U.S. patent application number 13/388172 was filed with the patent office on 2012-06-28 for method and device for producing a microalloyed steel, in particular a pipe steel.
Invention is credited to Joachim Ohlert, Juergen Seidel.
Application Number | 20120160377 13/388172 |
Document ID | / |
Family ID | 42752124 |
Filed Date | 2012-06-28 |
United States Patent
Application |
20120160377 |
Kind Code |
A1 |
Seidel; Juergen ; et
al. |
June 28, 2012 |
METHOD AND DEVICE FOR PRODUCING A MICROALLOYED STEEL, IN PARTICULAR
A PIPE STEEL
Abstract
The invention relates to a method of making microalloyed steel,
in particular a pipe steel, wherein a cast slab (1) passes through
an installation (2) having a casting machine (3), a first furnace
(4), at least one roughing roll stand (5), a second furnace (6), at
least one finishing roll stand (7), and a cooling line (8) in this
order in the travel direction (F) of the slab (1). The method
comprises: a) definition of a desired temperature profile for the
slab (1) over its travel through the installation (2); positioning
in the process line (L) of the installation (2) at least one
temperature-influencing element (9, 10) for setting the temperature
of the slab (1) according to the defined temperature profile, the
temperature-influencing element (9, 10) being introduced between
the first furnace (4) and the roughing roll stand (5), and/or
between the second furnace (6) and the finishing roll stand (7);
production of the slab (1) in the installation (2) configured in
this manner, the temperature-influencing element (9, 10) being
operated in such a way that the defined temperature profile is at
least substantially maintained. The invention further relates to an
installation for making microalloyed steel.
Inventors: |
Seidel; Juergen; (Kreuztal,
DE) ; Ohlert; Joachim; (Koeln, DE) |
Family ID: |
42752124 |
Appl. No.: |
13/388172 |
Filed: |
August 5, 2010 |
PCT Filed: |
August 5, 2010 |
PCT NO: |
PCT/EP2010/004814 |
371 Date: |
March 1, 2012 |
Current U.S.
Class: |
148/654 ;
72/201 |
Current CPC
Class: |
B21B 37/74 20130101;
C21D 8/0226 20130101; B21B 1/463 20130101; B22D 11/1206 20130101;
B21B 1/46 20130101; C21D 8/0215 20130101; C21D 8/021 20130101 |
Class at
Publication: |
148/654 ;
72/201 |
International
Class: |
C21D 9/52 20060101
C21D009/52; B21B 43/00 20060101 B21B043/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 6, 2009 |
DE |
10 2009 036 378.5 |
Claims
1-26. (canceled)
27. A method of making microalloyed steel, in particular pipe
steel, wherein a cast slab passes through an installation having a
casting machine, a first furnace, at least one roughing roll stand,
a second furnace, at least one finishing roll stand, and a cooling
line in this order in a travel direction of the slab, the method
comprising: a) definition of a desired temperature profile for the
slab over its travel through the installation; b) positioning in
the process line of the installation at least one
temperature-influencing element for setting the temperature of the
slab according to the defined temperature profile, the
temperature-influencing element being provided between the first
furnace and the roughing roll stand, or between the second furnace
and the finishing roll stand; c) production of the slab or strip in
the installation configured in this manner, the
temperature-influencing element being operated in such a way that
the defined temperature profile is at least substantially
maintained, wherein by use of a temperature-influencing element in
the form of a cooler, an input temperature may be achieved in the
finishing roll stand that is low enough that the recrystallization
and grain growth at that location are largely halted, the
temperature level between the input into the roughing roll stand
and the input into the temperature-influencing element in the form
of a cooler being either aa) decreased, in particular for pipe
steel having a low microalloy element content and small slab
thickness, by a temperature-influencing element in the form of a
cooler in order to reduce the grain size upon entry into the
finishing roll stand, or bb) increased, in particular for pipe
steel having a high microalloy element content and large slab
thickness, by a temperature-influencing element in the form of a
heater to ensure complete recrystallization during roughing, or cc)
merely balanced and otherwise being left unchanged, or by use of a
temperature-influencing element in the form of a heater, an input
temperature is achieved in the finishing roll stand that is high
enough that complete recrystallization takes place at that
location, either Aa) during the first finishing passes due to the
high temperatures and reductions, followed by an accumulation of
deformation in the last finishing passes, or Bb) only during the
last finishing passes due to moderate temperatures and reductions,
after prior accumulation of deformation has taken place.
