Features of S31803

Description of S31803

Duplex stainless steel S32205(S31803) is composed of 22% chromium, 2.5% molybdenum and 4.5% nickel-nitrogen alloy. It features high strength, good impact toughness and good overall and local resistance to stress corrosion. 2205 Stainless was originally created for the pulp and paper to counter act harsh chemicals and chlorides. It is now prevalent in many industries as a more cost-efficient alloy in lieu of higher nickel grades.The yield strength of S32205(S31803) duplex stainless steel is more than double as high as that of common Austenitic stainless steel, allowing designers to reduce weight when designing products. On this ground, this alloy is more competitive than 316 and 317L. S32205 is especially suitable for use in the temperature range of -50°F / +600°F, beyond which, this alloy may also be considered to use, but with some limitations, especially when applied to welded structures.

UNS S31803/2205 is a duplex grade with a ferritic-austenitic microstructure. The alloy consists of around 40-50% ferrite in the annealed condition. The duplex microstructure has the high strength of the ferritic grades whilst retaining the corrosion resistance of the austenitic grades. It is not uncommon to see the metal used as a practical solution to chloride-induced stress cracking, which is the achilles’ heel of stainless steel.This grade has good mechanical strength at room temperature, resistant to corrosive attack, including pitting and is resistant to stress corrosion cracking. The grade is a successful alternative to the normal 300 series austenitic stainless steels, where its higher strength and resistance to stress corrosion cracking is required in critical applications.

Features of S31803

Resistance to corrosion

UNS S31803 is resistant to intergranular corrosion. It has better corrosion resistance than that of other austenitic stainless grades such as 316, with higher resistance to stress corrosion cracking to that of either 304 or 316 stainless grades. Pitting corrosion and crevice corrosion is higher than that of 316. Due to its higher corrosion resistance UNS S31803 has better fatigue strength in corrosive environments than that of other austenitic.

2205 duplex stainless steel is a cost effective solution for many applications where the 300 series stainless steels are susceptible to chloride stress corrosion cracking. Stress corrosion cracking occurs when stainless steels are subjected to tensile stress, while in contact with solutions containing chlorides. Increasing temperatures also increase the susceptibility of stainless steels to stress corrosion cracking.

The combination of chromium, molybdenum and nitrogen convey the good resistance of 2205 to chloride pitting and crevice corrosion. This resistance is extremely important for services such as marine environments, brackish water, bleaching operations, closed loop water systems and some food processing applications. The high chromium, molybdenum and nitrogen contents of 2205 provide corrosion resistance superior to common stainless steels, such as, 316L and 317L in most environments.

Welding

UNS S31803 (1.4462, F51) has good weldability similar to that of other stainless steel types. Low thermal expansion reduces residual stresses after welding. Use duplex welding electrodes similar to that of the parent steel when welding UNS S31083. Electric arc welding processes are suitable though oxyacetylene welding is not recommended due to the possibility of carbon pick up in the weld area of the UNS S31803. Whilst post weld annealing is not a requirement for many applications it will give optimum corrosion resistance in severe service conditions. We recommend you contact your welding consumables supplier who should provide you full assistance and information of welding UNS S31803 duplex.

Most standard welding methods suit this grade, except welding without filler metals, which results in excess ferrite. AS 1554.6 pre-qualifies welding for 2205 with 2209 rods or electrodes so that the deposited metal has the right balanced duplex structure.

Adding nitrogen to the shielding gas ensures that adequate austenite is added to the structure. The heat input must be maintained at a low level, and the use of pre or post heat must be avoided. The co-efficient of thermal expansion for this grade is low; hence the distortion and stresses are lesser than that in austenite grades.

Machinability

Although machinable, the high strengths of duplex stainless steels makes machining difficult. As an example, machining of 2205 is around 20% slower than for 304.Machining can be enhanced by using the following rules:

Cutting edges must be kept sharp. Dull edges cause excess work hardening.

Cuts should be light but deep enough to prevent work hardening by riding on the surface of the material.

Chip breakers should be employed to assist in ensuring swarf remains clear of the work

Low thermal conductivity of austenitic alloys results in heat concentrating at the cutting edges. This means coolants and lubricants are necessary and must be used in large quantities.

Heat Resistance

The high chromium content of duplex stainless steels that protects against corrosion, causes embrittlement at temperatures over about 300°C. At low temperatures duplex stainless steels have better ductility than the ferritic and martensitic grades. Duplex grades can readily be used down to at least -50°C.The best suited heat treatment for this grade is solution treatment (annealing), between 1020 - 1100°C, followed by rapid cooling. Grade 2205 can be work hardened but cannot be hardened by thermal methods.

Chemical composition of S31803

S31803 Duplex Stainless Steel combines improved resistance to stress corrosion cracking, pitting, crevice corrosion and high strength. Due to it's chemical composition S31803 duplex stainless steel resists chloride environments and sulphide stress corrosion.

Applications of S31803 products

Duplex UNS S31803 products have features like high resistance to chloride stress corrosion cracking, resistance to chloride pitting and crevice corrosion, good general corrosion resistance, good sulfide stress corrosion resistance, high strength, good weldability and workability, etc.Duplex Steel UNS S31803 products is used in various industries like chemical processing, Oil and Gas Industry, Food Processing Industry and other industry.

Oil and Gas Industry:

Duplex Steel S31803  products are widely used in oil and gas due to their superior corrosion resistance properties. These fittings are ideal for pipelines that carry abrasive and corrosive materials, making them a perfect choice for offshore drilling platforms, refineries, and pipelines.

Chemical Industry:

The chemical industry also heavily relies on UNS S31803  products to safely transport chemicals that require high pressure and temperature. The products are resistant to various chemicals, including acids and alkalis, and can withstand harsh environments, making them an ideal choice for this industry.

Food Processing Industry:

The food processing industry requires products that are resistant to corrosion and can withstand high-pressure and high-temperature applications. Duplex S31803 pipes are ideal for this industry because they are non-toxic and hygienic. They do not leach harmful substances into the food products, making them an ideal choice for food processing applications.

UNS S31803 is versatile and can be used in various industries that require high-pressure and high-temperature applications. These fittings offer excellent mechanical properties, corrosion resistance, and affordability from the oil and gas industry to the food processing industry. They are ideal for use in harsh environments and can withstand various chemicals, making them a popular choice among industries worldwide. If you are looking for reliable and durable products, Duplex Steel S31803 can be an excellent choice for your application.