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20MnCr5 5120 1.7147 SMnC420H alloy structural steel

20MnCr5 alloy structural steel offers excellent case-hardening response, good core toughness, and high surface wear resistance. With good hardenability and machinability, ideal for gears, pinions, shafts, and other automotive transmission components.

Standard: ISO 20MnCr5, AlSI 5120, DIN1.7147, JIS SMnC420H, GB 20CrMn
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 ≤217 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 ISO 20MnCr5 in various custom sizes

Chemical Composition (%)

Grade	C	Si	Mn	P (≤)	S (≤)	Cr
20MnCr5	0.17–0.22	≤0.40	1.10–1.40	0.035	0.035	1.00–1.30
1.7147 (20MnCr5)	0.17–0.22	≤0.40	1.10–1.40	0.035	0.035	1.00–1.30
5120	0.17–0.22	0.15–0.35	0.70–0.90	0.035	0.040	0.70–0.90
SMnC420H	0.16–0.23	0.15–0.35	1.15–1.55	0.030	0.030	0.35–0.70
20CrMn	0.18–0.24	0.17–0.37	0.90–1.20	0.030	0.030	0.90–1.20

Main characteristics of 20MnCr5 alloy steel

20MnCr5 | 5120 | 1.7147 | SMnC420H alloy steel applications

20MnCr5 steel for Automotive Transmission Gear

Excellent case hardenability and tough core provide high wear resistance and bending fatigue strength, ensuring reliable, quiet gear shifting under heavy loads.

20MnCr5 steel for Differential Gear

High surface hardness after carburizing combined with good impact toughness withstands the extreme contact stresses and shock loads in differential applications.

20MnCr5 steel for Steering Knuckle & Drive Shaft

Deep hardenability and balanced core strength deliver the structural durability and safety required for critical chassis and drivetrain components.

Our Production Technology For 20MnCr5 (1.7147 / 5120) Case-Hardening Alloy Steel

Ultrasonic testing (UT) 100% as per SEP 1921, ASTM A388, or EN 10228-3 (upon request)
Micro Cleanliness as per ASTM E45 or DIN 50602 (upon agreement)
Grain size as per ASTM E112 (typical ≥ 5 for critical applications)
Delivery condition options:
Soft annealed (+A): max. 217–248 HB
Normalized (+N): refined grain structure for improved machinability
Quenched and tempered (+QT): tensile strength from 800–1200 MPa (depending on diameter)
Mechanical properties as per EN 10084 or ASTM A29 / A322

mechanical properties & heat treatment of 20MnCr5 steel

Heat temperature	Start forging temperature	Finish forging temperature	Cooling method
1100 – 1150 °C	1050 – 1100 °C	≥ 850 °C	Pit, sand, or furnace cooling

Annealing

Annealing temperature: 650 – 700°C
Hold at temperature for sufficient time (minimum 2 hours, or 2 minutes per mm of section thickness)
Cool slowly in the furnace
Hardness after annealing: max. 217 – 248 HB
Annealing in a protective atmosphere is recommended to reduce decarburization and surface scaling

Hardening

20MnCr5 is a case-hardening (carburizing) steel. The carburizing process is critical to achieve the desired case hardness and core toughness combination. After carburizing and quenching, the surface hardness can reach approximately 58 – 62 HRC, depending on case depth and heat treatment conditions
Carburizing:
Carburizing temperature: 880 – 980°C.
Typical range: 900 – 950°C.
Alternative range: 870 – 950°C.
Carburizing takes place at a temperature of about 880 – 980°C
Carburizing time: Depends on required case depth (typically 0.5–1.0 mm but can be deeper)
Cooling from carburizing temperature: water, oil, air, thermal bath, or cooling box
Core Hardening:
Austenitizing temperature: 850 – 880°C.
Alternative: 860 – 900°C
Quenching media: Oil
Purpose: Achieve the required core tensile strength (1000 – 1300 N/mm²)
Case Hardening:
Austenitizing temperature: 780 – 820°C.
Alternative: 810 – 840°C
Quenching media: Oil or water

Stress relieving

Perform after rough machining, heavy stock removal, or welding to reduce residual stresses
Heat to 600 – 650°C
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 to avoid cracking
Tempering temperature: 150 – 200°C.
Alternative: 170 – 200°C
Holding time: 1 hour per 25mm of section thickness (minimum 2 hours)
Cooling method: Air cool after tempering
Purpose: Reduces stresses without affecting case hardness

Why Choose NSPM as Your 20MnCr5 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.