TWI625172B - Composite cold rolling line - Google Patents

Abstract

A composite cold rolling line comprising a feeding unit, a first rolling unit connected downstream of the feeding unit, an annealing descaling unit downstream of the first rolling unit, and a continuous connection a pickling unit downstream of the annealing and descaling unit, a second rolling unit downstream of the pickling unit, and a return unit downstream of the second rolling unit. The first cold rolling mill can perform preliminary rolling before performing the annealing and pickling process, which not only can reduce the thickness of the rolling required for the second rolling, but also can continuously produce a large amount of high output rate. Cold-rolled thin hard-rolled steel coils, and the black-rolled steel coils after preliminary rolling can reduce the amount of scale by 30-70%, thereby reducing the number and length of rust-removing equipment, in addition to reducing equipment costs, and reducing Sandblasting, acid use and emissions, to achieve environmental protection and energy saving.

Description

Composite cold rolling line

The invention relates to a composite cold-rolled line, in particular to a composite cold-rolled cold-rolled thin hard steel coil used to continuously and massively input black skin steel coils into a minimum thickness of 0.25 ㎜. line.

Referring to Figure 1, the traditional stainless steel cold rolling process is to feed the black-coated steel coil F1, hot-rolled annealed pickling line A, and then annealed, sandblasted, and pickled to make NO.1 steel coil F2, and then No.1 steel coil F2 is rolled in a reciprocating multi-pass rolling process on a twentieth-high cold rolling mill of cold rolling line B until the NO.1 steel coil F2 is rolled to the target thickness. Volume F3. Cold rolled thin hard steel coil F3 can be produced by 2D steel coil F4, 2B steel coil F5, F6 after other processes such as cold rolling annealing pickling line C, quenched and tempered rolling line D and tension leveling line E ... ... and other high-value cold-rolled stainless steel products.

The aforementioned cold rolling process is sent to the hot-rolled annealing and pickling line A at the black skin steel coil F1. After the annealing process, the surface oxide scale will be thickened, and subsequent mechanical rust removal processes such as sandblasting and pickling shall be strengthened. The chemical derusting process is used to remove the scale on the surface of the steel coil. Therefore, it is necessary to set up a sand blasting machine and increase the speed of blasting, increase the length of the pickling tank and increase the acid concentration, which leads to equipment costs, blasting and acid consumption and subsequent waste Increased material handling costs. And because there is no significant difference in the thickness and size of the incoming black skin steel coil F1 and the outgoing NO.1 steel coil F2, there is no difference in reducing the rolling reduction of subsequent cold rolling mills and improving the cold rolling mechanism process efficiency. help.

In the cold rolling line B process of NO.1 steel coil F2 subsequently entered, a single 20-roller cold rolling mill is used for reciprocating rolling, and the number of rolling passes required will lead to the output per unit time. The reciprocating cold rolling mill can not provide a large amount of cold rolling because of the large reduction rate required for the production of thin steel sheets, high strip breakage probability, many rolling passes, and long rolling time. Thin hard plate steel coil F3. In addition, this type of reciprocating rolling mill needs to establish tension by coiling, so the head and tail sections of the steel coil will each have a length of about 6 ~ 8m for coiling, and the un-rolled off-gauge needs to be cut off, resulting in material loss in the cutting section. In order to reduce the output rate, even if this problem occurs before the pre-processed coil preparation line welding guide belt, an off-gaue with a length of 3m will still occur, and the on-line cost and conduction belt cost of the derivative coil preparation line increase.

In addition, because the traditional hot-rolled annealing and pickling line A and cold rolling mill are independent production lines, the black skin incoming steel coil F1 is unrolled, rolled, hot rolled, annealed, and pickled. .1 steel coil F2, while NO.1 steel coil F2 needs to be unrolled and rolled after rolling in order to obtain cold rolled thin hard steel coil F3, so the hot rolling annealing line is wasted. The time for coil and cold rolling mill to go on-line and unwind, resulting in a reduction in production efficiency.

Therefore, the object of the present invention is to provide a composite cold-rolled line with low production cost, high product yield, and continuous production to provide a large number of cold-rolled thin hard steel coils with a thickness of up to 0.25 ㎜.

