聚变堆用CLAM钢激光焊接接头显微组织及性能

对聚变堆用CLAM钢进行了激光焊接试验,并对接头进行740℃/1 h焊后回火处理,分别对热处理前、后接头的显微组织及性能进行了研究.结果表明,获得了成形良好、无缺陷的焊接接头;焊态下,焊缝由淬硬的板条马氏体和大量的δ铁素体组织组成.完全淬火区由板条马氏体和极少量的δ铁素体组成,其硬度高达545 HV;焊后热处理使焊缝及完全淬火区的板条马氏体分别转变为碳化物弥散分布的回火马氏体和回火索氏体组织.显著降低了接头的淬硬程度,最大硬度仅比母材高约15%;焊后回火热处理前、后接头的抗拉强度均高于基体母材,虽然焊后热处理使接头强度有所降低,但仍达到原始母材的98%以上.     

Effect of post weld heat treatment on properties of variable polarity TIG welded AA2219 aluminium alloy joints

AA2219 aluminium alloy joints were fabricated by variable polarity tungsten inert gas (VPTIG) welding process and the effects of post weld heat treatment (PWHT) on the tensile properties, microstructure and fatigue behaviour of the welded joints were investigated. The VPTIG welding process was adopted because it could meet the need of cathode cleaning and meanwhile it could reduce the deterioration of tungsten electrode furthest. The welded samples were divided into as-welded (AW) sample and PWHT sample. The PWHT method used on the samples was solution treatment (535 °C, 30 min), water quenching and artificial aging (175 °C, 12 h). The experimental results show that, compared with the AW samples, the microstructure characteristics and mechanical properties of the AA2219 joints after PWHT were significantly improved. The improvement of yield strength, ultimate tensile strength, and fatigue strength are 42.6%, 43.1% and 18.4%, respectively.     

焊后热处理对拘束焊焊缝金属冲击韧性与断裂韧性的影响

针对DH36钢厚板拘束焊焊接接头进行了620 ℃ × 2 h的焊后热处理，测试了热处理前后焊缝金属的冲击韧性和断裂韧性，对比分析冲击韧性与断裂韧性的差异，同时研究了焊后热处理的影响及其韧化机制. 结果表明，焊态下焊缝金属的冲击韧性良好，而断裂韧性较差；焊后热处理后，冲击韧性没有明显变化，但断裂韧性显著上升，平均CTOD值由0.123 mm显著升高至0.707 mm. 一方面，焊后热处理引起位错密度降低，位错缠结显著减少，细小碳化物析出并球化，有利于韧性的改善；另一方面，焊后热处理可消除大厚板拘束焊产生的应变时效局部脆化现象，提高断裂韧性. 由于冲击韧性与断裂韧性测试结果存在较大差异，采用单一温度的冲击韧性评估拘束焊焊缝金属的韧性与结构安全性可能存在风险.     

Effects of PWHT on Microstructure and Mechanical Properties of Weld Metals of Ni-Based Superalloy 617 and 263 for Hyper-Supercritical Power Plants

It is well known that solid solution-strengthened alloy 617 and γ' precipitation-strengthened alloy 263 have excellent mechanical properties and corrosion resistance at high temperatures.Hyper-supercritical power plants work at temperatures above 700 ℃,and these superalloys are considered candidate materials for steam turbines components of these power plants.In this study,gas tungsten arc weldability of these superalloys was evaluated,and the effects of postweld heat treatment(PWHT) on the microstructural characteristics and the mechanical properties of their weld metals were investigated.Scanning transmission electron microscopy,energy-dispersive spectroscopy and electron probe microanalysis were utilized for the investigation.The experimental results confirmed that these weld metals had different characteristics in microstructure and mechanical properties.PWHT resulted in the precipitation of intergranular carbides,γ' particles and an increase in tensile strength of these superalloy weld metals.Furthermore,fine γ' particles,which were not detected in the as-welded metal of alloy 263,were precipitated after PWHT and those particles were the reason for the drastic increase in tensile strength.     

