South Ural State University ( Chelyabinsk, Russia):

A. N. Maznichevsky, Post-graduate Student, Dept. of Materials Science and Physical-Chemistry of Materials, e-mail: chiefteh@lasmet.ru
Yu. N. Goikhenberg, Dr. Eng., Prof., e-mail: goikhenbergyn@susu.ru

Lasmet Co. (Chelyabinsk, Russia):
R. V. Sprikut, Director of Lasmet Co., e-mail: mail@lasmet.ru

The effect of nitrogen (up to 0.3% (wt.) on the structure, mechanical and technological properties, as well as the corrosion resistance of chromium-nickel-manganese steel 03Kh20N9G3A0.30 has been studied. It has been established that the introduction of nitrogen into steel leads to a change in the structure of the ingot, namely, to a decrease in the width of the columnar zone and an increase in the zone of equiaxed crystallites under conditions of small cross sections. In addition, the austenite grains of the cast metal are refined. It is shown that an increase in the nitrogen concentration to 0.3% (wt.) leads to a signifi cant increase in strength properties (by 50–70%) with practically unchanged steel ductility under test conditions at room temperature. An increase in the test temperature leads to a gradual convergence of the levels of strength properties of steels 03Kh20N9G3A0.30 and 03Kh18N11 and a significant decrease in hot plasticity (1.5–2.0 times) of austenitic steel with nitrogen. To ensure high technological plasticity, and hence to minimize losses for removing surface defects and possible rejects, various variants of microalloying nitrogen-containing steel with boron or rare earth metals (REM) have been investigated. It is shown that the optimal boron addition is 0.0015–0.0025% (wt.), and in the case of microalloying with cerium or yttrium 0.02% (wt.) and 0.04% (wt.), respectively. The conditions for keeping the nitrogen-containing steel resistance to intergranular corrosion during tests according to the DU GOST 6032-2017 method after provoking heating from 500 to 850 °C and holdings up to 100 h are determined. At the same time, the intergranular corrosion resistance of 03Kh20N9G3A0.30 steel under certain test conditions can be noticeably (4 times) higher than that of 03Kh18N11 steel.

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