DIN 20MnCr5 1.7147 5120 Case Hardening Steel

Product Overview

DIN 20MnCr5 and ASTM 5120 are high-performance low-carbon alloy carburized steels, engineered to excel in components subjected to repeated mechanical stress, friction, and heavy loads. As core members of the Mn-Cr alloy steel series, these grades deliver a unique combination of a wear-resistant hard surface (up to 62HRC after carburization) and a ductile, impact-resistant core—eliminating brittle failure risks in high-demand industrial scenarios.

20MnCr5 1.7147 adheres to European EN standards, while ASTM 5120 is the American equivalent, with both matching China’s GB/T 3077 20CrMn for seamless cross-regional sourcing. Widely adopted in automotive manufacturing, heavy machinery, construction equipment, and aerospace auxiliary systems, these steels are the first choice for precision transmission parts, high-strength fasteners, and load-bearing shafts where durability and reliability are non-negotiable.

With a precisely calibrated carbon content of 0.17-0.22%, the steels optimize carburization response—ensuring carbon diffusion forms a dense, hard surface layer while preserving the core’s toughness. Versatile supply forms (hot-rolled bars, forged bars, forged blocks) and customizable finishes further make them adaptable to both small precision components and large industrial heavy-duty parts.

Steel Equivalent

Country	USA	Europe	China
Standard	ASTM A29	EN10084	GB/T3077
Grade	5120	20MnCr5/1.7147	20CrMn

Product Features

Chemical Composition

The performance of 20MnCr5 1.7147 and ASTM 5120 is rooted in their optimized alloy ratio, with strict impurity control to enhance material integrity and processing stability. The Chinese equivalent 20CrMn is also included for Asian market reference:

Grade	C	Si	Mn	P	S	Cr
5120	0.17-0.22	0.15-0.35	0.70-0.90	0.035Max	0.040Max	0.7-0.9
20MnCr5/1.7147	0.17-0.22	0.40Max	1.10-1.40	0.025Max	0.035Max	1.0-1.3
20CrMn	0.17-0.23	0.17-0.37	0.90-1.20	0.030Max	0.030Max	0.9-1.2

Composition Core Benefits

• Low carbon content: Prevents core brittleness during carburization, enabling the material to absorb impact without cracking.

• Manganese gradient: Higher Mn in 20MnCr5 1.7147 boosts hardenability for deeper hardness penetration in thick components; lower Mn in ASTM 5120 suits small parts with rapid cooling.

• Chromium addition: Enhances wear resistance and carburization uniformity, forming stable carbides on the surface.

• Strict impurity limits: Ultra-low P/S in 20MnCr5 1.7147 reduces microcrack risks, critical for safety-critical components.

Mechanical Properties

All mechanical properties are tested in compliance with EN 10084 (20MnCr5) and ISO 683-11-1987 (simulated case-hardening), with tensile strength calibrated by component diameter for practical application reference:

Minimum Tensile Strength (Hardened & Tempered at 200℃)

Size range	Tensile strength
d≤16	1200Mpa Min
16＜d≤40	800Mpa Min
40＜d≤100	600Mpa Min

Comprehensive Mechanical Metrics

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	1000-1350Mpa	670Mpa Min	8% Min	20J Min
d=30	900-1250Mpa	610Mpa Min	9% Min	20J Min
d=63	780-1130Mpa	540Mpa Min	10% Min	23J Min

Surface hardness

Heat Treatment	Hardness
Treated to improve shearability (+S)	HB255Max
Soft annealed (+A)	HB217Max
Treated to hardness range(+TH)	170-217HBW
Treated to ferrite-pearlite structure and hardness range(+FP)	152-201HBW
Normalized(+N)	140-201HBW

Hardenability Performance

20MnCr5 1.7147 offers customizable hardenability options (+H: normal, +HL: low restricted, +HH: high restricted) to match different component processing needs. The Rockwell C hardness at different distances from the quenched end is as follows (core for heat treatment process design):

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	49	48	46	43	42	41	39	37	35	34	33	32
	min	41	39	36	33	30	28	26	25	23	21	/	/	/
Hardness In HRC + HH	max	49	49	48	46	43	42	41	39	37	35	34	33	32
	min	44	42	40	37	34	33	31	30	28	26	25	24	23
Hardness In HRC + HL	max	46	46	44	42	39	37	36	34	32	30	29	28	27
	min	41	39	36	33	30	28	26	25	23	21	/	/	/

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

Key

X   distance from quenched end of test piece, mm

Y   hardness, HRC

1   upper limit

2   upper limit, +HL grades

3   lower limit, +HH grades

4   lower limit

Heat Treatment

Both 20MnCr5 1.7147 and ASTM 5120 feature excellent heat treatment flexibility, allowing manufacturers to tailor material performance to specific component functional requirements. All processes are optimized for minimal distortion and maximum performance retention:

• Soft Annealing: Heat to 650-700℃, furnace cooling → Hardness ≤217HB. Ideal for reducing material hardness for precision machining (e.g., gear hobbing, shaft turning).

