STAINLESS STEEL 321
Stainless steel is the branded metal of present times. It can be applied successfully in modern needs. Its value can be utilized across various engineering productions. Stainless steel is recyclable, sustainable, and versatile in nature.
Stainless steel is a ferrous carbon alloy that contains chromium at least 11%. The famous property of corrosion resistance is contributed by the added chromium. Chromium forms a protective layer of chromium oxide and prevents corrosion. It makes stainless steel bright finished. Other alloying agents include nickel and molybdenum.
Austenitic steel is the most commercially used stainless steel worldwide. It represents strength, formability, resistance, and hardness. Austenitic stainless steel is high chromium and nickel grades. It exhibits superior corrosion resistance and considerable mechanical properties. This stainless steel cannot be hardened by cold-working and non-magnetic in nature.
Grade 321 Stainless Steel
Stainless steel Grade 321 is stabilized austenitic stainless steel. It is stabilized with added titanium with the presence of chromium and nickel in the composition. Titanium prevents the formation of chromium carbide precipitation from welding or exposure to high temperatures. Grade 321 is not sensitive to the carbide precipitation, which is formed after or during welding. It offers excellent corrosion resistance to intergranular corrosion after welding.
Stainless steel Grade 321 exhibits excellent forming and welding characteristics and holds good toughness at cryogenic temperature. It cannot be hardened by heat-treatment and it is non-magnetic in nature.
It is used often in applications that require intermittent heating between the temperature range of 427-899ºC, and for welding where post-weld annealing is not required. Most widely used in the aerospace industry, chemical processing, etc.
CHEMICAL COMPOSITION
| Element | Percentage (%) |
| Carbon (C) | 0.08 max |
| Chromium (Cr) | 17.0 – 19.0 |
| Nickel (Ni) | 9.0 – 12.0 |
| Titanium (Ti) | ≥ 5 × C (min) |
| Manganese (Mn)+ | 2.0 max |
| Silicon (Si) | 1.0 max |
| Phosphorus (P) | 0.045 max |
| Sulfur (S) | 0.030 max |
| Iron (Fe) | Balance |
MECHANICAL COMPOSITION
| Property | Value |
| Tensile Strength | 515 MPa (min) |
| Yield Strength | 205 MPa (min) |
| Elongation | 40% (min) |
| Hardness (Brinell) | 217 HB max |
| Density | 8.0 g/cm³ |
| Melting Range | 1399 – 1420°C |
PHYSICAL PROPERTIES
| Property | Value |
| Thermal Conductivity | 16.2 W/m·K |
| Electrical Resistivity | 0.72 µΩ·m |
| Modulus of Elasticity | 193 GPa |
| Magnetic Properties | Non-magnetic (slightly magnetic after cold work) |
EQUIVALENT GRADE
| Standard | Grade |
| AISI / ASTM | 321 |
| EN | 1.4541 |
| JIS | SUS 321 |
| DIN | X6CrNiTi18-10 |
| IS | 321 |
POSSIBLE ALTERNATIVE GRADES OF GRADE 321
- Grade 347 can be used as an alternation for grade 321.
- Grade 304L can be used as it provides resistance to intergranular corrosion, but it is appropriate for high-temperature strengthening.
- Stainless steel Grade 304 H
- Stainless steel Grade 310
CORROSION RESISTANCE
SS 321 Grade offers excellent corrosion resistance comparable to grade 304. It offers improved corrosion resistance in the chromium carbide precipitation range of 427-816°C. It offers improved intergranular corrosion resistance due to the addition of titanium.
Stress corrosion cracking can occur above 60°C. It also provides resistance to organic and inorganic acids at moderate temperatures. SS Grade 321 is prone to pitting and crevice corrosion in a warm chloride atmosphere.
Stainless steel 321 Grade can be used with diluted organic acids, phosphoric acid at low to moderate temperature. It can provide resistance to polythionic acid stress corrosion.
HEAT RESISTANCE
SS Grade 321 stainless steel offers a scaling resistance of 900°C in intermittent conditions and 925°C in continuous operations.
OXIDATION RESISTANCE
Stainless steel Grade 321 displays good oxidation resistance up to 870°C.
HOT FORMING
Grade 321 SS can be formed hot, by working in the temperature range of 1149- 1260°C. This grade is not suggested to work below the temperature of 927°C.
Grade 321 must undergo annealing after exposure to a high temperature to obtain maximum corrosion resistance.
COLD FORMING
Grade 321 SS has good ductility and can be formed easily.
HEAT TREATMENT
Annealing can be performed by heating in the temperature range of 950-1120°C followed by cooling for obtaining maximum corrosion resistance.
Tempering is done by heating the material to 700°C for 1-2 hours, followed by air cooling.
Stainless Steel Grade 321 cannot be hardened by heat treatment.
WELDING
Grade 321 shows excellent weldability, as the addition of titanium prevents carbide precipitation during welding. Austenitic stainless steel can be welded by common fusion and welded techniques, with and without filler metals. Grade 347 electrodes are suggested for welding grade 321. The high silicon content of grade 347 can also be used.
APPLICATIONS
Grade 321 is mainly used in:
- Aircrafts exhaust
- Heat exchangers
- Spiral welded tube
- Furnace parts
- Welded equipment
- Chemical processing equipment
- Refinery equipment
- Thermal oxidizers
321 Round Bars 321 Fine Wire
321 Hex Bars 321 General Purpose Wire
321 Flat Bars 321 Cold Heading Wire
321 Square Bars
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