微量合金元素对Si—Mn—Mo系焊缝显微组织和韧性的影响

在Si-Mn-Mo系60kg级结构钢焊条基础上,通过添加微量合金元素,研究微量元素对焊缝显微组织和低温韧性的影响.试验结果表明,当焊条药皮中联合添加适量Ti与B,并使焊缝中含有约0.021%[Ti]和0.004%[B]时,焊缝中的先共析铁素体(PF)和侧板条铁素体(FSP)几乎全部消失,而主要以均匀细小的针状铁素体(AF)存在.此时焊缝的低温韧性得到大幅度的提高,而且焊缝焊后经620℃×1h回火处理后的韧性降低甚微.     

提高60kg级结构钢焊条低温韧性的研究

采用微合金化方式，通过焊条药皮向焊缝过渡微量合金元素来提高Ｓｉ－Ｍｎ－Ｍｏ系６０ｋｇ级结构钢焊条焊缝金属低温韧性。试验结果表明：仅向焊缝过渡大约０．０２１％Ｔｉ时，焊缝韧性就较大的改善。     

稀土对低合金钢焊缝韧性的影响

在低合金钢焊条中,通过药皮过渡稀土合金,探讨其对低合金钥焊缝韧性的影响机制.结果表明:适量的稀土具有去氢、脱硫、减少夹杂、净化焊缝组织、细化晶粒的作用.并能抑制创板条铁素体的形成.因此,使低合金钢焊缝韧性得到明显提高.     

Ti-B多层焊缝及其热模拟试样冲击韧性的研究

本文采用热模拟试验机模拟了低碳低合金多层焊缝中的再热组织,证明多层焊缝低温冲击断裂的最薄弱环节就是热模拟焊缝再热区中韧性最低的区域,多层焊缝的韧性取决于焊缝再热区中韧性最低区域的韧性大小。线能量、合金元素之所以改变焊缝韧性是由于它们改变了焊缝再热区中韧性最低区域的韧性。     

Cr-Ni-Mo多层焊缝低温韧性的统计分析

本方采用示波冲击、俄歇分析、启裂源组织观察及热模拟实验,对Cr-Ni-Mo 70kg/mm~2手工多层焊缝中各种组织的形态及韧性进行了研究。其中韧性较低的是经850℃～1050℃再热后的重结晶及不完全重结晶组织,韧性最薄弱环节主要为具有黑色带状的重结晶组织,其构成为铁素体及带状分布的M-A组元或碳化物。薄弱环节数量越多韧性越低,整个焊缝的韧性越低;合金元素通过影响薄弱环节的韧性而影响整个焊缝的韧性。     

药皮组分对不锈钢焊条工艺性能的影响规律

焊条药皮成分对不锈钢焊条工艺性能有较大的影响。通过对近百种焊条的药皮组分进行调配，发现碳酸盐与氯化物的比值对稳弧性、焊接飞溅以及焊缝成型等性能的影响很大。TiO2与硅铝酸盐之比应不小于3．5：1，以防止出现粘渣。加入硅、钛等强脱氧剂会显著改善焊条的脱渣性能。药皮厚度对焊条工艺性能也有较大的影响。药皮厚度越大，焊接飞溅率越低，脱渣性能越好。     

药皮组分对不锈钢焊条工艺性能的影响规律

焊条药皮成分对不锈钢焊条工艺性能有较大的影响。通过对近百种焊条的药皮组分进行调配 ,发现碳酸盐与氟化物的比值对稳弧性、焊接飞溅以及焊缝成型等性能的影响很大。TiO2 与硅铝酸盐之比应不小于 3.5∶1,以防止出现粘渣。加入硅、钛等强脱氧剂会显著改善焊条的脱渣性能。药皮厚度对焊条工艺性能也有较大的影响。药皮厚度越大 ,焊接飞溅率越低 ,脱渣性能越好。     

新型J707Ni焊条的研制

本文根据焊缝扩散氢含量、氧含量及焊条工艺性能的测定结果,确定了以CaCO_3-CaF_2-TiO_2为基本渣系;又通过金相及断口分析、能谱分析和机械性能测定,研究了Cr,Ni,Mo对焊缝强度及韧性的影响及焊缝的低温断裂过程,其最佳含量范围如下:Ni为1.4％～1.6％,Cr为0.2％,Mo为0.3％～0.4％。在此基础上研制出一种新型J707Ni焊条,其各项性能基本达到国外同类焊条水平。     

