CLADDING TECHNOLOGY SHANXI CO., LTDSurfacing Material Research and Application for Steel Rolling Guide Plates
Literature Overview and Background
Steel rolling guide plates are critical components in rolling mill guide rolls, responsible for directing and supporting the strip during the rolling process. They operate in an extremely harsh environment characterized by high temperatures (up to 900°C), intense friction from hot steel strip contact, abrasive wear from scale and scale particles, and occasional impact loading from strip misalignment. The guide plate surface undergoes rapid degradation, leading to dimensional deviation, increased rolling force, and potential strip surface defects. Weld overlay provides the primary means of restoring guide plate geometry and enhancing surface properties for extended service life.
The literature under study systematically investigates surfacing materials for steel rolling guide plates, examining the relationship between material composition, microstructure, and tribological performance under simulated and actual service conditions. The research provides practical guidance for material selection and process optimization in industrial applications.
Core Technical Points and Material Systems
Service Environment Analysis
Understanding the service environment is fundamental to material selection. The study identifies four primary degradation mechanisms affecting guide plate surfaces:
- Abrasive wear: Caused by iron oxide scale particles embedded in the strip surface, producing ploughing and micro-cutting of the guide plate surface
- Adhesive wear: Resulting from localized cold welding at asperity contacts between the guide plate and the hot strip
- Thermal fatigue: Caused by repeated heating and cooling cycles as the strip passes through the guide roll
- Oxidative wear: High-temperature oxidation of the guide plate surface, particularly in the presence of steam or oxygen
| Degradation Mechanism | Temperature Range | Severity | Primary Countermeasure |
|---|---|---|---|
| Abrasive wear | 600-900°C | High | High hardness, hard carbides |
| Adhesive wear | 500-800°C | Moderate | Low friction coefficient, self-lubrication |
| Thermal fatigue | 600-900°C | High | Thermal conductivity, thermal expansion match |
| Oxidative wear | 700-900°C | Moderate | Chromium content, oxide scale protection |
Surfacing Material Selection
The study evaluates several material systems for guide plate surfacing, each offering different combinations of wear resistance, thermal stability, and toughness.
| Material System | Composition Range | Hardness (as-welded) | Thermal Stability | Application |
|---|---|---|---|---|
| High Cr austenitic (Cr25Ni) | 22-28% Cr, 18-22% Ni | 200-280 HBW | Excellent | High-temperature finishing mills |
| High Cr martensitic (Cr12) | 11-14% Cr, 0.3-0.6% C | 500-600 HBW | Good | Intermediate temperature mills |
| High-speed steel (HSS) | 6-8% W, 4-6% Mo, 3-5% V | 600-700 HBW | Good | Cold rolling guides |
| Ni-based alloy (Stellite) | 55-65% Ni, 5-10% Cr, 3-5% Co | 350-450 HBW | Excellent | Special alloy rolling |
| Composite (Cr + SiC) | 20-25% Cr, 5-10% SiC | 400-500 HBW | Good | Abrasive wear dominated |
The study recommends that material selection should be based on a comprehensive evaluation of the specific service conditions, including strip temperature, rolling speed, strip surface condition, and expected service life. A decision matrix approach is proposed to systematically evaluate material options against multiple performance criteria.
Process Optimization and Microstructural Control
Welding Process Selection
The geometry of guide plates (typically flat plates with complex contours, thicknesses of 20-80 mm) requires flexible welding processes capable of achieving uniform coverage and good surface finish.
| Process | Deposition Rate | Surface Quality | Heat Input | Suitability |
|---|---|---|---|---|
| SAW | High | Requires machining | High | Bulk resurfacing |
| PTA | Moderate | Good | Moderate | Precision resurfacing |
| GTAW | Low | Excellent | Low | Final layer, repairs |
| Laser cladding | High | Very good | Low | Precision resurfacing |
| Hot-wire TIG | Moderate | Good | Moderate | Large area coverage |
The study recommends a multi-layer approach combining high-deposition-rate processes for bulk material with precision processes for the final surface layer. The final layer should be deposited with parameters optimized for surface quality and hardness uniformity.
Microstructural Characteristics
The microstructure of the surfacing layer directly determines its tribological performance. The study documents the following microstructural features for high-chromium austenitic surfacing materials:
- Austenite matrix: Provides thermal stability and resistance to thermal cracking
- Chromium carbides (Cr7C3, Cr23C6): Provide wear resistance through hard particle dispersion
- Grain size: Typically 10-50 μm, with finer grains providing better toughness
- Segregation patterns: Chromium enrichment at grain boundaries, which can affect corrosion resistance
The study emphasizes that controlling the cooling rate during welding is critical for achieving the desired microstructure. Rapid cooling (achieved through low heat input processes or pre-cooling of the substrate) produces finer microstructures with improved wear resistance, while slower cooling (through higher heat input or preheating) produces coarser microstructures with improved toughness.
