4140 Round Bar

AISI 4140 Round Bar | Premium Alloy Steel Manufacturer & Supplier

AISI 4140 round bar is a chromium-molybdenum low-alloy steel known for its excellent strength, toughness, and wear resistance. As a through-hardening grade, 4140 is widely used in demanding engineering applications across oil and gas, automotive, aerospace, and heavy machinery sectors.

We are a professional manufacturer and supplier of 4140 steel bar with over 15 years of export experience. Our products are shipped to more than 50 countries worldwide, serving industries that demand reliable material performance and consistent quality.

Whether you require standard sizes or custom dimensions, we offer flexible solutions with full traceability and third-party inspection support. Our 4140 bars are manufactured under strict quality control to meet international standards including ASTM, AISI, SAE, DIN, and JIS specifications.

The precise chemical control ensures consistent hardenability, enabling reliable mechanical properties after heat treatment across various section sizes.

We follow a comprehensive and tightly controlled production process to ensure the highest quality 4140 alloy steel round bar:

Raw Material Selection – Premium scrap and alloying elements (Cr, Mo, Mn) are carefully selected.

Electric Arc Furnace (EAF) Melting – Primary melting to achieve the target liquid steel composition.

Ladle Refining Furnace (LF) – Fine-tuning of chemical composition and removal of impurities.

Vacuum Degassing (VD) – Removal of dissolved gases (hydrogen, oxygen, nitrogen) to improve internal soundness.

Continuous Casting / Ingot Casting – Casting into billets or ingots based on final product requirements.

Forging or Hot Rolling – Shaping round bars to specified diameters with precise dimensional control.

Heat Treatment – Annealing, normalizing, quenching, or tempering as per customer requirements.

Straightening & Cutting – Ensuring straightness and cutting to required lengths.

Surface Finishing – Peeling, turning, polishing, or grinding to achieve surface quality.

Final Inspection & Testing – Comprehensive dimensional, chemical, mechanical, and NDT inspection.

Our in-house heat treatment facility enables us to supply material in any condition required, from annealed for maximum machinability to quenched and tempered for high-strength applications.

Quality is the foundation of our manufacturing process. Every batch of 4140 round bar undergoes rigorous inspection to ensure compliance with applicable standards and customer specifications:

Inspection Capabilities:

Chemical Composition Analysis – Spectrometer testing per ASTM E415 / E1086

Mechanical Testing – Tensile, yield, elongation, reduction of area, and impact testing

Hardness Testing – Brinell, Rockwell, and Vickers hardness testing

Ultrasonic Testing (UT) – Internal defect detection per ASTM E114 / E587, Class C/C or D/D

Dimensional Inspection – Diameter, length, straightness, and surface quality verification

Macro/Micro Structure Examination – Grain size, inclusion rating, and microstructure analysis

Hydrogen Testing – For critical oil and gas applications

Third-Party Inspection:
We welcome and support third-party inspection by SGS, Bureau Veritas (BV), TUV, or any customer-nominated inspection agency.

Documentation:
Each shipment includes a complete Mill Test Certificate (MTC) providing full traceability from heat to finished product, including all test results. EN 10204 3.1 or 3.2 certification is available upon request.

Factory Facility: Advanced production lines with integrated EAF + LF + VD + continuous casting + forging/rolling capabilities.

Testing Laboratory: Fully equipped with spectrometers, universal testing machines, hardness testers, UT equipment, and metallographic microscopes.

Warehouse & Inventory: Large stock of standard sizes ready for immediate dispatch.

Packaging Line: Professional export packaging ensuring product safety during sea or land freight.

With 15+ years in the steel export industry, we have supplied AISI 4140 round bars to projects and clients across:

Oil & Gas Industry

Drill collars and tool joints for offshore drilling

Downhole tools and subsea connectors

Wellhead equipment and blowout preventers

Automotive & Transportation

Heavy-duty gears, pinions, and axles

Crankshafts and connecting rods

Torsion bars and suspension components

Aerospace & Defense

Structural forgings and aircraft components

Landing gear assemblies

High-strength fasteners and threaded components

General Engineering & Machinery

Hydraulic shafts and spindles

Mold bases and die holders

Machine tool components and industrial equipment

Fasteners & Bolting Industry

ASTM A320 L7 / L7M bolts and studs

High-strength nuts and threaded bars

Typical End-User Projects:

Offshore platform structural components – Southeast Asia

Mining equipment shafts – Australia

Automotive axle production lines – Europe

Pressure vessel bolting – Middle East oil refineries

Recommendation: Choose 4140 for cost-effective high-strength components in medium to heavy sections. Choose 4340 when superior toughness and deeper hardenability are required for very heavy sections.

What is the difference between 4140 round bar and 4140 steel plate?
Both share identical chemical composition. Round bars are typically used for turned components, shafts, gears, and fasteners, while plates are used for flat structural fabrication, brackets, and wear plates.

What is the minimum order quantity (MOQ)?
Our standard MOQ is 1 ton per size. However, we welcome trial orders of smaller quantities for new customers to verify our quality and service.

What is your typical lead time?
Standard lead time is 15–25 working days. For stock items in common diameters, we can ship within 3–5 working days. Large orders or special specifications may require longer lead times.

Can you provide custom sizes and lengths?
Yes. We support custom cutting to any length and can supply non-standard diameters upon request. Custom heat treatment and surface finishing are also available.

What certifications do you provide?
We provide Mill Test Certificates (MTC) with full traceability to the original heat. EN 10204 3.1 or 3.2 certification can be issued upon request. Our facility is ISO 9001:2015 certified.

Do you support third-party inspection?
Yes. We welcome inspections by SGS, BV, TUV, or any other accredited third-party inspection agency nominated by our customers.

What is the best heat treatment?
Oil quenching from 840–880°C followed by tempering at 550–650°C achieves the optimal balance of strength, toughness, and hardness. The specific tempering temperature depends on the target hardness. Annealing at 815–845°C provides maximum machinability.

Is AISI 4140 weldable?
Yes, but 4140 has higher carbon content (0.38–0.43%) than 4130, so preheating (300–500°F) and post-weld heat treatment (PWHT) are essential to avoid hydrogen cracking. It is not recommended for critical weld-fabricated structures.

What packaging do you use for export?
Our standard export packaging includes steel strapped bundles, wrapped in waterproof fabric, with plastic end caps on each bar to protect ends. Wooden cases, pallets, or crates are available upon request for added protection.

What is the hardness in annealed condition?
Typically 197–217 HB, which provides excellent machinability for subsequent finishing operations.

Can you supply 4140 bars with ultrasonic testing (UT) certification?
Yes. We offer UT testing per ASTM E114 / E587 standards, with Class C/C or D/D certification. Additional NDT methods such as magnetic particle inspection (MPI) are also available.

Do you provide machining services?
Yes. We support custom machining, including turning, drilling, threading, and grinding to customer drawings.

How do I request a quote?
Please provide your required diameter, length, quantity, delivery condition, surface finish, and any special certification requirements. We will respond with a competitive quote within 24 hours.

Looking for a reliable AISI 4140 steel bar supplier?
Contact us for:

1. 4140 round bar quotation
2. Latest AISI 4140 price, customized sizes, Heat treatment requirements
3. Technical support
4. We provide high-quality 4140 steel round bars for global industrial customers with competitive pricing, stable supply, and professional service.

Email:baohui@bhsteelpipe.com

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