Achieving a high-strength dissimilar joint of T91 heat-resistant steel to 316L stainless steel via friction stir welding

The reliable welding of T91 heat-resistant steel to 316L stainless steel is a considerable issue for ensuring the safety in service of ultrasupercritical power generation unit and nuclear fusion reactor,but the high-quality dissimilar joint of these two steels was difficult to be obtained by traditional fusion welding methods.Here we improved the structure-property synergy in a dissimilar joint of T91 steel to 316L steel via friction stir welding.A defect-free joint with a large bonding interface was produced using a small-sized tool under a relatively high welding speed.The bonding interface was involved in a mixing zone with both mechanical mixing and metallurgical bonding.No obvious material softening was detected in the joint except a negligible hardness decline of only HV~10 in the heat-affected zone of the T91 steel side due to the formation of ferrite phase.The welded joint exhibited an excellent ultimate tensile strength as high as that of the 316L parent metal and a greatly enhanced yield strength on account of the dependable bonding and material renovation in the weld zone.This work recommends a promising technique for producing high-strength weldments of dissimilar nuclear steels.

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.

Arc characteristics of submerged arc welding with stainless steel wire

The arc characteristics of submerged arc welding （SAW） with stainless steel wire were studied by using Analysator Hannover （AH）. The tests were carded out under the same preset arc voltage combined with different welding currents. By comparing the probability density distribution （PDD） curves of arc voltage and welding current, the changes were analyzed, the metal transfer mode in SAW was deduced, and the characteristics of a stable arc were summarized. The analysis results show that, with an increase of welding parameters, the short-circuiting peak in the PDD curves of arc voltage decreases gradually until it disappears, and the dominant metal transfer mode changes from flux-wall guided transfer to projected transfer and then to streaming transfer. Moreover, when the PDD curves of arc voltage are both unimodal and generally symmetrical, the greater the peak probability and the smaller the peak span, the more stable the arc becomes.

Research on submerged arc welding wire for X100 pipeline steel

According to the study of the microstructure and properties of X100 pipeline steel, the welding consumable-wire based on Mn-Ni-Mo-B-Ti alloy system was successfully designed and developed. The yield strength of the deposited metal of the developed welding wire was 695 MPa, the tensile strength was 810 MPa, and Charpy impact energy was 92 J at negative 20 ℃ when matching with BSG-SJ101H1 sintered flux. The results of the weldability test for X100 pipeline steel which adopting this developed wire showed that the tensile strength of the weld was 827 MPa, 185 J of Charpy impact energy（ -10 ℃ ） , 97% of section of shear and the weld had good strength and toughness matching when the welding speed got to 1.7 m/min. The microstructure and fracture appearance of the weld were analyzed by using metallographic microscope, scanning electron microscope （SEM） and laser confocal microscope, the results indicated that the microstructure was mainly granular bainite in the weld metal, and the fracture was dimple with 200 - 300 μm depth presenting a typical ductile fracture characteristics. The test of welding wire with different content of Ni and Cr element indicated that Ni was better than Cr in improving the strength and toughness of weld metal.

Influence of Creep Strength of Weld on Interfacial Creep Damage of Dissimilar Welded Joint between Martensitic and Bainitic Heat-Resistant Steel

The mechanical properties, creep rupture strength, creep damage and failure characteristics of dissimilar metal welded joint （DMWJ） between martensitic （SA213T91） and bainitic heat-resistant steel （12Cr2MoWVTiB（G102）） have been investigated by means of pulsed argon arc welding, high temperature accelerated simulation, mechanical and creep rupture test, and scanning electronic microscope （SEM）. The results show that there is a marked drop of mechanical properties of undermatching joint, and low ductility cracking along weld/G102 interface is induced due to creep damage. Creep rupture strength of overmatching joint is the least. The mechanical properties of medium matching joint are superior to those of overmatching and undermatching joint, and creep damage and failure tendency along the interface of weld/G102 are lower than those of overmatching and undermatching joint after accelerated simulation for 500 h, 1 000 h, 1 500 h, and the creep rupture strength of medium matching joint is the same as that of undermatching joint. Therefore, it is reasonable that the medium matching material is used for dissimilar welded joint between martensitic and bainitic steel.

