EP2591128A1

EP2591128A1 - Method and production line for producing a cold rolled flat steel product from a rustproof steel

Info

Publication number: EP2591128A1
Application number: EP11738649.0A
Authority: EP
Inventors: Ian Mackenzie; Christian Bartholdt
Original assignee: Andritz Sundwig GmbH
Current assignee: Andritz Metals Germany GmbH
Priority date: 2010-07-09
Filing date: 2011-07-01
Publication date: 2013-05-15
Also published as: JP2013536082A; BR112013000536A2; ZA201300198B; RU2013105473A; WO2012004205A1; US20130205855A1; DE102010026757A1; RU2562599C2; TW201211269A; KR20130027051A; DE102010026757B4; AU2011275945A1

Abstract

The invention relates to a method and to a correspondingly designed production line (1) for producing a cold rolled flat steel product (E) from a scale coated hot strip (W) made of a rustproof steel. In the course of the method according to the invention, the hot strip (W) coated with scale is cold rolled to form the flat steel product, the cold rolled flat steel product (E) is annealed, and the annealed flat steel product (E) is descaled. According to the invention, the cold rolled flat steel product (E) obtained after cold rolling the hot strip (W) is subjected to a descaling treatment in the hard rolled state prior to annealing, wherein the scale present on the cold rolled flat steel product (E) is mechanically removed. In this manner, methods and production lines can be implemented, by means of which it is possible to produce cold rolled flat steel products from rustproof steel having improved surface finish in a cost-effective manner.

Description

METHOD AND PRODUCTION LINE FOR MANUFACTURING A COLD-ROLLED STEEL FLAT PRODUCT FROM ONE NOT

ROSTEN STEEL

The invention relates to a method for producing a cold-rolled steel flat product from a

scaled, made of a stainless steel

existing hot strip in which the hot-rolled strip is cold-rolled to the flat steel product, wherein the cold-rolled flat steel product is annealed and the cold-rolled flat steel product is descaled.

Moreover, the invention relates to a

Production line for producing a cold-rolled stainless steel

Flat steel product, wherein the production line at least one cold rolling stand, at least one annealing furnace and

comprising at least one device for removing scale adhering to the cold-rolled steel flat product.

Here, the term "flat steel products" here from a stainless steel or a so-called "stainless steel" produced steel strips or sheets understood. In the course of the production of cold-rolled

Stainless steel flat products will be suitable

composite molten steel to a precursor, such as slabs, thin slabs or cast strip, cast, from which a hot strip is then hot rolled and wound into a coil. The hot strip obtained and, if necessary, subjected to a supplementary heat treatment is then cold-rolled one or more stages into a cold strip with the scale adhering to it.

In the course of cold rolling, hardening of the rolled steel strip occurs, as a result of which the cold strip obtained after cold rolling can at best be reduced to a very reduced extent. To eliminate this so-called "work hardening", that will

Cold strip is usually subjected to a heat treatment in which it is annealed at sufficiently high annealing temperatures. The then still existing fine and firmly adhering to the surface scale particles can in one

Pickling can be eliminated, through which the cold strip is passed after the mechanical scale removal.

A typical example of a production line of the type described above is known from DE 691 26 699 T2 (EP 0 509 177 B1). In order to increase the efficiency with which the scale adhering to the annealed strip is removed, according to this prior art, the pickling device may have a mechanically acting one

Descaling device can be combined.

In practice, a scale breaker is used in the coarser pieces of adhering to the annealed strip Zunders are removed. In addition, a ball-blasting or a brushing device is usually provided, which mechanically releases any larger scale particles that still exist from the cold-rolled strip on emerging from the scale breaker. At the end of production, the cold-rolled strip is, if necessary, still temper rolling after leaving the pickling device in order to improve its yield strength and dimensional stability.

Practical experiences show that with a

Production line of the type mentioned above, although at low cost large quantities of cold-rolled

Steel flat products can be produced from a stainless steel. However, that's enough

Surface quality of steel flat products produced with such production lines often do not meet today's requirements.

Against this background, the object of the invention was to provide a method and a production line which is particularly suitable for carrying out such a method, with which it is possible in a cost-effective manner to produce cold-rolled stainless steel flat products with improved surface quality.

