AISI / Alloy Steel 9850

Chemical Analysis
C% Carbon
0.48– 0.53
Mn% Manganese
0.70 – 0.90
P% Phosphorus
0.040 max
S% Sulfur
0.040 max
Si% Silicon
0.20 – 0.35
Ni% Nickel
0.85 – 1.15
Cr% Chromium
0.70 – 0.90
Mo% Molybdenum
0.20 – 0.30

General characteristics of Alloy Steel 9850

This is a nickel-chrome-molybdenum steel with excellent hardenability, strength and toughness.


This alloy is suited to production of highly stressed forged components of large cross section for aircraft, automotive and general engineering applications, such as propeller shafts, connecting rods, gear shafts, crankshafts and landing gear components, and for heavy forgings such as rotors, shafts and discs. This alloy will attain higher strength levels than alloy 9840, hence it will be used in applications requiring even greater strength than might be obtained from 9840 grade.


This alloy would be forged between 2100 and 1700ºF (1150 and 925ºC.) Parts should preferably be slow cooled after forging, otherwise transferred to a furnace held at an equalization temperature.

Heat treatment

Annealing: Austenitize at 1525ºF (830ºC) and slow cool from 1290 to 1200ºF (iso anneal) to give coarse pearlite structure for optimum machinability.

Normalizing: At 1600ºF (870ºC) followed by air cool.

Hardening: from 1500-1550ºF (815-840ºC) and oil quench for thin, intricate shapes, water quench for large, simple shapes.

Tempering: from 1000-1250ºF(540-680ºC) as per required properties.

Machinability:: this alloy may be readily machined, preferably from a coarse pearlitic structure.

Weldability:: pre-heat and post-weld stress relief are recommended for welding of this alloy. Welding should not be carried out in the hardened and tempered condition.

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