7005-T6铝合金搅拌摩擦焊焊接工艺与接头组织性能研究

通过固定搅拌头旋转速度,改变焊接速度对8 mm厚7005-T6铝合金板材对接接头进行搅拌摩擦焊,分析了在搅拌摩擦焊过程中不同焊接速度对焊接接头力学性能、焊缝微观组织和硬度的影响.研究表明,当焊接速度在200～350 mm/min时,接头的抗拉强度先减小后增大,当焊接速度为350 mm/min时焊接接头抗拉强度最高.由于...     

转速、焊速对6061-T6铝合金搅拌摩擦焊性能的影响

对3 mm厚6061-T6铝合金板材的搅拌摩擦焊工艺进行试验研究,分析了在搅拌摩擦焊焊接过程中不同搅拌头转速、焊接速度对焊接接头力学性能和焊缝中"S"线缺陷的影响。研究结果表明,当搅拌头转速保持在1 200 r·min~(-1)时,焊接工艺窗口较宽;当焊接速度为700 mm·min~(-1)、搅拌头的旋转速度为1 200 r·min~(-1)时焊缝的强度最高,为251.608 MPa,焊缝强度达到了母材的81.16%。焊接过程中提高搅拌头的旋转速度、减小焊接速度能够减少焊缝中"S"线缺陷的产生。     

铝合金氧化膜厚度对搅拌摩擦焊接接头组织和性能的影响

对表面氧化膜厚度不同的6005A-T4铝合金挤压板材进行搅拌摩擦焊接,观察接头宏观形貌、显微组织,并测试拉伸力学性能,研究氧化膜厚度对焊接后接头组织和力学性能的影响。试验结果表明:在搅拌头转速1 200 r·min-1和焊速750 mm·min-1时,可获得质量良好的接头;通过表面处理改变母材焊接前氧化膜厚度,由自然状态下5μm增至30μm,可使焊接接头抗拉强度由194.9 MPa下降至177.1 MPa,接头强度系数由82.56%下降到72.38%,说明氧化膜厚度对接头强度有极大影响;通过对接头处断口进行扫描电子显微镜和能谱分析,确定S曲线中"黑色物质"主要成分为Al2O3,而且大量氧化物颗粒形成的弱连接是导致接头抗拉强度下降的主要原因。     

6061铝合金搅拌摩擦焊接头组织与性能研究

采用搅拌摩擦焊方法(FSW)对6 mm厚的6061-T4铝合金板材进行对接,焊后利用光学显微镜(OM)和扫描电镜(SEM)分析、对比了焊接接头和母材的显微组织和断口形貌特征,并测试了其室温拉伸性能和显微硬度。实验结果表明:选择了适合于6061-T4铝合金板材搅拌摩擦焊的工艺参数:焊接时搅拌头旋转速度为1200 r.min-1,工件的进给速度为300 mm.min-1,在此参数下获得了与母材等强度、韧性接近于母材的焊接接头,为此种合金应用于汽车关键零部件提供了可靠的工艺方法。FSW板材接头焊核区的组织和性能明显优于其他区,热影响区是接头最薄弱的部分,焊核区的硬度最高,而热影响区的硬度最低,焊缝金属发生回复再结晶使晶粒细化。断口分析表明,断裂发生在热影响区,由于搅拌头的旋转运动和热量的累积,该区存在晶粒长大、组织粗化现象。对工艺参数的优化实验表明,搅拌头旋转速度与焊接速度对接头性能的影响存在一定的适配关系,通过工艺参数的调整可以有效地控制热影响区的焊缝组织和改善焊接接头的性能。细晶强化是搅拌摩擦焊接头强度与韧性提高的主要原因。     

人工时效对6082铝合金焊接接头组织和性能的影响

对6082-T6和6082-T4铝合金搅拌摩擦焊接头进行人工时效处理,并采用金相组织观察、拉伸力学性能和显微硬度测试等途径研究了焊后人工时效对焊接接头组织和力学性能的影响。研究结果表明:人工时效后组织内析出物的尺寸明显减小,但对焊缝晶粒尺寸无明显影响;人工时效后6082-T6焊接接头抗拉强度由269.5 MPa提高至306.5 MPa,6082-T4焊接接头的抗拉强度由208 MPa提高至335 MPa,后者的力学性能优于前者,可接近母材抗拉强度;人工时效后,6082-T6焊缝焊核中心硬度值从91 HV升至114 HV,6082-T4焊缝与母材硬度均显著提升,焊核中心硬度值从85 HV升至118 HV,母材硬度从85 HV提升至122 HV。     

