About Stainless Steel 347/347H
What is 347/347H Stainless Steel?
- Type 347 is a niobium stabilized chromium nickel austenitic stainless steel with corrosion resistance similar to 304/304L. 347 stainless steel is a columbium/tantalum stabilized austenitic chromium-nickel stainless steel. This grade is typically used in the 800-1500˚F temperature range where it is stabilized against chromium carbide precipitation by the addition of niobium, which results in the precipitation of niobium carbides. Type 347 has excellent intergranular corrosion resistance after exposure to this temperature range, and this grade resists oxidation up to 1500˚F and has higher creep and stress rupture properties than 304/304L.
- SS 347 also possesses good low temperature toughness and is non-magnetic in the annealed condition. 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. 347 is non-magnetic.
- Stainless Steel 347H is another stainless steel in a class of metals labeled of precipitation-hardened steels. It possesses many of the same properties and characteristics of stainless steel 347. In addition to its higher carbon content, the alloy is stabilized with an addition of columbium, or sometimes tantalum. Both these properties allow 347H to be exposed to higher temperatures than both 347 and the 304 stainless steel grades can withstand.
- Because of its elevated resistance to corrosion, 347H is often applied in high stress, high corrosion environments where exposure tends to be severe. High temperature manufacturing, steam pipes, boiler tubes, chemical processes and steam servicing all benefit from 347H’s resilience. This resilience in turn is due to the potentially elevated levels of chromium in 347H’s composition.
- The metal displays high workability under most common welding techniques. It can be treated with heat, however, it will not respond. Only cold working is sufficient to increase 347H’s toughness and strength.
What is the Difference Between 347/347H Stainless Steel and Other Grades?
Alloy 347 stainless steel tubing offers higher creep and stress rupture properties than Alloy 304 and, particularly, Alloy 304L, which might also be considered for exposures where sensitization and intergranular corrosion are concerns. 347 stainless steel offers good mechanical properties with higher creep and stress rupture characteristics than other grades, such as 304.
Difference between 347 and other grades:
|Type 304||The most common of austenitic grades, containing approximately 18% chromium and 8% nickel. It is used for chemical processing equipment, for food, dairy, and beverage industries, for heat exchangers, and for the milder chemicals.|
|Type 316||Contains 16% to 18% chromium and 11% to 14% nickel. It also has molybdenum added to the nickel and chrome of the 304. The molybdenum is used to control pit type attack. Type 316 is used in chemical processing, the pulp and paper industry, for food and beverage processing and dispensing and in the more corrosive environments. The molybdenum must be a minimum of 2%.|
|Type 317||Contains a higher percentage of molybdenum than 316 for highly corrosive environments. It must have a minimum of 3% “moly”. It is often used in stacks which contain scrubbers.|
|Type 317L||Restricts maximum carbon content to 0.030% max. and silicon to 0.75% max. for extra corrosion resistance.|
|Type 317LM||Requires molybdenum content of 4.00% min.|
|Type 317LMN||Requires molybdenum content of 4.00% min. and nitrogen of .15% min.|
|These types have been developed for corrosive resistance for repeated intermittent exposure to temperature above 800 degrees F. Type 321 is made by the addition of titanium and Type 347 is made by the addition of tantalum/columbium. These grades are primarily used in the aircraft industry.|
Applications of Stainless Steel 347/347H
- Chemical Processing
- Food Processing equipment and storage
- Petroleum Refining fluid catalytic cracking units, Polythionic acid service
- Pharmaceutical Production
- Waste Heat Recovery recuperators
- Boiler casings
- Cabin heaters
- Furnace heating elements
- Heavy wall welded equipment
- Welded construction and parts subjected to heating in the carbide precipitation range
- Aircraft collector rings
- Aircraft exhaust stacks
- Stainless Steel Reheater Tubes
- Superheater Tubes for Boiler
- Carburetor air intensifier tubes
- Exhaust manifolds
- Fire walls
- Carburetor air intensifier tubes
- Flash boilers
- Flexible couplings
- Jet engine parts
- Large mufflers for stationary diesel engines
- Pressure vessel
- Stack liners
- All-welded tank car for carrying chemicals
- Annealing box inner covers
- Expansion joints
- Heat resistors
- Welded tanks for storing organic chemicals
- Wire cloth and screens (industrial).