28. The method defined in claim 27, wherein an additional furnace
is used as the temperature-influencing element.
29. The method defined in claim 28, wherein an induction furnace is
used as the additional furnace.
30. The method defined in claim 28, wherein in the additional
furnace the slab is heated by direct flame action.
31. The method defined in claim 30, wherein the direct flame action
of the slab is provided by a gas jet containing 75% oxygen and a
gaseous or liquid fuel.
32. The method defined in claim 28, wherein a soaking furnace is
used as the additional furnace.
33. The method defined in claim 28, wherein a roller hearth furnace
is used as the additional furnace.
34. The method defined in claim 28, wherein a walking-beam furnace
or a pusher-type furnace that allows transverse transport of the
slab is used as the additional furnace.
35. The method defined in claim 27, wherein an additional cooling
line is used as the temperature-influencing element.
36. The method defined in claim 35, wherein an intensive cooler is
used as the additional cooling line.
36. The method defined in claim 35, wherein a laminar strip cooler
is used as the additional cooling line.
37. The method defined in claim 27, wherein a thermally insulating
element is used as the temperature-influencing element.
38. The method defined in claim 27, wherein the temperature profile
is determined on the basis of a structural model.
39. The method defined in claim 38, wherein the structural model
specifies or monitors the following parameters: the temperature
profile over time or the number of passes, the reduction
distribution over time or the number of passes, the holding or
cycle times, the roller speeds and transport speeds, or the heating
and cooling intensities.
Description
[0001] The invention relates to a method of making microalloyed
steel, in particular pipe steel, where a cast slab passes through
an installation having a casting machine, a first furnace, at least
one shaping roll stand, a second furnace, at least one finishing
roll stand, and a cooling line in this order in the travel
direction of the slab. The invention further relates to an
installation for making microalloyed steel.
[0002] Various options are described in the prior art for
manufacturing a strip according to the generic method. Reference is
made to US 2005/0115649 A1, WO 2009/012963 A1, WO 2007/073841 A1,
WO 2009/027045 A1, EP 0 611 610 B1, and EP 1 860 204 A1, for
example.
[0003] Thermomechanical rolling is an established method.
Microalloyed steels have become increasingly important in recent
times. Pipe steel (according to API Specification 5L) is one of the
most important subgroups within microalloyed steel. The demand for
such steel is constantly increasing.
[0004] Most pipe steel is produced in plate rolling mills. However,
in particular if the final thicknesses and final widths are not too
great, pipe steel may also be produced in hot-roll wide strip
mills, referred to as CSP facilities, and other apparatuses for hot
rolling.
[0005] To make microalloyed steel in general and pipe steel in
particular, special emphasis is placed on the variation of
temperature as a function of time (or a function of the location
within the production installation). This variation, in combination
with the reduction distribution, has a crucial influence on
development of the microstructure, and therefore specific
mechanical and technical properties of the steel. For this reason
high-powered cooling units, for example, are used downstream of the
finishing stage, thus allowing setting of the desired temperature
variation.
[0006] It is disadvantageous that previously known production
apparatuses and methods are not optimally suited for flexibly
responding to the particular starting conditions and requirements
in the manufacture of microalloyed steel, in particular pipe steel,
in order to produce these types of steel with an essentially freely
selectable temperature profile over time or over the production
path. Therefore, it is not optimally possible to control and
influence structural development within the steel. The flexible
manufacture of this steel with regard to its chemical composition
and dimensions is therefore limited.
[0007] The object of the present invention, therefore, is to
provide a method and an associated apparatus that allow the stated
disadvantages to be overcome. Accordingly, it is the aim to enable
improved control of the variation of temperature according to a
desired profile over time or over the production path in order to
allow better monitoring and control of the structural development.
