FIELD OF THE INVENTION
The present invention relates to an improved process for measuring vertical heat
transfer through different layers of mould powder/slag in a continuous casting
mould. The present invention further relates to a temperature probe to measure
heat transfer in the vertical direction through different mould powder/slag layer
in a continuous casting mould for casting steel slabs.
BACKGROUND OF THE INVENTION
Mould powder is an essential requirement for continuous casting of steel, in
particular steel of higher cross sections i.e. slabs, blooms and thin slabs. Mould
powder plays several roles during a continuous casting process for example, a)
provide lubrication between the mould and the solidifying strand gap, and b)
control of heat transfer from the top of the liquid steel to prevent freezing of the
meniscus. The present inventors recognized that the vertical heat transfer (VHT)
from liquid steel to the top mould powder layer has a significant impact on
surface quality of the cast product. As the mould powders is added from the top
of the mould over the liquid steel, so heat transfer in the vertical direction plays
a very important role as this influences the following properties/parameters
during continuous casting, a) melting rate of mould powder and its infiltration, b)
liquid slag pool formation, c) sintering of mould powder, d) vertical insulation on
the mould top. Therefore, it is crucial to determine the vertical heat transfer
profile through the mould powder/slag layers on the top of the mould.
Accordingly, it has been observed that the mould powder added on top of the
mould forms at least three distinct layers for example, 1) liquid slag layer on
liquid steel, 2) sintered layer above the liquid slag, 3) raw mould powder above
sintered layer as can be seen in Figure 2.

The non-patent literature entitled, Modelling molten flux layer thickness profiles
in compact strip process moulds for continuous thin slab casting", by Macias A.
E. Castillejos E. A. H.; Acosta G. F. A.; Herrera G. M.; Neumann, F. Cinvestav,
Mex. Ironmaking and Steelmaking (2002), 29(5), 347-358, Publisher: Maney
Publishing CODEN; teaches that the important functions promoted by powder
flux added over the liquid steel surface in continuous casting molds are strongly
affected by the thickness of the liquid layer that forms as a result of heat
absorbed. The publication discusses the results of a three-dimensional steady-
state model, developed to represent the coupled fluid flow and heat transfer
phenomena that determines thickness profiles of the liquid flux layer. Since the
laminar flow of the liquid slag layer depends on the shear imposed on it by the
turbulent motion of the liquid steel beneath it, and since the additional motion is
strongly influenced by the flow characteristics of the steel stream poured into the
mold through the submerged entry nozzle (SEN), separate turbulent flow models
for the liquid steel in the SEN and the mold were also developed. The
consistency among the models and their accuracy was judged by comparing
thickness and temperature flux profiles measured in plant against predicted
ones; the comparison showed good agreement. The effects of casting speed,
mold width, and flux viscosity and heat of melting on the liquid layer thickness
were investigated. The last variable was found to exert the most marked
influence. Different from conventional casting molds, where the liquid layer
thickness increases with increasing casting speed, in compact strip process molds
the thickness remains almost constant, with the increase in casting speed. This
difference is well accounted for by the model, which suggests that this behavior
stems from the different slag flow patterns generated in straight, wide molds and
in thin molds having a central upper funnel shaped section.

The non-patent literature entitled, "Theoretical and experimental study of vertical
continuous casting of copper", by Uoti, Markku; Immonen Mikko; Harkki Kalle.
Laboratory of Metallurgy, Helsinki University of Technology, Finland, dated
Nov. 13-15,2000 (2000), discloses an experimental study on heat transfer and
solidification during vertical continuous casting of copper. Plant scale
temperature measurements at the foundry and mathematical modeling were
combined. A finite-element model based software FIDAP was used to calculate
heat transfer and solidification phenomena, liquid pool depth, mold temperature
and cast slab temperature were determined. After tuning the model the main
mathematical model was used to investigate the effects of parameters such as
heat transfer coeff. and casting velocity on the temperature distribution in the
cast slab, especially on the shape and location of the solidification front.
US2009296773 teaches a double temperature sensor with a receiving element
for measuring a near-surface temperature of the ambient air and the skin
surface. The double temperature sensor with a receiving element includes an
insulating block, two temperature sensors and a receiving element. At least the
receiving element (8) and/or the insulating block are designed in terms of the
material structure such that the horizontal heat conduction is low compared to
the vertical heat conduction.
Very few works has been carried out in the prior art to measure the heat transfer
in the vertical direction of the mould slag in the mould. As the vertical heat
transfer is very important for powder melting and controls also the infiltration
between the mould and strand, it has been long-felt need to propose means for
measuring vertical heat transfer phenomena in the mould.

OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose a temperature probe to
measure heat transfer in the vertical direction through different mould
powder/slag layer in a continuous casting mould for casting steel slabs.
Another object of the invention is to propose an improved process for measuring
vertical heat transfer through different layers of mould powder/slag in a
continuous casting mould.
SUMMARY OF THE INVENTION
According to the invention, there is provided a temperature probe to measure
heat transfer in the vertical direction through different mould powder/slag layer
in a continuous casting mould for casting steel slabs, comprising a plurality of
thermocouples, disposed in a probe body, and being connected to a data
acquisition system which can continuously monitor the temperature. The probe is
dipped onto the top of the mould through different mould powder layers and the
temperature is recorded. The thermocouples are adequately protected from
melting.
After collecting the temperature data, a post processing of the captured data is
carried out in a processor to determine different thermal gradient across and in
between the different layers of slag.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 Schematically shows a probe to measure vertical heat transfer
according to the invention.
Figure 2 Shows different operational positions of the probe during insertion
in mould/slag layers.
Figure 3 Graphically exhibits measurement data through different slag
layers.
DETAILED DESCRIPTION OF THE INVENTION
According to the present invention, at least four (1,1,1,1) thermocouples are
inserted into the layers of mold/slag through a cylindrical pipe (2) configured
with a series of holes (a,b,c,d) on one side of the pipe (2) near its bottom as can
be seen in Figure 1. The tip of each thermocouple (1) is exposed outside through
these holes (a,b,c,d). Figure 2 represents a vertical heat transfer sample proble
(P) and the steps of gradually dipping the probe from the top of the mould
through different layers (5,6,7,8). The four thermocouples (1) generate data
concurrently and are recorded through a data logger (3). Analysis of the data
(Figure 3), clearly distinguishes all the top powder/slag layers (5,7) and the
corresponding temperature gradients. Measurement of vertical heat transfer
through different layers (5,6,7,8) of mould provides substantial advantages in
terms of determining online mould powder behaviour. A reliable prediction on
the following online casting parameters enables (i) identification of melting point
of the mould powder from the vertical heat transfer measurement to eliminate

prior art step of Differential Scanning Calirometry (DSC), (ii) accurately analyzing
based on the determined measured data interaction between sintered powder
(6) and liquid slag (7) in their interface, (iii)fast-determining of heat loss data
from the top of the caster, (iv) determining data on actual liquid slag pool depth
enabling measurement of lubrication loss during casting.

WE CLAIM :
1. A device to measure heat transfer in vertical direction through a plurality
layers of mould powder and slag in continuous casting moulds during slab-
casting, comprising :
- a temperature probe configured in the shape of a cylinder and configured
with a plurality of holes at different heights along the probe body;
- a plurality of thermocouples disposed in the probe body such that first
ends of the thermocouples respectively exposed to said mould
powder/slag layers via the plurality of holes, the second ends of the
thermocouples extend through the top-open portion of the cylindrical
probe body;
- a data conversion means operably connected to the second end of the
thermocouples to convert captured analog data to digital data; and
- a processor having a memory device with pre-stored data and operably
connected to the data conversion means;
wherein the probe upon gradually dipping into the mould is enabled to
generate respective temperature data of said plurality of layers through
said plurality of thermocouples which on processing by the processor
provide on-line casting parameters including deviation from pre-stored
data so as to introduce corrective measures.

2. A measuring device to measure heat transfer in vertical direction through
a plurality layers of mould powder and slag in continuous casting moulds
during slab-casting as substantially described and illustrated herein with
reference to the accompanying drawings.

ABSTRACT
The invention relates to a device to measure heat transfer in vertical direction
through a plurality layers of mould powder and slag in continuous casting moulds
during slab-casting, comprising : a temperature probe configured in the shape of
a cylinder and configured with a plurality of holes at different heights along the
probe body; a plurality of thermocouples disposed in the probe body such that
first ends of the thermocouples respectively exposed to said mould powder/slag
layers via the plurality of holes, the second ends of the thermocouples extend
through the top-open portion of the cylindrical probe body; a data conversion
means operably connected to the second end of the thermocouples to convert
captured analog data to digital data; and a processor having a memory device
with pre-stored data and operably connected to the data conversion means;
wherein the probe upon gradually dipping into the mould is enabled to generate
respective temperature data of said plurality of layers through said plurality of
thermocouples which on processing by the processor provide on-line casting
parameters including deviation from pre-stored data so as to introduce corrective
measures.