强电场对摩擦焊接头组织与性能的影响

为提高摩擦焊缝金属的变形能力，采用外加电场考察了摩擦焊缝金属的电塑性效应，利用金属组织观察、显微硬度测试及抗拉试验，定量分析了外加强电场对LY12铝合金摩擦焊缝组织与力学性能的影响，结果表明：外加强电场使焊缝金属组织轴向分布梯度减小，等轴性提高；不同焊接压力时，强电场使焊接接头的动态再结晶区宽度有不同程度的增大；在中等摩擦压力作用下，使近轴心线处的动态再结晶区宽度趋干均匀；此外，外加电场使接头焊合区硬度增加，并使焊接接头的硬度分布趋干均匀；采用强规范施焊时，外加电场提高了焊接接头的抗拉强度。     

不锈钢与渗碳钢惯性摩擦焊接头的组织与性能

目的 研究0Cr18Ni12Mo2Ti不锈钢与20CrMnMo渗碳钢的惯性摩擦焊焊接接头的组织与力学性能。方法 通过金相、能谱分析、显微硬度、拉伸试验对焊接接头进行组织与力学性能分析。结果 焊接试样上0Cr18Ni12Mo2Ti不锈钢一侧飞边尺寸比20CrMnMo渗碳钢一侧飞边小;焊接接头熔合区仅为50 μm,熔合线附近元素扩散层很窄,其中0Cr18Ni12Mo2Ti不锈钢仍为奥氏体组织,20CrMnMo钢组织由铁素体与珠光体转变为马氏体与索氏体,20CrMnMo一侧热力影响区组织为细小的片状珠光体与铁素体;焊缝区的显微硬度为358HV,高于2种母材;焊接接头抗拉强度大于590 MPa,断后伸长率大于32%,断裂位置均在0Cr18Ni12Mo2Ti不锈钢母材一侧。结论 采用惯性摩擦焊工艺可实现不锈钢与渗碳钢的高强连接。     

TLP扩散焊过程中近表面区域元素贫化控制研究

为了控制TLP扩散焊过程中近表面区域元素贫化,通过对IC10合金TLP扩散焊不同充氩分压量实验,测试分析充氩分压对表面Cr元素含量的影响和对焊接组织性能的影响。实验结果表明:TLP扩散焊真空充氩分压能控制表面Cr元素贫化层厚度在4μm左右,能有效控制TLP扩散焊过程中的表面元素贫化问题;焊接保温20min后开始分压,对焊接接头组织性能无不利影响;焊后进行热处理,能提高焊接强度,恢复基体组织性能。添加涂层后,经过扩散处理,贫Cr层消失。     

旋转摩擦焊接头焊合机理研究

以Q235低碳钢为母材,研究了摩擦时间和顶锻压力对旋转摩擦焊接头焊合率和冶金质量的影响规律并分析了接头焊合机理。结果表明,不同焊接参数下已焊合区域的拉伸强度基本相同且均大于或等于母材强度,焊接参数影响的只是接头焊合率(焊合率:接头横截面焊缝焊合部分长度与总长度之比),因此提出将焊合率作为焊接质量的评价标准。进一步研究表明,在其他参数不变的情况下,焊合率随顶锻压力的增大而增大,但增大速率逐渐趋缓,当顶锻压力达到某临界值后,焊合率达到100%,对所需临界压力进行了分析并得出了其计算方法;随着摩擦时间的增加,轴向缩短量增大,焊合率减小,焊接界面温度升高,高温区变宽,焊后再结晶区域加宽且晶粒尺寸变大。近缝区组织呈流线状,且晶粒大小不均匀。最终得出,大顶锻压力,短摩擦时间有助于提高焊合率,减小晶粒尺寸小,提升接头整体质量。     

镍铁基高温合金摩擦焊接接头在煤灰/烟气中的腐蚀行为

以HT700惯性摩擦焊焊接接头为研究对象,从腐蚀动力学、氧化膜相组成及微观结构方面研究了不同组织状态的焊接接头在750℃煤灰/烟气中的腐蚀行为。结果表明,焊接接头主要腐蚀产物基本一致,为富Fe、Cr的氧化物,另有少量Al_2O_3、TiO_2及Ti的内硫化腐蚀产物。焊态焊接接头晶粒细小,Cr元素可以更加及时地扩散至焊接接头表面,氧化初期可以快速形成氧化膜,延缓腐蚀;焊后热处理态焊接接头Cr元素扩散速率低,形成连续内氧化层的时间晚于焊态组织,导致氧化膜厚度更大。两种组织状态的焊接接头不同区域的腐蚀行为均呈现晶粒越小、氧化膜越薄的特征,焊缝熔合线具有最薄的氧化膜厚度。     

