Volgograd State Technical University (Volgograd, Russia):

M. Yu. Chubukov, Post-graduate, the Chair “Technology of Materials”,
D. V. Rutskiy, Dr. Eng., Ass. Prof., the Chair “Technology of Materials”,
N. A. Zyuban, Dr. Eng., Ass. Prof., Head of the Chair “Technology of Materials”, e-mail: tecmat@vstu.ru

Volzskiy Pipe Plant (Volzhskiy, Russia):
D. P. Uskov, Head Specialist on Material Science

It is established in this work that the forged piercing plug is characterized by more favorable macrostructure (lack of a holes and shrinkable friability, existence of a fine microstructure) in comparison with the cast one. The positive effect is reached by comminution of structure during deformation and it can be reduced at smelting stage due to formation of nonmetallic inclusions. It is shown that forged piercing plug has larger contamination by impurity nonmetallic inclusions, and it reduces quality of piercing plugs. The used annealing mode allows to receive an oxide layer no more than 155 microns thick with favorable development of structure of internal and superficial oxide layers and with strong coupling with the main metal layer; however, this layer thickness is obviously insufficient. The research on the electronic scanning microscope has revealed structure of a boundary layer adjacent to a metal surface. It has a structure in the form of stalagmites, and represents the oxide-metal composition containing chaotically located particles from oxides of iron and nickel oxides and other alloying elements being a part of steel composition. The method of piercing plugs production (molding in a sandy-argillaceous form or machining of forged preparation) don't influence on thickness and composition of oxide layers formed during annealing.

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