AISI 4130 25CrMo4 1.7218 SCM430 708M25 Alloy Steel

Product Overview

AISI 4130 and its international equivalents—DIN 25CrMo4 (1.7218), JIS SCM430, BS 708M25/708A25, and Chinese 25CrMo—are premium chromium-molybdenum (Cr-Mo) quenched and tempered alloy steels engineered for high-stress, high-temperature industrial environments. As a core member of the low-alloy structural steel family, this grade balances exceptional tensile strength, fracture toughness, fatigue resistance, and high-temperature stability—outperforming standard carbon steels in nearly all heavy-duty applications.

Formulated with a precisely calibrated carbon content (0.22-0.33%) and alloyed with chromium (0.8-1.2%) and molybdenum (0.15-0.30%), this steel undergoes quenching and tempering (QT) to transform its microstructure into a fine-tuned martensitic/bainitic matrix. This heat treatment unlocks its signature properties: superior hardenability, corrosion resistance, and retention of mechanical performance under cyclic stress and temperature fluctuations (up to 550°C).

Widely recognized across global manufacturing supply chains, this alloy steel is the material of choice for cross-border projects in automotive, oil & gas, aerospace, machinery manufacturing, and civil engineering—where reliability, compliance, and long-term durability are non-negotiable.

Steel Equivalent

Country	USA	Europe	China	British	Japan
Standard	ASTM A29	EN10083-3	GB/T3077	BS970	JIS G4105
Grade	4130	25CrMo4/1.7218	25CrMo	708M25/708A25	SCM430

Product Features

Key Chemical Composition

Tailored for regional manufacturing standards, the chemical makeup of these equivalent grades varies slightly to align with local production needs, while retaining core Cr-Mo alloying and performance:

Grade	C	Si	Mn	P	S	Cr	Mo
4130	0.28-0.33	0.15-0.35	0.40-0.60	0.035Max	0.040Max	0.80-1.10	0.15-0.25
25CrMo4/1.7218	0.22-0.29	0.40Max	0.60-0.90	0.025Max	0.035Max	0.90-1.20	0.15-0.30
25CrMo	0.22-0.29	0.17-0.37	0.60-0.90	0.030Max	0.030Max	0.90-1.20	0.15-0.30
SCM430	0.28-0.33	0.15-0.35	0.60-0.85	0.030Max	0.030Max	0.90-1.20	0.15-0.30

Mechanical Properties

Mechanical performance scales with product size (diameter/thickness) per EN 10083-3 (bars/plates) and EN 10250-3 (open die forgings). All values are minimum requirements unless noted as a range:

For Bars & Plates

Mechanical properties for 25CrMo4 quenching and tempering alloy steel according to EN10083-3.

Size range	Tensile strength	Yield strength	Alongation	Area of reduction	Impact value At RT/J
d≤16 t≤8	900-1100Mpa	700Mpa Min	12% Min	50% Min	/
16＜d≤40 8＜t≤20	800-950Mpa	600Mpa Min	14% Min	55%Min	50J Min
40＜d≤100 20＜t≤60	700-850Mpa	450Mpa Min	15% Min	60%Min	50J Min
100＜d≤160 60＜t≤100	650-800Mpa	400Mpa Min	16% Min	60%Min	45J Min

For Open Die Forgings

Mechanical properties for 25CrMo4 open die forgings steel according to EN10250-3.

Size range	Tensile strength	Yield strength	Alongation		Impact value at RT/J
			L	Tr	L	Tr
≤70d(longitudinal)	700Mpa Min	450Mpa Min	15% Min		50J Min
70＜d≤160	650Mpa Min	400Mpa Min	17% Min	13% Min	45J Min	27J Min
160＜d≤330	600Mpa Min	380Mpa Min	18% Min	14% Min	38J Min	22J Min

Remark: L= Longitudinal    Tr = Transverse

Hardenability & Surface Hardness Customization

This grade offers controllable hardenability and surface hardness, with heat treatment options tailored to application needs. It meets three hardenability grades: +H (normal), +HH (high), +HL (low) — ideal for large components requiring uniform hardness across thick sections.

