焊后热处理对P92钢焊缝冲击性能的影响

对P92钢焊后热处理试样的焊缝冲击性能进行研究。P92钢焊接接头断面硬度分析结果表明,厚壁P92钢管道现场焊后热处理时,形成了外层温度高、内层温度低的温度梯度,导致试件焊缝外层冲击吸收能量平均值比内层的高。焊缝冲击试样经过二次高温回火（770℃×2 h）后,内外层冲击吸收能量差别基本消失,同时平均值有所提高。结果表明,P92钢焊接接头壁厚上的温度梯度对P92钢焊缝冲击性能有重要影响。     

正面随焊超声冲击对焊接变形及组织的影响

焊接工艺中不均匀受热所产生的变形一直是工业生产中的难题。针对焊接残余应力与变形的问题,目前超声冲击技术取得了较好的效果,当温度较高时,材料的变形抗力减小。搭建了正面随焊超声冲击实验平台,在3mm厚的Q235B钢材薄板上进行正面随焊超声冲击实验,主要探究焊接变形及焊缝处晶粒变化与冲击距离之间的关系,当d=45 mm时,变形较常规焊减少43.3%,即高温冲击时变形减少效果最为明显。同时发现,在正面随焊冲击作用下,焊缝晶粒细化,尤其是当冲击距离小时细化效果最明显。     

G115钢管埋弧自动焊焊缝冲击性能不足的原因分析及热处理修复措施

采用埋弧自动焊(SAW)对大口径厚壁G115钢管进行焊接,焊后经785℃回火后发现焊缝冲击吸收能量低于标准要求的最低值。通过对焊接方法、焊材及回火温度的分析和试验表明,焊缝的回火温度超出了熔覆金属的Ac₁点,产生不完全相变组织,且碳化物回溶、沉淀强化作用减少、马氏体亚结构和位错密度降低、析出相长大粗化等多种因素的交互作用最终造成了焊缝冲击性能的下降。采用1080℃×3 h正火+770℃×6.5 h回火的热处理修复后,焊缝的冲击性能得到大幅度的提升。     

钢轨连续闪光焊送进速度对焊接过程的影响

影响钢轨闪光焊接头焊接质量的因素很多,其中焊机动力柱的送进速度就是重要因素之一。有效地控制钢轨连续闪光焊的动力柱送进速度,可以使整个焊接过程保持连续和稳定的闪光,从而获得优良的焊接接头。通过波形分析和对消耗的电能计算表明：将PID调节与ON-OFF控制调节两种方式结合使用,能有效控制动力柱送进速度．保证钢轨焊接接头质量,提高生产效率,节约能源。     

填丝速度对不锈钢埋弧焊焊缝成形及组织的影响

为降低不锈钢埋弧焊熔池过热度,减少焊道间冷却时间,研究了1.0～5.0 m/min不同填丝速度对不锈钢焊缝熔敷率、焊缝成形及焊缝组织的影响,并与单丝埋弧焊进行对比.研究表明,在填丝速度为3.0 m/min时,熔敷金属的铺展性和焊缝表面成形最佳,焊缝熔深为1.54 mm,焊缝金属熔敷率提高45％;同时,焊缝微观组织得到一...     

激光再流焊焊接速度对SOP器件焊点力学性能的影响

分别采用半导体激光再流焊与红外再流焊方法钎焊SOP器件,研究了激光焊焊接速度对其焊点抗拉强度的影响,并对焊点断口形貌进行了分析.结果表明,在激光再流焊条件下,激光焊焊接速度对SOP器件焊点的抗拉强度有显著的影响,而Sn-Pb焊点的力学性能对焊接速度的敏感度低于Sn-Ag-Cu无铅焊点,且存在一个最佳焊接速度.通过SEM观察发现,焊接速度相对慢时,断口有浅显韧窝和微孔,焊点断裂类型为微孔聚合型断裂;速度过快时,断口有较多的韧窝群,并且局部区域还有台阶,焊点断裂类型为韧窝型断裂和解理型断裂;焊接速度适中时,断口韧窝大且深,焊点断裂类型为韧性断裂.     

焊件冷却速度的影响及特征参数的应用

本文概述了焊件冷却速度的物理意义及特征参数,介绍了t对接头性能的影响及工程应用。结果表明,通常采用某一温度区间的冷却时间。等特征参数来代替瞬时冷却速度。对低碳低合金钢而言,过大或过小的。对接头的韧性均不利,对焊接接头中氢的扩散、逸出及聚集等均有重要影响。预热和后热在降低接头的冷却速度、改善焊接性、防止冷裂纹发生效果明显。多种控制冷速工艺的联合运用,其优势凸显。工件预热150℃＋焊后缓冷工艺,在掘进机滚筒焊接结构中成功应用,表明了该工艺的实用价值和推广意义。     

Ti和B含量对H08C埋弧焊熔敷金属冲击性能的影响

研究了不同 Ti和B含量对H08C焊丝配合自主研发的高碱度焊剂所得熔敷金属冲击性能的影响,发现随着熔敷金属中Ti和B含量增加,熔敷金属的冲击性能都降低,尤其B,对冲击性能的不利影响远大于Ti.     

