On-Site Cladding Repair of Phi1000x400 Roller Press

Literature Overview and Background

This technical report, published in the Cement journal in 2002, documents the on-site cladding repair of a Φ1000×400 roller press used in cement production at Futuan Building Materials Co., Ltd. The roller press is a critical piece of equipment in the cement grinding circuit, where two rollers compress raw material or clinker into a dense cake. The rollers are subjected to extreme compressive loads, abrasive wear, and impact loading. When the roller surface degrades, cladding repair is often the most economical solution compared to complete roller replacement. The study involves collaboration between Futuan Building Materials, the Zhengzhou Mechanical Research Institute, and Henan Construction Fifth Company.

Core Technical Content

Roller Press Operating Conditions

Parameter	Specification
Roller diameter	Φ1000 mm
Roller length	400 mm
Operating temperature	80-150 °C
Compressive load	200-350 t
Wear mechanism	Abrasive + impact + adhesive
Typical roller material	42CrMo or similar alloy steel

The roller press in cement grinding operates under severe conditions. The material being ground (raw meal or clinker) contains sharp mineral particles that cause abrasive wear on the roller surface. Additionally, the high compressive loads can cause surface fatigue and spalling. The roller surface hardness typically needs to be in the range of 50-58 HRC for optimal grinding performance, but wear reduces this hardness over time.

Cladding Repair Procedure

The on-site repair process involves the following steps:

Surface preparation: The worn roller surface is ground or milled to remove all damaged material, reaching sound base metal. The surface is cleaned of oil, rust, and contaminants. A V-groove or U-groove is prepared to provide mechanical keying for the cladding layer.
Preheating: The roller is preheated to 200-300 °C using induction heating or oxy-fuel heating. This temperature is critical to prevent hydrogen-induced cracking in the high-strength alloy steel base.
Underlay welding: A transition layer of low-carbon, high-ductility material (such as E8010 or equivalent) is deposited to reduce dilution and provide a compatible metallurgical interface between the base steel and the hard alloy cladding.
Overlay welding: The hard alloy cladding is deposited using surfacing electrodes or flux-cored wire. Multiple passes are required to achieve the target thickness of 4-8 mm. The cladding material typically contains Cr, Mo, and sometimes Ni to achieve hardness of 55-62 HRC.
Post-weld heat treatment: Stress-relieving annealing is performed to reduce residual stresses. The temperature is carefully controlled to avoid softening the cladding layer while effectively relieving stresses in the base metal.
Machining and finishing: The cladded surface is ground to the required geometric tolerances and surface finish. The final surface hardness is verified by Rockwell hardness testing.

Process Parameters for Overlay Welding

Parameter	Value
Welding process	SMAW / FCAW
Electrode/wire diameter	3.2-4.0 mm
Current	150-250 A
Voltage	22-28 V
Travel speed	50-80 mm/min
Layers	2-4 layers
Target cladding thickness	4-8 mm
Preheat temperature	200-300 °C
Interpass temperature	≤ 250 °C

Defect Analysis and Countermeasures

On-site repair introduces additional challenges compared to workshop repair, including limited access, environmental contamination, and difficulty in maintaining consistent process parameters.

Defect	Root Cause	Prevention
Cracks	High residual stress, hydrogen, thermal shock	Adequate preheat, controlled cooling, PWHT
Poor bond	Incomplete fusion, surface contamination	Thorough surface prep, proper root pass
Hardness variation	Uneven dilution, inconsistent parameters	Multi-layer technique, parameter control
Geometric deviation	Shrinkage, thermal distortion	Balanced welding sequence, backing plate

The on-site nature of this repair requires particular attention to environmental factors. Wind, rain, and dust can significantly affect weld quality. Wind shielding and moisture control are essential, especially when using hydrogen-sensitive consumables.

Engineering Practice Insights

The roller press repair case demonstrates the economic viability of cladding repair for large, heavy equipment. A complete roller replacement can cost hundreds of thousands of dollars and require significant downtime. Cladding repair, while requiring careful execution, can restore the roller to near-original condition at a fraction of the replacement cost.

A key insight from this case is the importance of the welding sequence. For a cylindrical roller, the welding sequence should be planned to minimize distortion. Welding should proceed in a balanced pattern, alternating between opposite sides of the roller circumference. Longitudinal welding should proceed from one end to the other, with frequent reversal to distribute heat input evenly.

The roller press application also highlights the importance of matching the cladding material properties to the operating conditions. In cement grinding, the roller surface must be hard enough to resist abrasive wear but tough enough to withstand impact loading from material feed. A purely hard alloy cladding may be prone to chipping under impact, so a multi-layer approach with a tough underlayer and hard overlay is often preferred.

Study Reflections and Conclusions

This literature provides a practical case study of on-site cladding repair for heavy industrial equipment. The key lessons are the importance of thorough surface preparation, controlled preheating, proper welding sequence planning, and post-weld heat treatment. The on-site environment adds complexity but does not fundamentally change the metallurgical principles that govern cladding success. Engineers should ensure that welding procedures are qualified for the specific base material and cladding combination, and that welders have adequate training and experience in hard alloy surfacing techniques. The economic and operational benefits of cladding repair make it a preferred option for critical rotating equipment, provided the repair is executed to the required quality standards.