Thus, a further goal is to enable more flexible production of
microalloyed steel, in particular pipe steel.
[0008] With regard to the method, this object is achieved by the
invention as characterized by the following sequential steps:
[0009] a) definition of a desired temperature profile for the slab
over its travel through the installation;
[0010] b) positioning in the process line of the installation at
least one temperature-influencing element for setting the
temperature of the slab according to the defined temperature
profile, the temperature-influencing element being introduced
between the first furnace and the roughing roll stand, and/or
between the second furnace and the finishing roll stand;
[0011] c) production of the slab or strip in the installation
configured in this manner, the temperature-influencing element
being operated in such a way that the defined temperature profile
is at least substantially maintained.
[0012] According to one embodiment of the invention, an additional
furnace is used as the temperature-influencing element. This may be
an induction furnace or a furnace that heats the slab by direct
flame action (DFI oxyfuel furnace). In the latter case, the direct
flame action of the slab is provided by a gas jet containing 75%
oxygen mixed with a gaseous or liquid fuel. A soaking furnace, a
roller hearth furnace, or a walking-beam furnace, i.e. pusher-type
furnace, may also be used as the additional furnace.
[0013] An additional cooling line may also be used as the
temperature-influencing element. This may be an intensive cooler or
a laminar strip cooler, for example.
[0014] Finally, a thermally insulating element (roller grippers)
may also be used as the temperature-influencing element.
[0015] The temperature profile is preferably determined on the
basis of a structural model. The structural model preferably
specifies and/or monitors the following parameters: the temperature
profile over time or the number of passes, the reduction
distribution over time or the number of passes, the holding or
cycle times, the roller speeds and transport speeds, and/or the
heating and cooling intensities.
[0016] One refinement provides that by use of a
temperature-influencing element in the form of a cooler, an input
temperature may be achieved in the finishing roll stand that is low
enough that the recrystallization and grain growth at that location
are largely halted, the temperature level between the input into
the roughing roll stand and the input into the
temperature-influencing element in the form of a cooler being
[0017] a) decreased, in particular for pipe steel having a low
microalloy element content and small slab thickness, by a
temperature-influencing element in the form of a cooler in order to
reduce the grain size upon entry into the finishing roll stand,
or
[0018] b) increased, in particular for pipe steel having a high
microalloy element content and large slab thickness, by a
temperature-influencing element in the form of a heater to ensure
complete recrystallization during roughing, or
[0019] c) merely balanced and otherwise left unchanged.
[0020] According to one refinement, using a temperature-influencing
element in the form of a heater makes it possible to achieve an
input temperature in the finishing roll stand that is high enough
that complete recrystallization takes place at that location,
either
[0021] a) during the first finishing passes due to the high
temperatures and reductions, followed by an accumulation of
deformation in the last finishing passes, or
[0022] b) only during the last finishing passes due to moderate
temperatures and reductions, after prior accumulation of
deformation has taken place.
[0023] According to the invention, the installation for making
microalloyed steel, in particular a pipe steel, having a casting
machine, a first furnace, at least one roughing roll stand, a
second furnace, at least one finishing roll stand, and a cooling
line in this order in the travel direction of the slab, is is
characterized in that a temperature-influencing element for setting
the temperature of the slab may optionally be introduced into the
process line between the first furnace and the roughing roll stand,
and/or between the second furnace and the finishing roll stand, the
temperature-influencing element being selectable from one of the
following elements: an additional furnace, an additional cooling
line, or a thermally insulating element.
[0024] One refinement provides that at least one of the
temperature-influencing elements comprising the additional furnace,
additional cooling line, and thermally insulating element is made a
transversely displaceable with respect to the travel direction of
the slab in such a way that one of the elements may optionally be
introduced into the process line.
[0025] At least one of the elements comprising the additional
furnace, additional cooling line, and thermally insulating element
may be configured to be pivotal about an axis extending in the
travel direction in such a way that one of the elements may
optionally be introduced into the process line.
