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E: enquiry@qilumetal.com
E: enquiry@qilumetal.com
No. 18 Xiangfu Middle Road,Yuhua District, Changsha City
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Grade: AISI 4140
Equivalent Steel: EN 42CrMo4 1.7225, GB 42CrMo, BS 708M40, JIS SCM440
AISI 4140 is a chromium-molybdenum alloy steel that derives its exceptional hardenability, high strength, and good toughness from a carefully balanced chromium-molybdenum (Cr-Mo) matrix . The nominal composition of 0.38-0.43% carbon provides the foundational hardness, while chromium (0.80-1.10%) enhances hardenability and wear resistance, and molybdenum (0.15-0.25%) contributes strength at elevated temperatures and reduces temper brittleness . Controlled manganese (0.75-1.00%) and silicon (0.15-0.35%) improve deoxidation and overall strength, with strict limits on phosphorus (max 0.035%) and sulfur (max 0.040%) to maintain material purity and consistent machinability.
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4140
Qilu
42CrMo4 (1.7225) is a premium Cr-Mo quenched and tempered steel compliant with EN 10083-3 and EN 10250-3. Equivalent to ASTM 4140, JIS SCM440, GB 42CrMo and BS 708M40. It is widely used for shafts, gears, bolts, spindles and other high-stress machinery parts. We supply 4140 QT alloy steel in multiple bar forms, including SAE 4140 round bar, 4140 steel bar and forged bar, for machining, heat treatment and industrial component manufacturing.
The combined effect of chromium (Cr) and molybdenum (Mo) alloying elements endows this steel with enhanced hardenability, anti-temper brittleness and mild corrosion resistance. Compared with ordinary carbon steel, 42CrMo4 maintains stable mechanical properties under heavy load, alternating stress and moderate high-temperature working conditions, so it is extensively applied for critical load-bearing components worldwide.
Country | USA | Europe | China | British | Japan |
Standard | ASTM A29 | EN10083-3 | GB/T3077 | BS970 | JIS G4105 |
Grade | 4140 | 42CrMo4/1.7225 | 42CrMo | 708M40 | SCM440 |
Grade | C | Si | Mn | P | S | Cr | Mo |
4140 | 0.38-0.43 | 0.15-0.35 | 0.75-1.00 | 0.035Max | 0.040Max | 0.80-1.10 | 0.15-0.25 |
42CrMo4/1.7225 | 0.38-0.45 | 0.40Max | 0.60-0.90 | 0.025Max | 0.035Max | 0.90-1.20 | 0.15-0.30 |
42CrMo | 0.38-0.45 | 0.17-0.37 | 0.50-0.80 | 0.035Max | 0.035Max | 0.90-1.20 | 0.15-0.25 |
708M40 | 0.36-0.44 | 0.10-0.40 | 0.70-1.00 | 0.035Max | 0.040Max | 0.90-1.20 | 0.15-0.25 |
SCM440 | 0.38-0.43 | 0.15-0.35 | 0.60-0.85 | 0.035Max | 0.040Max | 0.90-1.20 | 0.15-0.30 |
We divide properties into two categories: standard quenched and tempered steel (per EN10083-3) and open die forging steel (per EN10250-3), including longitudinal (L) and transverse (Tr) indicators for forgings. All tests follow European standard sampling rules.
Sampling rule: Take samples 12.5mm below the heat-treated surface as required by EN10083-1.
Size range | Tensile strength | Yield strength | Alongation | Area of reduction | Impact value At RT/J |
d≤16 t≤8 | 1100-1300Mpa | 900Mpa Min | 10% Min | 40% Min | / |
16＜d≤40 8＜t≤20 | 1100-1200Mpa | 750Mpa Min | 11% Min | 45%Min | 35J Min |
40＜d≤100 20＜t≤60 | 900-1100Mpa | 650Mpa Min | 12% Min | 50%Min | 35J Min |
100＜d≤160 60＜t≤100 | 800-950Mpa | 550Mpa Min | 13% Min | 50%Min | 35J Min |
160＜d≤250 100＜t≤160 | 750-900Mpa | 500Mpa Min | 14% Min | 55%Min | 35J Min |
Sampling rule: Take samples 4/T (min 20mm, max 80mm) below the heat-treated surface and t/2 from the forging end (EN10250-1). L=Longitudinal, Tr=Transverse.