Microstructure and Fracture Morphology in the Welding Zone of T91 Heat-resisting Steel Used in Power Station

Microstructure performance in the welding zone of T91 heat-resistant steel under the condition of TIG welding was researched by means of metallography, X-ray diffraction and scanning electron microscope (SEM). Experimental results indicated that microstructure of T91 weld metal was austenite + a little amount of S ferrite when using TGS-9cb filler wire. Substructure inside the austenite grain was crypto-crystal lath martensite, on which some Cr23C6 blocky carbides were distributed. The maximum hardness (HRC44) in the welding zone is near the fusion zone. There existed no obvious softening zone in the heat-affected zone (HAZ). For T91 steel tube of $63 mmx5 mm, when increasing welding heat input (E) from 4.8 kJ/cm to 12 5 kJ/cm, fracture morphology in the fusion zone and the HAZ changed from dimple fracture into quasi-cleavage fracture (QC). Controlling the welding heat input of about 9.8 kJ/cm is suitable in the welding of T91 heat-resistant steel.

高速拉拔ER70S-6焊丝钢生产工艺优化

通过总结分析ER70S-6焊丝钢存在的质量问题,提出了有针对性的优化改进措施,重点对ER70S-6焊丝钢的化学成分范围、气体氮含量、尺寸精度、显微组织等关键指标严格控制,攻关后C、Si、Mn、N含量内控达标率提高,尺寸偏差C级精度得到改善,而且消除了混晶异常组织。用户拉拔使用结果表明,优化后的焊丝钢质量得到进一步的提高,可满足用户拉拔速度28 m/s以上高速拉拔的要求。

送丝速度对铝/钢激光熔钎焊接头组织与性能的影响

采用ER2319焊丝进行了6061-T6铝合金/Q235镀锌钢光纤激光熔钎焊接,分析了送丝速度对接头成型、显微组织与力学性能的影响。结果表明:当激光功率为1.2 kW,焊接速度为1.2 m/min时,送丝速度在1.2~3.0 m/min范围内均可获得有效接头。接头的抗拉强度随着送丝速度的增加呈现先上升后减小的趋势,当送丝速度为2.4 m/min时平均抗拉强度达到最大值,为116.15 MPa。当送丝速度为1.8、2.4 m/min时,接头的上下表面的金属间化合物层可控制在10μm以内,而对接界面处的金属间化合物层厚度随着送丝速度的改变变化不明显,对接界面的IMC层主要由FeAl、FeAl_(2)、Fe_(4)Al_(13)相组成。接头的断裂形式为典型的解理断裂模式,而位于润湿铺展在钢表面的铝合金处则为韧性断裂。

等离子熔覆硼化物覆层的耐蚀性

采用等离子熔覆技术将自制的Mo-Fe-B-Cr药芯焊丝熔覆在316L不锈钢表面制备了硼化物覆层,通过扫描电镜(SEM)、能谱仪(EDS)、X射线衍射仪(XRD)和显微硬度计对硼化物覆层的组织、成分、物相和显微硬度进行分析,并通过电化学试验和中性盐雾试验对覆层的耐蚀性进行研究。结果表明:硼化物覆层主要由MO_(2)FeB_(2)、(Mo,Fe,Cr)3B_(2)、α-Fe和Fe_(23)(C,B)6组成,其显微硬度约为不锈钢基体的3.9倍;在中性环境中硼化物覆层的耐蚀性略低于316L不锈钢,而在酸性环境中硼化物覆层的耐蚀性要优于316L不锈钢;在中性盐雾腐蚀过程中,硼化物覆层表面会生成致密性良好的钝化膜,从而使覆层具备良好的耐蚀性。因此,硼化物覆层在拥有高硬度的同时还兼具良好的耐蚀性。

磁场辅助窄间隙激光填丝焊焊接工艺研究

采用磁场辅助窄间隙激光填丝焊工艺对25 mm厚S32101双相不锈钢板进行多层焊接,并对其焊接性能进行了研究。观察对比了有无磁场辅助窄间隙激光填丝焊的焊缝成形,并重点分析了磁场辅助焊接接头的力学性能、金相组织。结果表明:有无磁场辅助得到的焊缝表面均平滑均匀,基本无飞溅。无磁场辅助的焊缝出现气孔及未熔合缺陷,施加磁场后焊缝无此缺陷。磁场辅助焊接的拉伸试样均断裂于母材位置,焊接接头的抗拉强度高于母材。各焊层焊缝的平均硬度高于母材。焊缝组织为奥氏体和铁素体,组织细密均匀,两相比例均匀稳定,约为1:1。