Therefore, the composite cold-rolling line of the present invention is used to continuously make the input black skin steel coil into a cold-rolled thin hard plate steel coil, and the composite cold-rolling line includes an unrolling of the black skin steel coil into A steel strip feeding unit, a first rolling unit, an annealing and rust removing unit connected downstream of the first rolling unit and annealing and mechanically removing the steel strip, and one connected to the A pickling unit downstream of the annealing and descaling unit and pickling the steel strip, a picking unit that can immediately return the material when abnormal quality of the steel strip is detected after the pickling unit, a second rolling A rolling unit, and a withdrawal unit downstream of the second rolling unit.

The first rolling unit includes two or three first cold rolling mills disposed adjacent to each other and continuing downstream of the feeding unit. The second rolling unit includes five second cold rolling mills arranged adjacent to each other and continuing downstream of the pickling unit.

The effect of the present invention is that the first cold rolling mill can perform preliminary rolling before the annealing and pickling process, not only can reduce the thickness of the rolling required for the second rolling, so as to reduce the strip breaking rate, Therefore, it is possible to continuously produce large-volume cold-rolled thin hard steel coils with high output rates, and because the initially rolled black-skinned steel coils can reduce the amount of rust scale by 30 ~ 70%, it can reduce the number of rust removal equipment. And length, in addition to reducing equipment costs, it can also reduce the use and discharge of sandblasting and acid solution, and achieve environmental protection efficiency of energy saving and waste reduction.

Referring to FIG. 2, an embodiment of the composite cold-rolled line 1 of the present invention is used to continuously mass-produce input black coils into cold-rolled cold-rolled coils. The composite cold rolling line 1 includes a feeding unit 2, a first rolling unit 3, an annealing and descaling unit 4, an acid cleaning unit 5, a withdrawal unit 6, and a first Two rolling units 7, a return unit 8, and an accumulating unit 9 which is arranged between the aforementioned units and is connected according to the speed of production. The feeding unit 2 includes a feeding area 21 and a first welding machine 22 downstream from the feeding area 21. In this embodiment, the feeding area 21 has two unwinding stations 211, and each unwinding station 211 is equipped with a steel coil storage device, a steel coil trolley, an overhanging mandrel unwinder, and a steel coil unwinding, Leveling and shearing equipment. The first welding machine 22 is a laser full-automatic welding machine of MEL Laser Welder model manufactured by Guild International. The first welding machine 22 uses an optical fiber laser system, so only one optical fiber cable needs to be connected between the laser power source and the laser welding head without other consumables. Its welding advantage is that the welding bead is flat and the strength is uniform. Direct rolling without opening the work rolls, so there is almost no off-gauge material loss in the produced steel coil.

The first rolling unit 3 includes two first cold rolling mills 31 arranged adjacent to each other and downstream of the first welding machine 22 of the feeding unit 2. The first cold rolling mill 31 is a tandem cold rolling mill, the model is T-Sendzimir Z-type inserts ZR 613A-52, the maximum production rate at the inlet is 200mpm, the average production rate at the inlet is 63mpm, and the maximum output rate at the outlet is 200mpm The average output speed of the export is 125mpm, and the maximum total reduction rate of the two first cold rolling mills 31 is set to 50%. The black skin coil can be reduced after rolling according to different steel types or reduction rates. The scale of 30 to 70% can help the downstream annealing and descaling unit 4 and pickling unit 5 to reduce the number and length of descaling equipment, reduce the pickling concentration and shorten the pickling time. Each first cold rolling mill 31 includes a quick roll changing device to ensure that welding and work roll replacement will not cause production line interruption. The first cold rolling mill 31 uses water-soluble rolling oil and has the characteristics of good cooling effect and low oil cost. In addition, in order to cope with the large and large scale of the steel belt, the filter system is a filter cloth filter system, which can not only maintain the cleanliness of the rolled oil, but also cost less than the core filter system. It should be noted that the number of the first cold rolling mills 31 is two in this embodiment, but in other variations of this embodiment, the number of the first cold rolling mills 31 may also be three .

The annealing and descaling unit 4 includes an oven region 41, a rust crusher 42, a sandblasting region 43, and an abrasive brush roller 44 sequentially from upstream to downstream in order from the downstream of the first cold rolling mill 31. The furnace area 41 is a horizontal chain type structure, and has two radiant preheating sections, four gas heating sections, and five cooling sections. The main control computer of the furnace area 41 has an APN code setting, which can automatically adjust to the required annealing parameter condition (Heating Pattern) corresponding to different steel types and thicknesses to avoid the risk of personnel operation errors. The blasting area 43 includes four blasting machines. The grinding brush roller 44 uses two sets of steel hair brush rollers and back rollers. The brush rollers contact the surface of the steel strip, in addition to removing the rust on the upper and lower surfaces, and reducing the roughness of the plate surface, which can effectively improve the NO.1 steel. Fineness of the surface of the roll.

The pickling unit 5 includes a first pickling zone 51, a second pickling zone 52, and a first detector 53 in sequence from upstream to downstream in sequence. The first pickling zone 51 has two sulfuric acid tanks, and the second pickling zone 52 has four mixed acid tanks using nitric acid and hydrofluoric acid, and a five-stage water washing section. The water washing section has two sections of water spray cleaning, two sections of brush washing machine cleaning and one section of hot air drying. The first detector 53 is an automatic detection system, which can immediately determine whether there are defects in the strip that are not conducive to rolling, and choose whether to perform the withdrawal in advance of the withdrawal unit 6 to avoid poor product quality and subsequent second Risk of broken belt in rolling unit 7.

The unloading unit 6 includes a unloading zone 61 downstream from the first detector 53 and a second welding machine 62 downstream from the unloading zone 61. The unwinding area 61 includes a winding mandrel, a tension roller, a shearing machine, a turning roller, an interleaving paper device, a sleeve loading device, a steel coil unloading vehicle, and a steel coil binding, weighing, and storage device. The models and functions of the second welding machine 62 and the first welding machine 22 are the same.

The second rolling unit 7 includes five second cold rolling mills 71 downstream of the second welding machine 62 of the unwinding unit 6. The type and equipment of the second cold rolling mill 71 are the same as those of the first cold rolling mill 31 to facilitate the sharing of parts and reduce the amount of spare parts. The difference is that the five second cold rolling mills 71 add up The maximum total reduction rate is 75%, and the maximum production rate at the entrance is 200mpm, the average production rate at the inlet is 125mpm, the maximum output rate at the exit is 600mpm, and the average output rate at the exit is 500mpm. The second cold rolling mill 71 is designed with a system that can switch between water-soluble and mineral rolling oils. General products are produced by water-soluble rolling oils, especially steel grades without high gloss requirements (such as Pan 400 series, 200 System) to reduce production costs; high-quality demand products are converted to mineral rolling oil for production. The rolling oil filtration system adopts different filtering methods according to the type of rolling oil and product quality requirements. Water-soluble rolling oil recovery filter cloth filtration system; mineral rolling oil recovery filter core filtration system. And the mill is equipped with AGC (Automatic Thickness Feedback Control) and AFC (Automatic Profile Detection Feedback Control) systems, which can provide steel coil products with accurate thickness and good shape.

The unloading unit 8 includes an alkali washing zone 81, a second detector 82, and a discharge zone 83, which are sequentially connected to the second cold rolling mill 71 from upstream to downstream. The alkaline washing zone 81 has sections such as spray alkali washing, brush washing, hot water washing, and finally hot air drying. The second detector 82 is an automatic detection system of the same type as the first detector 53. The unwinding area 83 has two winding stations 831, each of which is the same as the unwinding area 61 and has a winding mandrel, a tension roller, a shearing machine, a turning roller, an interleaving paper device, Sleeve loading, coil unloading truck, and coil bundling, weighing and storage equipment.

The accumulating unit 9 includes a first welding machine 22 connected to the feeding unit 2 and a first accumulating area 91 between the first rolling unit 3, and a continuous unit connected to the first rolling unit. 3 and the second accumulation zone 92 between the annealing and descaling unit 4; a third accumulation zone 93 connected between the pickling unit 5 and the withdrawal zone 61 of the withdrawal unit 6; A fourth welding area 94 between the second welding machine 62 of the discharging unit 6 and the second rolling unit 7, an alkali washing area 81 subsequent to the discharging unit 8, and the second A fifth accumulation area 95 between the detectors 82.

Referring to FIG. 2 and FIG. 3, the manufacturing process of the composite cold rolling line 1 is as follows: the input black skin steel coil is set in the steel coil storage equipment of the feeding area 21, and the black skin steel coil is hot rolled Produced stainless steel coil without annealing and pickling. After unrolling the black steel coil into a plate-shaped steel strip, one unwinding station 211 conveys the steel strip along the downstream of the production line. When the black steel coil is used up, the other unwinds The rolling station 211 will then unroll another black steel coil into a steel strip and convey it, and the head and tail of the two steel strips will be connected by the first welding machine 22. Then, the steel strips are sequentially rolled through the two first cold rolling mills 31 at a maximum rolling reduction rate of 50%, thereby reducing the thickness of the steel strips, and rolling can reduce the thickness of the steel strips. The surface scale is cracked, and the amount of scale can be reduced by 30 ~ 70% according to different steel types and rolling reduction rates. In addition, the bead formed on the two steel strips by the first welding machine 22 has high flatness and uniform strength. Therefore, when the bead passes through the first cold rolling mill 31, it is not necessary to open the work rolls. Rolling directly can improve the production efficiency of the production line and avoid the occurrence of rolling breaks.

The steel strip after the first rolling and rolling will be sent to the furnace area 41, and the radiant heating is performed by the heat extracted by the gas heating section in the preheating radiation section, and the gas heating The section heats the steel strip to an annealing temperature of approximately 1200 degrees Celsius. The first four cooling sections use air as a cooling medium to reduce the temperature to about 150 degrees Celsius, and the fifth cooling section uses water cooling to reduce the steel strip to a maximum temperature of 70 degrees Celsius, Finally, it passes through a hot air drying section to remove moisture from the surface of the steel strip. The rust crusher 42 uses rollers to bend the steel strip, forcing the rust scale on the surface of the steel strip to crack and peel, and can improve the shape of the steel strip. Each sand blasting machine of the sand blasting area 43 is provided with two sand blasting wheels on the upper and lower sides of the steel belt, respectively. The rust on the surface of the steel belt is broken and crushed by sand blasting to remove the outer surface of the steel belt. Most of the rust. The grinding brush roller 44 uses two sets of steel hair brush rollers to remove rust on the upper and lower surfaces of the steel strip, and can reduce the surface roughness of the steel strip, thereby improving the surface fineness. Because the steel strip passes the preliminary rolling of the first cold rolling mill 31 to reduce the amount of scale, the number of annealing and descaling units 4 and the length of the production line can be reduced.

After the steel strip is sent to the pickling unit 5, it is sequentially pickled through the first pickling zone 51 and the second pickling zone 52, and finally passes through the five-stage water washing of the second pickling zone 52. Section to ensure that the surface of the steel strip is completely free of acid residue. The finished product of the steel strip after pickling is NO.1 steel strip, but for the sake of convenience, it is still collectively referred to as steel strip. It should be particularly noted that, because the steel strip is initially rolled by the first cold rolling mill 31 to reduce the amount of scale, the pickling concentration can be reduced and the time of the pickling operation can be reduced. 42 forces the scale of the steel strip to crack and peel, so sulfuric acid easily erodes the base material of the steel strip from the cracked area of the scale during pickling, thereby increasing the efficiency of pickling and rust removal. After the pickled steel strip is judged by the first tester 53 whether there is a defect that is not conducive to subsequent rolling, if there is a defect, the section of steel strip is guided to the discharge area 61 and rolled into steel. Roll, and cut off the defective section with a shearing machine, and then weld and join the two steel strips before and after the defective section with the second welding machine 62, and continue the subsequent operations.

The steel strips passing through the unloading area 61 will sequentially pass through the five second cold rolling mills 71 to perform a rolling operation with a maximum total reduction rate of 75%, thereby rolling the steel strips to a target thickness. Obtain the required cold rolled thin hard steel coil. The second cold rolling mill 71 is provided with an automatic thickness feedback control (AGC) system and an automatic shape detection feedback control (AFC) system to facilitate the rolling of the steel strip into a cold-rolled steel with accurate thickness and good shape. Thin hard board. Finally, the cold-rolled thin hard board passes through the alkaline washing zone 81 to remove the surface water-soluble or mineral rolling oil, and is sent to the discharge zone after the second detector 82 confirms the output quality. 83 coils were rolled into cold rolled thin hard steel coils. In addition, when the production line needs to be temporarily stopped, the steel strip may be temporarily stored in the first, second, third, fourth, and fifth accumulation areas 91, 92, 93, 94, and 95.

The following table 1 is the actual capacity estimation table of this example. From Table 1, it can be seen that the rolled products in this case can indeed reach the target thickness and less than 1㎜, and the minimum thickness can reach 0.25㎜.

Table I         <TABLE border = "1" borderColor = "# 000000" width = "85%"> <TBODY> <tr> <td> initial thickness </ td> <td> width (㎜) </ td> <td> average Rolling speed (mpm) </ td> <td> Density </ td> <td> Production (ton / hour) </ td> <td> Monthly output (10,000 tons) </ td> <td> Annual output (ten thousand Ton) </ td> <td> First rolling thickness (㎜) </ td> <td> Finished rolling thickness (㎜) </ td> <td> First rolling reduction (%) </ td> <td> Second rolling reduction (%) </ td> </ tr> <tr> <td> 2.0 </ td> <td> 1250 </ td> <td> 500 </ td> <td> 7.9 </ td > <td> 74.1 </ td> <td> 4.5 </ td> <td> 53.8 </ td> <td> 1.00 </ td> <td> 0.25 </ td> <td> 50.0 </ td> < td> 75.0 </ td> </ tr> <tr> <td> 2.0 </ td> <td> 1250 </ td> <td> 500 </ td> <td> 7.9 </ td> <td> 88.9 </ td> <td> 5.4 </ td> <td> 64.5 </ td> <td> 1.20 </ td> <td> 0.30 </ td> <td> 40.0 </ td> <td> 75.0 </ td> </ tr> <tr> <td> 2.4 </ td> <td> 1250 </ td> <td> 500 </ td> <td> 7.9 </ td> <td> 88.9 </ td> < td> 5.4 </ td> <td> 64.5 </ td> <td> 1.20 </ td> <td> 0.30 </ td> <td> 50.0 </ td> <td> 75.0 </ td> </ tr > <tr> <td> 2.4 </ td> <td> 1250 </ td> <td> 450 </ td> <td> 7.9 </ td> <td> 106.7 </ td> <td> 6.5 </ td> <td> 77.4 </ td> <td> 1.44 </ td> <td> 0.40 </ td> <td> 40.0 </ td> <td> 72.2 </ td> </ tr> <tr> <td> 3.0 </ td> <td> 1250 </ td> <td> 469 </ td> <td> 7.9 </ td> <td> 111.1 </ td> <td> 6.7 </ td> <td> 80.7 </ td> <td> 1.50 </ td> <td> 0.40 < / td> <td> 50.0 </ td> <td> 73.3 </ td> </ tr> <tr> <td> 3.0 </ td> <td> 1250 </ td> <td> 450 </ td> <td> 7.9 </ td> <td> 133.3 </ td> <td> 8.1 </ td> <td> 96.8 </ td> <td> 1.80 </ td> <td> 0.50 </ td> <td > 40.0 </ td> <td> 72.2 </ td> </ tr> <tr> <td> 3.0 </ td> <td> 1250 </ td> <td> 375 </ td> <td> 7.9 < / td> <td> 133.3 </ td> <td> 8.1 </ td> <td> 96.8 </ td> <td> 1.80 </ td> <td> 0.60 </ td> <td> 40.0 </ td > <td> 66.7 </ td> </ tr> <tr> <td> 3.0 </ td> <td> 1250 </ td> <td> 357 </ td> <td> 7.9 </ td> <td > 148.1 </ td> <td> 9.0 </ td> <td> 107.5 </ td> <td> 2.00 </ td> <td> 0.70 </ td> <td> 33.3 </ td> <td> 65.0 </ td> </ tr> <tr> <td> 3.5 </ td> <td> 1250 </ td> <td> 250 </ td> <td> 7.9 </ td> <td> 148.1 </ td > <td> 9.0 </ td> <td> 107.5 </ td> <td> 2.80 </ td> <td> 1.00 </ td> <td> 20.0 </ td> <td> 64.3 </ td> < / tr> </ TBODY> </ TABLE>

Through the first cold rolling mill 31, the steel strip can be pre-compressed before annealing and pickling operations, so as to reduce the thickness of the compression required for subsequent rolling operations, thereby avoiding the steel strip from rolling in the second rolling. In the case of the rolling unit 7, the strip breaking rate is increased because the rolling reduction of the rolled sheet is too large. When the steel strip passes through the first cold rolling mill 31 and the second cold rolling mill 71, it is transported in one direction without rolling back and forth, so that the production line can be continuously produced, and the production line production rate and Productivity. In addition, the preliminary rolling of the first cold rolling mill 31 can also reduce the amount of scale on the steel strip, thereby reducing the number and length of rust removal equipment, and can reduce the pickling concentration and the time of the pickling operation, thereby reducing Material cost of equipment, blasting and acid solution.

In summary, the first cold rolling mill 31 can perform preliminary rolling before the annealing and pickling process, which can not only reduce the thickness of the rolling required for the second rolling, but also improve the product yield, and The black rolled steel coil after preliminary rolling can reduce the scale of 30 to 70%, which can reduce the number and length of rust removal equipment, and reduce the pickling concentration and shorten the pickling time, so it can indeed achieve the purpose of cost invention. .

