Quantified results of rapid cooled C-pattern in agitated quenchant.
Duehring, Steven ; Spanielka, Jan ; Taraba, Bohumil 等
Abstract: The article is focused on the issue of heat treatment.
The cooling curves were obtained for Isorapid 277HM with an experimental
way of temperature measuring and their statistical processing. Material
data of the material pattern 50CrMo4 were obtained from the Material
Data Sheet (MDS) of Deutsche Edelstahlwerke (**'2011). The cooling
oil lsorapid 277HM was agitated with energy input 1.65 [J.s.sub.-1]
[.kg.sub.-1] and had a constant temperature of 50[degrees]C. In the
follow of this article were showed the experimentally obtained results:
geometry distortion, dimensional and metallurgical evaluation.
Key words: heat treatment, Isorapid 277HM, agitated oil, C-pattern,
steel 50CrMo4, distortion
1. INTRODUCTION
Today a typical problem is the exact and reliable prediction of
distortion and failures in the heat treatment processes. Beside the
possibilities of experimental, analytical and semi-empirical methods
will used the numerical procedures increasingly. The experimental
methods with prototypes are very expensive and need a lot of time. Often
these methods can not used in practise, reasoned by very complicated
conditions, difficult geometrics and the non-exactly reproducibility.
But basic data's are determined from experiments. FEM simulations
are only convincing with regard to well-known and defined boundary
conditions.
The kind of quenching medium, the selection of quenching medium
temperature, the selection of the medium state (no agitated, agitated),
the material properties at start (e.g. manufacturing process, follow up
treatment) and the changes of material behaviour are determining
factors. Basically for application in a numerical simulation is the
quantitative definition of the pattern surface and the material
properties. In summary the experiment will give basic information for
detecting of room for improvement of simulation.
2. EXPERIMENTAL SETUP AND PROCEDURE
The experimental setup consists of an electrical resistance furnace
of LM 212.10 type, a "C"-pattern of 50CrMo4; oil Isorapid
277HM--agitated, with mass of 28kg and pneumatically manipulator for
pattern moving. The outer diameter (OD) of the pattern was 110 mm, the
inner diameter (ID) was 68 mm and its high 20 mm see Fig. 1.
[FIGURE 1 OMITTED]
The material of the pattern is 50CrMo4 (1.7228) and its properties
see (***, 2011, Szmolka, Hazlinger, 2009). At the beginning of the
experiment the pattern was heated up from room temperature to the
initial temperature 850[degrees]C [+ or -] 5[degrees]C. Reference of the
temperature of the pattern was the furnace temperature control. The oil
temperature was 50[degrees]C checked by thermometer immersed in the
cooling medium and will accept as constant in the oil tank. The
quenching oil was agitated with energy input 1.65 [J.s.sup.-1]
[.kg.sup.-1] (Hajdu&Taraba, 2010). If the pattern has reached the
target temperature in the furnace, the pneumatic manipulator moves the
pattern as quick as possible into the cooling medium. The pattern was
kept in the oil more then 20 min to be sure, that the pattern has
reached the oil temperature also in the core. Afterwards the pattern was
analyzed with regard to the geometrical dimension, hardness distribution
and microstructure.
3. OBTAINED RESULTS OF THE EXPERIMENT
After removing the pattern, the figure 2 shows the pattern in
original with definition of measurement points. On the surface is
observed visually black spots which are not hard bonded to the rest of
material and comes from free sooty particles. The pattern was stored for
7 days. For the dimensional evaluation the pattern is measured with a
CMM at 20.01[degrees]C with an accuracy of 2 [micro]m, results see in
Table 1.
[FIGURE 2 OMITTED]
For visualization of distortion it was taken a contour
determination of ID and OD in different depths of 2.5 mm, 10.0 mm and
17.5 mm with a 3D--surface scanning procedure with CMM, see exemplary
figure 3, 4 [right arrow] bold black line is the original edge of body
after, middle circle is before.
[FIGURE 3 OMITTED]
[FIGURE 4 OMITTED]
[FIGURE 5 OMITTED]
The evaluation of hardness regarding to cut systematic obtains the
following results in table 2 and metallurgical investigation see in
figure 6. For metallurgical evaluation see figure 6 we can summarize a
finer grain size in edge area. Micro- and makro cracks were not
detected. The residual austenite content in border structure is lower
than < 20 %. Ferrite content is lower than 3 % and ferrite-pearlite,
fine grained with even distribution were not detected. Martensite and
Bainite is detected in the core, a result of lower cooling speed in
core.
[FIGURE 6 OMITTED]
4. CONCLUSION
The elastic deformation part is following the Hook's Law, the
thermal deformation part will summarized of the thermal expansions of
the structural constituents. For the calculation of transformation into
martensite during the rapid cooling we use the CCT or the
Koistinen-Marburger approach (***, 2011). The outcome of this is the
part of plastic dilatation. In order to calculate the plastic
transformation part of expansion we need the flow criteria, the flow law
and a formula which consider the increments of deformation linked with
the current strains with regard to current temperature. Furthermore we
have to respect creeping effects, evaluation of quenching power, effect
of process variables (bath temperature, agitation and others) on cooling
behaviour, effect of cooling characteristics on residual stress and
distortion. The real result of the experiment will used for comparison
and improvement within simulation approaches.
5. ACKNOWLEDGEMENTS
Thank to MTF STU Bratislava for facilitating implementation of
research. Article was supported by VEGA 1/1041/11.
6. REFERENCES
*** (2011) http://www.dew-stahl.com/fileadmin/files/dewstahl.com/documents/Publikationen/Werkstoffdatenblaetter/ Baustahl/1.7228_de.pdf,
Accessed 2011-06-05
*** (201 l) http://www.petrofer, com.ua/content/hardening com
pound/21.htm, Accessed 2011-06-05
Hajdu S., Taraba B. (2010). The numerical approach to the
calculation of combined heat transfer coefficient for cooling probe
immersed in agitated quenching oil. In: Annals of DAAAM and Proceedings
of DAAAM Symposium.--ISSN 1726-9679.--Vol. 21, No 1. Vienna, 2010.--ISBN
978-3901509-73-5, s. 1141-1142
Szmolka T., Hazlinger M. (2009). Influence of tempering temperature
on fracture behaviour of 50CrMo4 steel. In: 8th Youth Symposium on
Experimental Solid Mechanics. Gyrr, Hungary. Scientific Society of
Mechanical Engineers, 2009. --ISBN 978-963-9058-26-2.--S. 84-85
*** (201 l) http://www.math.uni
bremen.de/zetem/cms/media.php/262/report0702.pdf
Tab. 1. Dimensional values from CMM regarding to defined
measurement points
No description value No description value
[mm] 1-1 [mm]
1 Clear width 10.607 11 Probe 20.216
depth
2 Clear width 10.619 12 Pattern 20.231
depth
3 Clear width 10.669 13 Pattern 20.091
depth
4 Clear width 10.671 14 Pattern 19.949
depth
5 Clear width 10.428 15 ID depth 68.258
2.5
6 Clear width 10.307 16 1D depth 68.239
10.0
7 Clear width 10.303 17 ID depth 68.177
17.5
8 Clear width 10.437 18 OD depth 110.210
2.5
9 Pattern 19.954 19 OD depth 110.194
depth 10.0
10 Pattern
depth 20.075 20 OD depth 110.184
17.5
Tab. 2. Hardness values after heat treatment
cut 1 cut 2 cut 3 cut 4 cut 5
core [HV1] 730 779 763 745 751
edge [HV1] 1745 748 763 748 763
