K418与42CrMo异种金属激光焊的关键问题

研究了额定功率为3 kW的Nd:YAG激光焊焊接K418与42CrMo异种金属,通过光学显微镜、扫描电镜和能谱仪分析了接头组织和成分.结果表明:由于K418与42CrMo热物理性参数的差异,焊缝靠近42CrMo侧易出现未熔合;在扫描电镜下焊缝区观察到裂纹,裂纹处的能谱分析表明:Mo,Al,Nb,Ti元素聚集.由于深熔焊焊接过程匙孔的不稳定和保护气流量大小等因素的影响,焊缝中易形成气孔.为了获得优良的焊接接头力学性能,需要优化焊接工艺参数,抑制焊缝区的未熔合、裂纹和气孔的形成.     

异种金属和镀层金属的焊接

20095214K418与42CrMo异种金属激光焊的关键问题／庞铭…／／焊接．-2009（5）：61-63 研究了额定功率为3kW的Nd：YAG激光焊焊接K418与42CrMo异种金属,通过光学显微镜、扫描电镜和能谱仪分析了接头组织和成分。结果表明：由于K418与42CrMo热物理性参数的差异,焊缝靠近42CrMo侧易出现未熔合;在扫描电镜下焊缝区观察到裂纹,     

K418与42CrMo异种金属激光深熔焊接

研究了连续波Nd:YAG激光焊接功率、速度、离焦量和侧吹保护气流量对激光深熔焊接K418与42CrMo异种金属焊缝形貌、焊缝熔深的影响,讨论了焊缝区热裂纹产生机制.结果表明,额定功率为3 kW的Nd:YAG激光深熔焊接K418与42CrMo异种金属,由于它们的物理化学性质的差异,焊缝靠近42CrMo侧易出现未熔合;激光光斑向42CrMo侧偏移可以减少焊缝靠近42CrMo侧未熔合量;通过优化侧吹保护气流量和离焦量可以增加熔深.由于K418液态金属的流动性差,导致焊缝靠近K418侧对流传热不充分,使焊缝靠近K418侧熔合线呈现锯齿形.焊缝区热裂纹的产生主要是由于焊缝区元素偏析形成的低熔物导致.     

K418/42CrMo异金属连续驱动摩擦焊研究

采用连续驱动摩擦焊对K418/42CrMo异金属进行了焊接工艺试验,对焊接接头抗拉强度、断口形貌、金相组织、显微硬度等进行分析.结果表明:焊接接头质量良好,抗拉强度达到700MPa以上,焊缝区域有碳元素从42CrMo侧向K418侧转移扩散现象.     

TiAl合金与异种材料的摩擦焊接

TiAl合金与42CrMo直接摩擦焊接性较差,为此分别引入高温合金GH3039、K418、N80A和纯镍N6作为中间材料,对TiAl-GH3039/K418/N80A/N6-42CrMo异种材料的摩擦焊接工艺进行了研究。采用硬度计、扫描电镜和电子万能试验机对焊后接头区域的硬度、组织和焊合区成分变化以及接头力学性能进行了分析。研究表明,TiAl合金与异种材料焊后接头中形成了复杂的多层状金属间化合物;TiAl合金与GH3039、N80A的摩擦焊接性较好,与K418、N6的摩擦焊接性较差;根据不同材料线膨胀系数随温度的变化规律、与TiAl合金摩擦焊接后接头的性能及其与42CrMo的摩擦焊接性,最终选择GH3039作为中间材料。通过引入中间材料,摩擦焊制备了TiAl合金涡轮-42CrMo转轴的异种材料整体转子,使得TiAl合金在涡轮增压器领域的应用成为可能。     

K418/42CrMo连续驱动摩擦焊接头动态再结晶研究

采用连续驱动摩擦焊对K418/42CrMo进行焊接,对焊接接头金相组织等进行分析.结果表明:K418/42CrMo焊缝冶金结合面积大,42CrMo钢发生软化并流动,K418合金侧紧靠焊缝处组织发生再结晶,晶粒组织呈细小均匀的等轴晶特征.     

异种金属和镀层金属的焊接

镁铝异种金属焊接研究现状与进展;K418与42CrMo异种金属激光深熔焊接     

K418涡轮盘与42CrMo轴异种材料惯性摩擦焊研究

采用惯性轴向摩擦焊技术对镍基K418高温合金与42CrMo调质钢两种异种材料进行了焊接工艺试验,并分析焊接接头的显微组织,测试其力学性能.结果表明,惯性摩擦焊过程中发生摩擦面转移现象,碳原子扩散导致K418侧含有少量非连续网状碳化物,焊接界面两侧硬度均匀过渡,焊接接头抗拉强度均在750 MPa以上,整体抗拉强度高,获得了优良的焊接接头,惯性摩擦焊工艺适合于焊接异种材料.     

