CN114054515A - Method for controlling cold rolling base material iron scale after rolling - Google Patents
Method for controlling cold rolling base material iron scale after rolling Download PDFInfo
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- CN114054515A CN114054515A CN202110676134.5A CN202110676134A CN114054515A CN 114054515 A CN114054515 A CN 114054515A CN 202110676134 A CN202110676134 A CN 202110676134A CN 114054515 A CN114054515 A CN 114054515A
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- 238000005096 rolling process Methods 0.000 title claims abstract description 61
- 238000000034 method Methods 0.000 title claims abstract description 51
- 239000000463 material Substances 0.000 title claims abstract description 24
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 title description 54
- 229910052742 iron Inorganic materials 0.000 title description 26
- 238000005097 cold rolling Methods 0.000 title description 8
- 238000001816 cooling Methods 0.000 claims abstract description 103
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 91
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 47
- 239000010959 steel Substances 0.000 claims abstract description 47
- 239000007921 spray Substances 0.000 claims abstract description 33
- 238000010438 heat treatment Methods 0.000 claims abstract description 17
- 239000000498 cooling water Substances 0.000 claims abstract description 15
- 238000004321 preservation Methods 0.000 claims abstract description 11
- 239000002184 metal Substances 0.000 claims description 19
- 229910052751 metal Inorganic materials 0.000 claims description 19
- 239000000446 fuel Substances 0.000 claims description 12
- 238000006073 displacement reaction Methods 0.000 claims description 7
- 238000002791 soaking Methods 0.000 claims description 5
- 240000008866 Ziziphus nummularia Species 0.000 claims description 2
- 238000007599 discharging Methods 0.000 claims description 2
- 239000003245 coal Substances 0.000 claims 1
- 230000007547 defect Effects 0.000 abstract description 11
- 238000005554 pickling Methods 0.000 abstract description 11
- 238000001514 detection method Methods 0.000 abstract description 2
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 22
- 230000000694 effects Effects 0.000 description 13
- 230000003647 oxidation Effects 0.000 description 6
- 238000007254 oxidation reaction Methods 0.000 description 6
- 229910000859 α-Fe Inorganic materials 0.000 description 4
- 239000002253 acid Substances 0.000 description 3
- 238000005422 blasting Methods 0.000 description 3
- 238000006243 chemical reaction Methods 0.000 description 3
- 238000005098 hot rolling Methods 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 230000001590 oxidative effect Effects 0.000 description 3
- 238000005406 washing Methods 0.000 description 3
- 229910052785 arsenic Inorganic materials 0.000 description 2
- 229910052804 chromium Inorganic materials 0.000 description 2
- 229910052802 copper Inorganic materials 0.000 description 2
- 239000013078 crystal Substances 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
- 230000003116 impacting effect Effects 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- 238000007373 indentation Methods 0.000 description 2
- 229910052748 manganese Inorganic materials 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 229910052750 molybdenum Inorganic materials 0.000 description 2
- 229910052758 niobium Inorganic materials 0.000 description 2
- 238000005507 spraying Methods 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 229910052718 tin Inorganic materials 0.000 description 2
- 230000009466 transformation Effects 0.000 description 2
- 229910052720 vanadium Inorganic materials 0.000 description 2
- 206010027146 Melanoderma Diseases 0.000 description 1
- 206010039509 Scab Diseases 0.000 description 1
- 238000005452 bending Methods 0.000 description 1
- 238000005266 casting Methods 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 239000010960 cold rolled steel Substances 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 238000009749 continuous casting Methods 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 238000011143 downstream manufacturing Methods 0.000 description 1
- 238000007689 inspection Methods 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- SZVJSHCCFOBDDC-UHFFFAOYSA-N iron(II,III) oxide Inorganic materials O=[Fe]O[Fe]O[Fe]=O SZVJSHCCFOBDDC-UHFFFAOYSA-N 0.000 description 1
- 230000000877 morphologic effect Effects 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
- 238000007747 plating Methods 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B45/00—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills
- B21B45/04—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills for de-scaling, e.g. by brushing
- B21B45/06—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills for de-scaling, e.g. by brushing of strip material
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B37/00—Control devices or methods specially adapted for metal-rolling mills or the work produced thereby
- B21B37/74—Temperature control, e.g. by cooling or heating the rolls or the product
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B45/00—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills
- B21B45/02—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills for lubricating, cooling, or cleaning
- B21B45/0203—Cooling
- B21B45/0209—Cooling devices, e.g. using gaseous coolants
- B21B45/0215—Cooling devices, e.g. using gaseous coolants using liquid coolants, e.g. for sections, for tubes
- B21B45/0233—Spray nozzles, Nozzle headers; Spray systems
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- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Metal Rolling (AREA)
Abstract
A method for controlling the scale of a cold-rolled base material after rolling comprises the following steps: heating and heat preservation, furnace back descaling, rough rolling, intermediate blank descaling, finish rolling, laminar cooling and coiling, wherein in the laminar cooling step, a plurality of rows of bottom water spray nozzles are arranged, and a sparse cooling and concentrated cooling two-stage cooling mode is adopted, wherein the sparse cooling mode cools the hot-rolled strip steel to 780-820 ℃ at a cooling speed of 20-30 ℃/s, and the pressure of laminar cooling water is controlled to be 4.7-5.3 bar; cooling at a cooling speed of 40-50 ℃/s in a centralized cooling mode, controlling the pressure of laminar cooling water to be 6.8-7.2 bar, cooling the hot-rolled strip steel to 560-600 ℃, and then performing a coiling step. By adopting the method, the surface of the finished product strip steel is checked to be clean and clean, no oxide scale defect is generated, the thickness of the oxide scale is only 6-8 mu m through detection, the pickling speed of a customer is tracked, the pickling speed can be increased to 180m/min, the surface of a pickling plate is smooth and clean, the problem of incomplete pickling is avoided, and the use requirement of a user is completely met.
Description
Technical Field
The invention relates to a steel rolling method, in particular to a method for controlling cold rolling base material iron scale after rolling.
Background
The hot rolled plate strip is one of the most widely applied and largest-scale products of all steel products. With the rapid and vigorous development of modern industrial economy, the use requirements of production enterprises on steel products are higher and higher, hot-rolled steel strips replacing cold steel sheets by hot are the development trend of the steel industry, more users begin to use hot-rolled steel sheets to replace cold-rolled steel sheets, such as the industries of household appliances, automobiles, buildings and the like, more and more hot-rolled steel strips gradually replace cold-rolled products with the same specification, and the requirements for manufacturing appearance structural members by the hot-rolled products are increased continuously, so that the requirements of markets and users on the surface quality of the hot-rolled steel strips are higher and higher, and the requirements on high-added-value steel products are also increasingly strict. The cold rolled base material is a hot rolled strip which is subjected to cold rolling in a cold rolling mill after hot rolling. The surface quality defects of the hot rolled strip steel are various, such as scabs, tilted skins, inclusions, scratches, roll marks, scale indentation and the like, wherein the scale indentation defect is a quality defect which is very common in hot rolled strip steel products and has a great influence on the use of downstream users. The thickness of the iron scale is 12-16 μm in general, and the thickness of the iron scale at the black spot of the side plate can reach 20 μm. For serious iron scale defects, not only is the subsequent pickling treatment difficult to completely remove, but also residual iron scale defects still exist even after cold rolling, and further deep processing production such as stamping, coating and plating in downstream processes is influenced. In view of this, how to coordinate the rolling and cooling control process and the control process of the oxide scale morphological structure in the process is a key and difficult point for improving the surface quality of the hot-rolled strip steel.
