Search Results

The number of hot stamped components has been steadily increasing in the automotive industry. Press hardened steels (PHS) are generally used in hot stamping because, at the end of the process, the steel may achieve a tensile strength about 1,500 MPa. The hot stamping process consists of heating the steel blank at total austenitization temperatures and transferring it into the press tooling for forming and quenching simultaneously, and then to obtain a fully martensitic transformation. This transference step, from the furnace to the press, is a critical stage since it might promote steel oxidation. The application of metallic coatings avoids this event. The AlSi coating has been the most applied system on steel. However, alternative coatings, as ZnNi, are under development to keep up with the high demand.

This paper reports the experimental efforts in recording the 2-dimensional temperature distribution on autogenous thin plates of UNS S32304 steel during welding. The butt-welded autogenous joints were experimentally performed by the GTAW (Gas Tungsten Arc Welding) process with either argon or argon-2%nitrogen atmospheres. The temperatures cycles were recorded by means of thermocouples embedded by spot welding on the plate's surfaces and connected to a multi-channel data acquisition system. The laser flash method (LFM) was also used for the determination thermal diffusivity of the material in the thickness direction. The temperature curves suggest a relationship between the microstructures in the solidified and the heat affected zone with the diffusivity variation. This is a region where there had been a major incidence of heat. The obtained results validate the reliability of the experimental used apparatus.

The current study shows important results obtained by a new technique of residual stress virtual evaluation in automotive components for improving the development and quality of new products, aiming the structural performance, mass and cost reductions. The approaching those virtual results were adjusted by metallurgic data obtained in metallography, mechanical and chemical analysis. As part of this proposal, an automotive aluminum wheel belong to current production was evaluated in accordance with data acquired in the wheel manufacturing process. It was taking in account the real information of casting process parameters and the metallurgic information obtained in laboratorial tests. In this work, the results show that product residual stresses shall be considerate and evaluated during design phases as improving proposal, new technical concerns and quality improving.

The current study proposes to approach the fatigue behavior of stabilizer bars and specimens manufactured in quenched / tempered and as-received SAE5160 steels with and without a surface micro-notch. Some S-N specimens and stabilizer bars were shot-peened to improve the fatigue strength due to creation of compressive surface residue stresses and by surface plastic strain and others samples received a surface micro-notch of 0.3 mm depth introduced by EDM process. The crack growth evaluation at micro-notch was made comparatively with da/dN-ΔK curves in CT specimens. The proposed experimental study consists of comparative analysis of da/dN-ΔK and S-N curves, fractographic and, metallographic analysis, stabilizer bar bench tests, and after that, it is intended to show the relevant aspects of two microstructural classes currently specified for stabilizer bars, the beneficial effects obtained by shot peening and the bad influences of surface micro-notches.

The current study has the proposal to approach the differences in dynamic behavior between camshaft manufactured in the traditional gray cast iron and an alloyed gray cast iron with the improvement on mechanical properties in order to stresses found on roller finger follower applied systems. The main objective of this paper is to show that camshaft made of modified gray cast iron and heat treated through the remelting process is still a good solution for application with roller finger followers systems which requires higher wear resistance standards. The proposed experimental study consists of comparative analysis of microstructure and hardness, dynamometers tests, dimensional measurements of camshafts, and after that, intends to show the higher performance of this manufacturing process in more severe applications of internal combustion engines.

The current study has the proposal to investigate the differences in fatigue behavior between stabilizer bar manufactured in quenched & tempered and normalized SAE5160 steels. As it known, quenched & tempered stabilizer bars have higher mechanical and fatigue strengths, on the other hand, they are more expensive. Besides that, this type of part still receives a shot peening surface treatment to improve the fatigue strength due to creation of compressive surface residual stresses and by surface plastic strain. The previous subjects have affected directly the fatigue crack nucleation, then, in order to reduce the nucleation stage and study mainly the growth stage, a micro-notch (short crack) was introduced by EDM (Electric Discharge Machine) process on samples and stabilizer bars.

This work presents aspects related to research and development of high-speed steels for valve seat inserts application. Five series of materials were evaluated: high speed steel M3/2 infiltrated with copper during sintering; high speed steel M3/2 with Cu3P addition; high speed steel M3/2 with Cu3P addition and further copper infiltrated during sintering; high speed steel M3/2 mixed with iron powder; high speed steel M3/2 mixed with iron powder and niobium carbide. The physical and mechanical properties of the evaluated high-speed steels are presented in terms of densification, hardness, and radial mechanical strength. These properties are compared according to the materials processing and heat treatment.