浅谈焊接裂纹形成的原因及解决方法

某厂H型钢焊接加工过程中出现裂纹。根据裂纹的特点,从工艺焊接线能量、拘束应力、缺IZl敏感、焊前预热、焊接施工环境、焊后处理等方面分析裂纹产生的原因,提出了解决H型钢焊接过程中防止裂纹的工艺措施,控制热输入量,焊前、焊后处理,改善焊接环境等。经过以上工艺改进后进行焊接,焊接质量良好,取得了较好的效果,为同类H型钢钢结构施工提供有益的借鉴。     

铸造镁合金的焊接修复技术研究现状及发展方向

镁的密度为1.74 g/cm~3,是铝密度的2/3,具有铸造性好、比强度高的特点,可以在减轻结构质量方面发挥重要作用,铸造镁合金被广泛应用于航空航天、汽车等领域的重要机械零件。尤其是在铸造镁合金中添加稀土元素,可进一步提升镁合金的室温强度和高温蠕变性能,以满足更多领域的应用需求,进一步扩大镁合金的应用。镁合金在铸造过程中不可避免会产生铸造缺陷,为保障铸造镁合金构件的可靠性,针对铸造镁合金缺陷的焊接修复技术具有切实的工程意义。从铸造镁合金缺陷修复的实际需求出发,结合镁合金独特的物理特性及焊接性,国内外学者针对铸造镁合金缺陷的焊接修复技术展开了研究。钨极氩弧焊具有成本低、操作简单、适用性强的特点,在铸造镁合金的焊接修复中应用最广,为保证焊接质量,需要从缓慢冷却、控制热输入等方面制定严格的焊接工艺;冷金属过渡焊接可实现焊接过程的精确控制,从而提高熔化极气体保护焊焊接镁合金的焊缝质量;激光焊具有能量密度高度集中的特点,获得的焊接接头具有较小的热影响区,但需制定合理的工艺参数以避免焊接缺陷的产生;搅拌摩擦焊可较好地完成铸造缺陷修复,但由于构件复杂结构的影响,在铸造镁合金焊接修复中的应用受限。另外,脉冲激光焊、电子束焊、钎焊、扩散焊及复合焊接方法均在镁合金的焊接中有所应用,但在铸造镁合金的焊接修复中尚未见实际应用。然而,由于铸造镁合金特殊的物理性质和焊接性,以及待修复构件的复杂结构,已进行的铸造镁合金缺陷焊接修复技术仍存在许多局限性,亦缺乏深入系统的理论研究。为了有效解决铸造镁合金的实际修复工程问题,无论是该类铸造镁合金焊接修复技术,还是关于修复技术的系统化研究,都需要大量的探索性工作。本文简述了铸造镁合金的应用及其焊接性,重点介绍了钨极氩弧焊、冷金属过渡焊接、激光焊、搅拌摩擦焊在铸造镁合金焊接修复中的应用,讨论了目前铸造镁合金焊接修复技术存在的问题和未来的发展,为实现焊接修复区组织与性能更加可控的智能修复技术提供参考。     

镁合金焊接方法的研究现状及展望

镁合金发展前景广阔,但焊接性差限制了其应用.概述了镁合金各种焊接方法的优点、缺点以及发展现状.重点介绍了镁合金最有前途的固相连接方法--搅拌摩擦焊,并展望了镁合金搅拌摩擦焊的应用前景.指出搅拌摩擦焊是镁合金最好的连接工艺,应深入研究.     

破裂2Cr13不锈钢阀杆补焊工艺

根据2Cr13不锈钢的焊接特点,介绍了2Cr13不锈钢阀杆破裂后的补焊工艺.指出在工程实际应用中,2Cr13不锈钢阀杆如发生破裂,可采用合适的焊接工艺进行补焊,能有效的保证焊接质量和使用性能;2Cr13不锈钢阀杆在补焊前要进行预热,能防止冷裂纹;2Cr13不锈钢阀杆在补焊后要进行热处理,能减小残余应力,均匀组织,防止焊接缺陷.     

