Effects of External Electric Field on AlN Precipitation and Recrystallization Texture of Deep-drawing 08Al Killed Steel Sheet

The effects of an electric field on AIN precipitation and recrystallization texture were investigated. Cold-rolled 08Al killed steel sheets were annealed at 550℃ according to the two-step processes, for various maintaining times, with and without applying an electric field. It was found that the electric field promotes the precipitation of the second phase （AlN particles）, strengthens the γ-fiber and weakens the α-fiber texture component in the recrystallized specimens. A possible explanation for the reinforcement of γ-fiber texture by the electric field is that the second phase AIN particle promotes the growth of γ-fiber at the expense of differently oriented grains.

Analysis of edge microstructural characteristics and stamping formability of low carbon pickled steel sheets

The microstructural characteristics and formability at the edges of low carbon pickled steel sheets have been investigated based on the generation of earing and cracking defects while drawing. The microstructure of the edge features coarse grains and mixed sized grains. The strength of the sheet edge is slightly lower than that at the center. Besides, the formability is obviously worsened. The plastic strain ratios along the longitudinal and transverse orientations are 0.31 and 0.6, respectively, with distinct anisotropy. The plastic strain ratio at the edge is obviously lower than that at the middle of the steel sheet. The observed microstructural characteristics and mechanical properties at the edge of the steel sheet can be attributed to the lower rolling temperature in the two-phase region of pro-eutectoid ferrite and austenite. These differences in microstructure and mechanical properties at the edge of the steel sheet lead to the generation of earing and cracking defects while drawing. The microstructure and mechanical properties at the edge of low carbon pickled steel sheets can be improved via the optimization of the rolling process and the adjustment of chemical composition.

Experimental and finite element analysis for fracture of coating layer of galvannealed steel sheet

Mechanical properties of galvannealed (GA) steel sheet used for automotive exposed panel and predicted failure phenomenon of its coating layer were evaluated using finite element method. V-bending test was performed to understand better the fracture of coating layer of GA steel sheet during plastic deformation. Yield strength of the coating layer was calculated by using a relative difference between hardness of coating layer measured from the nano-indentation test and that of substrate. To measure shearing strength at the interface between substrate and coating layer, shearing test with two specimens attached by an adhesive was carried out. Using the mechanical properties measured, a series of finite element analyses coupled with a failure model was performed. Results reveal that the fracture of coating layer occurs in an irregular manner at the region where compressive deformation is dominant. Meanwhile, a series of vertical cracks perpendicular to material surface are observed at the tensile stressed-region. It is found that 0.26-0.28 of local equivalent plastic strain exists at the coating and substrate at the beginning of failure. The fracture of coating layer depends on ductility of the coating layer considerably as well.

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.

Properties,Microstructures and Precipitate Morphology of Hot-rolled Interstital-Free(IF)Steel Sheets

In order to simplify production process and to decrease production cost of thicker cold-rolled iF steel sheets for deep drawing applications, a new hot-rolled IF steel sheet is developed through hot-rolling in or region. In this paper, properties, microstructures and precipitate morphology of hot-rolled iF steel sheets are described..

Magnetic Properties and Workability of 6.5% Si Steel Sheet Manufactured by Siliconizing Process

A siliconizing process to manufacture 6.5% Si steel sheet has been developed. Electric components, such as transformers and reactors are made easily from 6.5% Si steel sheet. However, improved workability is desirable to increase the applications. Therefore the improvement of workability of 6.5% Si steel sheet was investigated, and the results were obtained as follows: (a) workability of 6.5% Si steel sheet is deteriorated by grain boundary oxidization, (b) grain boundary oxidization can be restrained by the addition of C. Workability and magnetic properties of 6.5% Si steel sheet with C addition are discussed. Furthermore, it was found that the workability of high Si steel sheet was improved remarkably by varying the Si content gradient along the thickness without deterioration of high frequency magnetic properties. This newly developed magnetic gradient high Si steel sheet is also discussed.

Recent Developments in the Study on Oriented Silicon Steel Sheets

Over the past several decades, the texture, properties and manufacture of quality silicon steels have been investigated for application in magnetic devices requiring magnetically soft materials, such as transformers, inductive devices, etc. Most recently, the factors effecting the texture and magnetic properties, e.g. impurities, rolling process and annealing process, have been greatly studied. The benefits of this study are that low core loss silicon steels with stable high-performance can be obtained through an economic production process. This review is intended to summarize the recent developments in the texture, properties, manufacture and application of oriented silicon steel sheets.

Failure Mechanism of Laminated Damping Steel Sheet during Tensile-Shearing

The tensile-shear failure zone of the laminated damping steel sheet was investigated by scanning electron microscopy and X-ray photoelectron spectroscopy. It is found that there exists cohesive failure in polymer sandwich and sub-boundary failure between the steel sheet and the polymer. The sub-boundary layer is dominantly polymer material. The tensile-shear failure of the laminated damping steel sheet is a process during which the crazes form, grow up and merge into cracks.

