Surfacing Welding Technology for Continuous Caster Guide Roller Surface

Literature Overview

This paper by Tang Qiong and Ma Jinglan from Taiyuan Iron and Steel (Group) Company, published in Shanxi Metallurgy in 1998, addresses a critical industrial challenge: the domestic production of guide roller sleeves for imported continuous casting machines through stainless steel surfacing welding. At the time, China relied entirely on imported guide roller components for continuous casting equipment, which created significant supply chain vulnerabilities and high replacement costs. The authors undertook a systematic experimental program to develop a domestically produced equivalent, a task without any prior successful domestic precedent.

Core Technical Challenge and Background

Continuous casting guide rollers operate under extremely demanding conditions. They are subjected to:

• Continuous mechanical contact with molten steel or solidifying slabs at temperatures ranging from 600°C to over 1200°C depending on the casting stage.
• Abrasive wear from scale and oxide particles adhering to the slab surface.
• Thermal cycling that induces residual stresses and potential cracking in the substrate material.
• Corrosive attack from molten slag and steel.

The original imported components employed a layered construction: a carbon steel or low-alloy steel substrate with a stainless steel surfacing layer providing wear resistance, corrosion resistance, and thermal stability. Replicating this construction domestically required not only the correct metallurgical selection but also precise control over the welding process parameters to ensure metallurgical compatibility between the base material and the overlay.

Process Development and Experimental Approach

The authors adopted a systematic experimental methodology, which can be characterized as a structured trial-and-error approach guided by metallurgical principles. The key elements of their approach included:

Substrate Preparation

The base material for the guide roller sleeves was selected based on the mechanical requirements of the continuous casting application. Surface preparation involved thorough cleaning to remove scale, oil, and oxidation products. The critical factor was achieving a clean, oxide-free interface to ensure proper metallurgical bonding between the base metal and the surfacing layer.

Welding Process Selection

The study evaluated multiple welding processes and parameters, including:

• Shielded metal arc welding (SMAW) with different electrode types
• Submerged arc welding (SAW) for higher deposition rates
• Different preheat temperatures to manage thermal gradients

Surfacing Material Selection

The stainless steel surfacing materials were selected to provide the following properties:

Key Technical Findings

The experimental work yielded several important conclusions:

1. Multi-layer surfacing is essential. Single-layer surfacing produced insufficient overlay thickness and excessive dilution, resulting in surface properties dominated by the base metal composition. A minimum of three layers was required to achieve the target metallurgical composition in the surface zone.
2. Interlayer temperature control is critical. Maintaining interlayer temperatures between 200°C and 400°C provided the optimal balance between thermal stress management and welding productivity. Temperatures below 200°C increased the risk of cold cracking, while temperatures above 400°C promoted excessive grain growth in the overlay.
3. Welding sequence optimization reduced distortion. A symmetric, spiral-pattern welding sequence from the center outward minimized angular distortion of the roller sleeve, which was critical for maintaining dimensional accuracy in the finished component.
4. Post-weld heat treatment was necessary. A controlled cooling followed by stress-relief annealing at 600-650°C for 2 hours eliminated residual stresses that could lead to delayed cracking during service.

Metallurgical Considerations

The metallurgical challenge in this application centers on the dilution effect. When welding stainless steel onto a carbon steel substrate, the first weld pass experiences significant dilution from the base metal, resulting in a carbon content in the weld metal that can exceed 0.3%. This elevated carbon level promotes chromium carbide precipitation at grain boundaries, leading to sensitization and reduced corrosion resistance.

The solution adopted was:

• Using a high-alloy first pass to increase the alloy content in the dilution zone
• Applying subsequent passes with lower alloy content to gradually transition to the target surface composition
• Controlling the total dilution ratio to below 30% in the final surface layer

Engineering Practice Implications

This work represents a significant milestone in the domestication of critical continuous casting components in China. The practical implications include:

• Cost reduction: Domestic production eliminated the premium associated with imported components and reduced lead times from months to weeks.
• Supply chain independence: The ability to produce replacement rollers domestically eliminated the risk of production stoppages due to supply interruptions.
• Technology transfer: The systematic experimental approach established a framework that could be adapted to other surfacing applications in the steel industry.

Critical Reflection

The paper, while valuable in its practical achievements, could benefit from more detailed metallurgical characterization. Modern standards such as ISO 14171 (Welding of ferrous materials - Surface welding) provide more rigorous requirements for overlay weld qualification, including metallographic examination, hardness profiling, and corrosion testing protocols. A contemporary approach would incorporate:

• Dilution studies using optical emission spectroscopy or XRF analysis
• Metallographic examination of the fusion line for cracking and microstructural assessment
• Hardness traverse measurements from substrate through overlay to quantify the dilution gradient
• Impact testing of the heat-affected zone to verify toughness retention

Despite these limitations, the work demonstrates the fundamental principles that remain valid today: systematic parameter optimization, careful material selection, and rigorous quality verification are the cornerstones of successful surfacing welding operations.

Summary

The Taiyuan Iron and Steel study represents an important early contribution to domestic surfacing welding technology in China's steel industry. By systematically exploring welding parameters, material combinations, and process sequences, the authors successfully developed a production-capable process for guide roller sleeves that met all functional requirements. The methodology employed—comparative experimental testing with rigorous performance evaluation—establishes a template for similar engineering challenges. For practicing engineers, the key takeaway is that successful surfacing welding requires not merely the selection of an appropriate overlay material, but the holistic optimization of the entire welding system including base preparation, parameter selection, sequence planning, and post-weld treatment.