Method of steel sheet surface treatment and apparatus of the same

Abstract

The present invention relates to a method of steel sheet surface treatment, wherein, the method comprises sequentially: a strip surface treatment unit (1) configured with a high pressure spraying device (1-1) or a centrifugal ejecting device (1-2), a strip surface rinsing unit (2), and a strip surface dry unit (3). Either or both of the high pressure spraying devices (1-1) and the centrifugal ejecting devices (1-2) are arranged, and spray onto the strip surfaces with a mixture of solid abrasives and water, i.e., slurry. Additionally, the method of steel sheet surface treatment comprises: a slurry supplying unit (4) and an abrasive recycling unit (5). When the method of the present invention is applied into the strip post processing line, it can control the surface roughness of the steel sheet, while clearing away grease, scales and some contaminations thereon, through impacting the mixture of water and solid particles with a certain ratio onto the surfaces of the strip steel. When the method of the present invention is applied into the finishing processing line, it can control the surface roughness of the steel sheet, while adjusting the mechanical properties of the strip, thereby completely or partially replacing the skin pass process.

Claims

1. A method of steel sheet surface treatment, the method comprising: spraying at least a portion of a steel sheet surface with a strip surface treatment unit (1) configured with at least one of a high pressure spraying device (1-1) or a centrifugal ejecting device (1-2), wherein either or both of the high pressure spraying device (1-1) and the centrifugal ejecting device (1-2) are arranged to spray a slurry of solid abrasives and water onto at least a portion of the strip surface; rinsing the sprayed steel sheet surface in a strip surface rinsing unit (2); drying the rinsed steel sheet surface in a strip surface dry unit (3); wherein the slurry is provided to the strip surface treatment unit (1) by a slurry supplying unit (4), and the slurry supplying unit (4) supplies slurry with abrasives of different particle sizes and different mixture ratios to each high pressure spraying devices (1-1) or centrifugal ejecting devices (1-2); and recycling at least a portion of the solid abrasives from the slurry in an abrasive recycling unit (5).

2. The method according to claim 1, wherein the slurry of solid abrasives and water comprises a mixture ratio of 10˜95%, and wherein the solid abrasives are selected from the group consisting of iron sand, steel shots, and cut wire shots, and the particle sizes of the solid abrasives are between about 20 and about 100 meshes.

3. The method according to claim 1, wherein the strip surface treatment unit (1) further comprises: a plurality of high pressure spraying devices (1-1) positioned along the width of the steel sheet, wherein the high pressure spraying devices (1-1) cover at least 50˜100 mm of the width of the strip; and 2˜8 rows of high pressure spraying devices (1-1) provided along the running direction of the strip.

4. The method according to claim 1, wherein surface roughness of the strip is controlled between 0.5 μm and 5 μm.

5. The method according to claim 1, wherein the strip surface treatment unit (2) rinses the strip surfaces with water at a pressure 5˜30 MPa, and the strip surface dry unit (3) dries the strip surfaces with hot wind.

6. The method according to claim 1, wherein the speed of the solid abrasives and water impacting onto the strip surface is in the range of 30 m/s˜300 m/s.

7. A steel sheet surface treatment device comprising: at least one strip surface treatment unit (1) configured with at least one high pressure spraying device (1-1) or centrifugal ejecting device (1-2) to spray a slurry of solid abrasives and water, and wherein the centrifugal ejecting devices (1-2) sprays onto the central portion of the strip and wherein the high pressure spraying device (1-1) sprays onto the edge portions of the strip; a strip surface rinsing unit (2) positioned downstream of the strip surface treatment unit device; a strip surface dry unit (3) positioned downstream of the rinsing unit (2); an abrasive supplying device (4); and an abrasive recycling device (5).

8. The device according to claim 7, wherein the slurry comprises a mixture of solid abrasives and water in a ratio of 10˜95%, and the solid abrasives are selected from the group consisting of iron sand, steel shots, and cut wire shots and the particle sizes of the solid abrasives are between 20 and 100 meshes.

9. The device according to claim 7, wherein the strip surface treatment unit (1) comprises: a plurality of high pressure spraying devices (1-1) or centrifugal ejecting devices (1-2) positioned along the width direction of the steel sheet, wherein each spraying device (1-1) covers 50˜100 mm of a width of a strip; and 2˜8 rows of high pressure spraying devices (1-1) arranged along the running direction of the strip.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic view 1 of a strip surface treatment device;

(2) FIG. 2 is a schematic view 2 of a strip surface treatment device;

(3) FIG. 3 is a schematic view of a strip surface pre-treatment process of Embodiment 1;

(4) FIG. 4 is a schematic view of a strip surface pre-treatment process of Embodiment 2;

(5) FIG. 5 is a schematic view of a strip surface pre-treatment process of Embodiment 3;

(6) FIG. 6 is a schematic view of a strip surface pre-treatment process of Embodiment 4;

(7) FIG. 7 is a schematic view of a strip surface pre-treatment process of Embodiment 5;

(8) FIG. 8 is a schematic view of a strip surface pre-treatment process of Embodiment 6;

(9) FIG. 9 is a schematic view of a strip surface pre-treatment process of Embodiment 7;

(10) FIG. 10 shows the distribution of the surface roughness of the strips under Embodiment 1;

(11) FIG. 11 is a comparative view showing the variation of the mechanical properties of the strips under Embodiment 7.

(12) In the drawings, the reference numeral 1 indicates a strip surface treatment unit, 1-1 a high pressure spray device, 1-2 a centrifugal ejecting device, 2 a strip surface washing unit, 3 a strip surface dry unit, 4 a slurry supplying unit, 5 an abrasive recycling unit, 6 a strip, 7 an uncoiler, 8 a welding machine, 9 a coiler, 11 an annealing exit loop, 10 an entry loop, 12 an annealing furnace, 13 a skin-pass mill, 14 an annealing units, 15 a zinc pot.

DETAILED DESCRIPTION

(13) Embodiment 1

(14) Taking the process wherein the separate degreasing units are provided with a strip surface treatment device in the present invention as an example, and referring to FIG. 3, the detailed embodiment is as follows:

(15) The strip in this embodiment is the cold rolled one with a width of 700˜1300 mm and a thickness of 0.2˜3 mm. At this moment, a variety of dirty matters generated during the rolling process remain on the strip surfaces, including rolling oil and oil dreg therein, iron powder generated in the rolling process, accumulating dust, weld slag generated in welding, or the like. The surface roughness of the strip after cold rolling, is 0.7˜0.8 μm, while the required surface roughness by the customer is 1.5 μm.

(16) The strip uncoiled by the uncoiler 7 is welded by the welding machine 8, then enters the steel sheet surface treatment device 1 via the tension rollers, which could be configured with a high pressure spray device 1-1 or a centrifugal ejecting device 1-2 shown as FIG. 1. If the high pressure spray device 1-1 is configured, steel shots with a particle size of 80˜100 meshes are used as the solid abrasive, and the mixture ratio of the steel shots and water is controlled at 50%, and the speed at which the mixture of the steel shots and water impacts on the strip surfaces is 70˜90 m/min. If the centrifugal ejecting device 1-2 is configured in the steel sheet surface treatment device 1, steel shots with a particle size of 80˜100 meshes are used as the solid abrasive, and the mixture ratio of the steel shots and water is 70%, and the speed at which the mixture of the steel shots and water impacts on the strip surfaces, is 70˜90 m/min. The dirty matters on the strip surface treated in this way are impacted by the solid abrasives and water, and leave the strip surface with the suspension liquid, such that the objective of clearing away the dirty matters is achieved. Besides, due to that the solid particles impacting on the strip surfaces, have a certain energy and velocity, and the size of the solid particles is larger than that of the strip, tiny disordering dents are formed on the surfaces thereof, so as to achieve the objective of controlling the surface roughness of the strip. The surface roughness of the strip treated in such a way can reach 1.4˜1.5 μm. The strip treated by the steel sheet surface treatment device 1, enters the strip surface washing unit 2, wherein pure water with a pressure of 20 MPa rinses the surfaces of the strip such that the solid abrasives are separated therefrom and enter the lower portion of the steel sheet surface treatment device 1 before being recycled by the filtering recycle device 5. No solid particle exists on the surface of the strip treated in such a way, which is then dried by hot wind of 100° C. in the strip surface dry unit 3, and coiled by the coiler 9.

(17) The distribution of the surface roughness of the strip treated in this way along the width of the sheet is shown as FIG. 10.

(18) Embodiment 2

(19) Taking the process wherein the continuous annealing units are provided with the strip surface treatment device in the present invention as an example, and referring to FIG. 4, the detailed embodiment is as follows:

(20) The strip in this embodiment is the cold rolled one with a width of 700˜1300 mm and a thickness of 0.2˜3 mm. At this moment, a variety of dirty matters generated during the rolling process remains on the strip surfaces, including rolling oil and oil dreg therein, iron powder generated in the rolling process, accumulating dust, weld slag generated in welding, or the like. The surface roughness of the strip after cold rolling, is 0.7˜0.8 μm, while the required surface roughness by the customer is 1.5 μm.

(21) The strip uncoiled by the uncoiler 7 is welded by the welding machine 8, then enters the steel sheet surface treatment device 1, wherein the treatment is the same as that in Embodiment 1. The strip treated in such a way enters the entry loop 10, before it is annealed by the annealing furnace 12. Then the strip is flattened, leveled, and finally coiled by the coiler, thereby finishing the whole annealing process.

(22) Embodiment 3

(23) Taking the process wherein the continuous hot dip galvanizing units are provided with the strip surface treatment device in the present invention as an example, and referring to FIG. 5, the detailed embodiment is as follows:

(24) The strip uncoiled by the uncoiler 7 is welded by the welding machine 8, then enters the entry loop 10, and subsequently enters the steel sheet surface treatment device 1, wherein the treatment is similar to that in Embodiment 1. The strip treated by the steel sheet surface treatment device 1 is annealed by the annealing furnace 12 before it is hot dip galvanized, thereby finishing the whole hot dip galvanizing process.

(25) Embodiment 4

(26) Taking the process wherein the continuous electrogalvanizing units are provided with the strip surface treatment device in the present invention as an example, and referring to FIG. 5, the detailed embodiment is as follows:

(27) The strips uncoiled by the uncoiler 7 are welded by the welding machine 8, then enter the entry loop 10, and subsequently enter the steel sheet surface treatment device 1, wherein the treatment is similar to that in Embodiment 1. The strip treated by the steel sheet surface treatment device 1 is subsequently electroplated, phosphated, coated, and the like, thereby finishing the whole electrogalvanizing process.

(28) Embodiment 5

(29) Taking the process layout of the method of the present invention in FIG. 7 which is added after the skin pass procedure as an example, and referring to FIGS. 1 and 2, the detailed embodiment is as follows:

(30) In this embodiment, a cold rolled steel sheet with a thickness of 0.3˜0.8 mm and a width of 800˜1200 mm, is used, and when it is flattened, the elongation rate thereof is 0.8%. The skin-pass mill is provided with smooth rollers, and the required roughness of the strip is 1.5 μm.

(31) Taking the process layout in FIG. 7 as an example, the strip 6 uncoiled by the uncoiler 7 passes through the tension rollers, then enters the skin-pass mill 13. The skin-pass mill flattens the steel sheet by an elongation rate of 0.8%, so as to improve the mechanical properties and the shape of the strips. The flattened strip passes though the tension rollers, then enters the strip surface treatment unit 1 which is configured with a abrasive supplying device 4. In the device 4, steel shots with a particle size of 60 meshes are used as the solid abrasives, and the mixture ratio of the solid abrasives and water is 70%. The abrasive supplying device 4 supply the slurry with the above-mentioned mixture ratio to the high pressure spray device 1-1, which provides energy to the slurry, so as to impact the slurry onto the strip surfaces at a speed of 120 m/s. Owing to that the medium impacting the strip surfaces are the mixtures of solid particles and water, a small amount of slurry may remain thereon, and most of slurry will stack beneath the tapered sink. The strip impacted by the slurry enters the strip rinsing unit 2, which uses pure water of 20 MPa to rinse the lower and upper surfaces of the strips, to clear the residual solid particles thereon. Subsequent to it, the strip enters the dry device 3, which dries the steel sheet with high temperature gas of a temperature 100° C., so as to meet the requirements of the following procedures like coiling. Then the strip passes through the tension rollers and is coiled by the coiler 9.

(32) If the steel sheet surface treatment device 1 uses the centrifugal ejecting device 1-2, the mixture ratio of solid particles and water is 60%, and the centrifugal ejecting device 1-2 provides impact energy to the slurry by means of blades, with the impact speed of 120 m/s on the strip surface and the impact density of 2 kg/m.sup.2 per unit area. Other stages are similar to the above-mentioned ones.

(33) Embodiment 6

(34) Taking the process layout of the method of the present invention in FIG. 8 which is added after the skin pass procedure of the continuous annealing process as an example, and referring to FIGS. 1 and 2, the detailed embodiment is as follows:

(35) In this embodiment, a clod rolled steel sheet with a thickness of 0.3˜0.8 mm and a width of 800˜1200 mm, is used, and when it is flattened, the elongation rate thereof is 0.6%. The skin-pass mill is provided with smooth rollers, and the required roughness of the strip is 1.2 μm.

(36) The strip 6 uncoiled by the uncoiler 7 enters the steel sheet cutting and welding units 8, then passes through the entry loop 10 and enters the continuous annealing units 14. There is yield platform in the mechanical properties of the strips treated in such a way, which has an effect on the shaping of strips. The annealed strip passes through the annealing exit loop and enters the skin-pass mill units 13. Tension devices are provided both at the upstream and downstream of the skin-pass mill units. During the skin pass process, the steel sheet is flattened by an elongation rate of 0.6%, so as to eliminate the yield platform existing in the annealed strips and improve the shape of the strip. The flattened strip enters the strip surface treatment unit 1 which is configured with a high pressure spraying device 1-1 as shown in FIG. 1. In the device 1-1, steel shots with a particle size of 80 meshes are used as the abrasives, and the mixture ratio of the solid abrasives and water is 60%. The slurry impacts onto the strip surfaces at a speed of 100 m/s; if the steel sheet surface treatment device 1 is configured with the centrifugal ejecting device 1-2 as shown in FIG. 2. In the device 1-2, steel shots with a particle size of 80 meshes are used as the solid abrasives, and the mixture ratio of solid particles and water is 50%, and the slurry impacts onto the strip surface at a speed of 100 m/s. The strip treated in such a way enters the rinsing device 2 and the dry device 3 in which the process is the same as that of Embodiment 5, and passes through the tension roller units and enters the leveling unit to further improve the shape of the strip, then is coiled by the coiler 9.

(37) Embodiment 7

(38) Taking the process layout of the method of the present invention in FIG. 9 which is added after the skin pass procedure of the continuous annealing process as an example, and referring to FIGS. 1 and 2, the detailed embodiment is as follows:

(39) In this embodiment, a clod rolled steel sheet with a thickness of 0.3˜0.8 mm and a width of 800˜1200 mm, is used, and the required roughness of the strip is 1.2 μm.

(40) The strip 6 uncoiled by the uncoiler 7 enters the strip cutting and welding units 8, then passes through the entry loop 10 and enters the annealing units 14. Subsequently, the annealed strip passes through the annealing exit loop 11 and directly enters the strip surface treatment unit 1. The strip surface treatment unit is provided with tension roller units both at the upstream and downstream thereof and with a plurality of groups of high pressure spraying device 1-1. After the strip enters the device 1-1, the groups 1, 2 of the devices 1-1 sprays the surface of the strip first, wherein the particle size of the impacting abrasives is 30 meshes and the mixture ratio of the slurry is 70%, and the speed of the abrasives impacting onto the strip surfaces is 150 m/s. With the aforementioned treatment, the mechanical properties of the strip can change and the yield platform existing in the annealed strip may vanish. In such a way, the strip enters the groups 3, 4 of high pressure spraying device, wherein the particle size of the impacting abrasives is 80 meshes and the mixture ratio of the slurry is 60%, and the speed of the abrasives impacting onto the strip surfaces is 100 m/s. The surface roughness of the strip treated in the above way has reached the requirement by the customer, and the subsequent strip enters the surface rinsing device 2, which uses pure water of 20 Mpa to wash the upper and lower surfaces of the strip. After that, the strip enters the dry unit 3 that dries the strip surface with pressed air with a temperature of 100° C., so as to satisfy the requirement of coiling process and the like.

(41) If the steel sheet surface treatment device 1 is configured with the centrifugal ejecting device 1-2 as shown in FIG. 2, the embodiment is similar to the above-mentioned, but the impact speed of the slurry sprayed by the groups 1, 2 of the centrifugal ejecting device 1-2 is 150 m/s, and the abrasive particle sizes of the solid particles are 30 meshes, and the mixture ratio of solid particles and water is 60%; while the impact speed of the abrasives sprayed by the groups 3, 4 of the centrifugal ejecting device is 100 m/s, and the abrasive particle sizes of the solid particles are 80 meshes, and the mixture ratio of solid particles and water is 60%.

(42) The comparison between the mechanical properties of the strip treated in this way and the strip prior to treating, is shown in FIG. 11.

(43) According to the present invention, by the method wherein solid mixed abrasives are used to impact onto the strip surface, the surface roughness can be online controlled flexibly, and the dirty matters such as the grease, scales residual on the strip surface can be cleared away. Additionally, it can replace the function of the skin pass procedure completely or partially. Due to the technology in this patent is mature and implemented easily, the spread application is available. Besides, this patent is capable of solving the problem well that the surface roughness cannot be improved because of the incapability of the equipments, and is highly valuable in product extension and the improvement of the product quality. Accordingly the present invention has a wide potential in applying into the filed of steel sheet surface treatment.