• Normalization: Heat to 840-870℃, air cooling → Uniform ferrite-pearlite structure (140-201HB). Eliminates internal stress from forging/rolling, prepping for subsequent carburization.

• Carburization: 20MnCr5 1.7147 heated to 880-980℃ (time adjustable for case depth) → Surface hardness 58-62HRC. Perfect for wear-prone parts (gear teeth, sprocket surfaces) with customizable case depth (0.5-2.0mm).

• Quenching & Tempering: Heat to 830-840℃, oil quenching (minimal distortion) + 150-200℃ tempering → Relieves residual stress while preserving surface hardness, extending component lifespan by 30-50%.

• Optimal Gear Process: Carburization (920-950℃, 4-8h) → Oil quenching → 180-200℃ tempering (2h) → Balances wear resistance and impact toughness for gear teeth.

Supply Specifications & Finishes

Hunan Qilu Steel provides full-range supply of 20MnCr5 1.7147 and ASTM 5120, with 10,000+ tons monthly stock and customizable sizes/finishes to match diverse production workflows. Strict tolerance control ensures precision for both rough and fine processing.

Supply Sizes

Product type	Size range	Length
Hot rolled bar	Φ14-Φ280mm	6000-9000mm
Hot forged bar	Φ140-Φ1200mm	3000-5800mm
Hot Forged block	T: 80-800mm; W: 100-2500mm	2000-5800mm

Stock Hot-Rolled Bar Diameters (Common Sizes)

14, 16, 18, 20, 22, 25, 28, 30, 32, 35, 38, 40, 42, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, 250, 260, 270, 280mm

Surface Finishes & Precision

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.

Industrial Applications

The unique performance of 20MnCr5 1.7147 and ASTM 5120 makes them indispensable in high-stress, high-wear industrial scenarios. Different grades are selected based on component size, load, and safety requirements:

1. Automotive Drivetrain Systems

• Transmission Gears: Resists tooth wear after 100,000+ km driving with 58-62HRC surface hardness and ≥20J impact value.

• Drive Shafts: Half-shafts/propeller shafts leverage ≥800MPa tensile strength (d≤40mm) to withstand torsion forces.

• Clutch Components: Pressure plates/flywheels use ≥8% elongation to handle repeated engagement without warping.

2. Heavy Industrial Machinery

• Sprockets & Pulleys: 170-217HBW hardness (+TH grade) resists abrasive wear from chains/belts, reducing maintenance downtime.

• High-Strength Fasteners: Bolts/nuts for turbines/compressors use ≥540MPa yield strength (d=63mm) to stay secure under vibration.

• Worm Gears/Sleeves: Replaces 20CrNi steel for cost savings while meeting medium-load sliding friction requirements.

3. Construction Equipment

• Excavator Gears: Swing/travel gears with ≥23J impact value (d=63mm) withstand rock/debris collisions; excellent hardenability ensures uniform performance in thick sections.

• Loader Hydraulic Shafts: Handles sudden 10+ ton load changes without bending/cracking, adapting to harsh dusty construction environments.

4. Aerospace Auxiliary Systems

• APU Transmission Parts: High-temperature stability (up to 200℃ tempered) ensures reliable operation in engine bays.

• Landing Gear Linkages: Ground finish (+0/+0.05mm tolerance) delivers precision and strength for smooth landing operations (not for primary flight structures).

