AISI 347 stainless steel VS. AISI 347H

Dec 08, 2025

Leave a message

AISI 347 and AISI 347H are both niobium-stabilized austenitic stainless steels, widely used in high-temperature applications. While they share similar corrosion resistance and weldability, the two grades differ primarily in carbon content, mechanical properties, and performance under prolonged high-temperature service. Understanding these differences is critical for buyers in the chemical, petrochemical, power generation, and heat-resistant equipment industries.

What is AISI 347 material?

AISI 347 stainless steel is equivalent to UNS S34700, ASTM 347, KS STS 347, JIS SUS 347, and DIN 1.4550. The modulus of elasticity of AISI 347 stainless steel is 28.0 x 10⁶ psi (193 GPa). The melting range of AISI 347 stainless steel is 1398–1446 °C (2550–2635 °F). It can be processed into plates, sheets, coils, strips, tubes, bars, and wires.

What is AISI 347H material?

AISI 347H is a high-carbon, niobium-stabilized austenitic stainless steel, similar to grade 347 stainless steel, designed for high-temperature applications. Due to its higher carbon content (0.04-0.10%) and stabilizing elements, it exhibits improved creep strength and resistance to sensitization (intergranular corrosion) at elevated temperatures (above 1000°F/537°C). It is suitable for demanding environments such as high-temperature chemical processing, refinery piping, and heavy-duty exhaust systems.

What is the main difference between AISI 347 and 347H?

The main difference is carbon content: AISI 347 has a max 0.08% carbon, while 347H has a higher range (0.04-0.10%), giving 347H superior high-temperature strength and creep resistance, making it better for prolonged elevated service, while 347 has slightly better weldability for general use.

AISI 347 stainless steel VS. AISI 347H Chemical Composition

Element	AISI 347	AISI 347H
Carbon (C)	≤ 0.08%	0.04–0.10%
Chromium (Cr)	17–19%	17–19%
Nickel (Ni)	9–13%	9–13%
Manganese (Mn)	≤ 2.0%	≤ 2.0%
Silicon (Si)	≤ 0.75%	≤ 0.75%
Phosphorus (P)	≤ 0.045%	≤ 0.045%
Sulfur (S)	≤ 0.03%	≤ 0.03%
Nitrogen (N)	≤ 0.10%	≤ 0.10%
Niobium (Nb + Ta)	0.8–1.0%	0.8–1.0%

AISI 347 stainless steel VS. AISI 347H Mechanical Properties

Property	AISI 347	AISI 347H
Tensile Strength (Rm)	520–700 MPa	520–720 MPa
Yield Strength (Rp0.2)	≥ 205 MPa	≥ 205 MPa
Elongation	≥ 40%	≥ 40%
Hardness	≤ 215 HB	≤ 220 HB
Density	7.90 g/cm³	7.90 g/cm³
Max Continuous Service Temp	870°C	870–950°C

What are the maximum service temperatures for 347 and 347H?

Both 347 and 347H stainless steels are excellent for high temperatures, with 347 typically used up to 1500°F (816°C) intermittently, while the higher-carbon 347H offers superior strength and is rated for continuous service up to 900°C (1650°F), generally allowing slightly higher design stresses and sustained use in severe conditions like aviation and power generation.

Is 347H more expensive than 347?
Yes , 347H stainless steel is typically more expensive than 347, due to its higher carbon content and enhanced high-temperature strength. For example, while 347 sheets might cost around USD 3.2–3.6 per kg, 347H often sells for USD 3.5–4.0 per kg, reflecting approximately a 10–15% premium for the improved thermal stability and creep resistance of 347H.

What is the difference between 304H and 347H?
347H is a stabilized grade of 304, adding Niobium (Nb) to prevent carbide precipitation (sensitization) during welding and high-temp exposure, making 347H superior for welded, sustained high-temperature uses like aerospace and boilers, whereas 304H is good for general heat.

Gnee supplies both AISI 347 and 347H stainless steel in a full range of forms, sizes, and finishes to meet high-temperature and corrosion-resistant application requirements.