Advanced Materials Research Vols. 189-193

Abstract: Aluminum alloy A5052 and low-carbon steel (SPCC) was welded using resistance spot welding with a cover plate. The interfacial microstructure was observed using electron microscopy. A thick two-layered reaction layer contains Fe2Al5 and FeAl3was observed at the welding interface, respectively. Mechanical property analysis suggested that the reaction layer has no effect on the tensile shear strength of the A5052/SPCC joint and affects the cross tension strength of the joint.

Abstract: The paper presents a Fe-base manual SHS Welding material with CuO+Al and Fe2O3+Al being the thermit and adding ferroalloy materials for solving the problem of low mechanical properties of the manual SHS Welding joint. The structure and properties of the welded joint were studied. The results indicated that: the welding was fusion welding, and weld appearance is good. Cu-Fe alloy in the molten pool experiences liquid phase separation during rapid solidification, and the weld metal is macroscopically separated into one Fe-rich part and one Cu-rich part. Fe-rich phase is filled in the welding line. At the same time, tensile strength of the welded joint was close to 500 MPa, and impact toughness was close to 40J/cm2, and surface hardness was also close to HB350. It also indicated this technology can meet the need of repair of metal parts in field.

Abstract: In this paper, to obtain hardfacing alloys with Anti-wearing，nine kinds of low-hydrogen type coating are designed with orthogonal optimization method and carbon, chromium, erbium and cerium are taken as four factors. The mechanical properties of each hardfacing layer are tested and the microstructure is analyzed. The optimal dosage of the four elements is found by R/S analysis method. There is no crack in continuous surfacing with the electrode prepared with optimal formula, the wear resistance of the corresponding hardfacing layer is good while the hardness reach to 57.9HRC, the microstructure is martensite, a small amount residual austenite and dispersed carbide.

Abstract: Prediction and control of welding distortion is an important stage to guarantee manufacturing quality of steel structures. Thermo-elasto-plastic finite element method is employed to analyze the model of "U" rib orthotropic plate. Through this method, inherent strain in the weld zone is extracted. Inherent strain obtained which is regarded as known conditions is put on the weld zone of "U" rib orthotropic plate. Elastic finite element analysis is employed to predict the welding distortion of the plate. According to the prediction result, control scheme of welding distortion is made and a curvilinear equation is provided. The equation elaborates the shape of the welding jig controlling welding distortion. Numerical simulation method is applied to analyze the control scheme and the steps of the method are given. The numerical simulation result meets the quality request of welding deformation control. The method provides important reference for the control of the welding distortion in complex components.

Abstract: The effect of wheel speed, axle load and track curve radius on wheel/rail adhesion properties under dry and water medium condition was investigated in this paper using JD-1 wheel/rail simulation facilities with Hertz simulation method, and then testing method of “four horizontals and three factors” was adopted to analyze the influence degree of speed, axle load and track curve radius on wheel/rail adhesion. Results from the experiment are that: The adhesion coefficient reached maximum at creep ratio of 1.5% under dry condition, and 1% under wet condition respectively; the adhesion coefficient under water medium condition occupy about a proportion of 32%-50% of that under dry condition. adhesion coefficient would reduce with speed increasing, axle load increasing and track curve radius decreasing under dry condition, and reduce with speed increasing, axle load decreasing and track curve radius decreasing under water medium condition; As far as influence degree of three testing factors which have effect on adhesion coefficient is concerned, axle load is the first one, then speed, finally track curve radius under dry condition, and speed is the first one, then axle load, finally track curve radius under water medium condition.

Abstract: The distribution of mechanical property in the weld zone of friction stir welded 7050 aluminum alloy joint along the plane perpendicular to the welding direction was experimentally investigated by the non-contact measurement method. The results show that the elastic modulus presents a W-shape distribution across the weld zone. The elastic modulus in the weld nugget zone is increased due to the grain refinement. In addition, the elastic modulus in the advancing side is slightly less than that in the retreating side possibly because of the relatively higher temperature in the advancing side during the welding process. The strength in the vicinity of weld center is decreased while the ductility is enhanced. The tensile strength and yield strength in the weld nugget zone and thermo-mechanically affected zone are significantly decreased while the elongation is increased due to the change of strengthening mechanism. In the heat affected zone the strength is decreased compared to the base material because the second phase grows up.

Abstract: In the paper, the effects of thermo-mechanical control process on microstructure and properties of oil country tubular goods by electrical resistance welding are analyzed. The TMCP parameters are optimized by Gleeble-1500 thermo-mechanical simulator, and industrial trial is carried out. The microstructures in the welded joints of original ERW OCTG are mainly composed of proeutectoid ferrite, pearlite and widmanstatten. In contrast, the welded joints of ERW OCTG treated by TMCP consist only of refined ferrite and pearlite. The higher low-temperature impact toughness and the better resistance to the grooving corrosion of the welded joints of ERW OCTG treated by TMCP could be attributed to removing welding residual stresses, homogenizing microstructure, eliminating porosity and refining grain. TMCP facilitates the performance optimization of welded joints so that the quality of the finished product can be improved.

Abstract: The corrosion behaviors of 304 stainless steel (304SS) which has been cut and 304SS which has not been cut in two different solutions were investigated using polarization curve and electrochemical impedance spectroscopy (EIS) methods. The results show that 304SS which has been cut and 304SS which has not been cut have the similar corrosion voltage in two different solutions. However, the corrosion velocity of 304SS which has been cut is more than 304SS which has not been cut both in the two solutions and the corrosion behaviors of two 304SS in the water solution are better than in the water which has little oil.

Abstract: Based on the production line technology of high-frequency welding H-beam steel, a High-frequency welding device which could be used in a H-beam less than 100mm steel was designed in this work. After virtual prototype established and kinematics Simulation was carried by Solidworks and Cosmos/motion respectively, the trajectory of contact terminal was defined. And the optimal vee angle, high frequency and some other technological parameter were determined through Ansys software, which provides important reference for the design of high-frequency welding H-beam steel.

Abstract: In order to investigate the effect of active fluxes on weld penetration, angular distortion and weld morphology in gas tungsten arc welding (GTAW), three types of oxide fluxes-CaO, TiO₂ and Al₂O₃-were used in the welding of 5mm think stainless steel plates. Those powders were applied through a thin layer of the flux to produce a bead on plate welds. The results showed that compared with conventional TIG welding, increased weld penetration and reduced angular distortion of the weld piece were obtained with the application of active fluxes. However, the weld morphology was not changed significantly when the powders were coated on the surface of steel. It was also found that each of the powders has a fittest range in penetration increment. Whether the rate of the coating run out of the range, the effects of these active fluxes on the increased weld penetration were not obvious. The CaO flux has a narrow effective range for deep penetration, while the Al₂O₃ powder does have no effect on A-TIG penetration. The mechanism of those different performances has not been found out. According to the investment, the mechanism of active fluxes for the increased weld penetration and reduced angular distortion is related to the contraction of the arc.