In terms of the procedure is this task

According solved according to the invention that in the production of cold-rolled steel flat products made of stainless steel, the steps specified in claim 1 are performed. In terms of the production line, there is the

inventive solution of the above object is that such a line has the features specified in claim 13.

Advantageous embodiments of the invention are set forth in the dependent claims and will become hereafter as the general inventive concept in detail

explained.

Like the prior art explained at the outset, the method according to the invention for producing a

cold-rolled steel flat product assumes that

Scalloped, made of a stainless steel

existing hot strip, so-called "black plate" is cold rolled without previous descaling. Furthermore, the method according to the invention comprises a

Annealing treatment to the cold rolled material too

entfestigen. Likewise, according to the invention a

Descaling takes place to rid the cold-rolled steel flat product from the tinder adhering to it.

According to the invention, the cold-rolled flat steel product obtained after the cold rolling of the hot strip is now in the hard-rolling state before the annealing of a

Subjected to a descaling treatment in which scale present on the cold-rolled steel flat product is mechanically removed. When inventive

Thus, a mechanical descaling is carried out on the still hard-cold cold strip before the cold strip is subjected to annealing. In this case, on the one hand, the invention makes use of that part of the scale already broken during cold rolling and itself

accordingly easy from the cold-rolled

Solve flat steel product leaves.

This procedure has the advantage that the cold-rolled cold strip is comparably insensitive to the forces acting on its free surfaces during mechanical descaling. This is what happens with the mechanical

Scale removal of the hard material only too

Surface deformations that are much lower than those resulting from conventional descaling of post-annealed, comparably soft steel strips.

The steel flat product largely freed from coarser scale in the manner according to the invention then passes through a conventional annealing device in which it is annealed in a manner known per se in order to obtain the same

Solidification occurring in the course of cold rolling and optionally in the mechanical

Descaling is further increased.

On the other hand, unlike the annealing of corrosion-sensitive flat steel products, in the subsequent annealing of steel strips or sheets made of stainless steels, only small amounts of new scale are formed on the surface of the respective flat steel product. These can be

then remove safely in a conventional pickling device. Another mechanical descaling between the exit from the annealing furnace and the inlet in the pickling therefore explicitly according to the invention does not take place.

Instead, after annealing, the stainless steel strip may optionally undergo a planarity improvement device. In the prior art, for example, stretch bending devices or the like are used for this purpose.

The above-explained features of

According to the method of the invention, a production line according to the invention for producing a cold-rolled steel flat product comprising a stainless steel comprises at least one cold rolling stand, at least one annealing furnace and at least one device for mechanically removing scale adhering to the cold-rolled steel flat product, the at least one device for mechanically removing the scale is arranged in the conveying direction of the cold-rolled steel flat product before the entrance of the annealing furnace.

Due to the minor damage, which in the according to the invention after the cold rolling and before the

Annealing carried out descaling, have produced in accordance with the invention, made of a stainless steel steel strips and sheets on an optimized surface finish. This optimization succeeds solely in that the mechanical descaling is carried out in front of the annealing furnace. The necessary facilities are already available in conventional production lines, but are used according to the invention elsewhere. As a result, arise by the procedure of the invention with a significant increase in the quality of the obtained

Product no additional costs.

Of course, the invention before the

Annealing furnace taking place mechanical descaling by means of several, optionally consecutively traversed or combined acting methods

be performed. Thus, it is conceivable to carry out the mechanical descaling by particle beams, such as sand or shot peening, or by brushing, wherein these descaling possibilities can be particularly effective if they are combined with one another in a corresponding device or carried out in separate beam and brush directions ,

In particular, when the descaling is to be carried out by a particularly gentle blasting using fine particles, it is expedient, before the blast treatment on the surface of the

Flat product to dry or remove any existing liquids as far as possible. In this way it prevents the on the

Surface of the hard steel flat product hit particles with the otherwise still existing on the surface, derived from the previous processing stages liquids such as rolling oil residues or

Likewise, mix to a difficult to remove mass that obstructs the desired scale removal. The removal of the liquid residues can be done by a thermal treatment. For this purpose, for example, a flame drying, in which the to cleaning surface is exposed to an open flame, so that the existing on the surface

Vaporize or burn liquids quickly.