[0026] By using the proposed approach, improved manufacture of
microalloyed steel, in particular pipe steel (such as X52 to X120,
for example), is possible, resulting in favorable property
combinations. Optimal values of strength and ductility, in addition
to maximum flexibility with regard to the chemical compositions
used, as well as the dimensions of the final product are achieved
as the result of targeted control of the temperature variation. The
limitations that have existed heretofore on the basis of customary
process control may be largely eliminated using the proposal
according to the invention. The application of a desired
temperature-time curve is advantageously achieved for manufacture
of the steel, thus allowing production of extremely high-quality
pipe steel.
[0027] According to the proposed procedure, upstream of the
roughing stage as well as between the roughing stage and the
finishing stage the temperature may be increased, held constant, or
decreased. Maximum flexibility with regard to temperature control
is thus achieved that opens up not only the basic possibility for
manufacturing pipe steel, but also allows different procedures for
manufacturing these types of steel and setting various material
properties, depending on requirements.
[0028] In addition, many other types of steel for which the
temperature variation plays an important role may be manufactured
much more easily, and in certain cases, with improved properties,
which is the case for multiphase steels and all types of
microalloyed steel, for example.
[0029] Finally, changed reduction distributions may be used, and in
particular higher reductions may be carried out by the altered
temperature variations. This also results in lower achievable final
thicknesses for all types of steel, and also additional
possibilities for installation design.
[0030] The use of effective heaters (inductive heaters or furnaces
according to the DFI oxyfuel process) and/or the use of adjustable
intensive coolers (for example, instead of exposing roughed strips
in air) further increase the overall productivity of the
installation, or simplify the production process.
[0031] Thus, the proposed procedure or apparatus allows targeted
influencing of the temperature of the slab before roughing, on the
basis of material analysis, material dimensions, and material
properties. Likewise, targeted influencing of the temperature of
the roughed strip before finish milling on the basis of material
analysis, material dimensions, and material properties is
possible.
[0032] Temperature control during the individual process steps is
preferably done in a targeted manner by use or application of a
structural model. As previously mentioned, the structural model
sets the course of and monitors the following parameters: [0033]
Temperature profile over time or a number of passes, [0034]
Reduction distribution over time or a number of passes, [0035]
Holding or cycle times, [0036] Roller speeds and transport speeds
for influencing the temperature profile, [0037] Heating and cooling
intensities.
[0038] Furthermore, targeted control of the various types of
softening processes during the individual process steps and
associated control of the material properties may be achieved.
[0039] The method may be used for various thermomechanical
treatments.
[0040] Slab cooling may be incorporated upstream of the roughing of
the slab in the roughing roll stand. Likewise, an induction heater
or a DFI oxyfuel heater may be incorporated upstream of the
roughing in the roughing roll stand.
[0041] The various cooling and heating units may be exchanged for
one another by sliding or pivoting out.
[0042] The maximum achievable reductions and the overall reduction
distribution may be influenced by a targeted temperature increase
upstream of the rough milling and finish milling, with effects on
the dimensions and properties of the product and the installation
design.
[0043] The productivity of the rolling installation is thus
increased by targeted (additional) cooling and/or heating.
[0044] Embodiments of the invention are illustrated in the
drawings, in which:
[0045] FIG. 1 schematically shows a casting rolling installation in
side view according to a first embodiment of the invention, having
a casting machine, first furnace, roughing stage, second furnace,
finishing stage, and cooling line(s);
[0046] FIG. 2 shows a design alternative to FIG. 1 of the casting
rolling installation according to a second embodiment;
[0047] FIG. 3 shows a further design alternative to FIG. 1 of the
casting rolling installation according to a third embodiment;
[0048] FIG. 4 shows a further design alternative to FIG. 1 of the
casting rolling installation according to a fourth embodiment;
[0049] FIG. 5 shows a further design alternative to FIG. 1 of the
casting rolling installation according to a fifth embodiment;
[0050] FIG. 6 shows a further design alternative to FIG. 1 of the
casting rolling installation according to a sixth embodiment;
[0051] FIG. 7 schematically shows a casting/rolling installation in
top view according to a further embodiment;
[0052] FIG. 8 schematically shows temperature-influencing elements
of the casting rolling installation, viewed in the travel direction
of the slab, according to a first embodiment of the invention;
[0053] FIG. 9 shows a further design alternative to FIG. 8 of the
temperature-influencing elements according to a second embodiment
of the invention;
[0054] FIG. 10 shows a further design alternative to FIG. 8 of the
temperature-influencing elements according to a third embodiment of
the invention; and
[0055] FIG. 11 shows a further design alternative to FIG. 8 of the
temperature-influencing elements according to a fourth embodiment
of the invention.
