Hardfacing Materials and Applications for Rolling Mill Guide Plates

Literature Overview

The 1996 publication by Wang Guoping from Anhui Institute of Technology addresses the selection and application of hardfacing materials for rolling mill guide plates, which are critical components in hot and cold rolling mills that direct and align the strip as it passes through the mill. Guide plates are subjected to extreme conditions including high temperatures (up to 900–1100°C in hot rolling), severe abrasive wear from the hot strip surface, and impact loading from strip misalignment. The selection of appropriate hardfacing materials and processes is essential for extending service life and reducing maintenance downtime.

Service Conditions and Failure Modes

Rolling mill guide plates experience a unique combination of loading conditions that must be considered when selecting hardfacing materials. The following table summarizes the key service parameters and associated failure modes:

The primary failure modes are abrasive wear at the strip contact surface, thermal fatigue cracking from cyclic heating and cooling, and impact damage from strip misalignment or jamming.

Hardfacing Material Selection

The study reviews several classes of hardfacing materials suitable for rolling mill guide plates, organized by their primary mechanism of wear resistance:

Ceramic-Reinforced Hardfacing Alloys

These materials contain a high volume fraction (15–35%) of hard ceramic particles such as Cr3C2, TiC, WC, or SiC dispersed in a tough matrix. They offer excellent abrasive wear resistance but are susceptible to thermal shock cracking. Typical compositions include:

Carbide-Precipitating Hardfacing Alloys

These materials rely on the in-situ formation of hard carbides during solidification or post-weld heat treatment. They offer good wear resistance and better thermal shock resistance than ceramic-reinforced materials. Examples include high-carbon Cr13-Mo alloys and Ni-Cr-C alloys.

High-Temperature Hardfacing Alloys

For hot rolling applications, the hardfacing material must retain hardness and strength at elevated temperatures. The study identifies several suitable materials:

The retained strength ratio is defined as the hardness at elevated temperature divided by the hardness at room temperature. Materials with higher retained strength ratios are preferred for hot rolling applications.

Welding Process Selection

The choice of welding process for rolling mill guide plate hardfacing depends on the geometry, production volume, and required quality level:

For most rolling mill guide plate applications, GMAW or SAW is preferred due to its balance of productivity and quality. PTA is reserved for critical applications where low dilution and high-quality overlay are required.

Engineering Practice Cases

The study presents several case studies from Chinese steel mills. In one case, a hot rolling mill guide plate with a Stellite 6 overlay layer achieved a service life of 45 days before replacement, compared to 12 days for the unhardfaced plate. The overlay layer was applied using GMAW with a multi-pass strategy to minimize dilution. The first pass had approximately 25% dilution, and subsequent passes progressively reduced dilution to below 10% in the final pass. The overlay thickness was 6–8 mm, with a post-weld machining allowance of 2 mm.

In another case, a cold rolling mill guide plate with a Cr3C2-reinforced hardfacing layer experienced thermal fatigue cracking after only 15 days of service. Investigation revealed that the hardfacing material had insufficient thermal shock resistance for the application. The corrective action involved switching to a Ni-Cr-C based alloy with better thermal shock resistance, which achieved a service life of 60 days.

Study Insights and Implications

This 1996 study by Wang Guoping provides a practical and comprehensive guide to hardfacing material selection for rolling mill guide plates. The systematic comparison of different material classes, welding processes, and service conditions offers valuable guidance for engineers in the steel industry. The key insight is that material selection must be driven by the specific service conditions rather than by generic hardness values. A material with high room-temperature hardness may be inferior to a material with moderate hardness but better high-temperature strength and thermal shock resistance in a hot rolling application. The study also emphasizes the importance of multi-pass welding strategies to minimize dilution and achieve the target overlay composition, which is a principle that remains relevant in modern welding practice. For engineers involved in rolling mill maintenance and hardfacing specifications, this literature serves as a practical reference for making informed material and process decisions.