Research on CMT welding of nickel-based alloy with stainless steel

Cold Metal Transfer （CMT） welding technique is a new welding technique introduced by Fronins company. CMT welding of nickel-based alloy with stainless steel was carried out using CuSi3 filler wire in this paper. Effects of welding parameters, including welding current, welding speed, etc, on weld surface appearance were tested. Microstructure and mechanical properties of CMT weld were studied. The results shaw that the thickness of interface reaction layer of the nickel- based alloy is 14. 3 μm, which is only 4. 33% of base material. The weld is made up of two phases, α-copper and iron-based solid solution. Rupture occurs initially at the welded seam near the edge of stainless steel in shear test. The maximum shear strength of the CuSi3 welded joint is 184. 9 MPa.

Characteristic of laser-MIG hybrid welding with filling additional cold wire for aluminum alloy

The weld appearance, deposition rate, welding efficiency, stability of arc, laser keyhole characteristic, and weld property were studied by using a novel laser-MIG hybrid welding process with filling wire of aluminum alloy. The results were also compared with those by conventional laser-MIG hybrid welding process. It was found that with the suitable process parameters this novel welding process for aluminum alloy was stable and final weld bead had fine appearance. Compared to conventional laser-MIG hybrid welding process, during this novel welding process the stability of arc, the laser keyhole characteristic and the weld property were similar, while the keyhole cycle frequency and keyhole opening area had differences of 1.23% and 15.34%, respectively, and the welding efficiency increased by about 31% without increasing heat input.

Effect of filler wire on the joint properties of AZ31 magnesium alloys using CO_2 laser welding

Laser welding with filler wire of AZ31 magnesium alloys is investigated using a CO2 laser experimental system. The effect of three different filler wires on the joint properties is researched. The results show that the weld appearance can be effectively improved when using laser welding with filler wire. The microhardness and tensile strength of joints are almost the same us those of the base metal when ER AZ31 or ER AZ61 wire is adopted. However, when the filler wire of ER 5356 aluminum alloy is used, the mechanical properties of flints become worse. For ER AZ31 and ER AZ61 filler wires, the microstructure of weld zone slws small dendrite grains. In comparison, for ER 5356 filler wire, the weld shows a structure of snowy dendrites and many intermetallic compounds and eutectic phases distribute in the dendrites. These intermetallic constituents with low melting point increase the tendency of hot crack and result in fiagile joint properties. Therefore, ER AZ31 and ER AZ61 wire are more suitable filler material than ER 5356 for CO2 laser welding of AZ31 magnesium alloys.

Microstructure and property research on welded joints of 7xxx aluminum alloy welding wire TIG for 7075 aluminum alloy

7 xxx welding wire was self-made by spray forming ingots drawn to series welding wires products,and then TIG butt welding test is used for 5 mm thick 7075 high-strength aluminium alloy.After welding,the stress relief+solid-solution aging heat treatment(T6)were performed to joints,and the mechanical properties and microstructure of the joints before and after heat treatment were comparative analyzed.The results show that the properties of the heat-affected zone(HAZ)of the joint before heat treatment decreas,and the joint is softened.The welded joints tensile strength is 271.8 MPa,the elongation is 5.6%,and the average hardness of the weld is 118.4 HV.The second phase particles such asη(Mg Zn2),S(Al2 Cu Mg),Al13 Fe4 are distributed in a network layer,with no apparent element segregation.After heat treatment,the structure of each area of the joint is coarsened,and a small amount of Fe-containing impurity phases are distributed.Theηand S phases are dissolved in the matrix.The hardness of each area of the joint is increased to 155 HV,and the softening zone is disappeared,this leads the joint elongation close to 16.9%.The tensile strength is increased to 511.8 MPa,reaching 94%of the base metal tensile strength.

Joint performance in laser welding Al alloy with filler wire

CO2 laser welding aluminum alloy with filler wire was studied. The results indicate that the problems in CO2 laser welding of Al alloy, such as bad appearance of weld, easily excessive penetration and low strength, can be improved effectively by using laser welding with filler wire, and the maximum tensile strength of weld can reach 94% for the base metal. It also can be found that, the linear energy have great influence on the microstructure and mechanical properties of the joint. As the heat input increases, the cellular fir-tree crystals in the weld zone become sparse and the form of tensile fracture transforms from gliding fracture to brittle fracture.

