

对97#钢板进行了热冲压实验研究,分析了不同奥氏体化温度、奥氏体化时间、保压时间对工件组织及力学性能的影响。结果表明,奥氏体化温度950℃、奥氏体化时间5min、保压时间60s为较优工艺参数,抗拉强度达2203MPa,强塑积为18.7GPa·%,金相组织为马氏体。     

氢对SAF2205钢低温塑性的损伤行为

采用慢速拉伸方法研究了－１９６￣２０℃温度范围内，氢对ＳＡＦ２２０５双相不锈钢力学性能的损伤作用。结果表明：氢使塑性明显降低，在－５０℃时达到极大值；温度下降和变形将促进马氏体转变，致使钢的低温强度和延性有所增加，氢致脆化现象与氢的扩散行为及马氏体转变行为有关。     

热处理对65Mn锯片用钢组织及性能的影响

对轧制态65Mn锯片用钢在740℃球化退火保温120 min后,分别在800~880℃范围内进行油淬并在370~450℃温度范围内进行回火处理.采用光学显微镜、万能力学性能试验机、冲击试验机及洛氏硬度计分别分析其金相显微组织、力学性能变化规律.结果表明:淬火组织为淬火马氏体+残余奥氏体;随着淬火温度的升高,淬火马氏体组织不断长大;硬度随淬火温度的升高由800℃的58 HRC逐渐提高到880℃的66 HRC.随着回火温度的升高,试样的组织由淬火马氏体逐渐转化为回火马氏体、回火马氏体+回火屈氏体组织,强度、硬度逐步降低,而塑性、韧性相应提高;在410℃附近出现了回火脆性.最佳热处理工艺为840℃(保温20 min)淬火+430℃(保温120 min)回火.     

微合金化热轧低硅多相钢的组织与性能

为了开发微合金化热轧低硅多相钢,在不含替代硅的合金元素的化学成分设计基础上,通过热轧实验研究了终冷温度对显微组织和力学性能的影响。结果表明,终冷温度从420℃升高到500℃,均可得到多相组织,其中残余奥氏体量增加了6.5%,马氏体消失,组织中出现大量的贝氏体。当实验钢的轧制工艺参数和开冷温度相近时,组织中的铁素体量、铁素体平均晶粒尺寸大致相同,终冷温度对其硬相特性以及残余奥氏体的分布有很大影响。终冷温度为470℃时,硬相特性及残余奥氏体的分布匹配良好,其屈服强度、延伸率、强塑积分别达到460 MPa、31.3%和21 754 MPa·%。     

热处理对低锰高镍管线钢力学性能的影响

采用金相显微镜、扫描电镜观察和力学性能测试研究了650~850℃热处理对低锰高镍TMCP管线钢微观组织及力学性能的影响.结果表明:轧态钢板以针状铁素体组织为主,有良好的强韧性.经650℃高温回火后M/A岛分解并球化,贝氏体发生回复和部分再结晶,大量析出物弥散分布,强度稍有提高,韧性略有降低.经700~800℃双相区加热空冷后的显微组织由铁素体和不规则的M/A或贝氏体组成.700℃热处理抗拉强度升高到778 MPa,但-40℃冲击功依然高达132J,拉伸曲线表现出连续屈服行为.750℃热处理后强度降低,冲击功提高至302J,伸长率提高至22%,具有很好的塑韧性.850℃正火组织强度较低.选择650~750℃的热处理工艺,TMCP钢力学性能得到进一步改善.     

M2高速钢模具材料静态与动态弯曲性能

对比研究了１０８０－１２２５℃奥氏体化并淬火及２００－６２０℃回火的多种条件下Ｍ２高速钢模具材料的静弯曲，疲劳及冲击弯曲性能，并探讨了工艺及冶金因素对它们的影响。试验表明这些性质能指标成倍地在大范围变动，影响抗弯强度的主要工艺参数是回火温度，相应的冶金因素是马氏体基体的固有强度与塑性。     

ML08Al钢的回火形变处理研究

以ML08Al冷镦钢为研究对象,研究了不同回火形变处理条件下,材料组织和力学性能的变化。研究发现,经过1 150℃热轧后直接淬火,并于470～530℃进行回火形变处理,随回火温度降低,材料的强度略有增加,但塑性和韧性有所下降。回火后的显微组织由细小纤维状回火屈氏体和铁素体组成,且经过500℃回火形变处理的ML08Al钢具有最佳的力学性能(室温条件下,屈服强度为796 MPa,拉伸强度为812 MPa,延伸率为13.8%,断面收缩率为43.2%,冲击能量为186 J)。与热轧态的相比,延伸率和断面收缩率分别降低了55%和31%,抗拉强度与屈服强度分别提高了78%与124%,冲击能量提高了约8倍。即使在-60℃时,屈服强度为863 MPa,拉伸强度为880 MPa,延伸率为12.7%,断面收缩率为39.4%,冲击能量为147 J。理论计算结果表明:位错强化和细晶强化是导致ML08Al钢回火形变处理后强度提升的两个主要因素。     