Highly efficient, the flame drying can be achieved by using a so-called "booster", which the

Application of an enveloping flame enveloping the liquid to be liberated band allowed. Such a booster is described for example in DE 10 2006 005 063 AI.

If the removal of the scale from the hard rolling

cold-rolled steel flat product by a

Blast treatment, this treatment may be considered

Liquid jets, for example

High pressure water jets are performed. In order to increase the effectiveness of the scale removal, the liquid steel agent can carry particles with it, which abradingly remove the scale adhering to the cold-rolled, hard-rolled steel flat product. The particles concerned may be scale particles obtained from the scale removed from the cold-rolled steel flat product.

It is likewise conceivable to use a conventional scale breaker for mechanical descaling, in which the scale adhering to the cold-rolled, flat-rolled steel flat product is broken by deflecting the flat steel product on at least one roll.

In order to optimize the dimensional accuracy, the surface roughness and the mechanical properties of steel flat products produced according to the invention, the cold rolled Flat steel product can optionally be tempered or tempered after annealing.

Depending on the number of performed

Cold rolling steps and the available

Plant technology, the inventive method can be completed discontinuously or in continuous flow. In the discontinuous

Carrying out, for example, the cold rolling

take place in several stages in a reversing stand operated independently of the operation of the annealing furnace. This has the advantage that a high overall deformation of the cold strip with a correspondingly high work hardening and a concomitantly particularly hard, against the

mechanical scale removal insensitive surface can be achieved.

The implementation in a continuous run is useful, for example, when large quantities of

Steel flat products are to be produced in a time-saving manner and over the one or more available, run in the continuous cold rolling stands, a sufficient reduction in thickness can be achieved. Fluctuations in the conveying speed between the individual workstations of such a continuous production line according to the invention can thereby be compensated by arranging at least one strip store in the conveying path of the flat steel product.

An inventively produced, made of a stainless steel flat steel product has a Surface roughness Ra on, which is regularly in the range of 0.1 - 1 μνα, without that on the

The procedure according to the invention requires additional measures. Particularly low surface roughness results in this case when the stainless steel strip is post-rolled after annealing at degrees of deformation of up to 10%, in particular 1-7%.

Hereinafter, the invention with reference to a

Embodiment illustrative drawing closer

explained.

The only figure shows a continuous

Pass in the conveying direction F passed

Production line 1 for producing a cold-rolled stainless steel strip E.

The production line 1 comprises one behind the other in the conveying direction F in line

a uncoiling device 2 for the successive unwinding of hot strips W wound to coils C1, C2, which consist of a stainless steel and on whose surface the scale resulting from the hot strip production still adheres,

a welding device 3, which serves to connect the end of the hot-rolled strip W wound to one coil Cl to the beginning of the hot strip W wound to the other coil C2, when the first hot-rolled strip is completely fed into the production line 1, a first band memory 4 for equalizing

Variations in the conveying speed of the in the

Production line 1 fed hot strip W,

- three rolling stands 5,6,7, which are

Conventional, from the prior art in

different designs known cold rolling stands and in which the hot strip W is cold rolled in three successive stages to stainless steel strip E,

a second band memory 8 for equalizing

Fluctuations in the conveying speed of the stainless steel strip E emerging from the cold rolling stand 7,

a first descaling device 9 in which the adhesive on the stainless steel strip E, in consequence of the

Passing through the cold rolling stands 5,6,7 occurred elongation of the stainless steel strip E broken scale is mechanically removed by shot peening of the stainless steel strip E,

- A second descaling device 10, in which the on the stainless steel strip E after leaving the

Ent scaling device 9 still adhering scale is removed by brushes of the stainless steel strip E mechanically,

- A continuous annealing furnace 11, in which the mechanically descaled stainless steel strip E after leaving the

Descaling device 10 in continuous

Pass over such a long glow time to one

sufficiently high annealing temperature is heated that the in the course of cold rolling and mechanical

Descaling of solidifications of the

Stainless steel strips E are removed and a sufficiently soft stainless steel strip E is obtained for further forming operations,

