Application of Novel Nickel-Based High Temperature Alloy Welding Electrode on Fixed Width Press Modules

Literature Overview

This publication, appearing in the Welding journal (2009), documents the industrial application of a newly developed nickel-based high-temperature alloy welding electrode for repairing and hardening fixed-width press modules at Baosteel Hot Rolling Mill. The collaborative research involved Wang Guanghuan from Shanghai Jiao Tong University School of Materials Science and Engineering, Jiang Guangbiao from Baosteel Hot Rolling Division, and Jiang Guangjian from Baosteel Equipment Maintenance Company. The study bridges academic materials development with real-world industrial maintenance challenges in the steel rolling sector.

Core Technical Content

Fixed-width press modules in hot strip mills experience extreme operating conditions characterized by temperatures exceeding 900°C, severe mechanical loading from rolling forces, and thermal cycling from repeated contact with hot strip steel. Conventional repair methods using standard high-speed steel welding consumables result in rapid degradation of the working surface, with typical service intervals of only 20-30 days before resurfacing is required. The nickel-based alloy electrode was specifically formulated to address these combined thermal and mechanical demands.

Alloy Design Philosophy

The nickel-based high-temperature alloy electrode incorporates a matrix of austenitic or austenitic-ferritic structure stabilized by alloying additions such as chromium, molybdenum, tungsten, and cobalt. These elements collectively contribute to:

• Retention of hardness at elevated temperatures through solid solution strengthening and precipitation hardening
• Resistance to thermal fatigue cracking through enhanced creep strength
• Oxidation resistance through chromium oxide scale formation
• Thermal conductivity sufficient to prevent localized overheating

The deposited overlay layer typically achieves a hardness of 40-48 HRC at room temperature with retention of 35-42 HRC at 600°C, representing a substantial improvement over conventional repair materials.

Application Methodology

The welding procedure emphasizes low heat input to minimize thermal distortion of the press module while ensuring complete fusion at each layer interface. The DCEP polarity provides deeper penetration, which is advantageous for repairing worn surfaces without excessive buildup of the overlay layer.

Defect Analysis and Quality Control

The primary failure modes observed in nickel-based overlay layers on press modules include:

1. Intergranular cracking: Caused by excessive interpass temperature allowing grain boundary precipitation of brittle phases. Mitigation involves strict temperature control and possibly adding boron to the electrode composition to segregate to grain boundaries in a non-brittle form.
2. Hot cracking: Associated with low melting point eutectics at grain boundaries during solidification. The nickel-rich composition reduces this susceptibility compared to cobalt-based alternatives, but careful dilution control remains essential.
3. Spalling and delamination: Results from high residual stresses combined with thermal cycling in service. Countermeasures include stress-relief annealing after welding and optimizing the coefficient of thermal expansion match between the overlay and substrate.
4. Excessive dilution: When the nickel-based alloy dilutes excessively with the carbon steel substrate, the resulting layer loses its high-temperature properties. Multi-pass welding with reduced heat input per pass helps maintain the alloy composition within the target range.

Engineering Practice Integration

At Baosteel's hot rolling facility, the application of this nickel-based electrode resulted in a documented extension of press module service life from approximately 25 days to over 60 days under identical operating conditions. This improvement translates to significant reductions in unplanned downtime, maintenance labor costs, and replacement material consumption. The economic analysis demonstrated a payback period of less than three months for the increased electrode cost.

A critical aspect of the field application was the development of a standardized welding procedure specification (WPS) tailored to the specific geometry and material condition of each press module type. The WPS incorporated detailed requirements for surface preparation, preheat application, welding sequence, and post-weld inspection. Non-destructive testing using magnetic particle inspection (MT) was performed after each pass to detect surface-breaking defects that could propagate under service loading.

The study also highlights the importance of consumable qualification testing. Before deployment in production, the electrode underwent extensive qualification including chemical composition verification, hardness profiling, high-temperature oxidation testing, thermal fatigue cycling, and impact testing at both room temperature and elevated temperature. These qualification data provided the technical basis for the welding procedure and established acceptance criteria for field welders.

Key Reflections and Study Insights

This case study demonstrates that the development of specialized welding consumables must be driven by specific industrial needs rather than purely academic considerations. The nickel-based electrode was not a generic product but was formulated to address the exact failure mechanisms observed in Baosteel's press modules. This problem-oriented approach to materials development is a model for engineering research that seeks genuine industrial impact.

The success of this application also underscores the principle that overlay welding is not merely a surface treatment but a comprehensive engineering solution requiring integration of materials selection, process design, quality control, and field application management. The collaboration between university researchers and industrial practitioners exemplifies the productive partnership that drives technological advancement in manufacturing.