CN118663689A - Rolling device and method for cup-like high-strength precise stainless steel strip - Google Patents

Abstract

The present invention provides a rolling device and method for high-strength precision stainless steel strips for cups, and relates to the technical field of steel strip cold rolling devices, comprising: an uncoiler, the uncoiler is used to unwind the steel strip raw material; a pickling tank, the pickling tank is arranged at the rear end of the uncoiler, and the unwinding steel strip raw material is pickled once, a multi-pass cold rolling roller, the multi-pass cold rolling roller is arranged in an emulsified liquid tank, so as to perform a multi-pass cold rolling on the steel strip raw material at the rear end of a pickling process, and a continuous annealing furnace, the continuous annealing furnace is used to anneal the steel strip after the multi-pass cold rolling; the present invention adopts the setting of a pickling tank to complete the two pickling of the steel strip, effectively improves the surface quality of the steel strip, and the multi-pass cold rolling roller is arranged in the pickling tank, and the spray tank can perform synchronous cleaning of the acid solution and the emulsifier residue, which greatly improves the integration and correlation of the device, and further saves energy and reduces emissions.

Description

A rolling device and method for high-strength precision stainless steel strip for cups

Technical Field

The invention relates to the technical field of steel strip cold rolling devices, and in particular to a rolling device and method for a cup-type high-strength precision stainless steel strip.

Background Art

High-strength precision stainless steel for cups generally refers to high-quality stainless steel materials used to make cups and other tableware. This type of stainless steel has the following characteristics:

High Strength: This material has higher tensile strength and hardness than regular stainless steel, making it more durable and impact-resistant.

Precision: Precision stainless steel means that the size and shape of the material are controlled very accurately during the manufacturing process, and can be used to make precision cutlery and containers.

Corrosion resistance: Stainless steel itself has good corrosion resistance, is suitable for long-term contact with moisture and various liquids, and is not easy to rust.

Food safety grade: The stainless steel materials used to make cups and tableware should meet food safety standards and contain no substances harmful to the human body.

In order to obtain the stainless steel material with the above characteristics, the steel strip needs to be cold rolled for multiple times to produce cup-type stainless steel that meets the above conditions.

The prior art discloses a device and method for removing iron oxide scale from hot-rolled steel plates for cold rolling, which is disclosed as "CN102205350A". The device and method relate to metal strip pickling equipment and method. The device is composed of an uncoiler, an inlet shear, a welding machine, an inlet looper, a tension and descaling machine, a pickling tank mechanism, an outlet looper, a trimming machine, an oiling machine, an outlet shear and a coiler. The device is characterized in that the pickling mechanism is composed of a primary pickling mechanism and a secondary pickling mechanism, and an asynchronous controlled rolling device is arranged between the primary pickling mechanism and the secondary pickling mechanism. The iron oxide scale of the steel plate is removed in the steps of uncoiler, descaling, primary pickling, asynchronous rolling, secondary pickling, trimming, oiling and shearing, and coiling into a steel coil. The device has the advantages of novel structure, simple process, safety and reliability, and the iron oxide scale on the surface of the strip is cleanly removed; the surface quality of the cold-rolled plate is significantly improved, the product qualification rate is improved, and the production cost is reduced; the service life of the lubrication circulation device, the lubricating fluid and the cold rolling roller is extended, the consumption is reduced, and the smooth cold rolling production is ensured.

However, the above-mentioned device still has obvious defects during use: the degree of integration of the above-mentioned device is not high, and its secondary pickling process and steel strip rubbing process are carried out in different equipment, which makes the overall equipment occupy a large amount of space, which is not conducive to the efficient use of space, and the correlation between various processes is poor.

Summary of the invention

The object of the present invention is to provide a device and method for rolling high-strength precision stainless steel strips for cups, so as to solve the problems raised in the above-mentioned background technology.

