TA2钛合金焊接接头不同区域的疲劳裂纹扩展速率

对TA2钛合金焊接接头的母材区、熔合线、焊缝中心和热影响区的疲劳裂纹扩展速率、疲劳断口形貌以及显微组织进行了研究。结果表明:接头各区域的疲劳裂纹扩展速率相差不大,可直接用焊缝区的裂纹扩展速率表示;各区域试样的断口呈典型的疲劳断口形貌;母材区的平均晶粒尺寸约62.8μm,热影响区的约为110μm,晶粒尺寸对疲劳裂纹扩展速率没有明显影响。     

激光焊接对镀锌平板力学性能及拉伸断口影响研究

采用光纤激光对海工装备中的镀锌平板进行焊接,对镀锌平板焊接接头母材区、热影响区、焊缝区的微观硬度进行测量,研究了焊接试样的拉伸性能和断口形貌。结果表明,激光焊接接头的强度和硬度均高于母材。焊缝区接头组织获得了低碳马氏体,因而接头硬度不及热影响区高。     

激光焊接对镀锌平板力学性能及拉伸断口影响研究

采用光纤激光对海工装备中的镀锌平板进行焊接,对镀锌平板焊接接头母材区、热影响区、焊缝区的微观硬度进行测量,研究了焊接试样的拉伸性能和断口形貌。结果表明,激光焊接接头的强度和硬度均高于母材。焊缝区接头组织获得了低碳马氏体,因而接头硬度不及热影响区高。     

TRIP钢板电阻点焊接头的疲劳性能

分别对TRIP800钢板母材、点焊接头进行疲劳试验,获得了载荷与疲劳寿命曲线,并对其显微组织、硬度、疲劳寿命和疲劳断口形貌进行了研究。结果表明:点焊接头的熔核区组织为板条状马氏体,热影响区为马氏体、铁素体及高温回火贝氏体组织,与母材的有较大差异;熔核区和热影响区的硬度比母材的高;TRIP钢点焊接头缺口效应严重以及大量脆性马氏体组织的存在,使得点焊接头的疲劳寿命明显降低,只有母材的1/10左右;母材的疲劳源均位于试样外表面的缺陷处;而由于缺口应力集中作用,点焊接头的疲劳源位于缺口附近的微观缺陷处,夹杂物的存在仍然是裂纹萌生的主要原因;母材的疲劳扩展区表现为韧性断裂,点焊接头表现为脆性断裂,瞬断区都表现为脆性断裂。     

2.25Cr-1Mo钢回火脆化对氢脆的影响

用冲击试验和电化学充氢方法研究了长期服役的2．25Cr-1Mo钢的回火脆化和氢脆问题．并对试样进行了显微组织分析和断口电镜扫描。结果表明：回火脆化程度不高的母材对氢脆的影响较小，断口形貌为准解理和少量的沿晶断裂；回火脆化程度较严重的焊缝对氢脆的影响较大，断口形貌为沿晶断裂。对于母材．回火脆化与氢脆的关系为线性相加；对于焊缝，回火脆化大大加剧了氢脆的程度。     

DH32船板钢埋弧焊接头的力学性能

采用埋弧焊对DH32高强度船板钢进行了焊接,通过扫描电镜、拉伸和冲击试验机等测试了焊接接头的力学性能并分析了其冲击断口形貌。结果表明:该钢10道次埋弧焊焊接接头的拉伸断裂位置均在靠近热影响区的母材区,接头的抗拉强度与母材的相当,没有出现明显的软化现象;焊缝、熔合区、热影响区试样的平均冲击功分别为55,58,75J,均满足冲击功不小于34J的要求;随着距焊缝中心距离的增大,焊接接头冲击断口中的纤维区面积增大,接头基本不存在韧性最差区。     

X70和X80钢螺旋焊管母材的低温韧性

对X70和X80钢螺旋焊管母材的低温夏比冲击性能和落锤撕裂试验(DWTT)性能进行了对比研究。结果表明:两种钢管母材横向试样的低温韧性均比纵向试样的好,X70钢管母材的韧脆转变温度低于X80钢管母材的;当试验温度在-20℃以上时,两种母材的冲击断口剪切面积比都在95%左右,为韧性断裂,低于-20℃时,随温度的降低,两种母材夏比冲击功的下降幅度远大于剪切面积比的下降幅度;母材的低温韧性受试验方法的影响很大,DWTT测得的韧脆转变温度远高于夏比冲击试验的。     

TA15钛合金钨极氩弧焊焊接接头力学性能研究

TA15钛合金钨极氩弧焊焊缝、热影响区、母材的微观组织差别明显,晶粒尺寸依次减小.焊接件的疲劳试验结果分析表明,热影响区是焊接接头的薄弱部位,疲劳裂纹大多萌生于焊接热影响区区域.疲劳破坏试样断口的SEM(scanning electron microscope)分析表明疲劳裂纹大多起源于焊接热影响区的气孔处.     