随焊激冷防止高强铝合金焊接热裂纹的数值模拟

采用热弹塑性有限元方法对随焊激冷防止焊接热裂纹的工艺过程进行了数值模拟 ,动态定量地描述了温度场、位移场和应变场的演变过程 ,清晰地揭示了随焊激冷防止焊接热裂纹的机理及主要参数的影响规律 .研究表明 ,随焊激冷能够通过冷源作用区的冷却收缩造成对其前方处于BTR金属的横向挤压 ,推迟塑性拉伸应变的开始形成温度并减缓其发展速率 ,因而降低热裂纹倾向 ;采用较小的激冷距离有利于降低热裂纹倾向 ,在激冷距离较大时提高激冷功率仍有防止热裂纹的作用 ;加大外部拘束会在一定程度上削弱随焊激冷防止热裂纹的效果 .     

铝合金线性摩擦焊研究现状

线性摩擦焊作为一种新型的固相焊接技术,热输入低、焊接应力小,适合于铝合金的焊接。介绍了线性摩擦焊的工作原理,主要综述了铝合金线性摩擦焊数值模拟、微观组织和力学性能等3个方面的研究进展。在此基础上,着重介绍了摩擦压力、焊接时间及振动频率等工艺参数对铝合金线性摩擦焊微观组织和力学性能的影响,介绍了工艺参数对铝合金与不锈钢、纯铜、镁合金等异种金属线性摩擦焊微观组织、力学性能及金属间化合物种类和分布的影响。最后,对铝合金线性摩擦焊在数值模拟、接头性能及金属间化合物调控方面存在的不足进行了总结,并对其主要发展方向进行了展望。     

随焊激冷防止焊接热裂纹新方法的研究

从焊接力学角度提出了随焊激冷防止焊接裂纹的新方法，阐明了随焊激冷防止焊接热裂纹的机理，并就随焊接冷参数对焊接热裂纹的作用进行了研究。通过测量近缝区两点在焊接过程中位移的实时变化过程，验证了随焊激冷防止焊接热裂纹的新方法。     

镁合金焊接研究现状

近年来,随着镁合金在交通运输、航空航天、3C等领域的广泛应用,焊接技术成为制约其应用的瓶颈。本文针对镁合金的特点及焊接性进行了分析,对钨极氩弧焊、熔化极惰性气体保护焊、激光焊、电子束焊、搅拌摩擦焊在镁合金焊接中的研究现状进行了介绍,并对镁合金焊接未来的发展方向进行了展望。     

镁合金摩擦焊的研究进展

介绍了摩擦焊的基本原理及特点,综述了镁合金摩擦焊的研究进展,重点讨论了Mg-Mg同种材料和Mg-Al异种材料摩擦焊工艺、连接机理、接头微观组织及其力学性能。同时分析了目前研究中存在的问题,指出镁合金摩擦焊接头的三维温度场、应力应变场、塑性流变机制等研究尚需进一步完善,此外工艺优化和设置成分过渡层是获得优质摩擦焊接头的发展方向。     

铸造高温合金精铸零部件的补焊研究进展

主要综述了采用钨极氩弧焊、激光焊、钎焊与粉末冶金修复再制造等焊接方式进行高温合金精铸件的补焊的研究现状及发展趋势.总结了采用不同补焊方法时焊接工艺对焊接性能的影响.指出了今后铸造高温合金精铸件的补焊的研究方向.     

Fatigue life estimation of ultrasonic spot welded Mg alloy joints

Lightweight magnesium alloys are increasingly used in automotive and other transportation industries for weight reduction and fuel efficiency improvement. The structural application of magnesium components requires proper welding and fatigue resistance to guarantee their durability and safety. The objective of this investigation was to identify failure mode and estimate fatigue life of ultrasonic spot welded (USWed) lap joints of an AZ31B-H24 magnesium alloy. It was observed that the solid-state USWed joints exhibited a superior fatigue life compared with other welding processes. Fatigue failure mode changed from interfacial failure to transverse-through-thickness crack growth with decreasing cyclic load level, depending on the welding energy. Fatigue crack initiation and propagation occurred from both the notch tip inside the faying surface and the edge of sonotrode indentation-footprints due to the presence of stress concentration. A life prediction model for the spot welded lap joints developed by Newman and Dowling was adopted to estimate the fatigue lives of the USWed magnesium alloy joints. The fatigue life estimation, based on the fatigue crack growth model with the global and local stress intensity factors as a function of kink length and the experimentally determined kink angle, agreed fairly well with the obtained experimental results.     

