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Influence of Material State on Austenitic Transformation in HSLA-Type Steel

Wojtacha Anna, Morawiec Mateusz, Opiela Marek

Advances in Science and Technology. Research Journal

2024

Vol. 18, no 4

66--75

The paper presents the results of research on the influence of the material condition – HSLA steel with Ti and Nb microadditions – on the course of the austenitic transformation. In order to determine the kinetics of phase transformations occur in steel during individual stages of the austenitic transformation, tests were carried out using a Bähr 805 A/D dilatometer. In order to determine the influence of hot plastic deformation on the course of the austenitic transformation, plastometric tests were carried out using the Gleeble 3800 thermomechanical simulator. For detailed microstructural analysis, microscopic examinations were carried out using the light microscope and the scanning electron microscope. The obtained results were compared with hardness measurements. The tests carried out showed significant differences in the course of the austenitic transformation and the values of critical temperatures for steel before and after using the plastic deformation. The Ac1 temperature for steel in the as-cast state is 850°C and the Ac3 temperature is 950°C. As the annealing temperature increases, the hardness increases from 210 HV100 for a temperature of 700°C to 260 HV100 for a temperature of 920°C. Knowledge about the phase transformations of supercooled austenite is extremely important, especially for newly developed steels, hence the aim of the work is to analyze the atypical course of the austenitic transformation of HSLA steels and to determine the influence of deformation on the austenitic transformation during heating.

Effect of Heat-treatment Parameters of Cast Iron GJS-X350NiMnCu7-3-2 on its Structure and Mechanical Properties

Medyński D., Janus A., Zaborski S.

Archives of Foundry Engineering

2017

Vol. 17, iss. 1

121--126

The paper presents influence of soaking parameters (temperature and time) on structure and mechanical properties of spheroidal graphite nickel-manganese-copper cast iron, containing: 7.2% Ni, 2.6% Mn and 2.4% Cu. Raw castings showed austenitic structure and relatively low hardness (150 HBW) guaranteeing their good machinability. Heat treatment consisted in soaking the castings within 400 to 600°C for 2 to 10 hours followed by air-cooling. In most cases, soaking caused changes in structure and, in consequence, an increase of hardness in comparison to raw castings. The highest hardness and tensile strength was obtained after soaking at 550°C for 6 hours. At the same time, decrease of the parameters related to plasticity of cast iron (elongation and impact strength) was observed. This resulted from the fact that, in these conditions, the largest fraction of fine-acicular ferrite with relatively high hardness (490 HV0.1) was created in the matrix. At lower temperatures and after shorter soaking times, hardness and tensile strength were lower because of smaller degree of austenite transformation. At higher temperatures and after longer soaking times, fine-dispersive ferrite was produced. That resulted in slightly lower material hardness.