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4340 40CrNiMoA Forged Alloy Steel Round Bar with Polished Surface for High Strength Applications

Minimum Order Quantity	1 Ton
Price	US $780-1,180 / Ton

Product Details

Diameter Range	6-630mm	Tensile Strength	930-1080 MPa
Yield Strength	740 MPa	Elongation	12%
Impact Resistance	47 J	Brinell Hardness	269-331
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°C-1200°C
Annealing Temperature	844°C
Highlight	4340 Forged Steel Round Bar , 40CrNiMoA Alloy Steel Round Bar , Polished Steel Round Bar

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Product Description

ASTM 4340, JIS Sncm8, 40CrNiMoA Forged Steel Round Bar

GB 40CrNiMoA BS S535/AMS 6350 AISI 4340 Round Bar JIS SNCM439

AISI 4340 steel is a medium carbon, low alloy steel known for its toughness and strength in relatively large sections. AISI 4340 is a nickel chromium molybdenum steel typically 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 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, specimen oil hardened, 600°C (1110°F) temper	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, heat up to 1150°C - 1200°C maximum for forging, hold 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. Cooling in sand or dry lime is recommended.

Heat Treatment

Stress Relieving

For 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 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). Do not 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.

Flame or Induction Hardening

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.

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, drilling etc. However in the high strength conditions of 200 ksi or greater the machinability is only from 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 at all possible, because of the danger of quench cracking, as the mechanical properties will be altered within the weld heat affected zone. If welding must be carried out, pre-heat to 200 to 300°C and maintain this while welding. Immediately after welding stress relieve at 550 to 650°C, prior to hardening and tempering. If welding in the hardened and tempered condition is really necessary, then the work piece, immediately on cooling to hand warm, should be if possible stress relieved at 15°C below the original tempering temperature.

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 Industry
Oil and Gas Drilling
Forging Applications
Warm and Cold Forming
Machine Building
Transfer Systems (power transmission gears and shafts)
General engineering industries and structural use applications
Heavy duty shafts, gears, axles, spindles, couplings, pins, chucks, molds

General Applications: Widely used for transmission systems, motors of tractors and middle-small automobiles. Alternative to 12CrNi3 for making higher class carburization and cyanide carburizing parts such as oil drilling, claws and cone for mining. Commonly used for carburized gears, pinions, shafts, bearings, piston rings, ring gears, crankshafts, etc.

Stock Sizes

Product Form	Diameter
Round Bar	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.

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We provide quality special steel for all industries with orders of any size, any length. We offer value-adding services including metal cutting, sizing, machining, and heat treatment.

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We provide quality special steel for all industries. Orders of any size, any length, ship fast. We carry a unique inventory of specialty special steel and provide related value-adding services including metal cutting, sizing, machining (blanking, milling, grinding), heat treatment, and sawing for small or large quantities. Excellent customer service guaranteed.

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4340 40CrNiMoA Forged Alloy Steel Round Bar with Polished Surface for High Strength Applications

4340 Forged Steel Round Bar

40CrNiMoA Alloy Steel Round Bar

Polished Steel Round Bar