ft Mes ig Image Analysis of Carbides in High Speed Steel Rolls and their Relationship
| with the Mechanical Properties
ck Paar
— Laurence de Colnet, Eric Pirard, Mica Laboratory; Jacqueline Lecomte, Jérome Tchoufang
ws * md bg ~~ Tchuindjang, M&S Laboratory, Université de Liege, Belgium
i
TT ig
Abstract
Image analysis is used to describe quantitatively various different natures of carbides in high speed
SED amined steel rolls. After an etching judiciously selected, the identification and the extraction of the carbide
eprodzertarkei types are based on spectral differences. For every carbide type, three parameters are measured : the
size, the spatial distribution and the volume fraction. The size of martensite grains is also measured.
Introduction
One goal of the COST 517 project entitled Effects of inclusions and carbides on the mechanical
werk stellt einen properties of alloyed steels is to establish quantitatively and statistically relations between the
Sindy ~ Microstructural and the mechanical properties of high speed steels. Mechanical tests will provide
10C16 themprif quantitative parameters like the tensile strength, the wear resistance, the hardness, the toughness,
Jationen zwischen the resilience. The microstructure is characterised by quantitative parameters measured by image
1s Newonale Netz analysis.
ım Stahl 100Cr6
The materials studied are rolls formed by a high speed steel shell (60 mm thick) and a nodular
; Beurteilung von graphite iron core manufactured by a vertical spin-casting process. The shell, directly in contact
roßer Aufwand zu with the rolled products, is submitted to high solicitations. So, its microstructure is the only one to
tog zu stelle be characterised. Preliminary observations of the shell under an optical microscope show
Härtemessung an microstructural differences from the surface to the shell-core limit. To characterise these
x könnten. auch differences, samples are cut off radially all along the thickness of the shell. The core-shell limit, that
derum zu großen is visible on the samples, allows to orientate them.
——pp 7 Core
Shell
Fig. 1 : Sampling for microscopic observations
FH Aalen (1998)
amaramefemn und Image acquisition
Acquisition system
am Beispiel von The acquisition system combines an optical microscope, a black and white CCD-camera and a set
an Metallographit of interference filters. The camera has a large spectral sensitivity spectrum (350 nm to 1000 nm)
aa and a high resolution (1280 by 1024 pixels). An interference filter in front of the camera selects
ae (100) only the wavelengths belong to a very narrow interval (107 m width at half maximum
Cs OD transmission peak). The wavelength of the interference filter is chosen to maximise the contrast
5 095 between phases when taking pictures.
rag 190)
ı and distributed
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