焊后热处理对DH36钢焊接接头断裂韧性的影响

针对DH36钢厚板拘束焊焊接接头进行了620 ℃ × 2 h的焊后热处理,测试了热处理前后焊缝金属的冲击韧性和断裂韧性,对比分析冲击韧性与断裂韧性的差异,同时研究了焊后热处理的影响及其韧化机制. 结果表明,焊态下焊缝金属的冲击韧性良好,而断裂韧性较差;焊后热处理后,冲击韧性没有明显变化,但断裂韧性显著上升,平均CTOD值由0.123 mm显著升高至0.707 mm. 一方面,焊后热处理引起位错密度降低,位错缠结显著减少,细小碳化物析出并球化,有利于韧性的改善;另一方面,焊后热处理可消除大厚板拘束焊产生的应变时效局部脆化现象,提高断裂韧性. 由于冲击韧性与断裂韧性测试结果存在较大差异,采用单一温度的冲击韧性评估拘束焊焊缝金属的韧性与结构安全性可能存在风险.     

奥-贝球铁焊接研究进展

介绍了近１０年来奥－贝球铁焊接研究进展,重要介绍了奥－贝球铁焊接冶金,获得奥－贝球铁焊缝金属的等温热处理工艺和焊接工艺特点,焊态直接获得奥－贝球铁焊缝的途径及奥－贝球铁焊接新材料。奥－贝球铁焊缝金属可以通过等温热处理获得,也可以在焊态下直接获得。对于前者,研究工作主要集中在合金元素对球铁焊缝白口倾向的影响,球铁焊缝金属等温转变及组织结构特点,等温热处理工艺对奥－贝球铁焊缝组织与力学性能的影响。而对于后者的研究则更多地集中于焊缝化学成分和冷却速度对焊态奥－贝球铁焊缝组织与力学性能的影响。研制成功的奥－贝球铁焊接新材料,其焊缝的组织与力学性能满足奥－贝球铁的要求。     

Postweld solution annealing effects on the ductility of ni-co-cr-base alloy gas tungsten arc welds

The welding characteristics of a commercial wrought alloy with a nominal composition of Ni-29Co-28Cr-2.75Si were investigated. Gas tungsten arc weldments with filler metal matching the chemistry of the alloy were found to have limited room-temperature ductility in the as-welded condition. Since welding is the main fabrication method of this alloy, the welding and postweld heat treatment (PWHT) characteristics were examined to provide guidelines for fabrication in the field. Metallographic evaluation revealed that the weld metal was characterized by the distribution of a continuous eutectic phase consisting primarily of (Si,Ti)_xNi_y The continuous eutectic phase in the as-welded deposit, which caused poor ductility of the welds, was successfully reduced or removed with proper PWHT. The PWHT is necessary if cold forming of a weldment is required after welding or if adequate joint ductility is a design requirement. The recommended PWHT temperature is 1050 °C.     

The corrosion behavior of Fe-Mn-Al weld metals

The corrosion resistance of a newly developed iron-base, Fe-Mn-Al austenitic, and duplex weld metal has been examined in the NACE solution consisting of 5 wt.% NaCl, 0.5 wt.% acetic acid, and the balance distilled water. The electrochemical techniques such as potentiodynamic polarization, Tafel plots, linear polarization, cyclic polarization, and open-circuit potential versus time were employed. The Fe-Mn-Al weld metals did not passivate and exhibited high corrosion rates. Fe-Cr-Ni (310 and 316) weld and base metals were also examined in the NACE solution at room temperature. The 310 and 316 base metals were more resistant to corrosion than the as-welded 310 and 316 weld metals. Postweld heat treatment (PWHT) improved the corrosion performance of the Fe-Mn-Al weld metals. The corrosion resistance of Fe-Mn-Al weld metals after PWHT was still inferior to that of the 310 and 316 weld and base metals.     

