On the Sensitivity of a Tool–Workpiece Thermocouple to Chemical Composition and Microstructure. Issue 4 (19th January 2023)

• Record Type: Journal Article
• Authors: Tröber, Philipp; Hackl, Alfred; Leitner, Harald; Welm, Markus; Demmel, Peter; Golle, Matthias; Volk, Wolfram
• Other Names: Asnafi Nader guestEditor.
• Is Part Of: Steel research international. Volume 94:Issue 4(2023)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2023-01-19
• Subjects: calibrations -- chemical compositions -- Seebeck coefficient -- temperature measurements -- thermoelectricity -- tool–workpiece thermocouple; Steel -- Periodicals; Steel -- Metallurgy -- Periodicals; 669.142
• DOI: 10.1002/srin.202200456
• Languages: English
• ISSNs: 1611-3683

Abstract

Abstract : Meeting the increasing demands on part quality and profitability of manufacturing processes despite difficult‐to‐machine materials is only possible with a deep understanding of the process. Herein, knowledge about the process temperature is of critical importance since it affects the material properties, such as hardness or forming behavior, as well as the chemical and physical interactions between the tool, workpiece, and lubricant. A proven thermoelectric method of temperature measurement in machining, forming, and blanking is a tool–workpiece thermocouple. Herein, instantaneous measurement of the temperature development is allowed in this setup during the manufacturing process in situ at the contact area of the tool and workpiece. The accuracy of this method is dependent on the calibration of the thermocouple, for which the Seebeck coefficients of the tool and workpiece material have to be determined. Usually, material samples from different batches are used for this purpose, although the resulting measurement errors due to slight changes in material properties are hardly known. The effects of small changes in the chemical composition and the transformation of the crystal lattice due to hardening on the Seebeck coefficient are investigated for the first time to allow precise quantification of the measurement error resulting from the calibration process. Abstract : A tool–workpiece‐thermocouple allows measuring process temperatures in sheet metal processing. To achieve high accuracy, a precise knowledge of the material‐specific Seebeck coefficients is a prerequisite. Herein, the effects of small changes in chemical compositions and heat treatment on this coefficient and the resulting temperature deviation are shown using blanking as an example.