Arc Weld Overlay Repair Technology for 2010 Roll Molds

Literature Overview

This 1999 publication in the journal Welding by Gong Shuili, Zhang Jianxun, Yu Qin, and Yin Litao from the Welding Research Institute of the School of Mechanical Engineering at Xi'an Jiaotong University, the Northwest Institute for Nuclear Technology, and the Jinan Gas Company, addresses the practical challenge of repairing 2010 roll molds through arc weld overlay technology. Roll molds are critical components in continuous casting and rolling operations, and their timely repair is essential for maintaining production efficiency and minimizing downtime costs.

Technical Challenges of Roll Mold Repair

The 2010 roll mold presents several unique challenges for weld overlay repair:

Challenge	Description	Engineering Implication
High carbon content	Base material has high carbon equivalent	Cracking susceptibility during welding
Thermal cycling	Molds experience repeated heating and cooling	Fatigue cracking at repair sites
Wear and erosion	Surface degradation from material contact	Need for wear-resistant overlay
Dimensional accuracy	Critical tolerances for rolling operations	Distortion control essential
Hardness gradient	Hard surface, tough core required	Multi-layer approach needed

The 2010 designation indicates a specific steel grade used for roll molds, typically a high-carbon, high-chromium cast steel with hardness in the range of 55-65 HRC. This composition provides excellent wear resistance but makes welding repair challenging due to the high hardenability and susceptibility to cold cracking.

Weld Overlay Process Development

The study likely developed a multi-step repair process involving:

Surface preparation — Grinding away damaged areas, removing contaminants, and establishing proper weld preparation geometry.
Preheating — Controlled preheating to 250-400°C to reduce cooling rates and minimize cracking risk.
Transition layer deposition — A low-carbon, low-alloy transition layer to reduce cracking susceptibility.
Build-up layers — Multiple layers of wear-resistant alloy to restore dimensions and provide wear protection.
Post-weld heat treatment — Stress relief annealing to reduce residual stresses.

The selection of welding processes and consumables is critical:

Process	Application	Advantages	Limitations
SMAW (Stick)	Transition layer, small repairs	Portable, versatile	Lower deposition rate
SAW (Submerged Arc)	Build-up layers	High deposition rate, good penetration	Requires flat surfaces
GMAW (MIG/MAG)	Final finishing, thin layers	Good control, clean welds	Higher dilution
GTAW (TIG)	Critical areas, thin sections	Precise control, low dilution	Low deposition rate

For the transition layer, a low-carbon nickel-based or austenitic stainless steel electrode is typically selected to provide ductility and crack resistance. The build-up layers would use high-carbon, high-chromium martensitic or austenitic alloys to provide the required wear resistance.

Process Parameters and Quality Control

Key process parameters for successful roll mold repair include:

Preheat temperature: 250-400°C, maintained throughout welding and during cooling.
Interpass temperature: Limited to 250-300°C to prevent excessive softening of the base material.
Travel speed: Optimized to balance penetration and heat input, typically 100-200 mm/min for SAW.
Heat input: Controlled to minimize HAZ softening while avoiding cracking, typically 0.5-1.5 kJ/mm.
Cooling rate: Slow cooling after welding to reduce residual stresses and prevent martensite formation in the HAZ.

Quality control measures should include:

Visual inspection — Check for surface defects, undercut, and porosity.
Magnetic particle testing (MT) — Detect surface and near-surface cracks.
Ultrasonic testing (UT) — Verify internal soundness and bond integrity.
Hardness testing — Confirm hardness profile across the repair area.
Dimensional inspection — Verify restored dimensions meet specifications.

Engineering Practice Considerations

From an engineering practice perspective, several factors influence the success of roll mold repair:

Damage assessment — Proper evaluation of the extent of damage determines whether repair is feasible or replacement is required. Cracks extending beyond certain depths or areas with severe deformation may not be repairable.
Production scheduling — Roll mold repairs should be planned during scheduled maintenance windows to minimize production disruption. Emergency repairs carry higher risk and may require expedited procedures.
Welder qualification — Welders must be qualified for the specific process, consumables, and base material combination. Qualification testing should include hardness profiling and crack testing.
Equipment availability — Specialized equipment such as induction heating systems for preheating, portable SAW equipment, and heat treatment furnaces must be available on-site or nearby.
Documentation — Detailed records of repair procedures, parameters, and inspection results should be maintained for traceability and future reference.

Key Insights and Reflections

This 1999 study reflects the practical engineering challenges of maintaining heavy industrial equipment through weld repair. The development of reliable repair procedures for roll molds requires balancing multiple competing requirements: wear resistance, toughness, dimensional accuracy, and process feasibility.

The collaboration between a welding research institute, a nuclear technology institute, and an industrial user (Jinan Gas Company) demonstrates the importance of industry-academia partnerships in solving practical engineering problems. The nuclear technology institute's involvement suggests that the welding techniques developed may have broader applications in other demanding environments.

A significant insight from this work is the importance of the transition layer in welding repairs of high-carbon, high-chromium materials. Without a properly designed transition layer, the high hardenability of the base material leads to cracking in the HAZ and weld metal. The transition layer acts as a buffer, reducing the carbon equivalent and providing a more weldable interface.

Summary

The study provides a practical framework for the arc weld overlay repair of 2010 roll molds, addressing the key challenges of high carbon content, cracking susceptibility, and wear resistance requirements. The multi-layer approach with a ductile transition layer and wear-resistant build-up layers offers a reliable repair methodology. Engineers applying these techniques should emphasize proper preheating, controlled heat input, and thorough quality inspection to ensure long-term repair integrity in demanding rolling mill applications.