焊接工艺参数对FGH96合金惯性摩擦焊过程材料塑性流动行为的影响

采用数值模拟方法对FGH96合金惯性摩擦焊过程进行分析,获得温度、轴向缩短量、材料流动与飞边四者之间的关系,着重研究初始转速与轴向压力等焊接工艺参数对材料塑性流动行为的影响规律。研究结果表明:在惯性摩擦焊初始阶段,材料温度与流动速度较低,无飞边产生;随着焊接过程的进行,材料的温度与流动速度呈现先升高后降低的规律;在焊接过程进入稳态后,摩擦面中心区域的材料主要沿试件的旋转方向流动,而摩擦面上两边界附近的材料向面外流动并形成飞边,飞边尺寸与弯曲程度随焊接时间的增加而增加。同时,随到摩擦面距离的增加,材料的流动速度逐渐降低且材料沿轴向流动的速度分量增大。结合FGH96合金惯性摩擦焊轴向缩短量的数值模拟结果,解释了从提高材料流动速度的幅度上看增加轴向压力优于初始转速的原因。     

A new current hybrid inertia friction welding for nickel-based superalloy K418–alloy steel 42CrMo dissimilar metals

The nickel-based superalloy K418 and alloy steel 42CrMo dissimilar metals friction welding joints lack strength and toughness due to high hardening and poor joining quality at the friction interface. To resolve this issue, a new current inertia friction welding (CIFW) method is carried out by hybrid an external additional electronic current in inertia friction welding (IFW) process. The characteristics of welding formation, the elements’ diffusion, and the mechanical properties of K418–42CrMo dissimilar metal joints are studied by scanning electron microscope, energy dispersive spectrometer, and X-ray diffractometer tools. The experimental results show that hybrid additional electronic current has a significant positive influence on interface characteristics of IFW joints. The required welding time for CIFW to complete a good qualified joint is shortened due to mixture actions of both friction heat and resistance heat. The width of the element diffusion zone increases in CIFW joints, and elements in 42CrMo side diffuse through the K418/42CrMo interface into the K418 side in CIFW joints. The width of the K418/42CrMo bonding interface increases in CIFW joints. The microhardness at the K418/42CrMo bonding interface is decreased in CIFW joints. The mechanical tensile property of CIFW joints is increased obviously. The interface bonding pattern becomes jagged and interlocking perfect formations. These above changes improve the joining quality of K418–42CrMo dissimilar metal friction welding joints. The heat treatment effect and resistance heat effect originated from hybrid external electronic currents are discussed by comparing CIFW with IFW. A new model is proposed to illustrate the interface’s evolution and development mechanism in K418–42CrMo dissimilar metal CIFW.     

Inertia friction welding process analysis and mechanical properties evaluation of large rotor shaft in marine turbo charger

The two aims of this study are first, determining the optimal welding process parameters by using the finite element simulation and second, determining the optimal tempering temperature by evaluating the mechanical properties of friction welded part for manufacturing large rotor shaft. Inertia welding was conducted in order to make the large rotor shaft of turbo charger for low speed marine diesel engine. The rotor shaft is composed of the 310mm diameter disk and the 140mm diameter shaft. Since diameters of disk and shaft are very different, the integration using friction welding reduces manufacturing cost compared with the forming process of which a disk and shaft are forged into one body. Finite element simulation was performed, because inertial welding friction process depended on many process parameters, including axial force, initial revolution speed and energy, amount of upset, and working time. It is expected that this modeling will significantly reduce the number of experimental trials needed when determining the optimal welding parameters. Inertia welding was carried out with optimal process parameter conditions obtained from the simulation results. Welded joint part, made by friction welding, had very poor mechanical properties, and so it required heat treatment. The base material used in the investigation was SFCMV1 (SANYO special steel, high strength low alloy Cr-Mo steel) of 140mm diameter. In the study, heat treatment test carried out quenching (950 °C, 4hr, oil cooling) and tempering (690–720 °C, 6hr, air cooling) for friction welding specimens. The various tests, including microstructure observation, tensile, hardness, and fatigue tests, were conducted to evaluate the mechanical properties under various heat treatment conditions after inertia welding.     