- one after the continuous annealing furnace 11 without an intermediate mechanical processing of

Surface of stainless steel band E traversed

Stretch bender 17 for improving the flatness of the stainless steel strip E,

- One in connection to the device 17 without a

intermediate mechanical processing of the

Surface of stainless steel band E traversed

Pickling 12 for removing the on the

Stainless steel band E still existing Zunders by chemical means,

- Another band memory 13 for balancing

Fluctuations in the conveying speed of the annealed from the continuous annealing furnace 11 annealed

Stainless steel bands E,

- An arranged in the outlet of the tape storage 13

Temper rolling stand 14 for re-rolling the stainless steel strip E with a total deformation degree of up to 10%,

a last band memory 15 for equalizing

Fluctuations in the conveying speed of the emerged from the temper rolling mill 14 annealed

Stainless steel bands E and

a reeling device 16 equipped with two reels which are used alternately for rewinding the stainless steel strip E leaving the strip store 15

The unwound from the in each case in use coils Cl or C2, afflicted with scale, optionally in the welding device 3 with the end of the previously

processed hot strip W connected, produced from a stainless steel in a conventional manner

Hot strip W is fed via the strip accumulator 4 into the first cold rolling stand 5 and then cold-rolled in the subsequently passed through cold rolling stands 6, 7 in a total of three stages to the cold-rolled stainless steel E. As a result of the reduction in thickness occurring via the cold rolling stands 5, 6, 7, the stainless steel strip E is elongated so that the scale adhering to it flakes off the hot strip W in coarse pieces as a result of the occurring surface tensions.

The after leaving the last cold rolling stand 7 on the now obtained to target thickness cold rolled, solidified as a result of cold rolling stainless steel strip E still

adhesive tinder will be in the first

Descaling device 9 mechanically descaled by directing a particle beam of high kinetic energy against the solidified surfaces of the stainless steel strip E. The particle beam may, for example, be a shot blast, as already used in the prior art for descaling, but elsewhere in the process. In the second Entzunderungseinrichtung 10 of the thus mechanically descaled stainless steel strip E of the there still existing scale brushed by brushes. Upon leaving the Entzunderungseinrichtung 10 and

Running into the continuous annealing furnace 11 therefore adhere only small, fine scale residues on the surface of the stainless steel strip E.

As an alternative or in addition to the devices 9, 10, a descaling device (not shown here) can be provided in which the scale adhering to the stainless steel strip E is removed by means of a high-pressure liquid jet. The applied under high pressure and with high kinetic energy on the belt surface to be descaled

Liquid jet can carry particles with it in order to increase the effectiveness of the scale removal. These particles can be trapped

Zunderteilchen act a certain grain size, which are the jet liquid, such as water, mixed.

When passing through the continuous annealing furnace 11, the stainless steel strip E is heated to a temperature at which the solidified structure of the stainless steel strip E softens again. The length of the continuous annealing furnace 11, the throughput speed and the annealing temperature are matched to one another in such a way that the desired microstructure hardening at the end of the continuous annealing furnace 11 is completed. Of course, the

Continuous annealing furnace 11 may be divided into several zones for this purpose, in which different temperatures prevail in order to achieve an optimum glowing result. Due to its alloy and the consequent minimized sensitivity to corrosion, it forms on the

Stainless steel band E only a small amount of new Zunders.

The on the stainless steel band E at the exit from the

Annealing furnace adhering amount of scale is so small that it is largely completely removed from the surface of the stainless steel strip E in the pickling device 12 by the action of it acting on the stainless steel strip E mordant. Before entering the pickling device 12, however, the stainless steel band E still passes through in

Conveying direction F behind the annealing furnace 11 arranged

Stretch bending device 17. In this is the

Stainless steel band E in a conventional manner by

multiple changes of direction so deformed that it at the immediately following entry into the subsequently swept pickling 12 a total

has improved flatness. The temper rolling carried out after discharge from the pickling device 12 serves, in particular, to improve the surface roughness of the stainless steel strip E, wherein in addition the dimensional stability and the mechanical properties are optimized before it is wound into a coil 3 or 4 in the coiling device 16. As a result of the secondary rolling carried out at deformation levels of typically 5-7%, the surface roughness values can be approximately halved, so that after the final rolling an optimally smooth product is available. REFERENCE NUMBERS