However, the above are only examples of the present invention. When the scope of implementation of the present invention cannot be limited in this way, any simple equivalent changes and modifications made in accordance with the scope of the patent application and the content of the patent specification of the present invention are still Within the scope of the invention patent.

1 ······ Composite cold-rolled line 2 ····· Feeding unit 21 ···· Feeding area 211 ···· Unwinding station 22 ··· ······················································································ Furnace area 42 ..... Rusty shredder 43..Blasting machine 44 ..... Grinding brush roller 5 ...... Pickling unit 51 ... ···································· Material area 62 ····· 2nd welding machine 7 ···· 2nd rolling unit 71 ··· 2nd cold rolling mill 8 ···· Unit 81 ... Alkali washing area 82 ... Second detector 83 ... Discharging area 831 ... Rewinding station 9 ... Accumulation unit 91 ... First accumulation area 92 ... Second accumulation area 93 ... Third accumulation area 94 ... Fourth accumulation Area 95 ......... Fifth accumulation area

Other features and effects of the present invention will be clearly presented in the embodiment with reference to the drawings, wherein: FIG. 1 is a production line diagram illustrating a conventionally well-known stainless steel cold rolling process; FIG. 2 is a production line diagram illustrating An embodiment of the composite cold rolling line of the present invention; and FIG. 3 is a flowchart illustrating the process flow of this embodiment.

Claims (8)

A composite cold-rolling line is used to continuously make an input black skin steel coil into a cold-rolled thin hard steel coil. The composite cold-rolling line includes: a feeding unit for unwinding the black skin steel coil. The coil is a steel strip and is conveyed downstream; a first rolling unit includes two or three first cold rolling mills which are arranged next to each other and are connected downstream of the feeding unit; an annealing and rust removing unit, which is continued Downstream of the first rolling unit, the steel strip is annealed and mechanically derusted. The annealing and descaling unit includes a horizontal chain type structure and is connected to a furnace downstream of the first rolling unit. Zone, a rust crusher downstream of the furnace zone, at least one blasting zone downstream of the ruster, and a grinding brush roller downstream of the blasting zone; an acid cleaning unit , Is connected downstream of the annealing and descaling unit, and performs pickling and chemical descaling treatment on the steel strip; a second rolling unit includes five adjacent to each other and is connected downstream of the pickling unit Second cold rolling mill; and a return unit, then And rolling units to the second downstream. The composite cold rolling line according to claim 1, wherein the first cold rolling mill of the first rolling unit is configured to continuously roll the passed steel strip, and the first cold rolling The maximum total rolling reduction of the rolling mill is 50%. The composite cold rolling line according to claim 1, wherein the second cold rolling mill of the second rolling unit is configured to continuously roll the passed steel strip, and the second cold rolling unit The maximum total reduction of the rolling mill is 75%. The composite cold rolling line according to claim 1, wherein the pickling unit includes a first pickling zone downstream of the abrasive brush roller, and a downstream of the first pickling zone A second pickling zone that uses a different solution from the first pickling zone for pickling, and a first detector connected downstream of the second pickling zone. The composite cold rolling line according to claim 4, wherein the feeding unit includes a feeding area, and a downstream of the feeding area for welding different black skin steel coils The first welding machine. The composite cold rolling line according to claim 5, wherein the unloading unit includes an alkali washing zone downstream of the second rolling unit, and a first washing zone downstream of the alkali washing zone. Two detectors, and a discharge area downstream of the second detector. The composite cold rolling line according to claim 6, further comprising a unloading unit located between the pickling unit and the second rolling unit, the unwinding unit including a pickling unit connected to the pickling unit The first stripping zone downstream of the first detector, and a second welding machine downstream of the stripping zone, when the first detector detects that the quality of the passed steel strip is substandard, the The steel strip is guided to the unloading area and cuts off the substandard steel strip. The second welding machine is used to weld the two cut off steel strips. The composite cold rolling line according to claim 7, further comprising an accumulation unit, the accumulation unit includes a first welding machine connected to the feeding unit and a first welding machine between the first rolling unit. An accumulation area, a second accumulation area connected between the first rolling unit and the annealing and descaling unit, and a second accumulation area connected to the withdrawal area of the pickling unit and the withdrawal unit Three accumulation areas, a second welding machine connected to the withdrawal unit and a fourth accumulation area between the second rolling unit, and a second detector and a place connected to the withdrawal unit. The fifth accumulation area of the discharge interval is described.