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Polished Surface High Strength 4340 Steel Round Bar for Mold Steel Applications
Product Details
| Diameter Range | OD 6-630mm | Tensile Strength | 930-1080 MPa |
|---|---|---|---|
| Yield Strength | 635-1080 MPa | Elongation | 5-13% |
| Impact Resistance | 10-54 J | Brinell Hardness | 248-429 |
| Carbon Content | 0.38-0.43% | Manganese Content | 0.60-0.80% |
| Nickel Content | 1.65-2.00% | Chromium Content | 0.70-0.90% |
| Molybdenum Content | 0.20-0.30% | Thermal Conductivity | 44.5 W/mK |
| Thermal Expansion | 12.3 µm/m°C | Forging Temperature | 1150-1200°C |
| Annealing Temperature | 844°C | ||
| Highlight | Polished Surface Steel Round Bar,High Strength Alloy Steel Bar,Mold Steel Application 4340 Steel Bar |
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Product Description
40CrNiMoA/4340 Steel Alloy Structural Steel Round Bar
AISI 4340 steel is a medium carbon, low alloy steel known for its toughness and strength in relatively large sections. As a nickel chromium molybdenum steel, 4340 alloy steel is generally supplied hardened and tempered in the tensile range of 930-1080 MPa. Pre-hardened and tempered 4340 steels can be further surface hardened by flame or induction hardening and by nitriding.
The 4340 steel offers excellent shock and impact resistance as well as wear and abrasion resistance in the hardened condition. AISI 4340 steel properties provide good ductility in the annealed condition, allowing for bending and forming operations. Fusion and resistance welding is also possible with 4340 alloy steel. ASTM 4340 material is often utilized where other alloy steels lack the hardenability to provide required strength, making it an excellent choice for highly stressed parts.
Specifications and Standards
| 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 (20°C/68°F) | 12.3 µm/m°C | 6.83 µin/in°F |
| Thermal conductivity (typical steel) | 44.5 W/mK | 309 BTU in/hr.ft².°F |
Forging Process
Preheat the steel 4340 first, then heat up to 1150°C - 1200°C maximum for forging, holding until temperature is uniform throughout the section. Do not forge below 850°C. 4340 has good forging characteristics but care must be taken when cooling as the steel shows susceptibility to cracking. Following forging operation, the work piece should be cooled as slowly as possible, with cooling in sand or dry lime recommended.
Heat Treatment
Stress Relieving
For pre-hardened steel, stress relieving is achieved by heating steel 4340 to between 500-550°C. Heat to 600-650°C, hold until temperature is uniform throughout the section, soak for 1 hour per 25 mm section, and cool in still air.
Annealing
A full anneal may be done at 844°C (1550°F) followed by controlled (furnace) cooling at a rate not faster than 10°C (50°F) per hour down to 315°C (600°F). From 315°C (600°F) it may be air cooled.
Tempering
AISI 4340 alloy steel should be in the heat treated or normalized and heat treated condition before tempering. The tempering temperature depends upon the strength level desired. For strength levels in the 260-280 ksi range, temper at 232°C (450°F). For strength in the 125-200 ksi range, temper at 510°C (950°F). Avoid tempering in the 220-260 ksi strength range as this can result in degradation of impact resistance. Tempering should be avoided within the range 250-450°C due to temper brittleness.
Flame or Induction Hardening
Pre-hardened and tempered 4340 steel bars or plates can be further surface hardened by either flame or induction hardening methods, resulting in a case hardness in excess of Rc 50. AISI 4340 steel parts should be heated as quickly as possible to the austenitic temperature range (830-860°C) to the required case depth, followed by immediate oil or water quenching. Following quenching to hand warm, tempering at 150-200°C will reduce stresses in the case with minimal effect on hardness. All de-carburised surface material must first be removed for best results.
Nitriding
Hardened and tempered 4340 alloy steel can also be nitrided, giving a surface hardness of up to Rc 60. Heat to 500-530°C and hold for sufficient time (10-60 hours) to develop the depth of case. Nitriding should be followed by slow cooling (no quench) to reduce distortion problems. The nitrided grade 4340 materials can be machined to near final size, leaving only a small grinding allowance. Surface hardness achievable is 600 to 650HV.
Machinability
Machining is best done with the alloy steel 4340 in the annealed or normalized and tempered condition. It can be readily machined by all conventional methods such as sawing, turning, and drilling. However, in high strength conditions of 200 ksi or greater, machinability is only 25% to 10% that of the alloy in the annealed condition.
Welding
Welding of steel 4340 in the hardened and tempered condition (as normally supplied) is not recommended and should be avoided if possible, because of the danger of quench cracking and altered mechanical properties in the weld heat affected zone. If welding must be carried out, pre-heat to 200-300°C and maintain this temperature while welding. Immediately after welding, stress relieve at 550-650°C prior to hardening and tempering.
Applications
AISI 4340 steel is used in most industry sectors for applications requiring higher tensile/yield strength than 4140 steel can provide.
- Aircraft Landing Gear
- Automotive Components
- Oil and Gas Drilling Equipment
- Forging Applications
- Warm and Cold Forming
- Machine Building
- Transfer Systems (power transmission gears and shafts)
- General engineering industries and structural applications
- Heavy duty shafts, gears, axles, spindles, couplings, pins, chucks, molds
Widely used for transmission systems, tractor motors, and small-to-medium automotive applications. Alternative to 12CrNi3 for higher class carburization and cyanide carburizing parts such as oil drilling claws and mining cones. Commonly used for carburized gears, pinions, shafts, bearings, piston rings, ring gears, crankshafts, and similar components.
Stock Sizes
| Round Bar Diameter | 12-380mm |
|---|
Available Sizes and Conditions
Our steel materials are available in different sizes and conditions specially catered to our customers' needs. They come in round bars, flat bars, plates, and blocks. The conditions of the materials vary from pre-hardened, hot rolled, annealed, quenched and tempered to surface conditions such as black, pre-machined, grinding, and polish.
Why Choose Us?
Quality Assurance
We meticulously source materials only from reputable steel manufacturers to ensure consistency in providing the finest quality steel products for our customers.
We meticulously source materials only from reputable steel manufacturers to ensure consistency in providing the finest quality steel products for our customers.
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We treat every business transaction as a priority, ensuring your purchase order reaches you in the shortest lead time possible.
We treat every business transaction as a priority, ensuring your purchase order reaches you in the shortest lead time possible.
Quality Commitment
Our integrated quality and work management system is continuously improved and certified in accordance with ISO 9001 standards.
Our integrated quality and work management system is continuously improved and certified in accordance with ISO 9001 standards.
Comprehensive Services
We provide quality special steel for all industries with orders of any size, any length, shipped fast. Value-adding services include metal cutting, sizing, machining, and heat treatment.
We provide quality special steel for all industries with orders of any size, any length, shipped fast. Value-adding services include metal cutting, sizing, machining, and heat treatment.
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