WO2015110490A1

WO2015110490A1 - Method and system for hot-dip coating hot-rolled steel strips

Info

Publication number: WO2015110490A1
Application number: PCT/EP2015/051175
Authority: WO
Inventors: Andreas Gramer; Werner Haupt; Hartmut Sulenski; Anja Maria Eder; Peter Jollet; Hans Georg Klöckner
Original assignee: Sms Group Gmbh
Priority date: 2014-01-22
Filing date: 2015-01-21
Publication date: 2015-07-30
Also published as: EP3097218A1; DE102015200764A1; CN106103783A; EP3097218B1

Abstract

The invention relates to a method and a system (1; 100) for producing hot-dip coated hot-rolled steel strips (2), preferably in a continuous processing line, comprising a strip pre-treating device (3) for scaling, preferably by means of a pickling, rinsing, and drying process, cold-working devices (8; 11) for reducing the strip thickness, preferably by cold-rolling the strip, and a subsequent post-treatment device, for example for a stretch-bending alignment and/or a chemical post-treatment. In order to allow valuable, zinced strips and strip surfaces to be achieved, the strip pre-treating device (3) for the descaled hot strip is first followed by the thickness-reducing device (8), in which the strip thickness is reduced by less than 30%, preferably 0.5 to 10%, and the thickness-reducing device is then followed by the strip-zincing device (7), in which the hot strip is subjected to a molten bath (9).

Description

Process and plant for hot dip coating of hot rolled

steel strip

The invention relates to a method for hot dip coating of

hot rolled steel strip, preferably in a continuous strip plant, in which the hot strip is subjected to a pretreatment for descaling, is galvanized, is reduced by cold working in its thickness and a

Undergoing post-treatment. Furthermore, the invention relates to a plant for producing hot-dip coated, hot rolled steel strip.

The liberation of the hot strip from the scale (pretreatment) as a prerequisite for cold forming and galvanizing is preferably carried out by pickling, rinsing and drying. For example, a straightening and / or a chemical treatment can be provided for the aftertreatment.

By WO2006 / 097237 A1 (EP 1 861 517 B1) are for

Hot dip galvanized steel strip, a process and equipment having been known to improve the thickness tolerance of controlled thickness reduction which is performed after galvanizing. For this purpose, a rolling stand is provided in the process line, wherein at least one

Thickness gauge in the outlet of the rolling stand, the achievement of the finished thickness is controlled and the deviations from this up or down as a control signal to the employment of the rolling stand are returned to increase the thickness reduction or reduce accordingly. This takes place in a continuous process line, in which the steel strip first by descaling, z. B. by means of a scale breaker, and pickling and rinsing is pretreated, then the steel strip passes through a galvanizing, which is the

Roll stand with the thickness gauge in the outlet for controlled

Thickness reduction connects before the steel band the final

After treatment undergoes, as by straightening and a chemical Treatment. The finished product thus prepared is in a z. B. a tape storage and a trimming scissors having outlet part

Bundled coils with a desired diameter. In this known method, technological disadvantages arise, individually or together for the production of high quality, galvanized

Band surfaces can affect unfavorable. The disadvantages are the fact that for galvanizing the tape roughness must be accepted, which brings the band through the preliminary processes with it. This can be very rough

Tape surfaces and extra thin coating layers

Cause surface problems. Furthermore, the soft zinc layer on the much harder steel strip in the controlled thickness reduction by the necessary high pressures in the nip to achieve the desired decreases in the range of 2 to 30%, preferably 4 to 10%, heavily loaded, resulting in increased abrasion of zinc particles lead, which deposit as dirt on the belt surface and tape cleanliness for downstream

Processes deteriorate. Finally, there is a risk that the zinc layer, the one carried out by the reduction in thickness of the steel base material

Enlargement of the strip surface must be experienced by elongation,

Damage, z. B. cracks, suffers the corrosion protection effect of

Destroy zinc layer.

The invention is therefore an object of the invention to provide a method and a system of the type mentioned, with which can reach high quality, galvanized bands and strip surfaces without the disadvantages mentioned.