Hot Cracking in AZ31 and AZ61 Magnesium Alloy

This paper examined the impact of the number of thermal cycles and augmented strain on hot cracking in AZ31 and AZ61 magnesium alloy. Statistical analyses were performed. Following observation using a scanning electron microscope (SEM), an energy dispersive spectrometer (EDS) was used for component analysis. Results showed that Al content in magnesium alloy has an effect on hot cracking susceptibility. In addition, the nonequilibrium solidification process produced segregation in Al content, causing higher liquid Mg-alloy rich Al content at grain boundaries, and resulting into liquefied grain boundaries of partially melted zone (PMZ). In summary, under multiple thermal cycles AZ61 produced serious liquation cracking. AZ61 has higher (6 wt%) Al content and produced much liquefied Mg17Al12 at grain boundaries under multiple thermal cycles. The liquefied Mg17Al12 were pulled apart and hot cracks formed at weld metal HAZ due to the augmented strain. Since AZ31 had half the Al content of AZ61, its hot-cracking susceptibility was lower than AZ61. In addition, AZ61 showed longer total crack length (TCL) in one thermal cycle compared to that in three thermal cycles. This phenomenon was possibly due to high-temperature gasification of Al during the welding process, which resulted in lower overall Al content. Consequently, shorter hot cracks exhibited in three thermal cycles. It was found the Al content of AZ31 and AZ61 can be used to assess the hot-cracking susceptibility.     

镁合金焊接技术的研究进展及应用

镁合金有很多优异的性能,在航空航天、汽车、电子等领域具有广阔的应用前景,而镁合金的焊接技术是制约其发展的关键技术之一.简述了镁合金的性能及应用,着重讨论了镁合金钨极氩弧焊、激光焊、电子束焊、激光-TIG复合焊、搅拌摩擦焊、电阻点焊的焊接特点,综述了镁合金焊接技术的研究进展和应用.     

A review: Hot topics on magnesium technology in China

Magnesium alloys have wide applications in automobiles, aerospace and so on due to many advantages, while a number of undesirable properties including poor corrosion resistance, inferior creep resistance and bad plastic processing ability have hindered their applications. Creep-resistant magnesium alloy design, plastic processing of magnesium alloys and rapid solidification processing of magnesium alloys have become the hot topics in magnesium technology. Other than these, surface modification as well as laser beam welding are also involved. The research progress and development in magnesium technology in China are reviewed in the paper.     

A review: Hot topics on magnesium technology in China

Magnesium alloys have wide applications in automobiles, aerospace and so on due to many advantages, while a number of undesirable properties including poor corrosion resistance, inferior creep resistance and bad plastic processing ability have hindered their applications. Creep-resistant magnesium alloy design, plastic processing of magnesium alloys and rapid solidification processing of magnesium alloys have become the hot topics in magnesium technology. Other than these, surface modification as well as laser beam welding are also involved. The research progress and development in magnesium technology in China are reviewed in the paper.     

Eigenschaften langzeitgealterter,artgleicher Schweißnähte der Ni‐Basislegierung alloy 602 CA

Properties of long‐time aged matching joints of Ni‐base alloy 602 CA The paper presents results about the influence of a 2‐year exposure in the production process of ammonia synthesis on the microstructure and the mechano‐technological properties of matching TIG‐ and e‐manual welds of the high‐temperature resistant Ni‐based alloy 602 CA (NiCr25FeAlY, Material‐No. 2.4633 / UNS N 06025). These results show, that Ni‐base alloy 602 CA possesses a very good resistance against metal dusting. Furthermore typical metallurgical characteristics of the welding process of this extremely hot‐crack sensitive alloy are presented and recommendations for a hot‐crack safe manufacturing of components made of this alloy are given.     