Disclosure of Invention
The invention provides a method for controlling the scale on a cold-rolled base material after rolling, which changes the scale component on the surface of the cold-rolled base material after rolling by adjusting a hot rolling process and achieves the aims of reducing the scale generation amount and improving the pickling efficiency.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
a method for controlling the scale of a cold-rolled base material after rolling comprises the following steps: heating and heat preservation, furnace back descaling, rough rolling, intermediate billet descaling, finish rolling, laminar cooling and coiling, wherein the laminar cooling step is provided with a plurality of rows of bottom water spray nozzles, and adopts a sparse cooling and concentrated cooling two-stage cooling mode, and the specific operation is as follows: closing the bottom water spray nozzles in the first three rows, wherein the bottom water spray nozzles in the third row to the first two thirds are in a sparse cooling mode of closing at intervals; the bottom water nozzles in the last third row adopt a centralized cooling mode that all water nozzles are opened except the last three rows, and the last three water discharging nozzles are closed; wherein the sparse cooling mode is used for cooling the hot-rolled strip steel to 780-820 ℃ at a cooling speed of 20-30 ℃/s, and the laminar cooling water pressure is controlled to be 4.7-5.3 bar; cooling at a cooling speed of 40-50 ℃/s in a centralized cooling mode, controlling the pressure of laminar cooling water to be 6.8-7.2 bar, cooling the hot-rolled strip steel to 560-600 ℃, and then performing a coiling step.
The method for controlling the rolled cold-rolled base material scale comprises the step of descaling the intermediate blank, wherein a descaling device is arranged between a flying shear and a descaling box in front of a finish rolling rack, the descaling device is provided with two water collecting pipes, a row of descaling water nozzles are uniformly distributed on each water collecting pipe, and the angle A between the axis of each descaling water nozzle and the intermediate blank is 70-75 degrees.
In the method for controlling the rolled cold-rolled base material scale, each scale breaking water nozzle is provided with a special-shaped nozzle, the special-shaped nozzles are date-pit-shaped, and the inclination angle B of the special-shaped nozzles relative to the horizontal plane is 12-15 degrees.
According to the method for controlling the rolled cold-rolled base material iron oxide scale, the bottom water spray nozzles in the laminar cooling step are arranged on the drainage nozzle frames in rows, every six rows of bottom water spray nozzles are one cooling unit, the bottom water spray nozzles in adjacent rows in each cooling unit are distributed in a staggered mode, each row of bottom water spray nozzles in each cooling unit sequentially move for a distance in the same direction, the sequential movement directions of the bottom water spray nozzles in the adjacent cooling units are opposite, and the displacement distances are the same.
According to the method for controlling the rolled cold-rolled base material iron oxide scale, the closest distance between the bottom water spray nozzle at the end part of each cooling unit and the strip steel guard plate is 25-40 mm, the farthest distance is 90-102 mm, the displacement of the bottom water spray nozzles in adjacent rows in the same cooling unit is L, and the L is 10-17 mm.
According to the method for controlling the rolled cold-rolled base material iron oxide scale, the scale breaking device further comprises a first hot metal detector and a second hot metal detector, the first hot metal detector is located in front of the flying shears, and the second hot metal detector is located between the flying shears and the water collecting pipe.
According to the method for controlling the scale of the cold-rolled base material after rolling, the scale breaking water pressure in the intermediate blank scale breaking step is 1.2-1.5 MPa.
In the method for controlling the rolled cold-rolled base material iron scale, in the rough rolling descaling step, all rolling passes are started by high-pressure water for descaling, and the rough rolling outlet temperature range is 1000-1030 ℃.
In the method for controlling the rolled cold-rolled base material iron scale, in the heating and heat preservation step, the heating temperature range of the billet is 1240-1250 ℃, the air-fuel ratio of the first section is controlled to be 0.8-1.0, the air-fuel ratio of the second section is controlled to be 0.6-0.8, the air-fuel ratio of the soaking section is controlled to be 0.4-0.6, and the furnace pressure is controlled to be 11-13 Pa.
According to the method for controlling the rolled cold-rolled base material iron scale, the inlet temperature of finish rolling is controlled to be 940-1000 ℃, the finish rolling speed is controlled to be 630-660 m/min, and the outlet temperature of finish rolling is 890-920 ℃.
