基于应力三轴度的铸态42CrMo钢高温拉伸断裂行为分析

利用Gleeble-3500型热模拟试验机对不同缺口半径(0.5,1.0,2.0,4.0 mm)的铸态42CrMo钢缺口试样进行不同温度(1223,1273,1373 K)下的热拉伸试验,基于应力三轴度分析了其高温拉伸断裂行为。结果表明:较高拉伸温度下缺口试样的流变应力较小;随着缺口半径减小,缺口试样流变应力和峰值应力增加,断裂应变减小;当缺口半径为0.5,1.0 mm时,应力三轴度最大值向最小横截面圆心转移;当缺口半径为2.0,4.0 mm时,拉伸过程中最小横截面圆心处的应力三轴度始终最大;随着缺口半径增加,应力三轴度减小;温度由1223 K升至1373 K,试样断口组织平均晶粒尺寸增大;缺口半径由0.5 mm增加至4.0 mm,平均晶粒尺寸增大,微空洞且尺寸及面积分数增加。

MECHANICS ANALYSIS ON PRECISE FORMING PROCESS OF EXTERNAL SPLINE COLD ROLLING

According to the suitable assumption, the deformation process of external spline cold rolling is analyzed. By the graphing method, the slip-line field of plastically deforming area in process of external spline cold rolling is set up. Different friction-conditions are used in different contact areas in order to realistically reflect the actual situation. The unit average pressure on contact surface of the rolling process is solved according to the stress filed theory of slip-line. And the formulae of the rolling-force and rolling-moment are established. The theoretical result is well consistent with the finite element analysis. A theoretical basis is provided for the precise forming process of spline cold rolling and the production of external splined shafts.

Metadynamic Recrystallization of the As-cast 42CrMo Steel after Normalizing and Tempering during Hot Compression

The existing researches of hot ring rolling process are mainly based on forged billet. Compared with the existing process, the new ring casting-rolling compound forming process has significant advantages in saving materials and energy, reducing emission and reducing the production cost. The microstructure evolution of the casting materials during hot deformation is the basis of the research of the new process. However, the researches on the casting materials are rare. The metadynamic recrystallization of the as-cast 42CrMo steel after normalizing and tempering during the hot compression is investigated. The tests are performed on the Gleeble-1500 thermal-mechanical simulator. The influence rule of the deformation parameters on the metadynamic recrystallization is obtained by analyzing the experimental data. The kinetic model of the rnetadynamic recrystallization is deduced. The analysis results show that the metadynamic recrystallization fraction increases with the increase of the deformation temperature and the strain rate. The metallographic experiments are used to investigate the influence rule of the deformation parameters on the grain size of the metadynamic recrystallization. The experimental results show that the grain of the metadynamic recrystallization could be refined with the increase of the strain rate and the decrease of the deformation temperature during hot compression. The occurrence of the metadynamic recrystallization during the hot deformation is more difficult in as-cast 42CrMo steel than in forged 42CrMo steel. The research can provide the foundation for the further research of the hot deformation behaviors of the as-cast structure and theoretical support for the new ring casting-rolling compound process.

Rolling Force and Rolling Moment in Spline Cold Rolling Using Slip-line Field Method

Rolling force and rolling moment are prime process parameter of external spline cold rolling. However, the precise theoretical formulae of rolling force and rolling moment are still very fewer, and the determination of them depends on experience. In the present study, the mathematical models of rolling force and rolling moment are established based on stress field theory of slip-line. And the isotropic hardening is used to improve the yield criterion. Based on MATLAB program language environment, calculation program is developed according to mathematical models established. The rolling force and rolling moment could be predicted quickly via the calculation program, and then the reliability of the models is validated by FEM. Within the range of module of spline m=0.5-1.5 mm, pressure angle of reference circle α=30.0°-45.0°, and number of spline teeth Z=19-54, the rolling force and rolling moment in rolling process （finishing rolling is excluded） are researched by means of virtualizing orthogonal experiment design. The results of the present study indicate that： the influences of module and number of spline teeth on the maximum rolling force and rolling moment in the process are remarkable; in the case of pressure angle of reference circle is little, module of spline is great, and number of spline teeth is little, the peak value of rolling force in rolling process may appear in the midst of the process; the peak value of rolling moment in rolling process appears in the midst of the process, and then oscillator weaken to a stable value. The results of the present study may provide guidelines for the determination of power of the motor and the design of hydraulic system of special machine, and provide basis for the farther researches on the precise forming process of external spline cold rolling.

