SS347

Similar to SS321, stainless steel 347 (SS347) is an austenitic stainless steel that includes tantalum (Ta) and niobium (Nb) intentionally added to the base stainless steel 304 (SS304). The addition of Nb+Ta helps reduce carbide precipitation sensitization during welding, enhancing its resistance to intergranular corrosion. SS347 is suitable for use in temperatures ranging from 427°C to 899°C. This stainless steel grade is commonly employed in applications such as high-temperature gaskets, expansion joints, exhaust manifolds, superheaters, heat exchangers, boilers, and chemical piping components.

1. UNS Designation & International Equivalent

Type	UNS	JIS	EN/DIN	EN/BS	EN/NF	ISO	GB	GOST
347	S34700	SUS347	X6CrNiNb18-10	347S31	X6CrNiNb18-10	16	0Cr18Ni11Nb	08KH18H12B

2. Product Forms and Standards

Product Forms	Material Standards
Plates, Sheets & Strips	ASTM A240
Billets, Bars & Rods	ASTM A276, A314, A479
Forgings(Flanges & Fittings)	ASTM A182, A473.
Wires	ASTM A313, A580.
Seamless and Welded Pipes	ASTM A312, A358, A213, A249, A813, A814, A632
Wrought Pipe Fittings	ASTM A403

*Especially, Metals-Piping supplies SS347 in the grades of ASTM A312 TP347, ASTM A182 F347, ASTM A403 WP347.

3. Physical Properties of SS347

ASTM A182 F347 ring gaskets, R24 made to ASME B16.20.

The Physical Properties of SS347
Density(lb/cu. in.)	0.29
Specific Gravity	8.03
Specific Heat(Btu/lb/Deg F)	0.12
Electrical Resistivity(microhm-cm)	438
Melting Point(Deg F)	2600

4. Chemical Composition of SS347

The Chemical Composition of SS347, %
Carbon	≤0.08
Manganese	≤2.00
Phosphorus	≤0.045
Sulfur	≤0.030
Silicon	≤0.75
Chromium	17.0-19.0
Nickel	9.0-13.0

5. Mechanical Properties of SS347

Tensile Strength, min.		Yield Strength, min.		Elongation	Hardness
ksi	Mpa	ksi	Mpa	%	HBW	Rockwell
75	515	30	205	40	201	92HRBW