35 Electrode

Background

Duplex stainless steels' microctructures are part austenite and part ferrite. In wrought or cast duplex stainless steels, the microstructure is usually the result of heat treatment in the range of 1900 to 2100 degrees F.

As cast, they contain approximately 80%-plus ferrite, a small amount of austenite, and intermetallic compounds of the "sigma" and/or "chi" phases. Under rapid cooler (e.g water quench) from its heat treatment temperature, new intermetallic compound formation is prevented and a room temperature microstructure of between 40-60% ferrite and the balance being austenite is obtained.

Duplex stainless steels, during slow cooling or holding in the temperature range of 1000 to 1700 degrees F undergo metallurgic damage know as "885 degree F embrittlement". This is caused by precipitation of chromium-rich ferrite (alpha prime) within the iron-rich ferrite. Even properly heat-treated duplex stainless lose toughness below -50 degrees C due to the ferrite phase undergoing a ductile-to-brittle fracture transition with declining temperature.

Therefore, duplex stainless steels generally have a useful service temperature of -50 degrees F to 500 degrees F. They are also often alloyed with nitrogen and molybdenum to improve pitting and crevice corrosion resistance.

Advantages of Duplex Stainless Steel

Duplex stainless steels combine some of the better features of austenitic and ferritic stainless steels, such as higher strength (usually more than twice the yield strength) and dramatically better resistance to stress corrosion cracking in chloride solutions.

Due to these advantages, Duplex stainless steel is extensively used in heat exchanger tubings, oil equipment tubing and piping, on off-shore platforms, gas wells, line pipe, cast pump and valve bodies and fittings used for handling seawater and sour gas or oil.

They are also used in the chemical processing industry since Duplex stainless steel offers chloride pitting and crevice resistance as good as grade 317L stainless, coupled with better stress corrosion cracking than 304L or 316L stainless.

35 has been engineered to effectively weld and repair Duplex Stainless Steel rapidly and with weld integrity superior to virtually any other alloy for such specialized base metals.

Mechanical Properties

Tensile Strength: 110,000 psi
Yield Strength: 80,000 psi
Elongation: 25%
Impact: 45 ft/lbs

Application Procedure

35 can be applied using either AC current or DC reverse polarity. Surfaces should be cleaned and properly degreased.

Weldability with 35 is good and it is suggested adopting procedures that ensure an acceptable phase balance in both the weld metal and the Heat Affected Zone. In general, higher heat input is recommended.

Pre-Heating, although not generally considered necessary, can assist in achieving the desired HAZ microstructure.

Recommended Amperage

3/32" 75 to 85 amps

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