Chrome Carbide Cladding Composite Steel Plate and Its Application in Cement Vertical Mill Equipment

Literature Overview

This study examines the fabrication, characterization, and industrial application of chromium carbide (Cr₇C₃ and Cr₃C₂) overlay cladding composite steel plates used in cement vertical mill components. Cement grinding operations are characterized by severe abrasive wear from hard limestone particles, making wear-resistant cladding a critical requirement for mill internals including grinding rollers, grinding discs, guide rings, and feed funnels. The research covers the complete value chain from welding consumable selection through process optimization to field performance evaluation.

Core Technical Content

Material System and Metallurgy

Chrome carbide overlay cladding typically employs a multi-layer system consisting of a transition layer (to accommodate thermal expansion mismatch), a binder layer (usually Mn13 or low-carbon steel), and a hardfacing layer containing Cr₇C₃ or Cr₃C₂ carbides. The chromium carbide phases have hardness values of 1600-2000 HV for Cr₇C₃ and 1400-1800 HV for Cr₃C₂, significantly exceeding the hardness of the surrounding binder matrix.

Welding Process Selection

The choice of welding process significantly affects the quality and performance of the cladding:

• Submerged Arc Welding (SAW): High deposition rate (500-2000 g/min), suitable for thick overlays; however, higher dilution (30-50%) reduces surface carbide content
• Flux-Cored Arc Welding (FCAW): Good all-position capability, moderate deposition rate (200-500 g/min); dilution of 20-35%
• MAG Welding: Good process control, moderate dilution (25-40%); suitable for repair and localized overlay
• Plasma Transferred Arc (PTA): Low dilution (10-20%), excellent surface quality; higher equipment cost

Microstructure and Wear Mechanism

The wear resistance of Cr₇C₃ cladding is attributed to:

1. Hard carbide particles (1600-2000 HV) that resist abrasive particle penetration
2. Matrix hardness of 800-1200 HV that provides a tough support for the carbides
3. Carbide network distribution that prevents crack propagation through the layer
4. Work-hardening binder matrix that accommodates impact loading

The dominant wear mechanism in cement grinding is micro-cutting by hard angular particles, supplemented by micro-ploughing and adhesive wear. The Cr₇C₃ particles act as hard asperities that plough through the abrasive medium rather than being removed by it.

Application in Cement Vertical Mill Equipment

Component-Specific Requirements

Field Performance Data

A comprehensive field study at a cement plant processing limestone with Mohs hardness of 3-4 (with some harder inclusions up to Mohs 6-7) demonstrated the following results:

• Original unclad grinding roller: replaced every 200-300 hours (wear rate: 0.3-0.5 mm per 100 hours)
• Cr₇C₃ clad grinding roller: replaced every 2500-3500 hours (wear rate: 0.02-0.03 mm per 100 hours)
• Improvement factor: 8-12 times
• Economic benefit: Despite 3-5 times higher initial cost, the cost per hour of service is reduced by 70-80%

Quality Control and Inspection

Critical quality control measures include:

1. Bond strength testing: Minimum 200 MPa shear bond strength required for critical components
2. Hardness mapping: Surface hardness should be 800-1200 HV with no unmelted flux inclusions
3. Penetrant testing (PT): Mandatory for detection of surface cracks and porosity
4. Ultrasonic testing (UT): For detection of lack of fusion at the cladding/substrate interface
5. Macroscopic examination: Cross-section analysis to verify carbide distribution and layer thickness

Defect Analysis and Countermeasures

Study Insights and Reflections

The most significant insight from this study is that the economic justification for chrome carbide cladding in cement mill applications is overwhelmingly favorable, with payback periods typically less than 3 months for critical components. The key to successful implementation lies in proper welding consumable selection, rigorous process parameter control, and thorough quality inspection. Particular attention must be paid to the transition layer, which accommodates the thermal expansion mismatch between the high-carbon hardfacing and the structural steel substrate. Without an appropriate transition layer, cracking at the interface is inevitable under thermal cycling conditions. Furthermore, the study underscores that wear resistance alone is insufficient; the cladding must also possess adequate toughness to resist spalling under impact loading, which is a common failure mode in cement grinding applications where material is dropped from height onto the grinding surface.

Concluding Summary

These five studies collectively represent the breadth and depth of modern cladding technology, spanning from fundamental materials research on composite wear mechanisms to advanced numerical simulation techniques, from innovative process enhancement through ultrasonic technology to practical industrial applications in cement grinding. The common thread throughout all studies is the critical importance of understanding the metallurgy of the fusion zone and the interface between dissimilar materials. Whether the application involves WC/Mn13 composites for mining equipment, austenitic stainless steel overlays for corrosion resistance, EDM cladding for precision repair, ultrasonic-enhanced welding for quality improvement, or chrome carbide cladding for cement mill components, the fundamental principles of dilution control, residual stress management, and microstructure optimization remain constant. Engineers working in this field must develop a systematic approach that integrates materials science fundamentals with practical process knowledge and quality control discipline to achieve reliable, long-lasting cladding solutions that deliver maximum economic and technical value in demanding industrial applications.