Surfacing Repair of Continuous Casting Machine Starter Chain

Literature Overview

Published in Welding Technology (2005, Vol. 34, No. 4, pp. 31-33), this paper documents a practical engineering case study on the surfacing repair of starter chain components in a continuous casting machine. Conducted by the Technology Center and Steelmaking Plant of Shanghai Meishan Iron and Steel Company, the work provides valuable insights into the practical application of surfacing technology in heavy industrial equipment maintenance, specifically addressing the repair of critical components in the steelmaking process.

Service Condition Analysis and Component Assessment

The starter chain (pilot bar chain) is a critical component in continuous casting operations, responsible for pulling the solidified steel shell out of the mold during the initial casting phase. The two primary wear components are:

The operating environment presents severe combined loading:

• High temperature exposure (up to 1500°C from molten steel)
• Repeated thermal cycling during each casting cycle
• Mechanical contact with mold walls and rollers
• Corrosive atmosphere from mold flux and oxide scale

Material Selection and Process Development

The paper emphasizes the importance of systematic material selection based on service condition analysis. The approach follows a logical engineering methodology:

1. Failure analysis: Identify the primary wear mechanism and failure mode of each component.
2. Material selection: Choose surfacing material matching the required properties (hardness, thermal stability, toughness).
3. Process development: Establish welding parameters ensuring sound bonding and adequate deposition.
4. Quality verification: Confirm repair effectiveness through dimensional, mechanical, and service testing.

Process Implementation and Quality Control

The repair procedure follows a structured approach:

1. Surface preparation: Remove worn material to sound base metal through grinding or machining. Inspect for cracks using magnetic particle testing (MT). Grind a generous weld groove to ensure complete fusion.
2. Preheating: Apply controlled preheat (150-250°C depending on base material carbon equivalent) to reduce thermal stresses and minimize cracking risk.
3. Surfacing deposition: Apply surfacing layers using the selected electrode, maintaining consistent bead overlap (50% minimum) and interpass temperature control.
4. Post-weld treatment: Stress relief if required by the base material specification. Dimensional restoration through machining or grinding.
5. Quality verification: Dimensional inspection, hardness testing, and potentially non-destructive examination before returning to service.

Engineering Practice Insights

This case study highlights several important principles for industrial surfacing repair:

1. Condition-based material selection: The starter head and chain links require fundamentally different surfacing materials because their failure modes differ. The starter head requires thermal and oxidation resistance at high temperatures, while chain links primarily need wear resistance and toughness.
2. Process adaptability: In a production steel plant environment, the repair process must be compatible with existing equipment and workforce capabilities. SMAW was selected as the primary process because it is portable, requires minimal equipment, and can be performed in situ without dismantling large assemblies.
3. Economic justification: Surfacing repair offers significant cost savings compared to component replacement. For large continuous casting components, the cost of replacement can be substantial, and the downtime associated with replacement is often the primary driver for rapid repair solutions.
4. Service life extension: The paper reports satisfactory service results, indicating that properly executed surfacing repair can restore components to acceptable service life, providing a viable alternative to replacement for moderately worn components.

Critical Evaluation and Lessons Learned

The practical nature of this case study makes it particularly valuable for maintenance engineers who must make rapid decisions under production pressure. The systematic approach of condition analysis, material selection, and process development provides a repeatable methodology that can be applied to similar equipment repair scenarios across the steel industry.

Summary

This case study demonstrates the successful application of surfacing technology to repair critical continuous casting starter chain components under real production conditions. The systematic approach of analyzing service conditions, selecting appropriate surfacing materials, and developing tailored welding procedures resulted in reliable repair outcomes. The work underscores the importance of engineering judgment in matching surfacing material properties to specific service demands and highlights surfacing as a cost-effective maintenance strategy for heavy industrial equipment. For maintenance engineers, this case provides a practical template for approaching surfacing repair decisions in production environments where speed, reliability, and cost-effectiveness must be balanced.