高锰钢辙叉与U71Mn钢轨闪光对焊接头组织分析

利用Gaas-100/580型闪光对焊机对ZGMn13高锰钢辙叉与U71Mn钢轨进行整轨焊接,分析了轨头、轨腰和轨底焊接接头拉伸、冲击、硬度分布等力学性能以及组织结构。结果表明,焊接接头各项力学性能均达到了国家铁路局有关标准要求,焊接接头高锰钢侧热影响区晶粒因动态再结晶而变得细小,钢轨钢侧热影响区为珠光体组织,没有马氏体出现;高锰钢辙叉与U71Mn钢轨采用直接闪光对焊是可行的。     

Study on microstructures and properties of preheated flash butt welded SW400 steel joints

Under the spirit of sustainable development,‘lightweight'has been gradually included into the vehicle design criterion by many manufacturers and used in automobile production. Following this trend,domestic wheel suppliers also begin to study the technology of lightweight wheel. One way to achieve this goal is improving strength grade of the steel and optimizing the structure design in the field of steel wheels. But there are a few problems in flash butt welding process in the application of high strength steel,leading to high rejection rates. SW400 steel is a special high strength wheel steel developed by Benxi Steel. Taking SW400 steel as the research material,this article studys the feasibility of improving the properties of rim flash butt welded joints by adding preheating process.     

Fatigue properties of friction stir welded butt joint and base metal of MB8 magnesium alloy

The fatigue properties of friction stir welded(FSW) butt joint and base metal of MB8 magnesium alloy were investigated.The comparative fatigue tests were carried out using EHF-EM200K2-070-1A fatigue testing machine for both FSW butt joint and base metal specimens.The fatigue fractures were observed and analyzed using a scanning electron microscope of JSM-6063 LA type.The experimental results show that the fatigue performance of the FSW butt joint of MB8 magnesium alloy is sharply decreased.The conditional fatigue limit(2 × 10~6) of base metal and welded butt joint is about77.44 MPa and 49.91 MPa,respectively.The conditional fatigue limit(2 × 10~6) of the welded butt joint is 64.45%of that of base metal.The main reasons are that the welding can lead to stress concentration in the flash area,tensile welding residual stress in the welded joint(The residual stress value was 30.5 MPa),as well as the grain size is not uniform in the heat-affected zone.The cleavage steps or quasi-cleavage patterns present on the fatigue fracture surface,the fracture type of the FSW butt joint belongs to a brittle fracture.     

Study on improving properties of welded joints of 400 MPa ultra fine grained steel by mechanical surface hardening

The welded joints of 400 MPa ultra fine grained steel in manual arc welding were treated by mechanical surface hardening. Microstructure and mechanical properties of the treated joints were compared with those of the untreated joints, based on which, primary study on the process and principle of mechanical surface hardening was carried out. The results shows that： Grain size of HAZ increases greatly and mechanical properties of welded joint decrease obviously compared with those of base martial, but grain size in the surface layer of HAZ can be refined （the grain size is about 100 nm or so） and mechanical properties of welded joints can be improved greatly by mechanical surface hardening.     

EFFECT OF REMOVING HYDROGEN FROM HEAVY RAIL STEEL BLOOMS BY STACK COOLING IN PANZHIHUA IRON AND STEEL COMPANY

The determination of dffusible hydrogen in U71Mn heavy rail steel,and hydrogen diffusivityas well as the hydrogen distribution in the cross section of blooms with stack cooling were stu-died.The results showed that,most of the hydrogen in blooms of heavv rail steel is diffusible,the hydrogen diffusivity in U71Mn rail steel blooms at room temperature is(0.85—1.02)×10~(-6)cm~2/s,after stack cooling,the hydrogen content in bloom will decrease greatly which ishelpful to form the flake-free phenomenon in the heavy rail produced by Panzhihua Iron andSteel Company.     

PRESS FORMABILITY OF YAG LASER WELDED TRIP STEEL SHEETS

The effects of YAG laser welding conditions on mechanical properties and press formability (bendability, stretch-formability and deep drawability) of high-strength transformation-induced plasticity-aided dual-phase (TDP) steel were investigated. Tensile tests and press forming tests have been conducted for laser butt welded joints between two pieces of the same steel. The tensile property and press formability were affected by the welding speed of 100 to 1100mm/min and the energy of 6 to 9J/pulse. Excellent press formability was obtained with the energy of 6J/pulse and the welding speed of 300mm/min. It was concluded that the excellent weldability of the TDP steel can be ascribed to the weld joint formation.     