焊接速度对双丝CO2焊的影响研究

利用研制的双丝数字化焊接电源系统搭建焊接工艺实验平台,通过大量的工艺实验,利用自行研制的四通道焊接电弧动态小波分析仪对两组电流、电压同时采样,全面测试所设计的电源。根据焊接过程采集的电流电压波形图和焊缝照片,对比分析了不同焊接规范的焊接效果。进一步找出焊接速度对焊接效果的影响规律。实验结果表明该双丝数字化焊接电源能够有效实现双丝CO2焊接,且焊接质量较为优异。     

Zr44Ti11Ni10Cu10Be25块体非晶合金与金属铝箔的扩散连接

采用铜模吹铸法制备出Zr44Ti11Ni10Cu10Be25块体非晶合金,并在真空扩散焊设备中与铝箔进行扩散焊接,研究了锆基非晶合金与Al箔进行超塑性扩散焊连接工艺及其连接界面的原子扩散情况。结果表明,元素的扩散情况与试样的变形量有关,但变形量又不完全影响元素的扩散,而是当变形量达到一定值时,温度越高,元素扩散程度越高。当温度达到713K、变形量达到26%时,元素的扩散程度最高。     

Simulation and instrumentation of electromagnetic compression of steel tubes

The near-axisymmetric compression of high strength steel tubes by electromagnetic forming is studied both experimentally and analytically. Tubes with a nominal tensile strength of 440 MPa, outer diameters of 75 mm and wall thicknesses up to 2.3 mm were compressed using a 9 turn helical actuator and discharge energies up to 24 kJ. This can produce reduction in diameters beyond 15%. Experiments were instrumented for measurement of velocity, as well as primary and induced current during the experiments. These records were compared to those of a simple numerical model and found to be in close agreement both in final tube diameter as well as temporal behavior of current and velocity. The model is also exercised to consider system design outside the space examined experimentally. The present experiments also clearly demonstrated that by reducing the system capacitance, the rise time of the pressure pulse can be decreased and this reduces the tendency for Euler bucking in the tubes. This results in rounder tubes, which may be more useful as a manufactured product.     

锌锡复合合金化对镁/铝FSLW组织与性能的影响

通过设计正交试验研究了添加Zn箔或Sn箔,以及Zn箔和Sn箔复合添加来进行界面合金化Mg/Al异种合金搅拌摩擦搭接试验。结果表明,进给速度对接头力学性能的影响最大,Zn箔厚度对接头力学性能的影响程度大于Sn箔。在Sn箔和Zn箔厚度均为0.05 mm、焊接速度为110 mm/min、旋转速度为750 r/min时,焊接接头的拉伸剪切强度最大。相较于单独添加Zn箔或Sn箔,复合添加的接头中脆性Mg-Al金属间化合物的含量更低,接头组织主要由Mg-Zn-Al三元相、Mg-Zn金属间化合物组成,接头力学性能比单独添加Zn或Sn时提升了35%左右。     

Vaporizing foil actuator: A tool for collision welding

A method for implementing collision welding at moderate to small length scales has been developed. The flyer, instead of being driven by chemical explosives (explosive welding) or magnetic forces (magnetic pulse welding), is launched toward the target by the pressure created from the electrically driven rapid vaporization of a thin metallic conductor. Mechanical impulse is developed from 0.0762 mm thick aluminum foils, which are vaporized using capacitor bank discharge with nominal charging voltage of 5.5 kV and peak current on the order of 100 kA delivered with rise times of about 12 μs. Welding couples of copper–titanium, copper–steel, aluminum–copper, aluminum–magnesium and titanium–steel have been successfully created with the same input parameters such as foil geometry, input energy and standoff distance. Instrumented peel tests, lap shear tests and optical and scanning electron microscopy reveal a wide spectrum of both strengths and interface structures. Copper–titanium and copper–steel welds are strong and have characteristic wavy interfaces with little intermetallics or void formation. The other combinations are seen to have brittle interfaces with intermetallics and defects, with the collision welding parameters used presently. For the titanium–steel system, a thin nickel interlayer is introduced and all the layers are welded in a single experiment. Peel strength of the weld was observed to be quadrupled. Peak velocities of up to 560 m/s were obtained for titanium flyer sheets.     