摩擦焊接初始阶段的摩擦机制及摩擦系数

对影响摩擦焊接初始阶段温度场的摩擦机制及摩擦系数进行了实验研究。结果表明：在摩擦焊接初始阶段，摩擦表面的摩擦机制主要为粘着摩擦，在外缘区域存在着氧化摩擦。文中还通过回归方法建立了ＧＨ２１３２材料摩擦焊接初始阶段摩擦系数与摩擦压力、摩擦速度及表面温度之间的经验公式。     

Effect of process parameters on tensile strength of friction stir welding A356/C355 aluminium alloys joint

In the present investigation, A356/C355 aluminium alloys are welded by friction stir welding by controlling various welding parameters. A356 and C355 aluminium alloys materials have a set of mechanical and physical properties that are ideally suited for application in aerospace and automobile industries and not widely used because of its poor weldebility. To overcome this barrier, weldebility analysis of A356 and C355 aluminium alloys with high speed steel (Wc-Co) tool has been investgated. An attempt has been made to investigate the influence of the rotational speed of the tools, the axial force and welding speed on tensile strength of A356/C355 aluminium alloys joint. The experiments were conducted on a milling machine. The main focus of investigation is to determine good tensile strength. Response surface methodology (box Behnken design) is chosen to design the optimum welding parameters leading to maximum tensile strength. The result shows that axial force increases, tensile strength decreases. Whereas tool rotational speed and welding speed increase, tensile strength increases. Optimum values of axial force (3 /KN), tool rotational speed (900 RPM) and welding speed (75 mm/min.) during welding of A356/C355 aluminium alloys joint to maximize the tensile strength (Predicted 223.2 MPa) have been find out.     

Comparative investigation on grindability of K4125 and Inconel718 nickel-based superalloys

Nickel-based superalloy is a typical hard-to-machining material in the aero-engine manufacturing industry. The grindability difference of two kinds of nickel-based superalloys, i.e., equiaxed cast nickel-based superalloy K4125 and wrought nickel-based superalloy Inconel718, are discussed in this article. The influence of grinding parameters (e.g., grinding speed, workpiece speed, and depth of cut) on the grinding force, grinding temperature, and ground surface quality are explored. The results illustrate that under the given grinding conditions, grinding K4125 generates higher forces than Inconel718. The temperature from the K4125 grinding process is beyond 400 °C, while the temperature from grinding on Inconel718 is below 200 °C. Moreover, because of the chip adhesion on the wheel surface when grinding K4125, not only the wheel wear is more severe but also the ground surface of K4125 is worse than that of Inconel718. Accordingly, it could be inferred that the grindability of K4125 is worse than that of Inconel718.     

PCBN刀具高速切削镍基高温合金切削力及刀具磨损试验研究

高速切削加工过程中切削参数的选择对刀具切削性能具有较大的影响。镍基高温合金因在高温条件下仍具有较高的抗疲劳强度、屈服强度、抗拉强度等特点,被广泛应用于航空航天、船舶、核电等行业。但是镍基高温合金的切削加工性能差,主要表现在切削力大、切削温度高、刀具磨损现象严重等方面。本文从切削速度、进给量、切削深度等切削参数对切削力的影响进行研究,同时对PCBN刀具磨损形貌进行分析。采用PCBN刀具进行高温合金车削试验,得到PCBN刀具切削高温合金GH4169时切削参数对切削力的影响规律,并探讨不同刀具磨损形貌产生的原因,为高温合金高速切削加工参数制定及工艺优化提供一定参考。     

Numerical modeling to understand liquation cracking propensity during laser and laser hybrid welding (I)

Two-dimensional thermal elasto-plastic model was established by finite element method to investigate weld heat-affected zone (HAZ) liquation cracking behavior during laser and laser–gas metal arc (GMA) hybrid welding nickel-based superalloy. Transient temperature, cooling rate, and stress and strain history were used and combined with solidification theory to analyze the mechanism of liquation cracking in the HAZ. Weld cracking mechanical driving force is related to local stress–strain development at the period of solidification, and stress and strain components were correlated along the fusion boundary of weld pool. Strain rate and weld pool geometry were demonstrated during in the stage of solidification process, which provide valuable insight into the quantitative evaluation the tendency of solidification cracking and give well understanding why laser–GMA welding is beneficial for minimizing cracking susceptibility than laser welding.     

耗材摩擦焊中的耗材过渡与成形机理研究

以 1 Cr1 8Ni9Ti为耗材在低碳钢母材表面进行了摩擦焊敷试验。观察测量了不同工艺参数匹配下耗材金属的过渡行为和真实接触面的大小 ,阐明了耗材金属的过渡机理和真实接触面的变化规律及影响因素 ;以特征流线为依据 ,建立了过渡金属形成初始焊敷层的物理模型并分析了摩擦碾压作用对焊敷层最终成形和界面连接过程的影响。研究表明 ,耗材金属是通过真实接触面过渡到母材表面的 ,真实接触面位于旋转界面的中心区域 ,其大小随耗材转速和摩擦压力的增大而减小 ;真实接触面两侧不对称的温度分布是推动耗材金属过渡的驱动力 ;摩擦碾压作用是焊敷层最终成形和界面形成可靠连接的决定因素。     