TOOTH CURVES AND ENTIRE CONTACT AREA IN PROCESS OF SPLINE COLD ROLLING

In spline rolling process, the contact area between roller and workpiece plays an important role in calculating rolling-force and rolling-moment. For the purpose of studying the contact area, contact state between roller and workpiece in process of spline cold rolling based upon cross rolling is analyzed. According to the suitable hypothesis, the mathematic model of roller-tooth-curve in optional position of rolling process is established. Combing the theory of conjugate curves with the theory of envelope curve, the corresponding mathematic model of workpiece-tooth-curve is established. By utilizing establishing mathematic models, the algorithm of entire contact area in rolling process is created. On the basis of the algorithm, calculation-program is compiled under MATLAB program language environment. The calculation-program actualizes quantitative analysis and quantitative calculation of contact areas. Utilizing the calculation-program, the influence of parameters on contact area is analyzed, and the tendency is consistent with the manufacturing experience. In consideration of rolling-force optimization, the primary process parameters may be selected according to results of calculation. The result of the present study may provide basis for research on rolling-force and rolling-moment.

RESEARCH ON THE ENERGY ECONOMIZATION OF ELECTRO-HYDRAULIC HAMMER

The research on the driving principle and economization of energy of electro-hydraulic hammer is discussed. By means of the balance chart of energy, the method and formulas to calculate every level efficiency and the total efficiency of steam drived hammer are formed.With the aid of actual data of plants,the actual efficiency of steam drived hammer is got. The working principle and the driving system of electro-hydraulic hammer are introduced. The procedure of energy energy of this hammer is analyzed. The utilization ratio of energy of this type of hammer is got. It is shown that the efficiency of electro-hydraulic hammer is 7 times as much as that of steam drived hammer.

Advances in Compact Manufacturing for Shape and Performance Controllability of Large-scale Components-A Review

Research on compact manufacturing technology for shape and performance controllability of metallic components can reanze the simplification and high-reliability of manufacturing process on the premise of satisfying the requirement of macro/micro-structure. It is not only the key paths in improving performance, saving material and energy, and green manufacturing of components used in major equipments, but also the challenging subjects in frontiers of advanced plastic forming. To provide a novel horizon for the manufacturing in the critical components is significant. Focused on the high-performance large-scale components such as bearing rings, flanges, railway wheels, thick-walled pipes, etc, the conventional processes and their developing situations are summarized. The existing problems including multi-pass heating, wasting material and energy, high cost and high-emission are discussed, and the present study unable to meet the manufacturing in high-quality components is also pointed out. Thus, the new techniques related to casting-rolling compound precise forming of rings, compact manufacturing for duplex-metal composite rings, compact manufacturing for railway wheels, and casting-extruding continuous forming of thick-walled pipes are introduced in detail, respectively. The corresponding research contents, such as casting ring blank, hot ring rolling, near solid-state pressure forming, hot extruding, are elaborated. Some findings in through-thickness microstructure evolution and mechanical properties are also presented. The components produced by the new techniques are mainly characterized by fine and homogeneous grains. Moreover, the possible directions for fin＇ther development of those techniques are suggested. Finally, the key scientific problems are first proposed. All of these results and conclusions have reference value and guiding significance for the integrated control of shape and performance in advanced compact manufacturing.

艾司氯胺酮预防腹腔镜胆囊切除术中瑞芬太尼痛觉过敏的效果

目的:探讨艾司氯胺酮预防腹腔镜胆囊切除术(LC)中瑞芬太尼痛觉过敏(RIH)的效果。方法:选取2020年3月—2021年3月无锡市锡山人民医院择期LC患者60例为研究对象,均采用全身麻醉,术后均入麻醉后恢复室苏醒,采用随机数字表法分为对照组和观察组,各30例。观察组于麻醉诱导前静脉推注艾司氯胺酮0.25 mg/kg,对照组静脉推注等容量的生理盐水。比较两组羟考酮首次应用时间、总消耗量,拔管后5、10、15、30 min Ramsay镇静评分,右前臂内侧和切口周围痛阈及痛敏面积,术后1、3、6、12、24 h静息和运动时疼痛数字评分(NRS),不良反应。结果:观察组羟考酮首次应用时间晚于对照组,总消耗量少于对照组,差异有统计学意义(P<0.05);术后24 h,观察组切口周围Vonfrey值高于对照组,切口周围痛敏面积小于对照组,差异有统计学意义(P<0.05);观察组拔管后5、10、15、30 min Ramsay镇静评分低于对照组,差异有统计学意义(P<0.05);观察组术后1、3 h静息NRS评分及术后1、3、6、12、24 h运动NRS评分均低于对照组,差异有统计学意义(P<0.05);两组不良反应发生率比较,差异无统计学意义(P>0.05)。结论:艾司氯胺酮可有效预防LC术中RIH,减轻术后疼痛,镇静效果好,且能减少羟考酮用量,不会增加不良反应。