Microstructure and shear strength of the brazed joint of Ti（C,N）-based cermet to steel

Firm joins were obtained between Ti(C,N)-based cermet and steel with Ag-Cu-Zn-Ni filler metal by vacuum brazing. The effects of technological parameters such as brazing temperature, holding time, and filler thickness on the shear strength of the joints were investigated. The microstructure of welded area and the reaction products of the filler metal were examined by scanning electron microscopy (SEM), metallographic microscope (OM), energy-dispersive X-ray analysis (EDS), and X-ray diffraction (XRD). The brazing temperature of 870°C, holding time of 15 min, and filler thickness of 0.4 mm are a set of optimum technological parameters, under which the maximum shear strength of the joints, 176.5 MPa, is achieved. The results of microstructure show that the wettability of the filler metal on Ti(C,N)-based cermet and steel is well. A mutual solution layer and a diffusion layer exist between the welding base materials and the filler metal.     

Effect of residual stress on the vibration failure of dissimilar steels joint

Elasto-plastic finite element method is used for the welding residual stress calculation in butt welded joint of carbon steel and stainless steel,fluctuating pressure on the ship hull induced by a prop...     

FATIGUE STRENGTH DETERMINATION OF BUTT WELDED JOINTS BY FEM

The influence of welding parameters of butt joints, made by three processes (MMA, MAGand T.I.M.E), on their geometric characteristics has been evaluated, which in turn caused a change of the fatigue strength. That fore the statistic analysis and FEM were used and a method developed in the Institute of Welding, which consist in a direct connection of parameters used during welding with the fatigue strength of joints welded by various processes. It has been proven, among others.which by using more advanced welding processes (TLM.E) the fatigue strength of welded joints can be increased in comparison to joints welded by MMA and MAG.     

Analysis of microstructure and performance of temper bead welded joints for SA508-3steel by Quenching and Tempering mode

The HAZ microstructure and performance of Quenching and Tempering mode temper bead welding and general welded joints which were made on SA508-3 steel of 60 mm thickness were compared in this article.The result shows that tempering sorbite which has excellent overall performance was obtained in both modes.The microstructure of Quenching and Tempering mode welded joints got more fine grain.Even though the hardness of tempering bead welded joints is higher than the general one,it still meets the standards which is lower than 350 HV.The impact absorbing energy of each district of tempering bead welded joints HAZ reached 170 J, which is equal to general one.     

高锰钢与钢轨钢二次闪光对焊接头的组织和冲击韧性

通过工艺试验,力学性能检验以及光镜、电镜、Ｘ射线衍射、电子探针等湿微分析手段,对高锰钢与钢轨钢二次闪光对焊接头的组织形态和冲击韧性进行了系统研究,确定了接头各区的组织形态和冲击韧性的变化情况,并提出了高锰钢与钢轨钢二次闪光对焊时改善钢轨钢焊接热影响区冲击韧性的工艺措施。研究表明,利用过渡材料来实现焊接性差、万分和物理性能相差悬殊的高锰钢与钢轨钢的焊接是一种行之有效的工艺措施。     

高锰钢和U71Mn钢在加焊接介质焊接时的接头组织

用一种焊接介质,采用等离子弧堆焊结合闪光对焊的方法将ＺＧＭｎ１３钢和Ｕ７１Ｍｎ钢加焊接介质进行焊接。结果发现ＺＧＭｎ１３钢热影响区内无碳化物析出,Ｕ７１Ｍｎ钢热影响区内无马氏体产生。中间介质为单相奥氏体组织,熔合区存在大约１０％的δ铁素体     

钢轨闪光焊接工艺与接头落锤试验分析

试验采用YHG-1200TH型移动式钢轨闪光焊机,焊接武钢60 kg/m U71Mn G热轧态钢轨.通过观察分析焊接曲线中闪平、脉动闪光、加速闪光与顶锻保压各阶段电流、电压、钢轨位移、压力等因素,结合接头落锤试验情况,调整并优选出合理工艺参数;分析焊接热输入与顶锻量间的搭配关系及接头抗落锤次数,观察断口与接头显微组织.结果表明,试验用钢轨闪光焊接热输入在11.5~12.5 MJ之间且顶锻量在15~16 mm之间时,接头抗落锤情况较集中,质量稳定性好;合理工艺参数焊接且经落锤检验合格的接头断口无明显缺陷,焊缝及热影响区组织为珠光体和少量铁素体,未见马氏体、贝氏体组织或其它缺陷.     

正火处理对贝氏体钢辙叉铝热焊接头性能和组织的影响

利用Gleeble-3500试验机模拟了贝氏体钢辙叉铝热焊热影响区各位置的热循环过程,研究了焊后正火工艺对热影响区性能与组织的影响. 热模拟结果表明,铝热焊后对接头进行900 ℃的正火处理,可以使焊接热影响区重新转变为贝氏体组织,提高了冲击韧性并改善硬度分布均匀性,强度值也达到或接近母材水平. 根据热模拟试验结果,对贝氏体钢辙叉和U75V钢轨进行了实际的铝热焊接. 结果表明,900 ℃火焰加热正火处理后,焊缝及热影响区软化区的硬度和抗拉强度值均有明显提高,这对提高焊接接头的使用寿命有重要作用.     