Compared with the prior art, the method has the following main advantages: 1. laminar cooling adopts a segmental cooling mode of front-section sparse and rear-section concentrated, the front section controls the size of ferrite grains through sparse cooling, the toughness and the stamping forming performance of the hot-rolling cold-rolling base material are improved, and single FeO is generated; the back section controls the FeO structure transformation of the third scale through rapid cooling, reduces the scale generation amount in the cooling process, and inhibits the pro-eutectoid or eutectoid reaction in the coiling process from being transformed into alpha-Fe and Fe3O4The mixture forms four times of iron scales with different structures, and the consistency of the components of the iron scales is ensured. 2. The scale breaking device is used between rough rolling and finish rolling descaling for carrying out scale breaking treatment on a rough rolling intermediate billet, the scale breaking device is used for carrying out strong blasting and impact on the scale oxide, so that cracks are formed on the surface of the oxide layer, and then in the finish rolling high-pressure water descaling process, high-pressure water enters the interface between the oxide layer and a billet base body through the cracks, so that secondary scale oxide on the surface of the billet is effectively removed, and the surface quality of the intermediate billet is improved. 3. The arrangement mode of the existing laminar cooling bottom water spray nozzle is improved, so that the whole width direction of the lower surface of the strip steel is uniformly and effectively cooled, the transverse cooling uniformity of the surface of the strip steel is greatly improved, the color difference of the surface of a product caused by watermarks appearing due to nonuniform temperature is avoided, and the transverse distribution uniformity of iron scales generated in the laminar cooling process is ensured. 4. The rough rolling outlet temperature range is controlled, the traditional odd-number pass descaling is improved into 5 rolling passes, high-pressure water descaling is started, the descaling effect is enhanced after even-number pass descaling is increased, the generation of pressed scale defects in the rolling process is avoided, and the surface quality of a rough rolling intermediate blank is further improved. 5. Controlling the heating temperature range, gradually reducing the oxidizing atmosphere in the furnace, controlling the air-fuel ratio of the first section to be 0.8-1.0, controlling the air-fuel ratio of the second section to be 0.6-0.8, and controlling the air-fuel ratio of the soaking section to be air-fuel ratioThe temperature is controlled to be 0.4-0.6, and the furnace pressure is controlled to be 11-13 Pa. On the premise of lower temperature before heat preservation of the plate blank, the generation amount of the iron scale is reduced, and simultaneously, the main component of the generated iron scale is FeO which is easy to remove. By adopting the method, the surface of the finished product strip steel is checked to be clean and bright, no iron oxide scale defect is generated, and the detected thickness of the iron oxide scale is only 6-8 mu m, which is reduced by 50 percent compared with the traditional method. The acid washing speed can be increased to 180m/min, the surface of the acid washing plate is smooth, the problem of incomplete acid washing does not exist, and the use requirement of a user is completely met.
Drawings
FIG. 1 is a schematic view of a bottom water nozzle arrangement (two cooling units are shown) during a laminar cooling step;
FIG. 2 is a schematic view of the installation position of the scale breaking device;
FIG. 3 is a view from D of FIG. 2 (not to scale);
FIG. 4 is a side view of FIG. 2 (not to scale);
fig. 5 is a view (not to scale) of fig. 4 in the direction of C.
The list of labels in the figure is: 1. the cooling water tower comprises a cooling water tower 2, a cooling water pipeline 3, a strip steel guard plate 4, a water nozzle frame 5, a bottom water nozzle 6, a first cooling unit 7 and a second cooling unit; 8. the device comprises an intermediate billet, 9, a first hot metal detector, 10, a flying shear, 11, a second hot metal detector, 12, a water collecting pipe, 13, a scale breaking water nozzle, 13-1, a special-shaped nozzle, 14, a scale removing box, 15 and a roller way.
Detailed Description
The cold rolling base material comprises the following chemical components: less than or equal to 0.08 percent of C, less than or equal to 0.03 percent of Si, less than or equal to 0.3 percent of Mn which is more than or equal to 0.15 percent, less than or equal to 0.025 percent of P, less than or equal to 0.025 percent of S, less than or equal to 0.02 percent of Al, less than or equal to 0.055 percent of As, less than or equal to 0.02 percent of Ti, and the balance of Fe and inevitable impurities (Cr, Cu, Sn, V, Mo and Nb). The method comprises the following steps: heating and heat preservation → furnace back descaling → rough rolling → intermediate billet descaling → finish rolling → laminar cooling → coiling.
