MAIN TOPICS，ABSTRACTS & KEY WORDS

The laser weldability of niobium to 304 stainless steel is very poor. The Nb/ stainless steel joint using direct laser welding process ruptured immediately after welding. The continuously distributed Fe2Nb was the primary reason that embrittled the joint. The silver was selected as the filler metal to join niobium and stainless steel. The weld appearance is good with Ag layer, there are no defects of appearance such as incomplete penetration, burn-through. The hindering effect of Ag transition layer on the formation of Fe2Nb enhances with the increase of thickness of Ag transition layer. And so the strength of joint increases with the thickness of Ag transition layer. The tensile strength of joint is 198 MPa when the thickness of Ag transition layer is up to 1 mm. The formation of brittle Fe2Nb is the key factor to reduce the strength of joint.

niobium,304stainlesssteel,laserwelding,Agtransitionlayer,strengthofjoint

Welding visualization process is consisted of three parts of visual detection, information processing and intelligent control. In this paper, different visualization methods corresponding to specific detection signals were summarized, such as image detection method, infrared thermal image method, non-destructive testing visualization based on weld defect imaging and measurement visualization based on molten pool vibration. Then, the advantages and disadvantages of active visual method and passive visual method were compared from different perspectives. The development methods of information processing software and the application of image processing technology in the welding visualization were introduced, and different intelligent control methods applied during the welding visualization process were described. A positive expectation and prospect for the development of welding visualization technology in the future was given.

visualization,visualsensing,imageprocessing,intelligentcontrol

The research status on the development of lead-free solders bearing Pr and Nd were reviewed and the effects of Pr and Nd on the microstructure and properties of Sn-Ag-Cu, Sn-Cu(-Ni) and Sn-Zn solders were summarized systematically. Moreover, the reliability and tin whisker problems by adding Pr and Nd also were analyzed. Synchronously, the developing trends of rare earth elements modified solders were prospected, which provides a base support for the developing of new lead-free solders.

rareearthelements,lead-freesolders,reliability,tinwhiskers

The calibration of welding robot system is the premise condition to promote intelligent level, improve the efficiency of welding and ensure the welding quality. A great deal of fruitful research works had carried out by many scholars at home and abroad for the research on calibration of welding robot system. According to different calibration object, the calibration of welding robot system is divided into four categories, the calibration of the welding robot body, the calibration of tools, part calibration and collaboration system calibration. The deficiency of the existing technology and the future development trend of calibration technology were proposed by the brief introduction of the respective calibration on the basis of principle and specific methods to promote the further development and application of the calibration technology of welding robot system.

weldingrobot,calibrationoftechnology,toolscalibration,partscalibration,collaborationsystemcalibration

The thermal cycling curves of the HAZ were measured by infrared thermal imager under different heat input conditions for super austenitic stainless steel 254SMo. The effects of peak temperature and cooling time on the microstructure and mechanical properties of heat affected zone were studied. The results show that the austenite grains grow in the heat affected zone with the increase of the heat input. When the heat input increase up to 1.61 kJ/mm, the average size of the austenite grains increases from 9.12 μm to 16.37 μm, and meanwhile the precipitation of the χ phase occurs. The microhardness and impact properties of welded joints were investigated. The results indicate that the welded joint has excellent integrated mechanical properties at the heat input of 1.46 kJ/mm.

weldingthermalcycle,heataffectedzone,microstructure,mechanicalproperty

Microstructures and mechanical properties of welded joint of 5083 aluminum alloy plate with 5 mm in thickness by plasma-MIG plant welding were studied. The results showed that equiaxed grains distribute in weld seam zone, and their sizes distribute uniformly. Fine equiaxed grains appear in the fusion boundary zone and weld center. The grain sizes on both sides of the weld and near the upper and lower surfaces are larger. The width of PMZ (Part of the melting zone) is larger. Micro-hardness value in the weld seam zone and the heat affected zone is less than that of the base metal, and the minimum hardness value of the weld is 78 HV, which is about 85% of that of the base metal. The tensile strength of the test plate is about 277 MPa, and the elongation is 7.34%. The fracture is located near the fusion line.

5083aluminumalloy,plasma-MIGwelding,microstructure,mechanicalproperties

C/C composites-CuCrZr joints were obtained by a simple active brazing process with Cu-3.5Si brazing filler metal and pure copper interlayer. And a micro-machined technique by means of laser was applied on C/C surface, resulting in a zig-zag interfacial structure between C/C and brazed seam. The results showed that the use of copper interlayer exhibits a significant effect on mechanical strength and thermal shock resistance of the C/C composites-CuCrZr brazed joint. Moreover, joint with zig-zag interfacial structure can further improve the mechanical properties of joint.

