 304H Stainless Steel Pipes & Tubes
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 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.
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.
Product Range
Specifications: ASTM A/ASME SA213/A249/A269/A312/A358 CL. I to V ASTM A789/A790
Sizes (Seamless): 1/2” NB - 24” NB
Sizes (ERW): 1/2” NB - 24” NB
Sizes (EFW): 6” NB - 100” NB
Wall Thickness available:
Schedule 5S - Schedule XXS (heavier on request)
Other Materials Testing:
NACE MR0175, H2 SERVICE, OXYGEN SERVICE, CRYO SERVICE, etc.
Dimensions:
All Pipes is manufactured and inspected/tested to the relevant standards including ASTM, ASME and API etc.
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Background : |
Grade 304 is the standard "18/8" stainless; it is the most versatile and most widely used stainless steel, available in a wider range of products, forms and finishes than any other. It has excellent forming and welding characteristics. The balanced austenitic structure of Grade 304 enables it to be severely deep drawn without intermediate annealing, which has made this grade dominant in the manufacture of drawn stainless parts such as sinks, hollow-ware and saucepans. For these applications it is common to use special "304DDQ" (Deep Drawing Quality) variants. Grade 304 is readily brake or roll formed into a variety of components for applications in the industrial, architectural, and transportation fields. Grade 304 also has outstanding welding characteristics. Post-weld annealing is not required when welding thin sections.
Grade 304L, the low carbon version of 304, does not require post-weld annealing and so is extensively used in heavy gauge components (over about 6mm). Grade 304H with its higher carbon content finds application at elevated temperatures. The austenitic structure also gives these grades excellent toughness, even down to cryogenic temperatures. |
Composition
Typical compositional ranges for grade 304 stainless steels are given in table 1.
Table 1. Composition ranges for 304 grade stainless steel
| Grade |
|
C |
Mn |
Si |
P |
S |
Cr |
Mo |
Ni |
N |
| 304 |
min. |
- |
- |
- |
- |
- |
18.0 |
- |
8.o |
- |
| max. |
0.08 |
2.0 |
0.75 |
0.045 |
0.030 |
20.0 |
- |
10.5 |
0.10 |
| 304L |
min. |
- |
- |
- |
- |
- |
18.0 |
- |
8.o |
- |
| max. |
0.030 |
2.0 |
0.75 |
0.045 |
0.030 |
20.0 |
- |
12.0 |
0.10 |
| 304H |
min. |
0.04 |
- |
- |
- |
- |
18.0 |
- |
8.o |
- |
| max. |
0.10 |
2.0 |
0.75 |
0.045 |
0.030 |
20.0 |
- |
10.5 |
- |
Mechanical Properties
Typical mechanical properties for grade 304 stainless steels are given in table 2
Table 2. Mechanical properties of 304 grade stainless steel
| Grade |
Tensile Strength (MPa) min |
Yield Strength 0.2% Proof (MPa) min |
Elongation (% in 50mm) min |
Hardness |
| Rockwell B (HR B) max |
Brinell (HB) max |
| 304 |
515 |
205 |
40 |
92 |
201 |
| 304L |
485 |
170 |
40 |
92 |
201 |
| 304H |
515 |
205 |
40 |
92 |
201 |
| 304H also has a requirement for a grain size of ASTM No 7 or coarser. |
Physical Properties
Typical physical properties for annealed grade 304 stainless steels are given in table 3.
Table 3. Physical properties of 304 grade stainless steel in the annealed condition
| Grade |
Density (kg/m3) |
Elastic Modulus (GPa) |
Mean Coefficient of Thermal Expansion (m/m/°C) |
Thermal Conductivity (W/m.K) |
Specific Heat 0-100°C (J/kg.K) |
Electrical Resistivity (n.m) |
| 0-100°C |
0-315°C |
0-538°C |
at 100°C |
at 500°C |
| 304/L/H |
8000 |
193 |
17.2 |
17.8 |
18.4 |
16.2 |
21.5 |
500 |
720 |
Grade Specification Comparison
Approximate grade comparisons for 304 stainless steels are given in table 4.
Table 4. Grade specifications for 304 grade stainless steel
| Grade |
UNS No |
Old British |
Euronorm |
Swedish SS |
Japanese JIS |
| |
|
BS |
En |
No |
Name |
|
|
| 304 |
S30400 |
304S31 |
58E |
1.4301 |
X5CrNi18-10 |
2332 |
SUS 304 |
| 304L |
S30403 |
304S11 |
- |
1.4306 |
X2CrNi19-11 |
2352 |
SUS 304L |
| 304H |
S30409 |
304S51 |
- |
1.4948 |
X6CrNi18-11 |
- |
- |
These comparisons are approximate only. The list is intended as a comparison of functionally similar materials not as a schedule of contractual equivalents. If exact equivalents are needed original specifications must be consulted. |
Corrosion Resistance
Excellent in a wide range of atmospheric environments and many corrosive media. Subject to pitting and crevice corrosion in warm chloride environments, and to stress corrosion cracking above about 60°C. Considered resistant to potable water with up to about 200mg/L chlorides at ambient temperatures, reducing to about 150mg/L at 60°C.
Heat Resistance
Good oxidation resistance in intermittent service to 870°C and in continuous service to 925°C. Continuous use of 304 in the 425-860°C range is not recommended if subsequent aqueous corrosion resistance is important. Grade 304L is more resistant to carbide precipitation and can be heated into the above temperature range.
Grade 304H has higher strength at elevated temperatures so is often used for structural and pressure-containing applications at temperatures above about 500°C and up to about 800°C. 304H will become sensitised in the temperature range of 425-860°C; this is not a problem for high temperature applications, but will result in reduced aqueous corrosion resistance
Heat Treatment
Solution Treatment (Annealing) - Heat to 1010-1120°C and cool rapidly.
These grades cannot be hardened by thermal treatment.
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