Overlay Welding Repair of Phi 1000x260 Roller Press Squeeze Rolls

Literature Overview

This technical paper by Wei Jianjun, Huang Zhiquan, Pan Jian, Xu Jian, and Huang Shilin, published in the journal "Cement" (1995, Issue 8, p. 15), documents the overlay welding repair of a Phi 1000x260 mm roller press squeeze roll in a bulk cement industry application. The research was conducted by the Zhengzhou Machinery Research Institute (under the former Ministry of Machinery) in collaboration with the Shantou Bulk Cement Industrial Company. This is a practical engineering case study that bridges metallurgical research with industrial maintenance operations.

Equipment Background and Failure Context

Roller Press Operating Conditions

The Phi 1000x260 mm roller press squeeze roll operates under severe tribological conditions in cement grinding circuits. The squeeze rolls function in a high-pressure, abrasive environment where:

Contact pressure: Typically 100-200 MPa between the squeeze roll and the feed material
Abrasive particles: Cement clinker and raw meal particles with high hardness (Mohs 5-7)
Roll surface speed: Variable depending on mill configuration
Operating temperature: Elevated due to frictional heating and hot feed material
Cycle life: Approximately one year of continuous operation before significant wear

Wear Pattern Analysis

After nearly one year of service, the static (slow-speed) roll exhibited severe surface wear. The wear pattern was characterized by:

Progressive loss of the original roll surface profile
Deepened wear grooves aligned with the roll axis
Surface roughening and localized material removal
Potential dimensional out-of-tolerance conditions affecting roller press performance

Overlay Welding Repair Strategy

Material Selection for Overlay

The repair approach involved applying a hardfacing overlay to restore the roll surface to acceptable dimensions and provide enhanced wear resistance. The selection criteria for the overlay material included:

Criterion	Requirement	Rationale
Hardness	Significantly higher than base roll steel	Enhanced abrasion resistance
Dilution resistance	Low susceptibility to base metal dilution	Maintain overlay properties
Crack resistance	Adequate toughness despite high hardness	Prevent cracking during service
Bond strength	Strong metallurgical bond to roll substrate	Prevent spalling or delamination
Weldability	Compatible with roll base steel	Minimize residual stress and HAZ cracking

Process Parameters and Procedure

The repair welding procedure would have involved:

Surface preparation: Grinding away the worn surface, removing any loose material, and preparing a uniform welding surface with appropriate root preparation.
Preheating: Applying controlled preheat to reduce thermal gradients and minimize residual stress in the large-diameter roll.
Multi-pass overlay: Building up the overlay layer in multiple passes to control dilution, manage heat input, and achieve the target overlay thickness.
Interpass temperature control: Maintaining interpass temperatures to prevent excessive grain growth and manage residual stress.
Post-weld treatment: Possibly including stress relief annealing to reduce welding residual stresses.

Technical Challenges and Solutions

Thermal Management

The large mass of the Phi 1000 mm roll creates significant thermal inertia. This presents both challenges and advantages:

Challenge: Slow cooling rates may promote coarse grain formation and reduced hardness in the overlay layer.
Advantage: The thermal mass acts as a heat sink, reducing the risk of excessive heat input damage to the base metal.

Residual Stress Control

Welding overlay deposits on a large cylindrical component introduces complex residual stress patterns. The circumferential and axial stress components interact with the roll's operational bending moments. Mitigation strategies include:

Controlled preheating (typically 150-300°C for carbon steel rolls)
Low heat input per pass
Multi-pass welding with controlled interpass temperatures
Post-weld stress relief treatment

Dimensional Accuracy

Restoring the roll to precise dimensional tolerances through overlay welding requires careful control of:

Build-up height per pass
Profile uniformity around the roll circumference
Final machining allowance
Geometric accuracy (runout, diameter uniformity)

Engineering Practice Insights

This case study exemplifies the practical application of overlay welding technology in industrial maintenance. The decision to repair rather than replace the squeeze roll reflects economic considerations:

Cost comparison: Overlay welding repair typically costs 20-40% of the cost of a new roll.
Downtime reduction: Repair can be completed in days versus weeks or months for procurement of a new roll.
Performance enhancement: The overlay material may offer superior wear resistance compared to the original roll surface, potentially extending service life beyond the original design.

The study also highlights the importance of understanding the service environment when selecting repair strategies. Cement roller press applications demand overlay materials with high abrasion resistance, which often requires trade-offs with toughness and weldability.

From a quality assurance perspective, the repair process should include:

Visual inspection of all welds
Magnetic particle or dye penetrant testing of the overlay surface
Hardness verification across the overlay layer
Dimensional inspection after final machining
Functional testing under load before returning to service

This practical case demonstrates how overlay welding technology enables cost-effective restoration of critical industrial equipment, extending asset life and reducing unplanned downtime in cement production facilities.