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Stadthagen, Germany

Falk H.,Scientific Consultancy Prof. Dr. Heinz Falk | Falk M.,Falk Steuerungssysteme GmbH | Wuttke T.,ThyssenKrupp
Spectrochimica Acta - Part B Atomic Spectroscopy

The sampling of the surface-near gas composition using a mass spectrometer (MS-Probe) is a valuable tool within a hot dip process simulator. Since reference samples with well characterized surface coverage are usually not available, steel samples can deliver quantifiable amounts of the process relevant species H2O, CO and H2 using the decarburization reaction with water vapor. Such "artificial calibration samples" (ACS) can be used for the calibration of the MS-Probe measurements. The carbon release rate, which is governed by the diffusion law, was determined by GDOES, since the diffusion coefficients of carbon in steel samples are usually not known. The measured carbon concentration profiles in the ACS after the thermal treatment confirmed the validity of the diffusion model described in this paper. The carbon bulk concentration > 100 ppm is sufficient for the use of a steel material as ACS. The experimental results reported in this paper reveal, that with the MS-Probe the LOQ of less than one monolayer of iron oxide can be achieved. © 2014 Elsevier B.V. All rights reserved. Source

Falk H.,Falk Steuerungssysteme GmbH | Falk H.,ThyssenKrupp | Falk M.,Falk Steuerungssysteme GmbH | Falk M.,ThyssenKrupp
Yejin Fenxi/Metallurgical Analysis

The reactions taking place in the annealing atmosphere of a furnace simulator can be monitored with the help of a mass spectrometer probe positioned near to the steel surface [1-3]. The concentrations of water vapor and hydrogen near to the steel surface during the thermal cycle within the furnace are of particular interest, since they are changing as a result of the interaction with the alloying elements oxides on the steel sheet as well as those near to the surface. The concentrations of H 2O, H 2, CO, CO 2, NH 3 and N have been measured via the mass spectrometer probe for studying the oxidation, reduction, decarburization and nitriding processes. After the thermal treatment the concentration distributions of the relevant elements determined by GDOES within the surface near layer could be correlated to the measurements results of the gaseous species concentrations. These data allow controlling the surface conditions during the continuous annealing part of a hot dip galvanizing line by in-situ measurements and also a description of the metallurgical behavior of steel grades differing in their alloying concepts. Source

Falk H.,Falk Steuerungssysteme GmbH | Falk M.,Falk Steuerungssysteme GmbH
Steel Research International

This study presents a new probe to analyse the gas composition near a metal surface. The probe uses a mass spectrometric detector and is incorporated in an experimental reactor for the thermal treatment and surface formation of steel sheet samples. Steel samples were exposed to various oxidizing and reducing gas flows at pressures between ambient and 3 bar. The reaction product H2O was measured with the MS-probe while reducing oxidized steel surfaces with H2 as well as the consumption of H2 as a function of the sample temperature. Similarly, the reaction productsCOand H2 were monitored during the oxidation of the bulk carbon with H2O. The sample temperature was ramped linearly from ambient to 900 8C. From these measurements it was possible to evaluate the onset temperatures and the activation energies for the respective reactions. The in-situ monitoring of the gas phase near the steel surface within the experimental reactor allows controlling the formation of a layer of iron as a result of the iron oxide reduction. Similarly, the decarburization of steel can be followed up by measuring the time course of the CO concentration. It is expected that the MS-probe will become an efficient tool for the understanding and optimization of the annealing and formation processes during strip annealing before hot dipping Copyright © 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

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