Magnitogorsk State Technical University (Magnitogorsk, Russia):

A. M. Pesin, Dr. Eng., Prof., Dept. of Materials Processing Technologies, e-mail: pesin@bk.ru
T. V. Shveyova, Cand. Eng., Associate Prof., Research Engineer, Scientific and Research Center, e-mail: asttv@mail.ru
D. O. Pustovoitov, Cand. Eng., Associate Prof., Dept. of Materials Processing Technologies, e-mail: pustovoitov_den@mail.ru

Comparative data have been presented and the example of 35, 40Kh and 30KhN steels shows the advantage of hot-deformed steel semifinished products over cast ones in terms of mechanical properties. The relationship between the resistance of 40Kh steel to brittle fracture at various temperatures and the degree of hot plastic deformation of the metal was shown. High impact toughness in the temperature range from +20 °C to –80 °C is reached for steel 40Kh after compression of the cast metal with a degree of not less than 44 times. When steel is smelted from scrap metal, its structure and properties are signifi cantly affected by impurities of heritable chemical elements, primarily aluminum and vanadium. Heat treatment technologies for cast and deformed semi-finished products from 20GL and 20KhGNM steels were developed and proposed for use in production. For 20GL steel cast products, an effective and easily implemented in the production technology of heat treatment has been proposed. Due to the regulated temperature and time parameters during heating and cooling of castings, a fine-grained structure and a ferrite-pearlite structure in the steel are achieved. Information is provided on the degree of additional deformation of rolled steel in the manufacture of eight forgings for truck parts. Heat treatment of inhomogeneously deformed forgings, including homogenization, austenitization and tempering, ensures the stable formation of a given structure and high mechanical properties over the entire cross section of the products. Examples of the negative influence of segregation in steel on the crack resistance of products were given, especially if the cracks come to the surface of the part.

The studies were carried out at the expense of a grant of the Russian Science Foundation (agreement No. 15-19-10030-P dated April 13, 2018), as well as within the framework of the implementation of Decree of the Government of the Russian Federation dated April 9, 2010 No. 220 (agreement No. 074-02-2018 -329 dated May 16, 2018).

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