AISI 8620 Steel | 1.6523 | 21NiCrMo2 | SNCM220

AISI 8620 Steel is a low alloy nickel, chromium, molybdenum case hardening steel, generally supplied in the as-rolled condition with a maximum hardness of HB 255max. SAE steel 8620 offers high external strength and good internal strength, making it highly wear resistant. AISI 8620 steel has a higher core strength than grades 8615 and 8617.

SAE 8620 alloy steel is flexible during hardening treatments, thus enabling improvement of case/core properties. Pre-hardened and tempered (un carburized) 8620 can be further surface hardened by nitriding but will not respond satisfactorily to flame or induction hardening due to its low carbon content.

Steel 8620 is suited for applications which require a combination of toughness and wear resistance. This grade is commonly supplied in round bar.

1. AISI 8620 Steel Supply Range

8620 Round Bar: diameter 8mm – 3000mm
8620 Steel Plate: thickness 10mm – 1500mm x width 200mm – 3000mm
8620 Square Bar: 20mm – 500mm
8620 tubes are also available against your detailed request.
Surface Finish: Black, Rough Machined, Turned or as per given requirements.

2. SAE 8620 Steel Specification and Relevant Standards

Country	USA	DIN	BS	BS	Japan
Standard	ASTM A29	DIN 1654	EN 10084	BS 970	JIS G4103
Grades	8620	1.6523/ 21NiCrMo2	1.6523/ 20NiCrMo2-2	805M20	SNCM220

3. ASTM 8620 Steels & Equivalents 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

4. AISI 8620 Steel Mechanical Properties

• 8620 Physical Properties:

Density (lb / cu. in.) 0.283
Specific Gravity 7.8
Specific Heat (Btu/lb/Deg F – [32-212 Deg F]) 0.1
Melting Point (Deg F) 2600
Thermal Conductivity 26
Mean Coeff Thermal Expansion 6.6
Modulus of Elasticity Tension 31

• 8620 Steel Mechanical Properties

Properties	Metric	Imperial
Tensile strength	530 MPa	76900 psi
Yield strength	385 MPa	55800 psi
Elastic modulus	190-210 GPa	27557-30458 ksi
Bulk modulus (typical for steel)	140 GPa	20300 ksi
Shear modulus (typical for steel)	80 GPa	11600 ksi
Poisson’s ratio	0.27-0.30	0.27-0.30
Izod Impact	115 J	84.8 ft.lb
Hardness, Brinell	149	149
Hardness, Knoop (converted from Brinell hardness)	169	169
Hardness, Rockwell B (converted from Brinell hardness)	80	80
Hardness, Vickers (converted from Brinell hardness)	155	155
Machinability (hot rolled and cold drawn, based on 100 machinabilities for AISI 1212 steel)	65	65

5. Forging of Material 8620 Steel

AISI 8620 alloy steel is forged at a start temperature of around 2250ºF (1230ºC) down to approximately 1700ºF(925ºC.) prior to the hardening heat treatment or carburizing. The alloy is air cooled after forging.

6. ASTM 8620 Steel Heat Treatment

• Annealing

AISI 8620 steel may be given a full anneal by heat to 820℃ – 850℃, and hold until temperature is uniform throughout the section and cool in furnace or air cooled.

• Tempering

Tempering of heat treated and water quenched parts of 8620 steels (not carburized) is done at 400 F to 1300 F to improve case toughness with minimal effect on its hardness. This will also reduce the possibility of grinding cracks.

• Hardening

The AISI steel 8620 will be austenitized at around 840°C – 870°C, and oil or water quenched depending upon section size and intricacy. Cool in Air or Oil required.

• Normalizing

1675ºF (910ºC) and air cool. This is another method of improving machinability in 8620 material; normalizing might also be used prior to case hardening.

7. Machinability of SAE 8620 Steel

The 8620 alloy steel is readily machined after heat treatment and/or carburizing, should be at a minimum so as not to impair the hardened case of the part. Machining may be done by conventional means prior to heat treatment – after carburizing machining is usually limited to grinding.

8. Welding of 8620 Materials

The alloy 8620 may be welded as rolled condition by conventional methods, usually gas or arc welding. Preheating at 400 F is beneficial and subsequent heating after welding is recommended – consult the approved weld procedure for the method used. However, welding in the case hardened or through hardened condition is not recommended

9. Application of ASTM 8620 Steel

AISI 8620 steel 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.