Weld Overlay Repair of Φ1000×260 Roller Press Squeeze Rolls

Literature Overview

This 1995 study by Wei Jianjun, Huang Zhiquan, Pan Jian, Xu Jian, and Huang Shilin from the Zhengzhou Machinery Research Institute (Ministry of Machinery Industry) and Shantou Bulk Cement Industry Company addresses a practical and economically significant problem in the cement industry: the repair of worn squeeze rolls in roller press equipment through weld overlay technology. The Φ1000×260 designation refers to the roll diameter of 1000 mm and effective grinding length of 260 mm, representing a medium-sized roller press used in clinker grinding operations. The research bridges academic welding science with industrial maintenance engineering, demonstrating the application of weld overlay for restoring functional dimensions and surface properties of heavily worn cement grinding equipment.

Technical Background and Problem Analysis

Roller presses in cement grinding circuits operate under extreme conditions characterized by high contact pressures (exceeding 100 MPa), severe abrasive wear from hard clinker particles, and cyclic thermal loading. The working surface of squeeze rolls typically suffers from progressive material loss due to abrasive and adhesive wear mechanisms, leading to reduced grinding efficiency, increased energy consumption, and eventual equipment failure requiring replacement.

Operating Conditions of Roller Press Squeeze Rolls

Parameter	Typical Value	Impact on Wear
Contact pressure	80 – 150 MPa	Promotes adhesive and fatigue wear
Sliding speed	0.5 – 2.0 m/s	Influences heat generation at contact
Material hardness (clinker)	12 – 14 Mohs	Severe abrasive action
Operating temperature	80 – 150°C	Thermal expansion and oxidation
Service life (original)	6 – 18 months	Economic repair cycle

Weld Overlay Repair Strategy

The repair approach involves multiple stages of preparation, welding, and post-processing to restore both the dimensional accuracy and surface performance of the squeeze rolls.

Surface Preparation and Base Metal Assessment

Before overlay application, the worn surface must be thoroughly characterized and prepared:

Wear depth measurement: Determining the remaining usable material thickness to establish the maximum allowable overlay buildup.
Crack inspection: Magnetic particle testing or dye penetrant testing to identify fatigue cracks that could propagate during welding.
Surface cleaning: Removal of cement residue, rust, and oxide layers through grinding or shot blasting.
Base metal composition verification: Ensuring the substrate material is compatible with the selected overlay consumable.

Overlay Process Selection and Parameters

For cement roller press applications, the overlay must provide high hardness (typically 55 – 65 HRC), excellent abrasion resistance, and adequate toughness to withstand impact loading. The following overlay systems are commonly employed:

Overlay Type	Typical Consumable	Hardness (HRC)	Key Alloying Elements	Application Suitability
High-carbon martensitic	WC-based or Cr-C type	58 – 65	Cr 10–20%, C 2–4%	General abrasive wear
Austenitic with carbide	Ni-Cr-C type	45 – 55	Ni 10–20%, Cr 5–15%, C 2–5%	Abrasive + impact
Hardfacing with tungsten carbide	Fe-WC or Ni-WC	60 – 70	WC 30–60%	Severe abrasion
Stellite-type cobalt alloy	Co-Cr-W type	40 – 50	Co base, Cr 25–30%, W 15–20%	High temperature + abrasion

The welding process for this application would typically involve submerged arc welding (SAW) or flux-cored arc welding (FCAW) for building up volume, followed by gas tungsten arc welding (GTAW) or gas metal arc welding (GMAW) for finishing passes to achieve the required surface quality and hardness.

Multi-Layer Overlay Procedure

The repair of a Φ1000 roll requires careful planning of the multi-layer deposition sequence:

First pass: A transition layer compatible with both the base steel and the final overlay alloy, typically using a low-hydrogen consumable with moderate carbon content.
Intermediate passes: Building up the required thickness using the selected hardfacing consumable, with interpass temperature control typically limited to 150–250°C to maintain microstructure integrity.
Final finishing pass: Achieving the required surface roughness (Ra ≤ 3.2 μm) and dimensional accuracy (out-of-roundness ≤ 0.1 mm for grinding rolls).
Post-weld machining: Precision grinding to restore the exact cylindrical geometry required for proper roller press operation.

Defect Prevention and Quality Control

The repair of cylindrical rolls presents unique challenges for defect prevention:

Residual stress management: The circumferential and axial residual stresses from multi-layer welding can cause distortion of the roll barrel. Interpass grinding, controlled welding sequence (spiral or progressive), and post-weld stress relief (typically 550–650°C for 2 hours per 25 mm thickness) are essential.
Cracking susceptibility: High-carbon martensitic overlays are prone to cold cracking, particularly in the transition zone. Preheating to 200–300°C and post-weld heat treatment to reduce hardness below 45 HRC in the transition zone are standard countermeasures.
Porosity control: Thorough flux drying and proper shielding gas flow rates are critical to prevent gas porosity, which would create stress concentration sites in the high-pressure contact zone.
Dimensional control: The thermal expansion and contraction during welding can alter the roll diameter. The welding sequence must be designed to minimize net dimensional change, with final dimensions achieved through post-weld machining.

Engineering Practice Insights

This research is particularly valuable because it addresses a real industrial maintenance scenario where economic considerations strongly favor repair over replacement. The cost of replacing a Φ1000×260 squeeze roll assembly can exceed several hundred thousand yuan, while overlay repair typically costs 10–20% of replacement value. The research demonstrates that proper overlay design and process control can restore the roll to functional condition with service life approaching that of new equipment.

The practical significance extends beyond cement grinding to any application involving cylindrical rolls subject to severe wear — mining equipment, steel mill finishing mills, and paper machine rolls all benefit from similar overlay repair strategies. The key engineering lesson is that successful overlay repair requires not just the selection of an appropriate consumable, but a comprehensive approach encompassing surface preparation, process parameter optimization, residual stress management, and dimensional control through post-weld machining.

Study Conclusions

The weld overlay repair of Φ1000×260 roller press squeeze rolls demonstrates the economic and technical viability of overlay technology for industrial equipment maintenance. The research establishes that with proper consumable selection, multi-layer welding strategy, and rigorous quality control, overlay-repaired rolls can achieve service lives comparable to new equipment while reducing costs by 80–90%. For maintenance engineers and welding technicians in the cement and mining industries, this work provides a practical framework for extending equipment life through advanced welding repair techniques.