LF21薄板搅拌摩擦焊工艺研究及微观组织分析

采用搅拌摩擦焊接方法对厚度为1．5mm的LF21薄板铝合金板在进行焊接试验,首次提出搅拌头旋转速度为5000r／min时的焊接工艺,实验结果表明：在焊接速度为70～105mm／min,压入量适中,并采用喷气冷却,可以获得较好的焊接接头,抗拉强度达到最大值111．530MPa。焊缝中存在3个组织变化区,其中焊核区内是细小均匀的等轴晶,焊缝两侧热机影响区组织存在较大差异,热影响区组织发生了回复、再结晶和粗化。     

挤压态6060-T5和铸态6061铝合金异种搅拌摩擦焊接头组织及力学性能研究

采用搅拌摩擦焊焊接挤压态6060-T5和铸态6061铝合金板材,在不同的焊接工艺下,对焊接接头的微观组织及力学性能进行研究。结果表明：焊接速度过快会在焊接表面形成少许毛刺,影响表面质量,但焊接接头均没有明显缺陷,焊核区微观组织还能得到显著细化。焊接接头硬度略低于同种铝合金焊接接头硬度,且受两种材料混合影响,焊核区硬度值波动较大。接头抗拉强度随着焊接速度的增大而提高,且均保留了较好的拉伸变形能力,断裂方式是韧-脆混合型。     

汽车用新型钛合金的搅拌摩擦焊研究

进行了6 mm厚汽车新型钛合金Ti-6Al-4V-0.2Y板材的单面对接搅拌摩擦焊试验,并对接头的宏观形貌、X光无损探伤、显微组织、表面硬度和力学性能进行测试与分析。结果表明,钛合金Ti-6Al-4V-0.2Y板材的焊接接头成形好、表面光亮、无明显缺陷、力学性能较佳;接头的室温抗拉强度达到900 MPa、接头系数高达96%;接头硬度最大值位于焊核区、最小值位于前进侧热影响区。     

大厚度紫铜搅拌摩擦焊接

采用搅拌摩擦焊接方法对厚度为30mm和50mm的T2紫铜板分别进行单面和双面焊接实验,并对焊缝的微观组织与力学性能进行了分析.结果表明:在一定的参数范围内,可获得表面成形美观、内部无缺陷且变形小的对接接头.30mmT2紫铜板单道焊焊后平均抗拉强度为177.2MPa,达到母材的81.7%,断后平均伸长率为25.4%;焊缝横切面显微硬度分布波动较大,最低值位于前进侧热影响区底部,说明了此处位置是焊缝薄弱环节.     

稀土镁合金搅拌摩擦焊接接头组织及性能分析

成功实现了7 mm厚Mg-Gd-Y系镁合金板的搅拌摩擦焊接,用光学电子显微镜、扫描电子显微镜等手段对焊接接头进行分析。实验结果表明:接头表面光滑,没有裂纹。显微组织特征显示接头有明显分区,各区域晶粒度存在差异。在旋转速度为800 r·min-1,焊接速度为100 mm·min-1时,可以获得较好的焊接性能,抗拉强度达到母材的87%,断后伸长率达到母材的84%。焊缝显微硬度的最低值出现在前进侧机械热影响区,断口表现为准解理断裂特征,断口剖面局部可见镁与稀土元素Gd和Y形成的形状规则、颗粒细小的第二相粒子。     

Influence of Rotational Speed on Microstructure and Mechanical Properties of Dissimilar Metal AISI 304-AISI 4140 Continuous Drive Friction Welds

 Fundamental investigation of continuous drive friction welding of austenitic stainless steel (AISI 304) and low alloy steel (AISI 4140) is described. The emphasis is made on the influence of rotational speed on the microstructure and mechanical properties such as hardness, tensile strength, notch tensile strength and impact toughness of the dissimilar joints. Hardness profiles across the weld show the interface is harder than the respective parent metals. In general, maximum peak hardness is observed on the stainless steel side, while other peak hardness is on the low alloy steel side. A trough in hardness distribution in between the peaks is located on the low alloy steel side. Peak hardness on the stainless steel and low alloy steel side close to the interface increases with a decrease in rotational speed. All transverse tensile joints fractured on stainless steel side near the interface. Notch tensile strength and impact toughness increase with increase in rotational speed up to 1500 r/min and decrease thereafter. The mechanism of influence of rotational speed for the observed trends is discussed in the torque, displacement characteristics, heat generation, microstructure, fractography and mechanical properties.     