C/Ccomposite,CuCrZralloy,brazing,interfacialstructure,mechanicalproperties

In order to improve the abrasion resistance of Z2CN18-10 stainless steel, the nickel-based alloy powder was deposited on the Z2CN18-10 stainless steel by plasma transferred arc welding. The microstructures, phase structure, compositions, microhardness and wear resistance properties of the hardfacing layer with different welding currents were characterized by scanning electron microscope, energy disperse spectroscopy, X-ray diffractometer, microhardness tester and abrasion tester. The results show that the surfacing layer mainly consists ofγ-Ni and precipitates such as FeNi3, Cr23C6, Cr7C3and CrB. The microstructures of nickel base alloy surfacing layer vary from clusters of petals to aquatic plants and the banded structure with the increase of welding current. At the welding current of 110 A, the hardfacing layer possesses the highest average microhardness of 898 HV, and its wear resistance is the best, and its relative wear resistance is 13.76, compared with the substrate. Wear mechanism of the hardfacing layer is adhesive and abrasive wear early, and then oxidative wear later.

plasmatransferredarcwelding,nickelbasealloy,phasestructure,microhardness,wearresistance,wearmechanism

MCrAlY-Cr3C2composite coatings were prepared by using vacuum brazing coating process to improve the high temperature wear resisitance and oxidation resisitance of single crystal superalloy. Methods of OM、SEM, XRD, EDS, EPMA were employed to investigate the microstructures and compositions of the coatings. Results shows that, the coating consists ofγ+γ’, Cr7C3, Cr23C6, Ni3Si and Cr3Si phases. Due to the interfacial interdiffusion, some silicides containing Mo and W are precipitated on the interface, while carbides riched in Ta and Ti with various morphologies are precipitated in the secondary reaction zone of the single crystal superalloy base metal. The hardness of the coating is obviously improved about 3 times, while the distribution is not uniform. The hardness on the interface between coating and substrate is low and the strengthening effect is not obvious because the solid solution strengthening effect is weak, which leads to the hard and the brittle phases have few effects on hardness.

singlecrystalsuperalloy,vacuumbrazingcoating,MCrAlY-Cr3C2,compositecoating

For welding of flat-roof in aluminum alloy car body of EMU, there are some defects such as incomplete fusion, cracks in the weld root and welding deformation in weld bead. So the causes of welding defects were studied in welding process of flat-roof in aluminum alloy car body of EMU, the welding parameters and control method of welding deformation were optimized. The results showed that the optimized can prevent welding defects such as incomplete fusion and root weld crack, and the overall flatness of the EMU Aluminum Alloy body flat can be controlled in less than 3 mm, the welding quality of body flat is effectively guaranteed.

bodyofEMU,weldingprocess,qualitycontrol

Studyonmicrostructureandpropertiesoffrictionsurfacingjointforaluminum/steelwithhybridheatsource

Friction hardfacing of 2A12 aluminum consume rod on Q235 low carbon steel substrate was achieved. The result show that that the preheat of substrate can improve the interface quality, the sound weld with good formation and without defects can be obtained. The surfacing layer is refined under the thermal-mechanical reaction, the grains of the substrate metal near the interface have been distorted along the consume rod rotation direction. The Fe and Al element diffused, and its diffusion range increases when the substrate is preheated. The hardness of the surfacing layer is lower than that of the base material, and it is lower when the substrate is preheated. For the hardness distribution of the consume rod, that in base material is higher than that of friction rolling zone and heat-affected zone, and the friction rolling zone is harder than heat-affected zone.

frictionsurfacing,preheating,dynamicrecrystallization,diffuse

With the development of manufacturing technology of flux cored wire, the flux cored wire in ship welding materials accounts for more than 90%. The flux cored wire used at present are seamed flux cored wire, the welding process has some advantages such as high efficiency, good performance, strong adaptability, but wire feeding is difficult in welding process and there are some disadvantages such as easy corrosion and easy wire surface moisture absorption, difficult storage and transportation and so on. For seamless flux cored wire for surface copper plating processing, Proof-moisture in holding process and wire feeding in welding process are better than that of seamed flux cored wire. The SRSF501 seamless flux cored wire for welding of deposited metal test and process performance were introduced in this paper, which will be applied to the 13 000 t heavy lift ship(HLCV). The result show that the SRSF501 seamless flux cored wire can meet the requirements of ship welding, and show the superiority of the application of seamless flux cored wire. The seamless flux cored wire will be of great significance on the development of medicine core wire.

seamlessfluxcoredwire,SRSF501,seamedfluxcoredwire,shipwelding

According to T Joint of large tilt angle laser penetration welding of carbon steel plate with 2.5 mm and 3 mm in thickness and filler wire of ER50-G, the shape and properties of T joint were systematically studied. It was investigated that the effects of welding parameters such as welding speed, wire feeding speed, laser power, the location of laser on the plate and the defocusing distance on weld formation. The microstructures and hardness of T joint were analyzed and tested. The results show that the optimized welding parameters were acquired, the welded joints welded with the optimized welding parameters are free of defects and meet the requirements. The studies will support the application of the laser welding with filler wire on the body structure of high speed train.

laserweldingwithfillerwire,Tjoint,largetiltangle,carbonsteel