The Rockwell hardness is one of the best techniques for checking the hardness of 304 full hard stainless steel. There are some other measuring systems for calculating the hardness of stainless steel, like Brinell hardness and Vickers hardness, in different value ranges. The Rockwell hardness is a very precise and well-known non-destructive metallurgical testing system among them. With the help of this testing method, we can determine whether the material is hard or soft.
The two brothers Stanly P. Rockwell and Hugh M. Rockwell invented the Rockwell hardness testing system in the early 1900s. In 1914, Stanley Rockwell obtained a patent for his testing technique. He updated the patent in 1919 to add the Rockwell scale chart. The most commonly used scales are scale C and scale B.
This guide is very helpful if you want to learn more about the Rockwell hardness of 304 full hard stainless steel.
What is full hard 304 stainless steel?
The full hard 304 stainless steel is a Nickel-Chromium alloy, which belongs to the austenitic stainless steel group. Full hard 304 stainless steel has high ductility and excellent forming and drawing properties. It has better corrosion resistance than grade 302 stainless steel. It is non-magnetic, but it got magnetic properties after cold working.
304 full hard is mostly resistant to salt spray and oxidizing acids. It has low carbon content; therefore, it reduces pitting corrosion susceptibility and the amount of carbide that precipitates in the heat-affected zone during welding.
Which hardness test is most widely used?
The Rockwell hardness testing system is most widely used due to its easy testing method and precise results. Rockwell’s method of testing is replaced older metal testing methods such as the time-consuming Vickers test and the overly damaging Brinell metal test, particularly for small parts.
Rockwell is the successful testing system has the following factors:
- The system needed to be simple to purchase and keep up with.
- The least harmful testing tools are required.
- Testing apparatus required simple implementation.
- It made operator oversight and training simple.
- The testing staff has to follow clear, documented standards.
- Users could get useful information from test findings.
The Rockwell hardness testing method fulfills all the requirements for the hardness testing of 304 stainless steel and all other grades of the austenitic stainless steel family. It is a very old method but still the best. You can see the scales of the Rockwell hardness in the following table.
Rockwell hardness scales and applications
| Scale | Abbreviation | Load Kgf (1 Kgf is equal to 9.80665 N) | Indenter | Application |
| A | HRA | 60 | 120-degree diamond cone | Cemented carbides, case-hardened steel |
| B | HRB | 100 | 1.588 mm steel sphere | Copper alloys, soft steel, aluminum alloys |
| C | HRC | 150 | 120-degree diamond cone | Steel, hard cast iron, titanium, deep case hardened steel |
| D | HRD | 100 | 120-degree diamond cone | Thin steel, medium case hardened steel |
| E | HRE | 100 | 3.175 mm steel sphere | Cast iron, aluminum, and magnesium alloys |
| F | HRF | 60 | 1.588 mm steel sphere | Annealed copper alloys, thin soft sheet metals |
| G | HRG | 150 | 1.588 mm steel sphere | Beryllium copper, malleable irons |
| H | HRH | 60 | 3.175 mm steel sphere | Aluminum, zinc, lead |
| K | HRK | 150 | 3.175 mm steel sphere | Very soft or thin materials, bearing materials |
What is the Rockwell hardness of 304 full hard?
Rockwell hardness testing system is a quicker and more reliable method for checking the hardness of 304 full hard stainless steel. It is preferable for both large and small-volume work pieces due to the relatively high load. The values of Rockwell hardness for all the temper conditions of 304 stainless steel can see in the following table.
| Temper condition of 304 | Rockwell hardness B HRB | Rockwell hardness C HRC |
| 1/4 Hard | 95-100 | 16-22 |
| Half hard | 100-106 | 22-31 |
| 3/4 Hard | 106-109 | 31-38 |
| Full hard | – | 38-41 |
Properties of 304 full hard stainless steel
304 full hard stainless steel is mostly used in industries due to its outstanding properties like excellent corrosion resistance and strength.
Mechanical properties
| Mechanical properties | Full Hard 304 |
| Tensile strength Min MPa | 1280 |
| Yield strength 0.2% Min MPa | 965 |
| Elongation | 0-3% |
| Shear strength MPa | 690 |
| Fatigue strength MPa | 440 |
| Poisson’s ratio | 0.29 |
| Fatigue strength MPa | 77 |
Thermal properties
| Thermal properties | 304 Full hard |
| Latent heat of fusion J/g | 290 |
| Maximum temperature corrosion °C | 420 |
| Maximum temperature mechanical °C | 710 |
| Specific heat capacity J/kg-K | 480 |
| Thermal conductivity W/m-k | 16 |
| Thermal Expansion µm/m-K | 17 |
Physical properties
| Density | Melting range | Modulus of Elasticity |
| 8.03 g/cm3 | 1400-1455 °C | 193 GPa |
Chemical composition
| Elements | Min | Max |
| Carbon | 0.08% | 0.08% |
| Manganese | 2.0% | 2.0% |
| Silicon | 1.0% | 1.0% |
| Chromium | 18.00% | 20.00% |
| Nickel | 8.00% | 10.50% |
| Phosphorus | 0.045% | 0.045% |
| Sulfur | 0.030% | 0.030% |
| Nitrogen | 0.10% | 0.10% |
| Iron | Balance | Balance |
Applications of 304 full hard stainless steel
The 304 stainless steel is the most widely used material in many applications like:
- Architectural panels
- In the production of pharmaceutical equipment
- Brewery and food industry
- Screws, bolts, nuts, and springs
- Beer kegs, bellows, chemical apparatus
- Coal hopper linings, evaporators,
- Feed water tubing, flexible metal hose,
- Hospital surgical apparatus,
- Hypodermic needles, kitchen sinks,
- Marine apparatus and fasteners, nuclear equipment, oil well filter screens, refrigeration apparatus, paper industry, pots and pans, pressure vessels, sanitary fittings, valves, and equipment for textile dyeing.
