Characteristics and purpose of ASTM A194 standard
The ASTM A194 specification covers a wide range of steel and stainless steel nuts designed for use in high-temperature and low-temperature, high-pressure or highly corrosive environments. The nuts are machined and, in many cases, heat-treated to ensure high mechanical properties. The standard includes stringent requirements in terms of:
- Chemical composition
- Mechanical strength (yield and tensile strength, proof test)
- Heat Treatments
- Mechanical and metallographic testing
- Markings and traceability
Main grades of nuts ASTM A194
The standard includes several grades, each with specific technical characteristics and fields of application:
- Grade 8: 304L stainless steel, for non-corrosive environments.
- Grade 8M: 316L stainless steel, for more aggressive conditions, such as marine and chemical environment.
- Grade 8T: 316Ti stainless steel stabilized with titanium, for use at high temperatures without loss of inter-granular corrosion resistance.
- Grade 8R: austenitic steel type XM-19 UNS S20910 suitable for applications where high mechanical strength is required.
- Grade 8MLCuN: Super austenitic steel type UNS S31254 used for applications in aggressive environments containing chlorides and seawater.
- Grade 8S: super austenitic steel type UNS S21800 used for seawater applications.
Typical applications of ASTM A194 nuts.
Nuts produced according to ASTM A194 find use in highly technical fields where mechanical or environmental stresses are significant:
- Oil & Gas: flanges, valves and high-pressure equipment
- Petrochemical: reactors, heat exchangers, distillation columns
- Thermoelectric plants: boilers, turbines, high temperature fittings
- Marine industry: structural applications and accessories subject to salt spray
- Infrastructure and tunnels: structural fixings subject to vibration or wet atmospheres
Bolt-nut couplings according to ASTM A194
One of the critical aspects in selecting a bolt + nut system is the compatibility between the materials. ASTM A194 nuts are designed to be compatible with:
- ASTM A193 B8M → coupled with nut A194 8M
- ASTM A193 B8 → coupled with nut A194 8
This interaction is critical to ensure that the bolted joint maintains its properties during operation.
Advantages of using ASTM A194 nuts.
Choosing ASTM A194 certified nuts means:
- Increase plant safety with reliable and tested materials
- Ensure the durability of the bolted joint even in extreme environments
- Obtain documented traceability with EN 10204 3.1 certification
- Comply with international regulations during procurement or inspection
These benefits translate into lower maintenance costs and greater long-term operational efficiency.