Standard Heat Treatment Results

Heat Treatment	Hardness
Flame or Induction hardening	54-60HRC
Treated to improve shearability (+S)	HB255Max
Soft annealed (+A)	HB212Max
Quenched and tempred (+QT)	HRC28-32(Common Range)

End-Quench Hardenability (Key +HH Grade Metrics)

The high-hardenability (+HH) grade ensures uniform performance in thick sections:

• Minimum 47HRC at 1.5mm from the quenched end

• Minimum 22HRC at 50mm from the quenched end

Distance in mm from quenched end
Distance		1.5	3	5	7	9	11	13	15	20	25	30	35	40	45	50
Hardness In HRC + H	max	52	52	51	50	48	46	43	41	37	35	33	32	31	31	31
	min	44	43	40	37	34	32	29	27	23	21	20	/	/	/	/
Hardness In HRC + HH	max	52	52	51	50	48	46	43	41	37	35	33	32	31	31	31
	min	47	46	44	41	39	37	34	32	28	26	24	23	22	22	22
Hardness In HRC + HL	max	49	49	47	46	43	41	38	36	32	30	29	28	27	27	27
	min	44	43	40	37	34	32	29	27	23	21	20	/	/	/	/

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

Supply Specifications & Stock Sizes

We offer flexible sizing, strict tolerances, and multiple surface finishes to accommodate diverse manufacturing demands—with immediate stock availability for standard sizes and custom forging/rolling for special requirements. All products meet international dimensional and flatness standards.

Product Forms & Size Ranges

Product type	Size range	Length
Cold drawn bar	Φ3-Φ80mm	6000-9000mm
Hot rolled bar	Φ16-Φ310mm	6000-9000mm
Hot forged bar	Φ100-Φ1200mm	3000-5800mm
Hot rolled plate/sheet	T:3-200mm; W:1500-2500mm	2000-5800mm
Hot Forged block	T: 80-800mm; W: 100-2500mm	2000-5800mm

Surface Finish & Tolerances

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.

In-Stock Sizes (Immediate Delivery)

• Hot Rolled Bars: Φ14, 16, 18, 20, 22, 25, 28, 30, 32, 35, 38, 40, 45, 50, 55, 60, 70, 80, 90, 100, 120, 150, 200, 250, 280mm

• Cold Drawn Bars: Φ6, 8, 10, 12, 15, 20, 25, 30, 40, 50, 60, 70, 80mm

• Hot Rolled Plates: T5, 10, 15, 20, 30, 40, 50, 80, 100, 150, 200mm

Stock levels update daily—contact our team for real-time availability and custom sizing.

Industrial Applications

This alloy steel’s versatility makes it a staple in six core industries, where it outperforms carbon steels and other low-alloy grades in durability and performance:

1. Automotive & Transportation

Critical powertrain and chassis components for passenger, commercial, and heavy vehicles:

• Transmission gears/shafts: 54-60HRC surface hardness (induction hardened) resists wear/tooth fatigue.

• Connecting rods: ≥700MPa yield strength and ≥50J impact value handle combustion cycle stress.

• Steering knuckles: Chromium-enhanced corrosion resistance for road salt/debris exposure.

2. Oil & Gas (Onshore/Offshore)

High-pressure, corrosive environments (up to 10,000 psi downhole pressure):

• Drill pipes/casing: 700-850MPa tensile strength and 500°C temperature stability prevent collapse.

• Wellhead components: Corrosion resistance to sour gas (H₂S) and brine; 28-32HRC hardness for leak-tight seals.

• Offshore platforms: Fatigue resistance to cyclic wave loads (10+ year component lifespan).

3. Aerospace & Defense

Lightweight, high-strength components (AS9100 compliant for aerospace grade):

• Landing gear parts: 900-1100MPa tensile strength and high strength-to-weight ratio for takeoff/landing loads.

• Engine mounts: 550°C high-temperature resistance and jet fuel corrosion protection.

• UAV frames: Precision cold-drawn bars (Φ3-80mm, +0/+0.05mm tolerance) for agility and durability.

4. Mechanical Manufacturing

Heavy-duty machinery for construction, mining, and industrial processing:

• High-strength fasteners: ≥600MPa yield strength prevents loosening under vibration.

• Gearboxes/reducers: ≥55% reduction of area prevents shear failure during torque transfer.

• Crushers/extruders: 54-60HRC surface hardness extends component life by 30% vs. carbon steel.

5. Construction & Bridge Engineering

Infrastructure projects requiring long-term structural stability:

• Prestressing bars: 700MPa+ tensile strength reduces concrete cracking in bridges/buildings.

• High-strength fasteners: 600MPa+ yield strength resists wind/seismic loads; corrosion resistance to rain/humidity.

