SOME TRIBOLOGICAL ASPECTS OF Fe-Zn COATED STEEL SHEETS AT STAMPING PROCESSES

Abstract

Contribution presents results of study of tribological characteristics of Fe-Zn coated steel sheets. Experimental research was done using coatings with different alloying -under alloyed, optimal and slightly pre alloyed. The optimally alloyed coatings and the slightly prealloyed ones were annealed in order to reach different alloying level. Alloying level was evaluated by phase composition and % Fe in coating. Tribological properties such as surface microgeometry, abrasion, friction coefficient were analysed from the view of formability. Experimental results of strip drawn test were used for verification of strip-drawn test numerical simulation. Based on numerical simulation results, contact pressure on drawing die radius was observed.Keywords: Fe-Zn coatings, steel sheets, coating morphology, friction coefficient, numerical simulation IntroductionCurrent production in the automotive, consumer goods industry and also other industries must adapt to many; often mutually conflicting technical, economic and environmental requirements. On the one hand, customer demands for products performance, primarily for safety, reliability, corrosion resistance, driving dynamics, comfort and economy are growing; on the other hand, pressure to reduce emissions, higher productivity, eco-friendly production, reduction of maintenance costs and prices of products is increasing. The main innovative trends for increasing the performance of automobiles include reducing the weight of structural parts that contribute the most to the total weight of the car (body 26 %, 23 % undercarriage, motor 21 %, 22 % equipment, etc.). The effectiveness of this approach has been demonstrated by the results of the project ULSAB. For more than 80% of structural elements of the ULSAB body the builders have used high-strength steels with yield strength from 210 to 550 MPa, ultra-high strength steels with yield strength above 550 MPa, almost half of the weight of the body consists of laser-welded tailored blanks (tailored blanks) and sandwich materials [1,2]. In order to ensure the adequate lifetime of autobodies, majority of structural elements of ULSAB body are made of zinc coated sheets. Among the coated steel sheets are given the ratio between quality and the price of its irreplaceable galvanized sheets. During annealing after galvanization the transformation of the

Evaluation of selected properties of coatings in respect of risk elimination of surface damage of stamped parts

“…Based on the knowledge of the load rate and sample feed rate and the The friction coefficient was determined by the originally designed friction simulator, which allows simulating the deep-drawing process - Fig. 1 [24,25]. This modified friction simulator of the "friction jawsroller" type (designed for TIRATEST 2300 tensile machine) enables to model load of contact surfaces in two modes:…”

Analysis of the galvanised steel sheets resistance to corrosion after plastic deformation

“…Železo-zinkové povlaky (galvannealed -GA) sa získavajú niekoľkosekundovým žíhaním pozinkovaných oceľových plechov pri teplote 500-565°C v peci umiestnenej na výstupe z pozinkovacej vane [5,6]. Zinkovo-horčíkovo-hliníkové povlaky sa vyrábajú žiarovým pozinkovaním ocelí v zinkovej zliatine, obsahujúcej 0,8 ÷1,0 % Mg a 0,8 ÷1,0 % Al.…”

Experimental Evaluation of Draw Bead Coefficient of Friction

“…the applied pressure load, surface roughness -both of sheet metal and tool and process conditions (static or dynamic loads, forming temperature, sliding speed) [1][2][3][4]. The friction mechanism also depends on the material of the tool and the relative hardness of the surface of the specimens to the tool materials [5,6]. In the sheet metal forming of parts with complex geometry, the magnitude and distribution of friction affect metal flow, part defects and production costs [7].…”