Texture Characteristics of Thin Grain Oriented Silicon Steel Sheet Produced by Cross Shear Rolling

Commercial grain oriented silicon steel was cold rolled to thickness from 0.06 to 0.10 mm by cross shear rolling, then annealed in vacuum or a hydrogen atmosphere furnace. Deformation textures of the sheets were researched by ODF method and reverse pole figure quantitative analyses. The results indicate that: in the condition of the cross shear rolling, the deformation texture of rolled sheet is generally similar to that of conventional rolled sheet, however, the texture distribution through the thickness is asymmetrical. With mismatch speed ratio increasing, the amount of Goss texture increases. With reduction ratio increasing, the intensity of γ-fiber becomes strong.

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.

Study on the formation of intermetallic phases in the new type of Zn-Mg coatings on steel sheets

Zn-Mg alloy coatings were obtained by physical vapor deposition （PVD） on electroplated steel sheets. Study on the formation of intermetallic phases in the coatings was conducted through the use of X-ray diffraction （XRD） ,scanning electron microscope （SEM） and glow discharge optical emission spectrometry （GDOES）. It is found that MgZn2 is the main Zn-Mg alloy phase formed after heat treatment. The formation of Mg-Zn intermetallic phases is controlled not only by thermodynamics, but also by kinetics. MgZn2 has different morphologies, such as laminar structure,porous structure and floc-like structure,which are mainly determined by the annealing temperature. Obvious diffusion of Mg starts at 350 ℃, and the diffusion of iron increases significantly when the temperature is elevated to 380℃.

Microstructure and texture evolution of cold-rolled deep-drawing steel sheet during annealing

In accordance with experimental results about the annealing microstructure and texture of cold-rolled deep- drawing sheet based on the compact strip production （CSP） process, a two-dimensional cellular automation simulation model, considering real space and time scale, was established to simulate recrystallization and grain growth during the actual batch annealing process. The simulation results show that pancaked grains form during recrystallization. （111} advantageous texture components become the main parts of the recrystallization texture. After grain growth, the pancaked grains coarsen gradually. The content of （111} advantageous texture components in the annealing texture increases from 55vo1% to 65vo1%; meanwhile, the contents of {112}〈110〉 and {100}〈110〉 texture components decrease by 4% and 8%, respectively, compared with the recrystallization texture. The simulation results of microstructure and texture evolution are also consistent with the experimental ones, proving the accuracy and usefulness of the model.

TENSILE-SHEAR STRENGTH AND BREAKING MORPHOLOGY FOR VIBRATION DAMPING LAMINATED STEEL SHEET

The phenolic resin-chloroprene nthher was used for sandwich in manufueturing the vibra-tion damping laminated steel sheet (also calied laminated sheet), Il is a metal matrix com-posite. The tensie-shear tests have been conducted over a range of temperatures from 20C to 150C and at the strain rates from 1.67× 10 ^(5) to 1.67× 10^(-2)s^(-1). The results show that test temperature will significaiilly affect the tensile shear strength of laminated sheet. and a minimal strength and a minimal activation energy occur near 80C . The tensile-shear breaking morphology of laminated sheet varies with strain rate and test temjteralurc.

Dislocation Densites of Deformed Steel Sheets Based on Positron Annihilation

The variation regularity of dislocation densites of some deformed steel sheets under three kinds of strainpaths as uniaxial tension, plane strain and equal biaxial stretching was investigated by means of positron lifetimespectrum and Doppler-broadening techniques. The results show that the increasing rate of dislocation densites isrelated to the plastic strain path. A relationship between the increasing rate of micro-defects, macro-instability andforming limits during the process of steel sheet forming was got based on analyzing the mechanism of dislocationdensity increasing under different stress-strain condihons.

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.

Self-cleaning performance of a self-cleaning pre-coated steel sheet in an industrial environment

A type of self-cleaning pre-coated steel sheet with excellent self-cleaning performance was developed using hydrophilic surface treatment technology. To understand the self-cleaning properties of this pre-coated steel sheet in an industrial environment, the Jiangjin natural environmental test station was chosen as the outdoor exposure test to be conducted, and the self-cleaning performance of the steel sheet was studied by measuring the water contact angle, stain resistance factor, color difference, and gloss of the steel sheet during the outdoor exposure test. The water contact angle of the self-cleaning steel sheet quickly decreased from 84° to 29° during the outdoor exposure test, and the steel sheet showed excellent hydrophilic properties, which were beneficial to the spread of rain drops and detrimental to the accumulation of the surface pollutants. After an outdoor exposure of 12 months,the self-cleaning steel sheet had a higher stain resistance and cleaner surface than the comparison sample sheet, demonstrating its excellent self-cleaning properties. Moreover, the color difference and gloss rate of the self-cleaning steel ＇sheet were similar to those of the pre-coated steel sheet without hydrophilic surface treatment. Therefore, the hydrophilic surface treatment technology used in this study did not affect the anti-aging property of the self-cleaning steel sheet.

