激光快速成形TA15钛合金氩弧焊接头组织及力学性能

对激光快速成形TA15钛合金与轧制TA15钛合金薄板进行了氩弧焊接试验,观察分析了焊接接头各区域组织特征,测试了焊接接头各区域的显微硬度以及室温拉伸性能.结果表明,激光快速成形件与轧制薄板氩弧焊焊缝凝固组织是具有粗大片状α+β组织特征外延定向生长的柱状晶.轧制件对焊接热影响敏感性强,热影响区晶粒发生严重长大现象,激光成形件靠近焊缝热影响区晶粒转变为等轴晶,距焊缝较远的热影响区仍保持柱状晶.激光成形件热影响区硬度最高,焊缝区及轧制件热影响区的硬度最低.焊接接头抗拉强度低于母材,塑性与轧制件相当,断裂位置位于轧制件热影响区.     

PM-TZM钼合金电子束焊接特性

为研究PM-TZM钼合金电子束焊接特性,对其进行了电子束焊接试验,分别对接头显微组织及力学性能进行了分析. 结果表明,PM-TZM钼合金电子束焊缝呈“钉状”几何特征,熔合线附近有链状气孔出现. 焊缝区由粗大的等轴晶及柱状晶组成,热影响区晶粒相比于母材明显长大. 接头各区域硬度值不同,焊缝区硬度与母材相当,硬度最低值出现在两侧热影响区.PM-TZM合金电子束焊接接头有较大的性能损失. 接头室温最高抗拉强度378 MPa,为母材抗拉强度的47%,1 000℃抗拉强度168 MPa. 接头拉伸断裂均发生于焊缝区,呈典型的脆性解理断裂特征.     

Mechanical and corrosion properties of 445J2 ultra pure ferritic stainless steel joint

The microstructure, mechanical and corrosion resistance properties of 445J2 ultra pure ferritic stainless steel thin plate joints conducted by the pulsed current gas tungsten arc welding (PCGTAW) were discussed in this paper. In order to avoid weld defects, the appropriate welding process was adjusted. The joints were subjected to optical microscopy, transverse static tensile, plastic deformation, intergranular corrosion and electrochemistry corrosion tests. The results indicated that the weld zone (WZ) is characterized with columnar grains and equiaxed grains and the heat-affected zone (HAZ) shows coarse ferrite grains due to the rapid solidification of thin plate welding. The PCGTAW joint exhibited acceptable mechanical properties and equivalent corrosion resistance properties as the base metal.     

旋转电弧横向GMAW接头组织及成形特点

旋转电弧横向GMAW可以很好地控制横向焊接时熔池下塌.由于旋转电弧的引入,在相同焊缝长度以及速度下,焊丝运动的轨迹增加,这样就会降低焊接热输入,从而降低焊缝下塌的趋势;另一方面,由于电弧的旋转,使得原本只作用在坡口中心的电弧力分散在坡口内的各个区域,使得电弧力可以抵消上坡口附近熔池金属的重力,抑制其下塌.文中对旋转电弧横向GMAW接头组织及成形进行了研究,发现了由于电弧旋转所产生的接头成形不对称这一特点,并对其产生的原因及机理进行了阐述和分析.     

Microstructure and alloy element distribution of dissimilar joint 316L and EH36 in laser welding

Microstructure and alloy element distribution of dissimilar joint 316L and EH36 in laser welding were researched, especially the influence of misalignment on weld profile and alloy element distribution. Weld zone (WZ) consisted of austensite and ferrite (F), and heat affected zone (HAZ) of EH36 side consisted of martensite, F, pearlite and carbide precipitation. Positive misalignment increased both upper and bottom widths (BWs), while negative misalignment made BW wider and upper width narrower. HAZ in steel EH36 side was clear and was narrowed and homogenised by negative misalignment. Alloy element contents of Cr and Ni in WZ was much more in negative misalignment. The interface transition gradient of alloy element between 316L and WZ was sharpened in the +0.8?mm misalignment, but diminished in the ?0.8?mm misalignment. The influence of misalignment on alloy element distributions can be attributed to the effect of gravity on transient flow of weld pool.     

