HIGH-STRENGTH, THICK-WALLED, SEAMLESS STAINLESS STEEL PIPES AND METHOD FOR MANUFACTURING THEREOF Russian patent published in 2019 - IPC C22C38/18 C21D8/10 C22C38/58 

FIELD: metallurgy.

SUBSTANCE: invention relates to metallurgy, in particular to the manufacture of high-strength, thick-walled, seamless stainless steel pipes. It can be used in the oil and gas industry in harsh meteorological conditions. Pipe is made of stainless steel containing Cr in an amount of from 15.5 % to 18.0 %. Microstructure of steel contains ferritic and martensitic phases, with the maximum value of the areas of ferritic grains in the microstructure of steel in the annular cross section and the cross section in the rolling direction of the steel pipe is 3000 mcm² or less. Content of ferritic grains having an area of 800 mcm² or less, is 50 % or more, based on the proportion of the area. In the microstructure of steel there are different grains, which are adjacent ferritic grains, difference of the orientations of the crystals of one and the other ferritic grain is 15° or more. Pipe is obtained by heating the steel, flashing the steel for the manufacture of hollow steel billets and subsequent rolling with stretching at a hot working temperature of 700 °C to 1200 °C, the microstructure of the steel at the temperature of hot treatment contains 35 % or more of austenite, based on the fraction of the area.

EFFECT: resulting pipe material has high strength, corrosion resistance and low temperature toughness.

6 cl, 1 ex, 3 tbl