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Shijiazhuang Faith Machinery Co.,Ltd’s carbon steel welded tube mill lines are engineered to produce welded carbon steel tubes that serve applications ranging from furniture frames and scaffolding to hydraulic cylinders and automotive components. By focusing on optimized weld seam quality, tight dimensional control, and efficient changeover, our carbon steel tube mills meet the rigorous demands of both small‐batch specialty producers and high‐volume manufacturers.
A carbon steel welded tube mill line typically consists of the following interconnected modules, each selected for handling common carbon steel strip grades (e.g., ASTM A527, EN 10130, or equivalent domestic standards):
Payoff/Coil Decoiler
Mandrel decoilers with hydraulic braking support strip coils up to 15 tons. Mandrel expansion systems grip inner diameters from 508 mm to 610 mm, ensuring secure strip handling.
The decoiler release tension arm, with load‐cell feedback, precisely maintains strip tension, minimizing strip flutter that could lead to seam misalignment.
Tension Leveling and Strip Conditioning
A tension leveler with 10–14 vertically oriented work rolls corrects residual camber and coil set. Adjustable hydraulic crown control ensures uniform pressure across the strip width (commonly 25 mm to 168 mm).
The leveling process improves strip flatness, directly influencing forming accuracy and weld seam alignment.
Forming Section
Progressive roll stands (usually 8 to 12 stands) gradually bend the strip from flat into a cylindrical shape. Each stand features matched upper and lower rolls, with roll surfaces hardened to resist wear from abrasive carbon steel strip.
Roll stands include manual or motorized gap adjustment. Motorized stands—driven by AC servo motors and ball-screw actuators—enable quick size changes by recalling roll positions stored in the PLC recipe library.
Welding Station (ERW)
Electric resistance welding heads operating at 300 kHz to 600 kHz heat strip edges to forging temperature (typically 1,200 °C). Induction coils deliver controlled current profiles matched to strip gauge (0.8 mm – 6 mm) and width (20 mm – 168 mm).
Weld rolls, positioned immediately after the induction coil, press softened edges together, forging a high‐quality weld seam with minimal flash.
Weld power supplies utilize IGBT converters for rapid current control, maintaining consistent weld properties despite variations in strip thickness or material grade.
Weld Bead Trimming
Inline scarfing units remove residual weld flash on the inside and outside. Scarfing heads with rotating cutter wheels trim the bead, and vacuum extraction ports capture metal shavings, reducing contamination and ensuring a clean production environment.
Sizing and Calibration
Multiple sizing stands refine tube outer diameter and circularity to within ±0.5% of nominal. Laser micrometers placed before and after the sizing section measure diameter at four quadrants around the tube, feeding back to the PLC for dynamic calibration of roll gaps.
A downstream stretch-forming module applies axial tension (5% – 8% of yield strength) to further correct ovality and improve straightness, targeting deviations below 2 mm over 3 m.
Cutoff and Scrap Handling
Flying cold saws, driven by servo motors, produce tube lengths up to 12 m with cut‐to‐length accuracy of ±5 mm at speeds up to 80 m/min for small‐diameter tubes.
For thicker wall tubes (above 4 mm), hydraulic cutoff shears deliver burr‐free ends. Chain‐shot conveyors capture scrap tube remnants, ensuring a safe and tidy workspace.
Secondary Finishing Options
End Chamfering/Beveling: Inline chamfering heads prepare tube ends for welding, threading, or flaring.
Hydrostatic Testing: Optional stations test tube integrity at pressures up to 3 MPa, detecting weld seam leaks and material defects in real time.
Surface Cleaning and Coating: Tube ends and weld seams undergo brushing and air-blow stations to remove debris. For corrosion protection, inline pre‐painting or galvanizing modules can be integrated.
Shijiazhuang Faith’s carbon steel welded tube mills accommodate a spectrum of carbon steel strip grades and tube specifications:
Standard Dimensional Ranges:
Tube diameters from 15 mm to 168 mm; wall thicknesses from 0.8 mm to 6 mm.
