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Carbon Steel Flat Bar – Hot Rolled & Cold Finished Steel Flat Bar Supplier
ASTM A36 | S235JR | S275JR | SS400 | Q235B | 1018 | Custom Sizes & Processing
Carbon Steel Flat Bar Supplier for Construction, Fabrication & Industrial Applications
Xi'an Dongmeng Group Co., Ltd. supplies carbon steel flat bars for structural fabrication, machinery manufacturing, steel construction, equipment production and industrial distribution.
Our product range includes hot rolled carbon steel flat bars, cold finished steel flat bars, mild steel flat bars and galvanized steel flat bars, with material grades and processing options selected according to project requirements.
Available material options include ASTM A36, S235JR, S275JR, SS400, Q235B and selected carbon steel machining grades such as 1018 and 1045.
Dongmeng Group supports bulk procurement, cut-to-length processing, customized fabrication, material traceability, mill test certificates and export packaging.
Whether you require standard mild steel flat bars for fabrication or project-specific steel flats with defined tolerances and inspection requirements, we can assist with technical specifications and international sourcing.
Request a Quote | Download Technical Specifications | Send Your Material List
What Is Carbon Steel Flat Bar?
Carbon steel flat bar is a solid steel product with a rectangular cross-section, manufactured in straight lengths for structural, mechanical and general fabrication applications.
It is commonly referred to as:
Mild Steel Flat Bar
Flat Steel Bar
Hot Rolled Steel Flat Bar
Carbon Steel Flat Stock
Rectangular Steel Bar
Steel Flat Strip
Carbon steel flat bars are widely used for brackets, supports, reinforcement members, base components, machinery parts and welded assemblies.
Unlike structural beams or channels, flat bars have a simple rectangular geometry, making them suitable for cutting, drilling, bending, welding and further machining.
Important: Hot-rolled flat bars, cold-finished flat bars and rectangular strips cut from steel plate are not necessarily interchangeable. Manufacturing route, edge condition, dimensions, tolerances and material documentation should be specified for the intended application.
Carbon Steel Flat Bar – Quick Specifications
| Item | Specifications |
| Product Name | Carbon Steel Flat Bar |
| Material Standards | ASTM A36/A36M, EN 10025-2, JIS G3101, GB/T 700; ASTM A108 for applicable cold-finished grades |
| Material Grades | A36, S235JR, S275JR, SS400, Q235B, 1018, 1045 |
| Material Type | Carbon Structural Steel / Mild Steel / Carbon Steel for Machining |
| Manufacturing Process | Hot Rolled, Cold Finished; Plate-Cut Flats on Request |
| Delivery & Surface | As-Rolled, Cold Finished, Pickled or Galvanized, as applicable |
| Indicative Size Range | Thickness 3–30 mm; Width 10–200 mm; Standard and Custom Lengths |
| Inspection & Documents | Dimensional Inspection, MTC, EN 10204 3.1 When Specified, Optional Third-Party Inspection |
Dimensions are indicative sourcing ranges, not a guaranteed stock list. Actual grade, size, manufacturing route and availability must be confirmed before ordering.
Carbon Steel Flat Bar Grades & Material Standards
Different steel grades offer different combinations of strength, weldability, machinability and processing characteristics.
Dongmeng Group helps buyers select appropriate grades based on engineering drawings, required product specifications and end-use conditions.
Common Material Grades
| Steel Grade | Standard / Grade System | Characteristics | Typical Applications |
| ASTM A36 | ASTM A36/A36M | General-purpose structural carbon steel | Frames, supports, brackets |
| S235JR | EN 10025-2 | Weldable non-alloy structural steel | General structural fabrication |
| S275JR | EN 10025-2 | Higher specified strength than S235JR | Structural members, machinery frames |
| SS400 | JIS G3101 | General-purpose structural steel | Fabrication, industrial components |
| Q235B | GB/T 700 | General carbon structural steel | Construction and welded structures |
| AISI/SAE 1018 | Specified carbon steel bar requirements | Low-carbon machining and fabrication grade | Shafts, machined components, fixtures |
| AISI/SAE 1045 | Specified carbon steel bar requirements | Medium-carbon grade suitable for selected machining and heat-treatment applications | Machinery components and wear-related parts |
Higher-strength alternatives: S355 structural grades and Q355B may also be considered for projects requiring higher strength. These should be quoted separately under their applicable material specifications.
