Alloy Steel 4140 Round Bar

Alloy Steel 4140 Round Bar (UNS G41400 / EN 1.7225) is a chromium-molybdenum low-alloy steel bar supplied to ASTM A29 / A322, commonly stocked pre-hardened at 262-321 HBW. With 0.38-0.43% carbon it hardens deeply, reaching a typical quenched and tempered strength of 900-1100 MPa, and is used for shafts, gears, crankshafts, drill collars and high-strength fasteners.

➡️ AISI 4140 | UNS G41400 | EN 1.7225

➡️ ASTM, EN, JIS & International Standards

➡️ Supply Conditions

➡️ Multiple Diameters & Supply Lengths

➡️ Global Export & International Delivery

Country of Origin:

Europe, Japan, USA

Material Type:

Alloy Steel

UNS Number:

G41400

Wr. No.:

1.7225

MTC Available:

EN 10204 3.1

Product Description for Alloy Steel 4140 Round Bar

Alloy Steel 4140 Round Bar is a solid cylindrical bar produced from low-alloy chromium-molybdenum steel grade AISI/SAE 4140 (UNS G41400). Bar is supplied to ASTM A29 / A29M for general requirements and ASTM A322 for hot-wrought alloy steel bars, with cold-finished bar under ASTM A108. It is one of the most widely used engineering steels in the world and is frequently stocked in the pre-hardened, quenched and tempered condition.

The grade contains 0.38-0.43% carbon with 0.80-1.10% chromium and 0.15-0.25% molybdenum. Compared with 4130 the higher carbon content raises the attainable hardness and strength and allows through-hardening in much larger sections, at the cost of reduced weldability. After quenching and tempering, tensile strengths of 900-1100 MPa with good toughness are routine, and higher strengths are achievable with lower tempering temperatures.

Bars are supplied hot-rolled, annealed, normalised, or quenched and tempered, in diameters from about 10 mm to 600 mm and lengths of 3 to 6 m. Pre-hardened bar at 262-321 HBW is a common stock condition that allows components to be machined directly to final size without further heat treatment. The grade also responds well to nitriding and to induction hardening.

Typical applications include shafts, axles, spindles, gears, pinions, crankshafts, connecting rods, drill collars and other oilfield components, high-strength bolts and studs to ASTM A193 Grade B7, forging dies, jigs and fixtures, and hydraulic and mining machinery parts. Industries served include oil and gas, automotive, mining, power transmission, tooling, machine building and general heavy engineering.

Common Applications of Alloy Steel 4140 Round Bar

➡️ Machined shafts, spindles, valve stems, pump sleeves and pins for food, beverage, dairy and pharmaceutical equipment, where the passive chromium oxide film resists both product acids and caustic clean-in-place chemicals.

➡️ Fasteners, studs, bolts, threaded rod and anchor components produced from bar stock, chosen for corrosion resistance combined with the ductility needed for cold heading and thread rolling.

➡️ Chemical, water treatment and general process plant parts such as agitator shafts, flange blanks, nozzles and support components handling water, steam and mildly corrosive media free of significant chlorides.

➡️ Architectural and structural hardware including handrail stanchions, balustrade fittings, tension rods and bollards, where a bright ground or polished bar finish provides both appearance and low maintenance.

International Equivalent Grade for AS 4140 Round Bar

Standard

Country / Region

Grade

ASTM A29 / A29M

USA

Grade 4140 (UNS G41400)

ASTM A322

USA

Grade 4140 - hot-wrought alloy steel bar

ASTM A108

USA

Grade 4140 - cold-finished bar

ASTM A193 / A193M

USA

Grade B7 - bolting material based on 4140 type chemistry

SAE J404

USA

4140

EN 10083-3

Europe / EU

42CrMo4 (1.7225)

BS EN 10083-3

United Kingdom

42CrMo4 (1.7225)

BS 970 Part 1 (superseded)

