Most forgings are made from carbon steels, alloy steels for hardening and tempering, case-hardening steels, or stainless steels. The right grade depends on the load the part carries, the heat treatment it will get, and any code or standard it must meet.
Indian forging units work with European, American, British and Indian grade names, often for the same steel. Knowing the common families helps you check that the grade quoted is the grade you asked for.
Carbon steels
Medium carbon steels are the workhorses of general forging. C45 under EN 10083, AISI 1045 under American naming, and EN8 in older British naming are broadly similar steels with roughly 0.35 to 0.5% carbon. They suit shafts, pins, flanges and general machine parts that are normalised or lightly hardened.
For pressure flanges and fittings, ASTM A105 is the usual carbon steel forging specification. Low temperature service often calls for ASTM A350 LF2 instead.
Alloy steels for hardening and tempering
Where strength and toughness matter, alloy steels are hardened and tempered. These are the families you will see most often:
- 42CrMo4, also seen as AISI 4140 and close to EN19, is a chromium-molybdenum steel for shafts, gears and high-strength bolts.
- 34CrNiMo6, close to EN24 and similar in purpose to AISI 4340, adds nickel for higher toughness in heavy sections.
- ASTM A182 F11 and F22 are chromium-molybdenum grades for high-temperature pressure forgings.
Case-hardening and stainless steels
Case-hardening steels such as 16MnCr5 and 20MnCr5 have low carbon in the core. They are carburised so the surface becomes hard and wear-resistant while the core stays tough. They are common for gears, pinions and splined shafts.
Stainless forgings use austenitic grades such as 304 and 316, often ordered as ASTM A182 F304 and F316, for corrosion resistance. Duplex and martensitic grades are used for higher strength. Each has its own heat treatment rules.
Grade names are not always equivalent
Cross-reference tables are a guide, not a guarantee. Two grades that look equivalent can have different limits on carbon, sulphur, phosphorus or alloying elements, and different required properties. Write the exact standard and grade on your drawing and order.
Ask the forging unit where its steel comes from and for the steel mill's certificate as well as its own material test certificate. The forging unit's certificate should trace back to the mill heat. Mixed or untraceable bar stock is a common cause of failures.
Choosing a grade
- Start from the loads, operating temperature and environment of the part.
- Decide the heat treatment and target hardness, since the grade must be able to reach them in your section size.
- Check whether a code or customer specification already fixes the grade.
- Consider machinability, weldability and availability in Indian bar sizes.
Next step
The heat treatment that goes with each grade is covered in heat treatment for forgings. We check grades, mill certificates and test results for every lot before shipment. To review your forging, book a free sourcing review.