What is ASTM A182 Grade F6a Stainless Steel?

ASTM A182 F6a is a forged martensitic stainless steel with 13 wt.% chromium. Martensitic stainless steels can be high-carbon or low-carbon steel alloys. The ASTM standard A182 describes the general set of specifications about several material grades. These material grades, for example ASTM A182 F6a class 1, are unique materials with different properties.

Naming 

ASTM 182 is a standard specification. This covers forged or rolled alloy and stainless steel pipe components to be used in pressure systems. Included are several grades of low-alloy steel, including martensitic, austenitic and ferritic-austenitic. 

The standard specification includes general requirements, manufacturing processes and heat treatment processes. 

F 6a is a grade which describes specifically the steel type (martensitic etc.), heat treatment type, the austenitising/solutioning temperature, cooling medium, quenching temperature, tempering temperature, composition and welding requirements. There are several classes of this grade including F6a Class 1, F6a Class 2, F6a Class 3 and F6a Class 4. 

Properties 

ASTM A182 F6a, Classes 1 – 4 all have a specified chemical composition consisting of 11.5 – 13.5 wt.% chromium, 0 – 1.0 wt.% manganese, 0 – 1.0 wt.% silicon, 0 – 0.5 wt.% nickel, 0 – 0.15 wt.% carbon, 0 – 0.04 wt.% phosphorus and 0 – 0.03 wt.% sulphur. 

All four classes have the same value for the reduction of area. The specifications for other mechanical properties, however, vary between the classes. Comparing them, ASTM A182 F6a Class 1 has the smallest Brinell hardness, tensile strength and yield strength and ASTM A182 F6a Class 4 has the highest. 

Applications 

Applications for this standard specification include steel piping, parts for pressure systems, flanges, fittings, valves and similar parts. It is also used for shafts on butterfly valves and stems on plug valves as well as parts for steel gate, globe and check valves.  

Due to the material’s various properties, ASTM A182 F6a is ideal for applications in which severe corrosion resistance is not required. It is recommended for use in the presence of oil, oil vapour, and mild corrosives at a temperature of up to 1000 °F (538 °C). 

Equivalent grades 

Equivalent grades to ASTM A182 F6a class 1 can be found on the ASTM A182 Grade F6a-1 material page.