[0056] FIG. 1 shows an installation 2 for casting and rolling in a
line of pipe steel (according to API Specification 5L), in the side
view. The installation has a casting machine 3 (vertical casting
installation or curved casting installation) in which a slab 1 is
produced in a known manner by continuous casting. A thickness
between 50 and 150 mm and a width between 900 and 3000 mm are
typical dimensions of the slab. In a travel direction F, the
casting machine 3 is followed by a first furnace 4, a roughing
stage for rolling the slab, only a single roughing roll stand 5
being illustrated (multiple roughing roll stands are sometimes
provided), a second furnace 6, a finishing stage for rolling the
slab or strip, only a single finishing roll stand 7 being
illustrated (multiple finishing roll stands are usually provided),
and a cooling line 8.
[0057] Further elements are also present that are not important or
that are only secondary with regard to temperature control. Shears
12 are provided between the casting machine 3 and the first furnace
4, by means of which the slab 1 may be cut to a desired slab length
(alternatively, a flame cutting installation may be used). A
descaling sprayer 13 is provided between the first furnace 4 and
the roughing roll stand 5. An additional descaling sprayer 14 is
located directly upstream of the finishing roll stand 7. A reel 15
that winds the finished strip is provided in a known manner
downstream of the cooling line 8.
[0058] For pipe steel there are increased demands with regard to
temperature control of the slab or strip on the path through the
installation 2.
[0059] Before the strip is manufactured, first the desired
temperature profile over time or along the production path in the
travel direction F is determined. For this purpose a computerized
structural model is preferably used that is known per se and is
used by those skilled in the art to specify the intended
temperature curve of the slab 1 or strip so that an optimal product
may be produced. Examples of such temperature variation are given
below, in that temperature ranges of the slab 1 or strip are
provided for particular locations in the production installation
2.
[0060] Depending on the specified temperature profile, the
installation 2 is to be prepared in such a way that the desired
profile may be followed. According to the invention, this is
achieved in such a way that at least one temperature-influencing
element for setting the temperature of the slab 1 according to the
defined temperature profile is provided in the process line of the
installation 2, the temperature-influencing element being
introduced between the first furnace 4 and the roughing roll stand
5, and/or between the second furnace 6 and the finishing roll stand
7.
[0061] In the embodiment according to FIG. 1, the
temperature-influencing element 9 is a cooling line that is
effectively introduced into the process line, downstream of the
second furnace 6. This may be an intensive cooler or a laminar
cooler, depending on the cooling power required for achieving the
desired temperature profile.
[0062] After cooling and passing through the descaling sprayer 14,
continuous or reversible finish milling is carried out in the
finishing roll stand 7, a number of finishing roll stands, i.e. a
finishing roll stand group, preferably being provided. The finish
milling is carried out to the desired finished strip thickness and
finished strip temperature, followed by cooling of the strip in the
cooling line 8. As the last step, the strip is wound onto the reel
15. Alternatively, instead of winding the finished rolled strip,
the strip may be sent directly to the finishing shop.
[0063] A temperature range from 850 to 950.degree. C. downstream of
the furnace 6 and the cooler 9 is provided for finish milling pipe
steel within the scope of a classical thermomechanical treatment.
The low input temperature ensures that during the essentially
isothermal rolling in the finishing stage, recrystallization and
grain growth are largely halted, and practically the entire
deformation is accumulated, resulting in a very finely grained is
structure in the subsequent conversion. Other prerequisites are a
sufficiently low final rolling temperature of typically less than
820.degree. C. and a sufficiently high cooling rate in the cooling
line.