摩擦焊接过程的热力耦合有限元分析

采用热力耦合有限元分析方法,综合考虑摩擦焊接过程中不同的产热机制、随温度变化的材料性能、飞边形成及摩擦系数随速度、温度、压力的变化规律,直接由焊件材料的性能参数及设定的焊接规范参数(轴向压力与转速随时间的变化曲线)对焊接全过程的焊接参数(摩擦转矩、轴向缩短量及平均温度)、物理参量场(温度场、应力场、变形场)及焊合区金属晶粒尺寸的变化规律进行了数值模拟,得到了焊接过程中摩擦表面上切应力、加热功率、温度及轴向压应力的分布及变化规律,实现了对焊合区金属晶粒尺寸的数值模拟。     

GH99镍基合金薄板电子束焊接头疲劳性能研究

电子束焊作为一种先进的连接技术,具有能量集中、焊接速度快、热影响区小等特点,被广泛应用于工业工程、航空航天等国民经济的重要领域。随着航天飞行器发动机设计寿命的不断提高,主要结构部件的电子束焊接头疲劳性能越来越受到设计工作者的关注,研究电子束焊接头的疲劳性能已经成为焊接工作者一个重要的课题。本文采用电子束焊接工艺,制备了GH99镍基高温合金薄板对接接头。针对电子束焊接头,进行了显微硬度测试、疲劳性能的研究及疲劳失效机理分析。研究表明,电子束焊接头焊缝中心及热影响区的维氏硬度与GH99镍基高温合金母材金属基本相同,接头并未出现性能的不均匀性。对两种工艺下的电子束焊接头的疲劳S-N曲线分析表明,适当加大电子束焊焊接电流,有利于减少焊缝焊根部位的焊接缺陷,有利于提高电子束焊接头的疲劳性能,从而提高了焊接接头疲劳寿命。     

基于ANSYS Workbench的盘式制动器热-机耦合分析

为进一步研究盘式制动器在制动过程中的行为,在建立盘式制动器热-机耦合简化计算模型的基础上,考虑温度变化对材料物理性能和摩擦因数的影响,运用ANSYS Workbench模拟分析不同制动初速度与不同制动压力下制动盘的热-机耦合特性,并从制动盘径向、周向、轴向等维度对其温度场与应力场进行了研究。结果表明：盘式制动器在紧急制动过程中,温度和应力的最大值与制动初速度和制动压力成正相关;制动初速度和制动压力对制动盘温度场和应力场有较大的影响,其中制动压力对制动盘温度和应力最大值的影响比制动初速度更加明显;制动盘温度与等效应力在圆周上都呈环带状分布,二者具有一致性,制动盘达到温度最大值早于达到应力最大值,二者之间具有耦合特性;制动盘温度在径向和轴向上存在较大的温度梯度,从而引起较大的应力变化。研究结果为探索制动盘温度场、应力场分布规律和制动盘在不同工作状态下的热-机耦合特性提供了参考。     

Milling of MAR-M247 nickel-based superalloy with high temperature and ultrasonic aiding

This study investigates the properties of machining MAR-M247 nickel-based superalloy combined ultrasonic vibration with high-temperature aided cutting. Taguchi experimental design was adopted to identify the influence of machining parameters on the machining characteristics. The six machining parameters, namely cutting tools for different materials; depth of cut; cutting speed; feed rate; working temperature; and, ultrasonic power. The machining characteristics analyzed include surface roughness, flank wear, cutting force, and milling temperature. According to the experimental results, when the cutting speed is greater than 90 m/min, P-type tungsten-carbide cutters with or without a Ti-alloy coating were unable to endure the very high temperatures generated in milling MAR-M247 nickel-based superalloy. The tungsten-carbide cutters melted and fractured. Due to the insufficient toughness of cermet cutters, the periodic high-impact stress causes severe cutter fractures when the cutting speed is greater than 60 m/min. When the cutting speed was less than 40 m/min, the cutter temperature was not significantly increased. Thus no melting or fracture of the cutters was found. Furthermore, when the cutting speed was less than 40 m/min, and fluid containing nano-particles of 5–23 nm in size was used, the cutter-workpiece friction force was reduced and the cutter life was extended.     

