Overview
Black square and rectangular tubes are cold-formed steel profiles widely used in industrial and construction applications. Their hollow cross-sections provide structural efficiency while minimizing weight. The black oxide coating enhances corrosion resistance and aesthetics, making them suitable for both functional and decorative purposes. These tubes are manufactured through high-frequency welding or seamless processes, with common materials including carbon steel grades like Q235 and Q345. Standard specifications adhere to GB/T 6728 (China) or ASTM A500 (international), ensuring dimensional accuracy and mechanical performance.
Structure and Working Principle
The tubes derive their strength from geometric rigidity—square and rectangular shapes distribute load evenly across edges. Wall thickness (ranging from 1.2mm to 20mm) and corner radii are critical design parameters affecting load-bearing capacity. In structural applications, they function as columns, beams, or trusses, transferring forces through their longitudinal axes. The hollow interior allows for utility routing (e.g., electrical conduits) or reduced material costs without compromising strength.
Key Features
1. **Durability**: Carbon steel provides tensile strength up to 500MPa, suitable for heavy-duty use. 2. **Corrosion Resistance**: The black oxide layer offers moderate protection against rust, though additional coatings (e.g., galvanization) may be required for harsh environments. 3. **Fabrication Flexibility**: Easily cut, welded, or drilled to fit custom designs. Standard sizes range from 20×20mm to 400×400mm for square tubes and 20×30mm to 300×600mm for rectangular variants. Tolerance levels typically conform to ±0.5mm for precision applications.
Application Areas
- **Construction**: Scaffolding, steel frameworks, and roof trusses. - **Machinery**: Conveyor systems, agricultural equipment frames. - **Furniture**: Modern shelving, table bases, and exhibition stands. - **Transportation**: Truck trailers and railcar components. Their modularity also supports DIY projects and temporary structures due to quick assembly/disassembly.
Maintenance and Precautions
Regular inspection for rust spots or structural deformities is recommended. Surface scratches may compromise the oxide layer—apply touch-up paint if exposed. During welding, preheat thick sections (>6mm) to prevent cracking. Store tubes horizontally on padded surfaces to avoid bending. For outdoor use, consider powder coating to extend service life.
B2B Procurement Guide
1. **Volume Discounts**: Orders exceeding 10 tons often qualify for 5–10% price reductions. 2. **Certifications**: Request mill test reports (MTRs) verifying chemical composition and mechanical properties. 3. **Logistics**: Confirm loading capacity with suppliers; standard 40-foot containers hold ~25–28 tons. Leading manufacturers include Baowu Steel (China), Nippon Steel (Japan), and ArcelorMittal (EU/US). Sample testing for dimensional accuracy is advised before bulk purchases.
Related Manufacturers
- 主营：[]
- 主营：花纹钢板、热轧碳钢板
- 主营：[]
- 主营：角钢、H型钢、槽钢、镀锌方管、方管、镀锌H型钢、钢板、镀锌钢板、工字钢、镀锌槽钢、镀锌角钢、c型钢、彩钢瓦、楼承板、镀锌圆管、镀锌钢管、预埋件、地脚螺栓、不锈钢天沟折件、钢结构预制加工、焊管、无缝管
- 主营：方管、冷拔无缝管、工字钢、方矩管、镀锌方管方矩管、角钢槽钢、H钢、扁钢、无缝管、Q345、Q235B、光亮管、黑退管、高压锅炉管、低温合金管、厚壁方管、美标汽车用管、欧标型钢
- 主营：[]
- 主营：[]
- 主营：[]
- 主营：彩钢板、中厚板、彩钢卷、热浸镀锌方矩管100x60、造船板、彩涂卷、桥梁钢板、彩涂钢板、船用钢板、锅炉容器板、拉森钢板桩、彩钢压型板、压力容器板
- 主营：异型管、水滴管、矩形管、健身器材管、办公桌架管、高频焊管、黑退扁方管、D型管、家具管、休闲椅子管、平扁元管、培训桌椅管、方管、升降桌管、光亮圆管、T型管、凹槽管、办公桌子脚管、三角管、汽车座椅管、家具椅子管、桌面支撑管、坐椅支撑管、椅子管
- 主营：钢板、圆钢、方管、方矩管、H型钢、角钢、工字钢、槽钢、焊管、无缝管
- 主营：角钢、槽钢、H型钢、螺纹钢、方管、镀锌管、钢板
- 主营：高压锅炉管、无缝方管、异型管、无缝方矩管、螺旋管、镀锌花纹板、厚壁无缝钢管零切
- 主营：工字钢、H型钢、钢板、槽钢、角钢、镀锌钢管、不锈钢管、不锈钢板、无缝钢管、镀锌方管、镀锌角钢、镀锌槽钢、中厚板、卷板
- 主营：镀锌钢带、热镀锌带钢、冷硬钢管、黑退方矩管、异型钢管、锌铝镁管、黑退圆管、黑退钢管、镀锌钢管、镀锌方管、异形管、方镀锌管、黑退管、镀锌圆管、镀锌带钢、q235镀锌钢管、镀锌管、DN150镀锌钢管、Q235消防镀锌管、镀锌大棚管、锌铝镁钢管、光亮焊接管、方管圆管黑退管、热镀锌无缝钢管
- 主营：钢丝、钢筋网、方管、黑色方管、圆管、H型钢、槽钢
- 主营：不锈钢钢管、涂塑钢管、无缝钢管、方矩管、螺旋钢管、H型钢、角钢、槽钢、工字钢、不锈钢板、防腐钢管、合金钢管、热镀锌钢管、镀锌钢管、高压锅炉管、不锈钢角钢、不锈钢槽钢、不锈钢装饰管、钢板、异形钢管、轨道钢、精密钢管、法兰、弯头大小头、注浆管
- 主营：镀锌钢管、焊接钢管、方管、无缝钢管、角钢、钢板、槽钢、球墨铸铁管
- 主营：镀锌管、钢板加工、焊接管、方矩管、镀锌方管、镀锌扁钢、无缝钢管、中厚板、角钢、槽钢、工字钢、镀锌板、螺旋管
- 主营：法兰、弯头、三通、异径管、大小头、人孔、封头、支吊架、管托、沟槽管件、防水套管、补偿器、高压承插管件、橡胶软接头、防腐钢管、保温钢管、镀锌钢管、方管
- 主营：螺旋管、铸铁管、抗震支架、方矩管、镀锌矩管、镀锌钢管、无缝钢管、涂塑钢管、加厚热镀管、钢塑复合管、汇津源钢铁、正大热镀管、不锈钢给水管、消防给水管件、热镀锌钢管
- 主营：楼承板、彩钢瓦、阳光瓦、花纹板、免拆模板、支撑圆管、镀锌方管、花纹钢板、管道配件、精密钢管、抗压钢板、支架配件、车库大棚、厂房托架、金属管材、支撑骨架、方形钢管、冷弯c型钢、国标z型钢、岩棉夹芯板、耐腐蚀檩条、泡沫夹芯板、剪折弯加工、彩钢波浪瓦、多规格模具
- 主营：黑色方管、起重机
- 主营：Q345B方管、厚壁方管、无缝方管、方矩管、小口径方管、大口径方管、镀锌方管、黑退方管、光亮方管、方通、方钢、焊管、镀锌管
- 主营：钢结构、镀锌方管、热镀锌槽钢、方矩管、角钢、镀锌管、镀锌圆管、工字钢、h型钢