In brief

Researchers found that their thermo-metallurgical model for hybrid laser arc welding accurately predicted the mechanical properties of welded chromium-molybdenum steel for industrial applications.

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Metallic and mathematical worlds collide

7 Sep 2023

A specially designed computational model guides the development of next-generation metal welding processes by predicting how heat affects the strength of welded joints.

A fiery ancient metal-working technique that dates back thousands of years is now getting a modern computing boost. Joining metals together by welding has roots in the making of tools and weapons by early civilisations. Today, modern welding techniques such as hybrid laser arc welding (HLAW) are used extensively in applications ranging from shipbuilding to car manufacturing and beyond.

HLAW is typically used to fuse chromium-molybdenum steel plates and lends itself to automation, making welding on industrial scales faster and more cost-effective. Despite its potential, it remains difficult to predict the strength and integrity of joints made by HLAW, a gap which experts say that computer simulations can help bridge.

“Simulations can accelerate the development of hybrid welding, enabling us to understand the complex physical phenomena that may arise,” said Youxiang Chew, from A*STAR.

Chew and colleagues at A*STAR’s Singapore Institute of Manufacturing Technology (SIMTech), with the support of the Singapore Maritime Institute, devised a computer model to make reliable predictions on how chromium-molybdenum steel plates change—such as which areas would melt and how the welded joints would solidify—during HLAW by considering factors like heat and material properties.

“The model helps us analyse the predicted solidification rates and phases to corroborate our experimental measurements,” explained Chew. “This correlation enables us to improve the mechanical performance of welds and their consistency across the welded areas, also known as the fusion zones.”

The researchers compared their computationally generated predictions with data from real world experiments which tested the strength of welded materials through various means, such as pressing, pulling and bending. They found that the fusion zones outperformed the rest of the material in terms of strength, with unwelded areas succumbing to damage first.

“The formation of refined grains during welding created more grain boundaries, acting like barriers to deformations and thereby increasing the overall strength and hardness of the welded area,” explained Chew. However, he cautioned that while this makes the material stronger, it can also increase brittleness and susceptibility to fracture under repeated stress.

The team’s innovative model validated the benefits of hybrid welding techniques, while also illuminating parameters such as cooling rates that can be tailored for brittle, difficult-to-weld materials. The researchers have initiated the commercialisation of their technology by filing a technical disclosure on their hybrid welding method.

The researchers are currently exploring other hybrid welding techniques to enhance additive manufacturing processes. “By applying various hybrid laser processes, our aim is to widen the range of parameters within which additive manufacturing processes can operate, leading to increased flexibility and precision,” concluded Chew.

Since the study in the Singapore Institute of Manufacturing Technology (SIMTech), Chew has joined the Advanced Remanufacturing and Technology Centre (ARTC) as a Principal Scientist.

The A*STAR-affiliated researchers contributing to this research are from the Singapore Institute of Manufacturing Technology (SIMTech).

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Du, Z., Sun, X., Ng, F.L., Chew, Y., Tan, C., et al. Thermo-metallurgical simulation and performance evaluation of hybrid laser arc welding of chromium-molybdenum steel. Materials & Design 210, 110029 (2021).│article

About the Researcher

Youxiang Chew has over nine years of experience in Laser Directed Energy Deposition (LDED) technology, focusing on processes, residual stress modelling and the integration of machine learning to optimise laser deposition toolpaths. Chew’s other research interests include developing high entropy alloys and bulk spatially patterned heterostructured multimaterials parts using LDED. Beyond the LDED process, Chew is now looking into new process innovation by combining different advanced manufacturing processes for multimaterial processing. The group is also exploring hybrid DED processes and new friction stir processing for repair and remanufacturing, aiming to streamline the manufacturing of high value components.

This article was made for A*STAR Research by Wildtype Media Group