摩擦压力对Super304H/T92摩擦焊焊接接头性能的影响

利用连续驱动摩擦焊技术焊接Super304H和T92钢管,焊接接头具有良好的显微组织和力学性能。考察摩擦压力对焊接接头显微组织和力学性能的影响,研究表明:随着摩擦压力增加,焊合区和热影响区晶粒尺寸没有明显变化,热影响区碳化物析出相的数量略微增加,显微硬度逐渐增大,冲击韧性逐渐降低,拉伸断裂位置和拉伸强度没有变化。     

Al-Zn-Mg合金焊接接头性能分析

对研制的Al-Zn-Mg合金和焊丝施焊后的焊接接头进行了宏、微观组织分析以及力学性能测试。结果表明，焊接系数可达76．6％。焊接接头最薄弱的环节是焊缝区，其次是焊接热影响区的软化区。提高焊接接头的力学性能关键是焊丝成分进一步优化。另外，焊接接头留有余高可以在一定程度上提高其承载能力。     

20Cr钢与B级钢焊接接头的组织和性能

采用低温冲击试验、拉伸试验、硬度试验以及金相分析等方法对ER50-6焊丝气体保护焊焊接20Cr钢与B级钢焊接接头的显微组织和性能进行了研究.结果表明,用ERS0-6焊丝气体保护焊焊接20Cr钢和B级钢可获得性能良好的焊接接头,其接头的强度不低于B级钢.焊缝组织为网状分布的先共析铁素体及少量无碳贝氏体;20Cr钢侧近缝区有无碳贝氏体及少量板条马氏体;在B级钢侧热影响区的块状铁素体基体上有少量粒状贝氏体.     

碳素结构钢与高速工具钢摩擦焊与闪光焊接头的组织和性能

采用摩擦焊及闪光焊两种不同工艺,对碳素钢45钢和W18Cr4V高速钢异种金属切削刀具实现连接.对焊接接头的组织和性能进行了对比分析,进而研究了闪光焊接头焊缝区强韧性损伤的机理;阐述了摩擦焊的优越性及接头形成机制,并提供了摩擦焊接头较佳的焊接参数.结果表明:45钢和W18Cr4V钢切削刀具经摩擦焊接,改善和提高了摩擦焊接头焊缝区的组织和性能.     

静轴肩搅拌摩擦焊2A14-T4铝合金T形接头的组织和性能

采用静轴肩搅拌摩擦焊技术实现了8.5 mm厚2A14-T4铝合金T形接头的焊接,研究了接头的宏观成型、显微组织及力学性能.结果表明:焊缝表面呈现光滑无弧纹特征,焊缝外部和内部未发现焊接缺陷;SSFSW T形接头截面焊接区域形貌整体呈现两头宽、中间窄的"开口哑铃"状,焊核区晶粒表现为取向随机的等轴晶,焊核区平均晶粒尺寸表现为第二次焊核区最大,焊接重合区次之,第一次焊核区最小.焊核区再结晶机制以几何动态再结晶为主并伴随有部分连续动态再结晶;热机影响区较窄且晶粒被拉长变形,热影响区组织晶粒长大粗化;焊接过程中第二相粒子的析出粗化造成焊核区硬度降低,硬度最低点出现在第一道焊缝热影响区与热机影响区的交界处;接头的硬度较低区域和结构尺寸引起的应力集中导致T形接头底板与筋板容易萌生裂纹、发生断裂;断口中存在较多的撕裂棱以及大小不一的韧窝,在韧窝中存在尺寸不均匀的第二相颗粒,断口呈现韧性断裂特征.     