Lap joining of titanium alloy using laser welding and resistance seam welding combined process

Titanium alloy lap joints were performed by combined laser welding and resistance seam welding process. The welding characteristics of this combined process were investigated compared with that of laser welding. The experimental results indicate that the combined process welded joint has larger weld width at the lap surface. The joint tensile shear force of combined process is 2.5 times that of laser welding. There are some pores around the lap surface in laser welded joint, and most pores can be eliminated by resistance seam welding process. Metallographic examinations of combined process welded joint reveal that the microstructure in heat-affected zone (HAZ) and weld zone has the acicular martensite morphology, which causes that the microhardness in HAZ and weld zone increases compared with the base metal, and the microhardness in weld zone is highest.     

Prediction of HAZ grain size in welding of ultra fine grained steel with different parameters

The temperature field and thermal cycling curve in the heat-affected zone during welding 400 MPa ultra fine grained steel by plasma arc were simulated using finite element method.The principle of grain growth kinetics was used to predict the grain size in the heat-affected zone under different welding parameters.The simulation results show that the growing tendency of HAZ grain could be controlled by adjusting the welding parameters,but the growth of HAZ grain could not be eliminated at all.The HAZ grain size became small with increasing of the cooling rate and added with increasing of welding current,arc voltage and welding speed.     

Impact property analysis of weld metal and heat-affected zone for low-alloy carbon steel multi-pass welded joint

Welded joint impact performances of low-alloy carbon steel plates welded by full-automatic gas metal arc welding (GMAW) were evaluated. To clarity the effect of impact temperature on impact properties of weld metal (WM) and heat-affected zone (HAZ), Charpy V impact tests at different temperatures and fracture surface analysis were carried out. The Charpy V impact energy decreases with the decreasing test temperature both for the WM and HAZ, while the proportion of crystal zone on WM and HAZ impact fracture surface increases with the decreasing test temperature. Research results indicate that the welding defects (void and slag) make the impact energy of WM more scattered and lower than that of HAZ.     

Microstructure and mechanical properties of the joint of 6061 aluminum alloy by plasma-MIG hybrid welding

Plasma-MIG (metal inert gas arc welding) hybrid welding of 6061 aluminum alloy with 6 mm thickness using ER5356 welding wire was carried out.The microstructures and mechanical properties of the welded joint were investigated by optical microscopy,X-ray diffraction (XRD),energy dispersive spectroscopy (EDS),tensile test,hardness test and scanning electron microscope (SEM) were used to judge the type of tensile fracture.The results showed that the tensile strength of welded joint was 142 MPa which was 53.6％ of the strength of the base metal.The welding seam zone was characterized by dendritic structure.In the fusion zone,the columnar grains existed at one side of the welding seam.The fibrous organization was found in the base metal,and also in the heat affected zone (HAZ) where the recrystallization occurred.The HAZ was the weakest position of the welded joint due to the coarsening of Mg2Si phase.The type of tensile fracture was ductile fracture.     

Metallographic structure analysis of DC pulsed SAW joint

Submerged arc welding （SAW） has shortcoming of over heat input, which increases grain size in heat-affected zone （ HAZ） and decreases welding quality and mechanical properties of the joints serioasly. With improvements of welding equipment, direct current （ DC） pulsed SAW （ PSAW） was utilized successfully in the research. Comparing DC PSAW with DC common SAW （ CSAW） , the metallographic structure was analyzed with optical and electron microscope, the width of HAZ was measured as well as the width and hardness of the coarse grained HAZ （CGHAZ）. The research shows that DC PSAW joint had higher welding penetration, narrower HAZ and CGHAZ, which benefited HAZ performance and welding quality.     

Study on weld formation in a novel rotating arc horizontal GMAW

A novel rotating arc horizontal welding process was developed for solving the sagging of the molten pool which bottlenecks the application and the development of the horizontal welding. The principle of the effect of the rotating arc on the molten pool is that the rotating arc process not only can reduce the welding heat input by prolonging the welding path in the same welding distance caused by the arc rotation, but also disperse the arc force to affect the sidewall periodically to support the molten metal near the upper sidewall. The effects of the rotating speed and arc voltage on the weld formation were studied.The results indicate that there is an appropriate range of the rotating speed and the arc voltage to obtain the defect free horizontal welding.     

