Intergranular amp; pitting corrosion resistant ferritic stainless steel in acid media

摘要

The present invention refers to a manufacturing procedure of a ferritic stainless steel presenting an improved corrosion-strength, and specially inter-granular corrosion-strength and pitting-corrosion-strength. Steel manufactured in ingot-shape, comprising on its composition by weight: 18 percent chromium 27 percent, 1 percent molybdenum 3 percent, 1 percent nickel 3 percent, manganese 1 percent, silicon 1 percent, carbon 0,030 percent, nitrogen 0.030 percent, 0.075 titanium 0.20 percent, 0.20 percent niobium 0.50 percent; sulfur 0.01 percent, phosphor 0,1 percent; balance being iron and impurities resulting from fusion of material necessary for manufacturing; this is subjected, in a first stage, to cooling at a rate comprised between 400 degree C and 600 degree C/hour until a temperature of 900 degree C, afterwards, in a second stage, to fast cooling at a rate comprised between 1,200 degree C and 1,400 degree C/hour.