薄镀层热成形钢激光填丝焊的焊缝特征及性能

为降低镀覆在钢板表面的铝硅镀层对激光接头的不利影响,采用薄镀层热成形钢材料配合激光填丝焊技术,获得了焊缝内铝质量分数小于1%的激光填丝焊接头。对该接头进行了宏观及微观组织分析,发现热成形后焊接接头组织被全马氏体组织取代,避免了软化现象。力学性能分析表明,热成形前后试样的抗拉强度从约570 MPa提高到约1 500 MPa,接头的薄弱环节位于母材,高速拉伸对接头的抗拉强度没有不良影响,而断裂伸长率受影响较大。

1000 MPa级高强钢国产自研实心焊丝焊接工艺研究

针对国产自研的1 000 MPa级高强钢实心焊丝的熔化极气体保护焊工艺进行了系统性试验与分析。深入探讨了焊接电流和预热温度对接头微观组织、硬度分布以及力学性能的影响。研究发现,焊缝金属组织主要由马氏体构成,且随着焊接电流和预热温度的增加,贝氏体的含量相应增加;热影响区(HAZ)呈现出明显的硬化和软化趋势,细分为粗晶区、细晶区和不完全重结晶区;硬度在细晶区达到最高值,临界热影响区最低;在相同的预热温度下,随着焊接电流的增加,焊接接头的抗拉强度和冲击韧性呈现先增加后减少的趋势;而在相同的焊接电流下,抗拉强度和冲击韧性随预热温度变化的规律性不明显。当焊接电流为260 A,预热温度为100℃时,接头的力学性能最优,其抗拉强度高达1 088 MPa,-40℃时的冲击韧性达到47.8 J。

回火对E101T1-K3C熔敷金属显微组织和力学性能的影响

采用E101T1-K3C低合金高强钢药芯焊丝对EH620钢进行焊接。焊接接头分别在460℃、580℃进行保温1 h回火热处理,应用金相显微镜、材料试验机、冲击试验机、扫描电子显微镜等对试样进行分析与测量。结果表明:焊态下熔敷金属显微组织为条状铁素体+少量贝氏体+第二相颗粒,熔合区显微组织为片状铁素体+马氏体+第二相颗粒。焊接接头经过460℃×1 h焊后回火处理后,焊缝区的显微组织为铁素体+少量贝氏体+第二相颗粒,熔合区组织为铁素体+回火屈氏体+第二相颗粒。焊接接头经过580℃×1 h回火处理后,焊缝及熔合区显微组织均为铁素体+回火索氏体+第二相颗粒;熔敷金属屈服强度由725 MPa下降589 MPa,-40℃冲击吸收能量KV2由71 J提高到114 J;维氏硬度值在焊接接头焊缝及热影响区的分布趋向一致,焊接接头具有理想的力学性能。

高强钢焊接接头优化方法研究现状

高强钢以出色的力学性能在焊接结构的应用量急剧增加,其焊接接头性能已逐步成为研究焦点。为了解决高强钢焊接易出现冷裂纹、热影响区软化脆化、低温冲击韧度不高等问题,获得高强钢焊接接头优良强韧匹配。在使用熔化极气体保护焊接工艺的基础上采用不同的高强钢焊接接头优化方法,对严格控制热输入、焊前预热并控制热输入和研发并采用药芯焊丝这3种焊接接头优化方法进行分析总结,对3种优化方法下的焊接接头微观组织及力学性能进行分析,发现通过这3种接头优化方法可避免焊接接头产生裂纹、获得良好的韧性组织和力学性能优良的焊接接头。