[0064] However, in addition to the above-described cooling in the
region between the roughing roll stand 5 and the finishing roll
stand 7, it may be necessary to influence the temperature of the
strip before entry into the roughing roll stand 5. In this regard,
FIG. 2 shows an installation 2 for manufacturing pipe steel
according to API in which the downstream section of the first
furnace 4 has been replaced by a strip cooler 10. Stated more
precisely, in this case an additional cooling line 10 has been
introduced into the process line as the temperature-influencing
element 10.
[0065] Cooling the slab further increases the extent of the
thermomechanical treatment and may limit grain growth between the
shaping mill and finish roll stands. However, complete
recrystallization must still be ensured, which makes this procedure
suitable in particular for pipe steel having a low content of
microalloy elements and fairly small slab thicknesses.
[0066] In contrast, for particularly high content of alloy elements
and large slab thicknesses, heating to even higher temperatures may
be useful to allow higher deformation rates and to ensure complete
dynamic or static recrystallization. In addition, the increased
temperature may have a favorable effect on the solution condition
of the microalloy elements. One embodiment of the invention that
makes this possible in a particularly advantageous manner is
illustrated in FIG. 3. Here, a temperature-influencing element 10
in the form of an inductive heater has been introduced into the
process line, downstream of the first furnace 4 and upstream of the
roughing roll stand 5.
[0067] FIGS. 4, 5, and 6 show installation designs in which the
main difference from the approach according to FIGS. 2 and 3 is
that the strip cooler provided upstream of the finish milling has
been replaced by an induction heater or furnace.
[0068] Whereas a classical thermomechanical treatment having the
aim of maximizing the accumulated deformation has been sought
heretofore, for certain steel a different method is to be used.
Instead of dispensing with further softening in the region of the
finishing stage after complete recrystallization following
roughing, repeated recrystallization is the aim. This
recrystallization requires high temperatures that may be produced
in a particularly advantageous manner using an induction heater or
a DFI oxyfuel furnace. The recrystallization may be carried out at
particularly high temperatures and deformation rates during the
first finishing passes, and may be followed by accumulation of
deformation in the last finishing passes, or alternatively, dynamic
recrystallization occurs at lower temperatures and deformation
rates only during the last finishing passes, after accumulation of
deformation in the first finishing passes has taken place. In
comparison to the classical thermomechanical treatment, for example
according to the approaches according to FIGS. 1, 2, and 3, in both
of the above-mentioned cases as a result of the temperature
increase the maximal possible deformation rate increases while the
deformation required for initiating recrystallization decreases, is
thus greatly increasing the tendency toward softening.
[0069] As the result of expanding the options according to the
invention for influencing temperature, previous conflicting
requirements for the temperature variation may be met in the
individual installation zones, thus enabling the optimal course of
the process in each individual zone with regard to the product
properties, i.e. following an optimally selected temperature curve
in the slab or strip along the travel direction F. This provides a
flexible adaptation to desired material properties, material
dimensions, or different material analyses.
[0070] At the same time, influencing temperature control is a
powerful tool for distributing the load and reduction in the
shaping and finishing roll stands used to reduce the minimum
achievable final thicknesses, or to employ smaller units in the
design.
[0071] The description of the numerous effects of the temperature
variation on the microstructure illustrates that control of the
structural development is necessary at all times, and that the
rolling of pipe steel according to the proposed procedure results
in the desired mechanical properties in particular when the process
is monitored and/or controlled or regulated by a suitable
structural model.
[0072] For rolling standard steel in the same installation,
temperatures of approximately 1000 to 1150.degree. C., or in
special cases higher or lower temperatures, are generally used
upstream of the finishing stage. The necessity of setting differing
temperatures becomes greater with increasing complexity of the
alloy design. This procedure is particularly advantageous for
multiphase steels and various microalloyed steel. By using the
proposed installation design, in most cases slabs, thin slabs,
intermediate strips, strips, and sheets may be brought to the
sought temperature level, so that there are no restrictions with
regard to the required material properties.
