INFLUENCE OF MANUFACTURING PROCESS ON CHEMICAL AND STRUCTURAL HOMOGENEITY OF WELDED PIPE SHEETS FOR TANKS AND VESSELS WORKING UNDER PRESSURE

摘要

The tests presented in the paper deal with rolling state inclusion analysis and the influence of heat treatment, sample direction, and sample type on impact strength characteristics. Heat treatment has generally resulted in better impact strength values. The heat treatment applied to the ferrito-perlitic structure has led to finer grains, with a good influence on impact strength values, compared with those obtained in rolling state. The annealing, followed by tempering has resulted in raising dislocation mobility, more energy for crack formation and propagation is necessary and the chance of cracking is lower. The values of impact strength, as function of sample processing direction have shown a certain anisotropy of characteristics. Heat treatment state also influences fracture appearance and the transition moment from ductile to brittle failure is moving to lower temperatures, compared to those corresponding to the rolling state.