In Situ High-Temperature Raman Spectroscopy Via a Remote Fiber-Optic Raman Probe

This Study Demonstrated for the First Time an in Situ High-Temperature Fiber-Optic Raman Probe to Study the Structure of Glass and Slag Samples at Temperatures Up to 1400 °C. a Customized External Telescope Was Integrated into a Portable Fiber-Optic Raman Probe to Extend the Optical Working Distance to Allow the Probe to Work in a High-Temperature Environment. Three Samples Were Evaluated to Demonstrate the Functionality of the High-Temperature Fiber-Optic Raman Probe. Room Temperature and High-Temperature Raman Spectra Were Successfully Collected and Analyzed. in Addition, a Deconvolution Algorithm Was Used to Identify Peaks in the Spectrum that Could Then Be Related to the Molecular Structure of Components in Each Sample. This Flexible and Reliable High-Temperature Raman Measurement Method Has Great Potential for Various Applications, Such as Materials Development, Composition, and Structure Monitoring during High-Temperature Processing, Chemical Identification, and Process Monitoring in Industrial Production

In Situ and Real-Time Mold Flux Analysis using a High-Temperature Fiber-Optic Raman Sensor for Steel Manufacturing Applications

Continuous Casting in Steel Production Uses Specially Developed Oxyfluoride Glasses (Mold Fluxes) to Lubricate a Mold and Control the Solidification of the Steel in the Mold. the Composition of the Flux Impacts Properties, Including Basicity, Viscosity, and Crystallization Rate, All of Which Affect the Stability of the Casting Process and the Quality of the Solidified Steel. However, Mold Fluxes Interact with Steel during the Casting Process, Resulting in Flux Chemistry Changes that Must Be Considered in the Flux Design. Currently, the Chemical Composition of Mold Flux Must Be Determined by Extracting Flux Samples from the Mold during Casting and Then Processing These Samples Offline to Estimate the Working Chemical Composition And, Therefore, the Expected Properties of the Flux. Raman Spectroscopy Offers an Alternative Method for Performing Flux Analysis with the Potential to Perform Measurements Online during the Casting Process. Raman Spectroscopy Uniquely Identifies Specific Chemical Bonds and Symmetries in the Glassy Flux by Revealing Peaks that Are a Fingerprint of the Vibration Modes of Molecules in the Flux. the Intensities of Specific Peaks in Raman Spectra Can Be Correlated with the Chemical Composition of the Melt and Associated Properties Such as Basicity and Viscosity. This Paper Reports on the First Use of a Portable Fiber-Optic Raman Sensor for in Situ Raman Spectroscopic Measurements of Molten Flux at 1400°C. the Work Demonstrates the Advantages of Fiber-Optic Raman Spectroscopy to Document the Structure and Chemical Composition of Flux Samples at Temperatures Typically Encountered in the Mold during Continuous Caster Operation. Experimental Results Demonstrate that the Composition-Dependent Raman Signal Shifts Can Be Detected at Caster Operating Temperatures, and the Use of High-Temperature Raman Analysis for In-Line Flux Monitoring Shows Significant Promise for the in Situ Detection of Changes in Flux Composition and Physical Properties during Casting

Real-Time Air Gap And Thickness Measurement Of Continuous Caster Mold Flux By Extrinsic Fabry-Perot Interferometer

Mold Flux plays a critical role in continuous casting of steel. Along with many other functions, the mold flux in the gap between the solidifying steel shell and the mold serves as a medium for controlling heat transfer and as a barrier to prevent shell sticking to the mold. This manuscript introduces a novel method of monitoring the structural features of a mold flux film in real-time in a simulated mold gap. A 3-part stainless-steel mold was designed with a 2 mm, 4 mm and, 6 mm step profile to contain mold flux films of varying thickness. An Extrinsic Fabry-Perot Interferometer (EFPI) was installed at each of the three steps in the mold. Mold flux was melted in a graphite crucible at 1400 °C and poured into the instrumented step mold for analysis. Interferograms from the three EFPIs were acquired and processed in real-time to measure the air gap and thickness of each flux film during solidification. Measurements were performed on two different mold flux compositions. Results demonstrate that the proposed system successfully records structural features of the flux film in real-time during cooling. It has a large real-time impact on the process control of steel making and optimizing the quality of steel castings. In addition, the measurement method has potential to monitor crystal nucleation and growth in a variety of crystallizing glass systems

Boosting SNR Of Cascaded FBGs In A Sapphire Fiber Through A Rapid Heat Treatment

This Letter reports the performance of femtosecond (fs) laser-written distributed fiber Bragg gratings (FBGs) under high-temperature conditions up to 1600°C and explores the impact of rapid heat treatment on signal-to-noise ratio (SNR) enhancement. FBGs are essential for reliable optical sensing in extreme temperature environments. Comprehensive tests demonstrate the remarkable performance and resilience of FBGs at temperatures up to 1600°C, confirming their suitability for deployment in such conditions. The study also reveals significant fringe visibility improvements of up to ∼10 dB on a 1-m-long sapphire optical fiber through rapid heat treatment, representing a first-time achievement to the best of our knowledge. These enhancements are vital for improving the SNR and overall performance of optical fiber systems in extreme temperatures. Furthermore, the research attains long-term stability for the cascaded FBGs over a 24-hr period at 1600°C. This research expands our understanding of the FBG behavior in high-temperature environments and opens avenues for developing robust optical fiber systems for energy, aerospace, oil and gas, and high-temperature distributed sensing applications