Characterization of microstructure of HAZs in as-welded and service condition of P91 pipe weldments

Steels 9-12% Cr, having the high creep rupture strength are advocated for the modern low polluting thermal power plants. In the present investigation, the P91 pipe weldments have been characterized for microstructural responses in as-welded, post-weld heat treatment (PWHT) and ageing conditions. The PWHT of welded samples were carried out at 760 °C for time of 2 h and ageing at 760 °C for 720 h and 1440 h, respectively. The effect of time has been studied on precipitates size, distribution of precipitates and grain sizes present in various zones of P91 steel weldments. The impact toughness and hardness variation of heat affected zone (HAZ) have also been studied in as-welded condition as well as at different heat treatment condition. A significant change was observed in grain size and precipitates size after each heat treatment condition. The maximum impact toughness of HAZ was obtained after PWHT at 760 °C for 2 h. The main phase observed in weld fusion zone in as-welded, PWHT and ageing conditions were M₂₃C₆, MX, M₇C₃, Fe-rich M₃C and M₂C. The unwanted Z-phase (NbCrN) was also noticed in weld fusion zone after ageing of 1440 h.     

Comparison of operational performance and bead characteristics when welding with different tubular wires

The aim of this work was to make a comparative study of the characteristics of the weld bead produced by nationally manufactured tubular wires; all rutilic (ASME SFA-5.20: E71T-1/E71T-9/E71T-9M), basic (ASME SFA-5.20: E71T-5/E71T-5M) and ‘metal cored’ (ASME SFA-5.18: E70C-3M), 1.2 mm in diameter, intended for the welding of structural steels with low and medium levels of carbon. Welding tests were carried out, in the flat position, on thick plates (with a thickness of 12 mm) of common low-carbon steel using a source operating in ‘constant voltage’ mode, with monitoring of the current and voltage signals of the arc and feed speed (fusion) of the wire. The following were varied in welding with each type of tubular wire: the composition of the shielding gas (75%Ar–25%CO₂ and 100%CO₂) and the feed speed of the wire (7 and 9 m/min). The other parameters were kept fixed, including the polarity of the electrode (DC+) and the energized lengths of the electrode (16 mm) and of the arcs (3.5 mm). For the different tubular wires, there was a comparative analysis of the principal weld bead characteristics, including its geometry (penetration, reinforcement, width, fused area, deposited area and dilution), presence of weld discontinuities, microstructure and hardness. Operational conditions that yielded weld bead characteristics that favoured the welding of thick plates of structural steels were determined.     

V含量及回火工艺对高强钢TIG焊熔敷金属组织性能的影响

采用四种不同V含量焊丝对高强钢板进行钨极氩弧焊试验,焊后对熔敷金属进行640 ℃保温2 h的回火处理. 研究了V含量和回火处理对熔敷金属微观组织及力学性能的影响. 结果表明,焊态及焊后回火态条件下,随着V含量的增加,熔敷金属强度升高,延伸率和冲击功降低,经回火处理后,不含V熔敷金属内晶界处析出M₂C碳化物,而含V熔敷金属内析出弥散分布的VC析出相,焊后回火过程中位错回复引起基体软化的作用高于M₂C及VC的析出强化作用,导致回火后强度降低,断后伸长率冲击吸收能量升高. 细小VC具有阻碍位错运动的作用,导致回火后含V熔敷金属仍保留较高的位错密度. 实际应用中应根据熔敷金属性能要求合理选择V含量及焊后回火工艺.     

三维管接头焊后局部热处理加热宽度准则

提出了直接定量评定管接头焊后局部热处理应力释放效果的方法。构造了三维管接头焊接应力和局部热处理温度场,采用粘弹塑性有限元方法对管接头焊后不同局部热处理条件不应力分布特征进行了研究,对单道焊情况,不同焊接规范下的焊接应力分布具有相似性,焊接顺序对应力峰值位置的影响较小。对管接头热点处焊接应力在不同局部热处理条件下释放程度做了分析,在局部热处理加热宽度足够大情况下残余应力明显下降,周向和轴向应力分量与加热宽度的关系不同,周向和轴向应力的最优加热宽度分别为3.46√-Rr的4.8√-Rt。通过对局部热处理主要工艺参数的计算,推荐了正交管接头局热处理加热宽度准则。     