Common grade options: Mild steel (e.g., ASTM A500 Grade B, EN 10219 S235JR), medium carbon (e.g., AISI 1045), and microalloyed grades (e.g., ASTM A656, Q195).
These tubes find applications in furniture (chairs, tables), handrails, automotive frames, scaffolding, and general structural uses.
High-Strength Carbon Steel Tubes:
Grades such as ASTM A992, S355J2H (EU standard) requiring higher yield strengths.
To achieve targeted mechanical properties, the welding process must control heat input and seaming speed. Post-weld stretch forming and tempering ovens help refine weld microstructure and relieve residual stresses.
Coated or Pre-Paired Strips:
Pre-painted or galvannealed strip options can be processed with modified strip handling to protect coating during decoiling and leveling.
Non-marking guide rollers (polyurethane or PFA-coated surfaces) and controlled tension prevent coating damage.
Ensuring consistent quality and traceability, Shijiazhuang Faith Machinery Co.,Ltd incorporates comprehensive automation and inspection into its carbon steel welded tube mills:
PLC and HMI Integration:
A distributed PLC network (e.g., Siemens S7-1500 or Allen-Bradley ControlLogix) manages decoiler tension, leveling roll pressures, forming roll positions, weld power settings, and cutoff timing.
The HMI—typically a color touchscreen—displays live metrics (coil ID, strip thickness, weld current/voltage, tube diameter, wall thickness, line speed) and allows operators to select from preconfigured “tube recipes.” Each recipe includes over 40 parameters, ensuring repeatable setups across material grades and tube sizes.
Weld Seam Monitoring:
Surface Inspection Cameras: High-resolution cameras capture weld bead profiles at multiple angles (0°, 90°, 180°, 270°). Image analysis algorithms detect bead defects such as undercut, excessive flash, or seam misalignment.
Ultrasonic Flaw Detection (UT): Inline UT probes scan the entire weld seam at production speed, identifying internal defects—lack of fusion, porosity, or microcracks. The PLC tags defective tube sections and activates a diverter, sending them to scrap conveyors without halting production.
Thermal Profiling: Infrared pyrometers or thermal cameras monitor weld seam temperature, enabling adaptive control of welding current and speed to maintain a consistent heat‐affected zone.
Dimensional Verification:
Laser Micrometers: Positioned before and after sizing stands, these sensors measure tube outer diameter at four circumferential points, allowing the PLC to adjust roll gap positions to maintain tolerances (±0.5%).
Ultrasonic Wall-Thickness Gauges: Installed immediately after the weld station for thicker tubes (>3 mm), these gauges verify uniform wall thickness, ensuring weld zones meet required specifications.
Tension and Speed Regulation:
Decoiler, leveler, forming, and pull-through drives are all powered by digital vector VFDs, providing precise control over strip tension even during coil transitions. Encoder feedback ensures synchronization, minimizing seam eccentricity and forming errors.
Data Logging and Traceability:
Each production run is archived in a centralized SQL database. Logged parameters include coil heat number, strip thickness, weld current profiles, ultrasonic test results, and dimensional readings.
Production managers generate batch traceability reports—including pass/fail metrics for each tube length—enabling quick identification of quality issues and supporting customer audits.
Shijiazhuang Faith Machinery Co.,Ltd provides extensive customization to match each producer’s product mix, production volume, and facility constraints:
Forming Roll Stands:
Fixed-Gap Stands: Suitable for producers running a limited range of tube sizes. Roll gaps are manually adjusted via shims, with preset measurements stored in the PLC recipe for quick reference.
Servo-Driven Stands: Feature AC servo motors and ball-screw actuators that automatically position roll gaps based on selected tube diameter. Changeover times are reduced to under 45 minutes, making the mill suitable for small‐batch, frequent size changes.
Welding Head Selection:
Single-Head ERW: Common for moderate production rates (up to 60 m/min) and tube diameters from 15 mm to 89 mm.
