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Vibration damping steel sheets (VDSS), which have sandwich structures with intermediate layers of resin, have been studied. The most important characteristics of VDSS for inner panels of automotive vehicles are the vibration damping properties, press formability and spot weldability. Vibration damping properties, which are quantified by loss factor,η, were influenced by both tanδ, which indicates damping capacity of resins, and elastic modulus of core resin. From a view point of vibration damping properties, resins with larger tanδ and relatively lower elastic modulus were favorable. Because these mechanical characteristics vary considerably with temperature, it is important to select the most suitable resin for the service temperature range. The relationship between noise reduction effect and loss factor of VDSS were also studied. It was experimentally confirmed that noise reduction effect of VDSS is proportional to the logarithm of their loss factor.

Galvannealed steel sheet (GA) is very extensively used for vehicle panels. However ζ-phase (FeZn13) in GA coat causes poor stamping formability. Previously, there were no easy methods to evaluate the influence of ζ-phase on the frictional characteristics other than the X-ray diffraction method. This study will discuss the development of a new testing method: Dr. STAMP Method that is both efficient and convenient with pin-on-disc tester.

Recently, many kinds of coated steel sheets are developed and used for automobile panels. Some of them show higher coefficient of friction and poorer formability than a cold rolled steel sheet. New polymer lubricating films are developed and proved to improve frictional characteristics of coated steel sheets in this study. The developed polymer lubricating films are applied to Electro Galvanized steel sheet and Hot Dip Galvannealed steel sheet, and coefficient of friction and formability of them are measured by using model dies. Different coefficients of friction are obtained by a change in a combination of components in a polymer lubricating film. As a result, the most suitable coefficient of friction is able to chose in forming conditions by the developed polymer lubricating films.

In order to attain the gauge reduction of outer body panels without spoiling the dent-resistance and formability, a bake-hardenable Al-killed steel sheet, named RBH-35, and has been developed in the conventional box-annealing process. RBH-35 is an 0.01% carbon, low manganese and rephosphorized Al-killed steel sheet retaining solute carbon of about 10 ppm. The steel exhibits high r-value, bake-hardenability of 40 MPa, ultimate tensile strength of above 350 MPa and substantially non-aging property. Results of stamping test of door outer panel showed that RBH-35 is the most suitable steel sheet for the thinning of outer body panels by about 10%. This paper reports the metallurgical features, mechanical properties and applications of the steel.

In order to help the gauge reduction of wheels and chassis parts of automobiles, a form-able and weldable hot rolled steel of 550 MPa grade, named FDP-55, has been developed. FDP-55 is an 0.14% C, 0.1% Si, 1.1% Mn and Nb free A1-killed steel obtained by controlled-cooling to a low coiling temperature on a runout table, and it is featured by ferrite-degenerated pearlite microstructure. Results of co-operative works with automotive makers showed that FDP-55 was successful in the application to wheels and chassis parts attaining the large weight reduction. This paper reports the metallurgical features and characteristics of the steel.