What is SS310 material?
SS 310 stainless steel is type of Austenitic Stainless steel with medium carbon percentage alike to carbon steel range and used mainly for high temperature service for example furnace parts, pipeline and heat treatment components. The material can withstand upto 2100°F 1150°C for continuous service. 310 type of austenitic stainless steel offers excellent oxidation resistance, good creep properties at high temperature and general corrosion resistance. The low carbon variant of 310 is 310S grade which have good weldability compare to SS310. SS310 is also used for cryogenic temperature services upto the temperature of -268°C (-450°F).
The UNS Number of the SS310 material is UNS S31000, for 310S UNS number is UNS S31008 and for 310H UNS Number is UNS S31009. The material is supplied as per below specifications:
- ASTM: A-240
- ASME : SA-240
- AMS: 5521
Chemical and mechanical properties of SS310
The chemical properties of SS310, SS310S and SS310H are shown in below picture. The main difference between 310, 310S and 310H is the amount of Carbon%. SS310S has the lowest carbon i.e. 0.08% maximum while SS310 has the maximum carbon percentage.
Standard tensile and yield strength of SS310 at 68°F or 20°C i.e. ambient temperature is given in below table. The typical hardness of SS310 is 217 HB and elongation is minimum 45%, a typical characteristics of austenitic stainless steel.
The creep properties of SS310 are given in below table at various temperature. The creep strain and creep rupture strength is shown in MPa for 310 stainless steel.
SMAW or Stick Welding of 310 alloy
Stick welding or SMAW welding of SS310 is carried out using E310-15 electrode. Stick welding of E310H is carried out with E310H-15 type electrode.
E310H SMAW Electrode properties: The composition of this weld metal is the same as that deposited by E310 electrodes, except that carbon ranges from 0.35 to 0.45 percent. These electrodes are used primarily for welding or repairing high-alloy heat and corrosion-resistant castings of the same general composition which are designated as Type HK by the Alloy Castings Institute. The alloy has high strength at temperatures over 1700°F [930°C]. It is not recommended for high-sulfur atmospheres or where severe thermal shock is present. Long time exposure to temperatures in the approximate range of 1400°F to 1600°F [760°C to 870°C] may induce formation of sigma and secondary carbides which may result in reduced corrosion resistance, reduced ductility, or both. The composition of this electrode should not be confused with the stainless steel wrought alloy 310H which has a lower carbon content of 0.04–0.10 percent.
When the 310 or 310H material is exposed to high temperature (in the temperature range of1202–1742°F (650–950°C)) it get sigma embrittlement. The one solution to regain its ductility back is by solution annealing but often its not feasible to do so at sites or big vessels made of SS310 material. In these case any welding work or repair shall be carried out with E16-8-2 electrode only. E16-8-2 electrodes offer high crack resistance compare to E310-XX type electrodes.
TIG-MIG welding of SS310
TIG or MIG welding of SS310/ SS310H/SS310S material is carried out using ER310 type filler wire as per SFA 5.9. ER16-8-2 is also used for materials exposed to high temperature. ER16-8-2 is also suitable for welding of new materials without any concerns. Flux core welding (FCAW) is carried out using SFA 5.22-E310T-X type cored wire.
Pure argon is usually used for shielding purposes. To know more about Shielding gases of TIG MIG and FCAW welding of stainless-steel duplex steel, Click here.
When welding open root with TIG or MIG gas purging is required and need to be pure inert gas to avoid the oxidation of the root side.
Welding of SS310 to Carbon Steel
SMAW or stick Welding of SS310 to carbon steel is carried out using E309L-15/16/17 or with AWS SFA/A 5.11, Classification ENiCrFe-2 or -3 or ENiCrMo-3 type electrodes.
welding 310 to 304 or 316 stainless
Welding of SS310 to SS304 or SS316 stainless steel is carried out using AWS SFA 5.4, Classifications E309-15/16/17 or E309L-X 15/16/17.
Click here to know Difference between E309L-15, 16 17, E316L-15,16 and 17
Preheating & interpass temperature
Preheating is generally not required for welding 310 material either its S310S or 310H. Interpass temperature shall be kept maximum 400°F or 200°C. Its is recommended to use low heat input to avoid deformation during SS310 welding.
For material exposed to high temperature and prone to have sigma embrittlement will lack ductility. So, preheat can be applied to these materials to avoid cracking during welding.
PWHT of SS310
PWHT of SS310 is not required. The heat treatment process used only is solution annealing at 1832–2101°F (1000–1150°C) to restore material ductility and original microstructure when it is exposed to high temperature.
Sigma embrittlement in SS310
SS310 alloy when exposed to temperature range of 1202–1742°F (650–950°C), the microstructure is prone to sigma phase precipitation (𝜎 phase) due to high carbon present in the material. Sigma phases are hard microstructure which reduce the material ductility. A high amount of sigma precipitation in material will make it brittle & reduce toughness and the material can easily crack if any impact is applied to the materials.
To overcome the effect of sigma embrittlement, a heat treatment known as solution annealing heat treatment is applied to the material at the temperature range of 2010-2100°F (1100–1150°C) to restore back material ductility and the toughness.