This object is achieved with a method according to the invention in that the hot strip removed from the scale is cold-formed in a process step preceding the galvanizing by reducing its strip thickness by less than 30%, preferably 0.5 to 10%. In connection with the implementation of the method is to be considered that the size of the cold forming and thus the reduction of the strip thickness both directly from the percentage ratio of the strip thicknesses, as well as indirectly. B. from the measured and converted ratios of the belt speeds before and after the cold forming, known in practice known as a temper. For all the following thickness reduction data, this means that less than 30% reduction in thickness corresponds to less than 43% of skin pass, and the preferred range from 0.5 to 10% reduction in thickness to 0.5 to 1 1, 1%

equate to.

A preferred procedural measure provides that in the

Cold forming by preferably a cold rolling process the band in one

Cold rolling mill using work rolls with a surface texture with a mean roughness Ra of less than 10 μιτι, preferably 0.2 - 3 μιτι, a surface structure is impressed.

If, according to a further proposal of the invention before the galvanizing, the thickness of the cold-formed strip measured and a deviation from a

Target thickness as a controlled variable for reducing the thickness of the cold forming

is returned, can achieve a controlled reduction in thickness.

According to another proposal of the invention it is provided that before the galvanizing the size of the cold forming, preferably the reduction in thickness, is controlled and regulated to a desired value. By controlling the size of the cold forming, which also includes a determined from the difference in belt speeds in the inlet and delivery of the cold rolling mill, a controlled thickness control is unnecessary when using hot strip with correspondingly narrow hot strip thickness tolerances. At this

Variant result from the over the band length then constant

Cold forming improved constant material properties, eg. B. Yield strength, tensile strength and elongation at break, resulting in controlled

Thickness decrease can not be achieved.

This also applies to a process variant according to the invention, accordingly in a further cold forming subsequent to the galvanizing

Strip surface in a cold rolling mill by temper rolling with

surface-structured work rolls at a degree of skin pass of less than 3%, preferably 0.5 to 2%, the strip surface structure of the finished product is applied.

According to another proposal according to the invention with a galvanizing subsequent, further cold forming the strip thickness is reduced by less than 30%, preferably 4 to 10% by cold rolling, wherein measured at least after this further strip deformation the strip thickness and deviations from a target strip thickness as a controlled variable of Cold forming can be supplied.

Optionally, a control can be provided for a constant reduction in thickness.

According to another proposal of the invention, the size of the cold working after galvanizing to reduce the strip thickness can be controlled and controlled to a desired value, which in the use of hot strip with

according to tight hot strip thickness tolerances a controlled

Thickness control makes unnecessary.

In the cold forming after galvanizing work rolls come with a Mittenrauwert of less than 10 μιτι, preferably 0.2 to 3.0 μιτι, used and thereby impress the surface of the strip on the surface structure of the finished product. The inventive method thus provides the conditions to adjust the tape roughness before galvanizing by cold forming to a required value and / or reduce the thickness tolerance before galvanizing by cold rolling and / or reduce the strip thickness by cold rolling before galvanizing to a desired level, single of the aforementioned parameters Tape roughness, tape thickness tolerance and tape thickness can be adjusted or supplemented by further cold forming after galvanizing in coordination with the upstream cold forming. The hot strip galvanizing can be carried out with at least one controlled thickness control either before or after galvanizing or without controlled reduction in thickness by controlling the size of the cold forming or the degree of temper rolling.

It is within the scope of the process variations according to the invention, advantageously provide a semi-continuous process flow, in which individual, the galvanizing preceding process steps as the

Strip pretreatment and / or the cold forming are carried out in separate from a galvanizing line, outsourced treatment lines, wherein in the galvanizing line in addition to the application of the zinc layer also cold forming after galvanizing and post-treatment of the strip can be done.

