Numerical Simulation and Measurement of Temperature and Stress Fields in Hot Rolling Roll Overlay Welding

Literature Overview

This 2014 paper by Chen Xueli, Zhang Zhiling, and Hui Xiangjun investigates the temperature field and stress field distribution during overlay welding of hot rolling mill rolls through combined numerical simulation and experimental measurement. Published in Hot Working Technology, the research addresses the critical challenge of predicting and controlling residual stresses in roll overlay operations, where stress management directly impacts roll service life and surface integrity.

Technical Framework

Hot rolling mill work rolls are subjected to extreme thermal and mechanical loads during service, necessitating periodic resurfacing through overlay welding. The overlay process introduces significant residual stresses that, if not properly managed, can lead to surface cracking, spalling, and premature roll failure. This research employs finite element analysis coupled with experimental thermocouple and strain gauge measurements to develop a comprehensive understanding of the thermal-mechanical behavior during roll overlay welding.

Numerical Simulation Approach

The simulation model incorporates the following key elements:

Model Component	Description	Key Parameters
Thermal model	Transient heat conduction with phase change	Thermal conductivity, specific heat, latent heat
Mechanical model	Elastic-plastic deformation	Yield stress, elastic modulus, thermal expansion
Material model	Temperature-dependent properties	Linearized yield curve, hardening law
Boundary conditions	Roll clamping, symmetry	Constraint stiffness, heat loss coefficients
Heat source model	Moving Gaussian or double-ellipsoidal	Heat input, travel speed, efficiency

Temperature Field Results

The numerical simulation reveals characteristic thermal cycles during overlay welding:

Peak temperature at the weld centerline: 1800-2200°C
Peak temperature at 5 mm from weld center: 800-1200°C
Peak temperature at 20 mm from weld center: 300-500°C
Cooling rate at weld centerline: 50-150°C/s
Cooling rate at 10 mm from weld center: 5-20°C/s

Stress Field Analysis

The residual stress distribution follows a characteristic pattern:

Maximum longitudinal tensile stress at the weld surface: 250-350 MPa
Maximum transverse tensile stress at the weld centerline: 200-280 MPa
Compressive stress in the heat-affected zone at depth: -50 to -150 MPa
Stress relaxation in the base metal beyond 30 mm: near zero

The simulation results show good agreement with experimental measurements, validating the model for use in process optimization.

Process Optimization Based on Simulation Results

The combined simulation and measurement approach enables identification of process parameters that minimize detrimental residual stresses:

Interpass temperature control: Maintaining interpass temperature between 150-250°C reduces peak stress by 20-30% compared to cold welding
Welding sequence optimization: Symmetric multi-pass sequences from the center outward reduce angular distortion by up to 40%
Heat input management: Higher travel speed reduces heat input and consequently reduces residual stress magnitude
Post-weld stress relief: Stress relief at 550-600°C for 1-2 hours reduces residual stress by 60-80%

Engineering Practice Integration

For hot rolling mill operations, the findings from this research directly inform roll maintenance procedures. The typical overlay welding specifications for work rolls include:

Base material: H13 or H21 hot work tool steel
Overlay material: High-speed steel (M2, M35) or cemented carbide
Typical overlay thickness: 15-30 mm for resurfacing
Acceptable residual stress limit: less than 200 MPa to prevent surface cracking

The numerical simulation approach provides a powerful tool for optimizing overlay welding procedures before actual production welding, reducing trial-and-error costs and improving first-pass yield rates.

Study Reflections

This research exemplifies the value of combining computational modeling with experimental validation in welding process development. The agreement between simulated and measured temperature and stress fields validates the approach for use in predicting residual stress states in complex geometries where direct measurement is impractical. For engineers involved in roll maintenance and refurbishment, the ability to predict residual stress distributions enables proactive process adjustments that extend roll service life and reduce unplanned downtime.