焊接电流对35CrMoA+S275NL异种钢焊接接头显微组织和硬度的影响

采用自动TIG焊,选用不同的焊接电流,对35CrMoA+ S275NL异种钢进行焊接.分析了焊缝和热影响区金属的显微组织;并测试了焊接接头的显微硬度.结果表明,焊接电流对热影响区的显微组织影响较小,但对焊缝金属中碳化物的大小及分布状态有较大影响;焊接电流为100A时,焊缝金属中的碳化物细小且分布均匀,其显微硬度分布也比较合理,更适合在低温条件下工作且存在交变载荷作用的零部件焊接.     

高强钢激光搭接焊接接头组织及显微硬度

采用光纤激光器对汽车工业中常用的双相钢HC450/780DPD+Z和低合金高强钢HC420LA进行激光搭接焊试验,探索焊缝附近微观组织和显微硬度转变,并研究不同焊接速度对焊缝显微硬度的影响。结果表明,焊缝附近微观组织主要包括熔化区、热影响区和母材三部分。焊接速度一定时,从母材到焊缝,HC420LA的显微硬度变化趋势为先增加后保持不变,HC450/780DPD+Z的显微硬度变化趋势为先增加后减小再保持不变。而随着焊接速度的增加,HC420LA焊缝显微硬度先增加后保持不变,HC450/780DPD+Z焊缝显微硬度先增加后减小。     

不同焊丝对35CrMoA+S275NL异种钢焊接接头显微组织和硬度的影响

分别选用TGS-2CM焊丝和ER309L焊丝,采用自动TIG焊对35CrMoA+S275NL异种钢进行焊接,分析了焊缝和热影响区金属的显微组织,并测试了焊接接头的显微硬度。结果表明,两种焊丝对异种金属35CrMoA+S275NL焊接均能获得良好的焊接接头,但用ER309L焊丝焊接所得焊缝金属的组织与性能更适合在低温条件下且存在交变载荷作用的焊接零部件。     

异种奥氏体钢焊接接头显微组织结构分析

研究了高锰奥氏体钢焊接接头性能和显微组织结构,在熔合线上不同合金元素成线性过渡,其显微组织与母材和焊缝组织相同,均为奥氏体加铁素体,显微硬度分析也证实了这点。说明用Ｎｉ－Ｃｒ奥氏体钢焊接材料焊接高锰奥氏体钢,可获得性能优良的焊接接头。     

焊接工艺对TP304/SS400异种钢焊接接头组织和性能的影响

利用扫描电子显微镜并通过常温拉伸弯曲、低温冲击以及显微硬度等试验研究了FCAW,SMAW和GTAW三种不同的焊接工艺对TP304/SS400异种钢焊接接头组织和性能的影响. 结果表明,三种焊接工艺条件下,焊缝金相组织都为δ铁素体+奥氏体,但δ铁素体含量及形态分布有明显差异;FCAW焊缝中蠕虫状δ铁素体和GTAW焊缝中针状δ铁素体可有效提高韧性,故冲击韧性较高,SMAW焊缝中骨骼状δ铁素体对韧性不利,冲击韧性最低,且随冲击吸收能量的降低断口由韧性断裂转变为脆性断裂;三种焊接工艺条件下,焊接接头综合力学性能表现良好,整体显微硬度值变化不大.     

中温回火对异种高强钢薄板激光拼焊接头组织性能的影响

本文利用激光焊工艺对B340L-B1500HS异种高强度钢进行了不等厚薄板焊接,研究了中温回火对接头组织性能的影响。试验结果表明,B340LA一侧的热影响区经过回火处理后,板条状马氏体组织消失并转变为铁素体组织：B1500HS％热影响经回火处理后原有粗大组织得到细化,转变为更加细小的铁素体组织。回火后焊缝中马氏体组织转变为回火托氏体组织,而针状马氏体和魏氏体组织消失,接头的硬度显著下降,焊缝附近硬度过渡更加平缓,有利于焊缝韧性的提高。     

35CrMoA+S275NL异种钢焊接工艺研究

在不同的焊接工艺条件下,用自动TIG焊对35CrMoA+S275NL异种钢进行了焊接.通过焊接接头试样,分析了焊缝和热影响区金属的显微组织,并测试了焊接接头的显微硬度.结果表明,在不同的焊接工艺条件下,均能获得冶金结合良好的焊接接头,当焊接电流为100A、焊前进行150℃预热时,获得焊缝金属的组织更细小,非金属夹杂物和...     