Size range | Tensile strength | Yield strength | Alongation | Impact value at RT/J | ||
L | Tr | L | Tr | |||
d≤160 | 750Mpa Min | 500Mpa Min | 14% Min | 10% Min | 30J Min | 16J Min |
160＜d≤330 | 700Mpa Min | 460Mpa Min | 15% Min | 11% Min | 27J Min | 14J Min |
330＜d≤660 | 600Mpa Min | 390Mpa Min | 16% Min | 12% Min | 22J Min | 12J Min |
Heat Treatment | Hardness |
Flame or Induction hardening | 53HRC |
Treated to improve shearability (+S) | HB255Max |
Soft annealed (+A) | HB241Max |
Quenched and tempred (+QT) | HRC28-32(Common Range) |
For orders with customized hardenability requirements, the HRC hardness range at different distances from the quenched end is as follows:
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 | 61 | 61 | 61 | 60 | 60 | 59 | 59 | 58 | 56 | 53 | 51 | 48 | 47 | 46 | 45 |
min | 53 | 53 | 52 | 51 | 49 | 43 | 40 | 37 | 34 | 32 | 31 | 30 | 30 | 29 | 29 | |
Hardness In HRC + HH | max | 61 | 61 | 61 | 60 | 60 | 59 | 59 | 58 | 56 | 53 | 51 | 48 | 47 | 46 | 45 |
min | 56 | 56 | 55 | 54 | 52 | 48 | 46 | 44 | 41 | 39 | 38 | 36 | 36 | 35 | 34 | |
Hardness In HRC + HL | max | 58 | 58 | 58 | 57 | 56 | 54 | 53 | 51 | 49 | 46 | 44 | 42 | 41 | 40 | 40 |
min | 53 | 53 | 52 | 51 | 49 | 43 | 40 | 37 | 34 | 32 | 31 | 30 | 30 | 29 | 29 | |
Scatter bands for the Rockwell - C hardness in the end quench hardenability test.
Heat the 42CrMo4 ingot to 1100–1200°C in a heating furnace for uniform temperature distribution.
Start forging; the final forging temperature shall not be lower than 800–900°C to avoid material cracking.
Cool naturally in air or bury in sand for slow cooling after forging to release internal stress.
Heat to 680–720°C → Soak fully → Cool slowly inside the furnace.
Purpose: Reduce hardness, improve cutting performance and eliminate forging stress.
Heat to 840–870°C → Soak → Air cooling.
Purpose: Refine grain, uniform internal structure, prepare for subsequent quenching & tempering.
Heating: 820–880°C → Soak thoroughly
Quenching medium: Water (for lower temperature range) or oil (for upper temperature range)
Tempering: 540–680°C → Air cooling after furnace discharge.
This process achieves the best comprehensive mechanical properties.
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. | |||||
We maintain over 10,000 tons of in-stock 42CrMo4 monthly for fast delivery. Stock changes daily; contact our sales team for real-time inventory.
Hot Rolled Bar Stock Diameter: 16, 18, 20, 22, 24, 25, 26, 27, 28, 30, 31, 32, 33, 35, 36, 38, 39, 40, 42, 45, 46, 48, 50, 52, 55, 56, 58, 60, 62, 63, 65, 68, 70, 72, 75, 78, 80, 82, 83, 85, 87, 90, 95, 100, 105, 110, 115, 120, 125, 130, 135, 140, 145, 150, 155, 160, 170, 180, 190, 200, 210, 220, 230, 240, 250, 260, 270, 280, 290, 300, 310mm
Hot Forged Bar Stock Diameter: 310, 320, 330, 340, 350, 360, 370, 380, 390, 400, 410, 420, 430, 440, 450, 460, 470, 480, 490, 500, 510, 520, 530, 540, 550mm
42CrMo4 steel has poor weldability. For steel material, weldability has strong relationship with carbon element, when the carbon element is more than 0.25%, the weldability will be starting to get worse. The carbon element of 42CrMo4 is around 0.42%, so the weldability is not good.
With high strength, toughness, wear resistance and fatigue resistance, 42CrMo4 covers multiple high-end industries:
Automotive Industry: Engine crankshafts, connecting rods, transmission gears, axles and chassis load-bearing parts.
Aerospace Industry: Aircraft engine components, landing gear structural parts, high-load transmission components.
Machine Tools & General Machinery: Main shafts, spindles, gear shafts and high-strength couplings.
Mining & Metallurgical Equipment: Crusher gears, conveyor shafts, rolling mill accessories and heavy-load transmission parts.
Power Generation Industry: Turbine shafts, generator rotors and wind power main shafts.
Petrochemical Industry: High-pressure pipeline joints, drilling tool accessories and high-temperature resistant structural parts.
A1: They are equivalent grades for most working conditions. Minor differences exist in chemical tolerance, impurity limits and regional standards. 42CrMo4 follows European EN standards, 4140 for American ASTM, SCM440 for Japanese JIS. They can be mutually replaced in conventional projects.
A2: The conventional QT hardness is 28–32 HRC. After induction/flame surface hardening, surface hardness can reach 53 HRC for enhanced wear resistance. Soft annealed state ≤HB241.
A3: 42CrMo4 contains Cr and Mo elements, with much higher hardenability, strength, toughness and fatigue resistance. It is suitable for heavy-load and alternating stress conditions; 45# steel is for low-load ordinary parts with better weldability and lower cost.
A4: Not recommended for direct welding. Due to high carbon and alloy elements, cracks easily occur. Strict preheating and post-weld heat treatment are required if welding is necessary. Welding is not suggested for heavy-load parts.
Contact us for quotation, lead time, sample, or custom specification of 4140 alloy steel.
