焊接方法对Fe-Cr-Ni-Mo系熔敷金属组织和性能的影响

分别采用钨极氩弧焊(TIG焊)和熔化极活性气体保护焊(MAG焊)方法制备了785 MPa级Fe-Cr-Ni-Mo系熔敷金属.利用扫描电子显微镜、透射电子显微镜和电子背散射衍射仪对熔敷金属的组织类型和晶体学特征进行了详细的表征分析,结果表明,采用不同焊接方法制备得到的熔敷金属组织均为贝氏体,但钨极氩弧焊熔敷金属(DM-TIG)中出现大量聚合贝氏体;由于焊接过程中使用的保护气体不同,熔化极活性气体保护焊熔敷金属(DMMAG)中存在大量夹杂物.经过电子背散射衍射分析结果表明,相比于DM-TIG,DM-MAG中由于存在大量自催化形核现象,晶体学取向非常复杂.力学性能测试结果表明,DM-MAG中大尺寸夹杂物在冲击过程中作为裂纹源,从而导致DM-MAG的韧性明显低于DM-TIG,实际工程应用中对于低温韧性要求较高的结构部件应合理选择焊接方法.     

焊接方法对316LN奥氏体不锈钢焊缝金属低温韧性的影响

采用手工TIG焊、手工MAG焊及窄间隙自动TIG焊分别对超导聚变堆用316LN奥氏体不锈钢进行焊接试验,并在液氮温度下进行夏比冲击试验。利用光学显微镜(OM)、扫描电镜(SEM)、能谱分析(EDS)等研究了接头微观组织及夹杂物对奥氏体不锈钢焊缝金属低温韧性的影响。结果表明,两种TIG焊焊缝金属77K冲击韧性均达到100J以上,满足超导聚变堆设计要求。手工MAG焊焊缝金属77 K冲击韧性不到80 J,未能达到要求,其焊缝中具有方向性的粗大柱状晶及Si O2等硬脆夹杂物的大量析出导致手工MAG焊焊缝金属低温韧性最低。窄间隙自动TIG焊微观组织为大量胞状晶,气体保护效果好,夹杂物少,且母材中含量较高的S元素形成高塑性的MnS包裹在硬脆夹杂物上,其低温冲击韧性最好。手工TIG焊焊缝微观组织较手工MAG焊要好,但气体保护效果比窄间隙自动TIG焊要差,夹杂物较多,其低温韧性介于二者之间。     

超级马氏体不锈钢焊丝MAG焊熔敷金属冲击性能优化

白鹤滩百万千瓦水电机组全部采用国产HS13/5L焊丝进行焊接，成功实现了中国高端装备制造的重大突破. HS13/5L焊丝为水轮机转轮同材质焊接材料，属于13Cr型超级马氏体不锈钢，然而其MAG焊熔敷金属的韧性低于母材，针对此问题，将现有的MAG平焊焊接工艺调整为立向上焊焊接工艺，以提高熔敷金属的冲击韧性.对比分析了平焊、立向上焊熔敷金属的微观组织和冲击性能. 结果表明，立向上焊位置回火热处理态熔敷金属的室温冲击吸收能量达到120 J以上，比平焊位置提高了约40%. 两种焊接位置下的熔敷金属微观组织的相组成无明显差异，焊态组织为淬火马氏体 + 残余奥氏体 + δ-Fe，回火热处理态组织为回火板条马氏体 + 逆变奥氏体 + δ-Fe.立向上焊熔敷金属中的氧化夹杂物密度比平焊位置降低了约22%.平焊和立向上焊熔敷金属冲击断口整体呈现出韧性断裂的特征，立向上焊位置熔敷金属的韧性优于平焊位置.     

HS-80高强钢焊丝激光-MAG复合焊熔敷金属特性

研究了HS-80焊丝激光-MAG复合焊和MAG焊两种焊接方法的熔敷金属特性.与MAG焊相比,激光-MAG复合焊熔敷金属的屈服强度、抗拉强度和冲击韧度显著提高,熔敷金属的组织更加细小,合金元素过渡系数增大.高速焊接导致的熔池金属冷却速度快及熔池金属流动性的增加是导致复合焊熔敷金属组织细化的主要原因.焊缝金属中Ti,Mo等...     

焊接方法对超低碳马氏体不锈钢焊丝熔敷金属冲击韧性的影响

针对大型水轮机转轮焊缝金属冲击韧性偏低,研究了不同焊接方法和气体含量对超低碳马氏体不锈钢熔敷金属冲击韧性的影响.结果表明,TIG焊和激光-MIG复合热源焊可有效提高熔敷金属的冲击韧性.TIG焊适合于不锈钢转轮的少量补焊,激光-MIG复合热源焊可在叶片与上冠及下环的组焊中推广应用.随着熔敷金属中C,[O],[N]元素含量的增加,熔敷金属的冲击韧性降低,但[O]元素含量是控制冲击韧性的决定因素.当熔敷金属中[O]元素含量较高时,形成较多球形氧化夹杂物,成为裂纹源,降低了冲击启裂功和裂纹扩展功,使冲击韧性明显降低.     

