STS347 Stainless Steel: Chemical Composition, Standards and Applications

What is STS347 stainless steel?
STS347 stainless steel is a stabilized austenitic stainless steel widely used in high-temperature, high-pressure, and corrosion-resistant environments. Its key feature is the addition of niobium (Nb), which stabilizes chromium carbides and prevents intergranular corrosion during welding or long-term exposure at 450–850°C.

 

What is the equivalent material of STS347 stainless steel?

STS347 stainless steel is equivalent to AISI 347, UNS S34700, JIS SUS 347, and DIN 1.4550, which are all stabilized austenitic stainless steels known for excellent high-temperature performance, preventing carbide precipitation with added Niobium (Nb) or Tantalum (Ta).

Standard	Equivalent Grade
JIS	STS347
ASTM	A240 / A276 / A312 / A358 / A182 – 347 / 347H
EN	1.4550 / X6CrNiNb18-10
UNS	S34700 / S34709 (H grade)
ISO	9328-7 Grade X6CrNiNb18-10

 

STS347 stianless steel Chemical Composition

Element (%)	STS347
Carbon (C)	≤ 0.08
Chromium (Cr)	17.0 – 19.0
Nickel (Ni)	9.0 – 13.0
Manganese (Mn)	≤ 2.0
Silicon (Si)	≤ 1.0
Phosphorus (P)	≤ 0.045
Sulfur (S)	≤ 0.03
Niobium (Nb + Ta)	Stabilized (8xC min.)

 

STS347 stianless steel Mechanical Properties 

Property	STS347
Tensile Strength	≥ 515 MPa
Yield Strength (0.2%)	≥ 205 MPa
Elongation	≥ 40%
Hardness	≤ 95 HRB
Density	7.93 g/cm³
Max Service Temperature	Up to 900°C

 

What is the difference between STS347 and 347H?

The main difference between STS347 and 347H is carbon content: 347H has a higher carbon percentage (0.04-0.10%) compared to standard 347 (max 0.08%), which gives 347H superior creep strength and performance at elevated temperatures, making it ideal for high-heat applications like boilers and furnaces, while both offer excellent intergranular corrosion resistance due to niobium stabilization.

 

Applications of STS347 Stainless Steel

Industry	Application
Petrochemical	Heaters, reformer tubes, catalytic cracking units
Power generation	Superheater tubes, boiler tubes
Food & pharma	High-temperature sterilization equipment
Oil & gas	Exhaust systems, pressure components
Aerospace	Combustion chambers, heat shielding

 

Is STS347 better than STS304 or STS321?

STS347 isn't universally "better"; it excels over 304 and 321 in high-heat, welded applications due to niobium stabilization, preventing carbide precipitation (sensitization) for better corrosion resistance in those conditions, while 304 is versatile/common, and 321 (Titanium stabilized) offers similar high-temp strength to 347 but 347 (Niobium/Columbium) provides superior resistance in strong oxidizers and better creep strength. Choose based on operating temp, welding needs, and environment: 304 for general use, 321/347 for heat.

 

STS347 stainless steel Price per kg (2025 Reference)

Product Type	Price (USD/kg)
STS347 Sheets/Plates	USD 2.90 – 3.80 / kg
STS347 Seamless pipes	USD 4.20 – 6.50 / kg
STS347 Welded tubes	USD 2.50 – 3.50 / kg
STS347 Round bar	USD 2.80 – 4.00 / kg

 

Gnee supplies a full range of STS347 stainless steel product forms, including sheets and plates (0.5–80 mm), seamless and welded pipes and tubes, round/square/hex bars, flanges, fittings, coils, strips, and customized machined components.

All materials are delivered with EN10204 3.1/3.2 MTC, along with SGS/BV inspection, PMI testing, and complete welding procedure support to ensure reliable quality.
Packaging options include PE film wrapping, steel strip reinforcement, waterproof protection, plywood cases for pipes and fittings, and export-grade seaworthy pallets, with laser marking and heat-number tracking for full traceability.

Delivery is fast and flexible-7–10 days for stock items and 15–30 days for customized sizes-ensuring timely supply for global customers.