United Kingdom

708M40

JIS G4105

Japan

SCM440

GB/T 3077

China

42CrMo

KS D 3867

South Korea

SCM440

ISO 683-2

International

42CrMo4

Technical Specification for Alloy Steel 4140 Round Bar

Specification

Value

Unit

Material

Alloy steel

Grade

4140 / UNS G41400 / 42CrMo4

Product Form

Round bar / rod

Standard

ASTM A29 / A29M and ASTM A322

Diameter

10 - 600 (available range)

Length

3 - 6 (standard random or fixed)

Manufacturing Process

Hot rolled, forged, or hot rolled and cold drawn

Production Route

EAF melting with ladle refining, continuous cast or ingot, hot rolling or forging, heat treatment

Surface Finish

Hot-rolled black, peeled, rough turned, cold-drawn bright, turned ground and polished

Heat Treatment / Delivery Condition

Annealed, normalised, or quenched and tempered (pre-hardened) as ordered

Annealing Temperature

810 - 850 then furnace cool (typical)

deg C

Normalising Temperature

870 - 900 then air cool (typical)

deg C

Hardening Temperature

840 - 870 followed by oil quench (typical)

deg C

Tempering Temperature

540 - 680 depending on required strength (typical)

deg C

Nitriding Temperature

500 - 530 giving a case hardness of about 600 - 650 HV (typical)

deg C

Tolerance Standard

ASTM A29 / A29M and ASTM A108

Carbon Equivalent (CEV)

0.75 (typical, IIW formula)

Density

7.85 (typical)

g/cm3

Melting Point

1416 - 1495 (approximate)

deg C

Thermal Conductivity

42.6 at 100 deg C (typical)

W/m.K

Coefficient of Thermal Expansion

12.3 at 20 - 100 deg C (typical)

micro-m/m.K

Specific Heat

473 at 50 - 100 deg C (typical)

J/kg.K

Electrical Resistivity

0.220 (typical)

micro-ohm.m

Modulus of Elasticity

205 (typical)

GPa

Magnetic Properties

Ferromagnetic

Applicable Testing Standard

ASTM A370, ASTM E8 / E8M, ASTM E23, ASTM E10, ASTM E415

Certification / Inspection Documents

EN 10204 Type 3.1 or 3.2 mill test certificate

Technical Specifications

Get the key technical specifications for Alloy Steel 4140 Round Bar

Alloy Steel 4140 Round Bar is ordered to ASTM A29 / A29M and ASTM A322 for hot-wrought bar and ASTM A108 for cold-finished bar. These specifications control composition, dimensions and quality but do not impose mechanical minima, so a heat treatment condition and required property range must be stated by the purchaser. Where EN 10083-3 is invoked for the equivalent grade 42CrMo4, mechanical minima are mandatory and tabulated by ruling section, which is often the more convenient route for a buyer needing guaranteed values.

Hardening is performed from 840-870 deg C with an oil quench, followed by tempering between about 540 and 680 deg C. Hardenability is high, so sections up to roughly 100 mm can be through-hardened, and larger diameters develop useful properties to considerable depth.

Pre-hardened bar, supplied quenched and tempered at 262-321 HBW, is widely stocked. It allows parts to be machined to final size without further heat treatment, avoiding distortion and scale, and is the usual choice for shafting, tooling plate and fixtures.

Tempering between about 250 and 400 deg C should be avoided due to tempered martensite embrittlement, and slow cooling from tempering temperatures above 575 deg C should be avoided in susceptible heats to limit temper embrittlement.

Testing typically covers analysis to ASTM E415, tensile testing to ASTM A370 and E8 / E8M, hardness to ASTM E10, Charpy testing to ASTM E23 and ultrasonic examination to ASTM A388 for heavy sections.