To achieve the above object, the present invention provides the following technical solutions:

A rolling device for high-strength precision stainless steel strip for cups, comprising:

An uncoiler, the uncoiler is used to unwind the steel strip raw material;

A pickling tank, which is arranged at the rear end of the uncoiler and performs pickling on the uncoiled steel strip raw material. The pickling tank includes a pickling tank, an emulsion tank and a spray tank;

Multi-pass cold rolling rollers are arranged in the emulsion tank, so as to perform multi-pass cold rolling on the steel strip material at the rear end of the primary pickling process until the steel strip material is compressed to a preset thickness;

A continuous annealing furnace, which is used to anneal the steel strip after multiple cold rolling; and

A coiler is used to coil the steel strip after cold rolling; wherein,

The cold-rolled steel strip after the continuous annealing furnace is transported to the pickling tank again through the change-direction roller for secondary pickling before reaching the coiler.

An emulsion pumping rod is also installed at the front end of the emulsion tank, and an emulsion pumping groove is also arranged on one side of the emulsion tank. The emulsion tank is communicated with the bottom of the emulsion pumping groove. A pumping piston is arranged in the emulsion pumping groove, and the pumping piston is movably inserted in the pumping cylinder. The pumping cylinder is connected with the emulsion pumping rod through the pumping pipe. The pumping piston performs telescopic movement under the drive of the telescopic driving mechanism and then pumps the emulsion in the emulsion pumping groove to the upper surface of the steel belt through the emulsion pumping rod.

Preferably, a pair of direction-changing rollers are provided in the pickling tank and the spray tank, and the pair of direction-changing rollers are used for supporting and changing the direction of the steel strip during the two pickling processes respectively.

Preferably, a cleaning transition roller is further provided above the emulsifying tank, and the secondary pickled cold-rolled steel strip is supported and redirected by the cleaning transition roller.

Preferably, the multi-pass cold rolling rollers include multiple pairs of cold rolling rollers, the multiple pairs of cold rolling rollers are arranged with decreasing spacing therebetween, and the number of the multiple pairs of cold rolling rollers M is ≥3.

Preferably, a plurality of pairs of spray heads are provided in the spray tank and the emulsion tank.

Preferably, a scraping tank is further provided between the pickling tank and the emulsifying tank.

Preferably, a scraping plate is provided above the spraying groove and the scraping groove, and the scraping plate is used to scrape off the liquid on the surface of the steel plate.

Preferably, the telescopic driving mechanism that drives the pumping piston to perform telescopic movement is a driven turntable, an eccentric rod is installed on one side of the driven turntable, and the pumping piston is inserted on the eccentric rod through a through hole at one end away from the pumping cylinder. The pumping piston cooperates with a gear groove opened on one of the multiple cold rolling rollers, and the pumping piston is driven to perform telescopic movement through the rotation of the cold rolling roller.

A method for rolling a cup-shaped high-strength precision stainless steel strip, the rolling method adopts the above-mentioned cup-shaped high-strength precision stainless steel strip rolling device, and comprises the following steps:

Step 1: Use the overhead crane to hoist the cold-rolled steel strip raw material onto the uncoiler, pull out one end of the steel strip through the rotation of the uncoiler and place it on the conveyor roller at the rear, and set the unwinding speed to 180-200m/min;

Step 2: The unwinding cold-rolled steel strip raw material enters the pickling tank for pickling. The pickling tank uses a mixed acid solution of nitric acid and HF acid. The concentration of nitric acid is 60-120g/L, and the concentration of HF acid is 5g/L to 12g/L. The pickling temperature is controlled at 40-55°C. The steel strip raw material after pickling enters the emulsification tank;

Step 3: When the steel strip raw material enters the emulsion tank, the steel strip raw material is subjected to multiple cold rolling by the multiple cold rolling rollers arranged in the emulsion tank. The emulsion tank is filled with emulsion, the concentration of the emulsion is 2.5%, and the liquid level of the emulsion is lower than the horizontal plane of the cold-rolled steel strip. During the cold rolling process of the multiple cold rolling rollers, the multiple cold rolling rollers are partially immersed in the emulsion to complete the application of the emulsifier, and are applied to the steel strip by contacting with the steel strip. The multiple cold rolling rollers are cold rolled by a 950mm single-frame six-roller reversible cold rolling mill, and the pickled steel strip with a thickness of 3-4mm is rolled into a finished product with a thickness of 0.36-0.42mm. The working roll body hardness of the 950mm single-frame six-roller reversible cold rolling mill is 90HSD, the roll diameter difference is 0.08mm, and the total deformation rate is controlled at 85%;

Step 4: The cold-rolled steel strip enters the spray tank to rinse the pickling residual liquid and emulsifier residue on the surface, and then enters the continuous annealing furnace for annealing. The annealing temperature is controlled at 750-810℃. The annealed cold-rolled steel passes through the changing roller and enters the pickling tank again for secondary pickling;

Step 5: After pickling, the cold-rolled steel strip is coiled by a coiler.