In the heating and heat preservation step, the heating temperature range is set to 1240-1250 ℃, and the oxidizing atmosphere in the furnace is gradually reducedAnd the air-fuel ratio of the first section is controlled to be 0.8-1.0, the air-fuel ratio of the second section is controlled to be 0.6-0.8, the air-fuel ratio of the soaking section is controlled to be 0.4-0.6, and the furnace pressure is controlled to be 11-13 Pa. On the premise of low temperature before heat preservation of the plate blank, the generation amount of the iron scale is reduced, the oxidizing atmosphere is enhanced to fully combust a medium, the combustion efficiency is improved, meanwhile, the main component of the generated iron scale is FeO which is easy to remove, and the higher the temperature is in the process of heating and heat preservation, the more the iron scale is generated in unit time. As the heating temperature of the steel billet rises, the diffusion of various components is accelerated, the equilibrium constant of the chemical reaction between furnace gas and steel also changes, conditions are created for accelerating oxidation, and the oxidation of the steel is accelerated. The heating temperature and the oxidation burning loss of the steel billet are in an exponential relationship, and the rate of the heating temperature and the oxidation burning loss of the steel billet are increased very quickly. Therefore, the oxidation atmosphere in the furnace is gradually reduced in the heat preservation section, the oxidation degree of the plate blank is reduced, and the magnetic iron scale Fe is greatly reduced3O4The scale removal effect after the furnace is improved.
The rough rolling descaling step improves rough rolling descaling passes, the traditional odd-pass descaling is improved into 5 rolling passes, high-pressure water descaling is started, even-pass descaling is increased, the descaling effect is enhanced, the generation of pressed scale defects in the rolling process is avoided, and the surface quality of a rough rolling intermediate blank is further improved.
The invention adds the step of crushing scale of the intermediate billet, and aims to solve the problem of pressing in of the scale which is caused by incomplete removal of the scale of the intermediate billet. Referring to fig. 2 to 5, a scale breaking device is installed between the flying shear 10 and the finish rolling descaling box 14 in front of the finish rolling stand. In the process of conveying the rough rolling intermediate billet 8 to finish rolling, firstly blasting and impacting the iron scale through a scale breaking device to enable the surface of the intermediate billet to generate cracks, and then entering a descaling box for descaling. And the high-pressure water in the descaling box enters the interface between the oxide layer and the billet base body through cracks generated by the surface impact of the oxide layer, so that the secondary oxide scale on the surface of the billet is effectively removed. The surface quality of the intermediate blank is improved, the pressing-in defect of the iron scale is effectively controlled, and the surface quality of the strip steel is favorably improved. The scale breaking device is provided with two water collecting pipes 12, a row of scale breaking water nozzles 13 are uniformly distributed on each water collecting pipe, and the angle A between the axis of each scale breaking water nozzle and the intermediate blank is 70-75 degrees. Each scale breaking water nozzle is provided with a special-shaped nozzle 13-1, the special-shaped nozzles are in a jujube core shape, the inclination angle B of the special-shaped nozzles relative to the horizontal plane is 12-15 degrees, and a water outlet similar to a cutting edge is formed. The length L of the special-shaped nozzle is 8-10 mm, the width H of the special-shaped nozzle is 3 mm, the length direction of the special-shaped nozzle is consistent with the width direction of the middle blank, and water flow jetted by the special-shaped nozzle is distributed in a sector shape and covers the whole surface of the middle blank. The pressure of the scale breaking water is 1.2-1.5 Mpa. The scale breaking device further comprises a first hot metal detector 9 and a second hot metal detector 11, the first hot metal detector is located in front of the flying shears, and the second hot metal detector is located between the flying shears and the water collecting pipe. The two hot metal detectors are installed because the first metal detector is linked with the flying shears, namely, a strip steel signal is detected, and the circuit is closed after the strip steel comes; the second metal detector is turned on to start spraying water. When the first hot metal detector and the second hot metal detector detect the intermediate billet signals, the electromagnetic valve connected with the water collecting pipe is electrified, the scale breaking water nozzle starts to spray water flow, and blasting and impacting are carried out on the intermediate billet iron oxide scale; when the strip steel is rolled to an F7 finishing mill (a final finishing mill), a load signal is switched on, the electromagnetic valve is powered off, and the scale breaking water nozzle stops spraying.