S30408焊接接头低温力学性能试验

为了研究国产奥氏体不锈钢S30408在低温下的力学性能变化规律,通过-196~20℃下的低温拉伸试验和冲击试验,获得S30408焊接接头与母材的低温拉伸性能和冲击性能数据.试验结果表明：焊接接头与母材的屈服强度和抗拉强度随温度降低呈现明显的增加趋势,低温强化效应显著;夏比冲击吸收能量和侧膨胀值则随温度降低呈现下降趋势;焊缝处铁素体含量最高,冲击韧性最差,且焊缝处冲击韧性的降低与其本身在低温下抵抗裂纹扩展能力的降低有关;铁素体分布的不均匀性致使焊接接头存在微观力学性能的差异,对接头处变形产生塑性拘束,削弱了焊接接头的承载能力.     

冷却速度对热轧双相钢相变的影响及双相化的可行性

讨论了随着冷却速度的降低，Ｓｉ－Ｍｎ－Ｃｒ－Ｍｏ系热轧双相钢连续冷却转变的组织中多边形铁素体量增多，贝氏体量减少，且贝氏体由羽毛状向粒状转化，当冷速减小到１．２４－０．２℃／ｓ的范围时，组织中出现针状马氏体。此外，该钢的ＣＣＴ曲线上出现了温度间隔约１８０℃的奥氏体亚稳区，为实现双相化热轧工艺提供了理论依据。     

冷轧TRIP钢两相区奥氏体化中合金元素的扩散

为了研究TRIP钢两相区奥氏体化过程中合金元素在奥氏体和铁素体中的分布,利用热膨胀仪、金相显微镜和电子探针等仪器,在对TRIP钢两相区奥氏体化过程进行热力学与动力学分析的基础上,建立了两相区奥氏体化过程的扩散模型,采用显式有限体积法对770℃和800℃的奥氏体化过程进行了数值求解.模拟结果表明：奥氏体生长初期受C元素在奥氏体中的扩散控制达到亚平衡,此时Mn元素在奥氏体与铁素体界面处的质量浓度差不显著;而奥氏体生长后期受Mn元素在铁素体中的扩散控制而达到最终平衡,此时Mn元素在奥氏体与铁素体界面处有较显著的浓度梯度.     

Influence of hot rolling conditions on the mechanical properties of hot rolled TRIP steel

Influence of hot rolling conditions on the mechanical properties of hot rolled TRIP steel was investigated. Thermomechanical control processing （TMCP） was conducted by using a laboratory hot rolling mill, in which three different kinds of finish rolling temperatures were applied. The results show that polygonal ferrite, granular bainite and larger amount of stabilized retained austenite can be obtained by controlled rolling processes. The finer ferrite grain size is produced through the deformation induced transformation during deformation rather than after deformation, which affects the mechanical properties of hot rolled TRIP steel. Mechanical properties increase with decreasing finish rolling temperature due to the stabilization of retained austenite. Ultimate tensile strength （UTS）, total elongation （TEL） and the product of ultimate tensile strength and total elongation （UTS×TEL） reaches optimal values （791 MPa, 36% and 28 476 MPa%, respectively） when the specimen was hot rolled for 50% reduction at finish rolling temperature of 700 ℃.     

Effect of Direct Quenching and Partitioning Treatment on Mechanical Properties of a Hot Rolled Strip Steel

Three different online heat treatment processes were designed to study the effects on the mechanical properties of a 0.19C-1.6Si-1.6Mn(wt%) hot rolled strip steel.The microstructures were characterized by means of SEM,TEM,EPMA,and XRD.The mechanical properties were estimated by tensile tests.Results showed that a satisfying combination of strength and ductility could be obtained through the ferrite relaxation and direct quenching and partitioning process.Analysis was also focused on this process.The microstructure contained proeutectoid ferrite grains,martensite packets and blocky or interlath retained austenite,and also contained carbide-free bainite in the case of relatively high quench temperatures.The retained austenite fraction was increased through proeutectoid ferrite and partial bainite transformation,while the tensile strength was also consequently decreased.The most of retained austenite transformed to ferrite under deformation and the elongation was obviously improved.     

