Hardfacing Repair of Slab Continuous Casting Machine Rollway Rolls

Literature Overview

This paper by Shan Lianying from Anyang Iron and Steel (Group) Company Sanbo Division, published in China Metallurgy (1998, Vol. 8, No. 3, pp. 37–38), presents an industrial case study of hardfacing repair technology applied to rollway rolls in slab continuous casting machines. The paper documents the development and implementation of a hardfacing-based repair methodology that significantly reduced roll consumption and extended component service life.

Engineering Context and Problem Statement

Rollway rolls are critical components in continuous casting machines, responsible for supporting and guiding the solidifying slab as it travels through the casting line. These rolls operate under severe conditions:

High mechanical loads from the weight of the slab
Thermal cycling from proximity to molten metal
Abrasive wear from scale and oxide debris
Corrosive attack from flux and slag residues

The combination of these factors results in high consumption rates and frequent replacement requirements. In the context of 1998 Chinese steel industry operations, roll supply was a significant bottleneck that constrained production capacity.

Failure Analysis and Material Selection

The study begins with a systematic investigation of roll material properties and failure modes. The analysis reveals that conventional roll materials experience a combination of:

Surface fatigue cracking
Abrasive wear in the contact zone
Thermal cracking from repeated heating and cooling
Adhesive wear from slab-scale interaction

Based on this failure analysis, appropriate hardfacing alloy compositions were selected to address the specific wear mechanisms encountered in service. The hardfacing alloys were chosen to provide:

High hardness for resistance to abrasive wear
Thermal shock resistance for cyclic temperature changes
Adequate toughness to prevent crack propagation
Compatibility with the base roll material

Hardfacing Repair Methodology

The repair process involves:

Surface preparation. Removal of damaged material through grinding or machining to expose sound base metal.
Preheating. Controlled heating of the roll to reduce residual stress and prevent cracking during hardfacing.
Hardfacing deposition. Application of multiple layers of hardfacing alloy using appropriate welding processes.
Post-weld treatment. Controlled cooling or stress relief annealing to minimize residual stresses.

Process Parameter	Recommended Range	Purpose
Preheat temperature	200–400°C	Reduce cracking risk
Interpass temperature	Controlled below 250°C	Maintain deposit properties
Number of layers	2–4 depending on thickness	Achieve target deposit thickness
Post-weld cooling	Controlled rate	Minimize residual stress

Performance Results and Economic Impact

The implementation of hardfacing repair technology yielded measurable improvements:

Extended roll life. Hardfaced rolls demonstrated significantly longer service intervals compared to conventionally manufactured rolls.
Reduced roll consumption. The number of rolls required per casting campaign was substantially decreased.
Cost reduction. The total cost per unit of steel produced was reduced through decreased roll replacement frequency.
Improved production reliability. Reduced unplanned roll changes minimized casting interruptions and quality variations.

Engineering Practice Insights

This case study exemplifies the practical application of hardfacing technology in a heavy industrial setting. Several lessons emerge from this work:

Failure analysis must precede repair strategy. Understanding the specific wear mechanisms is essential for selecting appropriate hardfacing alloys.
Process control is critical. Inconsistent hardfacing deposition can result in premature failure, negating the benefits of the repair.
Economic analysis should guide technology adoption. The cost savings from extended roll life must exceed the investment in hardfacing equipment and consumables.

Reflections and Study Insights

This paper, while modest in technical depth compared to more recent publications, represents an important example of applied metallurgical engineering. The challenge of rollway roll repair in continuous casting is not merely a materials science problem—it is an integrated engineering challenge that requires understanding of metallurgy, welding, tribology, and production economics.

From my perspective, the most valuable aspect of this study is its demonstration that hardfacing repair can be a viable alternative to complete component replacement, particularly in situations where spare parts supply is constrained. In modern steel production, where continuous casting machines operate at high utilization rates, the ability to quickly repair and return components to service is a significant operational advantage.

The principles established in this 1998 study remain relevant today. Modern hardfacing alloys, welding processes, and quality control methods have advanced considerably since then, but the fundamental approach—analyze failure, select appropriate materials, apply controlled repair, verify performance—remains the same. Engineers working on roll repair today should recognize the value of this early industrial experience and build upon it with contemporary materials and process capabilities.