Performance Characterization and Field Testing
Laboratory Testing Results
| Test Method | Material A (Cr25Ni) | Material B (Cr12) | Material C (Stellite) |
|---|---|---|---|
| Vickers hardness (HV) | 220-280 | 500-600 | 350-450 |
| Dry friction coefficient | 0.45-0.55 | 0.35-0.45 | 0.40-0.50 |
| Abrasive wear rate (mm³/N·m) | 2.5×10⁻⁶ | 0.8×10⁻⁶ | 1.2×10⁻⁶ |
| Thermal fatigue life (cycles) | 50,000+ | 20,000-30,000 | 40,000-50,000 |
| Oxidation resistance at 800°C | Excellent | Moderate | Excellent |
The results demonstrate that no single material system offers optimal performance across all service conditions. High-chromium austenitic materials excel in thermal stability and oxidation resistance, making them suitable for high-temperature applications. High-chromium martensitic materials offer superior abrasive wear resistance but suffer from reduced thermal fatigue life. Ni-based alloys provide excellent overall performance but at higher material cost.
Field Performance Data
The study presents field trial data from several rolling mills, demonstrating the practical benefits of optimized surfacing material selection:
| Mill Application | Original Material | Optimized Material | Service Life Extension |
|---|---|---|---|
| Hot strip finishing mill | Cr25Ni (standard) | Cr25Ni (optimized composition) | 30-50% |
| Intermediate mill | Cr12 (standard) | Cr12 + SiC composite | 40-60% |
| Cold rolling guide | HSS (standard) | HSS (optimized heat treatment) | 20-30% |
| Special alloy rolling | Stellite (standard) | Stellite (modified composition) | 25-40% |
The service life extensions achieved through material optimization demonstrate the significant economic benefits of proper material selection and process control.
Defect Analysis and Quality Control
| Defect Type | Root Cause | Detection Method | Countermeasure |
|---|---|---|---|
| Surface porosity | Gas entrapment, incomplete melting | PT, UT | Optimize shielding gas flow, control wire feed |
| Cracking | Excessive residual stress, hydrogen | MT, PT | Control preheat, use low-hydrogen consumables |
| Uneven hardness | Process parameter variation | Hardness mapping | Implement real-time parameter monitoring |
| Poor bond strength | Surface contamination, insufficient heat | Bond strength test | Thorough surface preparation, adequate heat input |
| Excessive dilution | High heat input, poor process control | Metallography | Reduce heat input, use backfill groove |
The study recommends implementing a comprehensive quality control system that includes in-process monitoring of welding parameters, post-weld hardness mapping, and periodic field performance tracking. This system enables early detection of quality issues and continuous process improvement.
Engineering Practice and Implementation
The study emphasizes the importance of systematic approach to surfacing material selection and process optimization. A structured methodology is proposed:
- Service condition analysis: Document strip temperature, rolling speed, strip surface condition, and failure modes
- Material screening: Evaluate candidate materials against service requirements using laboratory testing
- Process qualification: Develop and qualify welding procedures through coupon testing
- Field trial: Implement qualified procedures in production with performance monitoring
- Continuous improvement: Analyze field performance data and revise procedures as needed
A case study demonstrates the application of this methodology in a hot strip finishing mill, where systematic material optimization resulted in a 45% extension of guide plate service life and a 30% reduction in maintenance costs.
Key Questions and Reflections
The literature raises several important questions for further investigation. How can the tribological performance of surfacing materials be further enhanced through advanced alloy design and microstructural engineering? What are the limits of thermal fatigue resistance for current surfacing materials, and can new material systems extend guide plate life further? Additionally, the integration of condition monitoring systems with surfacing material selection could enable predictive maintenance strategies that optimize guide plate replacement intervals.
Summary and Study Insights
This literature provides a comprehensive technical framework for surfacing material selection and process optimization for steel rolling guide plates. The key insight is that optimal surfacing performance requires a systematic approach that integrates service condition analysis, material selection, process optimization, and quality control. For engineers in the steel industry, the study demonstrates that significant improvements in guide plate service life and rolling mill productivity can be achieved through proper material selection and process control. The structured methodology proposed in the study provides a practical roadmap for implementing surfacing optimization programs in industrial settings, offering a pathway to reduced maintenance costs and improved production efficiency.