2019年, 第28卷, 第2期　
刊出日期：2019-06-28

  

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  Effect of heat treatment on microstructure and properties of single crystal copper cold-welded joints

  黄勇, 冉小龙, 严晓娟, 郭廷彪

  中国焊接. 2019, 28(2): 1-9. https://doi.org/10.12073/j.cw.20190320001

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  With the means of electron backscattered diffraction (EBSD), mechanical properties test and digital eddy current metal conductivity, the single crystal copper cold-welded joint was tested and analyzed, the structure change of cold-welded joint and the effect of heat treating on the structure and property of cold-welded joint were discussed. The results show that: The deformation area of the single crystal copper cold-welded joint is broken, the crystalline grain at the interface of the joint is refined, and the single crystal structure is still maintained in the base metal area. The hardness of the deformation area increases greatly, the conductivity of the joint does not change much, and the tensile strength of the joint reaches about 70% of that of the base metal. At the interface of the heat treating joint, the single crystal structure of the deformation area and the base metal area are destroyed, and the grains grow up at the interface and the orientation is different. The hardness of the joint interface is much lower than that of the non-heat treating joint, the electrical conductivity of the joint is good, and the tensile strength of the joint is higher than that of the base metal.
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  Extrusion process and property of AZ31 magnesium alloy

  谭明, 权高峰, 刘赵铭

  中国焊接. 2019, 28(2): 10-14. https://doi.org/10.12073/j.cw.20181012001

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  The microstructure and mechanical properties of extruded AZ31 magnesium at different extrusion temperature were investigated. The results show that, at 380 ℃, when the extrusion ratio is 23, the AZ31 magnesium alloy has a dense recrystallized microstructure and good mechanical properties. On one hand, if the extrusion ratio is too small, grain crushing effect is not obvious, and part of the grain is not dynamic recrystallization. On the other hand, larger extrusion ratio can lead to grain growth and banded structure.Tensile fracture characteristics of extruded AZ31 magnesium alloy is quasi-cleavage.
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  Lap joining Al5052 to Ti6Al4V by GTAW with AlSi5 filler wire

  Akhtar Awais, 董红刚, 夏月庆, 李鹏

  中国焊接. 2019, 28(2): 15-23. https://doi.org/10.12073/j.cw.20190225001

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  Lap Joining of 5052 aluminum alloy (Al5052) to Ti6Al4V titanium alloy (Ti6Al4V) was conducted by gas tungsten arc welding (GTAW) process with AlSi5 filler wire. Microstructure examination revealed that non-uniform persistent reaction layer developed in Al5052/Ti6Al4V interfacial area, and the intermetallic compounds (IMCs) layer of Ti(Al, Si)₃ phase formed with the partial substitution of aluminum by silicon. The thickness of IMCs layer varied from less than 1 μm to more than 5 μm in accordance with rise in welding current. Aluminum, silicon and titanium elements in the IMCs layer and weld zone were identified by electron probe microanalysis (EPMA). The results demonstrated that sound Al5052/Ti6Al4V joints can be achieved in the range of 50 A–60 A welding current. The maximum tensile shear strength of 293 N/mm was attained at the optimized welding parameter and the joint fractured in the weld zone. Additionally, the micro-Vickers hardness at Al5052/Ti6Al4V interface was relatively higher in comparison with that of the weld seam and Ti6Al4V base metal as a consequence of IMCs formation.
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  Performance study of a complex thermal barrier functional coating with an electro-spark deposited burn-resistant layer

  汪瑞军, 徐天杨, 马小斌, 罗志恒

  中国焊接. 2019, 28(2): 24-28. https://doi.org/10.12073/j.cw.2019321001

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  It is necessary to develop burn-resistant and thermal barrier complex functional coatings on the titanium alloys surface due to the poor high temperature performance for titanium materials and the problem of “titanium fire” which is easily happened. MTU Aero Engines GmbH has developed a complex functional coating which has great performance of burn resistant and sealing, the coatings has already been applied on compressor blades and casing for aero-engines and showed great performance. In this study, the complex functional coating which is composed of an electro-spark deposited amorphous Ti₄₀Zr₂₅Ni₃ burn-resistant layer and a high-energy plasma spraying prepared YSZ thermal barrier layer was prepared on titanium alloys surface. Then the heat insulation ability, burn resistant performance and the bonding strength were investigated. The experimental results showed that the interface between the coating and the matrix was typical metallurgical bonded, and the average bonding strength was 36.335 MPa; when the temperature of the flame on the one side of the specimen reached 600 ℃, the average insulated temperature of the coating samples was 70.67 ℃; when the flame temperature was 350 ℃, the titanium samples without the complex functional coatings were burned, while the samples with the coating showed great performance of burn resistant even when the temperature was 750 ℃. This indicates that the new functional coating has good heat-insulating and burn-resistant performance.
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  The microscopic mechanical performance for nonuniform welded joint of nickel-based alloy with nanoindentation

