对接焊缝金属和熔敷金属冲击吸收功差异的探讨

针对对接焊缝金属和熔敷金属之间的冲击吸收功差异,分别从材料的韧-脆转变温度、成分、组织以及断口方面进行了探讨.结果表明,对接焊缝金属及熔敷金属的韧-脆转变行为存在较大的差异,相同温度下对接焊缝金属的冲击吸收功低于熔敷金属.这主要是因为二者所含的合金元素C和Mn有显著的不同,即元素C含量的增加以及元素Mn含量的减小均提高了对接焊缝金属的韧-脆转变温度;焊道布置的不同,致使对接焊缝金属中的屈氏体含量高于熔敷金属中的含量,从而使得对接焊缝金属容易形成裂纹;并且从断口照片可以看出对接焊缝金属的裂纹稳定扩展的距离相对较小.     

核用镍基焊缝缺陷控制与焊材研制

镍基焊材在核电主设备制备中有着重要的应用,镍基焊材的性能很大程度上决定了核电设备的服役寿命。通过分析镍基焊缝金属焊接过程中常出现的失塑裂纹和点状夹杂两类焊接缺陷,设计并制备了不同Nb、Mo含量的镍基合金焊丝。结果表明,Ti会促进镍基焊缝金属中点状夹杂的出现;随着Nb、Mo含量的增加,镍基合金焊缝金属的室温强度逐渐增加,且焊缝金属的塑性得到大幅提升。Nb、Mo元素的添加,有效地改善了镍基焊缝金属中失塑裂纹与点状夹杂缺陷。通过调整成分获得了满足核电主设备使用要求的镍基合金焊丝。     

Ti和B含量对X100管线钢用埋弧焊熔敷金属冲击韧性的影响

研究了不同Ti和B元素含量对自主研发的X100管线钢用埋弧焊焊丝和高碱度焊剂匹配焊接所得熔敷金属冲击性能的影响。结果表明,B元素含量小于0.0006%、Ti元素含量小于0.015%时,增加Ti和B元素,都有助于提高熔敷金属的冲击韧性;在B元素含量为0.0006%、Ti元素含量为0.015%时,熔敷金属冲击吸收能量-60℃达到最大值(101J)。B元素含量在0.0006%～0.001%之间,随着Ti,B元素含量的增加,熔敷金属冲击韧性都下降;B元素含量超过0.001%后,随着Ti含量的增加,熔敷金属冲击韧性快速降低。     

高速列车用富氩混合气体保护焊丝的研制

通过试验分析了富氩混合气体保护焊条件下焊丝中各元素含量对焊丝及焊缝金属性能的影响.结果表明:随着焊丝中C,Si,Mn含量的增加,焊丝及焊缝金属的强度均提高,焊缝金属的伸长率和冲击吸收功降低.考虑焊丝的制造工艺、使用性能以及CRH5高速列车转向架对焊接接头服役性能的要求,通过调整焊丝成分得到了符合CRH5高速列车使用要求的焊接接头性能.     

Al和Mg元素对吉帕级熔敷金属组织和力学性能的影响

针对吉帕级熔敷金属韧性不足的现状,设计了4组焊丝,研究了Al,Mg元素对金属粉芯焊丝熔敷金属组织和力学性能的影响. 采用扫描电子显微镜对熔敷金属的显微组织进行了表征,通过力学性能测试表征了熔敷金属的力学性能. 结果表明,熔敷金属主要由马氏体、贝氏体构成. 随着熔敷金属中Al,Mg元素的添加量由0Al-0Mg增加至0.3Al-0.9Mg,其氧含量由0.0308%降为0.0143%,聚合贝氏体含量减少,板条马氏体含量增加. 夹杂物由传统的以Fe,Al,Si,Mn等元素的氧化物转变为以Al,Mg氧化物为主的球形细小夹杂物(MgO·Al₂O₃). 0.3Al-0.9Mg组与0Al-0Mg组相比较,夹杂物的平均尺寸降低了0.13 μm,抗拉强度增加了152 MPa,冲击吸收能量增加了11 J (?20 ℃).     

B元素对药芯焊丝焊缝金属针状铁素体形成的影响

利用金相组织观察、冲击试验和热膨胀试验,研究了B元素含量变化对高强钢药芯焊丝焊缝金属中针状铁素体形成的影响,得到了不同试验温度下焊缝金属冲击吸收功. 结合透射电镜分析和分级淬火试验从热力学和动力学的角度对B元素影响机理进行了分析. 结果表明,焊缝金属组织晶界中含有自由状态的B元素具有抑制晶界铁素体形核利于针状铁素体生成的作用;N元素含量增加会降低晶界B元素含量,并提高奥氏体向铁素体转变的温度,减少针状铁素体含量;针状铁素体是在以Ti元素和Mn元素的氧化物为核心,以Cu元素和Mn元素的硫化物为外层,以BN为过渡层的复杂结构上形核并长大的;针状铁素体含量的增加有利于提高焊缝金属冲击吸收功,–60 ℃冲击吸收功最大为70 J.     

