347 Stainless Steel

What is stainless steel 347?

Stainless Steel 347 is similar to the 321 stainless steels in that it is often used as a stabilized alternative to Type 304. In the case of 347, however, the stabilizing agent is columbium. This metal intensifies 347’s already present ability to withstand intergranular corrosion for maximum capabilities. Additionally, the columbium allows for 347 to undergo repeated heating in temperatures up to 1650° F. As a result, the metal is commonly applied to high temperature equipment, such as gaskets and expansion joints, along with rocket engine and chemical manufacturing.
In addition to its heat resistance properties, 347 also enjoys better resistance against creep and stress rupture corrosions. This is another advantage of type 304, as 347’s characteristics may be better suited for environments where stabilization is a primary concern.
Type 347 is known for being workable under all common welding techniques, along with hot and cold working. However, when being heat treated the metal must be heated up in the range of 2100 to 2250°F. This is due to 347’s inability to work harden under heat treatment. Cold reduction is the only method that will utilize the alloy’s elevated properties.

347 stainless steel 1.4550 Finished Products Form

• Round, Sqaure, Hexagon & Flat Bars
• Seamless / Welded Pipes
• Seamless / Welded Tubes
• Hot & Cold Rolled Plates & Sheets
• Forged Bars
• Buttweld Pipe Fittings
• Forged Fittings
• Ferrule Compression Fittings
• Forged Flanges
• Valves
• Guages

Applications for 347 stainless steel

Collector rings, airplane exhaust stacks, annealing box covers, jet engine parts.expansion joints, tubing, fasteners, flexible metal hose and bellows

Equivalents of grade 347

EU EN	USA –	France AFNOR	England BS	Sweden SS	Russia GOST
X6CrNiNb18-10	347	Z6CNNb18-10	347S31	2338	08KH18N12B

Composition ranges for 347 grade of stainless steel

Grade		Ni	Mn	P	C	S	Si	Cr	OTHER	N
347	min.	9.00	–	–	–	–	–	17.0	Nb=10(C+N)	–
	max.	13.00	2.00	0.045	0.08	0.030	1.00	20.0	1.0

Mechanical Properties 

Grade	Tensile Strength (MPa) min	Elongation (% in 50mm) min	Yield Strength 0.2% Proof (MPa) min	Hardness
				Rockwell B (HR B) max	Brinell (HB) max
347	515	40	205	92	201

Physical Properties

Grade	Density (kg/m3)	Elastic Modulus (GPa)	Mean Coefficient of Thermal Expansion (m/m/0C)			Thermal Conductivity (W/m.K)		Specific Heat 0-1000C (J/kg.K)	Electrical Resistivity (n.m)
			0-1000C	0-3150C	0-5380C	at 1000C	at 5000C
347	8000	193	17.2	17.8	18.4	16.2	21.5	500	720

Corrosion Resistance

• Pitting corrosion-resistant steel
• Steel resistant to rural and non-industrial urban atmosphere
• Stainless steel less aggressive sea atmosphere
• Steel resistant to salt of nitric acid and nitric acid at concentrations of up to 55% and temperatures up to 80 °C
• Steel resistant to non-oxidizing environments, e.g. H2SO4, HCl, HF, etc.
• Steel resistant to stress corrosion in solutions of chlorides and hydroxides
• Steel resistant to pitting and contact corrosion in environments containing halides

Heat Treatment

Annealing temperature range is 1800 to 2000°F

May be stress relief annealed within the carbide precipitation range of 800 to 1500°F without any danger of subsequent intergranualr corrosion

Cannot be hardened by heat treatment

WELDABILITY

Austenitic stainless steels are considered to be the most weldable out of all high alloy steels

Can be welded by all fusion and resistance welding processes