The laminar cooling step is an important step of the improvement of the invention, and the laminar cooling adopts a front-section sparse and rear-section concentrated segmental cooling mode. The laminar cooling step is provided with a plurality of rows of bottom water nozzles, and the operation is as follows: closing the first three rows of bottom water spray nozzles, and adopting a sparse cooling mode of closing every other row from the third row to the first two thirds rows (taking the whole) of bottom water spray nozzles; the bottom water nozzles in the last third row (the whole row) adopt a centralized cooling mode that all water nozzles are opened except the last three rows, and the last three water nozzles are closed; wherein the sparse cooling mode is used for cooling the hot-rolled strip steel to 780-820 ℃ at a cooling speed of 20-30 ℃/s, and the laminar cooling water pressure is controlled to be 4.7-5.3 bar; cooling at a cooling speed of 40-50 ℃/s in a centralized cooling mode, controlling the pressure of laminar cooling water to be 6.8-7.2 bar, cooling the hot-rolled strip steel to 560-600 ℃, then performing a coiling step, and finally performing air cooling for 10 hours to reach the room temperature. Front section control of ferrite crystals by sparse coolingThe grain size improves the toughness and the punch forming performance of the hot-rolled and cold-rolled base material, and simultaneously generates single FeO. The back section controls the FeO structure transformation of the third scale through rapid cooling, reduces the scale generation amount in the cooling process, and inhibits the pro-eutectoid or eutectoid reaction from being transformed into alpha-Fe and Fe in the coiling process3O4The mixture forms four times of iron scales with different structures, and the consistency of the components of the iron scales is ensured. Under the optimization characteristic effects of low iron scale generation amount and high consistency of iron scale components, the efficiency of a subsequent pickling process is improved, and the surface quality of a downstream cold-rolled product is ensured. The purpose of closing the first three rows of bottom nozzles is as follows: firstly, crystal grains have a growth process, so that fine grains are avoided; and secondly, the influence of the backflow of cooling water on the inspection precision of the instrument is avoided. The purpose of closing the rear three rows of bottom nozzles is as follows: prevent the cooling water from flowing into the coiling machine to cause uneven performance of the steel strip.
Referring to fig. 1, laminar flow-cooled bottom water nozzles 5 are installed in rows on each water nozzle rack 4, and a cooling water tower 1 is communicated with a plurality of bottom water nozzles 5 through a cooling water pipe 2. Every six rows of bottom water spray nozzles are cooling units, the bottom water spray nozzles of adjacent rows in each cooling unit are distributed in a staggered mode, each row of bottom water spray nozzles in each cooling unit sequentially move for a distance towards the same direction, the sequential movement directions of the bottom water spray nozzles of the adjacent rows in the adjacent cooling units are opposite, and the displacement distances are the same. The shortest distance between the bottom water spray nozzles at the end part of each cooling unit and the strip steel guard plate 3 is 25-40 mm, the longest distance is 90-102 mm, the displacement of the bottom water spray nozzles in adjacent rows in the same cooling unit is L, and the L is 10-17 mm. The laminar flow cooling bottom water nozzles are arranged in 168 rows, the structural arrangement of the first cooling unit 6 and the second cooling unit 7 is shown in figure 1, and other cooling units are arranged according to the arrangement sequence shown in figure 1. The invention improves the traditional design of the center alignment arrangement of the bottom water spray nozzles into the staggered arrangement, ensures that the whole width direction of the lower surface of the strip steel is uniformly and effectively cooled in the laminar cooling process after the staggered arrangement, greatly improves the transverse cooling uniformity of the surface of the strip steel, avoids the color difference of the product surface caused by the watermark appearing due to the nonuniform transverse temperature, ensures the transverse distribution uniformity of the oxide scales generated in the laminar cooling process, and has obvious effect on reducing the oxide scales at the edge of the strip steel.