Nd:YAG激光与半导体激光复合焊接对铝合金焊缝组织和性能的影响

目的 提高铝合金的焊缝抗拉强度,解决铝合金焊接过程中的裂纹缺陷。方法 采用脉冲Nd:YAG激光与半导体激光复合焊接铝合金,先用Nd:YAG激光形成焊接熔池,然后用半导体激光对熔池进行加热保温,获得无裂纹的焊缝,并对焊缝进行抗拉强度测试。结果 与单独的Nd:YAG激光焊接相比,Nd:YAG激光与半导体激光复合焊接的铝合金焊缝抗拉强度提高了50%,达到193MPa,为母材抗拉强度的90%。结论 2束激光的结合延长了熔池的冷却凝固时间,从而有效避免了热裂纹,减少了焊接缺陷,提高了焊接质量。     

先进航空材料焊接过程热裂纹研究进展

高焊接热裂纹敏感性是制约新一代合金材料在航空航天领域推广应用的技术瓶颈。本文分别从焊接热裂纹的产生机理和各类合金裂纹敏感性实验的角度梳理该方向的研究进展。焊接热裂纹主要包括凝固裂纹（在焊缝内部产生）和液化裂纹（在焊缝与部分熔化区交界处产生）。影响焊接热裂纹产生的因素包括材料成分、焊接热循环以及接头热应力。在梳理焊接热裂纹机理研究的基础上,分别总结了铝合金、镁合金、先进高强钢以及镍基合金焊接热裂纹的实验研究进展。建立考虑复杂多组元以及结晶形态对裂纹敏感性影响的量化判据,是该领域未来的重要发展方向。针对母材和焊材进行成分优化、添加形核剂或实施辅助工艺措施,是工程应用领域抑制热裂纹缺陷的有效方法。开展焊接热裂纹产生机理及其抑制方法研究,有助于突破新一代合金材料加工技术瓶颈,推进其在航空航天领域的应用。     

High cycle fatigue behavior of as-extruded ZK60 magnesium alloy

Tensile and high cycle fatigue properties of hot extruded ZK60 magnesium alloy have been investigated, in comparison to that of hot-extruded plus T5 heat-treated ZK60 magnesium alloy which was named as ZK60-T5. High cycle fatigue tests were carried out at a stress rate (R) of −1 and a frequency of 100 Hz using hour-glass-shaped round specimens with a gage diameter of 5.8 mm. The results show that tensile strength greatly improved and elongation is also slightly enhanced after T5 heat treatment, and the fatigue strength (at 10⁷ cycles) of ZK60 magnesium alloy increases from 140 to 150 MPa after T5 heat treatment, i.e., the improvement of 7% in fatigue strength has been achieved. Results of microstructure observation suggest that improvement of mechanical properties of ZK60 magnesium alloy is due to precipitation strengthening phase and texture strengthening by T5 heat treatment. In addition, fatigue crack initiations of ZK60 and ZK60-T5 magnesium alloys were observed to occur from the specimen surface and crack propagation was characterized by striation-like features coupled with secondary cracks.     

搅拌摩擦焊镁合金隔声性能的研究

伴随搅拌摩擦焊在镁合金上的广泛应用,对其隔声特性研究尤为重要,基于自适应网格技术,对搅拌摩擦焊过程进行数值模拟,为后续声学计算提供约束模态,解决了材料属性难以确定的问题,一定程度上实现了焊接与声学的结合。自行设计和制造了混响箱,用以测量焊接镁合金板的隔声量,弥补了混响室测试小试件的不足。进而使用finite element-statistical energy analysis(FE-SEA)混合法计算焊接件的隔声量,与试验结果进行对比,吻合良好,表明此方法行之有效。通过对比焊接前后镁合金板件的隔声量,发现在吻合低谷区,焊接后板件的隔声有所降低。为了研究焊接参数对隔声的影响,分别改变焊接速度和搅拌头旋转速度,观察隔声量的变化,结果表明,这些参数都需要合理的设置,并非越大或者越小越好。