氧对00Cr13Ni5Mo熔敷金属组织和韧性的影响

文中研究了MAG焊保护气体氧含量变化对00Cr13Ni5Mo熔敷金属中氧化物夹杂类型、尺寸、数量、分布和残余奥氏体、逆变奥氏体含量以及冲击韧性的影响.结果表明,Si-Mn-O,Si-Mn-Al-O复合氧化物夹杂是导致00Cr13Ni5Mo熔敷金属冲击韧性下降的主要原因.氧化物夹杂对00Cr13Ni5Mo熔敷金属回火过程中产生的逆变奥氏体具有抑制作用,随着氧化物夹杂的增加,逆变奥氏体含量呈减少趋势.     

热输入量对一种新型药芯焊丝熔敷金属组织及冲击韧性的影响

采用自行研究开发的一种新型药芯焊丝,通过实验室大热输入焊接实验,研究分析了热输入量对焊缝熔敷金属组织与冲击韧性的影响规律.结果表明:在大热输入焊接条件下,熔敷金属中形成了大量细小、弥散分布的夹杂物,夹杂物周围诱导生成的大量相互交叉互锁的针状铁素体晶粒,这是焊缝熔敷金属具有较高低温冲击韧性的主要原因;随着焊接热输入量的增加,尺寸为1μm以下的夹杂物数量减少,1μm以上夹杂物分布无显著变化,针状铁素体形核点减少,熔敷金属中针状铁素体晶粒尺寸略有增加、低温冲击韧性略有降低.     

热输入及热处理对12Cr2Mo1R钢埋弧焊熔敷金属组织和性能的影响

对12Cr2Mo1R钢埋弧焊丝极材料进行了试验研究,分析了焊接热输入及焊后热处理对熔敷金属组织和力学性能的影响。结果表明,12Cr2Mo1R钢焊接材料熔敷金属组织主要为回火贝氏体。随着焊接热输入的增加,熔敷金属的强度呈下降趋势,而其冲击韧性先升高后降低。在焊接热输入20~28. 29 kJ/cm的范围内焊接,可以获得较好的强度和韧性。当焊接热输入为22 kJ/cm时,熔敷金属获得最佳韧性。随着回火参数P值的增加,熔敷金属的强度呈下降趋势,而其冲击韧性先升高后降低。试验用焊接材料的P值为19. 26~20. 71时,可以获得较好的强度和韧性。当P值为20. 62时,熔敷金属冲击韧性最佳。     

热输入对F69A4-ECM4-M4金属芯埋弧焊丝熔敷金属组织和力学性能的影响

采用F69A4-ECM4-M4金属芯埋弧焊丝在不同的热输入(18.67,20.57,22.56,24.63 kJ/cm)下焊接熔敷金属,并通过光学显微镜和扫描电镜对其组织进行了观察分析,采取冲击试验方法测试冲击韧性. 结果表明,不同热输入的熔敷金属其组织形态和数量也有着明显的差异;随着热输入的增加,其熔敷金属中柱状晶的宽度逐渐增大,-40 ℃的冲击韧性逐渐降低,断口形貌中放射区比例逐渐增加. 当热输入为18.67 kJ/cm时,熔敷金属显微组织主要由细小的针状铁素体组成,冲击吸收功达到最大值139 J. 随着热输入的增加,熔敷金属高温停留时间长,熔敷金属组织中针状铁素体晶粒急聚长大,从而导致熔敷金属冲击韧性的下降.     

不同焊接方法对TWIP钢焊后热影响区组织和性能的影响

文中对Fe-Mn-C系TWIP钢的焊接行为进行了系统研究,采用激光焊和钨极氩弧焊(TIG)进行了焊接试验,对两种焊接方法的焊后热影响区的显微组织及力学性能进行了分析.结果表明,激光焊后焊接热影响区(HAZ)及焊缝组织更为细小,分布也更为均匀,断后伸长率明显好于TIG焊.焊缝的显微硬度要高于HAZ和母材,TIG焊后HAZ晶粒严重长大,显微硬度在HAZ处也明显降低,出现了软化,导致综合性能偏差.     