- High temperature chemical processes
- Heat exchanger tubes
- High temperature steam service
- High pressure steam pipes
- Radiant superheaters
- Heavy duty exhaust systems
- General refinery piping.
Properties, Limitations and Processing Characteristics of Stainless Steel 347/347H
- Higher creep stress and rupture properties when compared with 304
- Ideal for high temperature service
- Overcomes sensitization and intergranular corrosion concerns
- Can be used in elevated temperature applications
- Due to stabilisation the material offers better overall corrosion resistance when compared to 304/304L
The elevated temperature creep and stress rupture strengths of the stabilized steels are higher than those of unstabilized Alloys 304 and 304L. These superior properties for the 321 and 347 alloys permit design of pressure containing components for elevated temperature service to higher stress levels as recognized in the ASME Boiler and Pressure Vessel Code.
Alloy 347 stainless steel materials doesn’t perform well in chloride solutions, even in small concentrations, or in sulfuric acid.
Processing / Welding
- 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
- Oxyacetylene welding is not preferred for 347H steel.
- Superior general corrosion resistance over Type 321 due to stabilization with columbium.
- Reduced tendencies to form continuous networks of chromium carbides at the grain boundaries.
- Better high temperature properties than 304 or 304L. Generally used for parts which are intermittently heated up to 1500 deg. F. For continuous service the maximum temperature is 1650 deg. F.
- Type 347H has high carbon (.04 – . 10) for better high temperature creep properties.
- Improved intergranular corrosion resistance.
Equivalents of Stainless Steel 347/347H
Chemical, Mechanical & Physical Properties of Stainless Steel 347/347H
|NI||17.0 – 20.0||17.0 – 19.0|
|C||0.08 max||0.04 – 0.10|
|MN||2.0 max||2.0 max|
|P||0.045 max||0.045 max|
|S||0.030 max||0.030 max|
|SI||1.0 max||1.0 max|
|CR||17.0 – 19.0||17.0 – 19.0|
|NB||10xC – 1.10||8xC – 1.10|
|Units||Temperature in °C|
|Specific Heat||0.12 Kcal/kg.C|
|Melting Range||1398 – 1446 °C|
|Modulus of Elasticity||193 KN/mm²|
|Electrical Resistivity||72 µΩ.cm|
|Coefficient of Expansion||16.0 µm/m °C|
|Thermal Conductivity||16.3 W/m -°K|
|Annealed||1040 – 1100 (°C) / 1900 – 2000 (°F)|
|Tensile Strength, min.||Yield Strength, min.||Elongation||Hardness|
Fabrication Data and Other Properties of 347/347H Stainless Steels
Alloy 347/347H stainless steels can be easily welded and processed by standard shop fabrication practices.
- Stainless steel 304 are not tougher than stainless steel 347; this material will produce the same tough stringy chips. For work harden, slow speeds and heavy feeds will minimize this alloy’s tendency.
- Working temperatures of 2100-2250 F (1149-1232 C) are suggested for forging, upsetting and other hot work process. Don’t work this alloy at temperatures beneath 1700 F (927 C). Material must be water quenched or completely annealed after working to reattain maximum corrosion resistance.
- In spite of the fact that this material requires higher initial forces than 304 stainless steels, it is slightly tough and ductile and can be easily stamped, blanked, spun and drawn.
Heat Treatment and Resistance of Stainless Steel 347/347H
1850-2000 F (1010-1093 C), water quenches. This process will result in maximum ductility. 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 intergranular corrosion
This alloy doesn’t harden by heat treating. High properties may only be obtained through cold reduction.
Stabilizing Heat Treatment
Both solution heat treatment and stabilizing heat treatment are used to reduce susceptibility to intergranular stress corrosion and embrittlement also to increase high temperature creep strength. Types 321 and 347 stainless steels are the alloys most commonly thermally stabilized, but these alloys are also susceptible to weld and HAZ cracking problems during these heat treatment procedures, i.e., reheat cracking and grain boundary liquation cracking (mechanism covered in a previous article). This susceptibility increases with increasing component thickness. Therefore, another part of the QA/QC program should include some type of surface (PT) and volumetric (UT) inspection. Remember that these cracking mechanisms can be subsurface only.
Corrosion Resistance of Stainless Steel 347/347H
- Alloy 347 stainless steel displays good general corrosion resistance that is similar to 304.