X80/X100异种钢激光-MIG复合焊接头显微组织和性能

采用激光-MIG复合焊对X80管线钢和X100管线钢进行焊接,研究了激光功率对复合焊接头的焊缝形貌、显微组织、硬度、强度和韧性的影响规律.结果表明,激光功率从2.0 k W增大至3.5 k W时,盖面焊缝熔宽和熔深增加,激光区熔深明显增加;激光区焊缝中AF含量增加、LB含量减少,X100侧粗晶热影响区和细晶热影响区中条状贝氏体含量减少,X80侧粗晶热影响区和细晶热影响区中准多边形铁素体含量增加.复合焊接头硬度分布并不对称,最高硬度出现在X100侧熔合区部位.复合焊接头的抗拉强度基本不随激光功率变化,拉伸试样断裂位置均为X80侧母材.随着激光功率增大,焊接接头最高硬度和韧性均下降.     

254SMO/Q235B异种钢焊接接头显微组织

分别选用ERNiCrMo-2,ERNiCrMo-3,ERNiCrMo-10,ERNiCrMo-12,ERNiCrMo-13及ERNiCrMo-14 6种镍基合金焊丝,采用手工TIG焊对254SMO/Q235B异种钢板进行焊接试验解决254SMO波纹管与Q235B钢管焊接时出现的裂纹问题,.焊后利用光学显微镜、X射线衍射仪、扫描电子显微镜和能谱仪对焊接接头进行了分析研究.发现采用ERNiCrMo-2,ERNiCrMo-3和ERNiCrMo-14焊丝时,焊缝中有较多的微裂纹出现;选用另外3种焊丝进行焊接时,焊缝成形良好,未出现焊接裂纹.结果表明,该焊接裂纹为热裂纹,异种钢物理性能的差异及焊缝中杂质元素的偏析是造成焊接裂纹的关键因素.     

T22/TP310H异种钢焊接接头的显微组织分析

采用手工钨极氩弧焊,选用ERNiCr-3镍基焊丝,对T22/TP310H异种钢进行焊接。焊后利用光学显微镜、扫描电镜、X射线衍射仪及能谱仪对焊接接头进行了分析研究。结果表明:焊缝组织主要为胞状树枝晶,焊缝金属的组成相主要有奥氏体基体γ相、NbC和M23C6碳化物相。T22侧热影响区有任意分布的块状铁素体,也有呈条状聚合物的块状铁素体;TP310H侧HAZ中奥氏体晶粒粗化现象不明显。     

Microstructure and deformation behaviour of laser welded dissimilar dual phase steel joints

The microstructure, microhardness, tensile properties, deformation and fracture behaviour of the Nd:YAG laser welded dissimilar joints between 780 and 980?MPa dual phase steels over a wide strain rate range were investigated. The welded joint shows hardening in fusion zone, supercritical and intercritical heat affected zones and softening in subcritical heat affected zones. For the dissimilar welded joint, the changing trend of the ductility is similar to those of the base metals with respect to the strain rate. The reason for the strain rate sensitivity of the failure location of the welded joint is that the major factor influencing the failure location changes from the content of ferrite to the content of ferrite/martensite interface with increasing strain rate.     

Microstructure and mechanical properties of laser welded dissimilar DP600/DP980 dual-phase steel joints

The use of dual phase (DP) steels in the automobile industry unavoidably involves welding and dynamic loading. The aim of this investigation was to evaluate the microstructural change and mechanical properties of laser welded dissimilar DP600/DP980 steel joints. The dissimilar joints showed a significant microstructural change from nearly full martensite in the fusion zone (FZ) to the unchanged ferrite-martensite dual-phase microstructure in the base metal. The welding resulted in a significant hardness increase in the FZ but the formation of a soft zone in the heat-affected zone (HAZ). The dissimilar welded joints were observed to exhibit a distinctive unsymmetrical hardness profile, yield-point-like phenomenon, and single-stage work hardening characteristic, with yield strength and work hardening rate lying in-between those of DP600 and DP980 base metals, and ultimate tensile strength equivalent to that of DP600 base metal. Although the welded joints showed a lower fatigue limit than the base metals, the fatigue life of the welded joints at higher stress amplitudes was almost the same as that of the DP600 base metal. The welded joints failed in the soft zone at the DP600 side under tensile loading and fatigue loading at the higher stress amplitudes. Fatigue crack initiation occurred from the specimen surface and crack propagation was characterized by typical fatigue striation together with secondary cracks.     

