Slajd 1

1
Technical University of CzestochowaThe Faculty
of Process Material Engineering and Applied
PhysicsThe Department of Industrial Furnaces and
Environmental Protection
Jaroslaw Boryca, Marian Kieloch, Lukasz Piechowicz
Modeling of the influence of technology and
productivity on thickness of scale layer in the
heating steel charge process
Abstract Heating of steel before the plastic
working is a very important process which
influences on quality of rental product and also
on complete money of the industrial processing.
Modern heat furnace present the complicated
thermal devices work of which is grounded about
the made phenomena of exchange of heat and mass.
The detailed cognition of these phenomena
requires wide theoretical developments,
laboratory measuring and also long-term
industrial researches.
Mathematical model In the work 2 computer
simulation was on basis of worked out numeric
model heating charge was conducted. It was put
was, that the heating process two-stage runs with
linear growth of temperature in period heating
up. It was established was, that for put course
of temperature of surface metal, initial
thickness of scale layer of scale d0 5 mm and
the speed of heating M 800 K/h, the essential
differences of temperature step out among surface
of metal and the surface of scale. The largest
differences of temperature stepped out on
beginning and on end of period heating up (?tmax
70 and 50ºC) (Fig. 1). The study of mathematical
model of heating of charge had on aim the
execution on conditions of flow of warmth the
numeric analysis of influence of scale layer the
charge inside as well as the delimitation the of
heating curves being with basis to execution of
laboratory investigations. The calculation of
heating charge was conducted for technology the
settled on basis of measurements of temperatures
in zones of real pusher furnace. In real pusher
furnace be heated of "cold steel charge. For
aims calculations, real pusher furnace import to
model, in which charge moves along furnace with
monotonous movement, and passing on to flow
warmth be holds on whole length of furnace. The
schedules of temperatures on fig. 2 were
introduced in zones of furnace.
Method of investigation The investigation was
conducted on samples in shape of roller the
executed from steel coal St3. The diameter of
samples carried out 30 mm, however height 50 mm.
Samples on one with their bases possessed
threaded enabling opening fastening to them hook.
Before beginning experiment sample be weighed as
well as measured and placed in furnace across
free hang up to weight then. In time of duration
of experiment the measurements depended on
registration of increase of mass sample mainly as
well as the control of parameters of process
burning. The measurement of mass be held with
frequency 0,00333 Hz. It water after end of
experiment sample was cooled was and the
remainder of scale in mechanical way was removed
with her, and weighing was made second then. The
measurement of thickness of pieces scale near use
the micrometer was has carried out
additionally. One the measured thickness of scale
( the measurement on cold) compared from
counted according to example (the measurement
hot)
They of thickness of layer scale appointed two
methods values are to me approximate. Average
relative difference among them carries out 4,11
. The similar difference steps out among values
of loss of steel.
It technologies were named was the received
schedules of temperatures conventionally and it
was marked as T(a) and T(b). It the calculation
of heating charge was realized was near use
procedure the worked out in environment of
application Mathcad 2001 Professional. Worked
out algorithm permits to mark the heating curve
for at will the set schedule of temperature and
any capacity. It the precise description of
procedure of calculations was contained was in
work 1.
Mathematical analysis It the value of thickness
of scale layer to analysis of results of
measurements was taken was appointed with method
of "measurement on cold (d1). They loss of steel
on decisive influence, except efficiency, the
received heating technology has. It for
technology T(b) average was got was about
22 smaller thickness of scale layer in
comparison to technology T(a). It was affirmed
was, it that was can describe with dependences on
thickness of scale layer the influence of
efficiency
Fig. 2. The schedules of temperatures of furnace
zones for definite heating technology
Fig. 1. Results of calculations in individual
zones the temperatures of charge

• Numerical analysis of influence of scale layer on
  heating conditions the steel charge
• It was calculation accepted, that heating charge
  draws ahead with technology T(a) peaceably
  (Fig.2). The process of heating be holds with
  project efficiency carrying out 120 t / h. It the
  simulation of heating charge was conducted was
  for two cases
• without regard of process of metal oxygenation,
• from regard the influence of metal oxygenation on
  process of flow warmth, near foundation, that the
  initial thickness of scale carries out 0.5 mm.
• It the results of calculations of for above
  mentioned foundations were introduced was on fig.
  3.