How to Choose the Right Steel Grade
ASTM A36 Flat Bar
A commonly specified option for structural fabrication, base supports, brackets and general construction.
S235JR Flat Bar
Suitable for projects specifying European structural steel requirements under EN 10025-2.
SS400 Flat Bar
Frequently specified in projects using Japanese structural steel standards.
1018 Carbon Steel Flat Bar
Often selected for components requiring machining and more controlled dimensional conditions, particularly when supplied as cold-finished material.
1045 Carbon Steel Flat Bar
May be suitable for machinery components requiring medium-carbon steel properties. Heat treatment and welding procedures require additional evaluation.
Material grades from different standards should not be treated as automatically equivalent. Any substitution must be reviewed against chemical composition, mechanical properties, thickness limitations and project requirements.
Carbon Steel Flat Bar Manufacturing Types
1. Hot Rolled Carbon Steel Flat Bar
Hot rolled flat bars are produced through rolling at elevated temperatures to form rectangular steel sections.
They are commonly selected for construction and general-purpose fabrication.
Key Features
Suitable for a broad range of structural and fabrication applications
Economical for bulk material sourcing
Can be cut, drilled and welded using suitable procedures
Typically supplied with an as-rolled surface
May have mill scale and rounded edges
Typical Applications: Steel frames, reinforcement bars, support brackets, fabrication components and construction accessories.
2. Cold Finished Carbon Steel Flat Bar
Cold finished steel flat bars undergo finishing processes that improve dimensional control and surface condition relative to general hot-rolled material.
The exact production process may include cold drawing or other cold-finishing operations.
Key Features
More controlled dimensional accuracy
Improved surface finish options
Suitable for selected machining operations
Useful for precision components and assemblies
Mechanical properties depend on grade and finishing condition
Typical Applications: Machined components, fixtures, precision supports, equipment parts and industrial manufacturing.
3. Galvanized Carbon Steel Flat Bar
Galvanized flat bars have a zinc coating intended to provide corrosion protection.
Hot-dip galvanizing may be specified for suitable structural flat bar components, including fabricated parts.
Key Features
Zinc coating for corrosion protection
Suitable for many outdoor installations
Can be incorporated into railings, fencing and supports
Coating requirements can be defined according to the project
Typical Applications: Outdoor frames, fencing systems, brackets, electrical supports and infrastructure accessories.
Coating thickness, galvanizing standard, fabrication sequence and post-treatment requirements should be agreed before production.
4. Custom Cut Carbon Steel Flat Stock
Rectangular flat stock can also be produced by cutting suitable steel plate or strip to the specified width and length.
This option may be considered for non-standard sizes.
It should be identified separately from directly hot-rolled flat bar because edge geometry, tolerances and material certification can differ.
Carbon Steel Flat Bar Sizes & Dimensions
Dongmeng Group supports standard dimensional configurations and project-specific enquiries for carbon steel flat bars.