980MPa高强钢焊接接头薄弱环节的确定

通过在低温下进行拉伸试验、冲击试验以及扫描电镜下的断口观察,对屈服强度为980 MPa新型高强钢的MAG和TIG焊接接头的性能和断裂机理进行了研究,并在此基础上确定焊接接头的薄弱环节,提出其薄弱环节对接头整体性能的影响规律.结果表明,这两种焊接方法焊缝金属的抗拉强度与母材相差不大,但其断面收缩率有所降低;焊缝金属尤其原...     

Effects of weld metal property and fraction on the toughness of welding joints of a 8%Ni 980 MPa high strength steel

This work investigated the variations of Charpy V toughness which was measured in various parts of welding joints of a 980 MPa steel. The welding joints were composed of multi-pass weld metal, heat affected zones (HAZs) and base metal. Two types of weld metals, one with inferior toughness and the other with comparable toughness to the base metal, were used to reveal the effects of weld metal property and fraction on the toughness of the welding joint as a whole. The notches of Charpy V specimens were located at various sections of the welding joints where the ligaments comprised various fractions of weld metal. The results revealed that the weld metal with inferior toughness, even in a fraction as low as 20%, caused remarkable deterioration on the impact toughness of the welding joint. The weld metal with comparable toughness had little effect on the properties of the welding joint. The microstructures and fracture surfaces were observed to analyze the mechanism of the inferior toughness in a MAG weld metal.     

Influence of Ti on non-metallic inclusion formation and acicular ferrite nucleation in high-strength low-alloy steel weld metals

The phase transition behaviors of non-metallic inclusions as a function of Ti content were investigated by monitoring changes in the microstructure and mechanical properties of high-strength low-alloy steel multipass weld metals. Weld metals with Ti contents ranging from 0.007 to 0.17 wt% were prepared using a gas metal arc welding process. The inclusion analysis was performed based on thermodynamic calculations and transmission electron microscopy, accompanied by energy-dispersive spectrometry and selected area electron diffraction. With increase in the Ti content of weld metals, the chaotic arrangement of ferrite laths in the columnar zone was transited to a well aligned arrangement and the impact toughness of the weld metals drastically deteriorated in response to the decrease in the Mn content of the inclusion. The effective inclusion phase for intragranular nucleation contained considerable amounts of Mn and a Mn depleted zone was observed around the effective nucleant.     

N和O元素引入对GPCA-TIG焊焊缝冲击韧性的影响

通过外层气体引入O和N元素,气体熔池耦合活性TIG焊(gas?pool?coupled?activating?TIG?welding)可以实现深熔深、高质量和连续焊接.?为了研究清楚O和N元素引入对焊缝冲击韧性的影响规律和机理,针对SUS304不锈钢分别测试了外层气体为O2,N2和O2?+?N2时的焊缝低温冲击韧性,并...     

Mechanical properties improvement of thick multi-pass weld by layered ultrasonic impact treatment

The effects of layered ultrasonic impact treatment (LUIT) on the mechanical properties of thick multi-pass weld were investigated. Two 55-mm thick multi-pass welding joints were prepared, one was treated with LUIT, and the other was joined with conventional welding method. Shear-punch test and Charpy impact test were used to examine the mechanical properties of both joints. Results show that LUIT can increase the strength of weld metal (WM), resulting in more uniform shear strength distribution across the treated WM and higher impact toughness of the WM. The mechanical properties improvement of WM attributes to the oxidation of metals induced by ultrasonic impact treatment, which increases the oxygen content in the WM and causes more non-metallic oxide inclusions, and then affects the grain growth behaviour of the subsequent beads, resulting in a fine-grained microstructure and improved strength and toughness of the WM.     

Comparison of Microstructure and Residual Stress Between TIG and MAG Welding Using Low Transformation Temperature Welding Filler

A Cr–Ni type of low transformation temperature(LTT) welding filler was devised in the present study. The LTT weld microstructures of the tungsten inert gas(TIG) and metal active gas(MAG) weldings were investigated by using electron-backscattered diffraction and orientation imaging microscopy. The results showed that the LTT weld microstructures prepared by TIG and MAG weldings were primarily martensite with 17.5% and 8.0% retained austenite,respectively. The LTT weld metal using TIG welding had larger grain size than using MAG. In addition, based on the Taylor factor calculation, the weld metal using MAG welding was more competent in repressing fatigue crack initiation.Meanwhile, the high angle and coincidence site lattice grain boundaries were dominant in the LTT weld metal using MAG welding. Moreover, the hardness of the LTT weld metal using MAG welding was higher than that of using TIG. Based on heat input and phase transformation, finite element method was applied to analyzing the tensile residual stress(RS)reduction in welded joints prepared by both conventional and LTT welding fillers, respectively. The corresponding outcome confirmed that the LTT weld metal using MAG welding was more beneficial to tensile RS reduction.