实-药芯多丝电弧复合焊中药芯焊丝位置对焊接稳定性的影响

为了实现高强钢的优质高效焊接,提出了一种全新的Q960E高强钢的高效焊接工艺,即实-药芯多丝电弧复合焊工艺,该工艺通过一把集成式三丝焊枪实现两根实心焊丝复合一根药芯焊丝,既可以利用药芯焊丝实现焊接接头力学性能的优化,又可以利用3根焊丝实现高效焊接。其中药芯焊丝可以从两实心焊丝的正前方、正后方及侧面送入,通过对比分析焊接过程、焊道成形得出最佳药芯焊丝作用位置,并对最佳药芯焊丝作用位置下焊接接头的组织和显微硬度展开分析。结果表明:当药芯焊丝从正后方或侧面送入时,其中一根实心焊丝易与熔池接触发生短路过渡,前者会导致焊道宽窄不一,后者会导致焊道明显偏向药芯焊丝送入一侧。当药芯焊丝从正前方送入时,药芯焊丝呈一脉多滴过渡,且两实心焊丝均为一脉一滴过渡,此时焊接过程稳定,焊后焊道成形较好,焊道横截面形貌呈“双峰”状,是最佳的药芯焊丝送入位置。此外,当药芯焊丝从正前方送入时,焊缝区组织主要为细小的针状铁素体,粗晶区组织主要为粗大的板条马氏体和少量粒状贝氏体,细晶区组织主要为细小的马氏体,不完全淬火区组织主要为回火马氏体。此外,热影响区同时出现了软化和硬化现象,近不完全淬火区的母材硬度最低,仅为296 HV,完全淬火区硬度最高,达到396 HV,母材和焊缝区的硬度在320~340 HV之间。

12Cr2Mo1V钢凸台附加填充丝埋弧堆焊工艺研究

针对12Cr2Mo1V钢加氢反应器壳体凸台采用单丝埋弧焊进行堆焊、制造效率低的问题,研究了采用附加填充丝埋弧焊的焊接方法堆焊12Cr2Mo1V材质凸台本体的工艺可行性。研究结果表明,在12Cr2Mo1V钢上采用附加填充丝埋弧焊进行本体堆焊,焊接工艺性良好;其工艺评定试验的各项力学性能完全满足母材的要求,特别是-30℃夏比KV_(2)型缺口冲击试验冲击值均≥54 J,抗回火脆化倾向评定试验结果均满足v Tr54+3Δv Tr54≤0℃的要求。与单丝埋弧堆焊相比,两枪六丝附加填充丝埋弧堆焊凸台可提高生产效率200%~250%。该项工艺研究在满足加钒钢凸台性能的前提条件下,能极大缩短凸台制造周期、节能减排,为加氢反应器先进绿色制造的发展提供了新的制造手段。

焊接速度对铝钢异种金属激光填丝熔钎焊性能的影响

采用不同的焊接速度对铝合金E600及汽车车身用镀锌钢板DP590D+Z进行激光填丝熔钎焊试验,焊接材料选用ER4047焊丝,分别对不同焊接速度下的焊缝成形质量、金属间化合物层厚度及力学性能进行了分析研究。结果表明:选择适当的焊接参数时,利用激光填丝熔钎焊可获得成形良好且具有一定抗拉强度的熔钎焊接头。为保证焊缝接头的性能,需控制界面处主要成分为FeAl_(2)和FeAl_(3)的金属间化合物层的厚度,随着焊接速度的提升,线能量下降,金属间化合物层厚度随之减小。综合考虑接头的线载荷及生产效率,最优焊接速度为1.5 m/min,此时线载荷约为197 N/mm,换算成铝合金强度为219 MPa,相当于母材强度的81%。

超大线能量焊接用EH36厚钢板的开发及其焊接试验

在大型建筑、桥梁、造船、重型机械等领域,经常需要焊接厚钢板,使用常规的焊接方法可能会遇到焊接效率低下、焊接质量不稳定等问题。开发了一种大线能量焊接用的EH36钢板(厚80 mm),并采用线能量532 kJ/cm的双丝气电立焊进行超大线能量焊接试验。结果表明,经过大线能量焊接热循环后,粗晶热影响区不可避免地出现了粗化问题,原奥氏体平均晶粒尺寸为312μm,通过均匀分布的复合氧化物夹杂诱导,晶内可形成针状铁素体为主+少量侧板条铁素体的组织类型,使粗晶区能够获得较理想的韧性水平。其中,在-20℃条件下,钢板厚度中心熔合线冲击功为70~269 J,均值为179 J;在-40℃条件下,钢板厚度中心熔合线冲击功为50~216 J,均值为115 J。焊接接头各位置冲击性能良好,满足EH36钢板对焊接接头冲击性能的要求。

基于正交实验优化304不锈钢丝网吸液芯制备工艺

为制备混合型多孔丝网吸液芯,为金属热管的设计与加工提供基础数据,本文以100目、200目、300目304不锈钢丝网为原材料,试样采用电阻焊进行焊接,研究了搭接目数、搭接角度、焊点间距以及焊接能量对组合型丝网吸液芯的拉伸和顶破性能.研究结果表明:搭接目数对试样的拉伸与顶破性能影响最大,焊接能量对试样的拉伸与顶破性能的影响最小.