Zhuojin Pipe Fitting Co., LtdSurfacing Technology for 1450 Rolling Mill Rolls Using Submerged Arc Welding
Literature Overview
The paper by Tu Xiaodong, published in Welding (1992, Vol. 4, pp. 17–20), documents the successful application of wear-resistant surfacing welding to rolls used in the underground coiling box of a 1450 rolling mill. The work was conducted at the Second Heavy Machinery Works, a major Chinese heavy equipment manufacturer. The study focuses on the guide rolls, assist rolls, and coiling rolls that handle hot steel during the coiling operation, and reports successful surfacing of both actual production rolls and simulation test rolls of 140 mm and 370 mm diameters. This work is classified under TG455, indicating its relevance to surfacing welding technology for industrial components.
Technical Background and Challenges
Rolls in a hot rolling mill coiling box operate under extreme conditions: they are subjected to hot metal contact temperatures, mechanical loading from the weight of the coiled strip, and continuous frictional wear from the hot steel surface. The combination of thermal cycling, mechanical stress, and abrasive wear leads to rapid degradation of the roll surface, necessitating frequent maintenance or replacement. The conventional approach of replacing worn rolls is costly and causes production downtime. Surfacing welding offers a practical solution by restoring or enhancing the surface properties of existing rolls.
The specific challenge in this application is the geometry of the rolls. The guide rolls, assist rolls, and coiling rolls have different diameters, surface curvatures, and operating orientations, which complicate the surfacing process. The underground location of the coiling box further constrains equipment access and operator working conditions. The 1450 mill designation indicates a wide-strip hot rolling mill, where the rolls are relatively large and the surfacing volume is significant.
Surfacing Process and Results
The following table presents the key process parameters and outcomes reported in the study:
| Roll Type | Diameter | Surfacing Method | Electrode / Flux Type | Key Performance |
|---|---|---|---|---|
| Guide roll | Production size | Submerged arc surfacing | Low-alloy hardfacing | Wear-resistant layer restored |
| Assist roll | Production size | Submerged arc surfacing | Low-alloy hardfacing | Surface hardness improved |
| Coiling roll | Production size | Submerged arc surfacing | Low-alloy hardfacing | Extended service life |
| Simulation roll 1 | 140 mm | Submerged arc surfacing | Test electrode | Process validation |
| Simulation roll 2 | 370 mm | Submerged arc surfacing | Test electrode | Scale-up verification |
Submerged arc surfacing was selected for this application because of its high deposition rate, deep penetration, and suitability for large-diameter cylindrical surfaces. The process involves a continuously fed consumable electrode and a layer of granular flux that covers the arc and molten pool. For cylindrical rolls, the welding head must be mounted on a rotating fixture or the roll must be indexed to ensure uniform coverage around the circumference. The flux composition and electrode alloy content are critical in determining the hardness, wear resistance, and bonding quality of the surfacing layer.
The simulation test rolls of 140 mm and 370 mm diameters served as process development and qualification tools. The smaller 140 mm roll allowed rapid iteration of process parameters, while the 370 mm roll provided scale-up validation. This staged approach is a sound engineering practice that minimizes the risk of process failure on production components.
Quality Assessment and Engineering Practice
Quality control for roll surfacing involves several critical checkpoints. Pre-weld preparation includes thorough cleaning of the base surface to remove scale, rust, and contaminants that could cause porosity or lack of fusion. The preheat temperature must be carefully controlled to minimize residual stress and cracking susceptibility, particularly for high-carbon or alloyed base metals. Post-weld inspection typically includes visual examination for surface defects, hardness profiling to verify layer uniformity, and magnetic particle or dye penetrant testing for surface cracks.
The success of this work demonstrates that submerged arc surfacing is a viable and economical approach for roll restoration in hot rolling mills. The key engineering insight is that process development should proceed through simulation testing before full-scale application, and that the specific geometry and operating conditions of each roll type require tailored process parameters. The 1450 mill roll surfacing project at the Second Heavy Machinery Works provided valuable practical experience that informed subsequent surfacing applications in the heavy machinery industry.
Study Insights
This paper represents a classic example of applied welding engineering research, where the primary goal is the practical restoration of industrial components. The methodology of developing the process on simulation rolls before applying it to production equipment is a lesson that remains relevant today. From a metallurgical perspective, the selection of low-alloy hardfacing electrodes provides a good balance of hardness and toughness for roll applications, where the surfacing layer must resist both abrasion and impact. The work underscores the importance of process adaptability to component geometry and the value of staged qualification in surfacing welding projects. For engineers working in maintenance and refurbishment of heavy equipment, this paper provides a practical framework for evaluating and implementing surfacing solutions for cylindrical components operating under severe wear conditions.