K418和42CrMo激光深熔焊焊缝形貌预测及验证

激光深熔焊热源模型反映焊接熔池热流分布情况,模型的准确性决定模拟结果的有效性。针对K418与42CrMo特有的焊缝形貌,在综合考虑了材料的热物性参数随温度的变化、熔池相变潜热和焊缝正面等离子体附加热源效应,建立了锥形热源与峰值热流逐渐衰减的圆柱复合热源。采用ANSYS软件模拟了激光深熔焊接K418与42CrMo异种金属焊缝形貌。通过试验验证表明:数值模拟焊缝形貌与试验基本吻合,说明了模型的有效性。     

42CrMo转子轴与Q235B辐板焊接工艺

风力发电机转子为合金钢42CrMo和Q235B异种钢焊接结构,采用SMAW和MAG复合热源焊对其进行焊接试验,通过金相显微镜、万能力学试验机和扫描电镜等分析方法观察和分析接头的组织性能及冲击断口形貌。结果表明:焊接热输入的增加会降低42CrMo和Q235B焊接接头的弯曲性能及低温冲击性能,实际电机转子焊接时应控制焊接热输入、预热温度和层间温度;小热输入焊接工艺制备的42CrMo和Q235B异种钢焊接接头的金相组织、力学性能和冲击断口形貌等技术指标满足企业相关规范,对后续的电机转子的焊接提供有力的技术支持。     

Microstructures and mechanical properties of Ti–24Al–17Nb (at.%) laser beam welding joints

Laser beam welding of Ti–24Al–17Nb (at.%) alloy was conducted to investigate the microstructures and the mechanical properties of its joints. The results indicated that the weld microstructure consisted primarily of retained ordered β phase (namely B2 phase) and was independent of the laser welding parameters, while the size and the orientation of the weld solidification structures and then the bend ductility of the joints were related to the welding conditions. The microstructures became coarser and the strains of inducing crack and fracturing decreased as the heat input increased. The fracture occurred in the base metal when the transverse tensile test of the joints was conducted. The tensile strength of the joints was equal to that of the base material and the tensile ductility could reach 12∼17%, which was near to that of the base material.     

High power laser welding of Nb microalloyed steel plates

Abstract

Laser welding studies on 12 mm thick Nb microalloyed steels were done using a 25 kW CO₂ laser at welding speeds of up to 3 m min^?1 with the aim of identifying the influences of Nb and carbon on laser weldability and weld properties. Welds were examined for solidification flaws, penetration characteristics, microstructure and mechanical properties. Solidification cracking did not appear to be influenced by carbon or Nb in the ranges studied when welding at power levels between 22 and 25 kW. The area fraction of martensite was shown to increase with decreasing energy input and increasing carbon content. Weld metal toughness was improved by reducing carbon content in the range 0·08–0·05%C but was little influenced by Nb. Weld metal and heat affected zone hardness levels were reduced, as expected, by reducing carbon content. The results show that increasing Nb content leads to higher strength material without significant loss of toughness, while lowering carbon content can improve toughness without loss of strength. Thus low carbon Nb microalloyed steels with about 0·05%C can achieve a good combination of parent plate and laser weld properties and appear to be suitable for high power laser welding situations.     

Mechanisms of joining aluminium A6061-T6 and titanium Ti–6Al–4V alloys by cold metal transfer technology

Abstract

Cold metal transfer (CMT) welding–brazing joining of Ti6Al4V and Al A6061-T6 was carried out using AlSi₅ wire. The joining mechanisms and mechanical properties of the joints were identified and characterised by scanning electron microscope, energy dispersive spectroscopy and tensile–shear tests. Desired CMT joints with satisfied weld appearances and mechanical properties were achieved by overlapping Ti on the top of Al. The joints had dual characteristics of a welding joint on the aluminium side and a brazing joint on the titanium side. Three brazing interfaces were formed for the joint, which increased the strength of the joint. An intermetallic compound layer was formed at the brazing interface, which included Ti₃Al, TiAl and TiAl₃. Two different fracture modes were also observed: one fractured at the welding/brazing interface and weld metal and the other at the Al heat affected zone (HAZ). Clearly, the joints fractured at the Al HAZ had higher tensile strength than those fractured at the welding/brazing interface and weld metal.     

热输入对海工用钢不同合金系焊缝金属韧性的影响

为探究不同合金系焊缝金属对热输入的适应性,用Si-Mn,Si-Mn-Ni,Si-Mn-Ti-B三种合金系的焊材分别以24和35 kJ/cm的热输入对420 MPa低合金高强度钢板进行埋弧焊. 经过冲击、拉伸、硬度试验及光学显微镜、扫描电镜分析,对熔敷金属的组织、性能进行研究. 结果表明,随着热输入增加,再热区比例增大,晶粒长大,三种合金系的韧性均下降,其中Si-Mn合金系对大热输入的适应性最差,脆性转变温度由?70 ℃降到?65 ℃;Si-Mn-Ni合金系析出大量呈方向性的贝氏体,恶化韧性;而Si-Mn-Ti-B合金系提供大量高熔点含Ti的形核质点,促进针状铁素体形成,改善韧性.     

