Strength and plasticity of base material and heat-affected zone of CrMoV and CrMoVNi steels at temperatures up to 780 degC

Within weldability research of steels CrMoV and CrMoVNi some mechanical properties were assessed of the heat affected zone of the welded joints that contribute to annealing and underclad crack formation. Test are described in detail of measuring the mechanical properties of the base material and a simulated heat affected zone in dependence on temperature up to 780 degC. The isothermal test is used for assessing steel resistance to annealing crack formation. The objective of the relaxation test is to define how the heat affected zone is capable of relaxing residual stress during annealing. The fracture surfaces of the test bodies were subjected to fractographic analysis. The specimens can be said to principally show intergranular fracture. The results also show that the shear strength and the tensile strength of the heat affected zone maintained a relatively high value even at a temperature of 600 degC, this in both steels. The CrMoV steel is susceptible to tempering brittleness. At the same initial stress, the CrMoVNi steel is capable of relaxing residual stress higher by 20 to 50 MPa than the CrMoV steel within the same time in the temperature range 550 to 650 degC. (Z.M.). 10 figs., 3 tabs., 5 refs