Statistical errors have been calculated. It has
been found that the average value of the mean
error of approximation is 1,70 and 1,87 .
Whereas, the average value of the correlation
coefficient is 1,70 i 1,87 . The influence of
efficiency on thickness of scale layer show on
Fig. 5.
Fig. 5. The influence of efficiency on thickness
of scale layer for studied heating technologies
From calculation it results, that the of scale
layer of oxygenation of metal (steel) coming into
being in result the negative influence can exert
on field of temperature inside the charge. It the
different final values of temperatures were got
was on surface and in axis of metal. For they
calculations of without regard they lay
oxygenation, the final temperature of metal
carried out t0 1238ºC, however temperature in
axis tos1208ºC. For calculations from regard
of oxygenation lay, temperatures these carried
out 1226ºC and 1190ºC, near final thickness of
layer of scale d 1.21 mm. The results of
calculations can show, that during working out of
heating technology of one should to take into
account influence of scale layer on final field
of temperature in section of charge.

• Conclusions
• The oxygenation of charge in heating process
  before plastic working, except considerable
  losses of steel, the lowering on result the
  intensity of process of made difficult
  penetration of to surface of metal warmth causes.
  This phenomenon this be caused, that scale in
  comparison from steel has the considerably
  smaller value of conductivity coefficient. The
  lack of regard on stage the thickness of scale
  layer of projecting the heating technology, it
  can cause, that the settled temperatures in zones
  of furnace can turn out for low to receipt of
  technological field of temperature the charge
  inside.
• It problem this can turn out particularly
  essential for
• heating from initial of scale layer,
• heating charge about large section,
• furnaces achieving the high coefficients of loss
  of steel on result of incorrect exploitation.
• It on basis of laboratory measurements was
  established was, that the thickness of scale
  layer creator (the loss of steel) it is closely
  dependent from curve heating, which it is the
  result the received technology (received schedule
  of temperature in zones of furnace) as well as
  the capacity. The smallest thickness of scale
  layer was got for heating with the capacity which
  is close capacity project. In case heating it
  with lower capacity from project, was one should
  alter the heating technology (lower the value of
  zone temperatures).

Measuring stand The investigation the influence
of heating curve (the technology and the
efficiency) on thickness of scale layer (they
stood the loss) it required of specialist
measuring stand (fig. 4).
Fig. 3. The schedules of temperatures for
considered cases
Fig. 4. Scheme of investigative stand 1-electric
tubular furnace, 1a-heating chamber, 1b-resistory
heating elements, 1c-thermal isolation,
2-three-phase feeding wardrobe, 2a-set the
arrangement of adjustment the admission of
furnace (the adjustment of power in manual
cog-wheel), 2b-the desk top with additional
functions, 2c-the keyboard and display of
programmable regulator, 2d-the keyboard and the
display of automatic limiter protecting, 2e-the
regulator the programmable SHIMADEN - FP93, 3-the
radial ventilator, 4-valve
of air, 5-the rotameter to measurement of
intensity of flow air combustion, 6-valve of gas,
7-gas rotameter, 8-gas burner, 9-feeding sparkle
exploder, 10-transformer - sparkle exploder,
11-the thermocouple controlling flame, 12-the
converter the YUKO-KO-485d with transport through
harbor RS 232, 13-the card PersonalDaq/54 with
transport through harbor USB, 14-the notebook
computer with software, 15-regulating
thermocouple, 16-the thermocouple to measurement
of temperature on surface of studied sample,
17-the mobile analyzer of flue gases TESTO 350,
18-supervisory co-operating from protecting
limiter thermocouple, 19-pull-off of flue gases,
20-the isolated shelf on weight, 21-steel sample,
22-the electronic weight precise WPS 360/C,
23-the electronic meter of energy the electric
LUMEL - LS31 with digital transport.

• References
• Piechowicz L. Zuzycie ciepla a straty stali w
  procesie nagrzewania wsadu, Praca doktorska,
  Politechnika Czestochowska, Czestochowa 2008.
• Piechowicz L., Kieloch M., Boryca J. Model
  numeryczny nagrzewania wsadu z uwzglednieniem
  powstawania zgorzeliny, Nowe technologie i
  osiagniecia w metalurgii i inzynierii
  materialowej, Czestochowa 2006, s. 430-433.