[0073] For optimal adaptation to the particular process conditions,
the strip cooler 9 (in FIGS. 1, 2, and 3) and the induction heater
10 (in FIGS. 3 and 5) or 9 (in FIG. 4) are designed to be shiftable
or pivotal transverse to the travel direction F, and either one or
the other of units 9, 10 may be activated.
[0074] Similarly, as an alternative to FIG. 4, according to FIG. 6
instead of the strip cooler 10 or induction heater 9 a conventional
soaking furnace 9, 10 may be introduced into the process line. This
applies for the various units upstream and downstream of the
shaping mill installation.
[0075] The casting machine 3 may be provided in the process line
with the roll stand 5, or may be spatially separated from it. For
this purpose, reference is made to FIG. 7 that shows a
corresponding example in the top view. In this case two upper
casting machines 3' are provided in parallel, downstream of which
the slab is cut to a desired length by flame cutting machines 12'.
By use of a walking-beam furnace 4' or pusher-type furnace the slab
1 may be displaced from the two upper process lines L to the lower
process line L, in a direction Q transverse to the travel direction
is F; the further installation parts for manufacturing the strip
are located in the lower process line. The lower process line L
likewise has a casting machine 3 downstream of which shears 12 are
provided.
[0076] The slab 1 is heated to a roughing temperature of
approximately 1100 to 1200.degree. C. by furnaces 4, 4'. Roughing
is carried out downstream of the descaling sprayer 13 continuously
or reversibly on one, or alternatively multiple, roughing roll
stands 5 to produce an intermediate thickness.
[0077] The furnace input temperature may also be influenced by the
selection of the roller speed at the roughing roll stand 5.
[0078] A second furnace 6 in the form of a holding furnace is
provided downstream of the roughing roll stand 5. The holding
furnace 6 provides enough space to completely accommodate a thin
slab that has been shaped in the roughing roll stand 5. Brief
cycling of the shaped thin slab may also take place in the furnace
6.
[0079] Instead of a holding furnace 6, in this case roller grippers
or a standard roller table may be provided. Subsequent to the
furnace 6 or the roller grippers, a temperature-influencing element
9 in the form of a cooling line is positioned in the process line
L, by means of which the slab 1 may be brought to the desired
temperature before the finish milling in the finishing roll stand
7. Alternatively, the strip cooler 9 may be provided upstream of
the holding furnace or the roller grippers.
[0080] Details concerning exchange of the various units by lateral
displacement or pivoting in and out of the temperature-influencing
elements 9, 10 are shown in FIGS. 8 through 11. In addition, three
different units may share a space in the process line by optionally
providing suitable displacement devices.
[0081] FIG. 8 shows the manner in which an additional furnace (left
side of FIG. 8) or an induction furnace (right side of FIG. 8) may
alternatively be moved into the process line L by displacement in
transverse direction Q. Offset positions 16, 16' on both sides of
the process line L allow the two furnaces to be simultaneously
moved from the illustrated position to the right, and vice
versa.
[0082] The analogous situation is illustrated in FIG. 9 for
temperature-influencing elements 9, 10 that may alternatively be
introduced in the form of a cooler (left side of FIG. 9) and an
induction furnace (right side of FIG. 9) into the process line L.
Once again, this applies for FIG. 10 for a roller hearth furnace
(left) and a slab cooler (right).
[0083] As shown in FIG. 11, a temperature-influencing element 9 in
the form of a cooling bar may be pivoted about an axis 11 for
engagement or disengagement. However, the induction furnace 10 is
once again provided so as to be transversely displaceable in
direction Q in order to disengage it by moving it into the
deflection position 16'.
TABLE-US-00001 List of reference numerals: 1 Slab (strip) 2
Installation 3 Casting machine 3' Casting machine 4 First furnace
4' Walking-beam furnace or pusher-type furnace 5 Roughing roll
stand 6 Second furnace 7 Finishing roll stand 8 Cooling line 9
Temperature-influencing element 10 Temperature-influencing element
11 Pivot axis 12 Shears 12' Flame cutting installation 13 Descaling
sprayer 14 Descaling sprayer 15 Reel 16 Deflection position 16'
Deflection position F Travel direction Q Direction of transverse
displacement L Process line
* * * * *