Combined Roller Body Surfacing Device for Steel Rolling Mill Applications

Literature Overview

This 2005 paper by Wang Yinjun from the Technical Center of Shanghai Meishan Co., Ltd., published in Mining Machinery, describes a combined roller body surfacing device designed for the hardfacing of steel rolling mill rolls. The paper focuses on the equipment configuration, process technical requirements, and post-weld heat treatment procedures for multi-process surfacing of squeeze rolls and roller mill components.

Equipment and Process Description

Combined Roller Surfacing Device Architecture

The combined device integrates multiple surfacing processes into a single system capable of handling different roller body configurations. Key components include:

Component	Function	Specification
Multi-process welding station	SMAW, SAW, or FCAW surfacing	Configurable for different roller diameters
Preheating furnace	Uniform heating before surfacing	200–400°C, controlled ramp rate
Post-weld heat treatment furnace	Stress relief and tempering	500–650°C, controlled cooling
Roller mounting fixture	Precise positioning and rotation	Accommodates various roller lengths and diameters
Inspection station	Dimensional and NDT verification	MT, UT, dimensional measurement

Process Technical Requirements

The authors outline the following process requirements for roller surfacing:

Base preparation: Surface grinding to remove scale and defects; magnetic particle inspection (MT) of the base material before surfacing
Preheating: Uniform preheating to 250–350°C for medium-carbon and alloy steel rollers; temperature must be maintained throughout surfacing
Surfacing parameters:

Layer thickness: 8–15 mm total, applied in 3–5 passes
Interpass temperature: 250–350°C (not to drop below 200°C)
Welding wire: Hardfacing alloy (typically Cr-Mo or Cr-V type for squeeze rolls)
Current density: 30–50 A/mm² (depending on process)

Post-weld heat treatment (PWHT):

Stress relief: 550–650°C for 2–4 hours per 25 mm wall thickness
Cooling rate: ≤100°C/hour in furnace
Final hardness verification: 50–55 HRC for typical squeeze roll overlays

Multi-Process Integration

The "combined" aspect of the device refers to the ability to switch between different surfacing processes depending on the roller geometry and wear pattern:

Full circumference surfacing: SAW or FCAW with roller rotation
Partial area repair: SMAW or FCAW for localized wear areas
Multi-layer build-up: Sequential application of different alloy compositions for functionally graded surfaces

Engineering Application Context

Application	Roller Type	Overlay Requirement	Typical Hardness
Squeeze rolls (roll compaction)	Pair rolls	High compressive strength, wear resistance	50–58 HRC
Rolling mill backup rolls	Large diameter	High load capacity, surface hardness	45–55 HRC
Finishing rolls	Small diameter	Surface quality, dimensional accuracy	40–50 HRC
Crush rolls	Medium diameter	Impact resistance, abrasion resistance	55–62 HRC

Quality Control Points

The paper emphasizes several critical quality control checkpoints:

Layer interface inspection: After each major layer, MT inspection for interface cracks
Hardness mapping: Grid-pattern hardness testing across the overlay surface
Dimensional verification: Roundness and diameter tolerance after surfacing (typically ±0.5 mm for squeeze rolls)
Residual stress measurement: X-ray diffraction or strain gauge method verification of residual stress levels

Study Insights and Reflections

This paper, while primarily a practical engineering report rather than a fundamental research paper, provides valuable insight into the industrial implementation of roller surfacing technology. Several observations are particularly noteworthy:

The emphasis on post-weld heat treatment as a critical process step reflects the practical reality that residual stress management is often more important than microstructure optimization in heavy-duty roller applications. In my own experience with piping and equipment repair, I have observed that many surfacing failures are attributed to residual stress-driven cracking rather than microstructural inadequacy. The systematic PWHT protocol described here—controlled heating, holding, and cooling rates—is a best practice that should be adopted in all heavy surfacing operations.

The combined device concept addresses a real industrial need: the flexibility to handle different roller types and surfacing requirements without requiring multiple dedicated equipment systems. This is particularly relevant for maintenance shops that service various equipment types and must optimize capital investment.

For piping engineers, the principles described here translate directly to the surfacing of large-diameter pipe spools, flanges, and fittings that require thick overlay deposits. The same concerns about preheating, interpass temperature control, and PWHT apply regardless of whether the component is a mill roll or a large-diameter pipe elbow.