Stainless Steel 347, 1.4550, UNS s34700
What is 347 stainless steel?
SS 347 stainless steel is a columbium/tantalum stabilized austenitic chromium-nickel stainless steel. This material is stabilized against chromium carbide formation by the addition of columbium and tantalum. Since these elements have a stronger affinity for carbon than chromium, columbium-tantalum carbides precipitate within the grains instead of forming at the grain boundaries. SUS 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. SS347 is non-magnetic.
UNS S34700 Chemical Composition
|Niobium||10 x C min / 1.00 max|
* Maximum, unless range is indicated
347 stainless steel Mechanical Properties
Mechanical property requirements for annealed product as specified in ASTM A240 and ASME SA240.
|Yield Strength, min. (ksi)||30|
|Tensile Strength, min. (ksi)||75|
|Elongation, min. (%)||40|
|Hardness, max. (Rb)||92|
Alloy 347 stainless steel plate exhibits good general corrosion resistance that is comparable to SUS304. It was developed for use in the chromium carbide precipitation range of 800 – 1500°F (427 – 816°C) where un-stabilized alloys such as SUS304 are subject to intergranular attack. In this temperature range, the overall corrosion resistance of Alloy 347 stainless steel plate is superior to Alloy 321 stainless steel plate. Alloy 347 also performs somewhat better than Alloy 321 in strongly oxidizing environments up to 1500°F (816°C).
The alloy can be used in nitric solutions, most diluted organic acids at moderate temperatures and in pure phosphoric acid at lower temperatures and up to 10% diluted solutions at elevated temperatures. Alloy 347 stainless steel plate resists polythionic acid stress corrosion cracking in hydrocarbon service. It can also be utilized in chloride or fluoride free caustic solutions at moderate temperatures.
Alloy 347 stainless steel plate does not perform well in chloride solutions, even in small concentrations, or in sulfuric acid.