The influence of temperature-time parameter of welded joints thermal treatment on strength-related characteristics of chromium-molybdenum and low-alloy manganese steels

The article deals with the analysis of the dependence of strength-related characteristics of welded joints from chromium-molybdenum steel (ASTM A335 Grd. P5) and low-alloy manganese steel (S355J2G3 EN10025-2) upon the parameters of heat treatment. Steel mechanical properties after post-weld heat treatment were analyzed. Chromium-molybdenum (Cr -5 %) steel and structural low-alloy manganese steel (Mn -1.4 %) was selected as a target. The steels of various classes widely applicable in oil industry were selected. At the beginning, samples were welded applying the same process. When welded, all the samples were heat treated. Tempering for each sample was performed by applying different temperature and exposure time. For analysis systemization the parameter of temperature-time P was applied. It was calculated for each heat treatment mode. After post-weld heat treatment each sample was tested subject to tensile and impact strength. P-dependence of mechanical properties of each steel sample was examined. It was determined that tensile strength and impact strength decreases by increasing P value. It showed the drop of mechanical properties value upon considerable increase of tempering temperature or application of a very long exposure time.