CLADDING TECHNOLOGY SHANXI CO., LTDApplication of RMD-01 Cladding Electrode on Single Roller Crusher
Background and Operational Context
Single roller crushers are critical equipment in mining, quarrying, and aggregate processing industries where they are subjected to extreme abrasive and impact loading conditions. The working surfaces of the crusher rollers—particularly the crushing teeth and the shell plate areas in direct contact with rock—experience material loss rates that can reach 5–15 mm per month under severe service conditions. The RMD-01 cladding electrode, a specialized hardfacing electrode designed for high-abrasion applications, has been developed to extend service life by depositing a wear-resistant overlay on these critical surfaces. This study note examines the technical basis, application methodology, and field performance of RMD-01 on single roller crushers.
Technical Characteristics of RMD-01 Electrode
The RMD-01 electrode is a martensitic hardfacing electrode with a chemical composition engineered to produce a high-hardness, high-toughness overlay suitable for severe abrasive and impact wear conditions.
| Parameter | Specification |
|---|---|
| Electrode type | SMAW (Shielded Metal Arc Welding) |
| Electrode diameter | φ3.2 mm / φ4.0 mm |
| Coating type | Basic (low hydrogen) |
| Overlay hardness (as-welded) | 50–58 HRC |
| Overlay hardness (tempered) | 45–50 HRC |
| Base metal compatibility | Carbon steel, low-alloy steel |
| Welding position | All positions (flat, horizontal, vertical, overhead) |
| Current type | DCEN (Direct Current Electrode Negative) |
| Current range (φ4.0 mm) | 160–220 A |
| Typical dilution rate | 15–25% |
| Impact toughness (Charpy V-notch, 20°C) | ≥27 J |
The microstructure of the RMD-01 overlay consists primarily of martensite with dispersed carbides (predominantly WC and Cr₇C₃), which provide the combination of hardness and toughness required for the mixed abrasion-impact loading environment of a crusher roller. The presence of tungsten carbide particles is particularly important as they resist ploughing and micro-cutting by abrasive particles.
Application Methodology on Crusher Rollers
Surface Preparation
Proper surface preparation is the foundation of successful cladding application. The roller surface must be cleaned to remove rust, scale, oil, and previous weld deposits. In practice, I follow a systematic preparation protocol:
- Mechanical cleaning: Use of angle grinder with abrasive flap wheels to remove loose scale and mill scale down to bright metal.
- Flame cleaning: For heavily scaled areas, oxy-acetylene flame cleaning is used to remove adherent scale, followed by wire brush cleaning.
- Machining of wear grooves: The existing worn surface is machined to create grooves (V-grooves or U-grooves, 6–8 mm wide, 3–4 mm deep) to improve mechanical interlocking and reduce dilution.
- Preheating: The roller is preheated to 150–250°C to minimize hydrogen cracking risk and reduce thermal shock during welding.
Welding Procedure
The welding procedure follows a multi-pass strategy to achieve the target overlay thickness (typically 4–6 mm on crusher teeth and 3–5 mm on shell areas):
| Pass | Technique | Purpose | Heat Input Control |
|---|---|---|---|
| Build-up pass | SMAW with RMD-01, φ4.0 mm | Fill grooves, establish bonding layer | 1.5–2.5 kJ/mm |
| Overlay pass 1 | SMAW with RMD-01, φ4.0 mm | First hardfacing layer | 1.2–2.0 kJ/mm |
| Overlay pass 2 | SMAW with RMD-01, φ4.0 mm | Second hardfacing layer | 1.2–2.0 kJ/mm |
| Finish pass | SMAW with RMD-01, φ4.0 mm | Final surface layer | 1.0–1.8 kJ/mm |
Interpass temperature must be maintained below 150°C to prevent softening of the previous layer and to maintain the martensitic microstructure. Excessive interpass temperature can lead to tempering of the martensite, reducing hardness by 5–10 HRC.
Post-Weld Treatment
After welding, the overlay surface is typically subjected to a tempering heat treatment to improve toughness while maintaining adequate hardness. The tempering parameters are:
- Temperature: 450–500°C
- Duration: 2 hours (furnace atmosphere)
- Cooling: Air cool or furnace cool
The tempered overlay achieves a hardness of 45–50 HRC with significantly improved impact toughness (typically 30–45 J at 20°C) compared to the as-welded condition.
Field Performance and Defect Analysis
In field trials conducted on single roller crushers processing granite and limestone, the RMD-01 overlay demonstrated service life improvements of 3–5 times compared to the original uncladded steel surfaces. However, several defect modes were observed:
| Defect Type | Frequency | Root Cause | Countermeasure |
|---|---|---|---|
| Overlay spalling | 8–12% of cases | Excessive heat input, insufficient groove preparation | Reduce heat input, deepen grooves to 4 mm |
| Cracking in overlay | 5–8% of cases | High hydrogen content, excessive restraint | Improve preheating, use low-hydrogen electrode storage |
| Poor bonding | 3–5% of cases | Inadequate surface cleaning, oxide contamination | Enhanced surface preparation, magnetic particle testing |
| Hardness below specification | 2–4% of cases | Excessive dilution from base metal | Increase number of overlay passes, use wire feeding |
Case Study: Granite Processing Application
In a granite processing plant, single roller crushers were experiencing roller replacement every 45 days. After applying RMD-01 overlay (total thickness 5 mm) to the crushing teeth and shell surfaces, the replacement interval was extended to 180 days. The overlay showed uniform wear patterns with no evidence of spalling or cracking. Metallographic examination of the worn surface revealed that the tungsten carbide particles had remained intact and were providing effective resistance to abrasive ploughing.
Key Reflections and Conclusions
The application of RMD-01 cladding electrode on single roller crushers demonstrates that hardfacing technology can deliver substantial service life extensions when properly applied. The critical success factors are meticulous surface preparation, controlled heat input to prevent dilution and thermal cracking, and appropriate post-weld tempering to balance hardness and toughness. The field performance data confirms that the martensitic-carbide microstructure of RMD-01 provides effective resistance to the mixed abrasion-impact loading characteristic of crusher applications. For engineers specifying cladding solutions for mining and quarrying equipment, the RMD-01 electrode represents a proven, cost-effective solution that significantly reduces downtime and maintenance costs. The key lesson is that hardfacing performance is determined not just by the electrode chemistry but by the entire fabrication process chain from surface preparation through post-weld treatment.