1 production line

2 uncoiling device

3 welding device

4 tape storage

5,6,7 cold rolling stands

8 tape storage

9 First Entzunderungseinrichtung

10 second descaling device

11 continuous annealing furnace

12 pickling device

13 tape storage

14 temper rolling mill

15 tape storage

16 reel device

17 Planarity improvement facility

C1, C2 coils made of hot strip W

E stainless steel bracelet

F conveying direction

W hot strip

Claims

P A T E N T A N S P R E C H E

Method for producing a cold-rolled

A flat steel product (E) of a scale-bearing stainless steel hot-rolled strip (W) in which the tindered hot strip (W) is cold rolled to the flat steel product (E), where the cold-rolled flat steel product (E) is annealed and annealed the cold-rolled steel flat product (E) is descaled by

e) in that the cold rolled flat steel product (E) obtained after the cold rolling of the hot strip (W) is subjected to a descaling treatment before being annealed in the hard rolled state, on the cold rolled

Steel flat product (E) existing scale is mechanically removed.

The method of claim 1, d a d u r c h

characterized in that the descaling of the cold-rolled, hard-rolled flat steel product (E) carried out before the annealing is carried out by blasting with solid particles.

3. Method according to one of the preceding claims, characterized in that liquid residues present on the cold-rolled, hard-rolled steel flat product (E) are present on the cold-rolled, flat-rolled steel flat product (E)

Descaling can be removed by a thermal treatment.

4. Method according to one of the preceding claims, wherein the descaling of the cold-rolled, hard-rolled steel flat product (E) carried out before the annealing is carried out by brushing.

5. Method according to one of the preceding claims, characterized in that descaling of the cold-rolled, hard-rolled steel flat product (E) carried out before annealing is carried out by liquid jets.

6. The method of claim 5, d a d u r c h

e n c ia n, the s

Fluid jets carry particles that are hard to cold rolled on the cold rolled

Abrasive wear of flat steel product (E).

7. The method according to any one of the preceding claims, characterized in that the carried out before the annealing descaling of cold-rolled, hard-cold rolled flat steel product (E) by redirecting the flat steel product

at least one role of a scale breaker takes place.

8. Method according to one of the preceding claims, characterized in that the cold-rolled flat product (E) after annealing optionally passes through a device for improving its flatness and is pickled.

9. Method according to one of the preceding claims, characterized in that the cold-rolled flat product (E) is tempered or re-rolled.

10. Method according to one of the preceding claims, characterized in that its work steps are discontinued discontinuously.

11. The method according to any one of claims 1 to 9,

d a d u r c h e c e n c e s, his work steps are completed in a continuous cycle.

12. The method according to any one of the preceding claims, characterized in that the obtained cold-rolled, from a non existing stainless steel flat product (E) a 0.1-1 μηα, in particular 0.3-0.7 μπ,

having sufficient surface roughness Ra.

13. Production line for making one out of one

stainless steel cold rolled flat steel product (E) comprising at least one cold rolling stand (5, 6, 7), at least one annealing furnace

(11) and at least one device (9, 10, 12) for the mechanical removal of scale adhering to the cold-rolled steel flat product (E),

d a d u r c h e k e n c i n e, that is, the at least one device (9, 10) for

mechanical removal of the scale in the conveying direction

(F) of the cold-rolled steel flat product (E), as seen in front of the entrance of the annealing furnace (11).

14. The production line according to claim 13, characterized in that

Cold rolling mill (5,6,7) is independent of the operation of the annealing furnace (11) operated reversing mill.

15. The production line according to claim 13, wherein a

Cold rolling mill (5,6,7), the means (9,10) for removing the scale and the annealing furnace (11) on a conveying path in the conveying direction (F) of the

Flat steel product (E) seen in such a row are arranged so that they are passed through in a continuous sequence one after the other.

Production line according to claim 15, at least one in the conveying path of the flat steel product (E)

Band memory (4,8,13,15) is arranged.