Application of rotating arc system to horizontal narrow gap welding

Abstract

A rotating arc system for narrow gap horizontal welding was developed for solving the problem that the molten pool sagged due to the gravity. The characteristic of the system was that the synchronous rotation of nozzle and wire was generated by eccentric sleeve driven by motor. This process not only may reduce welding effective heat input due to an increase in the welding instantaneous velocity but also may disperse arc force which could counteract the gravity of upper side of molten metal. Both the two aspects were beneficial for horizontal weld formation. Experimental results indicated that shapely horizontal joint could be obtained in appropriate rotating parameters. The asymmetry of joint formation indicated that the heat affected zone width and microstructure in upper side were larger than that in lower side. The effective heat input difference near each side caused by the instantaneous velocity difference was the main reason why the formation characteristics occurred.     

TiZrNiCuBe块体非晶合金激光焊接行为及温度场数值模拟研究

采用数值模拟研究了Ti40Zr25Ni3Cu12Be20块体非晶合金激光焊接过程中的温度场变化和冷却速度变化规律,分析了Ti基非晶合金在激光焊接过程中保持非晶态结构的机理。以高斯表面热源和圆柱体热源相结合的复合热源模型作为焊接热源,考察了不同焊接参数下Ti Zr Ni Cu Be非晶合金在激光焊接过程中的热历史,结合实验结果分别对接头焊缝区和热影响区显微组织变化进行了分析,分别从加热和冷却两阶段给出非晶合金激光焊接接头非晶相得以保持的理论解释。完全非晶态接头的显微硬度测试表明:热影响区体现出较母材以及焊缝区更高的显微硬度,从玻璃转变温度、冷却速度以及屈服强度三者之间关系的角度对该现象进行理论分析,并通过实验验证分析的准确性。     

大热输入焊接EH36船板钢接头力学性能

以EH36高强度船板钢为研究对象,通过拉伸和冲击分析试验手段,对EH36船板钢不同热输入埋弧焊接头进行了力学性能测试,同时采用扫描电镜对冲击试样断口形貌进行分析.结果表明,所有断裂均发生在拉伸试样的母材区,EH36船板钢在大焊接热输入条件下,焊缝和焊接热影响区的强度好于母材,并没有出现热影响区软化现象;随着焊接热输入增加焊缝的冲击韧性降低,从焊缝和熔合区断口形貌来看,断裂类型为韧性断裂和准解理断裂的混合断裂.随着远离熔合线距离的增加,冲击吸收功有增加的趋势,在距离熔合线4 mm处的冲击吸收功跟母材接近,说明该位置处韧性基本不受焊接热循环的影响.     

Double-sided gas tungsten arc welding process on TC4 titanium alloy

TC4 titanium alloy was welded by double-sided gas tungsten arc welding（GTAW） process in comparison with conventional GTAW process, the microstructure and mechanical performance of weld were also studied. The results indicate that double-sided GTAW is superior over regular single-sided GTAW on the aspects of increasing penetration, reducing welding deformation and improving welding efficiency. Good weld joint was obtained, which can reach 96.14% tensile strength and 70.85% elongation percentage of the base metal. The grains in heat-affected zone（HAZ） are thin and equiaxed and the degree of grain coarsening increases as one moves to the weld center line, and the interior of grains are α and α′ structures. The coarse columned and equiaxed grains, which interlace martensitic structures α′ and acicular α structures, are observed in weld zone. The fracture mode is ductile fracture.     

