EDTCrWB Wear-Resistant Electrode Surfacing of Scraper Conveyor Middle Trough

Literature Overview

This paper by Ma Changfa and Zhao Yuanjie from Nanjing Coal Machinery Works, published in Coal Science and Technology (1991, Vol. 19, No. 6, pp. 13-14), presents an engineering-focused evaluation of EDTCrWB wear-resistant electrode for surfacing scraper conveyor middle troughs in coal mining applications. The study analyzes the material from both processability and economic perspectives, concluding that it represents a cost-effective surfacing solution for coal mine equipment.

Technical Context and Application Requirements

Scraper conveyor middle troughs are critical components in underground coal mining operations, subject to severe abrasive wear from coal, rock, and debris. The middle trough experiences:

• Continuous sliding contact with the scraper chain and coal material.
• Impact loading from falling coal and rock fragments.
• Abrasive wear from hard mineral particles (quartz, feldspar) embedded in the coal.
• Potential for spalling and chipping of the surfacing layer.

The service conditions demand a surfacing material that provides:

• High hardness and wear resistance to extend service life.
• Adequate toughness to resist impact and spalling.
• Good bonding strength to the base metal (typically low-carbon structural steel).
• Weldability with minimal cracking tendency.
• Economic viability for widespread application.

EDTCrWB Electrode Characteristics

EDTCrWB is a high-carbon chromium-tungsten-boron steel electrode designed for arc surfacing. The composition typically includes:

• Chromium (Cr): 15-25% for carbide formation and oxidation resistance.
• Tungsten (W): 5-10% for high-temperature stability and wear resistance.
• Boron (B): 0.5-1.5% for additional hardness contribution.
• Carbon (C): 2-3% for high carbide volume fraction.

The electrode coating is designed to provide:

• Stable arc characteristics for consistent deposition.
• Sufficient alloy transfer to the weld deposit.
• Slag formation for protection and heat retention.
• Deoxidation and sulfur/phosphorus removal.

Processability Assessment

The paper evaluates the processability of EDTCrWB electrode through several criteria:

The electrode is designed for SMAW (Shielded Metal Arc Welding) surfacing, which is the most commonly available welding process in mining environments. The electrode diameter is typically 3.2 mm or 4.0 mm, with recommended currents in the range of 120-200 A depending on diameter and position.

Economic Analysis

The economic evaluation in this paper considers:

• Material cost: EDTCrWB electrode cost per kilogram compared to alternative surfacing methods.
• Labor cost: Deposition rate and productivity.
• Equipment cost: SMAW equipment is widely available and relatively inexpensive.
• Maintenance cost: Frequency of re-surfacing and downtime for repair.
• Service life extension: Reduction in trough replacement frequency.

The analysis concludes that EDTCrWB electrode offers favorable economics for coal mine applications due to:

• Relatively low material cost compared to specialized surfacing consumables.
• High deposition efficiency of SMAW process.
• Minimal equipment requirements.
• Significant extension of trough service life (typically 3-5 times compared to un-surfaced troughs).

Engineering Practice Guidelines

For engineers applying EDTCrWB electrode to scraper conveyor middle trough surfacing, the following practical guidelines are recommended:

Welding Procedure Specification

• Base metal: Low-carbon structural steel (Q235, Q345 equivalent).
• Preheat temperature: 100-150°C for thick sections (>25 mm) or cold ambient conditions.
• Interpass temperature: Maximum 250°C to avoid excessive softening of the previous pass.
• Electrode angle: 15-25° from vertical for horizontal positions.
• Travel speed: Moderate to ensure adequate melting and alloy transfer.
• Pass number: 2-3 passes for typical trough thickness.
• Post-weld heat treatment: Not typically required but recommended for critical applications.

Surface Preparation and Inspection

• Remove rust, scale, and contaminants from the surfacing area.
• Bevel the surface if required for adequate root penetration.
• Clean between passes to remove slag completely.
• Inspect for cracks, porosity, and undercut after surfacing.
• Measure hardness to verify deposit properties (typically 55-65 HRC).
• Perform bond strength testing on qualified specimens.

Common Defects and Solutions

Study Insights and Engineering Value

This paper, though published in 1991, provides valuable practical guidance for surfacing applications in the mining industry. The emphasis on both processability and economics reflects the practical constraints faced by mining operations, where cost-effectiveness is often as important as performance.

The study demonstrates that even relatively simple welding consumables can provide significant performance improvements when properly applied. The EDTCrWB electrode represents a practical solution for extending the service life of scraper conveyor troughs without requiring sophisticated equipment or highly trained personnel.

For contemporary practice, several considerations should be added:

• Environmental regulations may restrict the use of certain electrode coatings containing harmful substances.
• Safety standards for underground mining operations may impose additional requirements on welding procedures.
• Alternative surfacing methods (such as thermal spray or laser cladding) may be considered for specific applications where higher performance is required.
• Condition monitoring and predictive maintenance can help optimize surfacing intervals and reduce downtime.

The economic analysis methodology presented in this paper is directly applicable to surfacing qualification decisions in any industrial setting. Engineers should always evaluate surfacing solutions not only on technical performance but also on total cost of ownership, including material cost, application cost, maintenance cost, and service life extension.

In conclusion, this paper provides a practical, engineering-focused evaluation of EDTCrWB electrode for scraper conveyor trough surfacing. The emphasis on processability and economics makes it directly relevant for mining engineers and maintenance planners seeking cost-effective solutions for abrasive wear problems. The fundamental principles of surfacing material selection and application remain valid today, even as new consumables and processes become available.