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.
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.
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.
ASTM A29/A29m Hot Rolled Alloy Steel Round Bars SAE4340 10-350mm