动车铝合金搅拌摩擦焊接头疲劳性能的研究

分析了动车用6005A铝合金的搅拌摩擦焊接头的显微组织及疲劳性能。研究表明:接头表面有Al2O3生成,接头焊核区是细小的等轴晶,并有"洋葱环"形貌,热影响区晶粒粗大,接头的疲劳强度低于母材,但高于MIG焊,疲劳断口为韧窝与准解理的混合断口。     

激光焊接6156-T4铝合金对接与T型接头的性能对比

用拉伸试验机、疲劳试验机、扫描电镜等对激光焊接6156-T4铝合金对接接头和T型接头的拉伸性能、疲劳性能和断口形貌进行了对比研究。结果表明:对接接头的拉伸性能接近于母材的,T型接头的抗拉强度较母材的有一定程度的降低,对接接头的疲劳强度明显高于T型接头的;对接接头疲劳断口位于热影响区,T型接头的断口穿过热影响区和母材;两种接头疲劳裂纹均萌生于应力集中较为严重的焊趾部位,以近似半椭圆的形状沿厚度方向扩展直至接头断裂。     

铝合金双面双弧同步立焊工艺特征与接头组织性能分析

采用双面双弧同步立焊工艺方法,对8 mm厚5083铝合金进行自熔试验,I形坡口一次熔透,焊缝成形美观。通过调节两侧电弧热量配比研究熔池成形规律,并从焊接接头的微观组织、力学性能分析其连接机理。研究结果表明,随着热输入的增加,双面双弧同步立焊热量加速集聚,熔深以三次幂函数的速度增大。双面双弧同步立焊接头轮廓呈“双曲线形”,而相同热输入下的单面焊接头则呈“倒马鞍形”。总热输入一定的情况下,双面双弧接头正面熔宽随能量配比系数的增大而增大,反面熔宽随能量配比系数的增大而减小,中间熔宽基本不变,熔化面积随能量配比系数的增大先增大后减小;能量配比系数一定时,随着焊速的增大,接头熔宽和熔化面积均减小。母材组织为条带状纤维织构,热影响区发生静态回复与再结晶,变形组织消失,产生新晶粒,焊缝区主要由α-Al固溶体、β相(Al8Mg5)质点和骨骼状的Mg2Si析出相组成。焊缝的抗拉强度随着能量配比系数的增大而减小,拉伸断裂形式为韧性断裂。热影响区出现软化现象,双弧交汇区硬度低于正面焊缝区。     

Q690C粒状贝氏体钢MAG焊接头中M-A组元的演变及其对热影响区冲击韧度的影响

为了研究Q690C低碳粒状贝氏体钢热影响区M-A组元演变及其对各亚区韧性的影响,采用全自动熔化极活性气体保护焊(Metal active-gas welding, MAG)施焊并在接头各个区域开V型缺口进行冲击试验,分析各亚区韧性与各亚区组织、断口、M-A组元统计结果之间的对应关系。结果表明,焊缝为针状铁素体,断口上韧窝细小密集,呈韧性断裂,虽然M-A组元数量很多,且存在于晶界,但是由于尺寸小,大都为块状,所以对冲击韧度影响不大;熔合区与粗晶区均为上贝氏体,且M-A组元大多以长条状分布于上贝氏体板条束间;其中熔合区的冲击韧度最差,系粗大基体引发的解理断裂;其余各亚区韧性接近母材,无明显恶化,M-A组元多呈较小块状,存在于晶界。由上述结果可知,M-A的分布、尺寸与形态的演变受控于为领先相的基体组织;细小的贝氏体基体及针状铁素体基体可弥补M-A组元对韧性的危害;组织控制仍应以基体组织控制为重点。     

X80管线钢断裂韧性及失效评估图研究

X80管线钢在我国已经开始大规模的应用,其断裂韧性和失效评估曲线是工程应用中安全评定的重要依据。在力学性能测试的基础上,参考材料断裂韧性测试标准,并在试验中采用高K值比法预制疲劳裂纹,利用声发射装置确定裂纹起裂点,测定了X80管线钢母材、焊缝及热影响区的断裂韧性,并在此基础上建立其失效评估曲线,给出了符合三种材料特性的失效评估曲线拟合方程,以便为工程应用提供依据。     

焊后热处理对ASTM 4130钢焊接接头组织与性能的影响

通过金相观察、硬度和冲击试验,研究了不同保温时间的焊后热处理（PWHT）对ASTM 4130钢焊接接头显微组织、硬度、低温韧性的影响。结果表明,PWHT后,焊缝组织为铁素体、少量珠光体和碳化物,HAZ组织主要为回火索氏体、铁素体和贝氏体;造成熔合线附近硬度较高、韧性较低的原因是组织的粗化和上贝氏体的形成;随PWHT保温时间的延长,接头硬度降低,韧性改善。这主要是由于保温时间延长,使碳化物逐渐析出,其弥散强化效应和回火索氏体中合金元素固溶强化效应降低,同时,碳化物弥散度的降低也使得接头应力集中程度降低。     

