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8620 1.6523 SNCM220 alloy structural steel

8620 alloy structural steel offers excellent case-hardening response, high core strength, and outstanding fatigue resistance. With good hardenability and toughness, ideal for gears, shafts, bearings, and other heavy-duty automotive transmission components.

Standard: AISI 8620, DIN 1.6523(20NiCrMo2), JIS SNCM220, GB 20CrNiMo
Technique: EAF + LF + VD, forged or hot-rolled, multidirectional forging ratio ≥4, spheroidized annealed
Shape: Round, Flat, Plates, Blocks
Heat treatment: Supplied in annealed condition, hardness ≤229 HBW; normalized or prehardened (QT) condition available on request
Surface Treatment: Turned, milled / ground, sawn ends. Black (hotrolled / forged surface) available for large sections
Tolerance: flat bars & plates thickness: +0.5/-0.0 mm (turned); forged blocks: ±0.2 mm
MOQ: 1 Ton

We supply AISI 8620 in various custom sizes

Chemical Composition (%)

Grade	C	Si	Mn	P (≤)	S (≤)	Cr	Ni	Mo
8620	0.18–0.23	0.15–0.35	0.70–0.90	0.035	0.035	0.40–0.60	0.40–0.70	0.15–0.25
1.6523 (20NiCrMo2-2)	0.17–0.23	≤0.40	0.60–0.90	0.025	0.035	0.35–0.70	0.40–0.70	0.15–0.25
SNCM220	0.17–0.23	0.15–0.35	0.60–0.90	0.030	0.030	0.40–0.65	0.40–0.70	0.15–0.30
20CrNiMo	0.17–0.23	0.17–0.37	0.60–0.90	0.025	0.025	0.40–0.70	0.40–0.70	0.15–0.25

Main characteristics of 8620 alloy steel

8620 | 1.6523 | SNCM220 alloy steel applications

8620 steel for Automotive Transmission Gear

Excellent case hardenability and tough core provide high contact fatigue strength and wear resistance, ensuring quiet and reliable gear shifting.

8620 steel for Heavy-Duty Drive Pinion

High surface hardness after carburizing combined with good bending fatigue strength withstands extreme torque and shock loads in construction machinery.

8620 steel for Oil Field Rock Bit Journal

Outstanding core toughness and case wear resistance resist severe abrasive wear and impact, delivering reliable performance in downhole drilling.

Our Production Technology For 8620 (21NiCrMo2 / 1.6523 / SNCM220) Case-Hardening alloy steel

mechanical properties & heat treatment of 8620 steel

Heat temperature	Start forging temperature	Finish forging temperature	Cooling method
1200 – 1240 °C	1200 – 1150 °C	≥ 900 °C	Pit, sand, or furnace cooling

Annealing

Annealing temperature: 820 – 850°C (1550°F)
Hold at temperature for sufficient time (at least 1 hour per 25mm of section thickness)
Cool slowly in the furnace at a controlled rate of not more than 50°F (10°C) per hour down to 850°F (455°C)
Then air cool to room temperature
Hardness after annealing: 149 HB (typical)

Hardening

8620 is a carburizing alloy steel. The carburizing process is critical to achieve the desired case hardness and core toughness combination. The steel may be hardened by heating to 815°C (1500°F) followed by a water quench
Carburizing:
Carburizing temperature: 900 – 925°C (1650 – 1700°F).
Alternative: 885°C for 120 minutes
Carburizing medium: Gas, pack, or salt bath
Carburizing time: Controlled according to the carbon potential and the required case depth
Cooling from carburizing temperature: Pot cool (furnace cool)
Direct Quench (Single Quench) :
Reheat to hardening temperature: 845°C (1550°F)
Quenching media: Oil (agitated).
For thin sections: oil quench directly from carburizing.
For heavier sections (over 3/4″): furnace cool, then reheat to 845°C before oil quench
Double Quench (Improved Case/Core Properties) :
Carburize at 925°C (1700°F) for 8 hours
Pot cool
Reheat to 845°C (1550°F)
Quench in agitated oil
Reheat to 800°C (1470°F)
Quench in agitated oil
Hardness after quenching:
Surface hardness: up to 62 HRC.
Core hardness: approximately 30–35 HRC (typical for carburized case-hardened components)

Stress relieving

Perform after rough machining, heavy stock removal, or other cold working operations to reduce residual stresses
Heat carefully to 600 – 650°C (below the tempering temperature)
Hold at temperature for 1 hour per 25mm of section thickness (minimum 2 hours)
Air cool after holding
This operation reduces the risk of distortion during final heat treatment and improves dimensional stability

Tempering

Temper immediately after quenching when the temperature reaches about 70°C. Delayed tempering may cause cracking
Tempering temperature: 150 – 200°C (300 – 450°F).
Alternative: 230°C (450°F) for single quenched and tempered condition.
For carburized parts: 250 – 300°F (120 – 150°C)
Holding time: At least 1 hour
Cooling method: Air cool after tempering
Purpose: There is no significant drop in hardness at this temperature range, but it ensures better resistance to fracture and prevents the formation of surface cracks during grinding

Why Choose NSPM as Your 8620 alloy steel Supplier

Source Direct

Direct mill cooperation ensures stable supply, competitive pricing, and consistent quality. Global resource integration and strong supply chain management guarantee reliable material sourcing and long-term availability.

Stock Ready

50,000+ tons inventory across 11 warehouses enables fast delivery. Flexible cutting, short lead times, and ready stock support urgent demands and improve customers’ production efficiency.

Expert Team

600+ professionals, including R&D specialists and technical engineers, provide application-driven support. Fast response and deep tooling knowledge ensure accurate solutions for diverse industrial needs.

Fully Inspected

Strict quality control system with full traceability, UT testing, and heat treatment records. Certified standards (ISO, CE) ensure every material meets high-performance and reliability requirements.

Full-Chain Machining

From steel supply to precision machining, heat treatment, and equipment manufacturing, NSPM offers integrated solutions that enhance accuracy, efficiency, and overall tooling performance.