超声辅助水下湿法焊接工艺

水下湿法焊接过程电弧不稳定,常存在熄弧、焊缝成形不均匀等问题.针对这一问题,提出了超声辅助水下湿法焊接方法,其原理是将功率超声振动与常规水下湿法焊接相结合,通过超声振动作用改善焊接电弧稳定性、焊缝成形,进而提高水下焊接接头质量.超声辅助水下湿法焊接堆焊对比试验结果表明,超声辅助水下湿法焊接显著改善了焊缝成形,能够获得尺寸均一连续的焊缝;焊接过程稳定性提高,熄弧率明显减小,熔深增大,余高减小,焊缝中心区域的显微硬度减小.     

水下湿法焊条电弧焊接过程稳定性评价

焊接电参数(电弧电压、焊接电流)包含着丰富的焊接过程信息.针对水下湿法焊条电弧焊工艺,在不同焊接工艺条件(不同水深、不同焊条)时在线采集焊接电弧电压瞬时值,然后对其进行统计处理.利用电弧电压标准差σU以及电弧电压瞬时值与电弧电压平均值差值H的频率对比和焊接过程稳定性指数W相结合的方式,对水下湿法焊条电弧焊接过程的稳定性进行直观分析和定量评价.结果表明,利用W可以很好地识别不同焊接过程的稳定性,为水下焊接工艺稳定控制提供了新的方法,具有重要的理论意义.     

焊缝余高变异系数在水下湿法焊接质量评估过程中的应用

针对水下湿法焊接质量评定中缺乏简便、客观的评价指标的现状,提出利用焊缝余高的变异系数表征焊接质量. 该指标具有支持定量分析客观性强、步骤简单易操作等优点. 余高变异系数越大,焊缝外观成形均匀性越差,焊接质量越低;反之,焊缝越平滑、美观,焊接质量越好. 为验证该指标的准确性,设计了相关的工艺试验. 依据脉冲电流对焊接过程稳定性的影响,开展不同脉冲频率条件下焊接. 鉴于送丝方式对焊接过程影响较大,利用焊缝余高变异系数分析送丝方式对水下湿法药芯焊丝焊接过程稳定性研究. 结果表明,余高变异系数评价结果与焊接质量相关度较高. 焊接过程中采用X射线高速成像技术,从焊接过程稳定性与熔滴过渡类型等方面深入分析了焊接过程对余高变异系数的影响,进一步验证了该指标的可靠性.     

水下湿法焊接等离子成分计算

水下湿法焊接所产生的电弧是在带电离子气体的气泡中形成的,结合前人对水下湿法焊接气泡成分的测定,分析了水下湿法焊接气泡中气体的主要解离和电离过程,对局部热力学平衡态下的不同水压、不同温度的水下电弧成分采用potapov模型进行了计算,其主要理论依据为Dalton分压定律、质量作用定律、电荷准中性条件和化学计量平衡条件.结果表明,随着水压由0.101 3 MPa变化到1.013 MPa再到10.13 MPa,离子体内H+,O,C,O+,C+的数密度呈现逐渐增加的趋势,同时电子数密度和离子体密度也跟随增加.而离子体总体平均电离度不受水压的影响.为进一步计算水下湿法焊接电弧的输运系数和水下电弧的仿真打下了基础.     

DH36钢湿法焊条多层多道焊海试结果分析

通过对潜水员焊工的培训，成功实现了不同接头形式的水下湿法手工多层多道焊，并且在渤海海域的11 ，22 m两个水深分别进行了对接接头平焊、搭接接头横焊及立焊和T形接头立焊及船形位置焊的焊接试验.结果表明，在两种水深的对接接头和搭接接头中都未发现夹渣、气孔及未熔合等缺陷，并且两种水深的对接接头和搭接接头在各项力学性能指标上都满足AWS D3.6 M:2010关于B级接头的要求.与11 m水深的焊缝相比，22 m水深的焊缝柱状晶区的针状铁素体减少，块状铁素体明显增多.两种水深接头的热影响区粗晶区组织差异不大，主要由板条状马氏体组成.     

