Roll Cladding Technology Application at Tianjin Rolling Mill No.3

Literature Overview

This 1993 publication by Li Caihua documents the application of roll cladding (weld overlay) technology at Tianjin Rolling Mill No.3, a major steel rolling facility in China. The work represents an early but significant contribution to the domestic adoption of overlay welding techniques for extending the service life of rolling mill rolls. During the 1990s, China's rolling industry faced considerable challenges with roll wear, frequent replacement, and production downtime. The introduction of systematic cladding programs was a transformative step toward cost-effective roll maintenance and productivity improvement.

Core Technical Content

Roll cladding involves depositing a hardfacing or wear-resistant alloy layer onto the working surface of a rolling mill roll, replacing the original steel surface that has been worn or damaged. The primary objective is to restore dimensional accuracy while simultaneously improving surface hardness, wear resistance, and in some cases, reducing friction and improving strip surface quality.

Cladding Methods Applied

The typical methods employed for roll cladding at that era and location included:

Flame overlay welding (oxy-fuel): Used for repair and surface restoration where moderate deposition rates were acceptable.
Submerged arc welding (SAW) with flux-cored wire: Applied for heavy build-up and wear-resistant layers with good penetration.
Gas metal arc welding (GMAW) with flux-cored wire: Offered flexibility in deposition position and good control over dilution.

Typical Cladding Materials

Application	Cladding Material Type	Typical Hardness (HRC)	Key Properties
Roughing rolls	High-carbon martensitic	45–55	High wear resistance, moderate toughness
Finishing rolls	Medium-carbon with alloy additions	35–45	Good surface finish, dimensional stability
Backup rolls	Low-alloy steel	30–40	Compressive strength, fatigue resistance
Special service	Stellite-type Co-Cr alloy	40–50	Excellent hot hardness, corrosion resistance

Process Parameters and Control

The critical process parameters for roll cladding include:

Deposition rate: Typically 3–8 mm per pass depending on wire diameter and travel speed.
Dilution control: Must be maintained below 15–20% to ensure the as-deposited properties of the overlay alloy are preserved.
Preheating: Base roll temperature maintained at 150–250 °C to reduce residual stress and prevent cracking.
Interpass temperature: Limited to below 300 °C to avoid softening of previously deposited layers.
Post-weld heat treatment: Stress-relief annealing at 550–650 °C for 2–4 hours to relieve welding residual stresses without affecting hardness.

Engineering Practice Insights

Roll Surface Preparation

Proper preparation of the roll surface is fundamental to achieving sound metallurgical bonding. This includes:

Grinding away the worn surface to a uniform depth of 2–5 mm below the original dimension.
Ensuring the surface is free of scale, rust, oil, and other contaminants.
Machining a root groove or chamfer at the boundary between the cladding zone and the base material to improve wetting and reduce stress concentration.

Defect Prevention

Common defects encountered in roll cladding include:

Defect Type	Root Cause	Countermeasure
Cracking	High carbon content, restricted cooling	Preheat, control interpass temperature, post-weld stress relief
Poor bonding	Surface contamination, insufficient penetration	Thorough cleaning, use of proper flux, adequate arc current
Excessive dilution	Too high travel speed, too low current	Optimize welding parameters, use larger wire diameter
Porosity	Moist flux, contaminated wire	Dry flux storage, use of deoxidized wire
Dimensional deviation	Uneven deposition, thermal distortion	Use of backing fixtures, multi-pass symmetric welding

Reflections and Implications

The 1993 application of roll cladding at Tianjin Rolling Mill No.3 was part of a broader national effort to modernize China's rolling industry through advanced welding technologies. The significance of this work extends beyond the specific plant — it demonstrated that overlay welding could be reliably applied to large-diameter cylindrical components with demanding dimensional tolerances. The lessons learned from this early application informed subsequent developments in roll maintenance strategies across the Chinese steel industry.

A key insight from this work is the recognition that roll cladding is not merely a repair technique but a strategic approach to roll lifecycle management. By applying appropriate cladding materials, operators can extend roll life by 2–5 times compared to standard rolled steel, significantly reducing replacement frequency and production interruptions. The experience also highlighted the importance of systematic quality control — from material selection and process parameter optimization to post-weld inspection and dimensional verification.

This early work laid the groundwork for subsequent advancements including hot-wire TIG cladding for high-productivity applications, laser cladding for precision surface engineering, and the development of proprietary consumables tailored to specific rolling applications. The principles established here — dilution control, thermal management, and systematic defect prevention — remain relevant in modern roll cladding practice.