Thus, for example, the descaling process in a separated pickling line or the cold rolling process in a separated cold rolling mill

be carried out before the tape then reaches the galvanizing line with the subsequent subsequent treatments, such as straightening, passivating, etc. A particularly suitable for performing the method suitable for

Fabrication of hot dip coated hot rolled steel strip is characterized in that the hot strip is passed through a belt pre-treatment device to remove the scale, then by cold working the strip thickness is reduced by less than 30%, preferably 0.5 to 10%, and then following passes through the strip galvanizing, in which the band passes through a molten bath.

According to a preferred embodiment of the invention is the

Thickness reducing device designed as a cold rolling mill, which is associated with at least one measuring device in the outlet with feedback of thickness control signals to the cold rolling mill. Further advantageous embodiments of the invention provide that the cold forming to reduce thickness is performed with a cold rolling mill, in which in a turn preferred embodiment, at least one meter is disposed in the outlet of the cold rolling mill and either deviations from a desired thickness as a control signal to the thickness control of the cold rolling mill are returned or which by a regulation to a constant size of

Thickness reduction is regulated. To expand the concept and variation of the operation of the hot galvanizing is proposed according to the invention that the strip galvanizing followed by a cold rolling mill, further thickness reduction device connects, in which the strip thickness is reduced by less than 30%, preferably 0.5 to 10%, wherein at least At least one measuring device in the outlet with feedback of measuring signals for thickness control is assigned to this further cold rolling mill.

According to an optional proposal of the invention, the strip galvanizing device is followed by a further finishing mill designed as a skimming mill with a degree of skimming of less than 3%, preferably 0.5 to 2%

Thickness reduction device on.

According to an advantageous embodiment of the invention come into the

Thickness reduction devices for cold forming for embossing the strip surface structure of the finished product Work rolls are used which have a surface structure with a mean roughness Ra of less than 5 μιτι,

preferably 0.2 to 3 μιτι, have.

According to an embodiment of the invention are to a

Semicontinuous process from a galvanizing line separated, separate process lines for strip pretreatment and / or cold forming provided from which or the pretreated and cold-formed strip is fed to the galvanizing line with integrated strip aftertreatment.

Further features and details of the invention will become apparent from the

Claims and the following description of illustrated in the drawings embodiments of the invention. Show it:

1 is a schematic diagram of a continuous process line for

Hot strip galvanizing with cold deformation before galvanizing; and

2 is a schematic diagram of a semicontinuous process line for

Hot strip galvanizing with cold deformation before galvanizing.

In one example shown in Figure 1, operating in continuous operation hot-dip coating equipment 1 is to be treated, hot-rolled steel strip 2 from a z. B. with not shown straightening units and a tape storage equipped inlet part ET initially a strip pretreatment device 3 is supplied with a tinder breaker 4 or the like and a stain 5 and a sink 6 for removing the scale from the steel strip or band 2. The band pretreatment device 3 is followed by the dashed bordered or highlighted core of the

Hot dip coating plant 1, namely, a strip galvanizing 7 upstream thickness reduction device 8, designed as a cold rolling KWW as a preferred form of cold forming before the steel or hot strip 2 in the Bandverzinkungseinnchtung 7 for applying the coating passes through a molten bath 9.

In the outlet of the cold rolling mill KWW is at least one example

Thickness gauge 10 with feedback of the measured signals to the cold rolling mill arranged for control at deviations measured by a desired thickness.

Optionally, the KWW can also use a measuring method that is not the Thickness, but the size of the cold forming or a skin passage measures and outputs as a control signal. In the case of cold forming in the thickness reduction device 8, the cold forming is carried out with a reduction of the sheet thickness by less than 30%, preferably 0.5 to 10%. During cold forming by

Cold rolling or temper rolling is imparted to the strip a surface structure, to which the work rolls with a surface texture with a mean roughness Ra of less than 10 μιτι, preferably 0.2 to 3 μιτι, are formed.

