Papers by Keyword: Deep-Drawability

Abstract: One of the main aims of automotive developers is vehicle weight reduction. There are many well known ways related to weight reduction, for example using thinner and higher strength sheet materials, or using of formed tubes as load-bearing elements in car body structures. In the field of modern automotive industry we must not forget that the heavy loaded, and in passenger-safety aspect relevant elements frequently consist of tailor welded blanks (TWBs). The components could have different strength or thickness or coatings too. Therefore, certain segments of the welded elements could behave differently during forming. Generally the higher strength coupled with less formability, but in the case of welded blanks, the interaction of each parts are unknown in many aspects.This paper presents the results of the experimental work, carried out to evaluate the drawability of tailor welded blanks. The welded blanks were prepared by laser beam welding technology. The blanks consisted of a well drawing component, marked DC04, and a high strength steel component. The applied high strength steels are DP600, DP800 and DP1000 types. Our current object was to determine some basic parameters of deep-drawability as a typical sheet metal forming operation. It can be stated that as the strength ratio (SR) is increasing between the segments, the limiting drawing ratio is decreasing.

Abstract: Interstitial-free (IF) steel has excellent deep-drawability and was used widely in automotive industry. High strength IF-steel is that some phosphorus was put in common IF-steel to improve its strength without destroying the deep-drawability [1]. Microstructure and grain boundary character strongly affect the deep-drawability of high strength IF-steel, it is an obligatory task to test those characters. The technique of Electron Backscatter Diffraction (EBSD) can reveal the microtexture and detailed orientation distribution of grains from a single EBSD map, as a powerful instrument, EBSD was used widely in materials research from last decade [2]. Many researches have been focused on the texture evolution and recrystallization phenomena of high strength IF-steels [3,4], but the microtexture and grain boundary characters of warm-rolled high strength IF-steels was not fully investigated. The present study was aimed at researching the microtexture characters of a commercial high strength IF-steels under different warm-rolled temperature using EBSD technique, the microstructure and grain boundary character were analyzed systemically, and the relationship between the microstructure and deep-drawability was discussed.

Abstract: The ferritic rolling strategy allows for the production of two different hot strip grades, a "soft" and a "hard" hot strip. The "soft" hot strip is rolled in the upper ferrite region and a sufficiently high coiling temperature ensures direct recrystallisation in the coil. The "hard" hot strip is rolled at relatively lower temperatures in the ferrite temperature region and exhibits a strained microstructure with a desirable rolling texture. Furthermore, these ferritic rolled hot strips can be used as initial strip for subsequent cold rolling. The current investigation focuses on the development of the recrystallisation texture of cold rolled and annealed ferritic rolled hot strip for different cold reductions. For this purpose "soft" and "hard" hot strips were produced on a laboratory hot rolling mill. These strips were cold rolled with a total reduction of 40 to 80% to a final thickness of 0.5mm. Subsequently the strips were subjected to simulated continuous annealing, using a salt bath furnace. The macro texture of both types of specimens was measured and correlated to the mechanical properties, including the Lankford values. A very different development of the recrystallisation texture and hence mechanical properties has been observed. However, both grades yielded improved deep-drawing properties.