防护型车用超高强钢的焊接性及焊接工艺

常规工艺大都采用奥氏体、铁素体不锈钢焊丝焊接来避免出现焊接裂纹等缺陷,然而采用这类焊丝焊接的接头抗拉强度和硬度会大幅降低,使得车辆的防护性能也随之降低甚至失效。为了使超高强钢焊接接头的强度和硬度达到较高的使用要求,针对超高强钢(抗拉强度1 500MPa以上)的焊接性及焊接工艺进行了研究。通过理论分析,选取了与母材组织匹配的超低碳马氏体不锈钢焊材,制定了与之匹配的工艺方法及参数,使得焊接后接头与母材组织均为马氏体组织,且有效消除了焊接裂纹等缺陷,从而实现了焊接接头抗拉强度达到母材抗拉强度的70%以上,硬度与母材硬度相当的目标。在试验过程中,采用最经济的MAG焊焊接方法和较容易控制的预热温度,较为经济地满足了工业化生产应用。     

Comparison of microstructure and properties between joints of FSW and TIG 316L austenitic stainless steel

FSW and TIG were conducted on 316L stainless steel.Variation during microstructure and properties in joints obtained by different welding methods was studied.The results show that the effect of severe mechanical stirring and intense plastic deformation creat a fine recrystallized grain in the welding joint during FSW.As for TIG,the temperature of welding joint exceeds the melting point of welded material itself.The entire welding process belongs to the solidification of a small molten pool;and the microstructure of the joint takes on a typical casting structure.When the welding parameters were selected appropriately,the average ultimate tensile strength of FSW joints can reach 493 MPa,which is 83.6%of base metal;the average elongation is 52.1%of base metal.The average ultimate tensile strength of TIG joints is 475 MPa, which is 80.5%of base metal;the average elongation is 40.8%of base metal.The tensile test of FSW joints is superior to the TIG joints.The microhardness of FSW joint compared to base metal and TIG joint having a significant improvement,which arel95.5 HV,159.7 HV and 160.7 HV,respectively;grain refinement strengthening plays an important role in enhancing the microhardness.The electrochemical corrosion tests show that the joint of FSW 316L austenitic stainless steel has a good corrosion resistance.     

海洋平台用EH36厚钢板焊接接头的组织性能分析

按照EN 10225-2009附录E标准要求,采用50 kJ/cm大热输入埋弧焊工艺焊接厚为100 mm海洋平台用EH36钢板,测试分析了焊态及焊后热处理态焊接接头的组织与性能。结果表明,无论焊态还是焊后热处理态,EH36厚钢板焊接接头的硬度HV10≤280,抗拉强度≥510 MPa,-40℃冲击功均值≥50 J,表面组织以粗大的板条状贝氏体＋少量粒状贝氏体为主,心部组织以细小的铁素体＋珠光体为主,表明济钢开发的EH36厚钢板满足海洋平台的焊接生产要求。焊接接头表面与心部熔合线形状及传热状态的差异,是导致表面HAZ晶粒比心部粗大、因而表面韧性低于心部的主要原因。     

A practical strategy for improving the weldability of ultra-thin Al/Mg sheets by ultrasonic-assisted friction stir welding

In order to enhance the weldable thickness and tensile properties of dissimilar ultra-thin Al/Mg alloy sheets, ultrasonic-assisted friction stir welding (UaFSW) was performed. The addition of ultrasonic produces three benefits. First, a sound joint with smooth surface appearance was achieved. Next, weldable thickness and mixing degree of Al/Mg alloys were improved based on better material flow. Finally, continuous intermetallic compound (IMC) layer in the conventional joint was broken into small pieces, delaying crack propagation. Maximum tensile strength of the UaFSW joint reached 130?MPa, which was much more higher than 102?MPa of the conventional joint. It is concluded that UaFSW has a huge potential to join dissimilar alloys, especially those with the formation of IMCs.     