FIG. 1 further shows that the strip galvanizing device 7 can optionally be followed by a further thickness reduction device 11, in a preferred embodiment also as a cold rolling mill KWW. The work rolls of this further thickness reduction device 1 1 can then be designed so that they μιτι with a mean roughness Ra of less than 10 μιτι, preferably 0.2 to 3, in the cold forming the band, the surface structure of

Imprint finished product. In the case of a mode of operation with a

Thickness reducing 8 before galvanizing and a

Dickenreduziereinrichtung 1 1 after galvanizing, at least with a arranged in the outlet of the further thickness reduction device 1 1 measuring device 12, the deviation of a target strip thickness as a controlled variable of the cold forming of the thickness reduction device 1 1 returned.

The thickness reduction device 1 1 for cold forming in the preferred form of a cold rolling mill (KWW) can perform the process of the skin-forming with less than 3%, preferably 0.5 to 2%, tempering behind the strip galvanizing 7 instead of a controlled thickness control. Furthermore, that can

KWW perform the cold forming with less than 30%, preferably 0.5 to 10%, even with a constant setpoint of the cold forming.

The hot strip 2 cold-formed in this way with a surface structure then passes through a strip aftertreatment device 13, which in the

Plant example a stretch straightener STR and a chemical treatment part ChBT, z. As passivation, may include from which the hot strip 2 as

Finished product in the example with a trimming scissors and a

Tape storage (not shown) equipped outlet part AT passes. The illustrated in Figure 2, working in semi-continuous operation

Hot-dip coating installation 100 differs from the previously described, continuously operating hot-dip coating installation 1 only in that process steps preceding galvanizing are outsourced, in the exemplary embodiment process line I for strip pretreatment and process line II for cold forming, which are separate from process line III for strip galvanizing ,

For the reference numerals entered in FIG. 2 in accordance with FIG. 1, the functions and effects already explained above apply without restriction. Also in Figure 2, the core of the hot dip coating plant, namely the performed before galvanizing cold forming highlighted highlighted by dashed lines. The separation of the process lines entails that each line is associated with an inlet part ET and an outlet part AT, wherein the galvanizing line III next to the strip galvanizing 7 upstream of this band cleaning 14 and integrated the further thickness reduction device 1 1 following strip aftertreatment device 13th includes.

LIST OF REFERENCE NUMBERS

1 ; 100 hot-dip coating plant

2 steel strip / hot strip

3 tape pre-treatment device

4 scale breakers

5 stains

6 sink

7 strip galvanizing device

8 thickness reduction device

9 molten bath

10 gauge / thickness gauge

1 1 thickness reduction device

12 gauge / thickness gauge

13 belt aftertreatment device

14 tape cleaning

Process line strip pretreatment

Process line strip cold forming

Process line strip galvanizing

ET inlet part

AT outlet part

For example, scale breaker

KWW cold rolling mill or stand (as preferred form of cold forming)

STR stretch leveler

ChBT chemical treatment part

Claims

claims:

1 . A process for the hot-dip coating of hot-rolled metal strip, preferably in a continuous belt plant, wherein the hot strip

- subjected to a pretreatment for descaling,

- is galvanized,

- Is reduced by cold working in its thickness and

- undergoes a post-treatment,

characterized in that

the hot strip removed from the scale is cold-formed in a process step preceding the galvanizing with reduction of its strip thickness by less than 30%, preferably 0.5 to 10%.

2. The method according to claim 1,

characterized in that

in cold forming by preferably a cold rolling process, the strip in a cold rolling stand using work rolls with a

Surface structure with a Mittenrauwert Ra of less than 10 μιτι, preferably 0.2 to 3 μιτι, a surface structure is impressed.

3. The method according to claim 1 or 2,

characterized in that

before galvanizing the thickness of the cold-formed strip measured and a deviation from a target thickness is returned as a control variable for the thickness reduction of the cold forming. Method according to claim 1 or 2,

characterized in that

Before galvanization, the size of the cold forming is controlled and regulated to a setpoint.

Method according to one of claims 1 to 4,

characterized in that

before galvanizing with cold forming in a cold rolling mill by temper rolling with surface structuring work rolls with a

Dressing degree of less than 3%, preferably 0.5 to 2%, the required surface roughness is applied.

