Study of residual stresses after steel quenching with vegetable oils

Although quenching is necessary to increase the mechanical properties of steel, this process is often accompanied by high thermal stresses and transformation stresses which may lead to high residual stresses and distortions and possible cracking. Therefore, it is desirable to develop quenching processes that maximize the material properties while minimizing the residual stresses and distortions. This means that there is often a compromise between the factors involved to assure overall optimal process performance. The objective of this work was to measure and compare the experimental results of residual stresses that arise after quenching AISI 4140 steel grade into four different quenching fluids. Quenching was performed with 3 soybean derived oils and one fully formulated commercially available petroleum-based oil. Residual stresses were experimentally determined on cylindrical samples by two different methods: X-ray analysis and hole-drilling method according to ASTM E837-08. A detailed analysis of the residual stresses was carried out. The obtained results were related to the experimental heat transfer coefficient and viscosity of each fluid.