Ti含量对熔敷金属力学性能及焊缝中心显微组织的影响

文中以采用了Ti-B系的500 MPa级药芯焊丝YCJ501-1为对象,研究了Ti含量的变化对熔敷金属力学性能和焊缝中心显微组织的影响。研究表明,Ti含量偏低时,焊缝中心易形成网状的先共析铁素体,对冲击吸收功产生不良影响;当Ti含量偏高时,焊缝中心形成大量的针状铁素体和极少量先共析铁素体,导致焊缝金属塑性变差。当Ti含量合适时,熔敷金属的冲击韧性和塑性良好。     

Ti和B含量对H08C埋弧焊熔敷金属冲击性能的影响

研究了不同 Ti和B含量对H08C焊丝配合自主研发的高碱度焊剂所得熔敷金属冲击性能的影响,发现随着熔敷金属中Ti和B含量增加,熔敷金属的冲击性能都降低,尤其B,对冲击性能的不利影响远大于Ti.     

Al对金红石型药芯焊丝熔敷金属组织性能的影响

通过在金红石型药芯焊丝中加入不同含量的铝铁,研究了Al对熔敷金属组织及力学性能的影响,并对夹杂物的数量和成分进行了分析。随着焊丝中铝铁含量的增加,Al对促进其他脱氧元素过渡的作用不明显,熔敷金属强度基本保持不变,韧性变化显著。微观组织及夹杂物分析发现,当Al以合金元素的形式固溶于基体中时,促进晶界块状铁素体的析出,使韧性恶化;当Al以脱氧剂的作用与Ti、Mn等元素联合脱氧时,可以优化夹杂物尺寸,增大原奥氏体晶粒尺寸,促进针状铁素体的形核,使熔敷金属获得良好的韧性。     

960 MPa高强钢金属粉芯型药芯焊丝焊缝金属韧化机理

针对960 MPa高强钢研制了以Mn,Ni,Mo和Cr元素为主要合金体系,以Ti,B,Nb和Al元素为微合金元素的金属粉芯型药芯焊丝. 采用熔化极气体保护焊进行施焊,通过拉伸试验和低温冲击试验等方法对接头力学性能进行了测试,结合金相组织观察、断口扫描、能谱分析和透射电镜观察等对合金元素的作用机理进行了分析. 结果表明,接头抗拉强度平均值为952.24 MPa,-20 ℃焊缝低温冲击吸收功平均值为70 J,研制的焊丝在保证接头强度的同时有效改善了焊缝金属的低温冲击吸收功. 在药芯成分中,主要合金元素起固溶强化和弥散强化作用,微合金元素通过细化晶粒、抑制块状铁素体析出和增加针状铁素体形核率等方式改善低温冲击性能.     

Influence of filler wire composition on weld microstructures of a 444 ferritic stainless steel grade

Seven compositions of metal cored filler wires for gas metal arc welding (GMAW), containing the same weight percent of chromium (Cr) and molybdenum (Mo) as 444 steel, but with different titanium (Ti) and niobium (Nb) contents were investigated. Experimental results pointed out that the filler wire Ti content required to be twice time more than the amount expected in the deposited metal. This was due to the low Ti transfer ratio during arc welding. Moreover, Ti increased the wetting angle and promoted penetration. It was supposed that Ti affected the weld pool surface tension what led to inward Marangoni convection.Columnar to equiaxed grain transition (CET) was also promoted thanks to the precipitation in the weld pool of Ti rich refractory compounds which act as heterogeneous nucleation sites for equiaxed grains. A minimum 0.3% Ti was required in the filler wire to form a completely equiaxed grain structure in the fusion zone. Niobium in the filler wire did not seem to have any effect on penetration, wetting and grain structure of the fusion zone.     

焊丝成分对高速列车转向架焊接接头性能的影响

采用富氩基CO2焊工艺对高速列车转向架用S355J2G3钢板进行焊接,分析了焊丝中C,Mn,Si和Nb元素在焊接过程中的烧损及过渡规律,并研究了焊丝中C,Mn,Si和Nb元素含量变化对焊接接头力学性能的影响.结果表明,在富氩基CO2保护焊工艺中,Mn,Si元素会产生烧损,合理提高焊丝中Mn,Si元素含量,才能获得与母材相匹配的焊接接头性能,C元素的烧损规律与焊丝中各元素的原始含量有关.随着焊丝中C,Si,Mn元素含量的增加,焊缝金属的强度增加,断后伸长率降低.Nb元素的加入会显著提高焊缝金属的强度,但同时会恶化其塑性和韧性,因此应严格控制焊丝中的Nb元素含量.     