FEM analysis of stress evolution in twin wire welding of Al alloy

Twin wire weld temperature results calculated by classical double ellipsoid heat source model are bigger than the experimental results. By analyzing the shape of twin wire welding arcs and the track of droplets transition, the phenomena that both the fore arc and rear arc of twin wire welding deflect to the middle of the two arcs is found. Based on this the double ellipsoid heat source model is amended, and a heat source model which can be applied to calculate the temperature field of twin wire welding was put forward. This model is testified by actual experiment of temperature sampling. Then, the evolution regularities of longitudinal and transverse stress for 2219 sheets were investigated under the condition of twin wire welding. The result shows that longitudinal residual stress value of twin wire welding is 10% higher than that of the single wire welding.

Microstructures of 2219 twin wire welded joints

With thick plates of 2219 high-strength alloy, the microstructures of welded joints with twin wire MIG welding were analyzed. Experimental results show that no hot crack was found in the weld due to discontinuous distribution of cocrystallization with low melting temperature, but porosity is serious in the first weld seam that is mainly composed of equiaxial grains with uneven sizes. As the poor position of the whole welded joint, fusion zone has big and coarse grains, uneven microstructures ; In quenching zone, there exist a lot of soaked microstructures that cocrystallizntion with low melting temperature solute into matrix, thus strengthening the metal in this zone; In excessive aging zone, much more phases that distribute evenly will be separated from the matrix; Ontside this zone, properties and microstructures of the metal are basically similar to matrix due to the relatively low temperature or unaffected heat in the zone during welding.

焊丝成分对2050铝锂合金焊接性能影响研究

采用十字搭接试验方法测定2050铝锂合金焊接裂纹敏感性,研究了焊丝成分变化对2050铝锂合金焊接结晶裂纹率、液化裂纹率的影响,并对焊接接头的组织形貌、断裂特征和力学性能等进行了测试和分析。研究结果表明:采用钨极氩弧焊匹配Al-Cu-Si-Ti-Sc-Ce-B系焊丝对2050铝锂合金进行焊接,获得的焊接接头结晶裂纹率K1和液化裂纹率K2均为0,其强度系数可达母材的70%。

铝合金焊丝送丝稳定性测试分析

【目的】旨在深入分析影响4043铝合金焊丝送丝稳定性的因素,为铝合金焊丝产品质量检测提供指导依据。【方法】选取市面上国内外常用的5种4043铝合金焊丝,提取焊接过程中的送丝阻力、送丝速度,以及焊丝表面质量和焊丝拉伸性能等关键参数,综合分析评价送丝性能。【结果】通过测试送丝阻力和焊接时送丝速度的波动情况,得出不同厂家的铝合金焊丝在焊接过程中送丝阻力值、送丝速度的波动幅度区别较大;通过对铝合金焊丝表面质量观察分析,可以发现焊丝表面的微观形貌状态是影响送丝稳定的主要因素,焊丝表面平整度高、表面划痕少可以有效保证送丝稳定性;通过对铝合金焊丝拉伸性能测试和微观拉伸断口扫描分析可知,焊丝内部气孔少且小可以保证焊丝的拉伸性能,同时提高铝合金焊丝送丝稳定性。【结论】通过提取焊接过程送丝阻力和焊接时送丝速度的标准方差,可以客观评价4043铝合金焊丝的送丝性能,并与实际情况相符合;焊丝表面平整度高、微观划痕少的焊丝送丝性能良好,因此,为提高4043铝合金焊丝送丝稳定性,必须严格控制焊丝拉拔或刮削工艺;焊丝内部缺陷少的焊丝送丝性能良好,因此,为提高4043铝合金焊丝送丝稳定性,必须严格控制焊丝冶炼工艺。

焊丝成分对5454-H32铝合金焊缝组织与性能的影响

以使用脉冲弧熔化极气体保护焊焊接的3.2 mm厚5454-H32铝合金对接接头为研究对象,使用光学显微镜、SEM、EDS和显微硬度计,分析2种接头的显微组织、析出相形态、分布和成分及显微硬度,测试接头的力学性能。分析结果表明,使用ER5356焊丝焊接的接头各项性能均优于使用ER4043焊丝焊接的接头性能。

