Evaluation of Impact Strength and Microstructure as Quality Criteria for Selected Materials

The article presents the results of analysis of the chemical composition, hardness, microstructure and toughness of selected structural materials. The focus is on the results of impact tests carried out on the 40H steel quenched and tempered at three different temperatures, on grey cast iron used in industrial practice (cast material for brake drums) and on ADI, all of them being considered representatives of the group of materials commonly used in the production of structural elements and finished products, including items for use in the automotive industry. The impact tests were performed at a reduced temperature (-20°C), at room temperature (20°C) and at elevated temperature (150°C), comparing the results obtained with the microstructure of materials tested. It has been shown that in the case of steel, the smallest changes in microstructure cause changes in toughness, while the effect of tempering temperature is in this case of secondary importance. It was also proved that under the conditions of ambient temperature and reduced temperature, better results were obtained for ADI. At elevated temperature, better results were obtained for grey iron castings.