Volgograd State Technical University (Volgograd, Russia):

Chubukov M. Yu., Post-graduate, Chair of Materials Technology
Rutskii D. V., Cand. Eng., Ass. Prof., Chair of Materials Technology

Zyuban N. A., Dr. Eng., Prof., Head of Chair of Materials Technology
Palatkina L. V., Cand. Eng., Ass. Prof., Chair of Materials Technology

E-mail (common): tecmat@vstu.ru

Volzhskiy Pipe Plant (Volzhskiy, Russia):

Uskov D. P., Head Specialist in Material Science, Central Plant Labour

The work is devoted to research of the structural features of surface oxide layers and microstructure of plugs after their operation. It was established that thickening of oxide layer occurs with increase of number of cycles of metal shell piercing, as well as variation of its phase composition. As soon as number of piercing cycles increases, thickness of oxide layers on the plug service rises from 102 to 528 μm. The detailed investigation of oxide layers using the methods of optical and scanning electronic microscopy has displayed that oxide layer of plugs consists of several sublayers: the surface area with dense structure and the internal oxide layer that is located close to metal and has stalagmite-shaped image. Increase of the number of piercing cycles also leads to appearance of the intermediate layer that is characterized by laminated structure of dark and light sections. X-ray microanalysis of oxide layers of plugs in the “chart” conditions has shown that these layers present themselves an oxide-metallic composition, including particles from oxides of iron, nickel, silicon and other alloying elements of plug steel composition, and these particles are located in chaotic mode. Increase of the number of piercing cycles supports the diffusion process of alloying elements inside the space between oxide layers, and it aids to elevate bonding forces between the layers.

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