Study Note on Alloy Cladding Technology Application in Jigang Dry Quenching Coke Blower

Literature Overview

The dry quenching coke (DQC) process represents a significant advancement in coke oven gas recovery, replacing traditional wet quenching methods with inert gas cooling. This process generates substantial amounts of fine dust and abrasive particulates that severely degrade blower components through erosion and corrosion. The application of alloy cladding technology to protect critical blower components is a practical engineering solution that extends service life and reduces maintenance costs. This study note examines the technical approach, material selection, and implementation details of alloy cladding applied to Jigang Steel's dry quenching coke blower, drawing lessons from this industrial application.

Operating Environment and Damage Mechanisms

The dry quenching coke blower operates in an extremely harsh environment characterized by:

• High temperature: Gas temperatures range from 200 to 350 degrees Celsius, well above ambient conditions.
• Abrasive particulates: Coke dust particles with sizes ranging from 5 to 100 micrometers are carried in the gas stream at velocities exceeding 20 m/s.
• Corrosive atmosphere: The gas contains carbon monoxide, carbon dioxide, hydrogen sulfide, and water vapor, creating a reducing and corrosive environment.
• Cyclic loading: The blower experiences continuous vibration and pressure fluctuations that promote fatigue damage.

The combined effect of erosion and corrosion (erosion-corrosion) creates a synergistic damage mechanism that is significantly more aggressive than either mechanism alone. The abrasive particles remove the protective oxide layer, exposing fresh metal to the corrosive atmosphere, which accelerates material loss. This damage pattern typically manifests as localized thinning at impact zones, particularly at impeller blades, volute walls, and inlet guide vanes.

Material Selection for Cladding

The selection of cladding alloy for DQC blower components requires balancing erosion resistance, corrosion resistance, and mechanical properties. The following table presents candidate materials and their suitability for this application:

Based on the damage mechanism analysis, the literature recommends a zoned approach to cladding material selection. The impeller blades, which experience the most severe erosion, are clad with Inconel 625 or Stellite 6 for maximum erosion resistance. The volute walls and inlet sections, which experience primarily corrosion with moderate erosion, are clad with 310 stainless steel or Inconel 625. This approach optimizes the balance between performance and cost.

Cladding Process Implementation

The cladding process for DQC blower components involves several key steps that must be carefully executed to ensure quality. The typical process flow includes:

1. Surface preparation: All cladding surfaces are ground to bare metal with a minimum 10 mm overlap beyond the cladding boundary. The surface finish should be smooth and free of contaminants.
2. Preheating: Components are preheated to 150-200 degrees Celsius to reduce thermal stresses and prevent cracking.
3. Multi-pass cladding: The overlay is deposited in multiple passes to achieve the required thickness while maintaining controlled dilution. The first pass is critical for establishing the metallurgical bond, while subsequent passes build thickness.
4. Post-weld inspection: Each pass is inspected for surface quality, and the final overlay is examined for thickness uniformity and defect detection.
5. Post-weld heat treatment: Stress relief at 600-700 degrees Celsius for 2 hours is recommended to reduce residual stresses.

The literature documents the use of GTAW and GMAW processes for the blower cladding application. GTAW was used for the impeller blades due to the need for precise control and low dilution, while GMAW was applied to the larger volute surfaces for productivity. The typical overlay thickness was 2-3 mm for impeller blades and 3-4 mm for volute walls.

Performance Evaluation

The effectiveness of the cladding application was evaluated through both laboratory testing and field performance monitoring. The following table summarizes the key performance indicators:

The field performance data demonstrates that the alloy cladding technology significantly extends the service life of DQC blower components. The 310 stainless steel cladding on volute walls showed excellent performance with minimal erosion after 30 months of continuous operation. The Inconel 625 cladding on impeller blades maintained its integrity even after 24 months of exposure to high-velocity abrasive gas flow.

Defect Analysis and Countermeasures

Despite the overall success of the cladding application, several defects were encountered during implementation. The following table presents the identified defects, their causes, and the corrective actions taken:

The most significant defect encountered was excessive dilution in the first pass of impeller blade cladding, which resulted in reduced corrosion resistance of the overlay. The corrective action involved revising the welding procedure to reduce current by 15 percent and increase travel speed by 20 percent, achieving dilution below 15 percent in subsequent production runs.

Engineering Practice Insights

The Jigang DQC blower cladding project provides several valuable lessons for similar industrial applications. First, the importance of accurate damage mechanism analysis cannot be overstated. Understanding whether the primary damage mechanism is erosion, corrosion, or a combination of both directly influences material selection and process design. Second, the zoned cladding approach, where different materials are applied to different zones based on local damage severity, provides an optimal balance between performance and cost.

The project also highlights the importance of post-weld heat treatment in reducing residual stresses that can lead to cracking during service. The stress relief treatment at 600-700 degrees Celsius was found to be particularly effective for the Inconel 625 overlays, reducing residual stresses by approximately 60 percent. Additionally, the implementation of regular thickness monitoring during service allowed early detection of wear patterns and informed maintenance scheduling.

Key Reflections

The application of alloy cladding technology to the Jigang dry quenching coke blower demonstrates the effectiveness of this approach in extending component life in harsh industrial environments. The key insight is that successful cladding requires a systematic approach that integrates damage mechanism analysis, material selection, process optimization, and quality assurance. The project achieved a 4-12 times improvement in service life with a reasonable increase in initial fabrication cost, resulting in significant economic benefits.

This study reinforces the principle that cladding technology is not a one-size-fits-all solution but must be tailored to the specific operating conditions and damage mechanisms of each application. The experience gained from this project provides valuable guidance for engineers working on similar industrial applications, emphasizing the importance of thorough analysis, careful process design, and rigorous quality control in achieving reliable cladding performance.