Effects of external electric field on microstructure and property of friction welded joint between copper and stainless steel

Formability is a key factor which influences the friction weldability of dissimilar materials. Resistance to formability of metals can be reduced by the electric induced plasticity under an external electric field. Friction welding of T2 Copper and 1Cr18Ni9Ti stainless steel was carried out under the electric fields with an attempt to improve the friction weldability of these two materials. Effects of different types of external electric field on the microstructure of the welded joints were investigated and distributions of the dominating elements in the weld zone were analyzed using EDX. Torsion strength of the joints obtained from different welding parameters was tested. It was indicated that the dynamic recrystallization of the weld metal was enhanced by the applying electric fields. For the specimen connected to the cathode of the power supply (referring to negative field), much homogenous distribution of the recrystallized grains in the weld zone appeared. The diffusion distance of the dominating elements increased under either an AC electric field or a negative field. The torsion strength of the welding joints was improved with applying the external electric field, especially with the AC electric field.     

Influence of an electric field on the microstructures and properties of the friction-welded joint of LY12 alloy

By means of microstructure observation, hardness test and torsion strength test, some characteristics of the friction welded joint undergoing an external electric field have been studied quantitatively. The recrystallization grain size in the weld metal zone (WMZ) decreases when the external electric field is applied. The equiaxed grains in the dynamic recrystallization zone (DRZ) increase and the equiaxed characteristic of recrystallization grains in the DRZ is enhanced. The microstructure of the welded joint along the axial direction becomes more homogeneous. When the same friction welding parameters are applied, the electric field causes an increase in the width of the DRZ. Moreover, the external electric field effect leads to the hardness of the welded joint increasing, and also homogenizes the hardness distribution along the radial and axial directions. In addition, the average torsion ductility of the weld metal increases in the case of applying the external electric field.     

电磁场对高速钢与45钢感应摩擦焊接的影响

利用电磁场对金属材料产生的"场致效应",调节摩擦焊接表面的温度场,以改善异种金属摩擦焊接组织及性能.研究了外加电磁场对W6Mo5Cr4V2高速钢和45钢摩擦焊缝显微组织、合金元素扩散及焊接接头力学性能的影响.结果表明,摩擦加热阶段施加电磁场使45钢近缝区铁素体的数量减少;而在顶锻阶段施加电磁场,使45钢侧铁素体数量有所增多.同时,在顶锻阶段施加电磁场作用时,主要合金元素C、Cr、W的扩散区宽度明显增大.在顶锻阶段采用较短的电磁场施加时间和较低的感应电流强度,可以提高W6Mo5Cr4V2高速钢和45钢摩擦焊接头的抗拉强度.     

C、Cu和Cr对10CrNiCu埋弧焊丝配烧结焊剂焊缝力学性能的影响

针对船用10CrNiCu钢设计了4种不同化学成分的埋弧焊丝,研究了焊丝与烧结焊剂配套使用时C、Cu、Cr元素对焊缝力学性能的影响。结果表明C、Cu可以增加焊缝中针状铁素体的含量,细化晶粒尺寸,从而提高焊缝的低温冲击韧性和拉伸强度,Cr含量增加可以提高焊缝强度,但会降低焊缝的冲击韧性。     

Fatigue behavior of dissimilar friction stir welds between cast and wrought aluminum alloys

Cast aluminum alloy, AC4CH-T6, and wrought aluminum alloy, A6061-T6, were joined by means of friction stir welding (FSW) technique. The effect of microstructure and post heat treatment on fatigue behavior of the dissimilar joints was investigated. Near the weld centre, Vickers hardness was lower than in the parent metals and the hardness minima were observed along the trace route of FSW tool’s shoulder edge. Tensile fracture took place on A6061 side where the hardness was minimal, resulting in the lower static strength of the dissimilar joints than AC4CH or A6061. Fatigue fracture occurred on AC4CH side due to casting defects and the fatigue strength of the dissimilar joints was similar to that of AC4CH, but lower than that of A6061. Friction stir process (FSP) and post heat treatment successfully improved the fatigue strength of the dissimilar joints up to that of the parent metal, A6061. __________ Translated from Problemy Prochnosti, No. 1, pp. 150–154, January–February, 2008.     

