What Type of Material Is Stainless Steel 347?

Overview

Type 347 stainless is an austenitic steel alloy with added Niobium/Columbium which acts as a stabiliser. The alloy is, therefore, suitable for service in aqueous and low-temperature environments as the alloy has good resistance to intergranular attack. Alloy 347 is generally used where corrosive conditions are severe, such as aircraft exhaust stacks, manifolds and ring collectors. Type 347 is also used for heavy welded assemblies which cannot be annealed after welding or where the operating conditions cause exposure within the temperature range between 426.67° to 815.55°F.This grade is typically used in the 800-1500˚F temperature range where it is stabilized against chromium carbide precipitation by the addition of niobium, which results in the precipitation of niobium carbides. Type 347 has excellent intergranular corrosion resistance after exposure to this temperature range, and this grade resists oxidation up to 1500˚F and has higher creep and stress rupture properties than 304/304L. It also possesses good low temperature toughness and is non-magnetic in the annealed condition.

Stainless Steel 347 has slightly improved corrosion resistance over type 321 stainless steel in strongly oxidizing environments. Alloy 347 is a columbium(niobium)/tantalum stabilized austenitic chromium-nickel stainless steel which was developed to provide an 18-8 type alloy with improved intergranular-corrosion resistance. Alloy 347 has a slightly improved corrosion resistance over other alloys of stainless steel in strongly oxidizing environments as a result of the addition of columbium (niobium) and tantalum. Columbium-tantalum carbides precipitate within the grains instead of forming at the grain boundaries. Type 347 should be considered for applications requiring intermittent heating between 800ºF (427ºC) and 1650ºF (899ºC), or for welding under conditions which prevent a post-weld anneal.

stainless steel 347 is an austenitic stainless steel containing niobium. In terms of chemical composition, stainless steel 347 can be seen as 304 stainless steel with the addition of niobium. Niobium is a kind of rare earth element, which performance is similar to titanium. When added to the alloy, niobium can refine grains, resist intergranular corrosion and increase strength without reducing plasticity. It can thus save cost by reducing the thickness of the material and be used for structural strength parts. Type 347 exhibits good corrosion resistance in acid, alkali and salt liquid. It has good oxidation resistance and weldability in air below 800°C. In comparison with 304 stainless steel, 347 stainless steel features excellent high temperature stress rupture and high temperature creep resistance performance.

Chemistry of stainless steel 347 material

347 stainless steel is a stabilized austenitic stainless steel based on 18/8 stainless steel (18% Cr, 8% Ni). Its main chemical composition is as follows:

The characteristic of 347 stainless steel is the addition of stabilizer niobium, which gives it good intergranular corrosion resistance. The appropriate content of titanium and niobium effectively reduces the possibility of intergranular corrosion.

347 Stainless Steel Advantages Analysis

347 stainless steel has the following significant advantages among many stainless steels:

Good Intergranular Corrosion Resistance: Due to the addition of stabilizer niobium, 347 stainless steel has excellent intergranular corrosion resistance during welding, preventing intergranular corrosion in the heat-affected zone and improving the corrosion resistance of the weld joint.

High-Temperature Performance: 347 stainless steel maintains stable mechanical properties and oxidation resistance at high temperatures, suitable for long-term use below 800℃, applicable for critical components in high-temperature equipment.

Stress Corrosion Resistance: 347 stainless steel has good stress corrosion resistance in environments containing chlorides, suitable for corrosive environments like seawater, salt solutions, etc.

Weldability：Stainless steel 347 are easy to weld thanks to their high ductility and low thermal conductivity. This makes them viable for fabricating complex structures, piping, and tanks, leading to improved project efficiency and reduced downtime. Furthermore, these pipes have excellent dimensional stability, enabling precise fabrication and fitting for different applications.

Good Processability: 347 stainless steel has good cold working properties, can be processed and formed by cold rolling, cold drawing, etc., suitable for manufacturing various stainless steel products.

Durability：Durability is one of the properties that make stainless steel 347  popular in several industries. These strong pipes resist deformation better than other materials, making them efficient in harsh environments. This strength and durability are particularly useful in the offshore and marine industries, where the pipes can withstand harsh saltwater environments.

Superior Overall Performance: 347 stainless steel exhibits superior performance in corrosion resistance, high-temperature resistance, stress corrosion resistance, and processability, suitable for various complex environments and high-demand applications.

 Application fields of stainless steel 347 material

347 stainless steel, due to its superior properties, is widely used in the following areas:

1.Petrochemical Equipment: 347 stainless steel, with good high-temperature oxidation resistance and corrosion resistance, is suitable for high-temperature, high-pressure, and corrosive environments, such as cracking units, refining devices, etc.

2.Power Engineering: In high-pressure steam environments like nuclear power stations and thermal power plants, 347 stainless steel can be used as material for heat exchangers, boilers, and other critical components.

3.Food Processing Equipment: Due to its corrosion resistance and high-temperature resistance, 347 stainless steel is applied in food processing equipment, such as cookers, drying equipment, etc.

4.Aerospace: 347 stainless steel has stable performance under high temperature and pressure, suitable for critical components in the aerospace field, like engine parts, gas turbines, etc.

5.Chemical Equipment: 347 stainless steel can be used to manufacture various chemical equipment, such as reactors, storage tanks, etc., especially performing excellently in high-temperature, high-pressure, and corrosive environments.

6. Environmental Equipment: 347 stainless steel is used in various environmental equipment, like waste gas treatment devices, solid waste processing units, etc., having good corrosion resistance and high-temperature performance.

Conclusion

347 stainless steel, with its excellent corrosion resistance, high-temperature stability, and mechanical properties, is very suitable for use in chemical, petroleum, medical, food, and other fields. Especially in harsh working environments like high temperature, high pressure, and corrosion, the stability and durability of 347 stainless steel are widely recognized and applied.

As technology advances and the pursuit of material properties continues, 347 stainless steel will continue to play its unique advantages in various fields in the future, contributing to the industrial development and quality of life of humanity. At JN Alloy, we specialize in the production of 347 stainless steel, offering a material that excels in high-temperature and corrosive environments. Our commitment to quality ensures that our steel meets the diverse needs of industries ranging from petrochemical to aerospace.

In summary, stainless steel 347 are versatile, durable, and cost-effective, making them the ideal choice for several applications. Their properties, such as high-temperature resistance, corrosion resistance, and weldability, make them perfect for use in harsh environments. Additionally, they resist intergranular and crevice corrosion, reducing the risk of failure.