EFFECT OF STRAIN AGING ON THE PROPERTIES OF HIGH-STRENGTH STEEL 38Kh5MSFA

摘要

1. Steel 38Kh5MSFA subjected to low tensile deformations (0.6 - 1.2 percent) and subsequent aging is susceptible too strain aging, which manifests itself through an elevated yield strength and ultimate rupture strength and diminished uniform elongation. The effect of strain aging is the most vivid in steels with an initial structure of low-tempered martensite. After deformation with degree epsilon = 0.6 percent the conventional yield strength sigma_(0.1) increases by 300 - 350 MPa; after aging at 300 deg C it increases by another 150 - 200 MPa; the uniform elongation in this case decreases virtually to zero. Strain aging of the steel in a high-tempered state (560 - 600 deg C) develops weakly. The effect of the strain aging increases when the degree of the deformation increases to 1.2 percent and the aging temperature grows. The aging process occurs rapidly; at 150 deg C it finishes in 12 - 15 min; at 300 deg C it finishes in 3 min.2. The decrease in the carbon content in steel 38Kh5MSFA to 0.25 percent does not affect the strain aging under deformations of up to 1.2 percent.3. Low plastic tensile deformations with a degree of up to 1.2 percent and subsequent aging at 300 deg C do not decrease the resistance to brittle fracture and corrosion cracking of steel 38Kh5MSFA.4. The presence of residual strain of up to 0.7 percent in the shell and subsequent aging at 300 deg C did not diminish the structural strength of experimental tanks from steel 38Kh5MSFA.