我国大型卷板机研究现状和发展趋势

卷板机服务于国民经济建设各个领域,发展卷板机可以带动上、下游产业链。本文分析了近年来我国卷板机和卷板工艺的研究现状与进展,探讨了发展大型卷板机面临的主要问题与挑战,提出了我国大型卷板装备的发展趋势和展望。

离心铸造Q235B钢环件热辗扩过程中的组织演变

环件铸辗复合成形技术的关键在于使铸态环坯在热辗扩过程中实现宏观几何尺寸成形与微观组织改性的一体化制造。采用热压缩实验建立离心铸造Q235B钢组织演变模型,在DEFORM-3D平台上实现环形铸坯热辗扩过程变形-传热-微观组织演变耦合分析,揭示进给速度和初始辗扩温度对其组织演变的影响。结果表明,随着进给速度增大,动态再结晶体积分数和平均晶粒尺寸均减小;随着初始辗扩温度升高,动态再结晶体积分数增大,平均晶粒尺寸减小,且在1150℃时分布均匀。通过离心铸造环坯工业热辗扩实验发现,环件的各项力学性能指标均达到了标准要求,环件全厚度区域的外层和内层晶粒细小,平均晶粒直径为30~38μm,近中层的少数晶粒尺寸略大,达到了52~57μm。因此,采用离心铸造Q235B钢环坯直接热辗扩成形环件是切实可行的,可以实现环件“形”/“性”一体化控制。

环形零件短流程铸辗复合成形技术研究进展

轴承套圈、法兰等环形零件作为关键连接、传动、回转和支承结构件,在航空航天、风力发电、高铁、船舶和高档数控机床等重大装备制造领域应用非常广泛。环形零件的生产是一种高能耗的热加工过程,传统生产工艺主要有两种:(1)厚板轧制—弯卷—焊接成形,该工艺下环件焊接部位应力集中明显,在高压、强腐蚀等恶劣服役条件下为弱性能区;(2)通过冶炼—浇铸—加热—锭坯开坯—下料—圆棒加热—锻造—冲孔—加热—环坯热辗扩来实现环件生产,该工艺流程冗长,开坯、锻造和冲孔工序设备资金投入巨大,多次加热导致能源消耗和材料浪费严重,不利于环境友好型生产。环件热辗扩过程中的传热-变形-组织演变耦合行为使得环坯经历了多场、多因素作用下多道次、连续局部加载与卸载、不均匀变形和微观组织复杂演变历程,对成形环件的外形尺寸、组织和力学性能均产生显著影响。随着环件应用向着大型、轻量、重载和长寿命方面逐步发展,对其高性能、精确成形与低成本制造提出了更高要求。近年来得到重点研究并取得长足发展的环形零件短流程铸辗复合成形技术以砂型铸造或离心铸造获得的环形铸坯加热后直接进行辗扩为基础,省去了开坯、锻造和冲孔,只需要一次加热,具有工艺流程短和节能节材等突出优点(节材30%以上、节能60%以上),是风电法兰、石油化工容器和高档数控机床主轴承等重大装备高效、高性能和绿色制造的必然要求。然而,在热辗扩过程中不仅要实现环形铸坯截面轮廓达到所要求环件外形尺寸,同时其组织与性能也要得到充分改善和提高,使得对热辗扩过程中组织演变和性能控制面临诸多技术挑战。研究者们深入分析了环形铸坯材料单道次和双道次热压缩变形行为、组织演变规律及其模型构建方法,建立了关于材料常数考虑应变补偿的本构关系模型,为此研究了热-力-组织演变多场耦合及其基于晶粒拓扑变形技术和介观-微观元胞自动机跨层次耦合条件下的热辗扩数值模拟技术,构建了考虑晶粒空间重叠的CA模型,基于工业性试验从织构视角研究了其在铸坯环件热辗扩成形中微观组织和性能控制规律,获得了环件不同区域的晶粒细化极限,可以实现环件短流程铸辗复合成形生产。本文综述了基于锻态环坯和铸态环坯的热辗扩成形技术研究进展,探讨了环形铸坯热辗扩过程中组织与性能协同调控的理论与方法,建立了环形铸坯凝固过程裂纹萌生判据与裂纹控制的工艺方法,提出了环形铸坯热辗扩成形技术的研究发展方向,阐述了双金属复合环形铸坯热辗扩成形技术的研究内容及重点,以期推动环件短流程制造全过程“形”/“性”一体化调控理论与技术发展。

