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Polished Surface 4340 Steel Bar High Tensile Strength Alloy Steel Round Bar for Tool Steel Applications
Product Details
| Model Number | 1.6582 4340 40CrNiMoA | Surface Treatment | Polished |
|---|---|---|---|
| Diameter Range | OD 6-630mm | Production Capacity | 500tons |
| Tensile Strength | 930-1080 MPa | Yield Strength | 740 MPa |
| Elongation | 12% | Impact Resistance | 47 J |
| Brinell Hardness | 269-331 | Thermal Conductivity | 44.5 W/mK |
| Thermal Expansion | 12.3 µm/m°C | Forging Temperature | 1150°C - 1200°C |
| Annealing Temperature | 844°C | Tempering Temperature | 232°C - 510°C |
| Nitriding Hardness | 600-650HV | ||
| Highlight | Polished Surface Alloy Steel Round Bar,High Tensile Strength 4340 Steel Bar,Tool Steel Application 40CrNiMoA Rod |
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Product Description
Forged Alloy Steel Rod for Tools 1.6582 4340 40CrNiMoA Round Bar
Material Specifications: GB 40CrNiMoA BS S535/AMS 6350 AISI 4340 Round Bar JIS SNCM439
AISI 4340 Steel Overview
AISI 4340 steel is a medium carbon, low alloy steel known for its exceptional toughness and strength in large sections. As a nickel chromium molybdenum steel, it is typically supplied hardened and tempered in the tensile range of 930-1080 Mpa. This material offers excellent shock and impact resistance, along with superior wear and abrasion resistance in the hardened condition. In the annealed state, AISI 4340 provides good ductility for bending and forming operations, while also supporting fusion and resistance welding capabilities.
AISI 4340 steel is a medium carbon, low alloy steel known for its exceptional toughness and strength in large sections. As a nickel chromium molybdenum steel, it is typically supplied hardened and tempered in the tensile range of 930-1080 Mpa. This material offers excellent shock and impact resistance, along with superior wear and abrasion resistance in the hardened condition. In the annealed state, AISI 4340 provides good ductility for bending and forming operations, while also supporting fusion and resistance welding capabilities.
International Standards and Specifications
| Country | USA | Britain | Britain | Japan |
|---|---|---|---|---|
| Standard | ASTM A29 | EN 10250 | BS 970 | JIS G4103 |
| Grades | 4340 | 36CrNiMo4/1.6511 | EN24/817M40 | SNCM 439/SNCM8 |
Chemical Composition
| Standard | Grade | C | Mn | P | S | Si | Ni | Cr | Mo |
|---|---|---|---|---|---|---|---|---|---|
| ASTM A29 | 4340 | 0.38-0.43 | 0.60-0.80 | 0.035 | 0.040 | 0.15-0.35 | 1.65-2.00 | 0.70-0.90 | 0.20-0.30 |
| EN 10250 | 36CrNiMo4/1.6511 | 0.32-0.40 | 0.50-0.80 | 0.035 | 0.035 | <=0.40 | 0.90-1.20 | 0.90-1.2 | 0.15-0.30 |
| BS 970 | EN24/817M40 | 0.36-0.44 | 0.45-0.70 | 0.035 | 0.040 | 0.1-0.40 | 1.3-1.7 | 1.00-1.40 | 0.20-0.35 |
| JIS G4103 | SNCM 439/SNCM8 | 0.36-0.43 | 0.60-0.90 | 0.030 | 0.030 | 0.15-0.35 | 1.60-2.00 | 0.60-1.00 | 0.15-0.30 |
Mechanical Properties
| Condition | Ruling Section (mm) | Tensile Strength (MPa) | Yield Strength (MPa) | Elongation (%) | Izod Impact (J) | Brinell Hardness |
|---|---|---|---|---|---|---|
| T | 250 | 850-1000 | 635 | 13 | 40 | 248-302 |
| T | 150 | 850-1000 | 665 | 13 | 54 | 248-302 |
| U | 100 | 930-1080 | 740 | 12 | 47 | 269-331 |
| V | 63 | 1000-1150 | 835 | 12 | 47 | 293-352 |
| W | 30 | 1080-1230 | 925 | 11 | 41 | 311-375 |
| X | 30 | 1150-1300 | 1005 | 10 | 34 | 341-401 |
| Y | 30 | 1230-1380 | 1080 | 10 | 24 | 363-429 |
| Z | 30 | 1555- | 1125 | 5 | 10 | 444- |
Thermal Properties
| Properties | Metric | Imperial |
|---|---|---|
| Thermal expansion co-efficient | 12.3 µm/m°C | 6.83 µin/in°F |
| Thermal conductivity | 44.5 W/mK | 309 BTU in/hr.ft².°F |
Forging Process
Preheat AISI 4340 steel to 1150°C - 1200°C maximum for forging, ensuring uniform temperature throughout the section. Do not forge below 850°C. While 4340 exhibits good forging characteristics, careful cooling is essential to prevent cracking. After forging, cool the workpiece as slowly as possible, preferably in sand or dry lime.
