SUPERMARTENSITIC STAINLESS STEEL EXHIBITING HIGH MECHANICAL STRENGTH AND RESISTANT TO CORROSION, PROCESS OF ITS MANUFACTURE AS WELL AS OBJECTS PRODUCED THEREFROM

摘要

In the present invention there is disclosed a supermartensitic stainless steel exhibiting high mechanical strength and resistance to corrosion and having the following composition: less than or equal to 0.05 percent by weight of carbon, 12 to 15 percent by weight of chromium, 4 to 7 percent by weight of nickel, 1.5 to 2 percent by weight of molybdenum, 0.06 to 0.12 percent by weight of nitrogen, 0.5 to 1 percent by weight of manganese, less than 0.3 percent by weight of copper, less than 0.02 percent by weight of phosphorus, less than or equal to 0.005 percent by weight of sulfur, less than 0.02 percent by weight of aluminium, less than or equal to 1 percent by weight of silicon, whereby the balance being iron and small impurities and the percentages of Cr, Mo and N meet the requirement of the following formula: (Cr + 3.3 Mo + 16N) is more than or equal to 19. The above-described steel server for the manufacture of products exhibiting excellent properties regarding mechanical strength and resistance to corrosion, by forging or hot rolling the steel followed by a teat treatment. Austenitic heat treatment of a product is carried out at a temperature ranging from 880 degC do 980 degC, then the product is cooled down to a temperature less than 90 degC and subsequently it is subjected to tempering at a temperature ranging from 560 degC do 670 degC.