AISI / Alloy Steel 4330

Chemical Analysis
C% Carbon
0.30 – 0.34
Mn% Manganese
0.75 – 1.00
P% Phosphorus
0.025 max
S% Sulfur
0.010 max
Si% Silicon
0.15 – 0.35
Cr% Chromium
0.75 – 1.00
Ni% Nickel
1.65 – 2.00
Mo% Molybdenum
0.40 – 0.50
V% Vanadium
0.05 – 0.10

General characteristics of Alloy Steel 4330

This is a fine-grained, medium carbon, chromium-nickel-molybdenum alloy steel with good hardenability, and excellent transverse strength and toughness. It also shows excellent low-temperature impact properties.


This alloy finds forging applications as aircraft landing gear, and in other high-performance applications where toughness and wear resistance are required. The alloy is used in the oil and gas industry as raise bore drill rods and as drive subs for downhole motors.


Bars are forged to approximate dimensions, rough machined and bored (as required) prior to heat treatment. Preheat steel carefully then raise to 1950-2250ºF (1070-1230ºC) start forge temperature. Not to be forged below 1560ºF (850ºC) and slow cooling in ash or lime is recommended.

Heat treatment

Annealing: Heat slowly to 1510-1580ºF (820-860ºC), soak and slow furnace cool to 1075ºF (580ºC) and air cool.

Normalizing: this steel should be normalized at 1600-1700ºF (870-925ºC) and air cooled

Hardening: at 1550-1600ºF (845-870ºC) and water or oil quench according to size and intricacy of part.

Tempering: to desired strength levels, based on available data and experience.

Machinability: It is reported that best machinability is obtained in the normalized and tempered – at 1250ºF (675ºC) – condition.

Weldability: Preheat and post-weld stress relief recommended if this alloy is to be welded . It should be welded in the annealed condition only.

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