Case Hardening AISI 8620 Alloy Steel

Product Overview

AISI 8620 Case Hardening Steel (DIN 20NiCrMo2-2 1.6523, JIS SNCM220, BS 805M20) is a high-performance Ni-Cr-Mo alloy steel designed for carburizing applications. Compliant with EN 10084 and ISO 683-11 standards, this grade is celebrated for its ability to deliver exceptional surface hardness paired with superior core toughness—making it indispensable for high-load, wear-prone components. With global equivalents including China’s 20CrNiMo (GB/T 3077), DIN 20NiCrMo2-2 1.6523 Steel is a trusted choice in automotive, heavy machinery, and gear manufacturing industries. Its carbon content of 0.17-0.23% balances weldability and carburizing response, while alloying elements (Ni, Cr, Mo) enhance fatigue resistance and hardenability.

Key Product Features

Exceptional Carburizing Performance

After carburizing, quenching, and tempering, JIS SNCM220 Alloy Steel achieves a hard, wear-resistant surface (ideal for high-contact components) and a tough core (absorbing impact loads without cracking).

This grade offers impressive tensile strength (up to 1160 Mpa for d=16mm), yield strength (560 Mpa Min), and impact resistance (25J Min at RT)—perfect for components subjected to dynamic stresses.

Reliable Weldability & Hardenability

With carbon content below 0.25%, BS 805M20 Steel maintains good weldability. Its Ni-Cr-Mo composition ensures deep hardenability, allowing consistent properties across thick sections.

Available as hot-rolled bars (Φ8-Φ270mm), hot-forged bars (Φ100-Φ1200mm), plates (T:20-120mm), and blocks—supporting diverse manufacturing needs from small fasteners to large gear shafts.

1: Steel equivalent

Country	USA	Europe	China	British	Japan
Standard	ASTM A29	EN10084	GB/T3077	BS970	JIS G4105
Grade	8620	20NiCrMo2-2/1.6523	20CrNiMo	805M20	SNCM220

2: Chemical composition

Grade	C	Si	Mn	P	S	Cr	Mo	Ni
8620	0.18-0.23	0.15-0.35	0.70-0.90	0.035Max	0.040Max	0.4-0.6	0.15-0.25	0.40-0.70
20NiCrMo2-2/1.6523	0.17-0.23	0.40Max	0.65-0.95	0.025Max	0.035Max	0.35-0.7	0.15-0.25	0.40-0.70
20CrNiMo	0.17-0.23	0.17-0.37	0.60-0.95	0.030Max	0.030Max	0.4-0.7	0.20-0.30	0.35-0.75
805M20	0.17-0.23	/	0.60-0.95	0.035Max	0.035Max	0.35-0.65	0.15-0.25	0.35-0.75
SNCM220	0.17-0.23	0.15-0.35	0.60-0.90	0.030Max	0.030Max	0.40-0.65	0.15-0.30	0.40-0.70

3: Mechanical properties

Steel grades 20NiCrMo2-2 according to minimum tensile strength as a function of diameter after hardening and tempering at 200℃ according to EN10084.

Size range	Tensile strength
d≤16	1100Mpa Min
16＜d≤40	700Mpa Min
40＜d≤100	500Mpa Min

Mechanical properties for reference test bar in the simulated case-hardening condition according to ISO 683-11-1987.

Size range	Tensile strength	Yield strength	Alongation	Impact value At RT/J
d=16	810-1160Mpa	560Mpa Min	9% Min	25J Min
d=30	730-1080Mpa	510Mpa Min	10% Min	30J Min
d=63	660-1010Mpa	470Mpa Min	11% Min	30J Min

Sampling and preparation of test pieces for 20NiCrMo2-2 case-hardening steel.

1): According to EN10084, all samples shall be taken at a distance of 1/4 of the diameter or thickness below the heat-treated surface.

2): As stipulated in the contract between buyer and seller.

4: Surface hardness and hardenability

Heat Treatment	Hardness
Treated to improve shearability (+S)	HB255Max
Soft annealed (+A)	HB212Max
Treated to hardness range(+TH)	161-212HBW
Treated to ferrite-pearlite structure and hardness range(+FP)	149-194HBW

Where the steel is ordered by using the symbols for normal (+H) or restricted (+HL, +HH) hardenability requirements, the hardenability values should apply below:

Distance in mm from quenched end
Distance		1.5	3	5	7	9	11	13	15	20	25	30	35	40
Hardness In HRC + H	max	49	48	45	42	36	33	31	30	27	25	24	24	23
	min	41	37	31	25	22	20	/	/	/	/	/	/	/
Hardness In HRC + HH	max	49	48	45	42	36	33	31	30	27	25	24	24	23
	min	44	41	36	31	27	24	22	21	/	/	/	/	/
Hardness In HRC + HL	max	46	44	40	36	31	29	27	26	23	21	20	20	/
	min	41	37	31	25	22	20	/	/	/	/	/	/	/

Scatter bands for the Rockwell - C hardness in the end quench hardenability test.

