Carbon Steel Flat Bar | Mild Steel Flat Bar (A36, 1018, 1045, Q235, SS400)

Huaxia Steel — Professional Carbon Steel Flat Bar Supplier
15+ years of experience | ISO 9001 & SGS Certified | Hot rolled & cold drawn | Cut-to-length | Global shipping

What is Carbon Steel Flat Bar?

Carbon steel flat bars are rectangular cross-section steel products with a width-to-thickness ratio typically between 1:1 and 5:1. They are versatile intermediate products used in fabrication, machining, forging, and structural applications. Huaxia Steel supplies carbon steel flat bars in hot-rolled, cold-drawn, and forged conditions, conforming to ASTM A36/A27, EN 10025, JIS G3101, and GB/T 702 standards, serving the construction, automotive, machinery, and tooling industries worldwide.

Available Grades & Standards

Chemical Composition & Mechanical Properties of Common Carbon Steel Flat Bar Grades

Grade	Standard	C%	Mn%	Yield (MPa)	Tensile (MPa)	Application
A36	ASTM A36	0.25–0.29	—	≥250	400–550	General structural
1018	ASTM A108	0.15–0.20	0.60–0.90	≥370	≥440	Machining / forging
1045	ASTM A108	0.43–0.50	0.60–0.90	≥355	≥600	High-strength shafts
Q235B	GB/T 700	0.12–0.20	0.30–0.67	≥235	375–500	General structural
Q345B	GB/T 1591	≤0.20	1.00–1.60	≥345	470–630	Heavy structural
SS400	JIS G3101	≤0.15	—	≥245	400–510	General structural
S235JR	EN 10025-2	≤0.17	≤1.40	≥235	360–510	EU standard structural
S355JR	EN 10025-2	≤0.22	≤1.60	≥355	470–630	EU high-strength

Dimensions & Specifications

Carbon Steel Flat Bar Size Range & Tolerances

Parameter	Hot Rolled Flat Bar	Cold Drawn Flat Bar
Thickness	3–60mm	5–50mm
Width	10–200mm	10–100mm
Length	3–12m	3–6m (random or fixed)
Thickness Tolerance	±0.3–1.0mm	±0.05–0.15mm
Width Tolerance	±0.5–1.5mm	±0.1–0.3mm
Surface Roughness	12.5µm (Ra)	3.2µm (Ra) or better
Standard	ASTM A36/A27, GB/T 702	ASTM A108, EN 10278

Manufacturing Process

Carbon steel flat bars are produced through multiple routes:

Hot Rolling (Most Common): Steel billets are heated to 1100–1250°C and passed through flat bar rolling mills with progressively reducing gaps. The process produces bars with a scaled surface and standard tolerances, suitable for structural and fabrication applications. Hot-rolled flat bars are the most economical option.

Cold Drawing: Hot-rolled flat bars are further processed at room temperature through a die to achieve tighter dimensional tolerances, improved surface finish (Ra 3.2µm or better), and enhanced mechanical properties through strain hardening. Cold-drawn bars are ideal for machining and precision applications.

Forging: For special sizes or grades, flat bars can be produced by open-die forging, offering superior internal quality and grain flow for critical applications.

Surface Finish & Treatment Options

Available surface conditions:
– Hot Rolled (Black): Mill finish with blue-grey oxide scale
– Hot Rolled, Pickled (HRP): Scale removed for clean surface
– Cold Drawn (Bright): Smooth, polished surface for precision use
– Hot-Dip Galvanized: Zinc coating for corrosion protection
– Polished: Mirror or satin finish for architectural/decorative use
– Chamfered Edges: Edges broken for safer handling and assembly

Common Applications

• Structural support brackets, cleats, gussets, and tie plates
• Machinery frames, base plates, and mounting rails
• Automotive suspension components, leaf springs, and shims
• Shipbuilding: keel bars, deck supports, and frame reinforcements
• Electrical grounding busbars and switchgear components
• Tool and die making: parallels, strips, and key stock
• Fence posts, gate frames, and security grilles
• Grating and walkway fabrication for industrial plants

Why Choose Huaxia Steel as Your Carbon Steel Flat Bar Supplier?

Factory-Direct Pricing

Eliminate middlemen. Our direct mill partnerships ensure competitive pricing on every order, from small prototype quantities to full container loads.

Certified Quality

Every shipment includes full mill test certificates (MTC/EN 10204 3.1). ISO 9001:2015 certified. Third-party SGS inspection available on request.

Custom Processing

Cut-to-size, precision slitting, bending, welding, galvanizing, and surface treatment services. We deliver material ready for your production line.

Fast Global Logistics

Efficient shipping to North America, Europe, Middle East, Southeast Asia, and beyond. Standard lead time 7–15 days for stock items.

Frequently Asked Questions

What is the difference between flat bar and plate?

The primary difference is the width-to-thickness ratio and manufacturing method. Flat bars are typically produced by hot rolling with width from 10–200mm and thickness from 3–60mm. Plates are rolled on plate mills with width up to 5000mm and thickness from 6–200mm. Flat bars are supplied in straight lengths; plates are supplied as flat sheets. Flat bars are preferred for machining and fabrication; plates for large structural components.

Can flat bars be bent or formed?

Yes, carbon steel flat bars can be bent using press brakes, ring rollers, or pyramid rollers. The minimum bend radius depends on thickness, grade, and bend direction (rolling direction vs. transverse). As a general rule, hot-rolled A36/Q235 flat bars can be bent to a minimum radius of 1.5× thickness for transverse bends.

What is cold drawn flat bar?

Cold drawn flat bar is produced by pulling hot-rolled bar through a die at room temperature. This process achieves tighter dimensional tolerances (±0.05mm), improved surface finish (Ra 3.2µm), higher yield strength (through strain hardening), and straighter bars. Cold drawn bars are the preferred choice for precision machining operations.

What is the standard length?

Standard lengths are 3m, 6m, and 12m for hot-rolled flat bars. Cold drawn bars typically come in 3m and 6m lengths. Random lengths between 2–7m are also commonly available. Custom cut lengths can be arranged.