Zhuojin Pipe Fitting Co., LtdOverlay Welding Repair and Strengthening Process for Four-Roller Crusher Roller Sleeves
Literature Overview
This 1997 paper by Gan Zhixi, published in Welding, describes the overlay welding repair and strengthening of roller sleeves used in four-roller crushers at the Xiangtan Steel Company's Huaguang Equipment Repair Center. Four-roller crushers are critical equipment in metallurgical enterprises for coke crushing, and the roller sleeves are classified as consumable parts with a normal service life of 3 to 4 months. The sleeves are made of 30CrMo cast steel and are subject to both abrasive wear and corrosion. The paper reports that the plant consumes approximately 50 roller sleeves per year, and the adoption of overlay welding technology has significantly reduced production costs.
Failure Analysis and Repair Requirements
The primary failure modes of the roller sleeves are abrasive wear and corrosion, which occur during the crushing of coke particles. The 30CrMo cast steel material provides adequate strength but lacks the surface hardness required for long-term resistance to the severe abrasive conditions in coke crushing. The normal service life of 3 to 4 months indicates a high wear rate, and the annual consumption of 50 sleeves represents a substantial material and production cost.
The repair process addresses two distinct challenges: the removal of damaged material and the restoration of surface properties. The pre-weld preparation involves machining away the cracked and fatigued surface layer, followed by filling of deep depressions with J506 electrode and grinding to a smooth finish. The sleeves are then preheated in a furnace at a rate of 50°C/h to a temperature of approximately 250°C, with a 2-hour hold at temperature.
| Parameter | Specification |
|---|---|
| Sleeve material | 30CrMo cast steel |
| Normal service life | 3–4 months |
| Annual consumption | ~50 sleeves |
| Preheat rate | 50°C/h |
| Preheat temperature | ~250°C |
| Hold time | 2 hours |
| Filler for depressions | J506 electrode |
| Primary failure modes | Abrasive wear, corrosion |
The preheating procedure is critical for this application. The 30CrMo cast steel has a relatively high carbon equivalent, which increases its susceptibility to cold cracking during welding. The controlled preheating rate of 50°C/h ensures uniform temperature distribution throughout the thick cast section, minimizing thermal gradients and residual stresses. The 2-hour hold at 250°C allows for stress relief and hydrogen diffusion, further reducing the risk of hydrogen-induced cracking.
Process Design and Technical Details
The overlay welding process for the roller sleeves involves several key steps:
- Surface preparation: The damaged surface is machined to remove cracks, fatigue layers, and corrosion products. Deep depressions are filled with J506 electrode and ground smooth.
- Preheating: The sleeve is heated in a furnace at 50°C/h to 250°C and held for 2 hours.
- Overlay welding: Multiple layers of hard-facing material are deposited to build up the required thickness and hardness.
- Post-weld treatment: Controlled cooling or tempering may be applied to relieve residual stresses.
- Post-weld machining: The overlay surface is machined to the required dimensional tolerance and surface finish.
- Quality inspection: The repaired sleeve is inspected for hardness, surface integrity, and dimensional accuracy.
The selection of J506 electrode for filling depressions is a practical choice. J506 is a low-hydrogen, basic-flux covered electrode with good mechanical properties and low crack susceptibility, making it suitable for preheated thick sections of alloy steel. The hard-facing overlay material, while not explicitly specified in the abstract, would typically be a high-carbon chromium or cobalt-based alloy designed to provide high surface hardness and wear resistance.
Engineering Practice and Cost-Benefit Analysis
The economic justification for overlay welding repair is compelling. With 50 sleeves consumed annually, the cost of new sleeves represents a significant expense. Overlay welding repair extends the service life of each sleeve by multiple cycles, reducing the annual consumption rate and associated costs. The following cost-benefit considerations should be evaluated:
- Material cost: The cost of hard-facing consumables is significantly lower than the cost of new 30CrMo cast steel sleeves.
- Labor cost: The welding and machining labor for repair is less than the cost of manufacturing new sleeves.
- Downtime reduction: Repairing sleeves on-site or at a repair center reduces production downtime compared to ordering and waiting for new sleeves.
- Extended service life: Each repair cycle adds 3 to 4 months of service life, meaning a single sleeve can be repaired multiple times before retirement.
The overlay welding approach also offers technical advantages beyond cost savings. The hard-facing material can be selected to provide superior wear and corrosion resistance compared to the original 30CrMo cast steel, effectively upgrading the sleeve performance. Additionally, the repair process allows for the correction of manufacturing defects and surface irregularities, improving the overall quality of the sleeve.
Study Insights and Reflections
This paper exemplifies the practical application of overlay welding in industrial maintenance and component strengthening. The systematic approach to repair—encompassing failure analysis, process design, preheating, welding, and quality verification—serves as a model for similar repair applications in heavy industry. The emphasis on preheating and controlled cooling rates reflects a deep understanding of the metallurgical challenges associated with welding thick sections of alloy steel.
The case study also highlights the importance of process documentation and standardization. By establishing a repeatable repair procedure, the repair center can ensure consistent quality across multiple repair cycles. This is essential for maintaining the reliability of production equipment and minimizing unplanned downtime.
For engineers dealing with similar wear component repairs, the following lessons are applicable:
- Always perform a thorough failure analysis before initiating repair.
- Select welding consumables that are compatible with the base material and provide the required surface properties.
- Implement rigorous preheating and interpass temperature control to prevent cracking.
- Design the overlay thickness to provide both wear resistance and sufficient machining allowance.
- Conduct comprehensive quality inspections after repair to verify the effectiveness of the process.
In conclusion, the overlay welding repair of four-roller crusher roller sleeves demonstrates the significant economic and technical benefits of overlay technology in industrial maintenance. By extending component life, reducing material costs, and improving surface properties, overlay welding provides a sustainable solution for managing wear in heavy-duty equipment. Engineers should adopt this systematic approach to repair and strengthening as a standard practice in their maintenance programs.