镍基焊丝氩弧焊K438合金接头组织与性能研究

针对某型燃气轮机动力涡轮转子叶片磨损失效要求,通过钨极氩弧焊制备了无裂纹的K438接头,分析了K438接头的显微组织和力学性能。结果表明,接头成形美观、无裂纹,堆焊区组织中γ基固溶体上弥散分布着富Cr的柱状、颗粒状、树状等形态各异的M_(23)C_(6)和M_(6)C白色相,结合线硬度达452 HV0.5,堆焊区硬度约278 HV0.5,接头平均抗拉强度403.3 MPa,接头断裂于堆焊区,断裂形式为脆性和韧性混合断裂。

浅谈镁合金焊丝的成分、制备工艺及应用

文章重点介绍了镁合金焊丝的化学成分、制备工艺及应用,并对镁合金焊丝的研究提出了一些思考和展望。

镍铜合金FCAW-G堆焊工艺研究

采用药芯焊丝气体保护焊(FCAW-G)对Q345R钢试板进行了镍铜合金N04400堆焊工艺评定,依照NB/T47014—2011《承压设备焊接工艺评定》要求对堆焊层的弯曲、化学成分及金相组织进行了检测。试验结果表明:采用80%Ar+20%CO_(2)混合保护气体,选用型号为ENiCu7T0-4的药芯焊丝进行过渡层及耐蚀层的堆焊,可以获得性能优良的耐蚀层,其化学成分满足标准要求,为镍铜合金实现高效堆焊提供了一种新的工艺参考。

存放时间对铝合金焊丝熔敷金属及焊接性能的影响

针对已开封的铝合金焊丝,对其存放期限进行研究。分别选取存放时间为0、24 h、48 h、72 h、168 h、360 h的焊丝进行熔敷金属抗气孔性能试验和力学性能试验,并测试焊接接头疲劳性能,探究存放时间对铝合金焊丝性能的影响。研究结果表明:存放时间在0~360 h,熔敷金属的抗气孔性能均可以满足标准要求,熔敷金属的气孔数与存放时间呈线性递增关系,拟合度R 2因子达0.94;熔敷金属的力学性能均可以满足标准要求;随着存放时间的增加,熔敷金属的σb、σ0.2、断后延伸率A没有显现出特定的变化规律;随着存放时间的增加,焊接接头疲劳极限σ-1呈现出下降的趋势,存放时间0~24 h,焊接接头疲劳性能良好,承受动载荷能力较强;从实际应用的角度上讲,存放时间0~360 h的铝合金焊丝可以用于生产承受静载荷的构件,而对于承受动载荷的关键构件,焊接所用铝合金焊丝的存放时间不宜超过24 h。

Multi-scale study of ductility-dip cracking in nickel-based alloy dissimilar metal weld

A ductility-dip-cracking(DDC)-concentrated zone(DCZ) in a width of about 3 mm was observed adjacent to the AISI 316 L/52 Mw fusion boundary(FB) in 52 Mw. The morphology, microstructure, mechanical and thermal properties and corrosion behavior in simulated primary water of DDC/DCZ were investigated by scanning electron microscopy(SEM), transmission electron microscopy(TEM), 3 D X-ray tomography(XRT), 3 D atom probe(3 DAP), slow strain rate tensile(SSRT) testing and thermal dilatometry. The results indicate that DDCs are random-shaped and disc-like cavities with corrugated structure of inner surface and are parallel in groups along straight high-angle boundaries of columnar grains, ranging from micrometers to millimeters in size. Large-size M_(23)C_6 carbides dominate on the grain boundaries rather than MC(M=Nb, Ti), and thus the bonding effect of carbides is absent for the straight grain boundaries.The impurity segregation of O is confirmed for the inner surfaces of DDC. The oxide film formed on the inner surface of DDC(about 50 nm) is approximately twice as thick as that on the matrix(about 25 nm)in simulated primary water. The yield strength, tensile strength and elongation to fracture of 52 MwDCZ(400 MPa, 450 MPa and 20 %, respectively) are lower than those of 52 Mw-MZ(460 MPa, 550 MPa and 28 %, respectively). The intrinsic high-restraint weld structure, the additional stress/strain caused by the thermal expansion difference between AISI 316 L and 52 Mw as well as the detrimental carbide precipitation and the resulting grain boundary structure all add up to cause the occurrence of DCZ in the dissimilar metal weld.