• Crane rails: Induction-hardened 54-60HRC withstands 500-ton crane loads without wear.

6. Power Generation

Turbine and boiler components for thermal/hydroelectric power plants:

• Turbine shafts: High-temperature stability (up to 550°C) and fatigue resistance to rotational stress.

• Boiler support brackets: Corrosion resistance to steam and thermal cycling.

Key Grade Comparisons & Differences

1. AISI 4130 vs. DIN 25CrMo4 1.7218

While interchangeable for most applications (with minor heat treatment adjustments), the two grades differ in chemical composition and performance focus:

Aspect	AISI 4130	DIN 25CrMo4 1.7218
Carbon Content	0.28-0.33% (higher)	0.22-0.29% (lower)
Manganese Content	0.40-0.60% (lower)	0.60-0.90% (higher)
Phosphorus Limit	≤0.035%	≤0.025% (stricter)
Core Strength	Higher tensile strength	Higher purity/corrosion resistance
Ideal For	High-strength aerospace/automotive	Corrosion-prone oil/gas/marine

2. JIS SCM430 vs. BS 708M25

Nearly identical in mechanical performance—minor chemical differences do not impact real-world use:

• SCM430: Slightly higher C (0.28-0.33%) and lower Mn (0.60-0.85%) → marginally higher tensile strength (900-1100MPa for ≤16mm).

• 708M25: Lower C (0.22-0.29%) and full Mn range (0.60-0.90%) → preferred for European/UK manufacturing.

Interchangeable—SCM430 for Asian (Japanese) projects, 708M25 for European/UK projects.

3. AISI 4130 vs. AISI 4140

AISI 4140 is a higher-alloy Cr-Mo steel—key differences for selection:

Aspect	AISI 4130	AISI 4140
Carbon Content	0.28-0.33%	0.38-0.43% (higher)
Molybdenum Content	0.15-0.25%	0.15-0.25%
Hardness	28-32HRC (QT)	30-35HRC (QT) (harder)
Weldability	Moderate (easier)	Lower (more preheat)
Weight-to-Strength	Superior (lighter)	Lower (heavier)
Ideal For	Lightweight high-strength (aerospace/UAV)	Ultra-high strength (heavy machinery/tooling)

4. DIN 25CrMo4 vs. DIN 42CrMo4

42CrMo4 is a high-strength Cr-Mo steel for extreme loads:

• 25CrMo4: Lower C (0.22-0.29%) → better weldability and toughness → general industrial use.

• 42CrMo4: Higher C (0.38-0.45%) → ultra-high tensile strength (1100-1300MPa) → heavy forgings/axles.

FAQ

Q1: What is the main difference between AISI 4130 and 4140 steel?

A1: The primary difference lies in carbon content. 4130 has a lower carbon range (0.28-0.33%) compared to 4140 (0.38-0.43%). This gives 4130 superior weldability and ductility, making it a better choice for parts that require fabrication after heat treatment. 4140 offers higher potential hardness and strength but is less weldable.

Q2: Is DIN 25CrMo4 suitable for high-temperature service?

A2: Yes. Due to its molybdenum content, 25CrMo4 (1.7218) retains good strength at elevated temperatures and is often used for components operating up to 500°C (932°F) , such as pressure vessels, boiler parts, and turbine components.

Q3: Is AISI 4130/DIN 25CrMo4 weldable?

A3: Moderately weldable—not as easy as low-carbon steels, but manageable with proper pre/post-weld preparation (critical to avoid cracking/HAZ embrittlement):

• Preheat base metal to 200-300°C for thicknesses >12mm (reduces thermal stress).

• Use low-hydrogen electrodes (E8018-B2 for 4130) or GMAW with ER80S-B2 filler metal (minimizes hydrogen-induced cracking).

• Perform post-weld heat treatment (PWHT) at 580-620°C (softens HAZ and restores toughness).

• For critical applications (aerospace/oil & gas), conduct ultrasonic testing (UT) to verify weld integrity.

Q4: Are these grades corrosion-resistant?

A4: Yes—chromium alloying (0.8-1.2%) provides moderate corrosion resistance to atmospheric moisture, rain, road salt, and mild sour gas (H₂S). For highly corrosive environments (seawater/strong acids), we recommend surface coating (galvanization/powder coating) or upgrading to stainless steel.

Contact Us for real-time stock availability, custom quotes, or technical consultation—we deliver global-grade alloy steel to your doorstep, with flexible shipping options for all industries.