Process according to claims 1 to 5,

characterized in that

in a subsequent galvanizing subsequent, cold forming on the strip surface in a cold rolling mill by tempering with

Process according to claims 1 to 5,

characterized in that

the strip thickness is reduced by less than 30%, preferably 4 to 10%, in at least after this further cold forming the strip thickness is measured and deviations are fed from a target strip thickness as a controlled variable of the cold forming in a subsequent galvanizing subsequent cold work by cold rolling.

8. The method according to claim 6 or 7,

characterized in that

for Kaltumfornnung in the cold rolling mill after galvanizing work rolls with a Mittenrauwert of less than 10 μιτι, preferably 0.2 to 3 μιτι, used in the cold forming the band

Apply surface structure of the finished product.

9. The method according to any one of claims 1 to 8,

characterized by a semi-continuous process sequence in which individual, the galvanizing preceding process steps such as

Strip pretreatment and / or cold forming in one

Galvanizing line separate, outsourced treatment lines are carried out, wherein in the galvanizing line in addition to the application of the zinc layer and the aftertreatment of the strip takes place.

10. Plant (1; 100) for producing hot-dip coated,

hot-rolled steel strip (2), preferably in a continuous

A process line comprising a descaling belt pretreatment device (3), a strip galvanizer (7), at least one thickness reduction device (8; 1 1) by cold forming, in particular cold rolling, of the belt, and a belt aftertreatment device (13), in particular for feedthrough of the method according to claims 1 to 9,

characterized in that

the strip pretreatment device (3) for the hot strip removed from the scale firstly reduces the thickness reduction device (8) in which the strip thickness is reduced by less than 30%, preferably 0.5 to 10%, and this then following the strip galvanizing device (7) in which the hot strip passes through a molten bath (9).

1 1 .Anlage according to claim 10,

characterized in that

the thickness reduction device (8) is designed as a cold-rolling stand (KWW), to which a measuring device (10) is assigned at least in the outlet of the cold rolling stand (KWW), for returning measurement signals for a thickness control of the cold rolling stand (KWW).

12. Plant according to claim 10,

characterized in that

the thickness reduction device (8) is designed as a cold rolling stand (KWW), which is designed with a regulation to a constant size of the thickness reduction.

13. Plant according to claim 10,

characterized in that

the thickness reduction device (8) is designed as a cold rolling stand (KWW) which, with a degree of skin passage of less than 3%, preferably 0.5 to 2%, imposes a surface structure on the thickness reduction.

14. Plant according to one of claims 10 to 13,

characterized in that

the strip galvanizing device (7) is followed by a further reduction in thickness (11) carried out as a cold rolling mill (KWW), in which the strip thickness is reduced by less than 30%, preferably 0.5 to 10%.

15. Plant according to claim 14,

characterized in that

in this additional cold rolling stand (KWW) in the outlet with feedback of thickness control signals to the cold rolling stand (KWW) at least one

Measuring device (12) is arranged for the return of measurement signals for a thickness control of the cold rolling stand (KWW),

16. Plant according to claim 14 or 15,

characterized in that

This further cold rolling stand (KWW) (1 1) is designed with a control to a constant size of the thickness reduction.

17. Plant according to one of claims 14 to 16,

characterized in that

this further cold rolling stand (KWW) (11) with a degree of skin pass of less than 3%, preferably 0.5 to 2%, imprints a surface structure on the strip in the reduction of thickness.

18. Plant according to one or more of claims 10 to 17,

characterized in that

in the thickness reduction devices (8; 1 1) during cold forming for impressing the strip surface structure of the finished product, work rolls are used which have a surface texture with a mean roughness Ra of less than 10 μm, preferably 0.2 to 3 μm.

19. Plant according to one or more of claims 10 to 18, characterized in that

for a semicontinuous process from a galvanizing line (III) separated, separate process lines (I, II) for strip pretreatment (I) and / or cold working (II) are provided, from which or the pretreated and cold-formed strip to the galvanizing line (III ) with integrated strip aftertreatment (13) is supplied.