多元微合金化铸铁电弧冷焊同质焊条的焊接性能

在生产条件下,研究了铝粉的加入量及焊接温度对多元微合金化铸铁电弧冷焊同质焊条所获得的焊补区组织和性能的影响。观察评估了焊条的焊接工艺性能,结果表明,在焊芯成分不变的情况下,药皮中配入４％的铝粉有助于焊缝金属石墨化,可使焊缝硬度降低的１０％,适当提高焊接温度（室温→２００℃）,焊缝中铁素体含量增加,熔合区渗碳体趋于消失,焊补区硬度显著降低,焊缝和熔合区最低硬度分别为ＨＢ１７６和ＨＢ１９７;熔敷金属抗强度高达４５３ＭＰａ,焊缝中无裂纹,焊条的焊接性能优良。     

低温镍基焊条焊接的LNG储罐用9Ni钢接头的力学性能

采用3种药皮成分不同焊条对LNG储罐用9Ni钢进行焊接,利用多元热动力学相图计算软件JMat Pro的Scheil模型配合镍基合金材料数据库对相应焊缝熔敷金属进行偏析计算,通过光学显微镜(OM)分析熔敷金属的组织,并利用IPP软件观测枝晶间距.此外,通过硬度、拉伸和低温冲击等试验评定熔敷金属的力学性能.结果表明,Nb为正偏析元素,3种焊条的熔敷金属组织均由奥氏体树枝晶和析出相组成.OK92.55型焊条的熔敷金属具有更小的枝晶宽度和枝晶间距,这是由于Nb元素的偏析作用,形成的碳化物有抑制枝晶长大的作用,这促使其熔敷金属具有更大的断后延伸率和断面收缩率,具有良好的塑性.3种焊缝在热影响区的硬度最大,这是因为焊接热循环的作用.3种焊条熔敷金属的拉伸断口形貌均为韧窝和解理两种断裂方式相结合的形貌,说明它们既有塑性断裂,还有脆性断裂,但OK92.55型焊条熔敷金属的韧窝占比更高,证明其拉伸塑性较好.3种焊条的熔敷金属的低温冲击断口均为韧窝形貌,OK92.55型焊条熔敷金属的韧窝更深更小,表现出更好的低温韧性.     

锰对C-Mn钢多层焊缝低温韧性影响的机理

本文通过热模拟、夏氏冲击及启裂源组织观察等实验,研究了锰对C-Mn钢多层焊缝韧性影响的机理。结果发现:启裂的最薄弱环节组织一般为原始柱状晶过热区(1350℃)、不完全重结晶区(860℃)及两者共同作用的再热区域;当锰含量较高时,细晶区也可成为薄弱环节,随着锰含量的升高,薄弱环节中针状铁素体的比例增大,该区的韧性升高,从而使整个焊缝的韧性升高;当锰含量为1.34％时,焊缝的韧性最佳。     

Effect of welding process on the microstructure and properties of dissimilar weld joints between low alloy steel and duplex stainless steel

To obtain high-quality dissimilar weld joints, the processes of metal inert gas (MIG) welding and tungsten inert gas (TIG) welding for duplex stainless steel (DSS) and low alloy steel were compared in this paper. The microstructure and corrosion morphology of dissimilar weld joints were observed by scanning electron microscopy (SEM); the chemical compositions in different zones were detected by energy-dispersive spectroscopy (EDS); the mechanical properties were measured by microhardness test, tensile test, and impact test; the corrosion behavior was evaluated by polarization curves. Obvious concentration gradients of Ni and Cr exist between the fusion boundary and the type II boundary, where the hardness is much higher. The impact toughness of weld metal by MIG welding is higher than that by TIG welding. The corrosion current density of TIG weld metal is higher than that of MIG weld metal in a 3.5wt% NaCl solution. Galvanic corrosion happens between low alloy steel and weld metal, revealing the weakness of low alloy steel in industrial service. The quality of joints produced by MIG welding is better than that by TIG welding in mechanical performance and corrosion resistance. MIG welding with the filler metal ER2009 is the suitable welding process for dissimilar metals jointing between UNS S31803 duplex stainless steel and low alloy steel in practical application.     

Microstructure and properties of the interlayer heat-affected zone in X80 pipeline girth welds

The heat-affected zone between the layers of a weld metal is a sensitive and important component of girth welds in X80 pipelines.However,only a few studies have focused on the interlayer heat-afected zone(IHAZ).In this work,thermal simulation was conducted to investigate the relationship between IHAZ microstructure and properties.Results showed that the toughness of the weld metal improved after a single welding thermal cycle but decreased after double welding thermal cycles,particularly when the weld metal was subjected to unaltered coarse grains of IHAZ.The relationship between the microstructure and properties of IHAZ was established to present the correlation of toughness with granular bainite content,grain size,and high-angle grain boundary content.     

