CLADDING TECHNOLOGY SHANXI CO., LTDOverlay Welding Repair of Rolling Mill Guide Plate Heads
Literature Overview
This 1994 paper, published in Welding (焊接), was authored by Wan Weiguo from the Steel Research Institute of Maanshan Iron and Steel Company. The study addresses the practical problem of repairing worn rolling mill guide plate heads through overlay welding. Rolling mill guide plates are critical components that direct and support the steel strip as it passes through the rolling mill, and their wear directly affects product quality and rolling efficiency. The repair of these components through overlay welding is a cost-effective alternative to complete replacement, provided that the repair process is properly designed and executed.
Core Technical Content
Rolling Mill Guide Plate Service Conditions
Rolling mill guide plates operate under severe conditions that lead to rapid wear:
| Condition | Description | Impact on Wear |
|---|---|---|
| Temperature | 600-1200°C (hot rolling) | Thermal fatigue, oxidation |
| Contact pressure | 50-200 MPa | Abrasive wear, adhesive wear |
| Sliding speed | 1-10 m/s | High friction, heat generation |
| Material contact | Hot steel strip | Abrasive particles, oxide scale |
| Environment | Water cooling, scale | Corrosive attack, thermal cycling |
Wear Mechanisms
The wear experienced by guide plate heads is a combination of:
- Abrasive wear: Caused by oxide scale and hard particles on the steel strip surface.
- Adhesive wear: Due to metal-to-metal contact under high pressure and temperature.
- Thermal fatigue: From repeated heating and cooling cycles.
- Oxidative wear: From oxidation of the guide plate surface at elevated temperatures.
- Erosive wear: From water cooling and scale removal.
Overlay Welding Repair Strategy
The paper describes a systematic approach to overlay welding repair of worn guide plate heads:
| Repair Step | Description | Key Considerations |
|---|---|---|
| Surface preparation | Grind away worn material | Remove all damaged metal, achieve sound base |
| Preheating | Heat base to 200-400°C | Reduce residual stress, prevent cracking |
| First layer | Low-alloy surfacing | Bridge base metal, reduce dilution |
| Overlay layers | Wear-resistant alloy | 2-4 passes for 3-6 mm total thickness |
| Post-weld treatment | Controlled cooling or PWHT | Relieve stress, improve toughness |
| Machining | Machine to final dimensions | Achieve required geometry and surface finish |
Overlay Material Selection
The selection of overlay material depends on the specific service conditions:
| Service Condition | Recommended Overlay | Hardness | Key Property |
|---|---|---|---|
| Hot rolling (high temp) | Ni-Cr alloy or austenitic stainless | 30-40 HRC | High-temperature strength |
| Cold rolling | High-C martensitic or carbide alloy | 50-60 HRC | Wear resistance |
| General purpose | Cr-Mo low-alloy steel | 40-50 HRC | Balance of properties |
| High abrasion | Tungsten carbide-containing alloy | 60-70 HRC | Extreme wear resistance |
Typical Welding Parameters
| Parameter | Specification |
|---|---|
| Process | SMAW or SAW |
| Electrode/wire | Low-hydrogen Ni-Cr or high-C martensitic |
| Current | 150-300 A (SMAW), 300-500 A (SAW) |
| Voltage | 20-28 V (SMAW), 28-34 V (SAW) |
| Travel speed | 100-200 mm/min (SMAW), 200-400 mm/min (SAW) |
| Preheat | 200-400°C |
| Interpass temperature | < 300°C |
| Overlay thickness | 3-6 mm |
| Number of passes | 3-5 |
Quality Control
The paper emphasizes the importance of quality control in guide plate repair:
- Visual inspection: Examination of weld surfaces for proper profile and absence of surface defects.
- Magnetic particle testing (MT): Inspection for cracks or surface discontinuities.
- Hardness testing: Verification of overlay hardness and hardness profile through the cladding thickness.
- Dimensional inspection: Verification of final geometry after machining.
- Service life tracking: Monitoring of repaired components to validate repair effectiveness.
Engineering Practice Integration
The overlay welding repair of rolling mill guide plate heads is a common industrial practice that can significantly extend component service life and reduce production costs. The key to successful repair lies in proper assessment of the remaining base material, selection of appropriate overlay material, and rigorous quality control.
The paper's approach reflects the practical engineering philosophy of extending component life through targeted repair rather than complete replacement, which is particularly important for large, expensive components such as rolling mill guide plates. The systematic approach to material selection, process parameter optimization, and quality assurance provides a valuable framework for engineers implementing overlay welding repairs in industrial settings.
Study Reflections
This paper provides practical guidance on the overlay welding repair of rolling mill guide plate heads, a common maintenance activity in steel production facilities. The work highlights the importance of understanding the specific wear mechanisms in service and selecting overlay materials accordingly. The systematic approach to repair—from surface preparation through post-weld machining—provides a comprehensive framework that can be adapted to other industrial repair applications. The emphasis on quality control and service life tracking underscores the importance of validating repair effectiveness through ongoing monitoring. Engineers working on industrial repair and maintenance should study this work for its practical insights into overlay welding repair strategies and quality assurance practices.