Heat Treatment Procedures
Stress Relieving
For pre-hardened steel, heat to 500-550°C. For comprehensive stress relief, heat to 600-650°C, maintain until uniform temperature is achieved, soak for 1 hour per 25mm section, and cool in still air.
Annealing
Perform full annealing at 844°C (1550°F) followed by controlled furnace cooling at a maximum rate of 10°C (50°F) per hour down to 315°C (600°F). From 315°C, air cooling is acceptable.
Tempering
Temper AISI 4340 alloy steel after heat treatment or normalization. For strength levels of 260-280 ksi, temper at 232°C (450°F). For 125-200 ksi strength range, temper at 510°C (950°F). Avoid tempering in the 220-260 ksi strength range and the 250-450°C temperature range due to potential impact resistance degradation and temper brittleness.
Flame or Induction Hardening
Pre-hardened and tempered 4340 steel can be surface hardened using flame or induction methods, achieving case hardness exceeding Rc 50. Heat rapidly to 830-860°C austenitic range and immediately quench in oil or water. Temper at 150-200°C to reduce case stresses. Remove all decarburized surface material prior to treatment for optimal results.
Nitriding
Hardened and tempered 4340 alloy steel can be nitrided to achieve surface hardness up to Rc 60. Heat to 500-530°C and maintain for 10-60 hours to develop case depth. Follow with slow cooling to minimize distortion. Achievable surface hardness: 600-650HV.
Machining and Welding
Machinability
Optimal machining occurs with 4340 steel in the annealed or normalized and tempered condition. All conventional methods including sawing, turning, and drilling are suitable. Note that machinability decreases to 25-10% of annealed condition when strength exceeds 200 ksi.
Welding
Welding hardened and tempered 4340 steel is not recommended due to quench cracking risks and altered mechanical properties in the heat-affected zone. If welding is necessary, pre-heat to 200-300°C and maintain during welding. Immediately stress relieve at 550-650°C post-welding. For welding in hardened and tempered condition, stress relieve at 15°C below original tempering temperature after cooling to hand warm.
Applications
AISI 4340 steel is utilized across multiple industries where higher tensile/yield strength than 4140 steel is required:
- Aircraft Landing Gear
- Automotive Components
- Oil and Gas Drilling Equipment
- Forging Applications
- Warm and Cold Forming
- Machine Building
- Power Transmission Gears and Shafts
- Heavy Duty Shafts, Gears, Axles, Spindles
- Couplings, Pins, Chucks, Molds
- Carburized Gears, Pinions, Bearings
- Piston Rings, Ring Gears, Crankshafts
Available Sizes and Conditions
Round Bar Diameter: 12-380mm
Our steel materials are available in various sizes and conditions including round bars, flat bars, plates, and blocks. Conditions range from pre-hardened, hot rolled, annealed, quenched and tempered to surface conditions such as black, pre-machined, grinding, and polish.
Our steel materials are available in various sizes and conditions including round bars, flat bars, plates, and blocks. Conditions range from pre-hardened, hot rolled, annealed, quenched and tempered to surface conditions such as black, pre-machined, grinding, and polish.
Why Choose Our 4340 Steel Products
Quality Assurance
We source materials exclusively from reputable steel manufacturers to ensure consistent, high-quality steel products. Our two decades of customer support demonstrate our commitment to excellence.
Timely Delivery
We prioritize every business transaction to ensure speedy and timely delivery, whether for raw materials or finished products with machining or heat treatment.
Quality Commitment
Our ISO 9001 certified quality management system undergoes continuous improvement and regular audits to meet customer demands and quality considerations.
Comprehensive Services
We provide specialty steel for all industries with unique inventory, fast shipping, and value-adding services including metal cutting, sizing, machining, heat treatment, and sawing.
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