The corrosive behaviors of GI and IF steel sheets in salt water drops

The corrosive behaviors of hot-dip galvanized steel （G I） sheets and the corresponding interstitial free （IF） steel base sheets for use in automobiles were investigated by the classical salt water drop （SWD） test at room temperature. The corrosive processes and products were observed and analyzed through morphological observation, a scanning electronic microscope （SEM） and an energy dispersive spectrum （EDS）. The results show that the anodic and cathode sites can be distinguished clearly during and after the test. The propagation of rusting, and the color, distribution and composition of the final corrosive products of the two kinds of materials are quite different. The SWD corrosive mechanisms of steel with and without galvanized coating are both discussed in this paper.

The production and practice of cold-rolled steel sheets for automobile

Shougang Group has carried out a strategic structure adjustment in order to realize the promise of Chinese people to the Olympic Games.Automotive sheets are chosen as a type of strategic product and an engine to upgrade enterprise management,technology and operation to reach the top international level during the transition from long products to steel sheets in Shougang Group.Since 2006,Shougang Group has made an elaborate preparation on steel sheet culture,production line construction,technology import,pilot plant and talent reserve.It lays the foundation for the development of automotive sheets.The developing history of cold rolled automotive sheets is reviewed and the research and development of cold rolled automotive sheets, tackling key problem of defect on surface and the latest progress of automotive sheets construction are described in this paper.The main contents were given as follows:①The products of automotive sheets realize zero breakthrough in Shougang Group.Monthly output was 300 ton in January,2009 and it increased to 48 000 ton in June,2010.The ratio of IF steel sheets increases to 70%from 40%.The proportion of outside panel in automotive sheets occupys more than 15%.②A high emulational pilot plant is used as a product developing platform to develop successfully automotive sheets with 1 000 MPa and below.It guarantees that the industrial development of DP and TRIP sheets gets success at a time.It covers continuous annealing sheets with tensile strength≤780 MPa and galvanizing sheets with tensile strength≤590 MPa.③Individual design is used to meet special requirement of customer.Shougang owns 23 inner brands of LCAK and IF steels.It insures that the grades of yield strength cover whole range from 120 to 270 MPa.It keeps the stabilization of steel performance by means of chemical composition control and high accuracy rolling technology.For example,the strength of soft steel fluctuates within±15 MPa.④The steel sheets with surface grade O5 are produced steadily by solving forming striation of IF steel,grain coarse on surface,edge curling skin and mountains - and - waters painting defects.⑤The safeguard mechanism on quality of products is improved steadily and the output of automotive sheets and outside panel increases greatly by building consistency quality management system、information - system and customer service system.

The development of advanced Cr-free organic composite coated electrogalvanized steel sheet with excellent grounding property

In recent years,the concern about environmental protection is increasing on a world scale.Major manufacturers of home appliances and OA equipment have introduced so-called 'green procurement schemes' for reducing environmentally harmful substances in manufacturing process and end products. Under such background,a new type of chromate-free organic composite coated electro-galvanized steel sheet with high conductivity was developed by Baosteel,which meets the EU RoHS Directive(Restriction of the Hazardous Substances) and other related laws and regulations on environmental safety.It also provides excellent surface electrical conductivity,corrosion resistance,fingerprint resistance,solvent resistance,coating adhesion, heat resistance,formability and other special properties to meet the demand of manufacture's process of OA machine. Compared with previously developed anti-fingerprinting coated electro-galvanized steel sheet,this newly developed product has a good balance between high corrosion resistance(time to 5%white rust in salt spray test is 120 h for flat panel and 72 h for worked potion) and conductivity(surface electro-resistivity in accordance with LOREAST is less than 0.1 milliohm ) due to the special design of coating's structure.Besides,It also provides the properties of grounding and shielding against electromagnetic waves.The evaluation of surface performances of new product showed that it is comparable or even better than the similar products. Currently,the newly developed product has been commercialized. In this paper,the major properties are discussed,such as corrosion resistance,surface electrical conductivity, fingerprint resistance,solvent resistance,coating adhesion(ink/melamine alkyd paint),heat resistance and formability.Furthermore,the application is also briefly described.

Characteristics and application of Baosteel's Cr-free ultrathick J coat for non-oriented silicon steel sheets

Baosteel＇ s Cr-free ultrathick J coat for non-oriented silicon steel sheets has excellent insulation performance and has been successfully applied to middle and large scale electric power trains and wind electric power devices, which have stricter requirements than typical for coat insulation. In this paper, the characteristics and application of this type of coating for non-oriented silicon steel sheets were described in detail.