Laser brazing with filler wire for galvanized steel sheets

The process properties and interface behavior of CO_2 laser brazing with automatic wire feed for galvanized steel sheets were investigated, in which the brazing filler metal was CuSi3 and no flux was used. As to the appearance quality of the brazing seams, the roles of the processing parameters, such as brazing speed, wire feeding rate, inclination and feeding direction of the wire, laser power, spot diameter and heating position, were assessed. The further investigation indicates that the behavior of the active elements Si, Mn and Zn are significantly influenced by energy input. At the interface, the microstructure of the base metal was composed of columnar crystals and the acicular α solid solution was found on the filler metal side.

Effect of surface roughness on the surface lubrication performance of galvanized steel sheets with a self-lubricated coating

Four kinds of galvanized steel sheets having different surface roughness values were used to prepare the steel sheets with a self-lubricated coating. The effects of surface roughness on the surface lubrication performance of the steel sheets were examined using a friction coefficient tester. Results revealed large dynamic friction coefficients for the galvanized steel sheets, which increased remarkably with surface roughness. Once the self-lubricated coating was applied, significant drops in the dynamic friction coefficients were measured. After the first stage of the friction test,the coefficients were almost unchanged, which reflected a weak dependence on the surface roughness of the self-lubricated steel sheets. However, the dynamic friction coefficients gradually increased as the test progressed, where these increase clearly correlated with the surface roughness of the self-lubricated steel sheets.

Properties of Baosteel inorganic-lubricant-coated galvanized steel sheet for automotive body panels

An inorganic lubrication treatment for a galvanized steel sheet was developed to improve the press formability of automotive body panels. The properties and application of Baosteel＇s inorganic-lubricant-coated galvanized steel sheet are demonstrated. Compared with galvanized steel sheets without the inorganic lubricant coating,the Baosteel inorganic-lubricant-coated galvanized steel sheet has a lower friction coefficient and excellent lubricating ability,more homogeneous tribological and stamping behaviors,lower sensitivity to stamping parameters,excellent spot weldability,good adhesivity,and perfect phosphate compatibility and paintability. These results verify that the Baosteel inorganic-lubricant-coated galvanized steel sheet has excellent press formability and a huge market application potential.

Effect of Cu Addition on the Microstructure and Mechanical Properties of U-MIG Welds on Galvanized Steel Sheets

Ultrasonic-assisted metal inert gas(U-MIG)welding experiments were performed to analyze the effect of Cu addition on the microstructure and mechanical properties of galvanized steel sheet welds,and first-principles calculations were undertaken to predict the effect of Cu on the mechanical properties ofα-Fe based structures.As shown by scanning electron microscopy analysis,Cu is conducive to the refinement and uniformity of the microstructure in the weld zone.Energy-dispersive spectrometry data indicated the presence of Cu in the welds after welding with Cu powder.The elastic moduli of the welds without and with Cu powder,obtained from nanoindentation tests,were(217.66±5.11)GPa and(223.13±9.12)GPa,respectively,which were close to the calculated results.The mechanical properties of the crystal structures ofα-Fe andα-Fe_(1.9)Cu_(0.1)were calculated using Materials Studio software.Both the experimental and calculated results showed that Cu doping reduced the bulk modulus of the weld but increased its shear modulus.

Evolution of appearance profile of hot-dip galvanized car-body steel sheet during deformation process

In recent years, the waterborne free intermediate coating process has been widely used in the automotive industry. Because the baking times and coating thickness are decreased, the surface covering capability of the painting process is reduced, which directly affects the appearance quality（ long-and short-wave values） of the body paint. Thus, there are correspondingly higher requirements for the white body surface profile prior to painting. The surface profile of the white body is mainly affected by the plate material, the surface profile, and the deformation process. So,the change rule for the surface profile during deformation of the steel plate is a key factor in coating appearance optimization. In this paper, we first analyze the typical deformation of the outer cover of a car body. Then ,we examine the change tendency of the surface profile of steel plates with respect to different deformation rates, specifically for a steel plate comprising a hot-dip galvanized bake-hardened steel sheet. Based on our analysis of the influence of the deformation on the coating appearance,we selected 3% ,5% ,and 8% deformation rates in this research. We found the roughness （Ra） value in the typical deformation range （3% -8% ） of the car body to exhibit a decreasing trend at first and then an increasing trend. The Ra value of the 8% deformation is not more than the original plate test value. When the Pc value of the original plate is in the lower range （ about 60）, it exhibits a slight increasing trend in the deformation process （3 % -8 % ）. And when the Pc value of the original plate is in the higher range （ about 120 ）, it exhibits no increasing trend in the deformation process （ 3% -8% ）. In contrast,the waviness （WCA） value in the car body＇s typical deformation range （3%-8%） shows a significant growth trend.

Effects of surface treatments of galvanized steels on projection welding procedure

A group of projection welding experiments and joints tension-shear tests are carried out for cold-rolled steel sheets, galvanized steel sheets (GSS) without treatment, GSS with phosphating and GSS with surface greasing, respectively. The experimental results are regressively analyzed on the computers, then the projection welded joint tension-shear strength curve and the perfect welding currents range of each material are obtained. The results show that surface treatments of galvanized steels have effects on their spot weldabilities. Among the four kinds of materials, GSS with surface greasing have the worst spot weldability, for they need higher welding current and have a narrow welding current range.