Improving 410NiMo weld metal toughness by PWHT

Highlights of the present study is the importance of choosing suitable temperatures for two stage PWHT to achieve desirable toughness in the weld metals produced by ER 410NiMo filler wire. Weld pads prepared using this filler wire was used for extensive metallurgical characterization of the weld metal. Results indicate by choosing appropriate temperatures for the PWHT, it is possible to obtain toughness in the weld metal which is comparable to the toughness reported for the base metal of similar composition. Good toughness of the weld metal is attributed to the presence of retained austenite in the weld metal. Two stage PWHT that gave excellent toughness for the weld metal was employed for repair of cracked shrouds of a steam turbine in a nuclear power plant. The metallurgical characterization of the mock up weld pad prepared prior to actual repair confirmed that microstructure and hardness of the weld metal are similar to those obtained during the welding procedure development.     

低温管线K65热煨弯管用埋弧焊丝研制

设计了NiMoTiB体系实芯焊丝用于低温管线K65热煨弯管的埋弧焊接,并采用φ4.0 mm焊丝、双面四丝埋弧焊开展了壁厚30.8 mm直缝管试制,然后利用热煨弯制工艺制成弯管,并分别测试了直缝管和弯管的焊缝金属微观组织及力学性能.结果表明,焊态直缝管焊缝组织以针状铁素体为主,以及少量贝氏体及马氏体-奥氏体岛（M-A）;焊缝金属抗拉强度670 MPa,-40℃冲击吸收功为162 J.经过淬火+回火处理的热煨弯管焊缝主要由块状铁素体和尺寸1~5 μm的退化珠光体组成;焊缝金属抗拉强度665 MPa,-40℃冲击吸收功84 J,能够满足低温管线钢K65的标准要求.     

2195铝锂合金电子束焊接头的焊后热处理

采用光学显微镜、扫描电镜、能谱仪及X射线衍射仪等微观分析手段,研究不同热处理工艺条件下2195铝锂合金电子束焊接头焊缝区的显微组织演变,探讨接头的焊后热处理强化机制。结果表明,焊后热处理可显著改善接头区域的显微组织,促进强化相的析出,有利于提高接头的力学性能。经过焊后固溶+双级时效热处理,焊态下接头熔合线附近存在的等轴细晶区消失,β′、θ′和T₁等强化相在接头焊缝区析出,与单级时效处理工艺相比,双级时效处理的析出强化效果更为显著。力学性能测试表明,经过双级时效热处理后,接头的抗拉强度达到492.5 MPa,为母材强度的90.4%。接头拉伸断口表面存在许多小韧窝,并伴随出现解理面,接头呈韧-脆混合型断裂特征。     

Optimal Weld Parameters, Weld Microstructure, Mechanical Properties, and Hydrogen Absorption: An Effective Analysis

Weld bead-in-grooves were deposited on low alloy, high strength steel plates (ASTM A 517 Grade “F”) with a commercial flux-cored filler wire, Auto-MIG 420, at different welding conditions. Microstructure and mechanical properties of welds were characterized by means of optical microscopy, SEM, TEM, EPMA, microhardness measurements, tensile tests, and Charpy impact tests. Hydrogen content of weld metals in as-weld condition and after exposing in simulated service condition was measured by LECO Gas Analyzer. Microstructure of weld metals consisted primarily of lath martensite with small amount of M-A constituents (Martensite-Austenite alternating layers). For some particular welding conditions, such as higher heat input and lower preheat temperatures etc., acicular ferrite is observed with lath martensite. Welds consisting of acicular ferrite in the microstructure showed improved mechanical properties as well as lower hydrogen absorption. The study provides guidelines for selecting proper welding conditions, which results in lower propensity to absorb hydrogen during service, as well as better mechanical properties. Necessity of post-weld heat treatment processes, which is mainly performed to achieve toughness, may be reduced; consequently saving cost and time of the welding process.     

