退火温度对冷轧中锰钢力学性能的影响

在不同温度下对冷轧中锰钢(Fe-0.1C-5Mn)进行退火试验,研究了其力学性能的变化,通过单轴拉伸试验获得了不同热处理条件下的力学性能。研究结果表明:退火温度从550℃升高至800℃,冷轧中锰钢的抗拉强度和屈服强度先降低后升高;断后伸长率和均匀伸长率以及强塑积则先升高后降低,在650℃时达到最大值。在650℃退火后产生较多的逆转变奥氏体,在形变过程中产生持续TRIP效应,冷轧中锰钢获得了较高的强度以及良好的塑性,强塑积可以达到31 GPa%。     

临界区退火处理对0.15C-1.5Mn-1.5Al冷轧TRIP钢相变和力学性能的影响

利用热膨胀仪、热处理实验、拉伸实验和X衍射实验研究了不同临界退火温度对0.15C-1.5Mn-1.5Al TRIP钢相变、残余奥氏体特征和力学性能的影响.结果表明:不同临界退火温度下的热膨胀曲线具有相同的变化过程,两相区奥氏体含量随临界退火温度的升高而上升,而其碳含量则下降;临界退火温度影响试样的残余奥氏体特征和力学性能,820℃退火处理时残余奥氏体的体积分数为14%,碳的质量分数为1.36%;力学性能也是820℃退火时最佳,强塑积可达25400 MPa·%,且变形过程中具有高的瞬时加工硬化指数(n值).     

Effect of warm- rolling and intercritical annealing on microstructure and mechanical properties of medium- Mn steel

Effect of warm- rolling and subsequent intercritical annealing time at 650?? on microstructure and mechanical properties of a medium- Mn steel 0. 1C- 5Mn was investigated by using uniaxial tensile testing, transmission electron microscopy (TEM) and X- ray diffraction (XRD) analysis. The results show that a duplex microstructure having both equiaxed and lamellar morphologies of reverted austenite and ferrite is obtained after intercritical annealing of the warm- rolled steel sheet. The amount of reverted austenite and its size increase with increasing annealing time, which causes a decrease of the mechanical stability of austenite and thus an increase of ultimate tensile strength (UTS) while a decrease of yield strength, total elongation (TEL) and the product of UTS to TEL (UTS??TEL). An excellent combination of strength and ductility of 40GPa??% could be obtained after a short time annealing of 5min. The combination of strength and ductility (UTS??TEL) could be increased by about 20% for the warm- rolled steel sheet compared to that of the cold- rolled steel sheet. It is thus proposed that warm- rolling is a promising way to simplify the traditional multi- stage rolling and annealing processes of medium- Mn steels as well as further enhancing it mechanical properties.     

含铌TRIP钢连续退火后的组织性能及强化机理

在实验室模拟了含铌与无铌TRIP钢的连续退火工艺过程,通过金相显微技术(OM)、扫描电镜(SEM)、透射电镜(TEM)、背散射电子衍射技术(EBSD)、X射线衍射(XRD)和拉伸实验等检测手段研究了TRIP钢的组织性能,分析了TRIP钢中残余奥氏体稳定性的影响因素及强化机理.结果表明:在连续退火工艺条件下,Nb的存在细化了TRIP钢的微观组织,与未添加Nb的钢相比,添加Nb可以提高TRIP钢中残余奥氏体含量和残余奥氏体碳含量.含铌TRIP钢中残余奥氏体主要以团块状或薄膜状分布于铁素体与贝氏体晶界,极少部分以细小球状分布于铁素体晶内.含铌TRIP钢热轧后的主要析出物为Fe₃C和(Nb,Ti)(C,N),退火后的主要析出物为(Nb,Ti)(C,N).细小含铌析出物的析出强化导致了随着退火温度的升高,屈服强度和抗拉强度升高.     

