Laminar cooling rolls, as key equipment in the hot rolling laminar system, are positioned between the finishing mill exit and the coiler, playing a crucial role in transporting high-temperature strip steel. These rolls operate in harsh conditions, running continuously at temperatures between 400°C and 600°C, subjected to thermal shocks from cooling water, alternating loads, and compressive forces. Under such extreme conditions, traditional roll surfaces often experience wear, corrosion, and peeling, significantly affecting production efficiency and product quality.
Technological Bottlenecks in Traditional Processes
Traditionally, the manufacturing of laminar cooling rolls involves using flame spraying of Ni60 alloy followed by induction remelting. However, this approach has evident limitations:
- Insufficient Bonding Strength: The bond strength between the sprayed layer and the substrate is typically below 200MPa, leading to the potential for coating peeling during use.
- Significant Deformation and Uneven Coatings: The high heat input in traditional processes causes severe deformation of the workpiece, with uneven coating microstructure, resulting in a limited service life that fails to meet the demands of modern continuous production.
مزایای تحولآفرین فناوری پوششدهی لیزری
Compared to traditional surface modification techniques, laser cladding offers significant technical advantages:
Metallurgical Quality Breakthrough
The cladding layer forms a complete metallurgical bond with the substrate, with bond strength reaching over 85% of the substrate strength. Rapid solidification during the process (cooling rates of 10^4-10^6 K/s) results in fine dendritic microstructures, significantly enhancing the coating’s density.
Precision Thermal Control
Laser cladding adopts a low heat input process, precisely controlling the dilution rate within a 3-8% range. The heat-affected zone (HAZ) of the substrate remains smaller than 1mm, effectively preventing workpiece deformation and ensuring dimensional stability.
Innovative Material Design
Greenstone-Tech has developed a specialized alloy powder system tailored to the unique working conditions of laminar cooling rolls. This system optimizes the ratio of carbide-forming elements like chromium, molybdenum, and tungsten to enhance high-temperature wear resistance while maintaining coating toughness.
Engineering Practice and Performance Verification
Through in-depth research on the failure mechanisms of laminar cooling rolls, Greenstone-Tech has developed a proprietary process solution:
Innovative Equipment and Process
The ULC series high-speed cladding equipment, combined with a coaxial powder feeding system, ensures precise control of the cladding process. By optimizing key parameters such as laser power (3-4 kW), scanning speed (10-15 mm/s), and powder feed rate (20-30 g/min), the cladding layer’s quality is consistently maintained.
Achieved Performance Indicators
Real-world applications demonstrate that the cladding layer thickness remains stable at 1.3mm, with surface hardness reaching 55-60 HRC. Even at 600°C, the coating maintains excellent wear resistance, with no defects like pores or cracks. The service life of these rolls exceeds traditional processes by more than three times.
Quality Control System
A comprehensive quality control process has been established, including ultrasonic testing, hardness gradient analysis, and metallographic examination. This ensures that every repaired roll meets the specified technical standards. Industrial verification confirms that this process extends the maintenance cycle of laminar cooling rolls to 2.5 times longer than traditional methods, significantly reducing downtime.
Laser Cladding vs. Flame Spray Welding
Laser Cladding Process:
Workpiece → Degreasing → Laser Cladding → Finishing → Inspection
Flame Spray Welding Process:
Workpiece → Degreasing → Sandblasting → Preheating → Spray Welding → Remelting → Insulation → Finishing → Inspection
Comparison of Comprehensive Performance between Laser Cladding and Flame Spray Welding
| Performance | پوششدهی لیزری | Flame Spray Welding |
|---|---|---|
| Process Flow | Simple, easy to operate | Complex, narrow solid-liquid phase line, difficult mirror control |
| Bonding | Metallurgical bond | Partial metallurgical bond, prone to detachment |
| Hardness (HRC) | ≥55 | ≥56 |
| Coating Performance | ||
| Wear Resistance | Wear rate k (mm³/(N·m), 10⁻⁵) | Wear rate k (mm³/(N·m), 10⁻⁵) |
| Corrosion Resistance | Neutral salt spray 1000h, Grade 10 or above | Neutral salt spray 1000h, Grade 10 or above |
| Powder & Utilization | Iron-based powder, 12 kg/m² | Nickel-based powder, 13–14 kg/m² |
| Coating Lifespan | ≥2 years, steel throughput ≥8 million tons | 1.5–2 years |
| Process Stability | Stable process, good repeatability | Sensitive to powder, prone to defects such as pinholes |
Technological Outlook
With the increasing focus on green manufacturing, laser cladding technology is becoming the preferred solution for surface strengthening of laminar cooling rolls due to its exceptional performance and environmental benefits. Greenstone-Tech will continue to optimize process parameters, develop new alloy materials, and promote the large-scale application of this technology in hot continuous rolling, providing technical support for equipment upgrades in the steel industry.
لیدیا لیو
دکتر لیدیا لیو – پژوهشگر ارشد، متخصص یکپارچهسازی بازار و راهکارها دکتر لیدیا لیو یک حرفهای ترکیبی منحصر به فرد است که بهطور کامل تخصص فنی سطح بالا در ساخت افزودنی را با دیدی تیزبینانه نسبت به یکپارچهسازی بازار و منابع ترکیب میکند. او بهعنوان دکترا و پژوهشگر ارشد در زمینه ساخت افزودنی، دانش فنی عمیقی دارد و در عین حال بهعنوان پلی حیاتی میان فناوری پیشرفته و نیازهای بازار عمل میکند. ارزش منحصربهفرد او در تواناییاش برای درک عمیق پیچیدهترین چالشهای فنی پیش روی مشتریان و، بر اساس دیدی جامع از اکوسیستم جهانی ساخت افزودنی، یکپارچهسازی دقیق بهترین منابع و راهحلهای فنی نهفته است....