水下湿法焊接裂纹敏感性试验

潜水焊工在水深2m的水池里,使用水下专用焊条进行EH36和16Mn试板湿法焊接试验。依据GB4675.1-1984斜Y型坡口焊接裂纹实验方法,评价水下湿法焊接接头的冷裂纹敏感性。小铁研实验表明,水下湿法焊接接头的抗裂性很差,裂纹率基本为100%。裂纹是从根部产生,沿着熔合线向焊缝表面或者焊缝表面熔合线区域扩展。同时提出了水下湿法焊接冷裂纹防止的一些建议。     

Study of pores produced in underwater wet welding

0 IntroductionPore is one of the main defects produced in wet weld-ing, especially in deep water. The integrity, ductility,and strength of a wet weld will be reduced by the presenceof pores. It is very necessary to study the pore formation toimprove the quality of underwater wet welds and to ensurethe security and dependability of the welded structures.Underwater wet welding offers advantages such ashigh speed, good versatility, and cost effectiveness. It ischaracterized by lower visibility, …     

水下湿法手工自蔓延焊接技术

基于自蔓延高温合成技术（SHS技术）和湿法电弧焊原理,研究了一种用于水下金属结构应急维修的新型焊接方法—水下湿法手工自蔓延焊接技术.通过焊条结构设计、焊药设计等,研制了水下燃烧型焊条,进行了焊接试验,对接头组织和性能进行了分析.结果表明,该技术可在无电、无气、无其它设备的条件下实现水下金属构件的湿法焊接,单面焊双面成形,接头抗拉强度达267 MPa,冲击吸收能量13.8 J;SEM和EDS分析表明,焊缝金属为以α-Cu固溶体为基体、有大量块状富铁第二相析出的高铁铜合金,熔合区的成分和组织与焊缝第二相基本相同,焊缝合金与熔融母材交互结晶,形成了梯度熔焊连接;拉伸断裂发生在焊缝或熔合区,断口有大量韧窝,属韧性断裂.     

水下湿法自保护药芯焊丝

开发了一种新型水下湿法自保护药芯焊丝,采用模拟压力舱以及自动焊接系统,在30米模拟水深的条件下进行了焊接试验,焊接结果表明焊接过程稳定,成形良好.按照美国焊接协会水下焊接标准（ANSI/AWS D3.6 1999）对获得的焊接接头的抗拉性能、弯曲性能、硬度以及冲击韧性等进行了研究.拉伸试验试件断裂位置位于母材区,弯曲试验试件弯曲180°没有发生断裂,并无明显裂纹产生,0℃冲击韧性达到30.25J/cm2.研究结果表明,自主研发的水下湿法自保护药芯焊丝可满足CCSE36等级钢的水下30米水深的焊接性能要求.     

水下湿法焊接研究进展

为研究深水湿法焊接电弧等离子体介质击穿机制,建立了高压水下湿法焊接试验平台,获取40 m水深电弧引弧阶段光谱图,基于PIC-MCC方法建立40 m水深湿法焊接电弧击穿放电三维数值模型并对其进行分析,将光谱诊断电弧等离子体温度、电子数密度和数值模型分析得到的结果进行对比,验证了模型的合理性与正确性. 根据电弧光谱得到的电弧等离子体的主成分,从微观粒子角度对高压水下湿法焊接电弧等离子体动态演变过程展开研究,获得等离子体动态分布、粒子数目、电弧等离子体温度及电子数密度变化.结果表明,电子与背景成分水分子发生电离碰撞主要生成H⁺,OH⁺和O⁺,且OH⁺数目增长速度最快, H⁺次之,O⁺最后,在粒子数目上OH⁺远远大于H⁺和O⁺数目;电子与背景气体碰撞过程中发生了能量转移,运动到极板介质层的电子动能减小,电子与极板介质层电离碰撞反应弱化,直至达到饱和.     

A7075搅拌摩擦焊疲劳裂纹扩展速率试验分析

对航空用铝合金A7075-T651的搅拌摩擦焊接头的母材、焊核区和热影响区的疲劳裂纹扩展速率（da／dN）进行了试验研究。疲劳裂纹扩展试验采用CT（紧凑拉伸）试样,在810 Material Test System试验机上进行。用递增多项式法求得疲劳裂纹扩展速率（da／dN）和（△K）,并分别将母材、焊核区和热影响区同一组试样的（da／dN）和（△K）数据点合在一起进行了整体回归分析。试验中得到了以Paris公式表达的铝合金A7075-T651母材、焊核区、热影响区da／dN与△K的关系式。结果表明,热影响区疲劳裂纹扩展速率高于母材和焊核区,是该合金搅拌摩擦焊接头最薄弱的区域。     