焊缝匹配影响焊接残余应力的研究

采用有限元法对相同温度场的焊缝与母材强度和线膨胀系数匹配影响焊接残余和的规律进行了数值模拟,计算结果表明：等强度等匹配的焊缝区纵向残余应力水平高达母材的屈服强度,     

Evaluation of the microstructure and mechanical properties of friction stir welded 6005 aluminum alloy

Abstract

The microstructural change related with the hardness profile has been evaluated for friction stir welded, age hardenable 6005 Al alloy. Frictional heat and plastic flow during friction stir welding created fine and equiaxed grains in the stir zone (SZ), and elongated and recovered grains in the thermomechanically affected zone (TMAZ). The heat affected zone (HAZ), identified only by the hardness result because there is no difference in grain structure compared to the base metal, was formed beside the weld zone. A softened region was formed near the weld zone during the friction stir welding process. The softened region was characterised by the dissolution and coarsening of the strengthening precipitate during friction stir welding. Sound joints in 6005 Al alloys were successfully formed under a wide range of friction stir welding conditions. The maximum tensile strength, obtained at 507 mm min^-1 welding speed and 1600 rev min^-1 tool rotation speed, was 220 MPa, which was 85% of the strength of the base metal.     

6061铝合金搅拌摩擦焊工艺窗口的研究

目的提高6061铝合金搅拌摩擦焊接头的质量,确定合适的工艺参数范围。方法设计3种不同的搅拌头进行焊接,分析接头拉伸强度与组织性能,并根据试验结果建立工艺窗口,选择合适的轴肩尺寸及工艺参数范围。结果随着轴肩尺寸减小,焊缝宽度、金属流动性、热力影响区面积均减小,在较大的焊接速度及较小的搅拌头转速下,焊缝底部出现缺陷;采用轴肩直径小的搅拌头进行焊接,在一定焊接参数范围内,焊接接头的拉伸强度得到提高;随着轴肩直径减小,焊核区晶粒组织细化,材料变形程度减小;由建立的工艺窗口可知,当轴肩尺为9 mm时,可选择的参数范围最大。结论焊接时采用小尺寸轴肩,可以在搅拌头行走速度更低、转速更大的情况下,仍然可以保持合理产热量,使接头性能得到提高。     

Effect of welding wire and groove angle on mechanical properties of high strength steel welded joints

Mechanical properties of high strength steel welded joints strictly depend on the welding process, the filler material composition and the welding geometry. This study investigates the effects of using cored and solid welding wires and implementing various groove angles on the mechanical performance of weld joints which were fabricated employing the gas metal arc welding process. It was found that weld joints of low alloy, high strength steels using low alloy steel cored welding wires exhibited higher tensile strength than that of low alloy steel solid wire and chromium‐nickel steel bare welding wire when the method of gas metal arc welding is employed. The effect of groove angle on the strength and toughness of V‐groove and double V‐groove butt‐joints was investigated. V‐groove joints, with higher tensile strength than double V‐groove joints in the whole range of groove angles, were superior in toughness for small groove angles, but impact toughness values of both joints were comparable for large angles. The effect of heat input and cooling rate on the weld microstructure and weld strength was also investigated by performing thermal analysis employing the commercial software ANSYS. It was concluded that cooling rate and solidification growth rate determined the microstructure of the weld zone which had great consequences in regard to mechanical properties.     

Comparative experimental study on the modification of microstructural and mechanical properties of friction stir welded and gas metal arc welded EN AW‐6061 O aluminum alloys by post‐weld heat treatment

In this paper, the effects of post‐weld heat treatment on modification of microstructures and mechanical properties of friction stir welded and gas metal arc welded AA6061‐O plates were compared with each other. Gas metal arc welding and friction stir welding were used as the applicable welding processes for AA6061‐O alloys. The applied post‐weld heat treatment consisted of solution heat treatment, followed by water quenching and finally artificial aging. The samples were classified as post‐weld heat treated and as‐welded joints. The microstructural evolution, tensile properties, hardness features and fracture surfaces of both as‐welded and post‐weld heat treated samples were reported. The results clearly showed that friction stir welding process demonstrated better and more consistent mechanical properties by comparison with the gas metal arc welding process. The weld region of as‐welded samples exhibited a higher hardness value of 80 HV0.1 compared to the base material. In addition, the feasibility of post‐weld heat treatment in order to enhance the mechanical properties and to obtain more homogeneous microstructure of 6061‐O aluminum alloys was evaluated.