Dual-Head ERW (Tandem Welding): Two induction coils in series—with synchronized weld rolls—double throughput to 120 m/min for high‐volume runs of standard sizes (e.g., 25 × 1.5 mm).
SAW Integration (Optional): For tubes above 114.3 mm in diameter or wall thicknesses above 6 mm, SAW modules can be installed to provide deeper weld penetration and robust bead profiles. Flux recovery units capture unused flux to reduce waste.
Cutoff Options:
Flying Cutoff Saws: Driven by servo motors for continuous operation at full line speed, producing lengths up to 12 m with ±5 mm accuracy.
Hydraulic Cutoff Shears: For heavy or large-diameter tubes requiring slower, controlled shearing. These shears produce burr-free ends suitable for immediate downstream welding or assembly.
End-Forming Accessories:
Chamfering/Beveling Units: Inline rotary cutters prepare tube ends for welding or threading. Multiple tool stations accommodate various bevel angles (e.g., 30°, 37.5°, 45°) according to customer requirements.
Cold Expansion Units: Localized cold working around the seam zone improves mechanical properties for pressure applications (e.g., hydraulic tubing).
Hydrostatic Test Stations: Inline or offline hydrostatic testers apply pressures up to 3 MPa to verify seam integrity and detect leaks. Test results are logged and linked to tube batch codes.
Process Layout Configurations:
Straight-Line Layout: Ideal for facilities with adequate linear space, minimizing material transfer distances and simplifying maintenance access.
L-Shaped or U-Shaped Layout: For plants with limited length, modules are arranged to optimize floor space while preserving logical process flow.
Skid-Mounted Modules: Each major component (decoiler, leveler, forming, welding, sizing, cutoff) can be preassembled on a steel skid, reducing on-site installation time and ensuring precise alignment.
To maximize uptime and safeguard investment, Shijiazhuang Faith Machinery Co.,Ltd provides a range of support services tailored to carbon steel welded tube mill customers:
Turnkey Installation and Commissioning:
Faith Machinery’s project managers coordinate site preparation—foundation design, civil works, and utility hookups (power, compressed air, cooling water).
Mechanical alignment, PLC wiring, and system calibration are completed on-site, followed by trial production runs using customer-supplied strip. Commissioning reports document performance metrics, weld quality, and dimensional compliance.
Operator and Maintenance Training:
A structured training curriculum covers safe operation, HMI navigation, recipe management, and routine preventive maintenance tasks—such as forming roll inspection, bearing lubrication, and welding power upkeep.
Detailed operation manuals, maintenance schedules, and troubleshooting guides are provided for continuous reference.
Spare Parts Programs:
A recommended spare parts kit includes critical components—form roll bearings, welding power supply capacitors, hydraulic seals, shear blades, and NDT probe assemblies—available for immediate dispatch.
Customers may choose standard kits sized for 2,000 operational hours or customize kits based on their specific production volumes and identified wear points.
Remote Diagnostics and Software Updates:
Secure remote access options allow Faith Machinery’s technical team to review PLC logs, analyze alarm histories, and recommend parameter adjustments without physical travel.
Periodic software updates ensure the HMI and PLC remain compatible with evolving industrial network standards, cybersecurity protocols, and data logging requirements.
Field Service and Upgrades:
Scheduled field service visits include alignment checks of forming stands, weld head tuning, and NDT equipment calibration.
Retrofit solutions—such as additional forming stands for expanded diameter ranges, higher-capacity welding power supplies for increased throughput, or advanced AI-based weld defect recognition systems—enable existing carbon steel welded tube mills to adapt to new materials or production targets.
By combining durable mechanical components, advanced automation, and rigorous quality assurance, Shijiazhuang Faith Machinery Co.,Ltd’s carbon steel welded tube mills offer manufacturers a dependable, efficient, and fully supported production platform—delivering welded carbon steel tubes that meet demanding standards for strength, dimensional accuracy, and surface finish.