Compared with the prior art, the present invention has the following beneficial effects:

The present invention adopts a pickling tank to complete the double pickling of the steel strip. The two pickling steps at the front end of cold rolling and the back end of annealing effectively improve the surface quality of the steel strip. The multi-pass cold rolling rollers are arranged in the pickling tank, so that the pickling and cold rolling processes can be carried out simultaneously. The spray tank can simultaneously clean the acid solution and emulsifier residues, which greatly improves the integration and correlation of the device and further saves energy and reduces emissions.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of the overall structure of the present invention;

Fig. 2 is a schematic diagram of the structure of a pickling tank of the present invention;

FIG3 is a perspective schematic diagram of the cross-sectional structure of the pickling tank of the present invention;

FIG. 4 is a schematic diagram of the pumping piston and its connection structure of the present invention.

In the figure: 1 unwinder, 2 pickling tank, 3 pickling tank, 4 emulsion tank, 5 spray tank, 6 multi-pass cold rolling roller, 7 continuous annealing furnace, 8 winder, 9 change roller, 10 cleaning transition roller, 11 cold rolling roller, 12 spray head, 13 scraper plate, 14 emulsion pumping rod, 15 emulsion pumping tank, 16 pumping piston, 17 pumping cylinder, 18 pumping pipe, 19 scraper tank, 20 driven turntable, 21 gear slot.

DETAILED DESCRIPTION

The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

Please refer to Figures 1-4, the present invention provides a technical solution:

Embodiment 1:

A rolling device for high-strength precision stainless steel strip for cups, comprising:

An uncoiler 1, wherein the uncoiler 1 is used to unwind the steel strip raw material;

A pickling tank 2, which is arranged at the rear end of the uncoiler 1 and performs pickling on the unwinding steel strip raw material. The pickling tank 2 includes a pickling tank 3, an emulsion tank 4 and a spray tank 5;

A multi-pass cold rolling roller 6 is arranged in the emulsified liquid tank 4, so as to perform multi-pass cold rolling on the steel strip material at the rear end of the primary pickling process until the steel strip material is compressed to a preset thickness;

a continuous annealing furnace 7, wherein the continuous annealing furnace 7 is used to anneal the steel strip after multiple cold rolling passes; and

The coiler 8 is used to coil the steel strip after cold rolling; wherein,

The cold-rolled steel strip after the continuous annealing furnace 7 is transported to the pickling tank 2 again through the change-direction roller 9 for secondary pickling before reaching the coiler 8.

An emulsion pumping rod 14 is also installed at the front end of the emulsion tank 4, and an emulsion pumping tank 15 is also arranged on one side of the emulsion tank 4. The emulsion tank 4 is communicated with the bottom of the emulsion pumping tank 15. A pumping piston 16 is arranged in the emulsion pumping tank 15. The pumping piston 16 is movably inserted in the pumping cylinder 17. The pumping cylinder 17 is connected with the emulsion pumping rod 14 through the pumping pipe 18. The pumping piston 16 performs telescopic movement under the drive of the telescopic drive mechanism and then pumps the emulsion in the emulsion pumping tank 15 to the upper surface of the steel belt through the emulsion pumping rod 14.

A pair of direction-changing rollers 9 are provided in the pickling tank 3 and the spray tank 5. The pair of direction-changing rollers 9 are used for supporting and changing the direction of the steel strip during the two pickling processes.

A cleaning transition roller 10 is also arranged above the emulsified liquid tank 4 , and the secondary pickled cold-rolled steel strip is supported and redirected by the cleaning transition roller 10 .

