Use of Corrosion-Resistant Maraging Steels in Long-Lived Thread Pieces

The effect of isothermal holdings at 350, 500, 580, 660, and 780 degrees C during heating to various austenitizing temperatures on the grain size, aging processes, structural and mechanical properties, and the stress-strain curves of 03Kh11N10M2T-VD and 03Kh11N8M2F-VD maraging steels with 0.002% B is studied. X-ray diffraction analysis and metallographic examination are performed, and the corrosion and fatigue characteristics of these steels are determined. At the aged state with the maximum strength, the steels exhibit no strain-hardening ability upon tension and retain a high local plastic deformation during necking (psi <= 60%). Preliminary thermal-cycling treatment at 500-800 degrees C causes grain refinement and increases the plastic properties of the steels (the uniform elongation increases to 20%). Isothermal holding during heating to the austenitizing temperature affects an elastoplastic transition at a low tensile strain.