Cladding Technology for 1450 Rolling Mill Rolls

Literature Overview

This paper, published in 1992 in the journal "Welding" (焊接), was authored by Tu Xiaodong from the Second Heavy Machinery Factory (第二重型机器厂). The study addresses the cladding technology applied to 1450 hot rolling mill work rolls, a critical component in steel production facilities. The 1450 rolling mill refers to a two-high stand hot rolling mill with a roll diameter of 1450 mm, typically used for rolling medium and heavy plate products. The work rolls in such mills are subjected to extreme thermal and mechanical loading conditions, making their cladding technology a key factor in production efficiency and product quality.

Core Technical Content

Hot rolling mill work rolls experience a combination of severe operating conditions, including high temperatures (up to 1000°C in contact with hot steel), high contact pressures (exceeding 2000 MPa), thermal cycling, and abrasive wear from oxide scale and steel debris. The cladding layer on work rolls must therefore exhibit excellent wear resistance, thermal fatigue resistance, and bonding strength to the roll body material.

The cladding technology for 1450 rolling mill rolls typically involves the application of a multi-layer overlay system. The first layer, known as the transition layer or bonding layer, is designed to provide strong metallurgical bonding with the roll body material while accommodating the thermal expansion mismatch between the roll body and the wear layer. The subsequent layers, known as the wear layers, are composed of high-carbon, high-chromium alloys with excellent abrasion resistance.

The researchers at the Second Heavy Machinery Factory developed a comprehensive cladding process for 1450 rolling mill rolls that addressed the unique challenges of this application. The process involved careful selection of cladding materials, optimization of welding parameters, and implementation of rigorous quality control procedures to ensure consistent overlay performance.

Process Parameters and Technical Analysis

The following table summarizes the cladding process parameters and material specifications for 1450 rolling mill rolls:

The cladding process for rolling mill rolls requires careful control of heat input to minimize distortion and maintain dimensional accuracy. The rolls are typically clamped in a specialized fixture that allows for controlled rotation during the welding process. Multiple passes are applied in a systematic pattern to ensure uniform coverage and minimize residual stress.

The researchers conducted extensive testing of the cladding layers, including hardness profiling, microstructural examination, and wear testing. The hardness profile typically showed a gradient from the roll body (approximately 40 HRC) through the bonding layer (45-50 HRC) to the wear layer (50-55 HRC). This gradient helps to accommodate the thermal expansion mismatch and reduces the risk of spalling or delamination.

Defect Analysis and Countermeasures

Cladding of rolling mill rolls is susceptible to several critical defects that can lead to premature failure:

The most critical defect for rolling mill roll cladding is delamination, which occurs when the cladding layer separates from the roll body under operational loading. This defect is particularly dangerous because it can lead to sudden, catastrophic failure of the roll, causing production downtime and potential safety hazards. The researchers developed a systematic approach to preventing delamination, including careful surface preparation of the roll body, optimization of the bonding layer composition, and implementation of controlled cooling procedures.

The bonding layer composition is critical for preventing delamination. A low-carbon nickel-based alloy provides excellent bonding characteristics with both the roll body material and the high-carbon wear layer. The nickel content promotes austenitic transformation at the interface, which accommodates thermal expansion differences and reduces residual stress. The low carbon content minimizes the formation of brittle carbides at the interface, which would otherwise act as crack initiation sites.

Engineering Practice Implications

The cladding technology for 1450 rolling mill rolls has significant implications for steel mill operations. Properly clad rolls can extend service life by 2-3 times compared to unclad rolls, reducing replacement frequency and production downtime. The improved surface quality of clad rolls also leads to better surface finish on rolled products, reducing downstream processing requirements.

However, the cladding process requires significant investment in equipment and training. The specialized welding equipment, roll fixtures, and heat treatment facilities represent a substantial capital expenditure. Additionally, the process requires skilled welders who are trained in the specific techniques required for roll cladding. Quality control procedures must be rigorous, with non-destructive testing (NDT) performed on every roll before release for service.

The researchers also emphasized the importance of roll management procedures in maximizing the benefit of cladding technology. This includes proper storage conditions to prevent corrosion, careful handling to avoid surface damage, and systematic tracking of roll usage to ensure timely replacement or reclamation.

Study Insights and Reflections

This study provides valuable insights into the practical challenges of cladding large-diameter rolling mill rolls. The development of a comprehensive cladding process that addresses the unique requirements of this application demonstrates the importance of tailoring technology to specific industrial needs. The multi-layer approach, with a carefully designed bonding layer and wear layer, represents a sophisticated solution to the fundamental challenge of joining dissimilar materials with different thermal and mechanical properties.

The work also highlights the importance of process development and optimization in achieving reliable cladding performance. The systematic approach to parameter selection, material selection, and quality control demonstrated in this study is essential for achieving consistent results in production environments. The emphasis on defect prevention and quality assurance reflects the critical nature of rolling mill rolls in steel production operations.

In conclusion, the cladding technology for 1450 rolling mill rolls represents a mature and well-established industrial application that continues to evolve with advances in materials science and welding technology. The research presented in this paper provides a comprehensive overview of the technical challenges and solutions associated with this application, offering valuable guidance for engineers working in the steel rolling industry.