Steel its tensile strength and make the austenite form of the iron-carbon solution more stable, chromium increases hardness and melting temperature, and vanadium also increases hardness while making it less prone to metal fatigue. To inhibit corrosion, at least 11% chromium is added to steel so that a hard oxide forms on the metal surface; this is known as stainless steel. Tungsten slows the formation of cementite, keeping carbon in the iron matrix and allowing martensite to preferentially form at slower quench rates, resulting in high speed steel. On the other hand, sulfur, nitrogen, and phosphorus are considered contaminants that make
SAE 304 stainless steel cracking above about 60 °C. It is considered resistant to pitting corrosion in water with up to about 400 mg/L chlorides at ambient temperatures, reducing to about 150 mg/L at 60 °C. 304 stainless steel is also very sensitive at room temperature to the thiosulfate anions released by the oxidation of pyrite (as encountered in acid mine drainage) and can undergo severe pitting corrosion problems when in close contact with pyrite- or sulfide-rich clay materials exposed to oxidation. For more severe corrosion conditions, when 304 stainless steel is too sensitive to pitting or crevice corrosion by chlorides or general corrosion