母材成分对X80管道环焊接头冲击性能的影响

管线铺设过程中采用自保护药芯焊丝半自动焊焊接工艺,研究母材中Nb含量对X80管线钢环焊接头冲击韧性的影响。试验结果表明:母材的化学成分对焊缝金属的成分有影响,母材中较高的Nb含量经焊接热循环后过渡到焊缝金属中,促进了焊缝金属中M/A组元的形成和含量的增加,沿晶界分布的M/A组元降低了焊缝金属的冲击吸收功,影响了焊缝金属的冲击韧性及稳定性。经过优化焊接工艺参数,控制焊态焊缝金属的组织形貌、M/A含量及其分布,可保障X80自保护药芯焊丝焊缝金属的冲击韧性控制在较高且相对稳定的水平,但工艺窗口较窄。     

Effects of flux composition on the element transfer and mechanical properties of weld metal in submerged arc welding

Submerged arc welding was performed using metal-cored wires and fluxes with different compositions. The effects of wire/flux combination on the chemical composition, tensile strength, and impact toughness of the weld metal were investigated and interpreted in terms of element transfer between the slag and the weld metal, i.e., Δ quantity. Both carbon and manganese show negative Δ quantity in most combinations, indicating the transfer of the elements from the weld metal to the slag during welding. The amount of transfer, however, is different depending on the flux composition. More basic fluxes yield less negative Δ C and Δ Mn through the reduction of oxygen content in the weld metal and presumably higher Mn activity in the slag, respectively. The transfer of silicon, however, is influenced by Al₂O₃, TiO₂ and ZrO₂ contents in the flux. Δ Si becomes less negative and reaches a positive value of 0.044 as the oxides contents increase. This is because Al, Ti, and Zr could replace Si in the SiO₂ network, leaving more Si free to transfer from the slag to the weld metal. Accordingly, the Pcm index of weld metals calculated from chemical compositions varies from 0.153 to 0.196 depending on the wire/flux combination, and it almost has a linear relationship with the tensile strength of the weld metal.     

TIG焊对低合金钢焊缝金属元素分布状态的影响

采用TIG焊,选取两种成分相近的焊丝,制备了两组低合金钢焊接接头.通过焊材的EDS成分分析、焊缝金属XRF元素分析以及元素分布状态图等手段,研究了焊材及母材的合金元素在焊缝金属中的存在状态和分布特征.结果表明,锰在ER307Si焊缝中较高,镍、铬在ER308LSi焊缝中较高,硅在两组焊缝金属中相差不大;铬、镍、锰、硅在ER307Si焊缝中的起弧处含量较高,在ER308LSi焊缝中的中间处含量较高;起弧处元素分布较均匀,熔合线附近分布较稀疏;焊缝中间位置Ni元素分布较疏,含量较低;收弧处各元素分布不均.     

Effect of cooling rate on microstructure and properties of microalloyed HSLA steel weld metals

Abstract

Two high strength Nb/Ti microalloyed S690QL steels were welded with identical filler material, varying welding parameters to obtain three cooling rates: slow, medium and fast cooling. As cooling rate increased, the predominantly acicular ferrite in Nb weld metal (WM) is substituted by bainite, with a consequence of obvious hardness increase, but in Ti WM, no great variation of acicular ferrite at all cooling rates contributed to little increment of hardness. The transition between bainite and acicular ferrite has been analysed from the point view of inclusions characteristics, chemical composition and cooling rate. Excellent Charpy toughness at 233?K was obtained with acicular ferrite as predominantly microstructure. Even with bainite weld of high hardness, the toughness was nearly enough to fulfill the minimal requirements. WM for Ti steel showed to be markedly less sensitive to the variations of cooling rate than that for Nb steel.     

A flux-core wire for hardfacing sealing surfaces of stop valves

A new flux-cored wire producing the deposited metal of high-chromium steel of the Fe–Cr–Ni–Mo–Mn–Si–Nb–Ti–B alloying system is described. The structure of the deposited metal and the composition of the hardening phases are determined. The role of borides in increasing the wear resistance and stability of the properties of the metal in hardfacing is analysed.     

Mechanical properties of 422 stainless steel repaired via wire feed laser welding

Abstract

Laser welding with filler wire additions could be used in restoration of components that are of high cost or sometimes difficult to procure, such as steam turbine blades in fossil fuel power plants. In the present work, machined V groove specimens were employed to simulate laser repair of Carpenter 636 stainless steel (SS), which has a similar composition to a blade material, type 422 SS. Before repair welding, a heat treatment procedure including solution and temper treatments of the specimens was carried out according to the mechanical and microstructural analyses of a used blade after 20 years service at about 540° C. Tensile, impact, and fatigue crack growth tests of weld repairs using 410 SS filler wire were conducted. The weld repairs exhibited an impact toughness similar to that of the base metal and a lower fatigue crack growth rate than the base metal. However, the lower hardness associated with 410 SS filler metal led to tensile fracture in the weld metal of repaired specimens. Accordingly, the use of 410 SS filler metal for repair welding type 422 SS components should be limited to regions under low stress.