两相区退火温度对TRIP钢组织性能的影响

 针对600 MPa级别TRIP钢,进行了760、780、800、820、840、860 ℃两相区退火温度试验,利用扫描电镜和拉伸试验机等设备,分析了其对应的组织比例和力学性能检验结果,得出结论：随着两相区退火温度的升高,铁素体体积分数逐渐减少,钢板的抗拉强度值不断增加,但伸长率值却先下降再升高,在820 ℃伸长率有最大值,这与820 ℃时较高残余奥氏体体积分数和最大残奥中碳质量分数相对应,说明TRIP效应可以改善钢板的塑性指标,获得最佳强塑组合;在800～820 ℃的两相区转变温度范围内,强塑积可以达到2.17×104 MPa·%,为600 MPa级TRIP钢退火工艺提供了实际指导。     

临界热处理对中碳 Q&P 钢组织与性能的影响

摘要：对中碳钢采用Q&P（淬火 碳分配）和I&QP（临界热处理,淬火 碳分配）热处理工艺,通过对试样的显微组织,残余奥氏体的体积分数及其碳含量,硬度及其拉伸性能进行分析,研究了临界加热对中碳Q&P钢组织和性能的影响。实验结果表明,经临界热处理的Q&P钢组织中,除了马氏体和残余奥氏体,还存在部分铁素体,同时残余奥氏体的体积分数较少,马氏体板条更加细小。在相同的碳分配时间下,I&QP试样的硬度和抗拉强度都比Q&P试样低,但由于I&QP试样中软相铁素体的存在以及残余奥氏体能发挥更好的TRIP效应,使得临界热处理的实验钢的伸长率更高,加工硬化指数增加,强塑积更大。     

含铝TRIP钢组织和性能的研究

根据镀锌工艺要求设计ω(Al)为1.2%的TRIP钢进行实验研究,使用光学显微镜、SEM、XRD以及拉伸试验对TRIP钢的微观组织和性能进行检测和分析.结果表明,ω(Al)为1.2%的TRIP钢的Ac1达到747℃、Ac3达到930℃,在贝氏体区等温30 s即可得到最大强塑积.实验TRIP钢退火组织中残留奥氏体体积分数...     

两相区退火处理含铝中锰钢的组织和力学性能

 为了研究两相区退火处理对冷轧含铝中锰钢(0.2C-0.6Si-5Mn-1.2Al)(质量分数,%)微观组织和力学性能的影响规律,利用SEM、XRD及单轴拉伸等试验方法表征了不同工艺状态后的微观组织及测试了拉伸性能。结果表明,冷轧试验钢在退火过程中组织发生奥氏体逆转变,在退火温度为670 ℃、退火时间为10 min时可获得较佳的力学性能,即抗拉强度达到1 276 MPa,总伸长率达到51.8%,强塑积高达66.1 GPa·%。随着退火温度升高,残余奥氏体组织逐渐粗化且向马氏体组织转变,机械稳定性逐渐降低。残余奥氏体机械稳定性主要受残余奥氏体中碳质量分数及其晶粒尺寸的影响,而残余奥氏体中锰质量分数对其影响较小。     

Influence of intercritical annealing temperature on microstructure and mechanical properties of medium Mn TRIP steel

The transformation, microstructure and mechanical properties of the 0. 2C- 5Mn TRIP steel after intercritical annealing were investigated using dilatometer, scanning electronic microscopy (SEM), transmission electron microscopy(TEM), X- ray diffraction (XRD), and tensile testing machine. The phase transformation thermodynamics of the investigated steel after intercritical annealing was calculated by Factsage software and the characteristics of the transformation were discussed. The results show that the reversed austenite content increases with the increasing of the intercritical annealing temperature, the carbon content in reversed austenite firstly increases and then decreases, manganese content in reversed austenite decreases, which results in the decreasing of the thermal stability of reversed austenite. When the intercritical annealing temperature is 700??, an obvious martensitic transformation occurs during the cooling process. With the increasing of intercritical annealing temperature, cementite is gradually dissolved, but it cannot be completely dissolved due to the short transformation time. When the intercritical annealing temperature is 600-675??, the microstructure after intercritical annealing consists of ferrite, cementite and retained austenite. When the intercritical annealing temperature is 700??, the microstructure after intercritical annealing consists of ferrite, retained austenite, martensite and a small amount of undissolved cementite. The engineering stress and strain curves of the investigated steel are significantly changed with increasing intercritical annealing temperature. At the same time, the optimal mechanical properties with tensile strength of 1138MPa and total elongation of 23% can be obtained after annealed at 675?? for 3min.     

