变形工艺参数对铁素体相变行为的影响

在Ｇｌｅｅｂｌｅ５００热模拟机上测定了温度为８５０℃，变形为５０％的单道次动态ＣＣＴ曲线，并以此为依据在Ａｒ３附近进行了多道次累大变形和单道次大变形的轧制对比实验。同时进行了变形温度、变形量和冷却速度对铁素体相变行为的影响研究。结果发现在奥氏体未再结晶区进行多道次大压下量轧制及轧后快速可以大在地细化晶粒。     

316奥氏体不锈钢中厚板轧制晶粒度控制研究

针对316不锈钢中厚板晶粒度控制问题在实验室进行了一系列的轧钢试验,分别对钢坯原始组织状态、总轧制压缩比、单道次变形率3个因素进行分析。试验结果表明,当轧制压缩比超过6时,钢坯原始组织状态对中厚板全厚度晶粒均匀性无明显影响;钢坯加热温度、道次压下量相同时,总压缩比为6生产工艺能够轧制出全厚度晶粒均匀的钢板;当轧制总压缩比为4时,单道次压下率超过30%时,钢板表面晶粒度为2级和7级混晶组织;单道次轧制变形量均小于10%时,即使轧制总压缩比足够大,钢板热轧态晶粒度依然不均匀。     

H型钢变形量与奥氏体组织演变研究

借助有限元模拟方法,对H型钢生产过程中粗轧、精轧单道次和多道次变形压下量、轧制速率对奥氏体组织演变的影响进行研究,并表征了奥氏体再结晶和晶粒直径大小的关系。模拟结果表明:轧制前几个道次较大应变有利于奥氏体晶粒细化,高温段大变形量对细化奥氏体晶粒、均匀奥氏体组织有利。利用组合优化后的模拟结果,改进轧制工艺,现场应用结果表明,优化后奥氏体晶粒的最大值减小了近30%,奥氏体组织更加均匀,平均晶粒尺寸相应减小,奥氏体组织得到细化,有利于提高H型钢的力学性能。     

低碳锰铌钢两道次热变形的变形抗力

用热扭转试验方法,对低碳锰铌钢两道次热变形过程中的变形抗力进行了研究。基于软化百分数能反映多道次变形过程中应变累积效应的事实,提出了计算多道变形时变形抗力的“有效应变法”的计算方法。用该方法,对“多道次、小压下、累积压下率”控制轧制工艺条件下,轧制力和轧制力矩进行了计算。通过计算确定,多道次、小压下率轧制能降低每道次轧制力和轧制力矩,但消耗的总功率高于大压下率轧制所消耗的总功率。     

42CrMo钢特厚椭圆坯轧制工艺数值模拟

特厚模具钢因具有卓越的性能和可靠的使用寿命,在制造大型模具中起着不可替代的作用。然而,在连铸过程中,铸坯内部可能形成的缺陷对模具钢的力学性能和使用寿命造成严重影响。设计合理轧制工艺提高芯部变形是改善芯部缺陷的重要途经之一。针对大直径椭圆连铸坯轧制成特厚钢板的开坯粗轧、平整成型及精轧3个过程,采用有限元数值模拟的方法研究了不同轧制工艺对42CrMo特厚钢板不同位置的累积变形量、单道次变形量以及钢板成材率的影响。利用材料性能计算软件JMatPro计算了42CrMo钢的高温变形行为和热导率、比热容、密度、弹性模量、泊松比等物理参数,采用ABAQUS软件进行轧制有限元模拟分析了轧制道次压下量对椭圆坯内部疏松压合的影响规律。结果表明,开坯粗轧的前3道次压下量变化对芯部变形影响不大,芯部变形量主要取决于精轧阶段单道次压下量。采用前3道次较小压下量开坯加后5道次较大压下量精轧,芯部累积变形量最大,达1.5,且最后5道次中每道次的应变量均大于0.14,可以有效提高大规格椭圆坯轧制的特厚板芯部变形渗透率,有利于芯部裂纹和疏松等铸坯缺陷的改善。     

改进大立辊轧制工艺的试验研究

热轧带钢厂大立辊轧机现行工艺为一道次轧制,不能满足用户对成品带钢宽度多规格的要求。为了解决上述问题和提高带钢本身的性能,拟改革道次轧制为可逆多道次轧制,增大板坯侧压量。本文通过模拟试验阐述了改多道次后板坯的变形情况及规律。通过对多道次轧制,孔型形状、板坯变形规律等进行了解析讨论,阐述了采用多道次累积增大板宽压缩量的优劣点。     

10Ti钢多道次累积应变流变应力模型

本文利用Themecmastor-Z热模拟试验机,对10Ti钢单道次、双道次热变形流变应力变化作了研究。结果:1)10Ti钢的形变激活能Q为392.6KJ/mol;2)单道次流变应力模型;3)第二道次残留应变率与变形温度、变形速率、前道次变形量及道次间隙时间的关系;4)多道次累积应变变形抗力模型。     

一种奥氏体变形应力应变集成模型

介绍了预报奥氏体经多道次塑性加工时应力应变行为的集成模型.研究了试验钢加热等温过程奥氏体晶粒尺寸.在Gleeble 3800试验机上完成了系列单道次和双道次热压缩变形试验.采用Kocks-Mecking加工硬化物理模型,建立了奥氏体单道次变形过程应力应变本构关系模型.应用Johnson-Mehl-Avrami-Kolm...     