Temperature Monitoring in the Refractory Lining of a Continuous Casting Tundish using Distributed Optical Fiber Sensors

This Article Explores the Prospects of using Spatially Distributed Optical Fiber Temperature Sensors based on Rayleigh Optical Frequency Domain Reflectometry (OFDR) Technology in the Continuous Casting of Molten Steel. the Measurement Capability of the Optical Fiber Sensors in a Simulated Steelmaking Environment Was Demonstrated using a Mock Refractory-Lined Tundish, Which Was Fabricated In-House. Single-Mode Optical Fibers, Contained in Protective Stainless-Steel Tubing, Were Embedded in the Refractory Lining of the Mock Tundish. the Instrumented Tundish Was Preheated Up to a Temperature of 960 °C (Recorded at the Surface of the Working Lining) Before the Molten Steel Pour. a Low-Alloy Steel (AISI 4140 Grade) Was Melted in a 200 Lb (90.7 Kg) Coreless Induction Furnace and Was Poured into the Instrumented Preheated Tundish. the Embedded Optical Fiber Sensors Were Used to Measure the Temperature Distribution in the Castable Lining during the Preheating Process of the Tundish and during its Contact with Molten Steel. Temperatures Were Metered with a Spatial Resolution of 0.65 Mm Along the Embedded Optical Fibers. the Measurements Were Recorded with an Update Rate of 1 Hz. the Maximum Temperature Recorded by the Optical Fiber Sensors in the Castable Lining after the Steel Pour Was 591°C. the Spatially Continuous Optical Fiber Sensors Provided Useful Information on Thermal Gradients in the Castable Lining. Real-Time Monitoring of Spatially Distributed Thermal Profiles in the Refractory Lining Can Improve Superheat Control, Reduce Energy Losses, Detect Refractory Wear, and Improve the Quality of the Cast

Highly Cascaded First-Order Sapphire Optical Fiber Bragg Gratings Fabricated by a Femtosecond Laser

This Letter Reports an Innovative Technique for Fabricating Large-Scale, Highly Cascaded First-Order Sapphire Optical Fiber Bragg Gratings (FBGs) using a Femtosecond Laser-Assisted Point-By-Point Inscription Method. for the First Time, to the Best of Our Knowledge, This Study Successfully Demonstrates a Distributed Array of 10 FBGs within Highly Multimode Sapphire Crystal Fiber, Made Possible by Employing a High-Power Laser Technique to Generate Larger Reflectors with a Gaussian Intensity Profile. These First-Order FBGs Offer Advantages Such as Enhanced Reflectivity, Shorter Fabrication Time, and Simplified Spectral Characteristics, Making Them Easier to Interpret Compared with High-Order FBGs. the FBGs\u27 Resilience and Effectiveness Are Analyzed by Subjecting Them to Temperature Tests, Proving their Capacity for Accurate Temperature Monitoring Up to 1500°C—a Testament to their Suitability for Harsh Environments. This Novel Approach Broadens the Scope for Sensing and Communication Applications in Sapphire Fibers, Particularly under Challenging Conditions. the Novelty of Our Work Lies in Successfully overcoming the Limitations of Previous Designs by Integrating a Cascade of 10 FBGs in Sapphire Fibers, Thereby Enhancing Multiplexing Capabilities, Minimizing overlapping of FBG Peaks, and Ensuring Reliable Temperature Monitoring in Industries and Applications with Thermal Gradients

Structural Analysis Of Molten Materials By A Remote Fiber Optic Raman Sensor

This study presents a novel in situ high-temperature fiber optic Raman probe that enables the study of the physical properties and structure of molten samples at temperatures up to 1400°C. To demonstrate the functionality of the hightemperature fiber optic Raman probe, different composition mold fluxes were evaluated in this report. The Raman spectra at flux molten temperature were successfully collected and analyzed. A deconvolution algorithm was employed to identify peaks in the spectra associated with the molecular structure of the components in each sample. The experimental results demonstrate that the composition-dependent Raman signal shift can be detected at high temperatures, indicating that molten materials analysis using a high-temperature Raman system shows significant promise. This flexible and reliable high-temperature Raman measurement method has great potential for various applications, such as materials development, composition and structure monitoring during high-temperature processing, chemical identification, and process monitoring in industrial production

The Study Of The Behavior Of CaO-SiO2-Al2O3-Na2O-Based Mold Flux At 1,400 ºC By A Fiber -Optic Raman Sensor

Mold flux is an essential component for quality casting of steel as it controls heat transfer, lubricates the mold, and insulates the steel both thermally and chemically. However, because mold flux and steel interact during long sequences, the mold flux composition must be closely monitored to prevent undesirable defects. This paper proposes a high- temperature fiber-optic sensor to detect the Raman spectra of mold flux at 1400°C in real time that is suitable for online analysis. The experimental results demonstrate the viability of employing Raman spectroscopy to monitor the chemical composition of a mold flux under high-temperature conditions during continuous casting

Fiber-Optic Raman Probe For On-line EAF Slag Analysis

In Electric Arc Furnace (EAF) steelmaking, the push for improved efficiency requires accurate analysis of the chemical composition of its slag system to control slag foaming, provide refractory protection, and maintain high furnace iron yield. Therefore, the ability to obtain real-time slag chemistry data would provide a useful tool to improve the control and efficiency of the process. The work reported here aims to assess the structure and chemistry of EAF slags at high temperatures using a portable fiber-optic Raman probe. The ability to relate Raman spectra peaks to chemistry and structure is demonstrated in experimental result with EAF slags at 1550°C