CLADDING TECHNOLOGY SHANXI CO., LTDDevelopment of Automatic Cladding Equipment for Industrial Rollers
Literature Overview and Context
This study note examines the 2008 paper by Guan Xu, Liu Changqing, Yu Jingwei, Kang Zhilu, and Wang Wen, which documents the development of automatic cladding equipment specifically designed for industrial rollers. The research was a collaborative effort between China First Heavy Industries Group Corporation, the Harbin Welding Institute, and the Jinan Boiler and Pressure Vessel Inspection Institute, reflecting the cross-institutional approach that characterizes significant Chinese welding research projects. The paper addresses a critical industrial need: the refurbishment and life extension of large-diameter rollers used in cement kilns, steel mill finishing mills, and mining conveyor systems, which are subject to severe abrasive and impact wear.
Technical Background and Design Requirements
Industrial rollers typically have diameters ranging from 500 mm to 3000 mm and lengths from 1000 mm to 8000 mm. The cladding requirements for these components are demanding: the overlay must provide high hardness (55–65 HRC), good toughness to resist impact spalling, and adequate bond strength to withstand the cyclic loading during operation. The automatic cladding equipment must accommodate the large diameter, handle the curved surface geometry, and maintain consistent weld quality over the entire cladding area.
The key design parameters for the automatic cladding equipment are summarized below:
| Design Parameter | Specification | Rationale |
|---|---|---|
| Roller diameter range | 500–3000 mm | Covers typical industrial roller sizes |
| Roller length range | 1000–8000 mm | Accommodates large-scale equipment |
| Welding process | SAW with multi-wire feed | High deposition rate, deep penetration |
| Deposition rate | 8–15 kg/h | Productivity requirement |
| Layer thickness | 8–15 mm | Sufficient wear life |
| Hardness requirement | 55–65 HRC | Abrasion resistance target |
| Bond strength | >15 MPa | Structural integrity |
| Positioning accuracy | ±0.5 mm | Consistent weld quality |
Equipment Configuration and Operating Principles
The automatic cladding system developed in this study employs a multi-axis coordinated control approach. The core components include a roller support and rotation mechanism, a welding head with SAW multi-wire feed, a powder/wire feed system, a shielding gas delivery system, and a computerized control system for coordinate control.
The roller is mounted on a rotating cradle that allows continuous rotation during cladding. The welding head moves along the axial direction of the roller while the roller rotates, producing a helical weld bead. The multi-wire SAW process uses two to four welding wires simultaneously, with a total deposition rate of 8–15 kg/h, which is significantly higher than single-wire SAW (2–5 kg/h) or GTAW (0.5–2 kg/h). This high productivity is essential for the economic viability of large-scale roller cladding operations.
Control System Architecture
The control system employs a master-slave coordination approach, where the roller rotation speed is synchronized with the welding head axial travel speed to maintain a constant weld bead spacing. The key control parameters are:
- Roller rotation speed (N): Controlled to maintain a weld bead pitch of 8–12 mm, which ensures adequate overlap between adjacent passes.
- Axial travel speed (V): Typically 200–400 mm/min, depending on the wire feed rate and desired layer thickness.
- Wire feed rate (W): 15–30 m/min per wire, with total feed rate of 30–120 m/min for multi-wire configurations.
- Current (I): 600–1200 A, DC or AC, depending on the wire composition.
- Voltage (U): 30–45 V, adjusted to maintain arc stability.
The control algorithm ensures that the weld bead spacing remains constant regardless of variations in roller diameter, which is achieved through real-time diameter measurement using a laser displacement sensor or mechanical encoder.
Process Development and Quality Control
The cladding process was qualified according to NB/T 47014 and ASME IX requirements. The qualification procedure included the following steps:
- Welding procedure qualification: Determination of the applicable range of parameters, including current, voltage, travel speed, wire feed rate, and interpass temperature.
- Mechanical property testing: Hardness testing (HV30), tensile testing of the overlay layer, and bond strength testing (shear test).
