Stainless steel 321 is the stabilized version of stainless steel 304. The 18/8 blend of chromium and nickel is tempered with titanium to give type 321 protection from intergranular corrosion that can occur after heat treatment. It is protected from temperatures ranging from 800 to 1500° F. The metal displays high strength and resistance to various forms of corrosions, including that from aqueous environments.
Type 321 finds application in heavy welding components, along with dynamic environments that are subject to changes.
However, the addition of titanium limits the application of 321 in terms of working. The metal is not recommended for certain welding techniques as it is not consumable. Beyond this, stainless steel 321 has excellent forming characteristics, does not require annealing after being welded, and displays toughness in a range of temperatures.
The metal shows strength even when exposed to cryogenic temperatures. Additionally, it is often chosen over Type 304 for its increased resistance to creep and rupture. Both metals may be susceptible to stress corrosion cracking.
| Bar Products | Imperial Sizes | Metric Sizes |
|---|---|---|
| Round Bar Bright Drawn H9 | 1⁄8" - 7⁄8" | 4mm - 25mm |
| Round Bar Smooth Turned H9/H10 | 1" - 3" | 30mm |
| Round Bar Peeled K12/K16 | 3 1⁄4" - 6" | - |
| Sheet Size | Finish | Thicknesses |
|---|---|---|
| 2500 x 1250 | 2B | 1.5mm - 3.0mm |
| Chemical Element | % Present |
|---|---|
Chromium (Cr) | 17.00 - 19.00 |
Nickel (Ni) | 9.00 - 12.00 |
Molybdenum (Mo) | 0.00 - 0.75 |
Copper (Cu) | 0.00 - 0.75 |
Titanium (Ti) | 0.00 - 0.70 |
Carbon (C) | 0.00 - 0.08 |
Manganese (Mn) | 0.00 - 2.00 |
Silicon (Si) | 0.25 - 1.00 |
Phosphorous (P) | 0.00 - 0.04 |
Sulphur (S) | 0.00 - 0.03 |
Nitrogen (N) | 0.00 - 0.10 |
| Mechanical Property | Value |
|---|---|
0.2% Proof Stress | 205 N/mm2 |
Elongation A50 mm | 40 % |
Hardness Brinell | 217 max HB |
| Mechanical Property | Value |
|---|---|
Proof Stress | 205 Min MPa |
Tensile Strength | 515 Min MPa |
Elongation A50 mm | 35 Min % |
| Physical Property | Value |
|---|---|
Density | 8.09 g/cm³ |
Melting Point | 1400-1427 °C |
Modulus of Elasticity | 193 GPa |
Electrical Resistivity | 0.074 x 10-6 Ω .m |
Thermal Conductivity | 16.1 W/m.K |
Excellent weldability by all standard fusion methods, both with and without filler metals. AS 1554.6 pre-qualifies welding of 321 and 347 with Grade 347 rods or electrodes; a high silicon version of 347 is also pre-qualified for welding of 321. A post weld heat treatment is not necessary.
321 stainless steel (1.4541) has excellent corrosion resistance at normal temperatures but is primarily designed to perform at elevated temperatures. The added titanium content of minimum five times the carbon % content (max 0.7%) means that grade 321 also possesses good creep strength, good resistance to chromium carbide precipitation and is very resistant to oxidation and intergranular corrosion up to 850ºC in dry air service conditions. Other corrosive compounds in the hot atmosphere such as water and sulphur compounds will significantly reduce the maximum service temperature. The overall characteristics of this material make it an excellent, relatively low cost choice for many applications. Subject to pitting and crevice corrosion in warm chloride environments, and to stress corrosion cracking above about 60°C. Considered resistant to potable water with up to about 200 mg/L chlorides at ambient temperatures, reducing to about 150 mg/L at 60°C.
The cold work hardening rate of 321 makes it less machinable than 410
stainless steel, but similar to 304.
Hot Forming
Working temperatures of 2100–2300°F (1149–1260°C) are recommended
for forging, upsetting and other hot working processes. Do not work this alloy
at temperatures below 1700°F (927°C). Material must be water quenched or
fully annealed after working to re-attain maximum corrosion resistance.
Cold Forming
The alloy is quite ductile and forms easily.
Good oxidation resistance in intermittent service to 900°C and in continuous service to 925°C. These grades perform well in the 425-900°C range, and particularly where subsequent aqueous corrosive conditions are present.
321H has higher hot strength and is particularly suitable for high-temperature structural applications.
These grades cannot be hardened by thermal treatment.
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