AISI 4140 Round Bar 42CrMo 42CrMo4 Alloy Steel Rod Hot Rolled Forged OD 30-600MM
Product Description
4140 Steel Bar: Complete Technical & Commercial Guide (English)
Quick Overview
AISI 4140 (also known as SAE 4140) is a chromium-molybdenum medium-carbon alloy steel bar defined by ASTM A29/A29M standard. It's globally recognized for its exceptional strength-toughness balance, superior hardenability, and high fatigue resistance, making it the most widely used high-tensile steel for manufacturing critical components across industries. Equivalent to DIN 42CrMo4 (1.7225), JIS SCM440, and GB/T 3077 42CrMo.
1. Basic Information & International Equivalents
| Specification |
Details |
| Primary Standard |
ASTM A29/A29M (USA), SAE J403 |
| Common Names |
4140 alloy steel bar, 4140 quenched and tempered (QT) bar, 4140 chrome-moly bar |
| International Equivalents |
- DIN EN 10083-3: 42CrMo4 (1.7225) (Europe)- JIS G4053: SCM440 (Japan)- GB/T 3077: 42CrMo (China)- ISO 683-13: 42CrMo4- BS EN 10083-3: EN19 (UK)- AFNOR: 42CD4 (France) |
| Typical Delivery Forms |
Round bar, square bar, flat bar, hexagonal bar, forged bar |
| Delivery Conditions |
Hot-rolled, cold-drawn, normalized, quenched & tempered (QT), annealed |
2. Chemical Composition (ASTM A29/A29M)
| Element |
Content Range (%) |
Role |
| Carbon (C) |
0.38-0.43 |
Primary strength contributor; enables heat treatment |
| Silicon (Si) |
0.15-0.35 |
Deoxidizer; improves strength and heat resistance |
| Manganese (Mn) |
0.75-1.00 |
Enhances hardenability and tensile strength |
| Chromium (Cr) |
0.80-1.10 |
Increases hardness, wear resistance, and corrosion resistance |
| Molybdenum (Mo) |
0.15-0.25 |
Boosts hardenability, high-temperature strength, and prevents temper brittleness |
| Phosphorus (P) |
≤0.035 |
Controlled impurity (max 0.030% for premium grades) |
| Sulfur (S) |
≤0.040 |
Controlled impurity (free-machining grades have 0.08-0.15%) |
| Nickel (Ni) |
≤0.25 |
Trace element (some grades may have higher content) |
3. Mechanical Properties (Quenched & Tempered Condition)
| Property |
Minimum Value |
Typical Range |
Test Standard |
| Tensile Strength (σb) |
≥1080 MPa |
1080-1200 MPa |
ASTM E8/E8M |
| Yield Strength (σ0.2) |
≥930 MPa |
930-1050 MPa |
ASTM E8/E8M |
| Elongation (δ5) |
≥12% |
12-18% |
ASTM E8/E8M |
| Reduction of Area (ψ) |
≥45% |
45-55% |
ASTM E8/E8M |
| Impact Energy (Akv) |
≥63 J (at -20°C, V-notch) |
63-80 J |
ASTM E23 |
| Hardness |
28-32 HRC (QT condition) |
28-36 HRC |
ASTM E18 |
Note: Properties vary with section size and heat treatment parameters
4. Key Characteristics & Advantages
Excellent Strength-Toughness Balance: Maintains ductility while delivering ultra-high strength
Superior Hardenability: Can be uniformly heat-treated even in large cross-sections
No Temper Brittleness: Molybdenum addition prevents embrittlement after tempering
High Fatigue Resistance: Ideal for components under cyclic loading (axles, shafts, gears)
Good Low-Temperature Toughness: Performs reliably down to -20°C
Surface Hardenability: Can be induction hardened to 50-55 HRC while retaining core toughness
Improved Machinability: Available in free-machining grades with controlled sulfur content
Weldability: Requires preheating (200-300°C) and post-weld heat treatment to avoid cold cracking
5. Heat Treatment Guidelines
| Process |
Temperature |
Cooling Method |
Purpose |
| Quenching |
840-870°C |
Oil cooling |
Hardening to achieve base strength (55-60 HRC) |
| Tempering |
540-680°C |
Air cooling |
Reducing brittleness while maintaining strength (28-36 HRC) |
| Normalizing |
850-900°C |
Air cooling |
Homogenizing structure before final heat treatment |
| Annealing |
680-700°C |
Furnace cooling |
Softening for improved machinability (HB ≤217) |
| Induction Hardening |
900-950°C |
Water spray |
Enhancing surface hardness (50-55 HRC) for wear resistance |
| Stress Relieving |
550-600°C |
Air cooling |
Removing internal stresses after machining/welding |
6. Typical Applications
4140 steel bar is the material of choice for highly stressed components requiring strength, toughness, and durability:
Automotive Industry: Crankshafts, connecting rods, drive shafts, gears, steering knuckles, axle shafts
Oil & Gas Industry: Drill pipe joints, wellhead equipment, pressure vessels, downhole tools, offshore platform components
Heavy Machinery: Gearboxes, hydraulic cylinders, machine tool spindles, roller shafts, forging dies
Power Generation: Turbine components, generator shafts, high-pressure steam pipes
Aerospace: Landing gear components, structural parts (after special heat treatment)
General Engineering: Bolts, nuts, fasteners, couplings, sprockets, pinions, and other load-bearing parts
7. Standard Sizes & Supply Range
| Bar Type |
Dimension Range |
Notes |
| Round Bar |
- Hot-rolled: Ø5mm - 200mm- Forged: Ø140mm - 900mm (custom up to 3000mm)- Cold-drawn: Ø3mm - 100mm |
Most common form; available in precision tolerances |
| Square Bar |
10mm × 10mm - 300mm × 300mm |
Used for shafts, keys, and structural components |
| Flat Bar |
Thickness: 5mm - 100mmWidth: 20mm - 300mm |
Ideal for wear plates, brackets, and custom fabrication |
| Hexagonal Bar |
Across flats: 10mm - 100mm |
Used for bolts, nuts, and precision components |
| Length |
3000mm - 12000mm |
Standard length: 6000mm/12000mm; custom lengths available |
| Surface Finish |
Hot-rolled (black), cold-drawn (bright), shot-blasted, or coated |
According to customer requirements |
| Quality Grade |
I/II/III (ultrasonic testing available for critical applications) |
EN 10160 UT Class II standard for high-integrity components |
8. Commercial Product Description Template (For Export)
Product Name: AISI 4140 (SAE 4140) Quenched & Tempered Alloy Steel Round Bar (Equivalent to DIN 42CrMo4/1.7225, JIS SCM440)
Specifications:
Diameter: Ø50mm
Length: 6000mm
Delivery Condition: Quenched & Tempered (QT)
Hardness: 28-32 HRC
Surface Finish: Shot-blasted and oiled
Certification: MTC 3.1 (EN 10204), ISO 9001, ultrasonic test report (EN 10160 Class II)
Key Advantages:
High tensile strength (≥1080 MPa) with excellent toughness balance
Full compliance with ASTM A29/A29M and international equivalents
Stable supply from Shagang/Baosteel mill sources
Custom cutting-to-length, chamfering, and surface treatment services available
Packaging: Seaworthy wooden crates with moisture-proof paper, steel strapping, and end protectors
9. Quotation Inquiry Response Guide (For International Trade)
When responding to 4140 steel bar inquiries, emphasize these value points to differentiate your offer:
Material Certification: Provide MTC (Mill Test Certificate) 3.1, EN 10204 compliance, and ISO 9001 certification
Equivalent Assurance: Clearly state compatibility with 42CrMo4/SCM440 for global acceptance
Quality Control: Highlight ultrasonic testing, chemical composition verification, and mechanical property testing
Supply Capacity: Mention monthly production volume and delivery lead time (typically 3-4 weeks)
Technical Support: Offer free material selection advice and heat treatment recommendations
Custom Solutions: Provide cutting-to-length, chamfering, threading, and surface treatment services
Cost Efficiency: Highlight competitive pricing for QT bars compared to alternative high-strength materials
Q1: Why choose us?
A: Our company, as an internationally experienced and professionalsupplier, has been engaged in steel business for more than ten years. Wecan provide a variety of steel products with high quality to our clients.
Q2: Can you provide OEM/ODM service?
A: Yes. Please feel free to contact us for more details
Q3:What is your terms of payment?
A: 100% T/T advance.
30% T/T and balance against copy of documents.
30% T/T advance, balance L/C at sight.
Q4: Can we visit your factory?
A: Warmly welcome. Once we have your schedule, we will arrange theprofessional sales team to follow up your case.
Q5: Can you provide sample?
A: Yes. Sample is free for regular sizes, but the buyer needs to pay freightcost.
Q6: How long is your delivery time?
A: Regular lead time is 15 to 30 days after receiving deposit.
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