Wear behaviour of a steel weld-joint

A series of experiments has been carried out to examine the dry sliding wear behaviour of the different regimes of a single pass steel weld-joint vis-à-vis their microstructures and micro-hardness characteristics. Wear tests have been performed on two types of specimen configurations: first, on limited regions of the weld-joint exhibiting a specific microstructure, and second, continuously from the weld metal to the base metal via the heat affected zone (HAZ). The former type of experiments was found capable in delineating the wear characteristics of the base metal, weld metal and the different regimes of the HAZ. The wear behaviour of the varied regimes of the weld-joint, specifically that of the different sub-zones of the HAZ, has been explained using their microstructures, initial micro-hardness, work hardening during wear and their inherent residual stresses. This is a first report on the sequential wear behaviour of a weld-joint.     

Some investigations on microstructure and mechanical properties of submerged arc welded HSLA steel joints

This paper investigates the influence of the submerged arc welding (SAW) process parameters (welding current and welding speed) on the microstructure, hardness, and toughness of HSLA steel weld joints. Attempts have also been made to analyze the results on the basis of the heat input. The SAW process was used for the welding of 16 mm thick HSLA steel plates. The weld joints were prepared using comparatively high heat input (3.0 to 6.3 KJ/mm) by varying welding current (500–700 A) and welding speed (200–300 mm/min). Results showed that the increase in heat input coarsens the grain structure both in the weld metal and heat affected zone (HAZ). The hardness has been found to vary from the weld centre line to base metal and peak hardness was found in the HAZ. The hardness of the weld metal was largely uniform. The hardness reduced with the increase in welding current and reduction in welding speed (increasing heat input) while the toughness showed mixed trend. The increase in welding current from 500 A to 600 A at a given welding speed (200 mm/min or 300 mm/min) increased toughness and further increase in welding current up to 700 A lowered the toughness. Scanning electron microscopy of the fractured surfaces of impact test specimen was carried out to study the fracture modes. Electron probe micro analysis (EPMA) was carried out to investigate the variation in wt.% of different elements in the weld metal and HAZ.     

油气管线钢焊接局部脆化及断裂机理的研究

采用焊接热模拟方法和现代物理测试技术研究了管线钢焊接热影响区的韧性变化规律。结果表明,多道焊中,当二次热循环峰值温度处于(α+γ)临界区时,管线钢HAZ的韧性最低,表现为临界粗晶区局部脆化。拉伸试验和冲击试验结果表明,管线钢临界粗晶热影响区在断裂过程中,存在夹杂物形核、铁素体与M—A组元界面形核和M—A组元内部形核三种方式。M—A组元对裂纹扩展没有阻止作用。     

16MnR钢焊接接头氢扩散三维有限元模拟

利用电化学渗透法测定氢在16MnR钢焊接接头处的焊缝金属、热影响区金属以及母材中的扩散系数。基于有限元软件ABAQUS,开发焊接接头在氢环境下的三维氢扩散耦合有限元计算程序,考虑焊接残余应力、不同组织对氢扩散的影响,得到氢浓度随时间的分布规律。计算结果表明,在焊缝和热影响区,由于氢聚集的浓度和焊接残余应力较大,这很容易使材料在应力作用下发生与氢有关的开裂。     

Domex700MC低合金高强钢药芯焊丝CO2气体保护焊焊接接头的组织与性能

用药芯焊丝CO2气体保护焊焊接Domex700MC低合金高强钢,用光学显微镜、硬度计和冲击试验机等对焊接接头的显微组织和力学性能进行了分析。结果表明：焊缝金属晶粒细小且分布均匀,有较多针状铁素体,但熔合区组织比较粗大,使熔合区附近塑性降低,为焊接接头的薄弱部位;焊缝金属显微硬度较高,为315HV,而在热影响区为225HV,出现软化现象;焊接接头力学性能优良,具有较高的抗拉强度（630．94MPa）和冲击功（135．34J）。     

A study of microstructures and mechanical properties of laser welded joint in GH3030 alloy

In this paper, we represent experimental laser welding of GH3030 alloy. The microstructure and mechanical properties of laser welded joints were investigated using an optical microscope, scanning electron microscope, energy diffraction spectrum and other methodologies. The results demonstrated that the weld primarily involved slender dendrites together with a small number of equiaxial crystals. The occurrence of porosities was mainly associated with the composition of the material itself. The cracks in the HAZ were induced by lowmelting- point eutectic phases that formed during laser welding. The segregation of the alloying elements in the matrix induced the variation of the performance within the joint. The average strength of welded joints was 646 MPa, 97.6 % of that of the base metal. Formation of inclusions and micropores in the fusion zone weakened the joint strength greatly.