Characteristics of Joint Welded by Laser Welding of Aluminium-Lithium Alloy with Filler Wire

The characteristics of weld shape,microstructure,mechanical properties and defects of 5A90 Al-Li alloy joint by laser welding (LBW) and laser welding with filler wire (LWFW) were studied and analyzed.The results indicated that the microstructure of joint by LWFW was fine-grained layer and the equiaxed grain in most of seams,which were similar to the joint by LBW.Compared with the joint by LBW,the microstructure of joint by LWFW tended to fine,and the range of the columnar crystals zone was prone to decrease.The Microhardness of the joint by LWFW (92.57HV0.2) was lower than that by LBW (95.65HV0.2),but the uniformity was better.The ultimate tensile strength of the joint by LWFW was lower than that by LBW slightly,which reached to 73.03% and 79.22% of the base metal respectively.However,the elongation of the LWFW joint was higher than that of the LBW joint significantly,which reached to 38.65% and 20.38% of the base metal respectively.The microstructure and mechanical properties of 5A90 Al-Li alloy by LWFW were better than that by LBW.The defects of joint were mainly forming defects which were caused by improper parameters and porosity inside the joint,which was caused by uncleaned surface and incomplete penetration.

热丝TIG堆焊Alloy 59镍基合金工艺及其堆焊层性能研究

采用ASTM A262.E法、ASTM G48A法、ASTM G36及NACE TM0177腐蚀试验和力学性能、金相等测试方法,对热丝TIG堆焊Alloy 59进行了焊接工艺的研究,对堆焊层各项性能进行了研究。研究表明,热丝TIG是堆焊Alloy 59镍基合金的有效方法,堆焊层平整度较好,未观察到金相组织粗大晶粒;堆焊层力学性能及硬度均符合相关要求,抗晶间腐蚀及点蚀能力好,显示出良好的耐饱和湿H 2S环境腐蚀能力,同时也满足在Cl-应力腐蚀环境中的使用。

Impulse Capacitor Discharge Welding of Hollow Structure Made of Nickel-Base Alloy

Future steam turbines will use hollow structures so that the turbine inlet temperature can be increased to improve the thermal efficiency. These hollow structures are made of the nickel-base alloy Nicrofer 6025 HT and consist of a wire mesh between two cover sheets. The cover sheets can be joined to the wire mesh by capacitor discharge welding due to its extremely short welding duration. The goal of this research is to investigate suitable welding parameters so that the weld spots form in an optimum way to increase the tensile shear strength and reduce spattering. Tensile shear tests, three-point bending tests, and micrographs were used to judge the joint quality of structures made with various welding parameters. The results show that the best welds are obtained with a transmission ratio of 1：200, welding energy of 70% to 95%, and electrode force of 7 to 9 MPa.

Microstructure and properties of Al-Mg-(Sc, Zr) welded joint

Mechanical properties and microstructure of Al-Mg-(Sc, Zr) welded joint prepared by manual labor melt inert gas(MIG) welding method using Al-Mg and Al-Mg-Sc weld wire as filling materials were studied comparatively. The results show that the apparent recrystallization does not happen in heat-affected zone. It proves that Al-Mg(Sc,Zr) alloy has a high capability of resistance to welding heat-soften. Using Al-Mg-Sc welding wire as filling material can obviously refine the grains of weld seam and improve its strength. The layer of small equal-axe grains in fusion area improves the joint strength between welded metal and base metal. The coefficients of welded joints when Al-Mg-Sc and Al-Mg welding wire are used as filling material are greater than 0. 90, respectively. The yield strength of welded joints with Al-Mg welding wire is only 187 MPa, one is as high as 287 MPa with A1-Mg-Sc welding wire, thus the working strength of the welded unit is greatly improved.