In this embodiment, the uncoiler 1 is used to unwind the steel strip raw material. Before the steel strip raw material is cold-rolled, the steel strip first enters the pickling tank 2 for pickling. The pickling process is set to clean the residue on the surface of the steel strip so that the subsequent cold rolling process can obtain a cold-rolled steel strip with a smoother surface. In this embodiment, no new multi-pass steel strip line is set, but it is integrated into the pickling tank 2. After the pickling is completed, the cold rolling operation is immediately carried out. The advantage of this arrangement is that the surface flatness of the steel strip is higher after the cold rolling is completed. In theory, the longer the running length of the steel strip, the greater the probability that particles in the air fall onto the surface of the steel strip. Therefore, after the pickling is completed, The subsequent multi-pass rolling process of the steel strip can minimize the probability of particles falling into the steel strip, thereby ensuring the quality of cold rolling. Referring to Figure 1 of the specification, in the emulsion tank 4, the liquid level of the multi-pass cold rolling roller 6 is located below the axis of the cold rolling roller 11 arranged below. The cold rolling roller 11 is coated with an emulsifier during the rotation process, and is coated on the surface of the steel strip as it contacts the steel strip, thereby completing the lubrication and heat dissipation of the cold rolling process. At the same time, the steel strip located above is lubricated by the emulsion pumped by the emulsion pump rod 14, wherein the emulsifier pumped out by the emulsion pump rod 14 comes from the emulsion pumping tank 15 connected to the emulsion tank 4, and is pumped through the internal The telescopic movement of the pumping piston 16 performs the pumping operation of the emulsion. During the pumping process of the emulsion, multiple cold rolling is performed simultaneously. After multiple cold rolling, the tensile strength of the steel strip can reach 690Mpa and the yield strength is 290Mpa. The cold rolling process effectively improves the strength of the steel strip. Our company uses the cold-rolled steel for the production of stainless steel liner, which can ensure the strength and sealing of the cup. After the cold rolling is completed, the steel strip enters the spray tank 5, and the emulsifier and acid residue on the surface of the steel strip can be removed at the same time by spraying clean water. One process completes the operation of multiple distributed processes in the prior art, which greatly improves the device. Integration: The steel strip needs to be annealed after cold rolling. Since oxide scale may be formed on the surface of the steel strip during the annealing process, it needs to be pickled again in the pickling tank 2. In this embodiment, the annealed steel strip is transported to the front pickling tank 2 for secondary pickling, which further improves the integration of the device and can effectively reduce the footprint of the equipment. The spray tank 5 supplies cleaning water to the spray head 12 through an external water pump. A drain outlet for water outflow is provided at the bottom of the spray tank 5. The circulation of the spray water can be achieved by further installing a water filtering and cleaning device, thereby further improving the utilization rate of resources.

Embodiment 2:

In this embodiment, the multi-pass cold rolling rollers 6 include multiple pairs of cold rolling rollers 11, and the multiple pairs of cold rolling rollers 11 are arranged with decreasing spacing therebetween. The number M of the multiple pairs of cold rolling rollers 11 is ≥ 3. Furthermore, the cold rolling rollers 11 are specifically arranged according to the needs of cold rolling, so that the pressing rate of the cold rolling process is controlled within a reasonable range, thereby reducing damage to the steel strip and the cold rolling rollers 11 and ensuring continuous operation of the device.

Embodiment three:

A scraping tank 19 is also provided between the pickling tank 3 and the emulsion tank 4;

A scraping plate 13 is disposed above the spraying tank 5 and the scraping tank 19 , and the scraping plate 13 is used to scrape off the liquid on the surface of the steel plate.

In this embodiment, the scraper plate 13 is arranged to quickly clean the surface of the steel plate during the two cleaning processes. The flexible scraper is pressed tightly against the surface of the steel plate by a spring, and the residual liquid on the surface is quickly scraped off as the steel plate moves. The rear end of the secondary pickling can also be equipped with a drying box to further ensure the dryness of the steel strip surface before winding. The scraper groove 19 is arranged to enable the scraper plate 13 to scrape off the acidic solution remaining on the surface of the steel strip after the first pickling, thereby preventing the acidic liquid residue of the first pickling from adhering to the surface of the multi-pass cold rolling roller 6, thereby causing surface corrosion of the cold rolling roller 11, thereby effectively protecting the device.