中海拔地区钢轨焊接工艺及质量对比

以包钢U75V热处理钢轨焊接为对象,依据焊接接头型式检验结果,对比研究兰州铁路局中海拔地区基地闪光焊、现场移动式闪光焊、移动式气压焊及铝热焊接头性能。结果表明:基地焊接接头综合性能最佳,现场移动式闪光焊和移动式气压焊接头综合性能相近,铝热焊接头性能最差。     

Flux shielded arc butt welding of concrete reinforcing steel

Abstract

The present paper reports on a new variant of flux shielded arc butt welding without the addition of a filler material, applied to steel bars for concrete reinforcement. The welding process is described, including the arc ignition and forcing together of the workpieces, via the application of a mechanical force, to form an upset. A new portable machine is described, using which it is possible to apply flux shielded arc welding on site. Experiments were carried out, from which optimum welding parameters such as welding current, weld time, and upsetting force were found. The strength properties of the welded joints obtained were determined via mechanical testing, i.e. a bend test, a tensile strength test, and an impact toughness test. Macroscopic sections of the welded joints were also produced. A quality analysis of the butt welded joints showed that the mechanical properties of the joints were equivalent or even superior to the properties of the parent metal.     

不同热处理制度下1Cr11Ni2W2MoV闪光对焊接头的组织与性能

针对1Cr11Ni2W2MoV不锈钢开展闪光对焊试验,研究不同焊后热处理制度对其焊接接头组织和力学性能的影响。结果表明:采用闪光对焊方法焊接1Cr11Ni2W2MoV,能够获得优质的焊接接头。1Cr11Ni2W2MoV闪光焊焊态下焊缝组织为马氏体和少量的δ铁素体组织,焊接接头具有较好的拉伸性能,但塑性和韧性较差。经过淬火+回火热处理后组织表现为回火索氏体组织,焊接接头的抗拉强度、塑性和韧性等性能均得到改善。在1000℃油淬+570℃回火状态下,焊接接头具有良好的综合力学性能。     

Fatigue crack growth of bainitic rail steel welds

Abstract

The objective of the present study is to develop and evaluate novel weld repairs of bainitic rail steel defects, such as detail fracture, induced by in service loading. Slots were machined in the bainitic rail steel to simulate the removal of service defects. Multipass gas metal arc welding was used to fill and repair the slots. Three-point bend tests of the parent and welded steels revealed that the flexural weld efficiency was 75%. Fatigue crack propagation (FCP) tests were performed on specimens from the welded joints and compared with the parent materials to determine the mechanical integrity of the slot repairs. The fatigue lifetime and FCP kinetics were similar for the parent and slot welded bainitic steels, indicating similar resistance to FCP. The fatigue fracture surface morphology of the parent and welded bainitic rail steels both revealed mostly a ductile fracture mechanism in all the three FCP stages.     

400MPa级超细晶粒钢筋闪光对焊的组织及性能

400MPa级超细晶粒钢筋是通过形变诱导形核及控轧控冷技术，生成微米级铁素体，从而提高钢的强度和韧性。本文结合焊接接头的微观金相观察和宏观性能试验，对400MPa级超细晶粒钢闪光焊的适应性进行了研究。钢筋闪光焊接头具有良好的力学性能，接头HAZ不存在明显软化。只在焊缝心部区域出现局部软化，但少许的局部软化并不影响整个接头的性能。闪光对焊对于400MPa级超细晶粒钢筋的焊接具有良好的适应性，可得到具有优良性能的焊接接头。     

等离子弧焊Q345B和430不锈钢异种接头的微观组织与性能

摘要： 采用等离子弧焊对3 mm厚的Q345低合金钢与430不锈钢进行异种钢焊接,并对接头微观组织、力学性能及耐腐蚀性能进行了研究。结果表明,当转弧电流为100 A时,等离子弧焊Q345B/430异种钢接头的焊缝组织为均匀分布的马氏体及针状铁素体,焊接接头综合性能优良。随着电流的增大,焊缝组织转变为粗大板条马氏体及铁素体。两侧热影响区组织均发生一定程度的粗化,且Q345B侧热影响区出现魏氏组织。焊接接头于焊缝处显微硬度最大,不同转弧电流条件下异种钢显微硬度分布趋势大致相同。不同转弧电流下,焊接接头抗拉强度均与430不锈钢相近,且均断裂在靠近焊缝的430母材侧,转弧电流为100 A时接头抗拉强度最大值427 MPa。焊接接头的耐腐蚀性能与焊接电流呈负相关趋势。 创新点： 试验结果为铁素体低合金钢与铁素体不锈钢异种钢接头的应用提供了工艺数据与支撑。