Surfacing Repair of Crusher Grate Plates Under High-Temperature Abrasive Service

Literature Overview

This paper by Huang Taiming from Chongqing Iron and Steel Works Construction Department, published in Welding journal (1991, Vol. 1, pp. 22–23), documents a practical engineering solution for a severe wear problem in iron and steel plant operations. The subject is the grate plate of an F1500×2520 fully water-cooled single-roll crusher used in the sintering machine process. These grate plates operate under extreme conditions: hot ore particles at approximately 750°C impact the working surfaces at high velocity, causing rapid abrasion of the high-temperature wear-resistant alloy overlay. The overlay material wore through severely in less than one year of service, necessitating repair or replacement.

Operating Conditions and Failure Analysis

The service environment for crusher grate plates in sintering operations is among the most demanding in the steel industry. The combination of high-temperature thermal fatigue, abrasive wear from iron ore particles, and mechanical impact loading creates a synergistic degradation mechanism that accelerates material loss far beyond what any single mechanism would predict independently.

The failure mode was predominantly abrasive wear with a thermal component. At 750°C, many conventional hardfacing alloys experience significant softening due to carbide dissolution and matrix softening. The authors identified that the original overlay material, while adequate for lower-temperature abrasive service, lacked the thermal stability required for sustained operation at sintering temperatures.

Surfacing Repair Strategy

The repair approach involved removal of the worn overlay material followed by reapplication of a more suitable high-temperature wear-resistant alloy using arc surfacing techniques. Key considerations in the repair process included:

1. Surface preparation: Complete removal of the worn overlay and any heat-affected zone material from the base plate, achieved through grinding or carbon arc gouging. Surface cleanliness is critical for ensuring proper metallurgical bond between the repair overlay and the base metal.
2. Preheating: Given the thickness of the grate plate and the carbon content of the base material, preheating to 200–300°C was necessary to prevent cracking in the base metal heat-affected zone. The thick section of the grate plate acts as a heat sink, creating steep thermal gradients that must be mitigated.
3. Overlay material selection: The selection of a more thermally stable alloy composition, potentially incorporating higher concentrations of chromium, molybdenum, and tungsten carbides, was essential for improving high-temperature wear resistance.
4. Welding procedure: Multiple thin layers were deposited to minimize dilution and ensure adequate alloy content in the final surface layer. The first layer served as a transition layer to reduce carbon pickup from the base material, while subsequent layers built up the wear-resistant surface.

Engineering Practice Implications

This case study illustrates a fundamental principle in repair welding: the failure of an overlay does not necessarily indicate a failure of the surfacing technique but rather a mismatch between the overlay material properties and the actual service conditions. The sintering machine crusher grate plate represents a case where the original design specification may have been based on inadequate understanding of the thermal component of the wear mechanism.

For modern practice, I would recommend that engineers developing overlay specifications for high-temperature abrasive service conduct accelerated wear testing that includes thermal cycling. Laboratory wear tests conducted at room temperature provide no meaningful indication of performance at 750°C. Additionally, the use of thermal barrier coatings or thermal spray applications as a protective underlayer beneath the hardfacing could extend service life by reducing the temperature experienced by the wear-resistant alloy.

Study Insights and Reflections

This paper, though brief, captures an essential lesson in engineering repair: understanding the true service environment is more important than selecting the hardest available alloy. The sintering machine crusher grate plate failure was not a simple abrasive wear problem but a complex thermal-abrasive interaction that required a fundamentally different material approach. In my experience, many overlay failures in steel plants share this characteristic of being misdiagnosed as simple wear when the true mechanism involves thermal degradation. The systematic approach of analyzing the service environment, identifying the dominant degradation mechanism, and selecting materials accordingly should be standard practice in any overlay repair program.