304H stainless steel, sometimes referred to by its regional specifications UNS S30400 and S30409, is an impressive “18-8” austenitic stainless steel comprising a carefully balanced combination of chromium (18%) and nickel (8%). Creatively conceived and economically engineered, its major selling points are its exceptional yield strength and versatile anti-corrosion properties. By adding these newly improved capabilities to a long list of existing attributes – such as robustness and shock-resistance – 304H stainless steel is a greatly evolved material.
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.
Comparative Characteristics of 304H and 304L Stainless Steel
Carrying extremely similar chemical and mechanical properties, type 304H and 304L stainless steel possess one subtle but significant difference: carbon content. 304H stainless steel can contain up to 0.08% carbon, as opposed to 304L which commonly contains a maximum of 0.03%. This may seem a trifling disparity but even a slight increase in carbon can greatly bolster the corrosion resistance of steel alloys.
304H stainless steel grades are subsequently superior to 304L derivatives in terms of chemical characteristics. In fact, 304H has a clear advantage over many alloys that have come before.
Advantages of 304H Stainless Steel
Among the most notable benefits of 304H stainless steel’s increased carbon content is its greater resilience in high temperature environments. It also benefits from good workability, lending 304H grades to key structural applications requiring high-strength plates and parts for complex or challenging features. A tried and tested tolerance for extreme thermal conditions, as well as good physical durability is further evidence of 304H stainless steel’s suitability for an ever-growing scope of industrial jobs. This durability is guaranteed over the long term even when applied in severe processing/storage environments like boilers and pressure vessels, due to the superb creep resistance of 304H stainless in both the short and long term.
Chemical Composition of Grade 304H Stainless Steel
The chemical composition of Grade 304H Stainless Steel is provided in the table below.
| 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 | 0.10 |
Mechanical Properties of Grade 304H Stainless Steel
The mechanical properties of Grade 304H Stainless Steel are provided in the table below.
| UNS No | Grade | Proof Stress 0.2% (MPa) |
Tensile Strength (MPa) |
Elongation A5(%) |
Hardness Max | |
| HB | HRB | |||||
| S30409 | 304H | 205 | 515 | 40 | 201 | 92 |