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AISI Type 439 Stainless Steel Sheet (also known as ASTM XM-8) is a ferritic stainless steel designed to resist corrosion in a variety of oxidizing environments from fresh water to boiling acids. Type 439 Stainless Steel Sheet is a titanium stabilized, 18 percent chromium alloy that may be used in many oxidizing environments where Type 304 SS Sheet is considered adequate in terms of general corrosion resistance but is subject to chloride stress corrosion cracking. It is often used in place of Type 439 Stainless Steel where higher thermal conductivity is required. Type 439 Stainless Steel Sheet does not require annealing after welding to restore ductility or to provide intergranular corrosion resistance. Type 439 Stainless Steel Sheet also has superior formability capabilities and is heavily used in the automotive industry; it can be work hardened slightly to increase tensile strength.
AISI Type 439 Stainless Steel is resistant to attack by potable water and many mildly or moderately corrosive chemical environments which are oxidizing in nature. In various chloride solutions, studies have shown pitting resistance of Type 439 Stainless Steel to be superior to that of Type 304 Stainless Steel. In addition, Type 439 Stainless Steel is not subject to stress corrosion cracking which may cause premature failure of austenitic steels in chloride bearing environments such as hot waters used in heat exchangers.
AISI Type 439 Stainless Steel is resistant to attack by potable water and many mildly or moderately corrosive chemical environments which are oxidizing in nature. In various chloride solutions, studies have shown pitting resistance of Type 439 Stainless Steel to be superior to that of Type 304 Stainless Steel. In addition, Type 439 Stainless Steel is not subject to stress corrosion cracking which may cause premature failure of austenitic steels in chloride bearing environments such as hot waters used in heat exchangers.
439 stainless steel was developed in the 1950s. It was developed for use in direct-fired water heater tanks. This application required good welding properties and stress corrosion cracking resistance. Currently in the United States, lower cost immersion equipment and glass-lined tanks have replaced 439, which continues to be used successfully in Europe for direct fired hot water tanks.
The major advantages of 439 alloy are: