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25CrMo4 / 1.7218 is an alloy steel that belongs to the European standards EN 10083-3 and EN 10250-3. It is utilized in various industries, including automotive, machinery manufacturing, oil and gas, and construction, due to its excellent mechanical properties. As a result, you can find its equivalent steel grades in different country standards, such as ASTM 4130 from the American standard ASTM A29/A29M, SCM430 from the Japanese standard JIS G4105, 25CrMo from the Chinese standard GB/T 3077, and 708M25/708A25 from the British standard BS 970.
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AISI 4130 / DIN 25CrMo4 (1.7218) / JIS SCM430 / BS 708M25 is a family of high-performance quenching and tempering alloy steel designed for demanding industrial applications that require a balance of strength, toughness, and fatigue resistance. This alloy steel series complies with multiple international standards, including ASTM A29 (USA), EN 10083-3 / EN 10250-3 (Europe), GB/T 3077 (China), BS 970 (UK), and JIS G4105 (Japan), making it a globally recognized material for cross-border manufacturing projects.
At its core, this alloy belongs to the Cr-Mo steel category—a group valued for its ability to retain mechanical properties under high stress and temperature fluctuations. The carbon content of this steel range (0.22-0.33%) is carefully calibrated to work with the quenching and tempering (QT) heat treatment process, which transforms the material’s microstructure to deliver exceptional comprehensive performance. Unlike standard carbon steels, AISI 4130 / DIN 25CrMo4 benefits from the addition of chromium (0.8-1.2%) and molybdenum (0.15-0.30%), which enhance hardenability, corrosion resistance, and high-temperature stability.
This versatility has made it a staple in industries ranging from automotive and machinery manufacturing to oil and gas exploration and aerospace. Whether used for critical load-bearing components like shafts and gears or high-pressure equipment such as drill pipes, JIS SCM430 / BS 708M25 consistently meets strict performance criteria, making it a preferred choice for engineers and procurement teams seeking reliable, standards-aligned alloy steel.
The chemical makeup of AISI 4130 / DIN 25CrMo4 (1.7218) / JIS SCM430 / BS 708M25 is optimized to support its quenching and tempering capabilities, with slight variations across regional standards to align with local manufacturing needs. Key components (by weight percentage) include:
AISI 4130: Carbon (C: 0.28-0.33%), Silicon (Si: 0.15-0.35%), Manganese (Mn: 0.40-0.60%), Chromium (Cr: 0.8-1.1%), Molybdenum (Mo: 0.15-0.25%), Phosphorus (P: ≤0.035%), Sulfur (S: ≤0.040%).
DIN 25CrMo4 (1.7218): Carbon (C: 0.22-0.29%), Silicon (Si: ≤0.40%), Manganese (Mn: 0.60-0.90%), Chromium (Cr: 0.9-1.2%), Molybdenum (Mo: 0.15-0.30%), Phosphorus (P: ≤0.025%), Sulfur (S: ≤0.035%).
JIS SCM430: Carbon (C: 0.28-0.33%), Silicon (Si: 0.15-0.35%), Manganese (Mn: 0.60-0.85%), Chromium (Cr: 0.9-1.2%), Molybdenum (Mo: 0.15-0.30%), Phosphorus (P: ≤0.030%), Sulfur (S: ≤0.030%).
BS 708M25: Carbon (C: 0.22-0.29%), Silicon (Si: 0.15-0.35%), Manganese (Mn: 0.60-0.90%), Chromium (Cr: 0.9-1.2%), Molybdenum (Mo: 0.15-0.30%), Phosphorus (P: ≤0.030%), Sulfur (S: ≤0.030%).
These elements work synergistically: carbon boosts hardness, chromium improves wear resistance, and molybdenum enhances high-temperature strength—all critical for the alloy’s performance in harsh environments.
After quenching and tempering, AISI 4130 / DIN 25CrMo4 exhibits mechanical properties that exceed those of most carbon steels, with performance varying slightly by product size (per EN 10083-3 and EN 10250-3 standards):
For DIN 25CrMo4 (1.7218) bars/plates:
Size ≤16mm (diameter) / ≤8mm (thickness): Tensile strength (900-1100MPa), Yield strength (≥700MPa), Elongation (≥12%), Reduction of area (≥50%).
Size 16-40mm / 8-20mm: Tensile strength (800-950MPa), Yield strength (≥600MPa), Elongation (≥14%), Reduction of area (≥55%), Impact value (≥50J at room temperature).
Size 40-100mm / 20-60mm: Tensile strength (700-850MPa), Yield strength (≥450MPa), Elongation (≥15%), Reduction of area (≥60%), Impact value (≥50J at room temperature).
For DIN 25CrMo4 open die forgings:
Size ≤70mm (longitudinal): Tensile strength (≥700MPa), Yield strength (≥450MPa), Elongation (≥15%), Impact value (≥50J at room temperature).
Size 70-160mm: Tensile strength (≥650MPa), Yield strength (≥400MPa), Elongation (≥17% for longitudinal / ≥13% for transverse), Impact value (≥45J for longitudinal / ≥27J for transverse at room temperature).
These properties ensure the steel can withstand heavy loads, repeated stress, and temperature changes without deformation or failure.
AISI 4130 / DIN 25CrMo4 offers excellent hardenability, allowing manufacturers to adjust surface hardness based on application requirements. Common heat treatment results include:
Flame or Induction Hardening: Achieves a surface hardness of 54-60HRC—ideal for components needing wear resistance, such as gears and shafts.
Shearability Enhancement (+S): Limits maximum hardness to HB255 for easier machining and forming.
Soft Annealing (+A): Reduces hardness to HB212 max, simplifying cold working processes like bending or cutting.
Quenched and Tempered (+QT): The most common treatment, delivering a hardness range of 28-32HRC—a balance of strength and machinability for general industrial use.
For applications requiring controlled hardenability (e.g., large components), the steel meets +H (normal), +HH (high), and +HL (low) hardenability grades. In end-quench tests, +HH grade maintains a minimum hardness of 47HRC at 1.5mm from the quenched end and 22HRC at 50mm, ensuring uniform performance across thick sections.
To accommodate varied manufacturing demands, JIS SCM430 / BS 708M25 is available in multiple product forms with strict size tolerances:
Cold Drawn Bars: Diameter range Φ3-Φ80mm, length 6000-9000mm, surface finish options (turned, ground, polished) with a tolerance of +0/+0.05mm (ground/polished) for precision applications.
Hot Rolled Bars: Diameter range Φ16-Φ310mm, length 6000-9000mm, surface finish (black rolled or peeled) with a tolerance of +0/+1mm (black rolled) or +0/+0.1mm (peeled).
Hot Forged Bars: Diameter range Φ100-Φ1200mm, length 3000-5800mm, surface finish (black forged) with a tolerance of +0/+5mm—suitable for large, heavy-duty components like machinery frames.
Hot Rolled Plates/Sheets: Thickness 3-200mm, width 1500-2500mm, length 2000-5800mm, with a flatness tolerance of 1mm/1000mm (milled/ground) or 3mm/1000mm (black rolled).
Common stock sizes for hot rolled bars include 14mm, 16mm, 18mm, 20mm, 25mm, 30mm, 40mm, 50mm, 80mm, 100mm, 150mm, 200mm, and 250mm—with daily stock updates available upon request.
In automotive manufacturing, AISI 4130 / DIN 25CrMo4 is used for high-stress components that require durability and reliability. Key applications include:
Gears and Shafts: The steel’s 900-1100MPa tensile strength and 54-60HRC surface hardness (after induction hardening) resist wear and tooth fatigue in transmission gears and drive shafts.
Connecting Rods: Its balance of strength (≥700MPa yield strength) and toughness (≥50J impact value) handles the repeated stress of engine combustion cycles.
Steering Knuckles: The alloy’s corrosion resistance (from chromium) and impact resistance make it suitable for undercarriage components exposed to road salts and debris.
Major automakers rely on this steel to meet strict safety standards, as it minimizes the risk of component failure in high-speed or heavy-load conditions.
The oil and gas industry demands materials that withstand high pressure, corrosive fluids, and extreme temperatures—requirements JIS SCM430 / BS 708M25 fulfills:
Drill Pipes and Casing: The steel’s 700-850MPa tensile strength (for 40-100mm sizes) and molybdenum-enhanced high-temperature stability (up to 500°C) resist collapse under downhole pressure (up to 10,000 psi).