铝合金环形零件形/性一体化制造技术

铝合金环形零件作为关键连接、传动、回转和支承部件在重型运载火箭贮箱、风电设备的轴承套圈及齿轮环、压力容器和核反应堆的加强圈等重大装备制造领域应用非常广泛。铝合金环形零件的生产是一个高能耗的热加工过程,现有生产工艺主要有两种:(1)厚板轧制-弯卷-对半焊接成形,环件焊接部位缝组织为弱性能区,无法满足在重载、冲击、高低温和强腐蚀等极端恶劣条件下长期稳定服役时的要求;(2)圆铸锭坯-多向锻造制坯-马架扩孔或环件辗扩,工艺流程冗长,辗扩前开坯、锻造和冲孔工序设备资金投入巨大,多次加热导致能源消耗和材料浪费严重,不利于环境友好型生产。深空探测领域铝合金环件存在几何尺度大、形状精度高、结构刚度低和服役环境苛刻等技术挑战,目前已实现Φ3 m~Φ10 m级大型铝合金环件辗扩生产。环件辗扩过程中的传热-变形-组织演变耦合行为使得环坯经历了多场、多因素作用下多道次、连续局部加载与卸载、不均匀变形和微观组织复杂演变历程。为了实现铝合金环件的辗扩成形,一是要使环件自身整体刚性和辗扩过程稳定,即"控稳";二是要使环件直径扩大与截面充填协同进行,同步获得径-轴向尺寸、截面轮廓及几何精度,即"控形";三是要使成形环件达到所要求的内部组织状态和各向性能,即"控性"。铝合金环形零件用环坯的制备是铝合金环件辗扩成形及其形/性一体化调控的基础,采用多向锻造变形技术可以有效细化大规格圆铸锭的粗大组织、破碎网状共晶化合物,实现组织改性,为后续辗扩过程提供优质环坯。通过开发铝合金环件双向辗扩智能建模仿真方法和基于力控的铝合金环件双向辗扩工艺路径智能仿真优化方法,解决了矩形/异形截面环件径-轴向变形区不协调、环件刚度弱及辗扩过程失稳等问题,实现了各轧辊运动的协调匹配和基于目标驱动的自动调控。利用辗扩成形后的形变强化和热处理时效析出强化改性技术,可以进一步提高环件强度和消除残余应力,使环件径向、轴向和周向均具有优良的性能。针对现有技术的不足,本文提出了环形零件短流程铸辗复合成形技术,将砂型铸造或离心铸造获得的环形铸坯加热后直接进行辗扩,在热辗扩过程中同时实现环形铸坯几何尺寸精度要求和组织与性能改善,揭示了基于织构演变的铸坯环件在热辗扩成形中的微观组织和性能控制机制,可为铝合金环件及铝基双金属层状复合环件的短流程形/性一体化制造提供理论指导。本文基于铝合金环形零件形/性一体化制造技术的研究现状,从铝合金环形零件用环坯的制备技术、铝合金环件辗扩成形技术和铝合金环件辗扩过程中组织与性能协同调控技术研究等方面做简要评述,着重阐述铝合金矩形/异形截面环件形/性一体化控制的技术挑战,提出铝合金环件制造技术的发展趋势及研究重点,以期推动铝合金环件/铝基双金属层状复合环件短流程制造过程中形/性一体化调控理论与技术的发展。

大采高液压支架立柱系统动态特性研究

大采高液压支架供液管路的工作压力为23~32.5 MPa、通流直径为38~60 mm、管路长度为1000~1500 m,供液管路具有明显压力、流量响应滞后效应,导致立柱缸液压系统的速度、位移动态特性较差。对液压支架大通径高压供液管路进行水锤试验,试验结果为:在流量为182.7、351.2和521.5 L/min时,压力波速分别为715、979和1065 m/s。建立了AMESim管路模型和液压支架系统模型,分析管路长度、管路通径和初始压力对液压支架立柱动态特性影响规律。仿真结果表明:管路长度越大,管路通径越大,管路初始压力越小,立柱响应时间越长,升柱和降柱过程平稳性高,所用时间增长。