药芯焊丝CO2焊在复合钢制压力容器中的应用

介绍了用药焊丝CO2焊焊接16MnR/SUS321不锈钢合钢板压力容器的焊接工艺试验及焊接工艺评定，通过检查焊缝的化学成分，硬度，金相组织，测定接头的力学性能，晶间腐蚀试验等，证明药芯焊丝CO2焊用于不锈复合钢压力容器制造是可行的，对不锈复合压力容器的焊接要点进行了简要说明。     

Influence of process variables on weld bead quality in two wire tandem submerged arc welding of HSLA steel

Two-wire tandem submerged arc welding process involves simultaneous depositions from two electrode wires with the leading wire usually connected to a DC power source and the trailing wire connected to a pulsed AC power source. The weld bead profile and mechanical properties in the tandem submerged welding are significantly affected by the leading and trailing wire current transients and the welding speed. We present here a detailed experimental study on the influence of leading wire current, trailing wire current pulses, and welding speed on the weld bead dimensions and mechanical properties in single-pass tandem submerged welding of a typical HSLA steel. It is realized that the weld bead penetration is primarily influenced by the leading wire current while the weld bead width and the reinforcement height are sensitive to the trailing wire current pulses. Greater magnitude of trailing wire current pulses and shorter negative pulse duration increase the weld pool volume leading to reduced cooling rate and poor mechanical properties as the formation of the strengthening phases like acicular ferrite is inhibited. In contrast, increase in welding speed reduces the rate of heat input thereby enhancing the cooling rate and the weld bead mechanical properties. A set of empirical relations are developed to estimate the weld bead dimensions and mechanical properties as function of the welding conditions. The predictions from the empirical relations and the corresponding measured results are observed to be in fair agreement.     

采用镍基和奥氏体焊材焊接Cr13钢焊接接头性能

采用ER309L氩弧焊丝的奥氏体焊材和ERNiCrFe-3镍基焊丝的镍基焊材对Cr13钢母材进行TIG焊接,通过无损检测、显微组织、力学性能和耐腐蚀性能试验,对两种焊材的焊接接头性能进行研究.结果表明,两种焊接接头均未发现焊接缺陷,焊接接头属于高强匹配,弯曲性能合格.与奥氏体焊材焊缝相比,镍基焊材的焊缝冲击韧性低,硬度高,耐电化学腐蚀性能高.     

热连轧高强钛合金厚壁管道的TIG工艺及组织和性能

针对采用新型的热连轧工艺生产的厚壁高强度无缝钛合金管,通过TIG自动送丝与手工填丝2种焊接方法进行了环缝对接焊工艺试验,对比分析了2种工艺下接头的焊缝成形、微观组织及力学性能。结果表明,2种焊接方法下的焊道表面均呈亮银色,无明显氧化现象,自动送丝接头表面成形更加平滑美观,而手工填丝接头表面成形有不规则的鱼鳞纹;热影响区中β相均发生了一定程度的粗化,并生成了一定量的细针状α’马氏体相。焊缝区组织主要为沿β相界生成的板条状和块状α相,以及晶粒内形成的少量针状α’马氏体组织;TIG自动送丝和手工填丝焊接接头的硬度都是热影响区最高,焊缝最软而母材居中;拉伸试验断裂位置均位于焊缝,平均抗拉强度分别为603.8 MPa和571.7 MPa;热影响区的冲击吸收能量分别达到了41.7 J和78.5 J,手工填丝下的热影响区表现出了比母材更好的冲击韧性。创新点： (1)研究了热连轧工艺下新型钛合金管道手工TIG/自动TIG工艺下的组织及力学性能,2种工艺均采用多层多道焊技术。(2)2种工艺采用纯钛焊丝进行填充时,接头抗拉强度均高于母材;焊缝及热影响区冲击韧性均高于母材;焊缝由于纯钛焊丝合金元素低,冷却下来焊缝位置形成的马氏体含量低。(3)手工TIG/自动TIG多层多道工艺下复杂的热过程起到了合适的热处理作用,热影响区形成了大量重叠交织的α组织,使得热影响区的冲击韧性大幅度提升,解决了该系钛合金常规焊接工艺下热影响区冲击韧性差的问题。