Accurate measurement of interfacial heat transfer during casting solidification is crucial for optimizing metal solidification processes. The gap between the mold wall and the casting surface plays a significant role in heat transfer and cooling rates. In this study, two innovative fiber-optic sensors are employed to measure real-time mold gaps and thermal profiles during the solidification of A356 aluminum in a permanent mold casting. The experimental setup consists of a specially designed mold system made of unheated, uncoated tool steel, which facilitates easy installation of the fiber-optic sensors. An Extrinsic Fabry-Perot interferometric (EFPI) sensor is utilized to monitor the evolving gap between the mold wall and the casting surface. This method relies on the unique concept of using molten metal as the second reflection interface for gap measurements. The EFPI gap measurements exhibit high accuracy and precision, with a maximum error of only 2μ m when compared to physical measurements. Simultaneously, a stainless steel-encased fiber utilizing the Rayleigh backscattering (RBS) technique is deployed across the mold wall and cavity to achieve real-time temperature measurements with a spatial resolution of 0.65 mm. The study demonstrates that leveraging high-resolution temperature profiles and gap evolution measurements enhances understanding of heat transfer dynamics at the mold-metal interface, particularly valuable for complex-shaped castings and continuously cast metals. Additionally, the ability to measure the cast shape exiting a continuous casting mold during operation presents a novel tool for real-time product quality monitoring and process safety enhancement by detecting conditions that may lead to slab cracking and breakouts.


Materials Science and Engineering

Second Department

Electrical and Computer Engineering

Keywords and Phrases

Aluminum casting; distributed temperature measurement; extrinsic Fabrya-Perot interferometer (EFPI); gap measurement; interfacial heat transfer; molten metal; optical fiber sensors; optical frequency-domain reflectometry (OFDR); Rayleigh backscattering (RBS)

International Standard Serial Number (ISSN)

1557-9662; 0018-9456

Document Type

Article - Journal

Document Version


File Type





© 2023 Institute of Electrical and Electronics Engineers, All rights reserved.

Publication Date

01 Jan 2023