Improving the Inner Surface State of Thick-Walled Tubes by Heat Treatments with Internal Quenching Considering a Simulation Based Optimization

Abstract

Internal Quenching is an innovative heat treatment method for difficult to access component sections. Especially, the microstructure, as well as the residual stress state at inner surfaces, of thick-walled tubes can be adjusted with the presented flexible heat treatment process. Based on multiphysical FE-models of two different steels, a simulative optimization study, considering different internal quenching strategies, was performed in order to find the optimal cooling conditions. The focus hereby was on the adjustment of a martensitic inner surface with high compressive residual stresses. The simulatively determined optimal cooling strategies were carried out experimentally and analyzed. A good agreement of the resulting hardness and residual stresses was achieved, validating the presented Fe-model of the Internal Quenching process. The shown results also indicate that the arising inner surface state is very sensitive to the transformation behavior of the used steel. Furthermore, the presented study shows that a preliminary simulative consideration of the heat treatment process helps to evaluate significant effects, reducing the experimental effort and time.

Experimental and numerical investigation of residual stress distribution in Al-6061 tubes under using tubular channel angular pressing process by new trapezoidal channel

“…7 In another study, Kamal et al employed the Sachs technique to specify the residual stresses in SS304 thick-walled autofrettaged cylinders and indicated that the compressive residual stresses cause an increase in the hardness of internal tube surface and the tensile residual stresses cause a decrease in the hardness of external tube surface. 8 Recently, Mu¨hl et al 9 used the Sachs technique to determine the residual stresses of thick-walled tubes. The Sachs method can also be utilized to specify the axisymmetric residual stresses in the SPD techniques.…”