激光焊接异种钢接头微观结构及耐蚀性

对TRIP590钢和DP590钢拼焊板的接头区域进行了微观组织以及成分分析,并利用电化学方法测试了焊接接头各区域的塔菲尔曲线,研究接头各区域之间的组织、成分与腐蚀行为之间的关系。结果表明,焊缝区组织较均匀,两侧热影响区组织差别较大;Si和Mn在焊缝有一定的聚集;焊缝区的电极电位比两侧母材的都低,腐蚀电流密度相差不大,说明焊缝区耐蚀性低于母材;由于焊接热循环导致显微组织变化,焊缝区显微硬度明显比两侧母材高。     

Investigation into properties of laser welded similar and dissimilar steel joints

Abstract

Laser beam welding is currently used in the welding of steels, aluminium alloys, thin sheets, and dissimilar materials. This high power density welding process has unique advantages of cost effectiveness, deep penetration, narrow bead and heat affected zone (HAZ) widths, and low distortion compared to other conventional welding processes. However, the metallurgical and mechanical properties of laser welds and the response of conventional materials to this new process are not yet fully established. The welding process may lead to drastic changes in the microstructure with accompanying effects on the mechanical properties and, hence, on the performance of the joint. The thermal cycles associated with laser beam welding are generally much faster than those involved in the conventional arc welding processes. This leads to the formation of a rather small weld zone that exhibits locally a high hardness in the case of C–Mn structural steels owing to the formation of martensite. It is currently difficult to determine the tensile properties (full stress–strain curves) of the laser welded joint area owing to the small size(～V 2·3 mm) of the fusion zone. Complete information on the tensile and fracture toughness properties of the fusion zone is essential for prequalification and complete understanding of the joint performance in service, as well as for conducting a defect assessment procedure on such welded joints. Therefore, an experimental investigation into the mechanical properties of laser welded joints was carried out to establish a testing procedure using fiat micro tensile specimens (0·5 mm in thickness, 2 mm in width) for determination of the tensile properties of the weld metal and H AZ of the laser beam welds. Three similar joints, namely St 37–St 37, St 52–St 52, and austenitic–austenitic, and two dissimilar ferritic–austenitic joints were produced by CO₂ laser, using 6 mm thickness plates. The mechanical properties have been examined by microhardness survey and testing of conventional transverse tensile, round tensile, and fiat microtensile specimens. The results for the micro tensile specimens were compared with those for standard round tensile specimens and this clearly showed the suitability of the microtensile specimen technique for such joints.     

低合金高强钢激光电弧复合焊热模拟热影响区组织与冲击韧性

研制了一种Mn-Si-Ni-Cr系实心焊丝,用于新型船用440 MPa级低合金高强度(HSLA)钢焊接,采用热输入11.5,16.5和21.5 kJ/cm对该钢材进行了熔化极活性气体保护电弧焊,并使用光学显微镜、扫描电镜和透射电镜等设备重点研究了热输入对焊缝组织及性能的影响. 结果表明,随着热输入的增大,焊缝组织先以粒状贝氏体和板条贝氏体为主转变为以针状铁素体为主,再转变为以针状铁素体、侧板条铁素体和先共析铁素体为主,而且焊缝中M-A组元含量、直径大于 1 μm的夹杂物占比和夹杂物的平均直径均逐渐增大;随着热输入的增大,焊缝硬度不断减小,焊缝、熔合线和熔合线 + 2 mm处的冲击韧性均先增大后减小,同时焊缝的耐腐蚀性能也先增大后减小;3种焊接接头的板拉伸弯曲试样均在母材处断裂,弯曲试样均完好.     

RPC钢激光焊接CGHAZ的组织与性能

利用Gleeble-1500热模拟机进行了激光焊接条件下热模拟试验,研究了弛豫-析出-控制相变钢激光焊接热影响区粗晶区(CGHAZ)组织和性能。结果表明,CGHAZ组织为粒状贝氏体,具有较高的硬度、强度。CGHAZ韧性随t_8/5的增大先增大然后减小。当t_8/5为3~8s时,-40℃CGHAZ冲击吸收功远高于母材的冲击吸收功,表明在合适的激光焊接条件下,激光焊接CGHAZ可获得很好低温韧性。CGHAZ韧性随热输入的变化主要是由M-A组元的尺寸、总量、数量和形状综合决定的。     

异种钢焊接接头的监督管理

随着机组参数的不断提高,超(超)临界机组的投产,异种钢的焊接相当普遍,但是异种钢接头的失效也严重威胁到机组的安全运行。叙述了开展异种钢焊接接头金属技术监督的必要性和紧迫性,讨论了其监督的重点和方法,并结合案例进行了分析,为火力发电厂异种钢接头的监督管理提供了指导作用。