AISI 8620 Steel Forging

AISI 8620 is a type of alloy steel, which composed of iron, carbon, silicon, molybdenum, manganese, nickel, chromium, sulphur and phosphorus. These ingredient elements must be within certain weight percentages to create the 8620 alloy. It takes advantages of good strength and toughness properties, and has a higher core strength than grades 8615 and 8617. The equivalent Chinese material of AISI 8620 alloy steel is 20CrNiMo, which is a common material grade in steel forging.

Chemical Composition

Standard	Grade	C	Mn	P	S	Si	Ni	Cr	Mo
ASTM A29	8620	0.18-0.23	0.7-0.9	0.035	0.040	0.15-0.35	0.4-0.7	0.4-0.6	0.15-0.25
DIN 1654	1.6523/ 21NiCrMo2	0.17-0.23	0.65-0.95	0.035	0.035	≦0.40	0.4-0.7	0.4-0.7	0.15-0.25
EN 10084	1.6523/ 20NiCrMo2-2	0.17-0.23	0.65-0.95	0.025	0.035	≦0.40	0.4-0.7	0.35-0.70	0.15-0.25
JIS G4103	SNCM220	0.17-0.23	0.6-0.9	0.030	0.030	0.15-0.35	0.4-0.7	0.4-0.65	0.15-0.3
BS 970	805M20	0.17-0.23	0.6-0.95	0.040	0.050	0.1-0.4	0.35-0.75	0.35-0.65	0.15-0.25

Forging

This alloy is forged at a start temperature of around 2250ºF (1230ºC) and could be forged down to approximately 1700ºF(925ºC.) The alloy is air cooled after forging. The method of forging AISI 8620 steel used is closed die forging, which is very suitable for small precision components.

Heat Treatment

Annealing: For optimum machinabilty, an as-forged structure is normally sufficient for this grade of alloy steel. If this proves not to be the case then an iso-anneal from around 1650ºF (900ºC) to 1225ºF (660ºC) will improve machinability.

Normalizing: 1675ºF (910ºC) and air cool. This is another method of improving machinability in this grade; normalizing might also be used prior to case hardening.

Hardening: The alloy will be austenitized at around 1525ºF (830ºC) and oil or water quenched depending upon section size and intricacy.

Tempering: To desired hardness, using temperatures based on past experience, following water or oil quench.

Machinability: This grade of alloy is readily machined following suitable cooling from forging or subsequent heat treatment.

Weldability: This steel may be welded by normal fusion methods, but prior to carburizing or hardening and tempering.

Application of AISI 8620 Steel Forging

AISI 8620 steel forging material is used extensively by all industry sectors for light to medium stressed components and shafts requiring high surface wear resistance with reasonable core strength and impact properties.

Typical applications are: Arbors, Bearings, Bushings, Cam Shafts, Differential Pinions, Guide Pins, King Pins, Pistons Pins, Gears, Splined Shafts, Ratchets, Sleeves and other applications where it is helpful to have a steel that can be readily machined and carburized to controlled case depths.

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