X80管线钢热变形过程再结晶规律研究

利用Gleeble2000热模拟试验机,研究X80管线钢单道次变形变形量对奥氏体再结晶及晶粒长大的影响。绘制了试验条件下X80管线钢变形量与奥氏体晶粒尺寸的关系曲线。结果表明:X80管线钢奥氏体晶粒尺寸随着道次变形量的提高,奥氏体晶粒平均晶粒尺寸逐渐减小,晶粒越来越细小均匀。结合设备及工艺条件,确定粗轧末道次压下率为25%。     

住友金属开发超短时间间隔多道次轧制技术

日本住友金属工业公司以热轧簿板为对象,进行了铁素体晶粒度在1微米以下超细晶钢生产技术的研究,着手开发超短时间间隔多道次轧制技术（简称SSMR工艺）。该技术具有与采用低温一个轧制道次大压下精轧相同的晶粒超细化效果,能大幅度降低轧制负荷。     

700MPa管线钢热压缩变形及组织研究

利用 Gleeble-3500型热模拟机,研究700MPa 管线钢(/%：0.07C,0.90Si,0.60Mn,0.008P,0.002S, 0.30Ni,0.10Cr,0.12Mo,0.06V,0.03Nb,0.28Cu,0.04Alt,0.0060N) 20mm热轧板在850~1250℃ 和应变速率0.01~1s^-1下单道次热压缩变形及组织演变,得出单道次压缩变形真应力-真应变曲线,热压缩再结晶动态图和动态再结晶开始时间与变形温度关系(RTT)曲线。研究结果表明,发生再结晶由变形温度和应变速率共同决定,该700MPa管线钢在温度1100~1250℃和应变速率0.01~1s^-1下压缩变形时容易发生再结晶。再结晶发生机制是热压缩应变,使得原始晶粒破碎、新晶界产生迁移促使新晶核生成。     

15CrMoR钢变形抗力及连续转变研究

采用真空冶炼15CrMoR中温压力容器用钢,在MS-300热模拟试验机上采用单道次压缩实验测定了变形抗力,确定了变形抗力模型。采用热膨胀法测定了15CrMoR钢的动、静态CCT曲线。结果表明在接近工业生产的工艺参数条件下,其变形抗力表现为动态回复和动态再结晶型;在静态和动态条件下,15CrMoR钢室温组织为珠光体和铁素体以及部分贝氏体。塑性变形使CCT曲线向左上方移动。该研究为在宽厚板轧机上进行15CrMoR钢的生产提供了理论依据。     

Microstructure Transformations in Tempering Steels during Continuous Cooling from Hot Forging Temperatures

Apart from reducing the processing energy, hardening and tempering of near‐net shape forged components from their forging heat primarily promises shortened conventional process sequences. In this case, the continuous cooling transformation diagrams (CCT diagrams) found in the literature can only be used as a rough approximation of microstructural transformations during the heat‐treatment. The reasons for this are that firstly, the deformation influences the transformation kinetics and secondly, the deformation temperatures are comparatively high. Therefore, both deformation CCT diagrams and, for reference purposes, CCT diagrams without deformation were determined for a selection of heat‐treatable steels (34CrMo4, 42CrMo4, 52CrMo4, 51CrV4, 34NiMo6) at the heating temperature of 1200 °C and deformation levels of 0.3 and 0.6.     

Effect of Thermo‐Mechanical Process on Phase Transformation Behaviors of V–Ti–N Microalloyed Steel

Thermo‐mechanical simulation tests were performed on V–Ti–N microalloyed steel under three hot working conditions by using Gleeble‐3800 thermo‐mechanical simulator to study the effects of hot deformation and post‐deformation holding process on the continuous cooling transformation behaviors of overcooled austenite. The continuous cooling transformation diagrams (CCT diagrams) were determined by thermal dilation method and metallographic method. The effects of the hot deformation, post‐deformation holding, and cooling rate on the microstructure evolution were analyzed. The results show that deformation promotes ferrite and pearlite transformation. In addition, deformation leads to an increase in bainite start temperature, which becomes more markedly with the increase in cooling rate. The post‐deformation holding process is much favorable to promote carbonitride precipitation of the microalloying elements, which contributes to ferrite nucleation and smaller austenite grains. As a result, an increase in ferrite quantity and a decrease in ferrite grain size can be observed. And further more, the post‐deformation holding process reduces the effect of hot deformation on the bainite start temperature.     