General Product Specifications
| Parameter | Typical Enquiry Options |
| Thickness | 3–30 mm; other sizes on request |
| Width | 10–200 mm; wider flats subject to confirmation |
| Length | 3 m, 6 m, 12 m or custom cut lengths |
| Cross Section | Solid rectangular |
| Edges | As-Rolled, Sheared or Machined, according to product route |
| Straightness | Applicable product standard or agreed tolerance |
| Surface | Mill Finish, Cleaned, Coated or Galvanized |
| Processing | Cutting, Drilling, Punching, Bending, Machining |
| Packaging | Steel Bundles, Protective Wrapping or Custom Export Packaging |
Common Carbon Steel Flat Bar Size & Theoretical Weight Table
| Width × Thickness (mm) | Approx. Weight (kg/m) |
| 20 × 3 | 0.471 |
| 25 × 3 | 0.589 |
| 30 × 5 | 1.178 |
| 40 × 5 | 1.57 |
| 50 × 6 | 2.355 |
| 60 × 8 | 3.768 |
| 75 × 10 | 5.888 |
| 100 × 10 | 7.85 |
| 120 × 12 | 11.304 |
| 150 × 12 | 14.13 |
| 200 × 20 | 31.4 |
These are illustrative dimensional combinations, not confirmed inventory items. Theoretical weights assume a nominal density of 7,850 kg/m³ and a rectangular cross-section. Actual delivered weight varies with dimensional tolerances and product geometry.
Carbon Steel Flat Bar Weight Calculation
For estimating material quantities and shipping weight:
Weight (kg/m) = Width (mm) × Thickness (mm) × 0.00785
Example:
A 50 × 6 mm carbon steel flat bar has an approximate theoretical weight of:
50 × 6 × 0.00785 = 2.355 kg/m
For a 6-meter length:
2.355 × 6 = 14.13 kg per piece
Final invoicing weight may be based on actual weight or an agreed theoretical-weight method, as stated in the purchase contract.
Carbon Steel Flat Bar Standards & Dimensional Tolerances
Carbon steel flat bars should be ordered using both an applicable material standard and appropriate dimensional requirements.
| Standard | Scope / Application |
| ASTM A36/A36M | Structural carbon steel material requirements |
| ASTM A6/A6M | General requirements for applicable rolled structural steel bars and products |
| ASTM A108 | Applicable cold-finished carbon and alloy steel bars |
| EN 10025-2 | Technical delivery conditions for non-alloy structural steels |
| EN 10058 | Dimensions and dimensional tolerances for hot-rolled flat steel bars and wide flats |
| JIS G3101 | General structural rolled steel grades including SS400 |
| GB/T 700 | Carbon structural steel material grades including Q235 |
For example, a European structural flat bar may be specified using S235JR according to EN 10025-2, with dimensions and tolerances to EN 10058.
The material standard establishes requirements for the steel grade, while the dimensional standard establishes the relevant geometric requirements.
Tighter dimensional tolerances, specific straightness requirements, edge conditions and surface finish requirements should be reviewed separately before quotation.
Carbon Steel Flat Bar Processing & Customization
Dongmeng Group supports custom processing requirements to reduce downstream handling and preparation for industrial buyers.
Cut-to-Length Services
Flat bars can be supplied in project-specified lengths to support assembly, fabrication and installation.
Drilling & Punching
Hole patterns, slot dimensions and installation openings can be reviewed against customer drawings.
Bending & Forming
Suitable grades and dimensions can be processed into specified forms, subject to bend radius and material requirements.
Welding & Fabrication
Flat steel components can be incorporated into welded structures and assemblies using approved welding procedures.
Surface Treatment
Available enquiry options may include:
As-Rolled Finish
Surface Cleaning
Shot Blasting
Primer or Paint Coating
Hot-Dip Galvanizing
OEM & Drawing-Based Processing
Customers can submit PDF, DWG or other suitable technical drawings for customized components.
Processing feasibility, dimensional tolerance, minimum order quantity and inspection requirements are confirmed during technical review.
Carbon Steel Flat Bar Applications
Structural Steel Fabrication
Flat bars are used to manufacture brackets, reinforcement components, support members and connection details in steel structures.
Machinery Manufacturing
Selected grades can be used for machine components, mounting plates, fixtures and mechanical fabrication.
