Surfacing Composite Manufacturing of Discharge Rolls for Large Hot Rolling Width-Setting Press

Literature Overview

This 2013 paper by Zhong Yi and Zeng Yibin, published in Journal of Plasticity Engineering, addresses a critical industrial problem: the severe thermo-mechanical degradation of discharge rolls (also known as discharge shafts or delivery rolls) in large hot rolling width-setting presses. Operating in environments exceeding 800°C with direct contact with red-hot steel slabs, these rolls suffer from thermal fatigue cracking, cold-to-hot fatigue, and metal-to-metal abrasive wear. The authors developed a nitrogen-alloyed hardfacing flux-cored wire and a composite manufacturing process to extend roll life significantly. This work is highly relevant to engineers in the steel rolling industry and those involved in the hardfacing of high-temperature components.

Problem Definition and Failure Analysis

The discharge rolls in hot rolling width-setting presses are subjected to extreme and cyclic thermal loading. The repeated contact with red-hot steel slabs (above 800°C) causes alternating expansion and contraction, leading to thermal fatigue cracking on the roll surface. Simultaneously, the high-temperature sliding contact between the roll and the slab produces severe metal-to-metal abrasive wear. Conventional roll materials and standard hardfacing consumables are unable to withstand this combined thermo-mechanical service, resulting in short service intervals and frequent downtime for roll replacement or resurfacing.

Consumable Development and Microstructure

The authors developed a nitrogen-alloyed hardfacing flux-cored wire specifically designed for this application. The nitrogen alloying serves multiple functions: it stabilizes the martensitic structure against softening at elevated temperatures, promotes the formation of hard alloy compounds (nitrides and carbonitrides), and enhances the overall hardness retention at service temperatures.

The resulting surfacing layer microstructure consists of martensite with a small amount of ferrite and dispersed alloy compounds. This combination provides exceptional resistance to high-temperature softening, thermal fatigue cracking, and metal-to-metal wear.

Process Specification and Performance Results

The authors developed a rational surfacing process specification tailored to the geometry and service conditions of the discharge rolls. The surfacing composite manufacturing process combines a tough base roll with a wear-resistant, thermally stable surfacing layer, achieving a composite structure that outperforms either material alone.

The practical results are compelling: the surfacing-composite manufactured discharge rolls achieved service lives of up to six months without thermal fatigue cracking and with minimal metal-to-metal wear. This represents a substantial improvement over conventional approaches, translating directly into reduced maintenance costs, improved production continuity, and enhanced safety in the hot rolling mill environment.

Engineering Practice Integration

From an engineering practice perspective, this study exemplifies the systems approach to solving complex tribological problems. The solution is not merely a harder material but a carefully designed combination of consumable chemistry, process parameters, and composite architecture. The nitrogen alloying approach is particularly noteworthy because nitrogen is a potent interstitial alloying element that can dramatically alter the properties of steels and surfacing alloys without introducing heavy metal costs.

For engineers in the steel industry or related heavy industries, this case study demonstrates the value of application-specific consumable development. Off-the-shelf hardfacing consumables often fail to meet the demands of extreme service conditions, and the development of tailored alloys and processes can yield dramatic performance improvements.

Study Insights and Reflections

The most significant insight from this work is the demonstration that nitrogen alloying can be effectively leveraged in hardfacing flux-cored wires to address high-temperature wear and thermal fatigue challenges. This approach offers a cost-effective alternative to cobalt- or tungsten-based hardfacing alloys, which are prohibitively expensive for large-scale industrial applications. The six-month service life achieved is a testament to the effectiveness of the composite manufacturing approach and provides a benchmark for evaluating other hardfacing solutions in similar applications. For engineers involved in pipe and fitting hardfacing, the principles of nitrogen alloying and composite manufacturing demonstrated here can be adapted to address high-temperature wear challenges in components such as furnace rollers, conveyor rollers, and kiln wear plates.