Alloy 304/304L (UNS S30400/S30403) is the most widely used "18-8" chromium-nickel austenitic stainless steel. It is a cost-effective and versatile corrosion-resistant alloy suitable for a wide range of general-purpose applications. It is common for 304L to be dual certified as both 304 and 304L. The low carbon content in 304L, combined with the addition of nitrogen, allows it to meet the mechanical properties of 304 stainless steel. Alloy 304/304L exhibits resistance to atmospheric corrosion, as well as moderately oxidizing and reducing environments. It also has excellent resistance to intergranular corrosion in the as-welded condition. Additionally, Alloy 304/304L maintains good strength and toughness at cryogenic temperatures. In the annealed condition, Alloy 304/304L is non-magnetic. However, it may become slightly magnetic as a result of cold working or welding. It can be easily welded and processed using standard shop fabrication practices.
Applications
- Chemical and Petrochemical
Processing—pressure vessels, tanks, heat exchangers, piping systems,flanges, fittings, valves and pumps
- Food and Beverage Processing
- Medical
- Mining
- Petroleum Refining
- Pharmaceutical Processing
- Power Generation—nuclear
- Pulp and Paper
Standards
ASTM........A 240
ASME........SA 240
AMS..........5511/5513
QQ-S........766
Alloy 304/304L stainless steel demonstrates good resistance to atmospheric corrosion, as well as resistance to various organic and inorganic chemicals in moderately oxidizing to moderately reducing environments. The high chromium content in the alloy provides resistance to oxidizing solutions, including nitric acid up to 55% weight at temperatures up to 176°F (80°C).
The alloy also resists moderately aggressive organic acids such as acetic acid. The presence of nickel in the alloy contributes to its resistance to moderately reducing solutions, such as pure phosphoric acid, at any concentration in cold solutions, and up to 10% diluted hot solutions. It can also operate successfully in caustic solutions without chlorides. However, Alloy 304/304L does not perform well in highly reducing environments containing chlorides and sulfuric acid.
Alloy 304/304L performs well in fresh water service with low chloride levels (less than 100ppm). However, at higher chloride levels, the grade becomes susceptible to crevice corrosion and pitting. In such severe conditions, an alloy with a higher molybdenum content, such as 316/316L, is recommended. Alloy 304/304L is not recommended for use in marine environments.
In most cases, the corrosion resistance of Alloys 304, 304L, and 304H will be roughly equal in various corrosive environments. However, in environments that are corrosive enough to cause intergranular corrosion of welds and heat-affected zones, Alloy 304L should be used due to its low carbon content, which helps mitigate such corrosion.
Lowest Temperature (°F) at Which the Corrosion Rate Exceeds 5mpy
CORROSION
ENVIRONMENT |
Type
304/304H |
Type
316L |
2205
(UNS S32205) |
2507 |
| 0.2% Hydrochloric Acid |
>Boiling |
>Boiling |
>Boiling |
>Boiling |
| 1% Hydrochloric Acid |
86p |
86 |
185 |
>Boiling |
| 10% Sulfuric Acid |
— |
122 |
140 |
167 |
| 60% Sulfuric Acid |
— |
<54 |
<59 |
<57 |
| 96% Sulfuric Acid |
— |
113 |
77 |
86 |
| 85% Phosphoric Acid |
176 |
203 |
194 |
203 |
| 10% Nitric Acid |
>Boiling |
>Boiling |
>Boiling |
>Boiling |
| 65% Niitric Acid |
212 |
212 |
221 |
230 |
| 80% Acetic Acid |
212p |
>Boiling |
>Boiling |
>Boiling |
| 50% Formic Acid |
≤50 |
104 |
194 |
194 |
| 50% Sodium Hydroxide |
185 |
194 |
194 |
230 |
|
83% Phosphoric Acid +
2% Hydrofluoric Acid
|
113 |
149 |
122 |
140 |
60% Nitric Acid +
2% Hydrocloric Acid |
>140 |
>140 |
>140 |
>140 |
50% Acetic Acid +
50% Acetic Anhydride |
>Boiling |
248 |
212 |
230 |
1% Hydrochloric Acid +
0.3% Ferric Chloride |
68p |
77p |
113ps |
203ps |
10% Sulfuric Acid +
2000ppm Cl- + N2 |
— |
77 |
95 |
122 |
10% Sulfuric Acid +
2000ppm Cl- + SO2 |
— |
<<59p |
<59 |
104 |
| WPA1, High Cl- Content |
<<50 |
≤50 |
113 |
203 |
| WPA2, High F- Content |
<<50 |
≤50 |
140 |
167 |
ps = pitting can occur
ps = pitting/crevice corrosion can occur