Examples are provided below:
the hot-rolled and cold-rolled base material molten steel comprises the following chemical components: less than or equal to 0.08 percent of C, less than or equal to 0.03 percent of Si, less than or equal to 0.3 percent of Mn which is more than or equal to 0.15 percent, less than or equal to 0.025 percent of P, less than or equal to 0.025 percent of S, less than or equal to 0.02 percent of Al, less than or equal to 0.055 percent of As, less than or equal to 0.02 percent of Ti, and the balance of Fe and inevitable impurities (Cr, Cu, Sn, V, Mo and Nb).
Casting into a continuous casting billet with the thickness of 10200mm multiplied by 1010mm multiplied by 200mm and the thickness of 10200mm multiplied by 920mm multiplied by 200 mm. Heating and preserving heat in a heating furnace, wherein the soaking temperature is 1240-1250 ℃, the steel is sent to a roughing mill for five passes after being descaled by 20MPa high-pressure water after the steel passes through the furnace, and the descaling by the 20MPa high-pressure water is started in each pass; the thickness of the intermediate blank is 38 mm. Conveying the steel plate to a fine rolling mill through a middle roller way, performing scale breaking through 1.2Mpa of scale breaking water before flying shear, and then rolling through seven finishing mill groups, wherein the inlet temperature is controlled to be 940-1000 ℃, the fine rolling speed is controlled to be 630-660 m/min, and the outlet temperature is controlled to be 890-920 ℃; the laminar cooling is carried out by arranging 168 rows of bottom water spray nozzles, closing the front three rows and the rear three rows, opening the fourth row to the 112 th water discharge nozzles at intervals, and cooling to 780-820 ℃ at the cooling speed of 20-30 ℃/s; cooling the material from the 113 th row to the 165 th row to 560 ℃ to 600 ℃ at a cooling rate of 40-50 ℃/s, and coiling the material. Finally cooling to room temperature by air cooling for 10 hours. The finished product of the strip steel is checked to be clean and smooth in surface, the scale defects are not generated, the thickness of the scale is only 6-8 mu m through detection, the pickling speed of a customer is tracked, the pickling speed can be increased to 180m/min, the surface of a pickling plate is smooth and clean, the problem of incomplete pickling is avoided, and the use requirements of users are completely met.
The detailed process parameters are shown in Table 1, the surface quality tracking condition is shown in Table 2, and the mechanical properties are shown in Table 3.
TABLE 1 Process parameter control
TABLE 2 surface quality tracking
TABLE 3 statistics of mechanical Properties
| Serial number | Yield strength (MPa) | Tensile strength (MPa) | Elongation (%) | Yield ratio | Cold bending property |
| 1 | 254 | 334 | 49 | 0.7 | |
| 2 | 260 | 338 | 50.5 | 0.75 | |
| 3 | 256 | 333 | 49 | 0.74 | |
| 4 | 239 | 322 | 49 | 0.78 | |
| 5 | 265 | 331 | 49.5 | 0.75 | |
| 6 | 255 | 334 | 52 | 0.72 | Good effect |
| 7 | 259 | 342 | 51 | 0.76 | Good effect |
| 8 | 265 | 347 | 50 | 0.78 | Good effect |
Claims (10)
1. A method for controlling the scale of a cold-rolled base material after rolling is characterized by comprising the following steps: the method comprises the following steps: the method comprises the following steps of heating and heat preservation, furnace back descaling, rough rolling, intermediate billet descaling, finish rolling, laminar cooling and coiling, wherein a multi-row-bottom water spray nozzle is arranged in the laminar cooling step, and a sparse cooling and concentrated cooling two-stage cooling mode is adopted, and the method specifically comprises the following operations: closing the bottom water spray nozzles in the first three rows, and adopting a sparse cooling mode of closing the bottom water spray nozzles in the third row to the first two thirds rows at intervals; the bottom water nozzles in the last third row adopt a centralized cooling mode that all water nozzles are opened except the last three rows, and the last three water discharging nozzles are closed; wherein the sparse cooling mode is used for cooling the hot-rolled strip steel to 780-820 ℃ at a cooling speed of 20-30 ℃/s, and the laminar cooling water pressure is controlled to be 4.7-5.3 bar; cooling at a cooling speed of 40-50 ℃/s in a centralized cooling mode, controlling the pressure of laminar cooling water to be 6.8-7.2 bar, cooling the hot-rolled strip steel to 560-600 ℃, and then performing a coiling step.
