INVESTIGATING CHANGES IN THE DISLOCATION STRUCTURE OF 12Cr1MoV STEEL UNDER OPERATIONAL CONDITIONS.

The article provides the results of investigations into changes in the dislocation structure of 12Cr1MoV heat-resistant steel in the process of industrial operation in a range of working temperatures of 500-570 degree C and design stresses of 4. 4-7. 4 kgf/mm**2. The investigation was carried out on the metal from control sections of steam pipelines after operating periods of up to 78,000 h. The investigation of the dislocation structure of 12Cr1MoV steel by a metallographic method with the aid of an optical microscope has shown that the development of creep of the steel in the conditions of operation considered is the result of the complex interaction between the transverse deformation and the diffusion processes, and is connected with twinning of the grains, which form new sub-boundaries, and with the development of the polygonization structure and multiple slip.