- Austenitic SS 304
Austenitic SS 304
What is 304 stainless steel?
Stainless steel gets its name from its ability to resist types of corrosion because of the interaction between its alloying components and the environment in which their exposure takes place. 304 grade stainless steel is one of the durable, widely used and dependable austenitic steel in a variety of forms and finishes.
304 stainless steel alloy
This austenitic steel is defined as Chromium-Nickel austenitic stainless steel alloy. Alloy 304 has 18% chromium, 8% nickel also known as 18/8 Stainless steel because of its composition. SS 304 due to the austenitic structure in the material is ductile.
SS 304 is less electrically and conductive than carbon steel and is essentially non-magnetic. 304 stainless steel comes with a higher corrosion resistance than regular steel and is popularly used as it can be formed into various shapes.
GENERAL SPECIFICATIONS
| GRADE | UNS | OLD BRITISH | EURONORM | SWEDISH SS | JAPANESE JJ | ||
|---|---|---|---|---|---|---|---|
| BS | EN | NO | NAME | ||||
| SS 304 | S30400 | 304S31 | 58E | 1.4301 | X5CrNi 18-10 | 2332 | SUS 304 |
| SS 304L | S30403 | 304S11 | – | 1.4306 | X2CrNi 19-10 | 2352 | SUS 304L |
| SS 304H | S30409 | 304S51 | – | 1.4948 | X6CrNi 18-10 | – | – |
One of the other properties of 304 grade stainless steel is that it is excellent corrosion resistance to a wide range of atmospheric conditions and another corrosive effect. 304 stainless steel may suffer from pitting and corrosion when introduced in warm chloride environments and may stress corrosion crack above about 60°C. Even when we consider the difference between SS 304 and SS 316, 304 grade stainless steel wins the race.
SS 304 characteristics are very impressive such as forming and welding properties, corrosion, and oxidation resistance because of the chromium content excellent toughness, even deep down to cryogenic temperatures.
304 stainless steel composition
The carbon content in this grade SS 304 strengthens it and does not allow the alloy from getting fragile. This 304 stainless steel composition has brilliant processing capabilities and cold-working techniques at low-temperature properties respond positively to and get hardened.
| Grade | NI | CR | Si | C | MN | P | S | N | Fe | |
|---|---|---|---|---|---|---|---|---|---|---|
| SS 304 | MIN % | 8 | 18 | – | – | – | – | BALANCE | ||
| MAX % | 13 | 20 | 0.75 | 0.08 | 2 | 0.045 | 0.03 | 0.1 | ||
| SS 304H | MIN % | 8 | 18 | – | – | – | – | BALANCE | ||
| MAX % | 12 | 20 | 0.75 | 0.03 | 2 | 0.045 | 0.03 | 0.1 | ||
| SS 304L | MIN % | 8 | 18 | – | 0.04 | – | BALANCE | |||
| MAX % | 10.5 | 20 | 0.75 | 0.1 | 2 | 0.045 | 0.03 |
304 stainless steel properties
Due to a wide range of 304 stainless steel properties, it is used in many manufacturing processes and various applications. 304 grade stainless steel is specially used in a variety of household and industrial applications such as process equipment and food handling, screws machinery parts, and in the automobile industry as car headers. AISI 304 stainless steel is widely used in the building and construction field for external accents such as water and fire features.
PHYSICAL PROPERTIES
| Grade | Density (g/cm3) | Elastic Modulus (GPa) | Mean Co-eff of Thermal Expansion (μm/m/°C) | Thermal Conductivity (W/m.K) | Specific Heat 0-100°C | Electrical Resistivity (nΩ.m) | |||
|---|---|---|---|---|---|---|---|---|---|
| SS 304/H/L | 8 | 193 | 0-100°C | 0-315°C | 0-538°C | at 100°C | at 500°C | ( J/Kg.K) | 720 |
| 17.2 | 17.8 | 18.4 | 16.2 | 21.5 | 500 | ||||
304-grade stainless steel is available in two different forms such as 304H and 304L and they all possess the same nominal chromium and nickel contents and thus possess the same corrosion resistance, ease of fabrication and weldability.
The carbon content in 304H (UNS S30409) is in a controlled proportion of 0.04-0.10%, which offers better high-temperature strength. Another version of SS 304, the 304L (UNS 30403) has a restricted carbon content of a maximum of 0.03%, which helps avoid sensitization during welding. Sensitization is when the chromium carbides are formed along grain boundaries when any kind of stainless steel is exposed to temperatures in the range of ~900 °F (480 °C)–1,500 °F (820 °C).
304L is known as the commoner among Stainless steel all over the world because of its easy processing and immediate availability. The alloy is very ductile, can be stretched into thin wire, and can be hammered without breaking. This is because of its carbon content of 0.035%.
In the case of Type 304H, it has a higher carbon content of about 0.04 – 0.10% which helps in making it a grade with diverse applications at any given elevated temperatures. Both the 304L and 304H aren’t dependent on any additional filler material due to their machinability and weldability. They possess a combination of low yield strength and high elongation and can easily change into different shapes however complicated they may be.
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