Effect of Low-Temperature Annealings on the Change in the Level of Microdamage of Sheets of the Dual DP-600 Steel

Abstract

Abstarct

—The effect of the annealing temperature on the texture state and level of damage D of sheets of the steel DP600 (0.10% С, 0.15% Si, 1.4% Mn, 0.007% Р, 0.008% S, 0,009% N, 0.02–0.06% Al, 1% Cr–Mo–Ni) with a ferritic–martensitic structure and a texture of recrystallization and cold rolling has been studied in this work. The level of D was estimated based on the results of measurements of the Young’s modulus E and direct electron-microscopic observations. An increase in E after annealings in the 220–275°С temperature range stops; yield plateaus appear in the tensile curves, the yield stress increases, and the yield strength decreases in all directions of measurements. A redistribution of orientations can be seen in the texture, which does not affect the magnitude of E. These annealings are associated with the least level of D of the steel sheets, which after prolonged annealings can be considered to be “conditionally undamaged.” Further annealings (to 400°С) change the texture state of the sheets (three texture characteristics are increased) and the values of E in different directions and increase the level of damage. The values of D show up an anisotropy similar to that characteristic of E.