等离子弧焊Q345B和430不锈钢异种接头的微观组织与性能

摘要： 采用等离子弧焊对3 mm厚的Q345低合金钢与430不锈钢进行异种钢焊接,并对接头微观组织、力学性能及耐腐蚀性能进行了研究。结果表明,当转弧电流为100 A时,等离子弧焊Q345B/430异种钢接头的焊缝组织为均匀分布的马氏体及针状铁素体,焊接接头综合性能优良。随着电流的增大,焊缝组织转变为粗大板条马氏体及铁素体。两侧热影响区组织均发生一定程度的粗化,且Q345B侧热影响区出现魏氏组织。焊接接头于焊缝处显微硬度最大,不同转弧电流条件下异种钢显微硬度分布趋势大致相同。不同转弧电流下,焊接接头抗拉强度均与430不锈钢相近,且均断裂在靠近焊缝的430母材侧,转弧电流为100 A时接头抗拉强度最大值427 MPa。焊接接头的耐腐蚀性能与焊接电流呈负相关趋势。 创新点： 试验结果为铁素体低合金钢与铁素体不锈钢异种钢接头的应用提供了工艺数据与支撑。     

TC17钛合金线性摩擦焊接头组织及性能

文中针对航空发动机风扇及压气机盘TC17钛合金材料,开展了接头组织分析、拉伸性能测试及硬度测试,分析了接头不同部位组织特征及形成原因.结果表明,接头明显分为母材区（BM）、热力影响区（TMAZ）和焊合区（WZ）,焊接接头中部热力影响区的组织表现为等轴晶粒,而靠近焊缝边缘处热力影响区的晶粒表现为沿着受力方向被拉长,焊合区发生了动态再结晶;接头的拉伸性能与母材相当;接头热力影响区的硬度高于母材和焊合区,平均硬度为486 HV.     

DH36钢水下摩擦塞焊工艺及力学性能

文中通过工艺试验研究了DH36钢水下摩擦塞焊工艺窗口及焊接接头的显微组织和力学性能。结果表明,在焊接转速较低时,焊接接头根部容易形成“未结合”焊接缺陷,提高焊接转速可有效避免缺陷的形成;焊接转速为7500r/min、轴向压力在30~45kN范围是较适宜的焊接工艺参数;焊接接头焊缝组织主要为板条马氏体和贝氏体,焊接热影响区的组织主要为贝氏体;焊接接头的拉伸性能和冲击性能均随焊接转速的提高有不同程度升高,但随轴向压力的变化不具有明显规律性;在较优的焊接工艺参数下（焊接转速7500r/min、轴向压力40kN）焊接接头屈服强度为370MPa,抗拉强度为530MPa,断后伸长率为22.5%,结合线处0℃冲击吸收功为42.5J。     

Significant system parameters influencing HAZ properties in 9%Ni steel

Abstract

The relative influence of welding system parameters on the properties of the heat affected zone (HAZ) in 9%Ni steel has been investigated via a fractional factorial experiment. The HAZ properties evaluated were the dimensions in two locations, the hardness, and the impact strength. The independent variables were bevel preparation method, welding process, heat input, plate thickness, joint design, and position of the weldment. The study indicated that heat input, bevel preparation method, and an aliased interaction between the bevel preparation method and the joint design must be controlled to minimise the extent of the HAZ at the plate surface. The width of the HAZ measured at plate mid-thickness is a function of plate thickness, heat input, and two aliased interactions: between welding process and joint design; and that determined for the surface HAZ (interaction between joint design and bevel preparation method). Hardness was significantly affected by thickness, welding process, position, and heat input as well as by an aliased interaction between thickness and joint design. Impact strength was most influenced by two aliased interactions, both including the bevel preparation method. Weld position was found to affect HAZ impact values significantly.     

Effect of rotating arc process on molten pool control in horizontal welding

This paper describes the effect of rotating arc process on molten pool control in narrow gap horizontal welding. From energy strategy and force strategy, technical advantages of rotating arc process in molten pool control are explored. On the one hand, because of the decrease of temperature and holding time in weld centre, rotating arc process limits the tendency of molten pool sagging with the arc rotating frequency no more than 10 Hz, which is indicated from the simulation results of heat distribution characteristics. On the other hand, rotating arc process induces the flow of molten metal in the weld width direction by the periodical effect of arc force and droplets impingement, which is observed by the high speed photography system. This oscillation propels the molten metal at lower side against the effect of gravity to flow to the upper side, which is beneficial for the molten pool formation of horizontal welding.