- Used for applications where alloys such as Alloy 304 are vulnerable to intergranualr corrosion
- It was produced for use in the chromium carbide precipitation scope by 800 – 1500°F (427 – 816°C) where unbalanced alloys such as 304 are subject to intergranular attack. In this temperature scope, the overall corrosion resistance of Alloy 347 stainless steel plate is better than Alloy 321 stainless steel plate.
- Alloy 347 is preferred over Alloy 321 for aqueous and other low temperature environments in strongly oxidizing situations up to 1500°F (816°C).
- Primarily used in high temperature environments where resistance to sensitization is necessary, in turn preventing intergranualr corrosion at lower levels.
- The alloy can be utilized as a part of nitric solutions; most diluted organic acids at moderate temperatures and in pure phosphoric acid at lower temperatures and up to 10% diluted solutions at high temperatures.
- Susceptible to stress corrosion cracking
- Exhibits oxidation resistance similar to all other 18-8 austenitic stainless steels
- It can also be used in chloride or fluoride free caustic solutions at moderate temperatures.
Testing & Inspection of Stainless Steel 347/347H Materials
Testing (Destructive, Non Destructive)
|Positive Material Identification – PMI Testing||Hydrostatic Test|
|Chemical Analysis – Spectro Analysis||Hydrogen-Induced Cracking (HIC) Test|
|Mechanical Testing Such as Tensile, Elongation, Reduction of Area||Sulfide Stress Corrosion Cracking (SSC), NACE TM 0177|
|Micro Test||Radiography Test|
|Macro Test||Dye Penetrant Test (DP Test)|
|Hardness Test||Ultra Sonic Test (UT)|
|Pitting Resistance Test||Eddy Current Testing|
|Intergranular Corrosion (IGC) Test||Impact Test|
|Flaring Test||Bend Test|
- Our internal inspection reports would be provided for all the goods before shipment.
- Buyers or their associates are most welcome to visit us for personal inspect
- We regularly have inspections ongoing at our premises from internationally acclaimed Inspection Agencies such as TUV, BVIS, SGS, Llyods, DNV etc.
Prices for Stainless Steel 347/347H Materials
Prices for stainless steel 347/347H materials are directly co related to prices of the raw materials such as iron ore, metal scrap, chromium, nickel and various other alloying elements. The production cost of heat resistant stainless steel and nickel alloy plates is high as they contain high amount of nickel and chromium. Meanwhile, mild steel material is among the lowest cost steel available, followed by carbon steel, 400 series stainless steels, aluminium, alloy steel, and 300 series stainless steel. Special alloys such as titanium, Inconel, Monel and Hastelloy cost very high as the nickel, chromium and moly content is very high.
For special and discounted prices for various types of stainless steel 347/347H products, please feel free to contact us through email, phone or whatsapp.
We are also regularly publishing our price list for various steel products on our blog.
Documents Provided at the time of Domestic Sales or Export of Stainless Steel 347/347H Products
|Certificate of Origin||Raw Material Test Reports|
|Commercial Invoice||Heat Treatment Charts|
|Packing List||Quality Assurance Plan (QAP)|
|Fumigation Certificates||NABL approved Laboratory Test Reports|
|Letter of Gurantee||Material Test Certificates|
|ROHS Certificate||Certificate of Compliance/Conformity|
Price Basis for Stainless Steel 347/347H Materials
We can offer any of the following price basis depending on your requirement:
- FOR Site in India
- FOB Nhava Sheva
- CFR, CIF, CPT your destination port
- Door to Door Delivery Duty Paid as well as Duty Unpaid
Delivery Time of Stainless Steel 347/347H Materials
- If the items are available in stock, we take 2 days from the date of receipt of advance payment to clear the shipment and send it to port.
- And in-case the items are not availabe in stock, the time taken for manufacturing depends on the size, quantity and grade.
- However we can claim the fact that we can compete with anyone in India on Delivery time and most of the time our production time is the least.
- We have tied up with strong logistic partners in India which can undertake any type of shipping activities and make sure that there is no delay in shipment.
Marking & Packing of Stainless Steel 347/347H Materials
- All our products will have complete marking details which are co-related to the test certificates we supply.
- In case of orders for cut piece of Pipes, Sheets or Round Bars, the marking is transferred from the product from which it is cut. In such cases we provide Letter confirming the marking transfer and picture of the product from which it is cut.
- All goods are packed in wooden cases or pallets.