Overlay Welding Repair Scheme for Roller Press Roller Surface Wear

Literature Overview

This paper by Zhao Chun, published in Inner Mongolia Petrochemical Industry (2011, Vol. 37, No. 17, pp. 85-86), describes a practical overlay welding repair scheme for worn roller press roller surfaces. The author is affiliated with Inner Mongolia Zhongshi Complete Equipment Co., Ltd. The paper addresses the common problem of roller surface wear caused by contact with hard iron particles and abrasive materials during cement grinding operations, and presents a repair methodology using CO₂ gas shielded arc welding with specialized hardfacing consumables.

Core Technical Content

Roller presses in cement grinding circuits experience severe abrasive wear on the roller surface due to the grinding action between the rollers and the material being processed. The wear pattern is typically characterized by:

Gross material loss: Removal of the original hardfacing layer and exposure of the base metal.
Surface roughening: Formation of deep grooves and pits from embedded hard particles.
Geometry distortion: Loss of the original roller profile, affecting grinding efficiency.
Iron particle embedding: Hard iron particles from the cement clinker or grinding aids become embedded in the roller surface, accelerating wear.

The repair scheme presented in this paper uses CO₂ gas shielded arc welding (GMAW-C) with a series of hardfacing wires developed by a welding consumable manufacturer. The approach is designed to restore the roller surface geometry and provide a wear-resistant overlay layer.

Consumable Selection

The paper describes the use of a series of hardfacing wires, each designed for different wear conditions:

Wire Type	Hardness (HV)	Application	Key Alloying Elements
Type A	450-550	Moderate abrasion	Cr, Cr₃C₂
Type B	550-650	Severe abrasion	Cr, Mo, Cr₇C₃
Type C	650-750	Extreme abrasion	Cr, Mo, W, Cr₇C₃
Type D	350-450	Impact + abrasion	Ni, Cr, B

Welding Process Parameters

Parameter	Value	Notes
Welding process	CO₂ GMAW (GMAW-C)	Semi-automatic or manual
Wire diameter	1.2-1.6 mm	Depends on repair thickness
Current	180-260 A	Higher for thicker deposits
Voltage	22-28 V	Arc voltage for CO₂ shielding
Travel speed	200-350 mm/min	Slower for thicker deposits
Wire feed speed	6-10 m/min	Synchronized with travel
Shielding gas flow	15-20 L/min	CO₂, dry and oil-free
Preheat	100-150 °C	Prevents cracking in base metal
Interpass temperature	< 200 °C	Controls residual stress

Repair Procedure

Surface preparation: The worn roller surface is ground to remove loose material and embedments. The base metal is exposed and cleaned to bare metal.
Preheating: The roller is preheated to 100-150 °C using induction heating or torch heating.
First pass: A root pass is deposited using a compatible filler metal to ensure good fusion with the base metal. This pass is typically thinner (2-3 mm) and uses a lower heat input.
Build-up passes: Subsequent passes are deposited using the selected hardfacing wire to build up the required thickness. The number of passes depends on the material loss and desired final thickness.
Cooling: The roller is allowed to cool slowly to prevent cracking. Controlled cooling is achieved by covering the weld area with insulating blankets.
Machining: The weld deposit is machined to restore the original roller geometry and surface finish.
Inspection: The repaired surface is inspected for defects, hardness, and geometry.

Quality Control

The repair quality is verified through the following inspections:

Inspection	Method	Acceptance Criteria
Visual inspection	VT	No cracks, porosity, or undercut
Penetrant testing	PT (ASTM E709)	No linear indications
Hardness test	Rockwell C (ASTM B231)	45-60 HRC (hardfacing layer)
Dimensional check	CMM or laser scan	Within ±0.5 mm of nominal
Surface roughness	Ra measurement	Ra ≤ 3.2 μm after machining
Wear test	Laboratory abrasion test	Volume loss < 0.5 cm³/1000 cycles

Engineering Practice Insights

The paper highlights several practical aspects of roller press sleeve repair:

Cost-effectiveness: CO₂ GMAW is significantly cheaper than GTAW or FCAW for large-area overlay welding. The consumable cost is lower, and the deposition rate is higher.
Field applicability: The semi-automatic or manual CO₂ GMAW process can be performed in the field without the need for sophisticated equipment, making it suitable for on-site repairs.
Wear life extension: The repair restores the roller surface to its original geometry and provides a new hardfacing layer, extending the service life of the roller by 1-2 years depending on operating conditions.
Downtime minimization: The repair process can be completed in 24-48 hours for a typical roller press sleeve, minimizing production downtime.

Common Defects and Countermeasures

Defect	Cause	Countermeasure
Hot cracking	Excessive carbon equivalent, high sulfur	Use low-carbon consumables, control preheat
Cold cracking	Hydrogen embrittlement	Dry consumables, preheat, post-weld heat treatment
Porosity	Moisture in consumables or gas	Use dry consumables, check gas supply
Lack of fusion	Insufficient heat input, poor surface preparation	Increase current, grind surface before welding
Excessive spatter	High arc voltage, poor gas coverage	Optimize voltage, use gas nozzle with proper standoff
Dilution	Excessive base metal melting	Use multiple thin passes, lower heat input

Key Reflections

This paper represents a practical, field-oriented approach to roller press sleeve repair. The emphasis on CO₂ GMAW with hardfacing consumables reflects the reality of industrial maintenance operations, where cost, speed, and practicality often take precedence over optimal metallurgical outcomes.

The paper's approach of using a series of hardfacing wires for different wear conditions is particularly thoughtful. Rather than using a single consumable for all repairs, the selection of the appropriate wire based on the specific wear mechanism ensures optimal performance. This material selection strategy is consistent with best practices in tribology and wear engineering.

The paper also underscores the importance of surface preparation and preheating in repair welding. These seemingly simple steps are often neglected in field repairs, leading to poor fusion, cracking, and premature failure of the repair. The systematic approach described in the paper provides a reliable methodology for achieving durable repairs.

The wear life extension achieved through proper repair is significant from an economic standpoint. For a cement plant, each hour of production downtime costs thousands of dollars. A well-executed repair that extends roller life by even a few months can result in substantial savings compared to roller replacement.

Concluding Summary

These five literature pieces collectively illustrate the breadth and depth of overlay welding technology across different industrial applications. From the complex manufacturing of gasifier shells with S31603 inner wall overlay to the practical repair of cement roller press sleeves using CO₂ GMAW hardfacing, the underlying metallurgical principles and quality control requirements remain consistent. The evolution from manual flat plate electrode techniques to machine vision-guided robotic systems reflects the industry's ongoing pursuit of improved quality, consistency, and productivity. The ferrite content control study highlights the importance of microstructural engineering in achieving reliable performance in demanding service conditions. Together, these papers provide a comprehensive picture of overlay welding as a critical technology in heavy equipment manufacturing and maintenance, where the selection of appropriate materials, processes, and quality control methods determines the long-term reliability and economic viability of industrial equipment.