Cladding Materials for Rolling Mill Guide Plates and Their Applications

Literature Overview

This technical paper, published in "New Technology and New Process" (1996) by Wang Guoping from Anhui Institute of Technology, addresses the selection and application of overlay welding materials for rolling mill guide plates (guide shoes). Rolling mill guide plates are subjected to extreme conditions including high temperatures, severe abrasive wear from hot steel slabs, and impact loading from the rolling process. The paper provides a comprehensive review of available overlay materials and their performance characteristics in this demanding application.

Service Conditions and Failure Modes

Rolling mill guide plates operate under the following conditions:

Temperature: 500–900°C, depending on the rolling stage (hot rolling)
Contact pressure: 50–200 MPa from the steel slab
Sliding speed: 1–5 m/s relative to the slab surface
Impact loading: From slab deflection and rolling force fluctuations
Environment: Oxidizing atmosphere with iron oxide scale particles

Typical Failure Modes

Failure Mode	Mechanism	Location
Abrasive wear	Sliding contact with iron oxide scale	Working surface
Galling/seizure	Adhesive wear at high temperature	Contact interface
Thermal fatigue cracking	Cyclic heating and cooling	Surface and subsurface
Plastic deformation	Excessive contact stress	Subsurface
Spalling	Combined thermal and mechanical fatigue	Surface layer

Overlay Material Selection

The paper discusses several categories of overlay materials suitable for rolling mill guide plates:

Material Categories and Properties

Material Type	Typical Composition	Hardness (HV)	Service Temperature	Wear Resistance
High-carbon martensitic	C 0.8–1.2%, Cr 5–8%	500–600	< 600°C	Good
High-chromium cast iron	C 3–4%, Cr 25–30%	800–1000	< 800°C	Excellent
Stellite-type (Co-based)	Co 55%, Cr 25%, W 10%	400–500	< 1000°C	Excellent
High-speed steel type	W 10%, Mo 5%, V 5%, Cr 4%	600–700	< 700°C	Very good
Nickel-aluminum bronze	Ni 25%, Al 5%, Cu balance	200–300	< 500°C	Moderate (anti-galling)

Material Selection Guidelines

The selection of overlay material depends on the specific rolling mill application:

Hot strip mill guide plates: High-chromium cast iron or Stellite-type materials are preferred due to their excellent high-temperature wear resistance and thermal fatigue resistance.
Bar and wire mill guide plates: High-carbon martensitic or high-speed steel type materials provide good wear resistance at moderate temperatures.
Slab guide plates: Nickel-aluminum bronze may be used on the counterface to prevent galling, while the guide plate itself uses a hardfacing material.

Welding Process Considerations

Process Selection

Process	Advantages	Limitations
Submerged arc welding (SAW)	High deposition rate, low dilution	Limited to flat and horizontal surfaces
Shielded metal arc welding (SMAW)	Flexible, portable	Low deposition rate, high dilution
Flux-cored arc welding (FCAW)	Good deposition rate, moderate dilution	Requires gas shielding
Plasma transferred arc (PTA)	Low dilution, good surface quality	Equipment cost, limited thickness

For rolling mill guide plates, SAW is the most commonly used process due to the large surface area and the need for thick overlay layers (typically 6–12 mm). The high deposition rate of SAW makes it economical for large production runs.

Key Process Parameters

Parameter	Recommended Value	Purpose
Preheat temperature	200–300°C	Reduce cracking susceptibility
Interpass temperature	< 250°C	Control cooling rate
Heat input	1.5–3.0 kJ/mm	Balance between dilution and fusion
Number of passes	3–5 passes	Achieve required thickness
Post-weld heat treatment	600–650°C × 2h	Relieve residual stress, reduce hardness

Performance Evaluation and Field Results

The paper reports field trial results for several overlay materials on guide plates in hot strip mills:

Material	Service Life (original)	Service Life (overlay)	Improvement Factor
Base steel (Q345)	200–500 hours	—	—
High-carbon martensitic	—	1500–3000 hours	5–8×
High-chromium cast iron	—	3000–6000 hours	10–20×
Stellite 6 type	—	5000–10000 hours	20–40×

The significant improvement in service life demonstrates the economic value of overlay welding for guide plates. Even with the cost of overlay materials and welding labor, the reduced replacement frequency and downtime make overlay a highly cost-effective solution.

Engineering Practice and Recommendations

Based on the paper and practical experience, the following recommendations are provided:

Surface preparation: The base metal surface must be thoroughly cleaned of scale, rust, and contaminants before overlay welding. Shot blasting to Sa 2.5 standard is recommended.
Welding sequence: For large guide plates, a multi-pass welding sequence should be used to minimize distortion. Welding should proceed from the center outward, with each pass laid down as uniformly as possible.
Surface finish: After overlay welding, the surface should be ground to achieve a smooth finish (Ra < 12.5 μm) to reduce initial wear during the run-in period.
Inspection: MT or PT inspection should be performed on the overlay surface to detect cracks before installation. UT should be used to verify bond strength.

Study Insights and Implications

This paper, while dated, provides foundational knowledge on the application of overlay welding to rolling mill guide plates. The material selection guidelines and process parameters remain largely valid today, though modern consumables and advanced welding processes (such as laser cladding and cold spray) may offer improved performance. The key insight is that the selection of overlay material must be matched to the specific service conditions, and that process control is as important as material selection in achieving reliable overlay performance. The economic analysis presented in the paper clearly demonstrates the value of overlay welding as a maintenance and upgrade strategy for critical rolling mill components.