一次淬火马氏体对Q&P钢组织和性能的影响

 研究了一次淬火马氏体对低合金钢经淬火和配分(Quenching and Partitioning,Q&P)工艺后微观组织和单轴拉伸性能的影响,用扫描电镜进行微观组织表征,用X射线法测量残留奥氏体量。试验结果表明,随着一次淬火马氏体比例的增加,二次淬火马氏体的尺寸和数量逐渐减少,残留奥氏体体积分数呈先增加后减少的趋势,一次淬火马氏体体积分数为40%时获得最大残留奥氏体体积分数为16.92%。一次淬火马氏体体积分数为30%～70%时试验钢获得了较高的塑性和强塑积,马氏体基体为钢提供了高强度,残留奥氏体在变形过程中的TRIP效应提高了钢的塑性。     

不同轧制及退火处理0.1C-5Mn中锰钢的氢脆敏感性

 尽管中锰钢的强塑性等力学性能得到了较大幅度提升,但要大规模地应用于汽车部件制造,仍需解决材料在制造和服役过程中面临的氢脆等系列难题,在此背景下,利用电化学充氢、氢热分析仪、慢应变速率拉伸试验机及扫描电镜等研究了两种不同状态(热轧和温轧)0.1C 5Mn中锰钢在650 ℃保温30 min(两相区退火处理)后的氢脆敏感性。结果表明,热轧和温轧退火样的微观组织分别为板条状及等轴+板条状的铁素体与奥氏体的复相组织。尽管温轧退火样的强度比热轧退火样提高了约150 MPa,伸长率降低了约5%,但两者的强塑积均可达到约33 GPa·%。两种试验材料充氢时吸附的氢绝大部分为对应低温逸出峰的可扩散性氢,温轧退火试验材料的氢脆敏感性低于热轧退火钢。充氢热轧退火样断口起裂处的断裂机制为穿晶断裂+沿原奥氏体晶界的脆性沿晶断裂;温轧退火样的起裂处则为空心韧窝+包括奥氏体(变形后转变为马氏体)晶粒的实心韧窝,后者实际上为沿着奥氏体和铁素体界面起裂的一种脆性沿晶断裂。造成两种试验材料氢脆敏感性不同的原因主要是其微观组织及其所引起的氢致断裂方式的差异。     

Effect of intercritical annealing temperature and cooling rate on the microstructure and mechanical properties of low-carbon aluminum killed steel

In this study,the intercritical annealing process for a typical low-carbon aluminum killed steel is investigated.A cold-rolled sheet was annealed at intercritical temperatures ranging from 730 ℃ to 770 ℃ and then cooled in air or water.The annealed steel was then baked at 210 ℃,and its mechanical properties and microstructures were analyzed in detail.It is shown that after the air-cooling process,the strength of steel decreased and ductility increased with an increase in the annealing temperature.However,after water-cooling,the strength and ductility both increased with the increase of annealing temperature.These results are attributed to the propertyoptimization of the steel.     

冷轧压下率对TRIP钢组织与力学性能的影响

研究了含铝TRIP钢在相同的热处理条件和不同冷轧压下率时的组织和力学性能。结果表明,随着冷轧压下率增加,材料组织细化,屈服强度连续升高;而抗拉强度和伸长率则由于晶粒细化以及TRIP效应,先升高后降低。冷轧压下率74%时材料的综合性能最佳,此时带状组织的危害也有所减轻或消失。     

双相区形变对含Cu低碳钢Cu配分行为及组织性能影响

采用双相区形变+IQP及IQP(双相区等温-奥氏体化-淬火-碳配分)热处理工艺,研究了双相区形变对一种含Cu低碳钢Cu配分行为及其组织性能的影响。采用电子探针(EPMA)、扫描电镜(SEM)及透射电镜(TEM)等手段对元素配分行为及组织演变进行了表征。结果表明:实验钢经2种工艺处理后均出现Cu元素向逆转奥氏体的配分行为,采用双相区形变+IQ(双相区保温淬火)处理的组织中富Cu最高的区域面积为12.9%,比IQ工艺下富Cu区域提高108%;双相区形变+IQP工艺处理后实验钢的晶粒明显细化,且组织中块状残余奥氏体较多;与单一IQP工艺相比,双相区形变+IQP工艺处理的实验钢抗拉强度由1 253MPa提高到1 293MPa,伸长率由16.9%提高到18.3%,残余奥氏体体积分数由11.6%提高到13.8%,表明双相区30%的形变处理实现了促进Cu配分行为诱导残余奥氏体含量增加和细晶强化的双重效果。     

固溶温度对中锰TRIP钢组织与力学性能的影响

以w(Mn)=8%的热轧TRIP钢(即相变诱导塑性钢)为对象,研究了热处理工艺对其显微组织与力学性能的影响规律.该中锰TRIP钢在固溶温度为800℃时,可获得包括铁素体、马氏体、残余奥氏体的多相组织.与一般TRIP钢相比,其力学性能明显提高,在固溶加回火的条件下,实验钢的抗拉强度为800～1 000 MPa,延伸率达到31%～40%,而强塑积达(30～32)GPa%.     