焊接速度对机器人搅拌摩擦焊AA7B04铝合金接头组织和力学性能的影响

针对熔化焊在焊接AA7B04铝合金时易在焊缝中出现孔洞等缺陷,且接头性能下降明显、焊后变形大,以及采用铆接等机械连接方式会增加连接件的重量等问题,采用集成了搅拌摩擦焊末端执行器的KUKA Titan机器人对2 mm厚AA7B04高强铝合金进行了焊接,在转速为800 r·min-1的条件下,研究了焊度对焊接过程中搅拌头3个方向的受力F_x、F_y和F_z的影响.研究发现,F_z受焊速的影响显著,随焊速的增加而降低.利用光学显微镜、透射电子显微镜、拉伸试验、三点弯曲试验和硬度测试等方法,研究了不同焊速下AA7B04铝合金接头的微观组织和力学性能.结果表明:当焊速为100 mm·min-1时,接头的抗拉强度最高为447 MPa,可达母材的80%,且所有接头的正弯和背弯180°均无裂纹;接头横截面的硬度分布呈W型,硬度最低点出现在热力影响区和焊核区的交界处,焊速不同会导致不同的焊接热循环,且随着焊速的增加接头的硬度随之增加;焊核区组织发生了动态再结晶,生成了细小的等轴晶粒,前进侧和后退侧热力影响区的晶粒均发生了明显的变形;前进侧热影响区析出η'相,后退侧热影响区因温度较高析出η'相和尺寸较大的η相.      

搅拌摩擦加工IF钢的组织性能

对3 mm厚的DC04冷轧IF钢板进行搅拌摩擦加工,研究加工区域的微观组织与力学性能.在旋转速度为950 r·min-1,加工速度为60 mm·min-1时,采用加工后强制冷却技术可获得光滑平整且没有缺陷的加工表面.搅拌摩擦加工后组织显著细化,加工中心的平均显微硬度约为HV 135.6,是母材硬度的1.4倍,表面细晶层硬度最高可达到HV 312.8,细晶层和过渡层的抗拉强度分别比母材的抗拉强度提高50.9%和47.6%,加工前后试样的拉伸断口均呈微孔聚合韧性断裂特征.细晶强化对材料抗拉强度的提高起主要作用.      

Optimization of Friction Welding Process Parameters for Joining Carbon Steel and Stainless Steel

 Friction welding is a solid state joining process used extensively currently owing to its advantages such as low heat input, high production efficiency, ease of manufacture, and environment friendliness. Materials difficult to be welded by fusion welding processes can be successfully welded by friction welding. An attempt was made to develop an empirical relationship to predict the tensile strength of friction welded AISI 1040 grade medium carbon steel and AISI 304 austenitic stainless steel, incorporating the process parameters such as friction pressure, forging pressure, friction time and forging time, which have great influence on strength of the joints. Response surface methodology was applied to optimize the friction welding process parameters to attain maximum tensile strength of the joint. The maximum tensile strength of 543 MPa could be obtained for the joints fabricated under the welding conditions of friction pressure of 90 MPa, forging pressure of 90 MPa, friction time of 6 s and forging time of 6 s.     

Establishing a Mathematical Model to Predict the Tensile Strength of Friction Stir Welded Pure Copper Joints

This investigation was undertaken to predict the tensile strength of friction stir welded pure copper. Response surface methodology based on a central composite rotatable design with four welding parameters, five levels, and 31 runs was used to conduct the experiments and to develop the mathematical regression model by means of Design-Expert software. Four welding parameters considered were tool profile design, rotational speed, welding speed, and axial force. Analysis of variance was applied to validate the predicted model. Confirmation experiments including microstructural characterization and conducted tensile tests showed that developed models are reasonably accurate. The results showed that the joints welded using the square and triangular tools had higher tensile strength compared to the joints welded using other tools. The increase in tool rotational speed, welding speed, and axial force resulted in increasing the tensile strength of the joints up to a maximum value. Also, the developed model showed that the optimum parameters to get a maximum of tensile strength were rotational speed, welding speed, and axial force of 942 rpm, 84 mm/min, and 1.62 kN, respectively.