Fencing & Metal Fabrication
Flat steel bars are commonly incorporated into gates, fences, railing supports and welded metal assemblies.
Industrial Equipment
Flat bars can serve as mounting members, structural supports and fabrication materials for industrial equipment.
Electrical & Utility Structures
Appropriately designed steel flat bars are used in mounting brackets, equipment support systems and certain utility structures. Electrical grounding applications require separate assessment of conductivity, corrosion protection and applicable electrical standards.
Infrastructure & Construction
Flat bars can be used in secondary structures, installation supports, platforms, access systems and fabricated construction components.
Actual structural suitability must be determined through the applicable engineering design and project specifications.
Quality Control & Material Traceability
For international B2B procurement, material identification and inspection documentation are essential to consistent product quality.
Dongmeng Group supports documented material sourcing and inspection requirements based on the applicable product standard.
Material Verification
Steel grade and applicable specification
Chemical composition documentation
Mechanical test results where required
Heat number identification and traceability
Dimensional Inspection
Width and thickness
Length
Straightness
Edge condition
Surface appearance
Material Test Certificates
Mill Test Certificates can be arranged according to the purchase requirements.
EN 10204 Type 3.1 inspection certificates may be specified where available and agreed before order placement. These are issued by the producing manufacturer's authorized inspection representative independently of production.
Third-Party Inspection
Independent inspection arrangements can be discussed for projects requiring additional verification.
Inspection scope, acceptance criteria and documentation should be defined in the purchasing specification.
Packaging & International Shipment
Carbon steel flat bars can be prepared for domestic or international transportation according to their size, surface condition and shipment method.
Packaging options include:
Steel strapped bundles
Protective wrapping where specified
Bundle identification tags
Suitable lifting and handling arrangements
Project-specific export packaging
Order quantities may be coordinated for steel distributors, fabricators, contractors and project buyers.
Shipment methods and commercial delivery terms are confirmed during quotation.
Why Choose Dongmeng Group as Your Carbon Steel Flat Bar Supplier?
1. Multiple Steel Grade Options
Support for international carbon steel grade systems including ASTM, EN, JIS and GB/T.
2. Standard & Customized Specifications
Assistance with standard steel flats, non-standard lengths and drawing-based processing requirements.
3. Project-Based Material Sourcing
Support for distributors, equipment manufacturers, steel fabricators and construction projects requiring multiple product specifications.
4. Inspection & Traceability Support
Material certificates, dimensional verification and third-party inspection arrangements where specified.
5. International Procurement Coordination
Assistance with material lists, technical confirmation, export packaging and shipment documentation.
Frequently Asked Questions About Carbon Steel Flat Bar
Q1. What is carbon steel flat bar used for?
Carbon steel flat bar is used for structural brackets, welded frames, reinforcement components, machine parts, equipment supports, metal gates and general fabrication. The appropriate grade depends on the required strength, processing method and service environment.
Q2. What is the difference between hot rolled and cold finished flat bar?
Hot rolled flat bars are commonly used in structural and general fabrication applications. Cold finished flat bars typically provide improved dimensional control and surface finish, making them useful for certain machining and precision applications.
Q3. What is ASTM A36 carbon steel flat bar?
ASTM A36 flat bar is a rectangular structural steel bar supplied to ASTM A36/A36M material requirements. It is commonly specified for general structural and fabrication applications where suitable welding, bolting or other connection methods are used.
Q4. Are ASTM A36 and SS400 flat bars the same?
No. ASTM A36 and JIS SS400 are different standard designations. Although they may be considered for similar applications, they have different specification requirements. Any material substitution must be approved against the project specification.
Q5. Can carbon steel flat bars be galvanized?
Yes. Suitable carbon steel flat bars can be galvanized to improve corrosion protection. Hot-dip galvanizing requirements should specify the coating standard, minimum coating requirements and intended environment.
Q6. What sizes of carbon steel flat bar are available?