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Forming limit diagram (FLD) of cold- rolled TRIP steel was established by experiments. The microstructures of samples before and after deformation were examined by metalloscopy and scanning electron microscopy and at the same time the contents of retained austenite after different strain ratios were measured by X- ray diffraction. The results show that the ultimate strain under plane strain state(FLD0) is 0. 397. With the strain ratio increasing, strain path changes from uniaxial stretching to plane strain and then biaxial stretching and the transformation amount of residual austenite increases gradually. Compared with dual- phase steel, the higher FLD0of TRIP steel is ascribed to TRIP effect and necking area is wider during deformation.     

深冷对逆相变处理中锰钢组织性能的影响

为了研究原始组织状态对逆相变退火中锰钢微观组织和力学性能的影响,对淬火处理的中锰钢再进行-74℃深冷处理,采用SEM、EBSD、XRD等手段评价了逆相变退火处理后的微观组织,用单轴拉伸和冲击试验评价力学性能.研究结果表明:淬火态中锰钢的组织由马氏体和体积分数约为33％的残余奥氏体组成,深冷处理后得到残余奥氏体体积分数小...     

残余奥氏体中的碳元素在TRIP钢变形前后的分布

利用TEM和EPMA对TRIP钢中残余奥氏体形貌以及碳元素的分配进行了研究,发现TRIP钢中的残余奥氏体以多种形态分布,且碳在残余奥氏体中的浓度显著高于其他两相中的浓度,此时残余奥氏体可以通过EPMA中的贫硅区表示;变形之后的残余奥氏体将会发生相变,通过TEM发现残余奥氏体在受到应力作用而发生相变之后转变为细小的立方马氏体,且由于碳原子来不及扩散,马氏体中的含碳量和奥氏体中的含碳量基本相同。     

Mn和Si对中锰热轧高强钢组织和性能的影响

为了研究Mn和Si元素对中锰热轧高强钢显微组织和力学性能的影响,设计了不同Mn、Si含量C-Si-Mn系试验用钢.利用热膨胀仪、扫描电镜、透射电镜、X射线衍射和单向拉伸等实验方法对试验用钢的相变点、显微组织、残余奥氏体含量和力学性能进行了测定与分析.结果表明：Mn和Si对中锰热轧高强钢的显微组织影响较大,对于低Si高Mn的试验钢,其显微组织主要由粒状贝氏体组成;对于高Si高Mn的试验钢,主要由贝氏体铁素体、马氏体和残余奥氏体组成;对于高Si低Mn的试验钢,则由块状铁素体、贝氏体、马氏体和残余奥氏体组成.高Si高Mn试验钢获得最高的综合力学性能,抗拉强度达1200 MPa以上,总伸长率为16%,强塑积接近20 GPa·%.分析认为,试验钢这种高强度和较高的塑性是由超细晶组织和TRIP效应共同决定的.     

Effects of Mn and Cr contents on microstructures and mechanical properties of low temperature bainitic steel

The effects of Mn and Cr contents on bainitic transformation kinetics,microstructures and mechanical properties of high-carbon low alloy steels after austempered at 230,300 and 350 ℃ were determined by dilatometry,optical microscopy,scanning electron microscopy,X-ray diffraction and tensile tests. The results showed that Mn and Cr can extend bainitic incubation period and completion time,and with the increase of Mn and Cr content,the bainitic ferrite plate thickness decreased and the volume fraction of retained austenite increased. TRIP( transformation induced plasticity) effect was observed during tensile testing which improved the overall mechanical property. The increase of Mn concentration can improve the strength to a certain extent,but reduce the ductility. The increase of Cr concentration can improve the ductility of bainitic steels which transformed at a low temperature. The low temperature bainitic steel austempered at 230 ℃ exhibited excellent mechanical properties with ultimate tensile strength of( 2146 ± 11) MPa and total elongation of( 12. 95 ± 0. 15) %.