Standard Number, ASTM A – Title, Standard Terminology Relating to Steel, Stainless Steel, Related Alloys, and Ferroalloys. Standard Terminology Relating to Steel, Stainless Steel, Related Alloys, and Ferroalloys. Status: Withdrawn · Replaced by: ASTM A Buy this standard. Status: Alert Withdrawn. Norwegian title: Standard Terminology Relating to Steel, Stainless Steel, Related Alloys, and Ferroalloys. English title: Standard.
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Metals are rarely used in their pure form. Alloying elements are added to change their properties. There are over different stainless adtm with unique alloying element combinations.
These alloying additions improved corrosion resistance in different service environments and determine strength levels, formability, machinability and other desirable characteristics. Carbon is always present in stainless steel. The amount of carbon is the key.
In all categories except martensitic, the level is kept quite low. In martensitic grade the level is deliberately increased to obtain high strength and hardness.
SSINA: Stainless Steel: Overview
Heat treating by heating to a high temperature, quenching and then tempering develops the martensitic phase. Carbon can have an effect on the corrosion resistance. If, in localized areas, the chrome is reduced to below Once the composition contains at least The higher the chromium level the greater the protection.
Nickel is the essential allying element in the series stainless steel grades. It also makes the material non-magnetic. The addition of molybdenum to the Cr-Fe-Ni matrix adds resistance to localized pitting attack and better resistance to crevice corrosion particularly in Cr-Fe ferritic grades. Generally manganese is added to stainless steels to assist in de-oxidation, during melting, and to prevent the formation of iron sulfide inclusions which can cause hot cracking problems.
Small amounts of silicon and copper are usually added to the austenitic stainless steels containing molybdenum to improve corrosion resistance to sulfuric acid. The low carbon levels, however, tend to reduce the yield strength.
The addition of nitrogen helps to raise the yield strength levels back to the same level as standard grades.
Niobium additions prevents inter-granular corrosion, particularly in the heat effected zone after welding. Niobium helps prevent the formation of chrome carbides, that can rob the microstructure of the required amount of chromium for passivation.
Titanium is the main element used to stabilize stainless steel axtm the use of AOD Argon-Oxygen Decarburization vessels.
When stainless steel is aastm in air, it is difficult to reducing the carbon levels. At this high level, something was needed to stabilize the carbon and titanium was the most common way. Today all stainless steel are finished in an AOD vessel and the carbons levels are generally low due to the absence of oxygen. The most common grade today is with 0.
Sulfur is generally kept to low levels as it can form sulfide inclusions. The addition of sulfur, however, does reduce the resistance to pitting corrosion. MANGANESE Generally manganese is added to stainless steels to assist in de-oxidation, during melting, and to prevent the formation of iron sulfide inclusions which can cause asstm cracking problems.