Surfacing Repair of Continuous Casting Machine Ingot Pulling Chain

Literature Overview

This paper by Wang Yinjun, Zhang Guozhu, Li Yingjie, and Luo Jiazhi from the Technical Center and Steelmaking Plant of Shanghai Meishan Iron and Steel Company, published in Welding Technology in 2005 (Volume 34, Issue 4, pages 31-33), presents a practical engineering solution for the surfacing repair of ingot pulling chains used in continuous casting machines. The work addresses a common maintenance challenge in steelmaking operations and demonstrates the application of surfacing technology to extend the service life of critical equipment components.

Technical Background and Problem Analysis

Operating Conditions of Ingot Pulling Chains

The ingot pulling chain is a critical component in continuous casting machines, responsible for gripping and pulling the solidifying steel shell from the mold. The chain operates under extremely demanding conditions:

Operating Condition	Characteristics	Challenge
Temperature	1200-1450°C at mold exit	Thermal degradation of materials
Mechanical loading	High tensile and bending loads	Fatigue and wear
Environment	Molten slag, scale, and gases	Corrosion and erosion
Cycle frequency	Continuous operation, 24/7	Cumulative damage accumulation
Contact conditions	Abrasive contact with shell and guides	Severe wear

Component Analysis

The paper identifies two primary components requiring surfacing repair:

Ingot head (chain head): The gripping element that contacts the solidifying shell directly. Subject to thermal shock, abrasive wear from scale, and mechanical impact during shell gripping and release.
Chain links: The structural links connecting individual chain elements. Subject to tensile fatigue, bending stresses, and surface degradation from thermal and mechanical loading.

Surfacing Repair Strategy and Material Selection

Material Selection Rationale

The selection of appropriate surfacing materials is critical for successful repair. The paper describes a systematic approach to material selection based on the specific operating conditions of each component:

Component	Primary Damage Mode	Surfacing Material Type	Key Properties Required
Ingot head	Abrasive wear, thermal erosion	Hardfacing alloy	High hardness, thermal stability, spall resistance
Chain links	Fatigue, surface degradation	Tough hardfacing	Good toughness, fatigue resistance, weldability

Surfacing Process Design

The repair procedure involves several critical steps:

Surface preparation: Removal of degraded material, scale, and oxide layers to sound metal
Preheating: Controlled preheating to reduce thermal stresses and prevent cracking
Surfacing deposition: Multi-layer deposition using selected hardfacing electrodes or wire
Post-weld treatment: Stress relief and dimensional verification
Quality verification: Visual, dimensional, and hardness inspection

Process Parameters and Quality Control

Process Parameter	Ingot Head Repair	Chain Link Repair
Preheat temperature	200-300°C	150-250°C
Interpass temperature	<300°C	<250°C
Electrode type	Cast iron or Ni-based hardfacing	Low-alloy steel hardfacing
Number of layers	2-3 layers	1-2 layers
Bead size	Thin beads preferred	Moderate beads
Post-weld treatment	Stress relief 550-600°C	Stress relief 550-600°C
Acceptance hardness	Per specification	Per specification

Engineering Practice and Results

Repair Implementation and Outcomes

The paper reports successful implementation of the surfacing repair strategy, achieving reliable operation of the repaired ingot pulling chains. The key success factors included:

Appropriate material selection: Matching surfacing alloy properties to specific damage modes
Controlled process parameters: Preventing cracking and ensuring adequate bond strength
Systematic quality control: Ensuring repair integrity through comprehensive inspection
Proper surface preparation: Removing all degraded material to establish sound bonding

Cost-Benefit Analysis

Aspect	New Chain Replacement	Surfacing Repair
Material cost	High (full component cost)	Low (consumable only)
Labor cost	Moderate (replacement)	Moderate (repair)
Downtime	Extended (ordering and installation)	Minimal (on-site repair)
Environmental impact	High (waste material)	Low (minimal waste)
Service life extension	Full life	60-80% of original life
Overall cost savings	Baseline	50-70% savings

Study Insights and Reflections

This paper exemplifies the practical application of welding and surfacing technology in industrial maintenance. While the technical content may appear straightforward compared to fundamental research papers, the practical significance is substantial. In steelmaking operations, where downtime costs can exceed $100,000 per hour, the ability to perform effective on-site repairs of critical components represents enormous economic value.

The systematic approach to material selection and process design demonstrated in this work provides a template for similar repair applications across the steel industry. The key principles—understanding operating conditions, selecting appropriate materials, controlling process parameters, and verifying repair quality—are universally applicable.

From a metallurgical perspective, the repair of ingot pulling chains presents unique challenges due to the extreme thermal and mechanical environment. The surfacing materials must retain their properties at elevated temperatures, resist thermal cycling without spalling, and maintain adequate toughness to withstand impact loading. These requirements drive the selection of Ni-based or Co-based hardfacing alloys for the ingot head and tougher low-alloy deposits for the chain links.

The paper also highlights the importance of surface preparation in achieving successful surfacing repairs. In high-temperature service environments, components often develop thick layers of oxide scale, slag, and degraded material. Complete removal of these layers to sound metal is essential for achieving proper fusion and mechanical bonding of the surfacing deposit. Inadequate surface preparation is one of the most common causes of surfacing repair failure in industrial applications.

This work underscores the value of integrating metallurgical knowledge with practical engineering experience to develop effective maintenance strategies. The ability to extend component life through surface engineering not only reduces costs but also contributes to environmental sustainability by minimizing material waste and energy consumption associated with component replacement.