Wellhead Components: Its corrosion resistance (from chromium) protects against sour gas (H₂S) and brine, while its 28-32HRC hardness (QT treatment) ensures leak-tight seals in valves and flanges.
Offshore Platform Structures: The alloy’s fatigue resistance (from QT processing) withstands cyclic wave loads, making it ideal for structural supports and risers.
In offshore and onshore projects, this steel reduces maintenance costs by extending component lifespans to 10+ years.
For industrial machinery (e.g., construction equipment, mining machinery), AISI 4130 / DIN 25CrMo4 is a top choice for components needing to handle heavy loads:
High-Strength Bolts and Nuts: With a yield strength of ≥600MPa (16-40mm sizes), the steel secures large machinery frames and rotating parts without loosening under vibration.
Transmission Components: Gearboxes and reducers use this steel for shafts and bearings, as its 55%+ reduction of area (16-40mm sizes) prevents shear failure during torque transfer.
Crushers and Extruders: The steel’s 54-60HRC surface hardness (induction hardened) resists abrasion from rocks, plastics, or metals, extending component life by 30% compared to carbon steel.
Manufacturers appreciate its machinability (HB255 max for +S treatment), which reduces production time for complex parts.
In aerospace, where weight and strength are critical, AISI 4130 is a preferred material for:
Landing Gear Parts: Its high strength-to-weight ratio (900-1100MPa tensile strength at low weight) supports aircraft loads during takeoff and landing, while its 45J impact value (100-160mm sizes) handles rough landings.
Engine Mounts: The alloy’s molybdenum-enhanced high-temperature resistance (up to 550°C) withstands engine heat, while its corrosion resistance protects against jet fuel and atmospheric moisture.
UAV Frames: Cold-drawn AISI 4130 bars (Φ3-Φ80mm) offer precision (tolerance +0/+0.05mm) and lightweight design, making them ideal for unmanned aerial vehicles requiring agility and durability.
Aerospace-grade AISI 4130 meets AS9100 standards, ensuring compliance with strict quality controls.
For infrastructure projects, BS 708M25 / DIN 25CrMo4 provides the strength needed for long-lasting structures:
Prestressing Steel Bars: The steel’s 700MPa+ tensile strength allows it to apply preload to concrete bridges and buildings, reducing cracking and extending structural life.
High-Strength Fasteners: Used in steel frame buildings and bridges, its 600MPa+ yield strength resists wind and seismic loads, while its corrosion resistance (chromium) protects against rain and humidity.
Crane Rails: Induction-hardened BS 708M25 (54-60HRC) withstands the weight of heavy cranes (up to 500 tons) without wear, reducing rail replacement frequency.
While both are quenching and tempering Cr-Mo alloy steels, the key differences lie in chemical composition and mechanical properties. AISI 4130 has a higher carbon content (0.28-0.33% vs. 0.22-0.29% for DIN 25CrMo4) and lower manganese (0.40-0.60% vs. 0.60-0.90%), resulting in higher tensile strength (900-1100MPa for ≤16mm sizes vs. the same range for DIN 25CrMo4). DIN 25CrMo4, however, offers stricter phosphorus limits (≤0.025% vs. ≤0.035% for AISI 4130), improving purity and corrosion resistance. For most applications, they are interchangeable with minor heat treatment adjustments, but AISI 4130 is preferred for high-strength needs, while DIN 25CrMo4 excels in corrosion-prone environments.
The alloy is compatible with four primary heat treatment processes, each tailored to application needs:
Quenching and Tempering (QT): Heat to 840-900°C, soak, quench in water/oil, then temper at 540-680°C. Delivers 28-32HRC hardness and balanced strength/toughness—ideal for general use.
Flame/Induction Hardening: Localized heating to 850-950°C, quench rapidly. Creates a hard surface (54-60HRC) with a tough core—used for gears and shafts.
Soft Annealing: Heat to 650-700°C, soak, cool in furnace/air. Reduces hardness to HB212 max—simplifies cold working.
Normalization: Heat to 860-900°C, soak, cool in air. Refines grain structure and stabilizes dimensions—preferred for large forgings before machining.
Always follow EN 10083-1 (bars) or EN 10250-1 (forgings) guidelines for heat treatment parameters to avoid brittleness.
AISI 4130 / DIN 25CrMo4 has moderate weldability—not as easy to weld as low-carbon steels, but manageable with proper preparation. Its weldability is influenced by carbon content (0.22-0.33%) and alloying elements (chromium, molybdenum), which increase the risk of weld cracking and heat-affected zone (HAZ) embrittlement. To ensure strong welds:
Preheat the base metal to 200-300°C (for thicknesses >12mm) to reduce thermal stress.
Use low-hydrogen electrodes (e.g., E8018-B2 for AISI 4130) or gas metal arc welding (GMAW) with ER80S-B2 filler metal to minimize hydrogen-induced cracking.
Perform post-weld heat treatment (PWHT) at 580-620°C to soften the HAZ and restore toughness.
For critical applications (e.g., aerospace), ultrasonic testing (UT) is recommended to verify weld integrity.
Hunan Qilu Steel maintains large inventories of AISI 4130 / DIN 25CrMo4 / JIS SCM430 / BS 708M25 to support quick turnaround times. Common in-stock sizes include:
Hot Rolled Bars: Diameters 14mm, 16mm, 18mm, 20mm, 22mm, 25mm, 28mm, 30mm, 32mm, 35mm, 38mm, 40mm, 45mm, 50mm, 55mm, 60mm, 70mm, 80mm, 90mm, 100mm, 120mm, 150mm, 200mm, 250mm, and 280mm (length 6000-9000mm).
Cold Drawn Bars: Diameters 6mm, 8mm, 10mm, 12mm, 15mm, 20mm, 25mm, 30mm, 40mm, 50mm, 60mm, 70mm, and 80mm (length 6000-9000mm, ground finish).
Hot Rolled Plates: Thicknesses 5mm, 10mm, 15mm, 20mm, 30mm, 40mm, 50mm, 80mm, 100mm, 150mm, and 200mm (width 1500-2500mm, length 2000-5800mm).
Stock levels change daily, so contact our team with your specific size requirements for real-time availability.
JIS SCM430 and BS 708M25 are nearly identical in mechanical performance, with minor differences in chemical composition that do not impact most applications. JIS SCM430 has a slightly higher carbon content (0.28-0.33% vs. 0.22-0.29% for BS 708M25) and lower manganese (0.60-0.85% vs. 0.60-0.90%), leading to a marginally higher tensile strength (900-1100MPa for ≤16mm sizes vs. 800-950MPa for BS 708M25 in the same size range). Both alloys offer identical yield strength (≥600MPa for 16-40mm sizes), elongation (≥14%), and impact value (≥50J at room temperature).
For practical purposes, they are interchangeable. JIS SCM430 is more commonly used in Asian manufacturing (e.g., Japanese automotive), while BS 708M25 is preferred in European and UK projects. Both meet the same quenching and tempering standards, ensuring consistent performance across global supply chains.
1: 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 |
2: Chemical composition
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 | 0.8-1.1 | 0.15-0.25 |
25CrMo4/1.7218 | 0.22-0.29 | 0.40Max | 0.60-0.90 | 0.025Max | 0.035Max | 0.9-1.2 | 0.15-0.30 |
25CrMo | 0.22-0.29 | 0.17-0.37 | 0.60-0.90 | 0.030Max | 0.030Max | 0.9-1.2 | 0.15-0.30 |
SCM430 | 0.28-0.33 | 0.15-0.35 | 0.60-0.85 | 0.030Max | 0.030Max | 0.9-1.2 | 0.15-0.30 |
3: Mechanical properties .
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 |
Sampling and preparation of test pieces for 25CrMo4 quenching and tempering steel.
1): According to EN10083-1, all samples shall be taken at a distance of 12.5mm below the heat treated surface
2): As stipulated in the contract between buyer and seller.
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
Sampling and preparation of test pieces for steel forging.
1: According to EN10250-1, all samples shall be taken at a distance of 4/T below the heat treated surface (with a minimum of 20mm and a maximum of 80mm), and t/2 from the end (where t is the equivalent thickness of the thickness of the ruling section of the forging at the time of heat treatment.
2: As stipulated in the contract between buyer and seller.
4: Surface hardness and hardenability.
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) |
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 | 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.
5: Supply size & Tolerance & Stock size
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 | 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
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 | 280 |
Since the stocks change everyday, if you want to know our stock available information, please contact our salesman.
AISI 4130 / DIN 25CrMo4 (1.7218) / JIS SCM430 / BS 708M25 is a family of high-performance quenching and tempering alloy steel designed for demanding industrial applications that require a balance of strength, toughness, and fatigue resistance. This alloy steel series complies with multiple international standards, including ASTM A29 (USA), EN 10083-3 / EN 10250-3 (Europe), GB/T 3077 (China), BS 970 (UK), and JIS G4105 (Japan), making it a globally recognized material for cross-border manufacturing projects.
At its core, this alloy belongs to the Cr-Mo steel category—a group valued for its ability to retain mechanical properties under high stress and temperature fluctuations. The carbon content of this steel range (0.22-0.33%) is carefully calibrated to work with the quenching and tempering (QT) heat treatment process, which transforms the material’s microstructure to deliver exceptional comprehensive performance. Unlike standard carbon steels, AISI 4130 / DIN 25CrMo4 benefits from the addition of chromium (0.8-1.2%) and molybdenum (0.15-0.30%), which enhance hardenability, corrosion resistance, and high-temperature stability.
This versatility has made it a staple in industries ranging from automotive and machinery manufacturing to oil and gas exploration and aerospace. Whether used for critical load-bearing components like shafts and gears or high-pressure equipment such as drill pipes, JIS SCM430 / BS 708M25 consistently meets strict performance criteria, making it a preferred choice for engineers and procurement teams seeking reliable, standards-aligned alloy steel.
The chemical makeup of AISI 4130 / DIN 25CrMo4 (1.7218) / JIS SCM430 / BS 708M25 is optimized to support its quenching and tempering capabilities, with slight variations across regional standards to align with local manufacturing needs. Key components (by weight percentage) include:
AISI 4130: Carbon (C: 0.28-0.33%), Silicon (Si: 0.15-0.35%), Manganese (Mn: 0.40-0.60%), Chromium (Cr: 0.8-1.1%), Molybdenum (Mo: 0.15-0.25%), Phosphorus (P: ≤0.035%), Sulfur (S: ≤0.040%).
DIN 25CrMo4 (1.7218): Carbon (C: 0.22-0.29%), Silicon (Si: ≤0.40%), Manganese (Mn: 0.60-0.90%), Chromium (Cr: 0.9-1.2%), Molybdenum (Mo: 0.15-0.30%), Phosphorus (P: ≤0.025%), Sulfur (S: ≤0.035%).
JIS SCM430: Carbon (C: 0.28-0.33%), Silicon (Si: 0.15-0.35%), Manganese (Mn: 0.60-0.85%), Chromium (Cr: 0.9-1.2%), Molybdenum (Mo: 0.15-0.30%), Phosphorus (P: ≤0.030%), Sulfur (S: ≤0.030%).
BS 708M25: Carbon (C: 0.22-0.29%), Silicon (Si: 0.15-0.35%), Manganese (Mn: 0.60-0.90%), Chromium (Cr: 0.9-1.2%), Molybdenum (Mo: 0.15-0.30%), Phosphorus (P: ≤0.030%), Sulfur (S: ≤0.030%).
These elements work synergistically: carbon boosts hardness, chromium improves wear resistance, and molybdenum enhances high-temperature strength—all critical for the alloy’s performance in harsh environments.
After quenching and tempering, AISI 4130 / DIN 25CrMo4 exhibits mechanical properties that exceed those of most carbon steels, with performance varying slightly by product size (per EN 10083-3 and EN 10250-3 standards):
For DIN 25CrMo4 (1.7218) bars/plates:
Size ≤16mm (diameter) / ≤8mm (thickness): Tensile strength (900-1100MPa), Yield strength (≥700MPa), Elongation (≥12%), Reduction of area (≥50%).
Size 16-40mm / 8-20mm: Tensile strength (800-950MPa), Yield strength (≥600MPa), Elongation (≥14%), Reduction of area (≥55%), Impact value (≥50J at room temperature).
Size 40-100mm / 20-60mm: Tensile strength (700-850MPa), Yield strength (≥450MPa), Elongation (≥15%), Reduction of area (≥60%), Impact value (≥50J at room temperature).
For DIN 25CrMo4 open die forgings:
Size ≤70mm (longitudinal): Tensile strength (≥700MPa), Yield strength (≥450MPa), Elongation (≥15%), Impact value (≥50J at room temperature).
Size 70-160mm: Tensile strength (≥650MPa), Yield strength (≥400MPa), Elongation (≥17% for longitudinal / ≥13% for transverse), Impact value (≥45J for longitudinal / ≥27J for transverse at room temperature).
These properties ensure the steel can withstand heavy loads, repeated stress, and temperature changes without deformation or failure.
AISI 4130 / DIN 25CrMo4 offers excellent hardenability, allowing manufacturers to adjust surface hardness based on application requirements. Common heat treatment results include:
Flame or Induction Hardening: Achieves a surface hardness of 54-60HRC—ideal for components needing wear resistance, such as gears and shafts.
Shearability Enhancement (+S): Limits maximum hardness to HB255 for easier machining and forming.
Soft Annealing (+A): Reduces hardness to HB212 max, simplifying cold working processes like bending or cutting.
Quenched and Tempered (+QT): The most common treatment, delivering a hardness range of 28-32HRC—a balance of strength and machinability for general industrial use.
For applications requiring controlled hardenability (e.g., large components), the steel meets +H (normal), +HH (high), and +HL (low) hardenability grades. In end-quench tests, +HH grade maintains a minimum hardness of 47HRC at 1.5mm from the quenched end and 22HRC at 50mm, ensuring uniform performance across thick sections.
To accommodate varied manufacturing demands, JIS SCM430 / BS 708M25 is available in multiple product forms with strict size tolerances:
Cold Drawn Bars: Diameter range Φ3-Φ80mm, length 6000-9000mm, surface finish options (turned, ground, polished) with a tolerance of +0/+0.05mm (ground/polished) for precision applications.
Hot Rolled Bars: Diameter range Φ16-Φ310mm, length 6000-9000mm, surface finish (black rolled or peeled) with a tolerance of +0/+1mm (black rolled) or +0/+0.1mm (peeled).
Hot Forged Bars: Diameter range Φ100-Φ1200mm, length 3000-5800mm, surface finish (black forged) with a tolerance of +0/+5mm—suitable for large, heavy-duty components like machinery frames.
Hot Rolled Plates/Sheets: Thickness 3-200mm, width 1500-2500mm, length 2000-5800mm, with a flatness tolerance of 1mm/1000mm (milled/ground) or 3mm/1000mm (black rolled).
Common stock sizes for hot rolled bars include 14mm, 16mm, 18mm, 20mm, 25mm, 30mm, 40mm, 50mm, 80mm, 100mm, 150mm, 200mm, and 250mm—with daily stock updates available upon request.
In automotive manufacturing, AISI 4130 / DIN 25CrMo4 is used for high-stress components that require durability and reliability. Key applications include:
Gears and Shafts: The steel’s 900-1100MPa tensile strength and 54-60HRC surface hardness (after induction hardening) resist wear and tooth fatigue in transmission gears and drive shafts.
Connecting Rods: Its balance of strength (≥700MPa yield strength) and toughness (≥50J impact value) handles the repeated stress of engine combustion cycles.
Steering Knuckles: The alloy’s corrosion resistance (from chromium) and impact resistance make it suitable for undercarriage components exposed to road salts and debris.
Major automakers rely on this steel to meet strict safety standards, as it minimizes the risk of component failure in high-speed or heavy-load conditions.
The oil and gas industry demands materials that withstand high pressure, corrosive fluids, and extreme temperatures—requirements JIS SCM430 / BS 708M25 fulfills:
Drill Pipes and Casing: The steel’s 700-850MPa tensile strength (for 40-100mm sizes) and molybdenum-enhanced high-temperature stability (up to 500°C) resist collapse under downhole pressure (up to 10,000 psi).
Wellhead Components: Its corrosion resistance (from chromium) protects against sour gas (H₂S) and brine, while its 28-32HRC hardness (QT treatment) ensures leak-tight seals in valves and flanges.
Offshore Platform Structures: The alloy’s fatigue resistance (from QT processing) withstands cyclic wave loads, making it ideal for structural supports and risers.
In offshore and onshore projects, this steel reduces maintenance costs by extending component lifespans to 10+ years.
For industrial machinery (e.g., construction equipment, mining machinery), AISI 4130 / DIN 25CrMo4 is a top choice for components needing to handle heavy loads:
High-Strength Bolts and Nuts: With a yield strength of ≥600MPa (16-40mm sizes), the steel secures large machinery frames and rotating parts without loosening under vibration.
Transmission Components: Gearboxes and reducers use this steel for shafts and bearings, as its 55%+ reduction of area (16-40mm sizes) prevents shear failure during torque transfer.
Crushers and Extruders: The steel’s 54-60HRC surface hardness (induction hardened) resists abrasion from rocks, plastics, or metals, extending component life by 30% compared to carbon steel.
Manufacturers appreciate its machinability (HB255 max for +S treatment), which reduces production time for complex parts.
In aerospace, where weight and strength are critical, AISI 4130 is a preferred material for:
Landing Gear Parts: Its high strength-to-weight ratio (900-1100MPa tensile strength at low weight) supports aircraft loads during takeoff and landing, while its 45J impact value (100-160mm sizes) handles rough landings.
Engine Mounts: The alloy’s molybdenum-enhanced high-temperature resistance (up to 550°C) withstands engine heat, while its corrosion resistance protects against jet fuel and atmospheric moisture.
UAV Frames: Cold-drawn AISI 4130 bars (Φ3-Φ80mm) offer precision (tolerance +0/+0.05mm) and lightweight design, making them ideal for unmanned aerial vehicles requiring agility and durability.
Aerospace-grade AISI 4130 meets AS9100 standards, ensuring compliance with strict quality controls.
For infrastructure projects, BS 708M25 / DIN 25CrMo4 provides the strength needed for long-lasting structures:
Prestressing Steel Bars: The steel’s 700MPa+ tensile strength allows it to apply preload to concrete bridges and buildings, reducing cracking and extending structural life.
High-Strength Fasteners: Used in steel frame buildings and bridges, its 600MPa+ yield strength resists wind and seismic loads, while its corrosion resistance (chromium) protects against rain and humidity.
Crane Rails: Induction-hardened BS 708M25 (54-60HRC) withstands the weight of heavy cranes (up to 500 tons) without wear, reducing rail replacement frequency.
While both are quenching and tempering Cr-Mo alloy steels, the key differences lie in chemical composition and mechanical properties. AISI 4130 has a higher carbon content (0.28-0.33% vs. 0.22-0.29% for DIN 25CrMo4) and lower manganese (0.40-0.60% vs. 0.60-0.90%), resulting in higher tensile strength (900-1100MPa for ≤16mm sizes vs. the same range for DIN 25CrMo4). DIN 25CrMo4, however, offers stricter phosphorus limits (≤0.025% vs. ≤0.035% for AISI 4130), improving purity and corrosion resistance. For most applications, they are interchangeable with minor heat treatment adjustments, but AISI 4130 is preferred for high-strength needs, while DIN 25CrMo4 excels in corrosion-prone environments.
The alloy is compatible with four primary heat treatment processes, each tailored to application needs:
Quenching and Tempering (QT): Heat to 840-900°C, soak, quench in water/oil, then temper at 540-680°C. Delivers 28-32HRC hardness and balanced strength/toughness—ideal for general use.
Flame/Induction Hardening: Localized heating to 850-950°C, quench rapidly. Creates a hard surface (54-60HRC) with a tough core—used for gears and shafts.
Soft Annealing: Heat to 650-700°C, soak, cool in furnace/air. Reduces hardness to HB212 max—simplifies cold working.
Normalization: Heat to 860-900°C, soak, cool in air. Refines grain structure and stabilizes dimensions—preferred for large forgings before machining.
Always follow EN 10083-1 (bars) or EN 10250-1 (forgings) guidelines for heat treatment parameters to avoid brittleness.