水深和流速对水下湿法焊接热过程影响的数值模拟

水下电弧在高压和强烈冷却作用的环境下,其弧压、形态和能量密度都发生了改变,工件的换热条件更发生了显著的变化.文中考虑水下压力对电弧的压缩和水环境中工件换热速度的提高,进行一定的参数假设,建立了湿法熔化极气体保护焊接热过程的数值分析模型,得出了不同水深和不同水流速度下的工件热循环曲线、熔池形状等典型数据.模拟结果表明,随水深增加,熔池的深度增加而宽度减小,各等温线的形状也逐步变得狭窄而且更深;随工件表面水流速度增大,熔池变小,等温面所笼罩的体积也显著减小.     

Thermodynamic considerations of pore formation and hydrostatic pressure during underwater wet welding

The pore and crack formations in the weld bead during underwater wet welding are the main cause of failure to reach the required mechanical properties of the weld metal. These defects are closely associated with the decomposition of the water molecule under electric arc conditions. In this paper, the thermodynamic calculations of the complex process of the water decomposition under the conditions of high electric arc temperatures at a pressure of 1 atm of steam are discussed. The values of the partial pressures of the five main products of the vaporizations and decomposition of the water (H₂O_(g), H₂, O₂, H and O) are calculated for temperatures between 1870 and 4000 K. Due to the fact that atomic hydrogen is mainly responsible for pore formation in the weld metal, its partial pressure as a function of partial pressures of atomic oxygen and steam (water vapour) is expressed. Hydrogen solubility values in the liquid metal under the conditions of underwater wet welding at depths of 50 and 100 m, and a comparison between the thermodynamic calculation and porosity measurement results at depths of 50 and 100 m, are presented.     

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.     

水下湿法焊接浅水环境下FCAW电弧静特性

为了研究水下湿法焊接浅水环境下FCAW电弧特性,在自制的能够模拟不同水深的高压舱焊接系统内进行了一系列试验.并用编写的Lab View程序在采集到的电弧电压和焊接电流数据中选取焊接时较稳定的数据绘制电弧静特性曲线,对比分析了在相同的焊接工艺参数下常压空气中平板工件焊接和在浅水环境下水下湿法FCAW的电弧静特性,同时研究...     

Research on porosity of underwater wet FCAW duplex stainless steel

To study the influence laws of welding parameters on weld porosity, underwater wet flux-cored arc welding ( FCAW) duplex stainless steel S32101 was carried out in a hyperbaric chamber, and the second-order multiple regression equation was established. The interactive effects of welding parameters on the porosity were analyzed by the three dimensional response surfaces and the contour plots. The results present that the interaction effect between water depth and voltage on the porosity is the most significant. Theoretically, a non-pores weld bead can be gained by reasonably matching these parameters with water depth less than 10 m. Always, the weld porosity reaches its peak value with a 7 mm/ s welding speed.     

Microstructure and mechanical properties of dissimilar welds between 16Mn and 304L in underwater wet welding

Dissimilar joint between 304L austenitic stainless steel and low-alloy steel 16Mn was underwater wet welded using self-shielded nickel-based tubular wire. Microstructure, mechanical properties and corrosion behaviour of dissimilar welded joints were discussed. Ni-based weld metal was fully austenitic with well-developed columnar sub-grains. Type II boundary existed between Ni-based weld metal and ferritic base metal in underwater welds similar to that in air welds. Major alloying elements distributed non-uniformly across the austenitic weld metal/16Mn interface. Maximum hardness values in wet welding appeared in a coarse-grained heat-affected zone at the 16Mn side, which possessed very low impact toughness. Underwater Ni-based welded joints fractured at Ni-based weld metal under tensile test. Ni-based weld metal had favourable corrosion resistance similar to 304L base metal.     

水下管道焊接技术的研究现状及发展趋势

水下管道的焊接由于受水下环境韵影响,焊接方法与焊接设备都较陆地上的复杂得多,它具有可见度差、焊缝舍氢量高、冷却速度快、电弧电压高和连续作业困难等特点。综述了水下管道焊接技术研究与应用的最新进展,并就水下．焊接技术的发展趋势提出了看法。