S355J2W钢高频脉冲MAG焊T-HV焊缝的组织和性能

文中选用直径分别为1.2 mm和1.6 mm的焊丝,对S355J2W耐候钢进行高频脉冲MAG焊工艺试验,接头为T形接头,通过对焊接接头宏观形貌观察和微观组织分析,2种工况焊缝成形均良好,实现了单面焊双面成形,且在较小热输入的条件下采用直径1.6 mm焊丝打底也可防止产生根部未熔合、未焊透缺陷,避免了气孔、夹杂及裂纹的产生。接头显微组织特征类似,焊缝为较多的先共析铁素体(GBF)、针状铁素体(AF)和少量珠光体(P)及粒状贝氏体(BG)组织,未见向晶界内生长的塑性较差的侧板条铁素体(FSP);熔合区主要为一定量的先共析铁素体(GBF)、针状铁素体(AF)组织,少量的珠光体(P)、粒状贝氏体(BG)组织,靠近焊缝侧晶粒较细小,靠近过热区侧晶粒较粗大;过热区主要是较多的细条状铁素体(IGF)、粒状贝氏体(BG)和少量珠光体(P)组织,晶粒大小比较均匀。采用Image-Pro Plus软件测量和计算了焊缝中针状铁素体占比,与直径1.2 mm焊丝相比,采用直径1.6 mm焊丝的焊缝中针状铁素体增加了10%。硬度测试结果表明：2种工况焊接接头的硬度值均在母材处出现最小值,在过热区出现最大值,且硬度...     

S355J2W+N耐候钢焊接接头的组织和力学性能

S355J2W+N耐候钢是制造高速列车转向架构架的主要钢种,本文通过拉伸、冲击、弯曲、硬度和金相等试验方法对其MAG焊焊接接头的力学性能与显微组织进行了研究。结果表明:采用G424G3Si1焊丝对S355J2W+N耐候钢进行焊接时,接头具有良好的抗拉强度、弯曲性能和低温冲击韧性;焊缝组织主要为先共析铁素体,晶内为针状铁素体和珠光体,局部有一定量的粒状贝氏体;热影响区组织主要为先共析铁素体和针状铁素体,同时存在少量的珠光体和贝氏体;母材为铁素体和珠光体。     

S355J2W耐候钢高频脉冲MAG焊对接接头的组织和性能

文中选用φ(Ar)80%+φ(CO₂)20%(M21型)的保护气体,对板厚为12 mm的地铁转向架构架用S355J2W耐候钢进行了3 mm间隙的高频脉冲MAG焊(冷焊打底)与常规脉冲MAG焊2种工况的对接焊工艺试验,研究了接头的组织和性能。研究结果表明：2种工况的对接焊接头,焊缝均成形良好,接头无裂纹、气孔等缺陷,且焊缝金属与母材金属熔合良好;接头的显微组织特征类似,为先共析铁素体(GBF)、针状铁素体(AF)和少量珠光体(P)以及少量粒状贝氏体(B_G)组织。与常规脉冲MAG焊相比,采用高频脉冲MAG焊(冷焊打底)可获得较为理想的接头组织和性能。     

S355J2W+N耐候钢高频脉冲MAG焊不同保护气体的接头组织和性能

文中选用φ(Ar)70%+φ(CO₂)30%(M31型)、φ(Ar)80%+φ(CO₂)20%(M21型)和φ(Ar)90%+φ(O₂)10%(M22型)3种形式的保护气体,对板厚为12 mm的高速铁路转向架用S355J2W+N耐候钢进行高频脉冲MAG焊,研究了对接接头的组织和性能。研究结果表明,使用这3种保护气体,焊缝均成形良好,接头无裂纹、气孔等缺陷,且焊缝金属与母材金属熔合良好;接头的显微组织特征类似,为先共析铁素体(GBF)、针状铁素体(AF)和少量珠光体(P)以及少量粒状贝氏体(B_G)组织。与其他保护气体相比,使用M31气体可获得较为理想的接头组织和性能,即焊缝和熔合区不含侧板条铁素体组织(FSP),过热区的晶粒粗化程度较小,焊缝中含更多的针状铁素体(AF)组织,焊缝、热影响区的低温(-40℃)冲击韧性较好,相比M21和M22,焊缝区冲击吸收功分别高出1.95%和54.9%,热影响区冲击吸收功分别高出1.72%和3.27%,且冲击吸收功均高于27 J,焊接接头的拉伸和弯曲性能良好。     

S355J2与S355J2W细晶粒钢焊接接头力学性能分析

对比分析S355J2+N与S355J2W+N这2种钢板焊接接头的力学性能,尤其在低温冲击功方面是否有较大区别,从而为高速动车组转向架母材选择提供科学数据.     

