Effects of viscous flow on generation of thermal stress and strain during quenching of steel plates

Substantial improvements have been made recently in the quality of the mathematical models used to represent the generation of thermal stress and strain during the quenching of steel components. However, viscous processes have received little attention in these models, even though there is frequently sufficient time for creep processes to occur during a quench. The inclusion of stress–relaxation and creep effects in one such model has led to a marked improvement in the degree of agreement between the experimental and predicted residual–stress distributions obtained after an oil quench, at the expense of a modest reduction in the corresponding level of agreement after a water quench. The best correlation is obtained by the representation of stress–relaxation and creep effects by means of a standard linear solid model at temperatures above 230°C, with stress–relaxation rates a function of temperature only. Since the isothermal stress–relaxation tests indicated significant viscous processes at temperatures above 130°C, it is possible that the model could be further refined by consideration of the interaction of viscous processes that occur at different stages in the quench. Results are also presented of the predicted relationship between stress and strain at the surface and centre of a plate during quenching in both water and oil.

MST/3