  李晓泉, 郝本行, 陈一鑫, 云叶菱, 杨宗辉

  中国焊接. 2019, 28(2): 29-34. https://doi.org/10.12073/j.cw.20181130001

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  To quantify the nonuniform micromechanical performance of welded joint, the load-displacement curves by nanoindentation test were introduced to examine different zones including base metal, coarse grained heat affected zone, partially melted zone, weld metal near the fusion boundary and weld metal center. The results showed that the strengthening effect of weld metal was more obvious than that of heat affected zone for nickel based welded joint and especially in coarse grained heat affected zone, the hardening resulted from overheating was not apparent. Nickel based weld metal with high content of alloying elements which were often segregated at interdendritic regions or precipitated in grain interior under nonequilibrium solidification contributed to the characteristics that differ from conventional low alloy steel welded joint.
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  Welding deviation detection method based on weld pool image contour features

  朱彦军, 吴志生, 李科, 杨培新

  中国焊接. 2019, 28(2): 35-44. https://doi.org/10.12073/j.cw.20190201003

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  Automatic on-line detection of welding deviation based on machine vision is one of the key technologies of arc welding robot tracking welding, in which obtaining high quality weld pool image and accurate welding deviation detection algorithm are two important steps of tracking welding. Through the research and analysis of the weld pool image of gas metal arc welding (GMAW), it was found that the weld pool contains abundant welding information. First, the average gray value of the weld pool image can reflect the interference degree of arc to weld pool image and the heat input of welding process. Secondly, the tip of the weld pool image contour can reflect the center of the groove gap. Finally, the horizontal distance between the center coordinate of the wire contour and the tip coordinate of the weld pool image contour can reflect the welding deviation. On the basis of analyzing the characteristics of weld pool image, this paper proposes a new method of weld seam deviation detection, which includes the collection of weld pool image, image preprocessing, contour extraction and deviation calculation. The results of the tests and analyses showed that the maximum error of the on-line welding deviation obtained was about 2 pixels (0.17 mm) when the welding speed was ≤60 cm/min, and the algorithm was stable enough to meet the requirements of real-time deviation detection for I-groove butt welding. The method can be applied to the on-line automatic welding deviation detection of arc welding robot.
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  Interface microstructure and properties of submerged arc brazing tin-based babbit

  周方明, 李敬, 徐冬豪, 石铭霄

  中国焊接. 2019, 28(2): 45-49. https://doi.org/10.12073/j.cw.20190308001

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  The submerged arc brazing method was used to connect the tin-based babbit alloy with the steel matrix. The microstructure of the submerged arc brazed Babbitt interface layer on the surface of Q235B steel was analyzed by OM, SEM and EDS and the hardness properties of the joint interface layer were tested by MH-5 microhardness tester. the result of research shows that a layer of canine-shaped intermetallic compound with uneven thickness is formed at the interface, and the thickness is 10 – 20 μm. The interface layer includes two kinds of compound layers, namely the FeSn layer near the side of the steel substrate and FeSn₂ layer near the side of the babbit. During the interfacial reaction process, Fe atoms in the steel matrix dissolve into the liquid babbit alloy and form a certain concentration gradient at the interface. The farther from the interface, the lower the Fe atom concentration. The growth of Gibbs free energy of FeSn is lower when the temperature is above 780.15 K, and the temperature during the welding process is much higher than 780.15 K, moreover the precipitation temperature of FeSn is higher. Therefore, in the subsequent cooling process, FeSn is first precipitated from the interface near the side of steel matrix and then FeSn₂ is precipitated from the interface near the side of babbit alloy. Microhardness test showed that the intermetallic compound at the interface layer significantly improved the hardness properties.
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  Principles and application of RES welding technology

  韩立军, 于立建, 张更伟, 钟丽慧

  中国焊接. 2019, 28(2): 50-55. https://doi.org/10.12073/j.cw.20190128001

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  Friction element welding technology is rich of flow drill screws combined with friction welding technology and is developed for the hot-forming steel plate and aluminum alloy welding of car body-in-white. In this paper, the principle of RES welding technology, equipment, technical characteristics, application condition and welding parameters are analyzed systematically. Moreover, the changing laws of welding parameters and welded joint quality control standards are described, which provides the necessary technical support for safety and light-weight car body design requirements. This study has high practical application value, and enriches the automobile body joining technology.
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  A brief review of brazing diamond in cutting tools

  崔冰, 陶善仁, 薛行雁, 钟素娟, 徐东

  中国焊接. 2019, 28(2): 56-64. https://doi.org/10.12073/j.cw.20190314001

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  Diamond has high hardness and good wear resistance. It is widely used in cutting tools and workpieces. Brazing is an effective method to realize high quality cemented carbide joints in various materials connection technologies. This paper analyzes the research status of diamond brazing in detail. The materials used as brazing filler in diamond brazing are reviewed. Copper base filler and nickel base filler are the most commonly used brazing filler in diamond brazing. The advantages and disadvantages of diamond grinding tools under different production methods are analyzed. In addition, a series of new brazing alloys such as amorphous Ni based brazing filler metals are analyzed. Finally, the development trend of diamond brazing is pointed out.