CO_2激光焊接600MPa DP钢接头组织与性能

采用CO2激光对抗拉强度为600MPa,厚度1.4mm的DP钢进行焊接.研究焊接速度对焊缝外观和截面成形的影响、接头的组织特点、硬度、强度和成形能力.结果表明,激光功率相同,焊接速度较低时焊缝易产生气孔,焊接速度较高时易发生飞溅;焊接速度对焊缝熔深及熔宽也有影响.焊缝区组织主要由马氏体构成,从焊缝、焊接热影响区到母材,组织中马氏体含量下降,接头的最高硬度出现在焊缝或热影响区.在平行于焊缝方向,焊接接头的抗拉强度高于母材,垂直于焊缝方向,接头的抗拉强度与母材相当.由于焊缝出现马氏体组织,接头的塑性和韧性降低,板材的冲压成形能力下降.     

35CrMo调质钢超窄间隙MAG焊接头组织分析

介绍在低温预热条件下35CrMo调质钢厚板的超窄间隙MAG环缝对接焊的设备与工艺。通过焊接接头的金相观察、硬度测量和拉伸试验,分析其组织分布和力学性能。发现焊缝区和热影响区内的微观组织均为细晶形态,硬度值较高。焊接接头的拉伸实验结果表明,断裂均发生在硬度值较低的焊缝区,但对应强度大大高于该焊丝的抗拉强度。应用超窄间隙MAG焊较低热输入焊接工艺,有利于形成细晶粒的焊缝和热影响区组织,能够通过细晶强化大幅度提高熔敷金属的抗拉强度,这对低合金调质高强钢的工艺设计与应用具有重要的参考价值。     

光斑形式对Ti/Al异种合金激光熔钎焊特性的影响

采用椭圆形和矩形两种光斑形式对Ti/Al异种合金进行了激光填丝熔钎焊的试验研究,分析了不同工艺参数对焊缝成形的影响规律,获得不同热源作用方式下的界面形态规律及其对界面强度的影响.结果表明,采用椭圆形光斑和矩形光斑进行激光填丝熔钎焊均可获得较满意的焊缝成形.其中矩形光斑具有更好的焊接适应性,更容易控制焊缝成形.抗拉强度测试结果表明,椭圆形和矩形光斑接头的最高抗拉强度分别达到铝母材的75%和80%.     

高温钛合金Ti55/Ti60真空电子束焊接

对 Ti55 与 Ti60 合金薄板进行了电子束焊接,研究了电子束焊接工艺参数对接头组织及力学性能的影响.结果表明,焊缝区形成大量针片状的α' 马氏体,焊缝中心为粗大的柱状晶.焊接工艺参数对焊缝组织和接头抗拉强度有一定影响,接头室温抗拉强度高于母材,600℃时接头抗拉强度与 Ti60 母材相当,抗弯强度达到母材的 80% 左右,冲击韧度能够达到母材的 90% 以上,断裂发生在热影响区处,为韧性断裂.

Abstract：

Ti55 and Ti60 titanium alloy sheets were welded by electron beam, and the influences of parameters on microstmcture and mechanical properties of welding joints were studied. The results show that weld zone is characterized by acicular α' martensite plate,and weld center is formed by coarse columnar crystals. Welding parameters can affect microstructure and tensile strength to a certain extent. At room temperature, the tensile strength of joint is higher than that of base metal. At a higher temperature of 600 ℃, tensile strength of joint is about equal to that of Ti60, and bending strength can be up to 80% of that of base metal, even impact toughness also can be larger than 90% of base metal. Failure occurs in heat-affected zone, and the fracture mode shows toughness characteristic.     

Tensile resistance,microstructures of intermetallic compounds,and fracture modes of welded steel/aluminum joints produced using laser lap welding

The joining of DP780 steel to Al5052 was conducted by laser lap welding, in which the metal vapor and spatters were monitored by a high-speed camera. A universal testing machine was used to test the mechanical properties of the welded joints, and the changing law of lap tensile resistance with the laser welding parameters was analyzed. Optical microscope and scanning electron microscope were used to observe the macro-structure and micro-structure, respectively. Three different intermetallic compounds (IMCs) phases, i.e. banded Fe₂Al₅, FeAl₂ and needle-like FeAl₃ were generated at the steel/Al interface on microscopic observation. The aim of this research is to investigate the relationship among the lap tensile resistance, the welding parameters and the failure mode under different energy densities. Experimental results showed that the steel/Al joints have two different fracture modes at low heat input and high heat input. The failures happened along the heat-affected zone of the weld and along the steel/Al joint interface, respectively. And both of the two failure modes are brittle fractures. Additionally, cracks appeared at the fracture interface, and needle-like particle clusters were found in the fracture microstructure.