Technology and Experiments of 42CrMo Bearing Ring Forming Based on Casting Ring Blank

Bearing ring is the crucial component of bearing. With regard to such problems as material waste, low efficiency and high energy consumption in current process of producing large bearing ring, a new process named ＂casting-rolling compound forming technology＂ is researched by taking the typical 42CrMo slew bearing as object. Through theoretical analysis, the design criteria of the main casting-rolling forming parameters are put forward at first. Then the constitutive relationship model of as-cast 42CrMo steel and its mathematical model of dynamic recrystallization are obtained according to the results of the hot compression experiment. By a coupled thermal-mechanical finite element model for radial-axial rolling of bearing ring, the fraction of dynamic recrystallization is calculated and recrystallized grains size are predicated. Meanwhile, the effects of the initial rolling temperature and feed rate of idle roll on material microstructure evolution are analyzed. Finally, the industrial rolling experiment is designed and performed, based on the simulation results. In addition, mechanical and metallographic tests are conducted on rolled bearing ring to get the mechanical parameters and metallographic structure. The experimental data and results show that the mechanical properties of bearing ring produced by casting-rolling compound forming technology are up to industrial standard, and a qualified bearing ring can be successfully formed by employing this new technology. Through the study, a process of forming large bearing ring directly by using casting ring blank is obtained, which could provide an effective theoretical guidance for manufacturing large ring parts. It also has an edge in saving material, lowering energy and improving efficiency.

双金属复合构件离心铸造技术

轧辊、无缝管和环类零件等是核电火电、石油化工和大型轧机等高端装备的关键基础构件,具有承载、连接和传动等作用,品种多、用量大、用途广。单一金属材料轧辊、无缝管和环件在性能上越来越难以满足重大装备在极端严酷环境下的服役性能要求,如在高磨损、高腐蚀环境下不仅需要考虑构件材料本身的力学性能,还必须采用抗磨损、抗腐蚀合金提高构件的力学性能和延长其使用寿命。因此,将具有不同性质的两种材料复合在一起组成双金属复合构件,可以实现两种单一金属组元性能的优势互补。单侧性能要求较高时,双金属构件可以取代稀有、贵重金属,在深空探测、风电、石化和远洋船舶等领域应用广泛。由于双金属材料成分、结构和性能的差异,其复合界面形态与结合特点是该类构件制造的关键。经过多年的研究与发展,已实现了复合辊、复合管等双金属复合构件离心铸造技术生产。双金属复合辊为外层卧式离心铸造、内层重力填充铸造,双金属复合管内、外层均为典型的卧式离心铸造,双金属结合界面形态受外层浇注温度、内外层浇注间隔时间和铸型转速的影响,结合层厚度的影响因素主要为浇注温度和凝固方法,复合构件性能主要取决于结合界面的性能;在复合辊和复合管离心铸造过程中,加以电磁控制和多元合金变质处理,以及离心铸造复合后进行阶梯热处理,均能够改善结合界面形态与成分分布均匀性,从而提高其结合性能,离心铸造复合成形机理主要为冶金结合。本文综述双金属复合构件离心铸造技术的研究现状,以典型双金属复合辊和复合管为研究对象,分析其离心铸造工艺特点与成形规律,探讨工艺参数对结合界面和结合性能的影响规律,揭示离心铸造过程中的组织演变机理,指出双金属构件离心铸造中存在的问题。结合盘状类环形零件的特点,展望双金属离心铸造复合构件的发展趋势与重点研究内容。

Fractal Characteristics and Microstructure Evolution of Magnetron Sputtering Cu Thin Films

How to describe surface morphology characteristic and microstructure evolution are the hottest researches of current thin film researches. But in traditional characterization of surface morphology, the roughness parameters are scale related. And the microstructure evolution of thin film during post-treatment is usually not considered in detail, To give a better understanding of the roughness of thin films topography, fractal method is carried out. In addition, microstrueture evolution of thin films is analyzed based on the crystallography and energy theory. Cu thin films are deposited on Si （100） substrates by magnetron sputtering, and then annealed at different temperatures. Surface topography is characterized by atomic force microscope （AFM）. Triangular prism surface area （TPSA） algorithm is used to calculate the fractal dimension of the AFM images. Apparent scale effect exists between the surface morphology roughness and film thickness. Relationship between the fractal dimension and roughness is analyzed by linear regression method and linear relationship exists between fractal dimension and surface roughness root mean square （RMS）. Fractal dimension can be characterized as a scale independence parameter to represent the complex degree and roughness level of surface. With the increase of annealing temperature, surface roughness and fractal dimension decrease. But when the annealing temperature exceeds the recrystallization temperature, due to the agglomeration and coalescence of Cu grain, surface roughness and fractal dimension increase. Scale effect and changing regularity of grain growth and shape evolution for different film thickness under different annealing temperatures are analyzed. Based on minimum total free energy, regularity of grain growth and changing is proposed. The proposed research has some theory significance and applicative value of Cu interconnect process and development of MEMS.