Chemical Composition for Alloy Steel 4140 Round Bar

Element

Symbol

Min

Max

Unit

Carbon

0.38

0.43

Manganese

0.75

1.00

Silicon

0.15

0.35

Phosphorus

0.035

Sulfur

0.040

Chromium

0.80

1.10

Molybdenum

0.15

0.25

Iron

Balance

Chemical Composition

View the chemical composition and applicable material limits for AS 4140 Round Bar

Carbon at 0.38-0.43% sets the maximum attainable hardness. A fully quenched structure reaches about 55-58 HRC before tempering, which is where the strength advantage over 4130 comes from and why the grade is chosen for heavily loaded components. The same carbon content raises the carbon equivalent to around 0.75 and makes the grade appreciably harder to weld.

Chromium at 0.80-1.10% is the principal hardenability element. It delays the transformation of austenite to ferrite and pearlite so that martensite forms throughout thick sections with only an oil quench. Chromium also forms stable carbides that resist softening during tempering, allowing high tempering temperatures without excessive strength loss, and it contributes to wear resistance and to nitriding response.

The 0.15-0.25% molybdenum adds further hardenability and secondary hardening during tempering, and it suppresses temper embrittlement. Without molybdenum, slow cooling through the 375-575 deg C range would allow phosphorus and other tramp elements to segregate to prior austenite grain boundaries and sharply reduce impact toughness.

Manganese at 0.75-1.00%, higher than in 4130, provides additional hardenability and ties up sulphur as manganese sulphide, preventing hot shortness during rolling and forging.

Silicon at 0.15-0.35% acts as the deoxidiser, and phosphorus and sulphur, limited to 0.035% and 0.040%, are residuals that reduce toughness and transverse ductility, and are often restricted further for critical applications.

Mechanical Properties for Alloy Steel 4140 Round Bar

Mechanical Property

Value

Unit

Tensile Strength (annealed)

655 (typical)

MPa

Yield Strength (annealed)

415 (typical)

MPa

Hardness (annealed)

197 max (typical)

HBW

Tensile Strength (normalised)

1020 (typical)

MPa

Yield Strength (normalised)

655 (typical)

MPa

Tensile Strength (quenched and tempered, 16 - 40 mm per EN 10083-3 42CrMo4)

1000 - 1200 (specified range)

MPa

Yield Strength 0.2% Proof (quenched and tempered, 16 - 40 mm)

750 (minimum)

MPa

Elongation in 50 mm (quenched and tempered, 16 - 40 mm)

11 (minimum)

Tensile Strength (quenched and tempered, over 40 to 100 mm)

900 - 1100 (specified range)

MPa

Yield Strength 0.2% Proof (quenched and tempered, over 40 to 100 mm)

650 (minimum)

MPa

Elongation in 50 mm (quenched and tempered, over 40 to 100 mm)

12 (minimum)

Reduction of Area (quenched and tempered)

50 (typical minimum)

Charpy V-Notch Impact Energy at room temperature (quenched and tempered, per EN 10083-3)

35 (minimum)

Hardness (quenched and tempered, pre-hardened stock)

262 - 321 (typical range)

HBW

Modulus of Elasticity

205 (typical)

GPa

Mechanical Properties

Check the key mechanical properties and performance requirements of AS 4140 Round Bar

ASTM A29 / A29M and ASTM A322 do not set mandatory mechanical properties for Alloy Steel 4140 Round Bar, so annealed and normalised values are typical figures. Where guaranteed properties are needed, EN 10083-3 for the equivalent grade 42CrMo4 provides mandatory minima in the quenched and tempered condition, tabulated by ruling section. For sections of 16-40 mm the requirement is a minimum yield of 750 MPa with a tensile range of 1000-1200 MPa and 11% minimum elongation. From 40 to 100 mm it falls to 650 MPa yield, 900-1100 MPa tensile and 12% elongation, and it continues to fall for larger ruling sections. Minimum Charpy V-notch energy at room temperature is 35 J across these bands.

Properties are set principally by the tempering temperature. Tempering near 540 deg C gives the upper strength range with lower ductility, while tempering near 680 deg C gives lower strength with markedly better elongation, reduction of area and impact energy.

