Numerical Simulation of Hardfacing Process for Hydraulic Support Cylinder Piston Rods

Literature Overview

This 2021 paper by Zhang Jin and colleagues from Anhui University of Science and Technology presents a finite element analysis (FEA) of the temperature field distribution during hardfacing of hydraulic support cylinder piston rods. Published in Hot Working Technology (Vol. 50, No. 9, pp. 122–124), the study uses ANSYS software with APDL programming and element birth-death techniques to simulate transient thermal analysis under three preheat conditions: ambient temperature (20°C), 150°C, and 300°C. The primary objective is to predict the temperature field distribution and evaluate the effect of preheat on the formation of quenched hard structures in the weld zone.

Simulation Methodology

The numerical model employs the finite element method with a transient thermal analysis approach. The element birth-death technique is used to simulate the sequential deposition of hardfacing layers, where each layer is "born" (activated) at the moment of welding and "dies" (deactivated) after the thermal analysis of that pass is complete. This approach accurately captures the thermal history of each deposition layer while managing computational efficiency.

Temperature Field Distribution Results

The simulation results reveal distinct temperature field patterns under the three preheat conditions. At ambient temperature (20°C), the welding zone experiences the highest thermal gradient, with peak temperatures concentrated in a narrow band around the weld. The rapid cooling from this high peak temperature creates conditions favorable for martensitic transformation, resulting in quenched hard structures in the weld metal and heat-affected zone (HAZ).

At 150°C preheat, the temperature field is more broadly distributed, with lower peak temperatures and a wider thermal affected zone. The reduced thermal gradient slows the cooling rate, partially mitigating the formation of quenched structures. At 300°C preheat, the temperature field is even more uniform, with the lowest peak temperatures and the broadest thermal affected zone. The significantly reduced cooling rate substantially suppresses martensitic transformation, producing softer microstructures in the weld and HAZ.

Engineering Analysis and Process Optimization

The simulation results have direct implications for the hardfacing process design of hydraulic support cylinder piston rods. These components operate under high cyclic loading in mining environments, where the hardfacing deposit must provide wear resistance while maintaining adequate toughness to resist impact and fatigue. The quenched hard structures that form under ambient temperature welding are brittle and susceptible to cracking under cyclic loading.

Optimal Preheat Selection

For hydraulic support cylinder piston rods, the optimal preheat temperature depends on the specific service conditions. For applications requiring maximum wear resistance where impact loading is minimal, ambient temperature welding with a hardfacing consumable designed to resist cracking may be acceptable. For applications involving significant impact or cyclic loading, a preheat of 150–300°C is recommended to reduce quenched structure formation and improve toughness.

The simulation also highlights the importance of controlling interpass temperature. Even with preheat, if the interpass temperature rises too high during multi-layer deposition, the thermal cycles can soften previously deposited layers, reducing the overall wear resistance of the deposit. A typical interpass temperature control range of 100–250°C is recommended for hardfacing of piston rods.

Thermal Stress and Distortion Considerations

Although the paper focuses on temperature field analysis, the temperature gradients revealed by the simulation directly correlate with thermal stress development. The steep thermal gradients at ambient temperature welding create significant thermal stresses that can cause distortion of the piston rod and contribute to cracking. The more uniform temperature distribution at higher preheat temperatures reduces thermal stress magnitude, which is beneficial for dimensional accuracy and crack resistance.

For engineers implementing this hardfacing process, the following practical recommendations emerge:

• Use preheat of at least 150°C for piston rods with wall thickness exceeding 25 mm
• Control interpass temperature between 100–250°C to balance toughness and hardness
• Use multi-pass welding with lower heat input per pass to reduce peak temperatures
• Perform post-weld stress relief annealing at 550–650°C to eliminate residual stresses
• Verify hardness profile across the deposit thickness to confirm uniform microstructure

Summary

The Zhang et al. numerical simulation study provides valuable predictive insights into the temperature field behavior during hardfacing of hydraulic support cylinder piston rods. The clear demonstration that preheat reduces quenched hard structure formation offers a straightforward process control lever for improving weld toughness and crack resistance. For engineers in the mining equipment manufacturing sector, this simulation-based approach enables process optimization before physical trials, reducing development costs and accelerating the qualification of hardfacing procedures for critical hydraulic components. The findings reinforce the principle that thermal management—through preheat, interpass temperature control, and heat input selection—is the primary means of controlling microstructure and properties in hardfacing deposits.