304 and 304L stainless steels are among the most versatile and widely used of all the stainless steel grades. So, what is it that makes these the best all-around performance stainless steels, and what’s the difference between the two?
Regarding the TP304/304L stainless steel of this material, let’s first understand 304 or 304L stainless steel.
The correct name for stainless steel is: standard + standard number + version number + grade, such as: ASTM A240-09 304L material, indicating that the material is: in line with the American ASTM standard 2009 version, A240 standard number of 304L grade austenitic stainless steel Plate material. As for the grade of this type of stainless steel pipe, “TP” is usually added before the grade, which means steel pipe: such as ASTM A312-08 TP304, ASTM A312-08 TP316L, etc.
AISI 304 and 304L (SS304L) are austenitic stainless steels, and also known as 18/8 stainless steel. AISI 304L stainless steel is an ultra-low carbon version of SS 304 (Carbon content: ≤ 0.08 %). “L” is short for “Low carbon” and the maximum carbon content is 0.03%. The main purpose is to prevent carbide precipitation and improve weldability and corrosion resistance.
Type 304 and 304L Stainless Steel Composition:
| Element | Type 304 (%) | Type 304L (%) |
| Carbon | 0.08 max. | 0.03 max. |
| Manganese | 2.00 max. | 2.00 max. |
| Phosphorus | 0.045 max. | 0.045 max. |
| Sulfur | 0.03 max. | 0.03 max. |
| Silicon | 0.75 max. | 0.75 max. |
| Chromium | 18.00-20.00 | 18.00-20.00 |
| Nickel | 8.00-10.50 | 8.00-12.00 |
| Nitrogen | 0.10 max. | 0.10 max. |
| Iron | Balance | Balance |
Physical properties of TP 304 stainless steel
Tensile strength σb (MPa)≥515
Conditional yield strength σ0.2 (MPa)≥205
Elongation δ5 (%)≥40
Mechanical properties of TP304L stainless steel:
Yield strength (N/mm2) ≥170
Tensile strength ≥485
Elongation (%)≥40
Corrosion Resistance
Due to its ultra-low carbon content, SS304L has better corrosion resistance than SS 304.
The following table list 304 vs 304L stainless steel corrosion rates in boiling 50% NaOH solution.
|
Material |
Base metal |
Weld |
||
|
mm/yr |
mils/yr |
mm/yr |
mils/yr |
|
|
SS304 (UNS S30400) |
3.0 |
118 |
3.3 |
130 |
|
SS304L (UNS S30403) |
1.8 |
71 |
2.2 |
87 |