| WPA |
P2O5 |
CL- |
F- |
H2SO4 |
Fe2O3 |
Al2O3 |
SiO2 |
CaO |
MgO |
| 1 |
54 |
0.20 |
0.50 |
4.0 |
0.30 |
0.20 |
0.10 |
0.20 |
0.70 |
| 2 |
54 |
0.02 |
2.0 |
4.0 |
0.30 |
0.20 |
0.10 |
0.20 |
0.70 |
Weight % (all values are maximum unless a range is otherwise indicated)
| Element |
304 |
304H |
| Chromium |
18.0 min.-20.0 max. |
18.0 min.-20.0 max. |
| Nickel |
8.0 min.-10.5 max. |
8.0 min.-10.5 max. |
| Carbon |
0.08 |
0.04 min-0.10 max. |
| Manganese |
2.00 |
2.00 |
| Phosphorus |
0.045 |
0.045 |
| Sulfer |
0.030 |
0.030 |
| Silicon |
0.75 |
0.75 |
| Nitrogen |
0.10 |
0.10 |
| Iron |
Balance |
Balance |
Physical Properties
Density
0.285 lbs/in3
7.90 g/cm3
Specific Heat
0.12 BTU/lb-°F (32 – 212°F)
502 J/kg-°K (0 – 100°C)
Modulus of Elasticity
29.0 x 106
200 GPa
Thermal Conductivity 212°F (100°C)
9.4 BTU/hr/ft2/ft/°F
16.3 W/m-°K
Melting Range
2550 – 2590°F
1398 – 1421°C
Electrical Resistivity
29.1 Microhm-in at 68°C
74 Microhm-cm at 20°C
Mean Coefficient of Thermal Expansion
| Temperature Range |
|
| °F |
°C |
in/in °F |
cm/cm °C |
| 68-212 |
20-100 |
9.2 x 10-6 |
16.6 x 10-6 |
| 68-932 |
20-500 |
10.0 x 10-6 |
18.0 x 10-6 |
| 68-1600 |
20-870 |
11.0 x 10-6 |
19.8 x 10-6 |
Mechanical Properties
| |
ASTM |
| |
Typical* |
Type 304 |
Type 304H |
| 0.2% Offset Yield Strength, ksi |
42 |
30 min. |
25 min. |
| Ultimate Tensile Strength, ksi |
87 |
75 min. |
70 min. |
| Elongation in 2 inches, % |
58 |
40 min. |
40 min. |
| Reduction in Area, % |
70 |
— |
— |
| Hardness, Rockwell B |
82 |
92 max. |
92 max. |
Fabrication Data
Alloy 304/304L can be easily welded and processed by standard shop fabrication practices.
Cold Forming
The alloy is quite ductile and forms easily. Cold working operations will increase the strength and hardness of the alloy and might leave it slightly magnetic.
Hot Forming
Working temperatures of 1652–2102°F (750–1150°C) are recommended for most hot working processes. For maximum corrosion resistance, the material should be annealed at 1900°F (1038°C) minimum and water quenched or rapidly cooled by other means after hot working.
Machining
Alloy 304/304L is subject to work hardening during deformation and is subject to chip breaking. The best machining results are achieved with slower speeds, heavier feeds, excellent lubrication, sharp tooling and powerful rigid equipment.
| Operation |
Tool |
Lubrication |
CONDITIONS |
| |
|
|
Depth-mm |
Depth-in |
Feed-mm/t |
Feed-in/t |
Speed-m/min |
Speed-ft/min |
| Turning |
High Speed Steel |
Cutting Oil |
6 |
.23 |
0.5 |
.019 |
13-18 |
42.6-59 |
| Turning |
High Speed Steel |
Cutting Oil |
3 |
.11 |
0.4 |
.016 |
20-25 |
65.6-82 |
| Turning |
High Speed Steel |
Cutting Oil |
1 |
.04 |
0.2 |
.008 |
26-31 |
85.3-101.7 |
| Turning |
Carbide |
Dry or Cutting Oil |
6 |
.23 |
0.5 |
.019 |
75-85 |
246-278.9 |
| Turning |
Carbide |
Dry or Cutting Oil |
3 |
.11 |
0.4 |
.016 |
90-100 |
295.3-328.1 |
| Turning |
Carbide |
Dry or Cutting Oil |
1 |
.04 |
0.2 |
.008 |
110-120 |
360.8-393.7 |
| |
|
|
Depth of cut-mm |
Depth of cut-in |
Feed-mm/t |
Feed-in/t |
Speed-m/min |
Speed-ft/min |
| Cutting |
High Speed Steel |
Cutting Oil |
1.5 |
.06 |
0.03-0.05 |
.0012-.0020 |
18-23 |
59-75.5 |
| Cutting |
High Speed Steel |
Cutting Oil |
3 |
.11 |
0.04-0.06 |
.0016-.0024 |
19-24 |
62.3-78.7 |
| Cutting |
High Speed Steel |
Cutting Oil |
6 |
.23 |
0.05-0.07 |
.0020-.0027 |
20-25 |
65.6-82 |
| |
|
|
Drill ø mm |
Drill ø in |
Feed-mm/t |
Feed-in/t |
Speed-m/min |
Speed-ft/min |
| Drilling |
High Speed Steel |
Cutting Oil |
1.5 |
.06 |
0.02-0.03 |
.0007-.0012 |
10-14 |
32.8-45.9 |
| Drilling |
High Speed Steel |
Cutting Oil |
3 |
.11 |
0.05-0.06 |
.0020-.0024 |
12-16 |
39.3-52.5 |
| Drilling |
High Speed Steel |
Cutting Oil |
6 |
.23 |
0.08-0.09 |
.0031-.0035 |
12-16 |
39.3-52.5 |
| Drilling |
High Speed Steel |
Cutting Oil |
12 |
.48 |
0.09-0.10 |
.0035-.0039 |
12-16 |
39.3-52.5 |
| |
|
|
|
|
Feed-mm/t |
Feed-in/t |
Speed-m/min |
Speed-ft/min |
| Milling Profiling |
High Speed Steel |
Cutting Oil |
|
|
0.05-0.10 |
.002-.004 |
12-22 |
39.4-72.2 |
Welding
Alloy 304/304L can be readily welded by most standard processes. A post weld heat treatment is not necessary.