Common enquiry sizes include widths from 10 to 200 mm and thicknesses from 3 to 30 mm. Availability varies by material grade, manufacturing process and dimensional standard. Other sizes can be reviewed upon request.
Q7. Can you supply custom-cut carbon steel flat bars?
Yes. Dongmeng Group supports enquiries for custom-length flat bars and further processing based on project drawings. Processing capability and tolerances are confirmed before quotation.
Q8. What standards apply to carbon steel flat bars?
Common standards include ASTM A36/A36M, EN 10025-2, JIS G3101 and GB/T 700 for suitable material grades. EN 10058 addresses the dimensions and tolerances of hot-rolled flat steel bars, while ASTM A108 applies to certain cold-finished steel bars.
Q9. What is the difference between flat bar and plate-cut flat stock?
A hot-rolled flat bar is produced directly in a rolling process. Plate-cut flat stock is produced by cutting steel plate or strip into rectangular pieces. Their edge conditions, production tolerances, surface characteristics and documentation requirements may differ.
Q10. Can you provide an EN 10204 3.1 certificate?
EN 10204 Type 3.1 certification can be requested where applicable and available from the producing manufacturer. Buyers should specify the required certificate type and traceability requirements before confirming the order.
Q11. Is carbon steel flat bar suitable for welding?
Many structural carbon steel grades are commonly welded using suitable procedures. However, weldability depends on material chemistry, thickness, restraint, welding process and service conditions. Medium-carbon grades such as 1045 may require additional welding precautions.
Q12. How do you calculate the weight of carbon steel flat bar?
For a rectangular flat bar, the approximate theoretical weight in kilograms per meter equals width in millimeters multiplied by thickness in millimeters multiplied by 0.00785.
Q13. What is the minimum order quantity for carbon steel flat bars?
Minimum order quantity depends on the steel grade, dimensions, processing requirements and whether the material can be sourced from available stock. Please send your specification and required quantity for confirmation.
Q14. Can you supply steel flat bars for large construction projects?
Dongmeng Group supports project-based procurement enquiries, including multiple sizes, material grades, customized lengths and agreed inspection requirements.
Q15. What information is needed for a carbon steel flat bar quotation?
Please provide the material grade, manufacturing type, width, thickness, length, quantity, surface treatment, processing requirements, inspection documents and delivery destination. Drawings are recommended for customized components.
Request a Quote for Carbon Steel Flat Bar
Send Us Your Steel Flat Bar Specifications
Looking for a reliable carbon steel flat bar supplier for your next project?
Xi'an Dongmeng Group Co., Ltd. welcomes enquiries from steel distributors, fabrication companies, machinery manufacturers, EPC contractors and international purchasing teams.
Please include the following information in your enquiry:
| RFQ Information | Customer Requirements |
| Product | Carbon Steel Flat Bar |
| Material Grade | A36 / S235JR / SS400 / Q235B / 1018 / Other |
| Manufacturing Route | Hot Rolled / Cold Finished / Other |
| Dimensions | Width × Thickness × Length |
| Quantity | Pieces / Metric Tons |
| Surface Finish | As-Rolled / Galvanized / Other |
| Processing | Cutting / Drilling / Bending / Machining |
| Inspection | MTC / EN 10204 3.1 / Third-Party Inspection |
| Delivery Destination | Country / Port |
| Commercial Terms | EXW / FOB / CFR / CIF / Other |
Request a Quotation | Submit Your Drawings | Contact Our Sales Team
Office Information
Xi'an Dongmeng Group Co., Ltd.
Phone: +86 157 6921 4734
Email: office@dongmjd.com
WhatsApp: Dong, +86 157 6921 4734
Office Address: Room 4107, Runfeng Building, Sanqiao New Street, Weiyang District, Xi'an City, Shaanxi Province, China.
Dongmeng Group – Carbon Steel Flat Bar Supply, Custom Processing & International Procurement Support.
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