2. The method for controlling mill scale of cold rolled base stock after rolling as set forth in claim 1, wherein: the intermediate billet descaling step is provided with a descaling device, the descaling device is arranged between a flying shear and a descaling box in front of a finish rolling rack, the descaling device is provided with two water collecting pipes, a row of descaling water nozzles are uniformly distributed on each water collecting pipe, and the angle A between the axis of each descaling water nozzle and the intermediate billet is 70-75 degrees.
3. The method for controlling mill scale of cold rolled base stock after rolling as set forth in claim 2, wherein: each scale breaking water nozzle is provided with a special-shaped nozzle, the special-shaped nozzle is in a jujube core shape, and the inclination angle B of the special-shaped nozzle relative to the horizontal plane is 12-15 degrees.
4. The method for controlling mill scale of cold rolled base stock after rolling as set forth in claim 3, wherein: the bottom water spray nozzles in the laminar cooling step are arranged on each water discharge nozzle frame in rows, every six rows of bottom water spray nozzles are one cooling unit, the bottom water spray nozzles in adjacent rows in each cooling unit are distributed in a staggered mode, each row of bottom water spray nozzles in each cooling unit sequentially move for a distance in the same direction, the sequential displacement directions of the bottom water spray nozzles in each row in the adjacent cooling units are opposite, and the displacement distances are the same.
5. The method for controlling mill scale of cold rolled base stock after rolling as set forth in claim 4, wherein: the shortest distance between the bottom water spray nozzle at the end part of each cooling unit and the strip steel guard plate is 25-40 mm, the farthest distance is 90-102 mm, the displacement of the bottom water spray nozzles adjacent to each other in the same cooling unit is L, and the L is 10-17 mm.
6. The method for controlling mill scale of cold rolled base stock after rolling as set forth in claim 5, wherein: the scale breaking device further comprises a first hot metal detector and a second hot metal detector, the first hot metal detector is located in front of the flying shears, and the second hot metal detector is located between the flying shears and the water collecting pipe.
7. The method for controlling mill scale of cold rolled base stock after rolling as set forth in claim 6, wherein: and the scale breaking water pressure in the intermediate blank scale breaking step is 1.2-1.5 MPa.
8. The method for controlling mill scale of cold rolled base stock after rolling as set forth in claim 7, wherein: in the rough rolling descaling step, all rolling passes are started to remove scale by high-pressure water, and the rough rolling outlet temperature range is 1000-1030 ℃.
9. The method for controlling mill scale of cold rolled base stock after rolling as set forth in claim 8, wherein: in the heating and heat preservation step, the heating temperature range of the billet is 1240-1250 ℃, the air-fuel ratio of the first section is controlled to be 0.8-1.0, the air-fuel ratio of the second section is controlled to be 0.6-0.8, the air-coal ratio of the soaking section is controlled to be 0.4-0.6, and the furnace pressure is controlled to be 11-13 Pa.
10. The method of controlling mill scale of cold rolled base stock as claimed in claim 9, wherein: the inlet temperature of finish rolling is controlled to be 940-1000 ℃, the finish rolling speed is controlled to be 630-660 m/min, and the outlet temperature of finish rolling is 890-920 ℃.
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| CN115572978A (en) * | 2022-10-25 | 2023-01-06 | 本钢板材股份有限公司 | Rapid and low-acid-consumption hot rolled steel plate pickling method |
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