A method for rolling a cup-shaped high-strength precision stainless steel strip, the rolling method adopts the above-mentioned cup-shaped high-strength precision stainless steel strip rolling device, and comprises the following steps:

Step 1: The cold-rolled steel strip raw material is hoisted on the uncoiler 1 by means of a crane, one end of the steel strip is pulled out by the rotation of the uncoiler 1 and is placed on the conveying roller at the rear, and the unwinding speed is set to 180-200 m/min;

Step 2: The unwinding cold-rolled steel strip raw material enters the pickling tank 2 for pickling. The pickling tank 3 uses a mixed acid solution of nitric acid and HF acid. The concentration of nitric acid is 60-120g/L, and the concentration of HF acid is 5g/L to 12g/L. The pickling temperature is controlled at 40-55°C. The steel strip raw material after pickling enters the emulsification tank 4;

Step 3: When the steel strip raw material enters the emulsion tank 4, the steel strip raw material is subjected to multiple cold rolling by the multiple cold rolling rollers 6 arranged in the emulsion tank 4. The emulsion is filled in the emulsion tank 4, and the concentration of the emulsion is 2.5%. The liquid level of the emulsion is lower than the horizontal plane of the cold-rolled steel strip. During the cold rolling process of the multiple cold rolling rollers 6, the multiple cold rolling rollers 6 are partially immersed in the emulsion to complete the application of the emulsifier, and are applied to the steel strip by contacting with the steel strip. The multiple cold rolling rollers are cold rolled by a 950mm single-frame six-roller reversible cold rolling mill, and the pickled steel strip with a thickness of 3-4mm is rolled into a finished product with a thickness of 0.36-0.42mm. The working roll body hardness of the 950mm single-frame six-roller reversible cold rolling mill is 90HSD, the roll diameter difference is 0.08mm, and the total deformation rate is controlled at 85%;

Step 4: The cold-rolled steel strip enters the spray tank 5 to rinse the pickling residual liquid and emulsifier residue on the surface, and then enters the continuous annealing furnace 7 for annealing. The annealing temperature is controlled at 750-810°C. The annealed cold-rolled steel passes through the change-direction roller and enters the pickling tank 2 again for secondary pickling;

Step 5: After pickling, the cold-rolled steel strip is coiled by the coiler 8 .

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims (9)