Pre-hardened bar supplied at 262-321 HBW corresponds to roughly 900-1080 MPa tensile strength and represents a practical compromise between strength and machinability, since parts can be finished directly at this hardness.

Two tempering ranges should be avoided. Tempering between about 250 and 400 deg C causes tempered martensite embrittlement, and slow cooling from above 575 deg C can cause classical temper embrittlement in susceptible heats. Testing follows ASTM A370, ASTM E8 / E8M and ASTM E23.

Dimension / Sizes for Alloy Steel 4140 Round Bar

Dimension / Size

Value

Unit

Diameter (available range)

10 - 600

Standard Length

3 - 6

Custom Length

Cut to length on request

Diameter Tolerance (hot-rolled)

Per ASTM A29 / A29M

Diameter Tolerance (cold-finished)

Per ASTM A108, h9 / h10 / h11 or as agreed

Length Tolerance

Per ASTM A29 / A29M or as agreed

Straightness Tolerance

Per ASTM A29 / A29M or as agreed

End Condition

Square cut, saw cut, chamfered or as ordered

Surface Finish

Hot-rolled black, peeled, rough turned, cold-drawn bright, turned ground and polished

Cut-to-Length Availability

Available

Dimensional Standard

ASTM A29 / A29M and ASTM A108

Dimensions & Sizes

Explore available diameters, lengths, and dimensional requirements for AS 4140 Round Bar

Pricing for Alloy Steel 4140 Round Bar

Round Bar Prices are generally quoted per kilograms or meters tonnes and can fluctuate with the global raw material and market prices. The final price will depend on a variety of factors, including the grade size, diameter, length, surface finish, the quantity and whether the bars are cut to length or in standard lengths.

For smaller quantities, we can also quote per metre or per piece basis once the required dimensions have been confirmed. Container-loads or orders that are larger in size are typically priced per tonne, based upon the specifications required and the supply conditions.

Please provide your desired dimensions, grades, length number, and end for a current quote including the lead time applicable and details for certification.

Pricing

Get current Alloy Steel 4140 Round Bar pricing based on size, quantity, grade, finish, and delivery requirements.

Why Choose Us

Euro Steel Bars is an international distributor, stockist and exporter of stainless round steel bars that cover carbon, stainless alloy, special grades. We stock a variety of sizes and grades. We guarantee every order with mill test certificates as well as full quality-assurance documentation. Our name speaks to our roots: European-sourced materials that is backed by the certificates and rigor that buyers from Asia as well as the Gulf and Africa are looking for.

Each bar we deliver is accompanied by EN 10204 3.1 mill test certificates as well as complete documentation of quality, so what you receive corresponds to what’s written in the documents. We carry a selection of sizes and grades ready for transport, and cut length upon the request of customers, which results in quicker lead times, whether you’re ordering just a one-off spec or a complete project tonnage.

We operate an actual wholesale business that is that is supported with an internationally-operated supply chain therefore we are able to serve fabricators sourcing one grade the same way in the same way as an EPC contractor who is placing a large order. Our clients include manufacturers, fabricators EPC construction companies, engineers oil and gas projects as well as construction companies. we design our inventory as well as documentation to show what buyers need to bring projects forward.

Our customers trust us across Qatar, Oman, Bahrain, Kuwait, Jordan, Malaysia, Singapore, Thailand, Taiwan, Turkey, Italy and South Africa. If you’re looking to source an Gulf energy project, or a construction project within Southeast Asia, you get the same quality of certified material, the exact documentation, and the exact delivery procedure.

Frequently Asked Questions

Everything you should be aware of regarding Alloy Steel 4140 Round Bar from the grade and standards internationally, to the available sizes and finishes, requirements for manufacturing and application. This section will help buyers examine specifications and options for supply prior to making an inquiry or requesting a quote.

What is Alloy Steel 4140 Round Bar?

