Description
It is defined as Chromium- Nickel austenitic alloy. TP 304 has 18% chromium, 8% nickel and a maximum of 0.08% carbon, also known as 18/8 stainless steel because of its composition. The carbon content in this grade prevents the alloy from getting brittle. The grade has brilliant processing capabilities. It can be deep drawn without the need of intermediate annealing, it can be formed to variety of components for industrial, constructional and architectural requirements. The types in the given alloy grade are 304 L and 304 H.
Type 304 L is probably the world’s most common stainless steel, due to its easy processing and availability. The alloy has a carbon content of 0.035%, which makes it extremely ductile. Furthermore, it does not require to be heat treated after welding for removal of post welding stresses and hence can be used in heavy gauge components.
Type 304 H has higher carbon content of about 0.04- 0.10 %, which makes it a grade bearing diverse applications at elevated temperatures. Both the grades have good machinability and weldability and does not require additional filler metal. They have a combination of low yield strength and high elongation and hence they can be successfully made into complicated shapes.
Chemical Properties
| Grade | Ni | C | Cr | Mn | Si | P | Fe | S | N | |
| 304 | Min. | 8.00 | – | 18.00 | – | – | – | – | – | – |
| Max. | 10.50 | 0.08 | 20.00 | 2.00 | 0.75 | 0.045 | BAL. | 0.030 | 0.10 | |
| 304L | Min. | 8.00 | – | 18.00 | – | – | – | – | – | – |
| Max. | 10.50 | 0.08 | 20.00 | 2.00 | 0.75 | 0.045 | BAL. | 0.030 | 0.10 |
Physical Properties
| Density | 0.285 lbs / in3/7.90 g /cm3 |
| Melting Point | 2550 – 2590°F/1398 – 1421°C |
| Specific Heat @ 70°F | 0.12 BTU/lb-°F (32 – 212°F) 500 J/kg-°K (0 –100°C) |
| Thermal Conductivity @ 70°F | 9.4 BTU/hr/ft2/ft/°F 16.3 W/m-°K |
| Elastic Modulus @ 70ºF (tension) | 29.0 x 106 psi 200 GPa |
| Electrical Resistivity @ 70°F | 29.1 Microhm-in at 68°F 73 Microhm-cm at 20°C |
| Annealing | 1652 – 2102°F (750 – 1150°C) |
General Data
| Standard | SS 304 | SS 304L |
| UNS | S30400 | S30403 |
| WERKSTOFF NR. | 1.4301 | 1.4306/1.4307 |
| EN | X5CrNi18-10 | X2CrNi18-9 / X2CrNi19-11 |
| BS | 304S31 | 304S11 |
| GOST | 304S31 | 03Х18Н11 |
| JIS | SUS 304 | SUS 304L |
Standards Specifications
PIPES & TUBES
| Summary | Standards |
| Standard Specification for Seamless Ferritic and Austenitic Alloy-Steel Boiler, Superheater, and Heat-Exchanger Tubes | ASTM A213 |
| Standard Specification for Welded Austenitic Steel Boiler, Superheater, Heat-Exchanger, and Condenser Tubes | ASTM A249 |
| Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubing for General Service | ASTM A269 |
| Standard Specification for Seamless, Welded, and Heavily Cold Worked Austenitic Stainless Steel Pipes | ASTM A312 |
| Standard Specification for Electric-Fusion-Welded Austenitic Chromium-Nickel Stainless Steel Pipe for High-Temperature Service and General Applications | ASTM A409 |
| Standard Specification For Seamless Stainless Steel Mechanical Tubing | ASTM A511 |
FITTINGS & FLANGES
| Summary | Standards |
| Standard Specification for Forged or Rolled Alloy and Stainless Steel Pipe Flanges, Forged Fittings, and Valves and Parts for High-Temperature Service | ASTM A182 |
| Standard Specification for Wrought Austenitic Stainless Steel Piping Fittings | ASTM A403 |
Forms of Supply
Piping and tube, fittings and flanges, washers.
Corrosion Resistance
Resistant to a wide range of atmospheres in chemical, textile, food and petroleum industries. It is resistant to potable water with up to about 200 mg/L chlorides at normal temperatures, and reducing to about 150 mg/L at 60 °C.
Heat Treatment
Type 304 is non-hardenable by heat treatment. It is annealed to about 1100 deg. Celsius and then air cooled if thin sections or water quenched for heavy parts.
Weldability
Excellent weldability in all forms of the grade. They are generally known to be weldable by vommon fusion and resistance techniques. The 304 L grade doesn’t require any post-welding annealing but the heavy welded sections in the grade 304 might require.
Machining
Excellent machining, higher machining rates, lower tool wear rates.
Applications
- Food processing equipment
- Dairy equipment like milking machines, homogenizers, sterilizers
- Pressure vessels
- Heat exchangers used in turbines
- Brewing industry which includes pipelines, fermentation vats, storage and railway cars
- Domestic tool industry used in coffee urns, table tops, stoves, refrigerators
- Architectural panelling and railing
Possible grade alternatives
GRADES – 301 L
| Grade | Ni | C | Cr | Mn | Si | P | S | N | |
| 301L | Min. | 6.0 | – | 16.0 | – | – | – | – | – |
| Max. | 8.0 | 0.03 | 18.0 | 2.00 | 1.0 | 0.045 | 0.030 | 0.20 |
GRADE – 302 HQ
| Grade | Ni | C | Cr | Mn | Si | P | S | N | |
| 302 HQ | Min. | 8.0 | – | 17.0 | – | – | – | – | 3.0 |
| Max. | 10.0 | 0.03 | 19.0 | 2.00 | 1.0 | 0.045 | 0.030 | 4.0 |
GRADE – 303
| Grade | Ni | C | Cr | Mn | Si | P | S | |
| 303 | Min. | 8.0 | – | 17.0 | – | – | – | – |
| Max. | 10.0 | 0.15 | 19.0 | 2.00 | 1.0 | 0.20 | 0.15 |
GRADE – 316
| Grade | Ni | C | Cr | Mn | Si | P | Mo | S | N | |
| 316 | Min. | 10.0 | – | 16.0 | – | – | – | 2.00 | – | – |
| Max. | 14.0 | 0.08 | 18.0 | 2.00 | 0.075 | 0.045 | 3.00 | 0.03 | 0.10 |
GRADE – 321
| Grade | Ni | C | Cr | Mn | Si | P | Ti | S | N | Fe | |
| 321 | Min. | 9.0 | – | 17.0 | – | – | – | – | – | – | 65.045 |
| Max. | 12.0 | 0.08 | 19.0 | 2.00 | 1.0 | 0.045 | 5(C+N) -0.70 | 0.030 | 0.10 | – |
