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Alloy 304H/1.4948 UNS S30409 stainless steel is a variation of the 18% chromium – 8% nickel austenitic Alloy 304, in which the carbon content is controlled to a range of 0.04-0.08 to provide improved high temperature strength to parts exposed to temperatures above 800°F.
Unlike 304L, Type 304H has a higher carbon content making the steel more suitable for use in applications where elevated temperatures are present. It is an austenitic chromium-nickel steel alloy and the greater carbon content delivers an increased tensile strength and yield strength. The material is recommended for use in ASME pressure vessels in working service above 525 °C due to the grade's heat resistant properties.
The higher carbon content of 304H increases its strength, so the ASTM tensile strength and yield strength of 304H is greater than 304L. 304H has greater short term and long term creep strength than 304L at temperature up to 500 degrees C, and 304H is more resistant to sensitization than 304L. In ASME pressure vessels for use above 525 degrees C, the carbon content of 304 stainless steel must be 4 percent or more. 304H is required in such applications.
Alloy 304H is most commonly used in petroleum refineries. It is also in boilers, heat exchanger, condensers, pipelines, cooling towers, steam exhausts, and electric generation plants. It will also be found in fertilizer and chemical plants.
General Properties
Chemical Composition
Resistance to Corrosion
Physical Properties
Mechanical Properties
Welding
Heat Treatment
Cleaning
304/304L/304LN/304H Tubing and Pipe
Benefits of using 304H Stainless Steel
- Higher carbon content gives the material greater heat resistant qualities
- Higher tensile yield strength
- Greater short and long term creep strength
304H alloy is commonly found in the oil refining, gas and chemical industry and is used in industrial boilers, pressure vessels, heat exchangers, pipelines and condensers. The material is also used throughout the power generation industry.
ASTM Standards
| Bar |
Butt Weld Fittings |
Forgings |
Pipe, Welded & Seamless |
Tube, Welded |
Tube, Seamless |
Plate |
| A 276, A479 |
A403 |
A182 |
A312 |
A249 |
A213 |
A240 |
Chemical Composition
| UNS No |
Grade |
C |
Si |
Mn |
P |
S |
Cr |
Mo |
Ni |
N |
| S30409 |
304H |
0.04/0.10 |
0.75 |
2.00 |
0.045 |
0.030 |
18.00/20.00 |
– |
8.00/10.50 |
– |
Mechanical Properties
| UNS No |
Grade |
Proof Stress
0.2% (MPa) |
Tensile Strength
(MPa) |
Elongation
A5(%) |
Hardness Max |
| HB |
HRB |
| S30409 |
304H |
205 |
515 |
40 |
201 |
92 |
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