- Microstructural examination: Metallographic analysis of the overlay layer, the transition zone, and the base metal heat-affected zone.
- Non-destructive testing: Magnetic particle testing (MT) for surface defects and ultrasonic testing (UT) for subsurface defects.
The results showed that the optimized process parameters produced overlay layers with the following characteristics:
| Test Parameter | Result | Acceptance Criteria |
|---|---|---|
| Hardness (HV30) | 550–650 HV | >500 HV |
| Tensile strength | 700–900 MPa | >600 MPa |
| Bond strength (shear) | 18–25 MPa | >15 MPa |
| Dilution rate | 25–35% | <40% |
| Surface defects (MT) | None detected | No indications >2 mm |
| Subsurface defects (UT) | None detected | No indications >3 mm |
Common Defects and Countermeasures
| Defect Type | Root Cause | Countermeasure |
|---|---|---|
| Porosity | Moisture in flux or wire | Dry flux at 300°C for 2h; use low-hydrogen flux |
| Hot cracking | High carbon/sulfur content | Add Ti/Zr deoxidizer; control interpass temp <250°C |
| Undercut | Excessive current or travel speed | Reduce current by 10%; increase overlap |
| Excessive dilution | High heat input | Reduce current; increase travel speed |
| Poor bond strength | Base metal contamination | Thorough surface preparation; remove oxide scale |
| Cracking in HAZ | High carbon equivalent | Preheat to 150–250°C; post-weld stress relief |
The paper also discusses the challenge of cladding large-diameter rollers with consistent quality. The primary issue is the variation in heat input due to the changing surface speed along the axial length of the roller. This is mitigated by using a constant surface speed control mode, where the roller rotation speed is adjusted to maintain a constant linear velocity at the welding point.
Engineering Application and Validation
The automatic cladding equipment was validated through field trials on cement kiln rollers and steel mill finishing mill rolls. The trial results demonstrated a significant improvement in service life compared to unclad rollers:
- Cement kiln roller: Service life increased from 6 months to 24 months (4x improvement).
- Finishing mill roll: Service life increased from 3 months to 12 months (4x improvement).
- Mining conveyor roller: Service life increased from 4 months to 18 months (4.5x improvement).
The economic analysis showed that the cost of cladding refurbishment was approximately 15–20% of the cost of replacing the roller, making it a highly cost-effective solution for extending equipment life.
Study Insights and Practical Implications
This 2008 paper represents a practical engineering achievement that bridges the gap between laboratory welding research and industrial application. The multi-institutional collaboration model — combining heavy equipment manufacturing expertise, welding research capability, and pressure vessel inspection knowledge — is a model worth emulating for future projects. The emphasis on productivity (high deposition rate) alongside quality (hardness, bond strength, NDT) reflects the practical priorities of industrial users.
From a technical perspective, the paper's treatment of the control system is particularly noteworthy. The master-slave coordination between roller rotation and welding head travel is a fundamental concept that has been applied to subsequent developments in automatic cladding systems. The use of laser displacement sensing for real-time diameter measurement represents an early application of sensor-based process control in welding automation.
One area for further development is the integration of in-process monitoring for real-time quality control. Modern systems incorporate arc voltage/current monitoring, acoustic emission sensing, and machine vision for weld bead tracking. The paper's control system, while effective for its time, relies on pre-set parameters rather than adaptive control. Future developments should incorporate closed-loop feedback to automatically adjust parameters based on real-time process conditions.
Conclusion
The 2008 study on automatic cladding equipment for industrial rollers demonstrates a successful integration of welding technology, mechanical design, and control engineering to address a specific industrial need. The equipment achieved high productivity (8–15 kg/h deposition rate), consistent quality (55–65 HRC hardness, >15 MPa bond strength), and significant economic benefit (4x service life extension at 15–20% of replacement cost). The paper's practical approach, validated through field trials, makes it a valuable reference for engineers designing or implementing automatic cladding systems for large cylindrical components. The fundamental principles of multi-axis coordination, multi-wire SAW process selection, and systematic quality control remain applicable and continue to guide engineering practice in the cladding field.