桡骨远端手术B超引导下不同入路神经阻滞的效果

目的分析B超引导下腋路、肌间沟及锁骨上不同入路神经阻滞在桡骨远端手术中的应用效果。方法将我院收治的90例桡骨远端骨折患者随机分为A组、B组及C组,每组30例;A组采用肌间沟入路臂丛神经阻滞术治疗,B组采用腋路臂丛神经阻滞术治疗,C组采用锁骨上入路臂丛神经阻滞术治疗;观察三组患者操作时间及手术时间;统计所有患者痛觉消失时间,操作完成后采用针刺法对神经支配区痛觉进行评价;对患者各神经支配的感觉阻滞进行评价;分析患者局部麻醉药中毒、血肿、膈神经阻滞、术中止血带反应等并发症情况。结果三组操作时间及手术时间差异无统计学意义(P>0.05);三组患者前臂外侧皮神经及桡神经分支痛觉消失时间差异无统计学意义(P>0.05),B组患者前臂内侧皮神经、尺神经及正中神经分支痛觉消失时间低于A组及C组(P<0.05);B组患者麻醉效果优良率高于A组及C组(P<0.05);三组患者镇痛持续时间差异无统计学意义(P>0.05);三组患者并发症差异无统计学意义(P>0.05)。结论相较于前臂内侧皮神经、尺神经阻滞,腋路臂丛神经阻滞效果更好。

环坯壁厚对铸辗连续成形的高温出模铸坯裂纹的影响

环件的短流程铸辗连续成形工艺中,高温出模环坯容易在表面和边角部产生裂纹。利用Procast模拟,探讨了42CrMo离心铸造环坯壁厚对裂纹形成的影响,提出了抑制裂纹的措施。结果表明:环坯出模时温度分布不均匀、与环境温差大,导致热应力应变大,是裂纹形成的主要原因。为避免裂纹形成,宜选用外径与内径比为1.5左右壁厚的环坯。采用金属型内壁覆砂,设计模具为圆角,可降低高温环坯局部应力集中,减小裂纹敏感性。研究结果可为新工艺实现提供重要理论指导。

Q345/40Cr钢双金属环件的热处理工艺及组织性能

对热辗扩Q345钢/40Cr钢双金属环件进行860~950℃淬火和520~610℃回火处理,并对热处理后的组织和性能进行了观察、分析和测试。双金属环件在890℃淬火后,进行不同温度回火,测试其力学性能。结果表明,淬火后晶粒细化,随着淬火温度的升高,晶粒变大。40Cr钢硬度先下降后升高,Q345钢硬度稍微下降,结合层靠近40Cr钢一侧硬度先下降后升高,靠近Q345钢一侧硬度下降。在860℃淬火时,40Cr钢一侧合金元素未完全溶解,在890℃淬火效果最佳。随着回火温度的升高,双金属环件的抗拉强度和硬度下降;40Cr钢的伸长率提高,Q345钢和结合层的伸长率先升高后降低;双金属环件的冲击性能提高。结合层断口在Q345钢一侧。双金属环件在890℃淬火、550℃回火后综合性能最好,可以满足实际使用要求。

铸态42CrMo钢高温拉伸变形中工艺参数和动态再结晶对空洞演化的影响及微观损伤机理分析

用热模拟实验机对铸态42CrMo钢进行高温拉伸实验,分析了断口及断口附近的微观组织、空洞演化与温度、应变速率及应变之间的关系,探讨了工艺参数和动态再结晶行为对空洞演化的影响,研究了铸态42CrMo钢的微观损伤机理。结果表明:铸态42CrMo钢的变形温度控制在1423~1473 K,并控制应变速率和应变,可以抑制高温拉伸变形中的空洞萌生、长大和聚集;发生动态再结晶行为时,微空洞不易形核和长大,空洞之间聚集的间距减小,增加了断裂应变;铸态42CrMo钢高温拉伸变形过程中,氧化硅、硫化锰、氧化铝和氧化钙等夹杂物的脱落或破裂导致空洞形核,且马氏体晶粒之间也可形核。