Product Description
1: 4340 steel introduction
AISI 4340 steel is a medium carbon, low alloy steel known for its toughness and strength in relatively large sections. AISI 4340 is also one kind of nickel chromium molybdenum steels. 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 has good shock and impact resistance as well as wear and abrasion resistance in the hardened condition. AISI 4340 steel properties offer good ductility in the annealed condition, allowing it to be bent or formed. Fusion and resistance welding is also possible with our 4340 alloy steel. ASTM 4340 material is often utilized where other alloy steels do not have the hardenability to give the strength required. For highly stressed parts it is excellent choice. AISI 4340 alloy steel can also be machined by all customary methods.
2: 4340 Steel equivalent
| Country | Japan | Germany | Britain | USA |
| Standard | JIS G4103 | EN10250 | BS970 | ASTM A29 |
| Grade | SNCM439 | 36CrNiMo4/1.6511 | EN24/817M40 | 4340 |
3: 4340 steel chemical composition
| Grade | C | Si | Mn | P | S | Cr | Mo | Ni |
| 4340 | 0.38-0.43 | 0.15-0.35 | 0.6-0.8 | 0.035 | 0.04 | 0.7-09 | 0.2-0.3 | 1.65-2.0 |
| 36CrNiMo4 | 0.32-0.4 | 0.4 | 0.5-0.8 | 0.035 | 0.035 | 0.9-1.2 | 0.15-0.3 | 0.90-1.20 |
| EN24 | 0.36-0.44 | 0.1-0.4 | 0.45-0.7 | 0.035 | 0.04 | 1.0-1.4 | 0.2-0.35 | 1.3-1.7 |
| SNCM439 | 0.36-0.43 | 0.15-0.35 | 0.6-0.9 | 0.03 | 0.03 | 0.6-1.0 | 0.15-0.3 | 1.6-2.0 |
4: 4340 steel mechanical properties
The mechanical properties mainly include tensile strength, yield strength, elongation, area or reduction, hardness, impact value, non-metalic inclusion etc. Different heat treatment, the mechanical properties will be different, such as normalized, tempered, QT. If you want to know the properties, kindly contact the salesman.
5: 4340 steel overviews
| Size | Round | Dia 6-1200mm |
| Plate/Flat/Block | Thickness 6mm-500mm | |
| Width 20mm-1000mm | ||
| Heat treatment | Normalized ; Annealed ; Quenched ; Tempered | |
| Surface condition | Black; Peeled; Polished; Machined; Grinded; Turned; Milled | |
| Delivery condition | Forged; Hot rolled; Cold drawn | |
| Test | Tensile strength, Yield strength, elongation, area of reduction, impact value, hardness, grain size, ultrasonic test, US inspection, magnetic particle testing, etc. | |
| Payment terms | T/T;L/C;/Money gram/ Paypal | |
| Trade terms | FOB; CIF; C&F; etc.. | |
| Delivery time | 30-45 days | |
| Application | 4340 alloy steels are used for aircraft landing gear, automotive, oil and gas drilling, warm and cold forming, machine building, transfer systems like power transmission gears and shafts, general engineering industries and structural use applicatios such as heavy duty shafts, gears, axles, spindles, couplings, pins, chucks, molds and so on. | |
6. Heat Treatment
Stress RelievingFor pre-hardened steel stress relieving is achieved by heating steel 4340 to between 500 to 550°C. Heat to 600 °C - 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 for 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). And don't temper the 4340 steels if it is in the 220 - 260 ksi strength range as tempering can result in degradation of impact resistance for this level of strength.
Tempering should be avoided if possible within the range 250 °C - 450 °C due to temper brittleness.
Hardening
As mentioned above, pre-hardened and tempered 4340 steel bars or plates can be further surface hardened by either the 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 °C - 860 °C) and required case depth followed by an immediate oil or water quenching, depending upon hardness required, workpiece size/shape and quenching arrangements.
Following quenching to hand warm, tempering at 150°C - 200°C will reduce stresses in the case with minimal effect on its hardness.
All de-carburised surface material must first be removed to ensure 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°C - 530°C and hold for sufficient time (from 10 to 60 hours) to develop the depth of case. Nitriding should be followed by slow cooling (no quench) reducing the problem of distortion. The nitrided grade 4340 materials can therefore be machined to near final size, leaving a small grinding allowance only. The tensile strength of the 4340 steel material core is usually not affected since the nitriding temperature range is generally below the original tempering temperature employed.
Surface hardness achievable is 600 to 650HV.
7: Delivery condition
For hot forged rolled bar, usually the delivery condition is hot forged or rolled, annealed/QT, rough turned/Black surface.
For hot forged or hot rolled bar, usually the delivery condition is hot rolled, annealed/QT, Black surface.
For hot forged plate, usually the delivery condition is hot forged, annealed/QT, milled surface/Black surface
For hot rolled plate, usually the delivery condition is hot rolled, annealed/QT, black surface.
Hunan Qilu Industrial Co., Ltd has the capacity to forge round steel, steel flat, square steel, module, shaft and roller, etc. The main specifications of the products include Φ80-1000mm forging materials and 80-1200mm square billets and which the maximum piece weight can reach 50T.
Hunan Qilu Industrial Co., Ltd were already engaged in exporting steel for 11 years, could supply a great variety of hot forged, hot rolled and cold drawn Steels, including engineering steel, cold work tool steel, hot work tool steel, plastic mold steel, spring steel, high speed steel, stainless steel etc., besides Qilu Industrial also has their own heating treatment shop and machining shop to provide heating and cutting service.
Since 2008 year, Hunan Qilu Industrial has the right to export all FORGED STEEL behalf of Qilu Speical Steel Co.,ltd which is specialized in smelting and forging of special steel since 1965 year, now Qilu special steel is one of the biggest manufacturer of forged product in China.The forged products are used in Automotive, Aerospace, Power Generation, Oil & Gas, Transportation and Industrial. We already set up the warehouse in Wuxi and Dongguan city, more than 20000 tons ex-stock could be supplied with kinds of size.
Qilu Industrial is the professional one-stop steel manufacturer, stockist and exporter in China, our customers spread all over the world, include West Europe, North America, South America, Asia, Middle Asia, Africa, Australia, etc.
The company owns advanced special steel smelting facilities and forging processing equipments, the main steel-making equipment include 2 sets of 50t ultra-high power electric arc furnaces,2 sets of 60t LF refining furnaces,1 set of 60t vacuum degassing refining furnace and 4 sets of 1-20t electroslag re-melting furnaces.The main forging equipments mainly include:3 sets of 5t electro-hydraulic hammers, 1 set of high-speed forging units of 800t,1600t,2000t and 4500t respectively.
Hunan Qilu Industrial CO., LTDWeb: qilusteel.en.made-in-china.com