S355J2W+N钢不同直径焊丝的高频脉冲MAG对接焊工艺

文中采用?1.2 mm和?1.6 mm焊丝对S355J2W+N耐候钢进行高频脉冲MAG对接焊工艺试验,坡口角度为40°,使用直径1.2 mm焊丝的焊接参数为：打底焊接电流236 A,电弧电压29 V;盖面焊接电流242 A,电弧电压30.1 V,摆动角度3°,摆动速度8周/min,摆动的左右停留时间为0.3 s;使用直径1.6 mm焊丝的焊接参数为：打底焊接电流210 A,电弧电压26.5 V;盖面焊接电流249 A,电弧电压27.5 V。对焊接接头进行宏观形貌观察和分析,结果显示：焊缝成形均良好,实现了单面焊双面成形,无气孔、夹渣、裂纹等焊接缺陷,外观符合EN ISO17637∶2016/EN ISO 5817∶2014 B级质量要求。但G40X焊缝呈蘑菇状,G40Y焊缝近似三角形状,且G40Y焊缝成形系数、余高系数及焊趾角度均大于G40X的,与?1.2 mm焊丝相比,使用?1.6 mm焊丝可使根部熔深提高50%。     

调修温度对S355J2W(H)钢组织与性能的影响

采用不同的火焰调修温度(700℃、800℃、1 000℃和1 200℃)对构架材料S355J2W(H)钢进行火焰调修,研究不同火焰调修温度对其组织和性能的影响。结果表明:随着火焰调修温度的升高,S355J2W(H)钢冲击性能下降较为明显;但不同调修温度对其弯曲、拉伸性能及显微硬度影响不大;S355J2W(H)钢在700℃、800℃和1 000℃热调修时,其显微组织与未经调修的母材相当,为沿轧制方向呈带状分布的铁素体和珠光体;而在1 200℃调修时其显微组织为粗大的多边形块状铁素体和珠光体,已完全没有未经调修的母材呈带状分布的轧制特征且晶粒有所长大,故合适的热调修温度为700℃~1 000℃,不宜超过1 000℃。     

转向架用耐候钢焊接接头显微组织和力学性能

以转向架用国产耐候钢S355J2W与进口耐候钢SMA490BW为研究对象,选用进口焊丝G424M21Z与国产焊丝CHW-55CNH进行焊接,获得3种焊接接头。通过金相、硬度、拉伸和弯曲试验,对接头进行显微组织和力学性能研究。结果表明,3种接头的基本力学性均能满足标准要求;1#、2#接头焊缝区硬度比母材区高,拉伸断裂位置在母材处,为高配焊丝;3#接头焊缝区硬度和母材区相当,拉伸断裂在焊缝处,其抗拉强度比1#、2#高,但延伸率及塑性较差,为低配焊丝。     

转向架用P355NL1钢焊接接头组织及力学性能的研究

采用MAG焊接工艺对转向架用P355NL1钢板进行焊接,研究了P355NL1钢焊接接头的微观组织形貌、硬度分布及室温力学性能。试验结果表明:焊缝组织主要是粗大板条状和块状的先共析铁素体、针状铁素体以及少量珠光体;热影响区的晶粒是大小不均匀的块状铁素体、针状铁素体。焊缝区硬度值分布在192~201 HV,热影响区的硬度最高可达220HV。拉伸试样均断裂于母材处,其抗拉强度在518 MPa左右,断后伸长率平均为23.8%,P355NL1钢MAG焊接接头具有良好的强度和塑性。     

S30432钢不同焊材焊接接头组织性能

研究了超超临界锅炉用S30432钢采用不同焊材焊接接头的显微组织和力学性能。结果表明,S30432钢分别采用YT-304H、ERNiCrMo-3、ERNiCrCoMo-1焊材焊接接头经650℃×7000 h时效后,仍可保持较高的室温强度,焊缝金属均具有一定的时效脆化倾向,ERNiCrMo-3焊缝时效后的韧性最低;3种焊材焊接接头都具有优异的高温持久性能。显微组织分析认为,YT-304H焊缝强度的保持主要源于细小富Cu相和MX相的弥散分布,ERNiCrCoMo-1、ERNiCrMo-3焊缝时效后的主要强化相分别为γ’和γ″,ERNiCrMo-3焊缝晶界附近针状δ相和σ相的密集分布,导致了该焊材焊缝金属时效后冲击性能恶化。     