Grade Comparison & Selection Guide

1. DIN 20MnCr5 1.7147 vs ASTM 5120

Aspect	DIN 20MnCr5 1.7147	ASTM 5120
Hardenability	High (1.10-1.40% Mn) → Deep hardness penetration	Moderate (0.70-0.90% Mn) → Rapid cooling for small parts
Impurity Control	Strict (P≤0.025%, S≤0.035%)	Standard (P≤0.035%, S≤0.040%)
Ideal Components	Thick parts (d>40mm), safety-critical parts (brakes, heavy shafts)	Small parts (d≤16mm), non-critical components (brackets, small gears)
Cost & Value	Slightly higher cost, superior reliability	Cost-effective, balanced performance for general use

2. 20MnCr5 1.7147 vs 20CrMnTi (Common Alternative)

20CrMnTi is a widely used carburized steel; the comparison below helps with targeted selection:

Aspect	20MnCr5 1.7147	20CrMnTi
Alloy Element	Mn-Cr based, no Ti	Mn-Cr-Ti based, Ti refines grains
Hardenability	Higher, better for thick sections	Moderate, suitable for medium/small parts
Machinability	Excellent (low impurity)	Good, but Ti increases cutting resistance
Wear Resistance	Superior (dense Cr carbides)	Good (Ti carbides for grain refinement)
Cost	Moderate	Slightly lower
Application	Heavy-duty transmission parts, large shafts	Automotive small gears, precision fasteners

3. 20MnCr5 1.7147 vs 20Cr

20MnCr5 1.7147 outperforms 20Cr in all core aspects, making it the upgrade choice for high-demand applications:

• Hardenability: 20MnCr5 has 2-3x deeper hardness penetration than 20Cr, eliminating core softness in thick parts.

• Mechanical Properties: 30% higher tensile strength and 50% higher impact value after heat treatment.

• Wear Resistance: Carburized surface hardness 58-62HRC (20Cr: 50-55HRC), with longer service life.

• Application: 20Cr for low-load parts; 20MnCr5 for high-stress, high-wear components.

FAQ

Q1: How to choose between 20MnCr5 1.7147 and ASTM 5120 for my project?

A1: Select 20MnCr5 1.7147 for components with diameter >40mm, safety-critical parts (e.g., automotive brakes), or harsh working conditions (high vibration/impact). Choose ASTM 5120 for small parts (d≤16mm), non-critical components, or cost-sensitive projects—its performance fully meets general industrial requirements.

Q2: Is 20MnCr5 1.7147 interchangeable with China’s 20CrMn?

A2: Yes, 20CrMn (GB/T 3077) is the direct Chinese equivalent, with almost identical chemical composition and mechanical properties. The slight difference in element ranges has no impact on practical application, enabling seamless replacement in production.

Q3: Can I weld 20MnCr5 1.7147/ASTM 5120? What are the key steps?

A3: Both steels have limited weldability due to Mn/Cr content, but successful welding is achievable with strict process control:

• Preheat the steel to 150-250℃ to reduce HAZ (heat-affected zone) cracking (Cr forms hard microstructures in HAZ).

• Use low-hydrogen electrodes (e.g., E7018) to minimize hydrogen-induced cracking.

• Post-weld temper at 150-200℃ to relieve residual stress and restore toughness.

Note: Never weld carburized parts—heat will soften the hard surface layer; weld only in annealed/normalized states.

Q4: What causes carburization failure of 20MnCr5 1.7147 and how to avoid it?

A4: Common failures: uneven case depth, low surface hardness, core brittleness. Prevention measures:

• Control carburization temperature (880-980℃) and time (based on required case depth, 0.5-2.0mm).

• Ensure uniform furnace temperature (temperature difference ≤±5℃) to avoid local overcarburization/undercarburization.

• Use high-purity carburizing agent to prevent impurity contamination of the surface.

• Cool slowly after carburization to avoid core brittleness, then perform oil quenching/tempering.

Q5: How to improve the machining efficiency of 20MnCr5 1.7147?

A5: Perform soft annealing first (650-700℃ furnace cooling) to reduce hardness to ≤217HB, significantly improving cutting efficiency. For high-precision machining (e.g., gear cutting), use peeled/ground finishes to reduce tool wear.

Q6: Why choose 20MnCr5 1.7147/ASTM 5120 over generic case hardening alloys?

A6: These grades outperform generic alloys in three core aspects:

• Global Standard Compliance: EN 10084/ASTM A29/GB/T 3077 certification eliminates international sales barriers.

• Consistent Performance: Tight tolerances (C±0.02%, tensile strength±50MPa) ensure batch-to-batch uniformity, reducing production defects.

• Total Cost Savings: Although 10-15% higher upfront cost than generic steels, their 2-3x longer lifespan and lower maintenance needs cut total ownership costs by 20-25% over 5 years.

Inquire Now: All product specifications and performance data are in compliance with international standards; for special application scenarios, contact our technical team for customized solutions.