高等级管线钢的超细晶粒控制

论述了高强度管线钢超细品粒控制的材料学原理和关键技术.分析了应变诱发相变和超细奥氏体强化相变这两种超细品粒控制方法的原理、工艺设计原则以及工业化应用需要注意的问题.讨论分析的结果表明,轧制过程中积累足够大的应变是实现超细晶粒控制的关键.在工业生产中只能通过多道次轧制工艺逐个道次的应变累加实现所需的应变积累.而抑制道次之...     

再结晶区轧制工艺参数对X80管线钢组织及织构的影响

通过单道次和双道次热模拟实验,研究了变形量20%～50%在980、1000、1020 ℃变形温度、1000℃下不同变形量(25%～40%)以及1 000℃变形后间隔不同时间(1～20 s)的再结晶区的轧制过程。结合金相检测、电子背散衍射(EBSD)及X-射线衍射(XRD)等检测方法表征和分析了变形过程中的间隔时间、变形温度和变形量对晶粒尺寸、解理单元尺寸以及织构的影响。结果表明,随着再结晶间隔时间的减少、再结晶区变形温度的降低和变形量的增加,组织晶粒尺寸和解理单元尺寸均细化显著。当变形温度降低至980 ℃时,可获得更多的{110}滑移面,使得韧性提高。     

Improving corrosion resistance of RE-containing magnesium alloy ZE41A through ECAP

Significant grain refinement was achieved in rare earth (RE) containing aeronautic magnesium alloy ZE41A through equal-chan-nel angular pressing (ECAP) using rotary die at 603 K. Influence of ECAP pass number on its microstructure change and corrosion behavior was investigated by optical microscope (OM)/scanning electron microscope (SEM) observation and potentiostatic polarization tests in aque-otis solution of NaCl, respectively. The results showed that ultrafine equiaxial grains (about 2.5 μm) were obtained over 16 passes due to plastic-induced grain refinement accommodated by dynamic recrystallization. The lower corrosion current density and nobler corrosion po-tential correlated with large number of pressing passes were attributed to the low tendency toward localized corrosion with broken secondary phase after homogenization on ultrafine-grained Mg matrix. The multi-pass ECAP method made the ZE41A aeronautic magnesium alloy more attractive since severe plastic deformation may significandy improve its corrosion resistance besides superior mechanical properties.     

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The continuous cooling transformation process and the organization performance of transformation product was investigated by means of dilatation test during single pass deformation on Gleeble-3500. The result shows that bainite transition can be happened when the cooling speed about 3??/s on 460B steel with boron, and the grain size is coarse and hardness is higher when the cooling speed (0. 1, 0. 3, 0. 5??/s)is slowly, it is more tiny than without boron. Boron can make the CCT curves shift to right, the transition from austenite to ferrite and pearlite is restrained, the hardenability of the steel are obviously improved, the cooling speed from austenite to martensite is lower and Ac3, Ac1, Ar3, Ar1, Ms is dropped.     

Computer Model of Phase Transformation From Hot-Deformed Austenite in Niobium Microalloyed Steels

Based on thermodynamics and kinetics, a new mathematical model was developed to calculate the CCT diagrams and the transformation kinetics in low carbon niobium steels, in which the effect of deformation on the degree of supercooling was taken into account. The undercooling caused by deformation is the major reason for the increase of the starting transition temperature during continuous cooling. The critical cooling rate of bainite formation is within 2--5 ℃s for the studied niobium steels and deformation is suitable for the occurrence of pearlite. The ferrite volume fraction increases with the increase of the austenite boundary area, and decreases with the increase of the cooling rate. The calculated CCT diagrams and the volume fraction of each phase are in good agreement with the measurements.     

Q235/304碳钢-不锈钢复合板界面结合的有限元模拟

应用MARC软件对304不锈钢(%:17～19Cr、8～11Ni)/Q235碳钢(%:0.14～0.22C)复合板前5道次往复热轧过程(变形率%:3.4、10.4、25.0、37.8、49.4)进行有限元模拟,得出Q235钢和304不锈钢在界面处的应力和应变分布。模拟结果表明,在两种材料都进入塑性变形状态时,界面处法向应力值达到或超过304不锈钢界面温度下的变形抗力,且两种材料应变平均值的差值≤0.01时即可复合,该模拟结果与生产试验结果一致;这说明使用小的单道次变形率,大的累积变形率可获得结合良好的碳钢/不锈钢复合板。