It is a solid cylindrical bar made from low-alloy chromium-molybdenum steel AISI/SAE 4140 (UNS G41400), containing 0.38-0.43% carbon with about 1% chromium and 0.2% molybdenum. It is one of the most widely used engineering steels, chosen for its deep hardening, its high strength after quenching and tempering, and the fact that it can be bought pre-hardened and machined straight away.

What standard does Alloy Steel 4140 Round Bar comply with?

General requirements are covered by ASTM A29 / A29M, hot-wrought alloy steel bar by ASTM A322 and cold-finished bar by ASTM A108, with composition also listed in SAE J404. In Europe the equivalent grade 42CrMo4 is covered by EN 10083-3, which does impose mandatory mechanical minima by ruling section. Bolting material of similar chemistry is covered by ASTM A193 Grade B7.

What are the equivalent grades of Alloy Steel 4140?

The recognised equivalents are 42CrMo4 (1.7225) to EN 10083-3 and ISO 683-2 in Europe, SCM440 to JIS G4105 in Japan, 42CrMo to GB/T 3077 in China, SCM440 to KS D 3867 in South Korea and 708M40 under the superseded BS 970 in the United Kingdom. The UNS designation is G41400.

What does pre-hardened 4140 bar mean?

Pre-hardened bar has already been quenched and tempered by the mill, usually to a hardness of 262-321 HBW, which corresponds to roughly 900-1080 MPa tensile strength. This allows components to be machined directly to final size without further heat treatment, avoiding the distortion, scale and dimensional change that heat treating a finished part would cause. Most shafting, tooling plate and fixture stock is held this way.

What are the key mechanical properties of 4140?

In the quenched and tempered condition EN 10083-3 requires, for the equivalent 42CrMo4 in sections of 16-40 mm, a minimum yield strength of 750 MPa, a tensile range of 1000-1200 MPa and 11% minimum elongation. From 40 to 100 mm the figures are 650 MPa yield, 900-1100 MPa tensile and 12% elongation, with 35 J minimum Charpy energy at room temperature. Pre-hardened stock at 262-321 HBW is a common supply condition.

Can Alloy Steel 4140 be welded?

It can, but with careful control. The carbon equivalent of about 0.75 makes the heat-affected zone hard and susceptible to hydrogen cracking. Successful welding requires preheat of typically 250-350 deg C, low-hydrogen consumables, controlled interpass temperature and post-weld heat treatment, usually a temper below the original tempering temperature. Where extensive welding is planned, grade 4130 is a better selection.

Can 4140 be nitrided or induction hardened?

Yes to both. Nitriding at 500-530 deg C produces a hard, wear-resistant case of about 600-650 HV with no quench distortion, and the chromium and molybdenum content makes the grade a good nitriding steel. Induction and flame hardening can produce a surface hardness of about 55-58 HRC. Both processes are normally applied to material already in the quenched and tempered condition.

What sizes and finishes are available?

Round bar is generally available from about 10 mm to 600 mm diameter in 3 to 6 m lengths, with larger forged rounds and blocks produced to order. Finishes include hot-rolled black, peeled, rough turned, cold-drawn bright and turned, ground and polished. Cut-to-length service is offered, and dimensional tolerances follow ASTM A29 / A29M for hot-rolled or ASTM A108 for cold-finished bar.

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Alloy Steel 4140 Round Bar

Country of Origin:

Material Type:

UNS Number:

Wr. No.:

MTC Available:

Product Description for Alloy Steel 4140 Round Bar

Common Applications of Alloy Steel 4140 Round Bar

International Equivalent Grade for AS 4140 Round Bar

Technical Specification for Alloy Steel 4140 Round Bar

Chemical Composition for Alloy Steel 4140 Round Bar

Mechanical Properties for Alloy Steel 4140 Round Bar

Dimension / Sizes for Alloy Steel 4140 Round Bar

Pricing for Alloy Steel 4140 Round Bar

Why Choose Us

Frequently Asked Questions

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Technical Specification

Chemical Composition

Mechanical Properties

Dimensions & Sizes

Pricing