Product Description

We specialize in supplying high-quality hot-rolled structural steel round bars, precisely covering low, medium, and high carbon grades. Tailored to global industrial procurement needs, we optimize the production of commonly demanded sizes: 6mm, 10mm, and 30mm black steel bars. Manufactured through high-temperature continuous rolling, the bars feature a dense microstructure, stable mechanical properties, and a natural black scale surface. They offer excellent weldability, machinability, and heat treatment responsiveness, making them ideal base materials for machinery manufacturing, construction engineering, and hardware processing.

Product Specifications

Product Type: Hot-rolled Structural Steel Round Bar / Black Steel Bar

Key Diameters: 6mm, 10mm, 30mm (Other sizes available upon request)

Carbon Grade Classification:

▸ Low Carbon (≤0.25%): Excellent weldability & ductility

▸ Medium Carbon (0.25%-0.60%): Balanced strength & toughness, ideal for quenching & tempering

▸ High Carbon (≥0.60%): High hardness & wear resistance, suitable for heat treatment

Typical Grades: Q195/Q235, 20#/45#/1045/S45C, 65Mn/1095, etc. (Supply available per ASTM/GB/JIS/DIN/EN standards)

Surface Finish: Hot-rolled black scale (natural oxide layer, ideal for machining & subsequent anti-rust/coating processes)

Standard Lengths: 6m / 9m / 12m (Custom cutting available)

Standards: GB/T 702, ASTM A29/A500, JIS G4051, DIN EN 10050, etc.

Key Advantages

Complete Carbon Grades for Precise Matching

Full coverage of low/medium/high carbon series to meet different requirements for welded structures, mechanical transmission parts, springs, and fasteners.

Hot-Rolled Process, Dense Microstructure

High-temperature rolling eliminates internal stresses, refines grains, ensures stable tensile/yield strength, and delivers excellent concentricity & straightness.

Black Scale Surface, Machining-Friendly

Natural oxide layer prevents storage rust, ensures smooth cutting/milling/drilling, and produces clean chip breakage.

Strict Tolerances & Batch Consistency

Diameter tolerances strictly controlled (typically ±0.4~±1.0mm, upgradeable). Chemical composition & mechanical properties tested batch by batch.

Stocked Sizes, Fast Delivery

6mm/10mm/30mm and other popular sizes kept in stock. Supports quick dispatch and custom cutting, shortening your production lead time.

Applications

Construction steel structures & engineering machinery parts

Automotive chassis components, drive shafts, connecting rods

Fasteners (bolts, nuts, rivets) & standard parts

Hardware tools, mold inserts, fixture guide rails

Spring washers, bearing races, wear-resistant pins

Agricultural machinery, marine fittings & general equipment

Why Choose Us?

Specialized in Carbon Steel Round Bars

Years of focus on low/medium/high carbon hot-rolled bars. We understand heat treatment & machining characteristics of different carbon grades and provide precise material selection advice.

Full-Process Quality Control

Strict control from steelmaking composition, rolling temperature curves to final dimensional inspection. ISO-certified system with optional third-party testing reports.

Flexible Customization

Custom length cutting, chamfering, anti-rust oil coating, and flexible packaging (bundling/wooden crate/pallet) to perfectly match your production line.

Stable Supply Chain & Competitive Pricing

Direct partnership with top mills, sufficient capacity, and transparent pricing ensure cost efficiency and long-term supply stability.

Proven Export Experience

Familiar with international shipping standards & compliance. Experienced in customs clearance, inspection certificates, COO, and SGS/Intertek inspections for smooth global delivery.

FAQ

Q1: What material grades are available for 6mm/10mm/30mm black bars?

A: Low carbon: Q195/Q235/1008/1010; Medium carbon: 45#/1045/S45C/AISI 1035; High carbon: 65Mn/1095/SAE 1080. We recommend the optimal grade based on your application.

Q2: Does the black scale surface affect machining or welding?

A: No. The natural oxide layer aids chip evacuation during machining. For welding, simple grinding or pickling is sufficient. Bright/polished finishes or shot blasting are also available upon request.

Q3: What is the typical diameter tolerance?

A: Standard hot-rolled tolerances: ±0.4mm (6mm) / ±0.5mm (10mm) / ±0.8mm (30mm). Tighter tolerances can be achieved via cold drawing or precision rolling.

Q4: Do you offer custom length cutting per drawings?

A: Yes. Laser/saw cutting to custom lengths with ±1~2mm tolerance. End chamfering and deburring services are also available.

Q5: Can you provide material certificates or test reports?

A: Mill Test Certificates (MTC) are provided with every shipment. Third-party testing (SGS/CTI, etc.) for chemical composition and mechanical properties is available upon request.

Q6: What is the MOQ and lead time?

A: Standard grades MOQ: 5~10 tons per size. In-stock items ship in 3-7 days. Custom cutting or special grades take 10-15 days, confirmed per order.

Q7: How is packaging designed to prevent rust & damage?

A: Standard: anti-rust paper + steel strapping + moisture-proof pallets. Export options: wooden crates, vacuum anti-rust film, or seaworthy bundles. Fully compliant with ocean freight anti-corrosion standards.