AISI 4130 / DIN 25CrMo4 has moderate weldability—not as easy to weld as low-carbon steels, but manageable with proper preparation. Its weldability is influenced by carbon content (0.22-0.33%) and alloying elements (chromium, molybdenum), which increase the risk of weld cracking and heat-affected zone (HAZ) embrittlement. To ensure strong welds:
Preheat the base metal to 200-300°C (for thicknesses >12mm) to reduce thermal stress.
Use low-hydrogen electrodes (e.g., E8018-B2 for AISI 4130) or gas metal arc welding (GMAW) with ER80S-B2 filler metal to minimize hydrogen-induced cracking.
Perform post-weld heat treatment (PWHT) at 580-620°C to soften the HAZ and restore toughness.
For critical applications (e.g., aerospace), ultrasonic testing (UT) is recommended to verify weld integrity.
Hunan Qilu Steel maintains large inventories of AISI 4130 / DIN 25CrMo4 / JIS SCM430 / BS 708M25 to support quick turnaround times. Common in-stock sizes include:
Hot Rolled Bars: Diameters 14mm, 16mm, 18mm, 20mm, 22mm, 25mm, 28mm, 30mm, 32mm, 35mm, 38mm, 40mm, 45mm, 50mm, 55mm, 60mm, 70mm, 80mm, 90mm, 100mm, 120mm, 150mm, 200mm, 250mm, and 280mm (length 6000-9000mm).
Cold Drawn Bars: Diameters 6mm, 8mm, 10mm, 12mm, 15mm, 20mm, 25mm, 30mm, 40mm, 50mm, 60mm, 70mm, and 80mm (length 6000-9000mm, ground finish).
Hot Rolled Plates: Thicknesses 5mm, 10mm, 15mm, 20mm, 30mm, 40mm, 50mm, 80mm, 100mm, 150mm, and 200mm (width 1500-2500mm, length 2000-5800mm).
Stock levels change daily, so contact our team with your specific size requirements for real-time availability.
JIS SCM430 and BS 708M25 are nearly identical in mechanical performance, with minor differences in chemical composition that do not impact most applications. JIS SCM430 has a slightly higher carbon content (0.28-0.33% vs. 0.22-0.29% for BS 708M25) and lower manganese (0.60-0.85% vs. 0.60-0.90%), leading to a marginally higher tensile strength (900-1100MPa for ≤16mm sizes vs. 800-950MPa for BS 708M25 in the same size range). Both alloys offer identical yield strength (≥600MPa for 16-40mm sizes), elongation (≥14%), and impact value (≥50J at room temperature).
For practical purposes, they are interchangeable. JIS SCM430 is more commonly used in Asian manufacturing (e.g., Japanese automotive), while BS 708M25 is preferred in European and UK projects. Both meet the same quenching and tempering standards, ensuring consistent performance across global supply chains.
1: 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 |
2: Chemical composition
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 | 0.8-1.1 | 0.15-0.25 |
25CrMo4/1.7218 | 0.22-0.29 | 0.40Max | 0.60-0.90 | 0.025Max | 0.035Max | 0.9-1.2 | 0.15-0.30 |
25CrMo | 0.22-0.29 | 0.17-0.37 | 0.60-0.90 | 0.030Max | 0.030Max | 0.9-1.2 | 0.15-0.30 |
SCM430 | 0.28-0.33 | 0.15-0.35 | 0.60-0.85 | 0.030Max | 0.030Max | 0.9-1.2 | 0.15-0.30 |
3: Mechanical properties .
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 |
Sampling and preparation of test pieces for 25CrMo4 quenching and tempering steel.
1): According to EN10083-1, all samples shall be taken at a distance of 12.5mm below the heat treated surface
2): As stipulated in the contract between buyer and seller.
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
Sampling and preparation of test pieces for steel forging.
1: According to EN10250-1, all samples shall be taken at a distance of 4/T below the heat treated surface (with a minimum of 20mm and a maximum of 80mm), and t/2 from the end (where t is the equivalent thickness of the thickness of the ruling section of the forging at the time of heat treatment.
2: As stipulated in the contract between buyer and seller.
4: Surface hardness and hardenability.
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) |
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 | 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.
5: Supply size & Tolerance & Stock size
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 | 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
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 | 280 |
Since the stocks change everyday, if you want to know our stock available information, please contact our salesman.