Effects of welding wire composition and welding process on the weld metal toughness of submerged arc welded pipeline steel

The effects of alloying elements in welding wires and submerged arc welding process on the microstructures and low-temperature impact toughness of weld metals have been investigated. The results indicate that the optimal contents of alloying elements in welding wires can improve the low-temperature impact toughness of weld metals because the proeutectoid ferrite and bainite formations can be suppressed, and the fraction of acicular ferrite increases. However, the contents of alloying elements need to vary along with the welding heat input. With the increase in welding heat input, the contents of alloying elements in welding wires need to be increased accordingly. The microstructures mainly consisting of acicular ferrite can be obtained in weld metals after four-wire submerged arc welding using the wires with a low carbon content and appropriate contents of Mn, Mo, Ti-B, Cu, Ni, and RE, resulting in the high low-temperature impact toughness of weld metals.     

钛合金激光/氩弧斜焊缝疲劳性能对比研究

针对TC4钛合金激光、氩弧斜角度焊接疲劳性能展幵对比试验研究。对两种斜焊缝试样的疲劳寿命和疲劳断口进行了対比计算与分析。结果表明:氩弧斜焊试件的疲劳寿命相比激光斜焊的分散性小,激光斜焊试件的中值疲劳寿命是氩弧斜焊的1.96倍;激光焊缝比氩弧焊总体面积小,激光斜焊疲劳裂纹起始于热影响区表面,氩弧斜焊疲劳源位于试件内部气孔缺陷处。裂纹扩展初期两种焊缝均有脆性解理特征矿展后期和瞬断区激光斜焊比氩弧斜焊表现出更好的韧性。     

Fe-6.5% Si合金热轧板焊接接头的组织和力学性能

针对Fe-6.5% Si合金热轧板焊接接头易萌生裂纹的问题,研究了不同氩弧焊工艺对焊接接头显微组织和力学性能的影响规律.研究表明:不使用填充焊丝的TIG焊不适合Fe-6.5% Si合金热轧板焊接,因在焊缝内出现大量显微裂纹;使用工业纯铁焊丝的MIG焊实现了Fe-6.5% Si合金热轧板的良好连接,焊缝表面连续、鱼鳞纹均匀,焊缝内无显微裂纹.稀释硅浓度是改善焊缝区组织和力性的有效方法.优化工艺下的焊接接头在500℃拉伸延伸率5.5%,抗拉强度280 MPa,满足Fe-6.5%Si合金板带制造过程中的温轧工艺要求.     

喷焊层对焊缝组织性能的影响规律

为解决油田管线焊接接头防护问题 ,利用金相显微镜对焊缝组织形貌进行了观察。得到了镍基喷焊层元素熔入量对奥氏体焊缝显微组织及裂纹敏感性的影响规律。结果表明 ,镍基合金喷焊层的合金元素对奥氏体焊缝显微组织有明显影响 ,随着喷焊层元素熔入量的增加 ,焊缝柱状晶变得粗大 ,且方向性变得更明显。在一定范围内 ,增加喷焊层元素熔入量 ,焊缝的热裂纹敏感性将增大 ,但当熔入量再继续增加时 ,由于过量的喷焊层形成的大量低熔共晶物对焊缝冷却过程中的微裂纹起到了“愈合作用” ,使焊缝裂纹敏感性有所降低。同时 ,熔入过量喷焊层元素使得焊缝的薄弱位置发生了变化 ,热裂纹产生的位置由等轴晶区转移到柱状晶区。为了降低焊缝的热裂纹敏感性 ,应该在保证喷焊层耐蚀性的前提下 ,尽量降低喷焊层的厚度     

摩擦焊接头组织与力学性能

研究了变形速率对低合金结构钢摩擦焊接头组织与力学性能的影响，结果表明，增大变形速率和延长减速改善了接头区域的硬度分布，焊缝区宽度变窄，热影响软化区不明显，焊缝晶粒细化，使焊缝的韧性得到一定程度的改善，本文对接头各个区域的显微组织进行了分析。     

添加或未添加 Cu?Nb 的超低碳高强度钢焊接金属的显微组织和力学性能

Two types of ultralow carbon steel weld metals (with and without added Cu?Nb) were prepared using gas metal arc welding (GMAW) to investigate the correlation between the microstructure and mechanical properties of weld metals. The results of microstructure characterization showed that the weld metal without Cu?Nb was mainly composed of acicular ferrite (AF), lath bainite (LB), and granular bainite (GB). In contrast, adding Cu?Nb to the weld metal caused an evident transformation of martensite and grain coarsening. Both weld metals had a high tensile strength (more than 950 MPa) and more than 17% elongation; however, their values of toughness deviated greatly, with a difference of approximately 40 J at ?50°C. Analysis of the morphologies of the fracture surfaces and secondary cracks further revealed the correlation between the microstructure and mechanical properties. The effects of adding Cu and Nb on the microstructure and mechanical properties of the weld metal are discussed; the indication is that adding Cu?Nb increases the hardenability and grain size of the weld metal and thus deteriorates the toughness.