非对称循环载荷下镍基单晶合金低周疲劳损伤研究

通过分析影响单晶叶片低周疲劳寿命的主要因素,对循环塑性应变能的计算方法进行了研讨,认为构成塑性应变能的主要因素应包括循环等效应力范围、全应变范围、晶向参数和平均应力等影响参量,它们与塑性应变能之间呈幂函数关系。利用试验数据对循环塑性应变能与镍基单晶合金低周疲劳寿命之间的相关性进行定量分析,结果表明：循环塑性应变能与镍基单晶合金低周疲劳寿命之间存在着比较密切的相关关系。     

Frictional behaviour of mild steel in friction welding

Experiments were carried out on the friction welding of mild steel tubular specimens having an outside diameter of 19 mm and inside diameter of 12.7 mm. The average rubbing speed was varied from 0.42 m/s to 3.36 m/s and the axial force from 2.4 kN to 19 kN. The resulting variations in the resisting torque, axial force and axial shortening during the welding cycle were measured and recorded.The results obtained indicate that the frictional behaviour of mild steel under these particular conditions is greatly influenced by the rubbing speed and to a lesser extent by the value of force normal to the rubbing surfaces. A theory is proposed for the frictional behaviour of mild steel under these conditions which seems to give a reasonable explanation for most of the observed results.     

铝合金摩擦液柱成形有限体积法数值模拟

为了研究焊接参数对摩擦液柱成形过程的影响,建立了铝合金材料的三维模型,采用有限体积法对该模型进行了数值模拟,得到了塑性化铝合金的流动速度和压力分布情况,并且分析了焊接旋转速度与进给速度对流动速度和压力分布的影响。仿真结果表明,焊接棒附近流动速度较其他区域大,压力高的区域主要集中在焊接模型底部,进给速度对压力的影响大于旋转速度的影响,对于流动速度的影响主要取决于旋转速度。     

油气两相动压密封自振稳定性流固热耦合分析

考虑热与变形对油气两相动压密封自振稳定性的影响,建立基于油气两相动压密封自振稳定性数学模型,采用流固热耦合有限元方法,研究油气比、转速、压差和O形圈阻尼等参数对油气两相动压密封受干扰后的轴向、角向自振稳定性能的影响。结果表明:转速较低时轴向自振稳定性较好而角向自振稳定性较差,转速高时两者相反,O形圈阻尼较低时轴向自振稳定性较差而角向自振稳定性较好,O形圈阻尼高时两者相反,因此在极端转速和取极端O形圈阻尼的情况下轴向或角向临界频率较小,不利于油气两相动压密封自振稳定;压差越大轴向临界频率越大,轴向自振稳定性越好,但角向临界频率越小,角向自振稳定性越差;随着两相介质油气比的增大,轴向临界频率减小而轴向临界质量增大,油气比在0.1～0.15时临界频率、质量以及转动惯量较大,密封综合自振稳定性能较好。     

计算机闭环控制系统在摩擦焊接中的应用

根据摩擦焊接过程质量控制需要 ,建立了摩擦焊接过程计算机电液比例闭环控制系统 ,实现了摩擦焊接过程中轴向压力的闭环控制、滑台进给速度的开环比例控制。生产现场数据统计分析表明 ,采用电液比例计算机闭环控制系统后 ,摩擦压力与顶锻压力的平均误差小于 2 % ,变异系数接近于 0 ,摩擦焊接参数的稳定性大大提高 ,有广泛的应用前景     

Characterization of the tensile properties of friction stir welded aluminum alloy joints based on axial force,traverse speed,and rotational speed

Friction stir welding (FSW) process has gained attention in recent years because of its advantages over the conventional fusion welding process. These advantages include the absence of heat formation in the affected zone and the absence of large distortion, porosity, oxidation, and cracking. Experimental investigations are necessary to understand the physical behavior that causes the high tensile strength of welded joints of different metals and alloys. Existing literature indicates that tensile properties exhibit strong dependence on the rotational speed, traverse speed, and axial force of the tool that was used. Therefore, this study introduces the experimental procedure for measuring tensile properties, namely, ultimate tensile strength (UTS) and tensile elongation of the welded AA 7020 Al alloy. Experimental findings suggest that a welded part with high UTS can be achieved at a lower heat input compared with the high heat input condition. A numerical approach based on genetic programming is employed to produce the functional relationships between tensile properties and the three inputs (rotational speed, traverse speed, and axial force) of the FSW process. The formulated models were validated based on the experimental data, using the statistical metrics. The effect of the three inputs on the tensile properties was investigated using 2D and 3D analyses. A high UTS was achieved, including a rotational speed of 1050 r/min and traverse speed of 95 mm/min. The results also indicate that 8 kN axial force should be set prior to the FSW process.     

高速铣削 Inconel718已加工表面残余应力的有限元分析

利用有限元法对镍基高温合金Inconel 718的高速正交铣削进行模拟仿真,获得切削力、切削温度和残余应力.结果表明在仿真切削速度100-3000m/min范围内,刀尖峰值温度随切削速度提高而增大,由于高温造成工件软化,从而使切削力随切削速度增大而减小;残余应力层深度在已加工表面O.5mm以下,最大表面残余应力为拉应力...