1. A rolling device for high-strength precision stainless steel strip for cups, characterized by comprising: An uncoiler (1), the uncoiler (1) being used to unwind a steel strip raw material; A pickling tank (2), the pickling tank (2) being arranged at the rear end of the uncoiler (1) and performing pickling on the uncoiled steel strip raw material, the pickling tank (2) comprising a pickling tank (3), an emulsion tank (4) and a spray tank (5); A multi-pass cold rolling roller (6), wherein the multi-pass cold rolling roller (6) is arranged in the emulsion tank (4), so as to perform multi-pass cold rolling on the steel strip material at the rear end of the primary pickling process until the steel strip material is compressed to a preset thickness; a continuous annealing furnace (7), wherein the continuous annealing furnace (7) is used to anneal a steel strip after multiple cold rolling passes; and A coiler (8), the coiler (8) is used to coil the steel strip after cold rolling; wherein: The cold-rolled steel strip that has passed through the continuous annealing furnace (7) is transported again to the pickling tank (2) through a change-of-direction roller (9) for secondary pickling before reaching the coiler (8); An emulsion pumping rod (14) is also installed at the front end of the emulsion tank (4), and an emulsion pumping tank (15) is also arranged on one side of the emulsion tank (4). The emulsion tank (4) is communicated with the bottom of the emulsion pumping tank (15). A pumping piston (16) is arranged in the emulsion pumping tank (15). The pumping piston (16) is movably inserted in a pumping cylinder (17). The pumping cylinder (17) is communicated with the emulsion pumping rod (14) through a pumping pipe (18). The pumping piston (16) performs telescopic movement under the drive of the telescopic drive mechanism, thereby pumping the emulsion in the emulsion pumping tank (15) through the emulsion pumping rod (14) onto the upper surface of the steel belt. 2. A rolling device for high-strength precision stainless steel strip for cups according to claim 1, characterized in that a pair of direction-changing rollers (9) are provided in the pickling tank (3) and the spray tank (5), and the pair of direction-changing rollers (9) are used for supporting and changing the direction of the steel strip during the two pickling processes respectively. 3. A rolling device for high-strength precision stainless steel strip for cups according to claim 1 or 2, characterized in that a cleaning transition roller (10) is also arranged above the emulsion tank (4), and the secondary pickled cold-rolled steel strip is supported and redirected by the cleaning transition roller (10). 4. A rolling device for high-strength precision stainless steel strip for cups according to claim 3, characterized in that: the multi-pass cold rolling roller (6) includes multiple pairs of cold rolling rollers (11), the multiple pairs of cold rolling rollers (11) are arranged with spacing decreasing in sequence, and the number M of the multiple pairs of cold rolling rollers (11) is ≥3. 5. The rolling device for high-strength precision stainless steel strip for cups according to claim 4, characterized in that a plurality of pairs of spray heads (12) are arranged in the spray tank (5). 6. The rolling device for high-strength precision stainless steel strip for cups according to claim 5, characterized in that a scraping groove (19) is further provided between the pickling tank (3) and the emulsifying tank (4). 7. A rolling device for high-strength precision stainless steel strip for cups according to claim 6, characterized in that a scraping plate (13) is provided above the spraying tank (5) and the scraping tank (19), and the scraping plate (13) is used to scrape off the liquid on the surface of the steel plate. 8. A rolling device for high-strength precision stainless steel strip for cups according to claim 7, characterized in that the telescopic driving mechanism for driving the pumping piston (16) to perform telescopic movement is a driven turntable (20), an eccentric rod is installed on one side of the driven turntable (20), and the end of the pumping piston (16) away from the pumping cylinder (17) is inserted on the eccentric rod through an opened through hole, and the pumping piston (16) cooperates with a gear groove (21) opened on one of the cold rolling rollers (11) in the multi-pass cold rolling rollers (6), and the pumping piston (16) is driven to perform telescopic movement through the rotation of the cold rolling roller (11). 9. A method for rolling a cup-like high-strength precision stainless steel strip, the rolling method using the rolling device for cup-like high-strength precision stainless steel strip according to any one of claims 1 to 8, characterized in that the method comprises the following steps: Step 1: hoisting the cold-rolled steel strip raw material onto the uncoiler (1) by means of a crane, pulling out one end of the steel strip by the rotation of the uncoiler (1) and placing it on a conveying roller at the rear, and setting the unwinding speed to 180-200 m/min; Step 2: the unwinding cold-rolled steel strip enters the pickling tank (2) for pickling. The pickling tank (3) uses a mixed acid solution of nitric acid and HF acid. The concentration of nitric acid is 60-120 g/L, and the concentration of HF acid is 5 g/L to 12 g/L. The pickling temperature is controlled at 40-55° C. After pickling, the steel strip enters the emulsification tank (4); Step 3: When the steel strip raw material enters the emulsion tank (4), the steel strip raw material is subjected to multiple cold rolling by the multiple cold rolling rollers (6) arranged in the emulsion tank (4). The emulsion tank (4) is filled with emulsion, the concentration of the emulsion is 2.5%, and the liquid level of the emulsion is lower than the horizontal surface of the cold-rolled steel strip. During the cold rolling process of the multiple cold rolling rollers (6), the multiple cold rolling rollers (6) are partially immersed in the emulsion to complete the coating of the emulsifier, and the emulsifier is coated on the steel strip by contacting with the steel strip. The multiple cold rolling rollers are cold rolled by a 950mm single-frame six-roller reversible cold rolling mill, and the pickled steel strip with a thickness of 3-4mm is rolled into a finished product with a thickness of 0.36-0.42mm. The working roll body hardness of the 950mm single-frame six-roller reversible cold rolling mill is 90HSD, the roll diameter difference is 0.08mm, and the total deformation rate is controlled at 85%; Step 4: After cold rolling, the steel strip enters the spray tank (5) to wash away the pickling residual liquid and emulsifier residue on the surface, and then enters the continuous annealing furnace (7) for annealing. The annealing temperature is controlled at 750-810°C. The annealed cold-rolled steel passes through the change-direction roller and enters the pickling tank (2) again for secondary pickling. Step 5: After pickling, the cold-rolled steel strip is coiled by a coiler (8).