Introduction of duplex SS UNS31803

Duplex UNS S31803

Duplex UNS S31803 Technical Information

Overview

Duplex is an austenitic ferritic Iron Chromium-Nickel alloy with Molybdenim addition. It has good resistance to pitting, a high tensile strength and higher resistance to stress corrosion cracking at moderate temperatures to that of conventional austenitic stainless steels.

Duplex is a material having an approximate equal amount of austenite and ferrite. These combine excellent corrosion resistance with high strength. Mechanical properties are approximately double those of singular austenitic steel and resistance to stress corrosion cracking is superior to type 316 stainless steel in chloride solutions. Duplex material has a ductile / brittle transition at approximately -50°C. High temperature use is usually restricted to a maximum temperature of 300°C for indefinite use due to embrittlement.

Benefits

There are several benefits of Duplex including:

High Strength

High resistance to pitting, crevice corrosion resistance

High resistance to stress corrosion cracking, fatigue and erosion

Excellent resistance to Chloride stress corrosion cracking

Low thermal expansion and higher heat conductivity than Austenitic steels

High energy absorption

Good workability and weldability

Applications

Pipe – ASTM A790

The method of manufacture can be either seamless or automatic welding, with no addition of filler metal. Pipe may be hot or cold finished but must always be furnished in the heat treated condition.

BUTT WELD – ASTM A815

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This class covers the class of WP, made up of 4 categories and meet the requirements of ANSI B16.9. Pressure ratings are the same compatability of matching pipe.

Categories :-

WP-S : Seamless Construction

WP-W : Welded Construction where construction welds are radiographed

WP-WX : Welded Construction where all welds are radiographed

WP-WU : Welded Construction where al welds are Ultrasonically Tested.

Flanges ASTM A182

ASTM specifications regulate approved raw materials from which flanges can be made. Forged or rolled alloy steel pipe flanges, forged fittings and valves for high temperature applications.

Valves ASTM A890 Grade 5A

Standard Specification for Castings, lron-Chromium-Nickel-Molybdenum Corrosion-

Resistant, Duplex (Austenitic/Ferritic) for General Application’

Technical Details

CHEMICAL COMPOSITION (All values are maximum unless stated otherwise)

MECHANICAL PROPERTIES

* (N.A.C.E. MR-01-75 latest revision may limit hardness in certain applications)

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PREn (PITTING RESISTANCE EQUIVALENT) – (%Cr) + (3.3 x %Mo) + (16 x %N)

HEAT TREATMENT: SOLUTION ANNEALED AT 1020 DEG C – 1100 DEG C WATER QUENCH

EQUIVALENT GRADES? ? ? ? ? ? ? ? ? ? ?+