母材及焊丝对转向架用耐候钢焊接接头性能的影响

以高速列车转向架用耐候钢S355J2W与SMA490BW为母材,匹配G424M21Z焊丝与CHW-55CNH焊丝得到三种焊接接头。观察三种接头的显微组织,并比较三种接头的力学性能和腐蚀性能。结果显示,三种接头的焊缝区显微组织均由先共析铁素体、针状铁素体、粒状贝氏体以及珠光体组成,过热区组织粗大出现魏氏组织,正火区组织细小均匀。S355J2W母材匹配两种焊丝所得接头的拉伸断裂强度接近,且断裂位置均位于母材,而SMA490BW母材匹配CHW-55CNH焊丝所得接头拉伸断裂位置位于焊缝,且其拉伸强度明显高于另外两种接头。SMA490BW母材的腐蚀速率低于S355J2W母材。以S355J2W为母材匹配两种焊丝所得的两种接头腐蚀速率接近。以CHW-55CNH为焊丝匹配SMA490BW母材的接头低于匹配S355J2W母材所得接头。母材是影响接头耐蚀性的主要因素,而焊丝对接头的耐蚀性的影响小于母材。     

921A钢激光-MAG复合焊接头组织及性能

针对6 mm厚的921A钢板,采用激光-MAG复合焊接工艺进行对接焊试验,并对焊接接头的显微组织、硬度、拉伸性能、耐腐蚀性能等进行了分析。结果表明,采用激光-MAG复合焊工艺可获得成形连续美观的焊接接头,无未熔合、裂纹、气孔等缺陷;焊缝组织为针状铁素体、少量沿晶界析出的先共析铁素体及长条状贝氏体,热影响区组织为马氏体;焊接接头的拉伸性能和冲击性能均符合国家标准要求,焊缝强度高于母材,但塑韧性低于母材。峰值硬度在热影响区,为315 HV,焊缝硬度约为280 HV,符合最高硬度不得超过410 HV的规定。焊缝耐电化学腐蚀性能最强,母材次之,热影响区最低;激光和MAG电弧2种热源共同作用区域的组织分布更加均匀,硬度及耐腐蚀性能较激光单独作用区域有了明显改善。创新点： 采用激光-MAG复合焊实现了6 mm厚度921A钢板无缺陷对接焊的一次焊接成形。焊缝晶粒更加细化,分布更加均匀;焊缝抗拉强度、硬度、电化学腐蚀性能均高于母材,冲击吸收能量满足船级社要求。     

环境温度对Q345C钢MAG焊接头力学性能的影响

对轨道车辆材料Q345C低合金结构钢MAG焊接头进行了常温、低温(0℃、-10℃、-20℃、-30℃、-40℃)力学性能试验,包括拉伸试验、弯曲试验、冲击试验,得到力学性能随温度的变化规律,同时测量了接头硬度分布,分析了接头硬度分布规律,观察了接头金相组织。研究结果表明,随环境温度下降,其抗拉强度和屈服强度均有所提高,但伸长率和断面收缩率变化不大,冲击吸收功明显降低;Q345C焊接接头有较大的低温冷脆倾向;对在低温环境条件下服役的Q345C低合金结构钢,需重点考虑其低温冷脆倾向。     

Enhanced Fatigue Property of Welded S355J2W Steel by Forming a Gradient Nanostructured Surface Layer

Welded joints are usually characterized by microstructural and compositional inhomogeneities, which may significantly degrade their fatigue properties and result in unpredictable failures. The present work demonstrates a novel and simple method to effectively optimize the microstructure in the surface layer and promote the fatigue properties of welded specimens. By a recently developed approach—surface mechanical rolling treatment(SMRT), a gradient nanostructured surface layer is formed on welded S355 J2 W steel specimens. The mean grain size is refined to nanometer scale, and the hardness is significantly enhanced in the SMRT surface layer. Independent of the initially inhomogeneous microstructure and hardness distributions, the microstructure and hardness distributions in the surface layers are comparable on different zones of a welded specimen after SMRT with the same procedure. Consequently, fatigue property of the SMRT specimens is significantly enhanced relative to that of the as-welded specimens within the high cycle fatigue regime.     

Microstructure and mechanical properties of E36 steel joint welded by underwater wet welding

The microstructure and mechanical properties of E36 steel joint welded by underwater welding using flux-cored wire are comprehensively investigated. The welding depth, welding current and welding voltage is 4 m, 130 A and 32 V, respectively. The weld metal is ferrite which varies in size, with carbide particles distributed on it, while the microstructure of HAZ is mixture of martensite of different size and some tempered structure. The microhardness of the weld metal is 190 HV. Almost all the tensile specimens fracture in weld metal and the average tensile strength of joint is 390 MPa, which is equal to 80% that of base metal. The tensile fracture morphology of joint presents obviously the characterization of brittle fracture, which displays the features of cleavage fracture and intergranular fracture.     

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.