Mechanical properties of fine-grained dual phase low-carbon steels based on dynamic transformation

The fine grained dual phase (FG-DP) steel with ferrite grains of 2-4.5 μm and martensite islands smaller than 3 μm was obtained through the mechanism of deformation-enhanced ferrite transformation (DEFT). Mechanical properties of the steel were tested at room temperature. The results indicated that with a similar volume fraction of martensite (about 20vol%),FG-DP steel ex-hibited a superior combination of higher strength and more rapid strain hardening at low strains compared with the coarse-grained dual ph...     

800 MPa级CSiMnNb与CSiMnCr系冷轧双相钢组织与性能

在实验室采用CCT-AY-Ⅱ连续退火模拟器研究不同退火温度条件下800 MPa级CSiMnCr与CSiMnNb系冷轧双相钢的力学性能,并对其显微组织进行分析.结果表明：在同一成分试验钢中,770℃退火较790℃退火时所获得的强度高;钢中添加少量的Nb细化了铁素体与岛状马氏体组织,并且岛状马氏体更纯净,屈强比低,加工硬化指数n值更高.     

Relation of martensite-retained austenite and its effect on microstructure and mechanical properties of the quenched and partitioned steels

A two-step quenching and partitioning(QP) treatment was applied to low-carbon alloy steels. The relation of initial martensite- retained austenite- fresh martensite and its effect on microstructure and mechanical properties were investigated by experiments. The results reveal that the volume fraction of retained austenite can reach the peak value of 17%, and the corresponding volume fractions of initial martensite and fresh martensite are 40% and 43%, respectively, when the tested steel is treated by initial quenching at 330°C, partitioning at 500°C for 60 s and final quenching to room temperature. Moreover, the micromorphologies of austenite and martensite become finer with the increasing of initial martensite fraction. The elongation is the highest when the volume fractions of initial martensite and retained austenite are 70% and 11%, respectively, meanwhile, the yield strength increases and tensile strength decreases gradually with the increase of initial martensite fraction, which proves that the mechanical properties including elongation, yield strength and tensile strength are based on the comprehensive effect of the retained austenite fraction, the finer microstructure and austenite stability.     

Effect of controlled rolling on the martensitic hardenability of dual phase steel

The C-Mn and C-Mn-Nb steels were thermo-mechanically processed to develop dual phase steel and to study the effect of controlled rolling on the martensitic hardenability of austenite. The steel specimens were intercritically annealed at 790°C,rolled at that temperature to the reductions of 10%,23%,and 47% and immediately cooled at different rates. Quantitative metallography was used to construct the microstructure map,which illustrated that increasing deformation progressively reduced the proportion of new ...     

A Special TMCP Used to Develop a 800MPa Grade HSLA Steel

The effect of relaxation after finished rolling on structures and properties of four microalloyed steel with different content of Nb and Ti was investigated. By alloy designing and control rolling + relaxation-precipitation-control phase transformation (RPC) process, a new 800 MPa grade HSLA plate steel could be obtained, the microstructure is composite ultra- fine lath bainite/martensite. The tempering process and mechanical properties of this kind of HSLA steel were investigated. The yield strength can achieve 800 MPa, and the ductility and impact toughness is satisfied.     

High performance low cost steels with ultrafine grained and multi-phased microstructure

Ultrafine grained ferrite was obtained through tempering cold rolled martensite with an average grain size of 200―400 nm in a low carbon and a microalloyed steel. Thermal and mechanical stability of the two steels was studied. Due to the pinning effect of microalloyed precipitates on the movement of dislocations and grain boundaries, the recrystallization and grain growth rate were retarded, and the thermal stability of ultrafine grained microstructure was improved. The ultrafine grained ferritic steel was ...     

Analysis of Microstructure and Mechanical Properties of Ultrafine Grained Low Carbon Steel

A novel design scheme of hot stamping, quenching and partitioning process was conducted in a quenchable boron steel to obtain the nanometric duplex microstructure comprising ultrafine retained austenite and martensite. It is shown that the materials possess excellent mechanical properties and the ductility can be further improved without compromising the strength. The newly treated steel shows excellent mechanical properties and the total elongation of the steel increases from 6.6% to 14.8% compared with that of hot stamped and quenched steel. Therefore, this kind of steel has become another group of advanced high-strength steels. The microstructure which is mainly responsible for such excellent mechanical properties was investigated.