Effects of welding velocity on the impact behavior of droplets in gas metal arc welding

The influence of welding velocity on the impact behavior of the globular metal transfer was studied by high speed video photography with a laser source during gas metal arc welding of E36 steel. The welding current and voltage were 180 A and 30 V during the welding process. The results indicated that the impact location of a droplet depended strongly on the welding velocity. There was a critical welding velocity (0.4 m/min) that when the welding velocity was lower than this value the droplet impacted inside the weld pool, while the welding velocity was higher than this value the droplet impacted outside the weld pool. The results showed that when a droplet impacted outside the weld pool it would rebound or adhere on the workpiece, which was depended on the kinetic energy of the droplet. The rebound percentage of droplets increased with increasing kinetic energy. With increasing welding velocity, the mass of droplets was not changed obviously, but the flight velocity of the droplet increased, i.e. the kinetic energy of droplets increased with increasing welding velocity. The results also showed that when a droplet impacted outside the weld pool, the droplet which rebounded away from the workpiece surface formed weld spatters, resulting in discontinuous weld appearance, while the droplet which adhered on the workpiece surface streamed to the weld pool and good weld joint would still be obtained. Molten metal decreases with increasing welding velocity. When the welding velocity increases from 0.4 m/min to 2.0 m/min, the weld width decreases from 12.9 mm to 6.3 mm and the weld penetration decreases from 5.4 mm to 2.1 mm.     

A356铝合金搅拌摩擦焊接热力耦合分析

借助多场耦合求解技术,利用Comsol Multiphysics软件建立了A356.0-T61铝合金搅拌摩擦焊接热力耦合的有限元模型。并利用JMatPro定义了随温度变化的A356铝合金的热物理属性,着重分析轴向下压力、旋转速度、焊接速度等工艺因素对搅拌摩擦焊A356铝合金温度场和应力分布演变规律的影响。结果表明,焊接速度对FSW等温线椭圆形分布形状的椭圆率影响很大;在SAZ的外边缘处焊接等效应力最大,在SAZ的外缘附近区域出现呈离散状态分布的低应力小区域。A356铝合金FSW温度场分布的工艺参数影响的显著性顺序为:焊接速度>搅拌头旋转速度>轴向下压力;焊接应力分布的工艺参数影响的显著性顺序为:轴向下压力>焊接速度>搅拌头旋转速度。     

Corrosion susceptibility of peened friction stir welded 7075 aluminum alloy joints

Effects of surface treatment techniques like laser and shot peening on stress corrosion cracking (SCC) susceptibility of friction stir welded (FSW) 7075 aluminum alloy joints were investigated. This study had two parts; the first part investigated the peening effects on stress corrosion cracking susceptibility in FSW samples by slow strain rate testing in a 3.5% NaCl solution. The second part of the study investigated the effects of peening on corrosion while submerged in a 3.5% NaCl solution with no external loads applied. No signs of corrosion pitting or SCC were evident on any of the tensile samples during the slow strain rate testing. The FSW plates exposed in 3.5% NaCl solution for 60 days were inspected periodically for signs of corrosion and stress corrosion cracking in the areas expected to have residual stresses due to welding. Pitting corrosion was seen on the samples, but even after 60 day exposure no stress corrosion cracking was detected on any of the peened or unpeened samples.     

Quantitative characterization of porosity in Fe–Al dissimilar materials lap joint made by gas metal arc welding with different current modes

5052 Al alloy sheets and galvanized mild steel sheets were joined by gas metal arc welding with three different current modes, including direct-current pulse gas metal arc welding (DPG), alternate-current pulse gas metal arc welding (APG) and alternate-current double pulse gas metal arc welding (ADG). The effect of current mode on size, distribution and volume fraction of pores generated in Fe–Al dissimilar materials lap joint was quantitatively studied. EDS result showed that pores in Fe–Al joint were mainly caused by trapped zinc metal vapor from galvanized steel. Volume fraction of pores in joints made by APG and ADG processes was larger than that in joint resulted from DPG process. Moreover, pores in joints made by APG and ADG processes had smaller diameter, and tended to distribute in the middle of the weld seam. On the contrary, pores with large diameter were inclined to distribute close to upper weld surface of the joint resulted from DPG process. These results are attributed to the difference of arc stirring force and linear heat input in these three processes caused by different current modes.     

地磁场环境下铝合金FSW缺陷微磁信号特征提取研究

搅拌摩擦焊(FSW)作为一种新型的固相焊接方法,所形成的焊缝中易含有紧贴型、取向复杂的微细尺寸缺陷。针对铝合金FSW焊缝检测高精度、高分辨率的检测需求,根据7A09铝合金在地磁场环境下所具有的弱顺磁性,提出一种基于铝合金自身磁信号分布的微磁检测方法。通过高精度测磁传感器采集铝合金FSW焊缝表面微弱的磁感应强度变化信号,利用小波变换的多尺度性把焊缝缺陷处的磁异常信号精确地从复杂的原始磁感应强度信号中提取出来,将焊缝缺陷信息直观地映射到分离出的d1信号曲线上。结果表明,微磁检测方法对铝合金FSW焊缝中微细缺陷的检测精度可达到0.2 mm,对缺陷位置的检测误差仅为1.67%,能够实现对铝合金FSW焊缝全覆盖式、高可靠性的无损检测。