5: Supply size & Tolerance & Stock size

Product type	Size range	Length
Hot rolled bar	Φ8-Φ270mm	6000-9000mm
Hot forged bar	Φ100-Φ1200mm	3000-5800mm
Hot rolled plate/sheet	T:20-120mm; W:1500-2500mm	2000-5800mm
Hot Forged block	T: 80-800mm; W: 100-2500mm	2000-5800mm

Surface Finish	Turned	Milled	Grinding(Best)	Polished(Best)	Peeled(Best)	Black Forged	Black Rolled
Tolerance	+0/+3mm	+0/+3mm	+0/+0.05mm	+0/+0.05mm	+0/+0.1mm	+0/+5mm	+0/+1mm
Straighness	1mm/1000mm max.					3mm/1000mm max.

Qilu steel stock hot rolled bar and forged bars more than ten thousands tons every month, below our our stock size.

1): Stock diameter for hot rolled bar

8	10	12	14	16	18	20	22	25	26	28	30	32	35	36
38	40	42	45	50	55	60	65	70	75	80	85	90	95	100
105	110	115	120	125	130	135	140	145	150	160	170	180	185	190
200	210	220	230	240	250	260	270

Since the stocks change everyday, if you want to know our stock available information, please contact our salesman.

6：Forging processing

Put the 20NiCrMo2-2 ingot into the furnace and heat to 1150-1200℃

Forge the ingot, forging temperature should be not less than 850℃

Cooling in the air after forged

7: Heat treatment

Soft annealed:

Heat 20NiCrMo2-2 steel to 820-850℃ in the furnace

Soak at this temperature in the furnace

Cooling in the furnace or in the air

Normalized:

Heat 20NiCrMo2-2 steel to 880-920℃ in the furnace

Soak at this temperature in the furnace

Cooling in the air

End quench test Austenitizing temperature: 920℃

Carburizing temperature: 880-980℃

Core-hardening temperature: 860-900℃

Case-hardening temperature: 780-820℃

Quenching and tempering:

Heat 20NiCrMo2-2 steel to 850-880℃ in the furnace

Soak at this temperature in the furnace

Quench in water or oil

Temper steel at 150-200℃ in the furnace

Take out of 20NiCrMo2-2 steel from furnace and cool in the air.

Remark: The conditions given above are for guidance, at the temperatures at the lower end of the range are generally applicable to hardening in water and those at the upper end for hardening in oil.

8: Weldability

20NiCrMo2-2 steel has good weldability. For steel materials, weldability is strongly influenced by the carbon content. When the carbon content exceeds 0.25%, the weldability decreases. The carbon content of 20NiCrMo2-2 is usually in the range of 0.17% - 0.23%, which is relatively moderate.

Application Scenarios

Gear Manufacturing

Automotive gears: Transmission gears, differential gears (high wear resistance + impact tolerance)

Industrial machinery gears: Low-speed to medium-speed gears for heavy equipment

Wind power equipment gears: Withstands cyclic loads and outdoor conditions

Shaft & Rotating Components

Transmission shafts: For automobiles and heavy machinery (balances strength and fatigue resistance)

Crankshafts: Lightweight yet durable for engine applications

High-Strength Fasteners

Bolts, nuts, and studs: For critical joints in machinery and automotive chassis (high tensile strength)

Tools & Molds

Cold work molds: Stamping tools and low-load dies (carburized surface for wear resistance)

FAQ

What is the surface hardness of AISI 8620 Steel after carburizing?

After proper carburizing and heat treatment, the surface hardness typically ranges from 58-62 HRC, while the core remains tough (28-32 HRC).

What are the key differences between AISI 8620 and standard carbon steel?

AISI 8620 is an alloy steel with Ni, Cr, and Mo additions—offering better hardenability, fatigue resistance, and wear performance than low-carbon steels like AISI 1020.

Can DIN 20NiCrMo2-2 1.6523 Steel be used for high-temperature applications?

It performs well in moderate high-temperature environments (up to 300℃). For extreme heat, additional heat-resistant alloys may be preferred.

What supply tolerances are available for JIS SNCM220 Steel?

Surface finishes include grinding (±0/+0.05mm), peeling (+0/+0.1mm), and black rolled (+0/+1mm), with straightness up to 1mm/1000mm Max for precision applications.