CN114054515B - Method for controlling scale of cold rolling base stock after rolling - Google Patents
Method for controlling scale of cold rolling base stock after rolling Download PDFInfo
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- CN114054515B CN114054515B CN202110676134.5A CN202110676134A CN114054515B CN 114054515 B CN114054515 B CN 114054515B CN 202110676134 A CN202110676134 A CN 202110676134A CN 114054515 B CN114054515 B CN 114054515B
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- 238000005096 rolling process Methods 0.000 title claims abstract description 62
- 238000000034 method Methods 0.000 title claims abstract description 53
- 238000005097 cold rolling Methods 0.000 title claims description 10
- 238000001816 cooling Methods 0.000 claims abstract description 97
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 92
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 49
- 239000010959 steel Substances 0.000 claims abstract description 49
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 43
- 229910052742 iron Inorganic materials 0.000 claims abstract description 21
- 238000010438 heat treatment Methods 0.000 claims abstract description 16
- 239000000498 cooling water Substances 0.000 claims abstract description 14
- 239000007921 spray Substances 0.000 claims abstract description 11
- 239000002184 metal Substances 0.000 claims description 18
- 229910052751 metal Inorganic materials 0.000 claims description 18
- 239000000446 fuel Substances 0.000 claims description 8
- 238000006073 displacement reaction Methods 0.000 claims description 6
- 238000004321 preservation Methods 0.000 claims description 6
- 239000003245 coal Substances 0.000 claims description 4
- 238000002791 soaking Methods 0.000 claims description 3
- 238000005554 pickling Methods 0.000 abstract description 12
- 230000007547 defect Effects 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 44
- 230000008569 process Effects 0.000 description 17
- 239000000463 material Substances 0.000 description 11
- 230000003647 oxidation Effects 0.000 description 5
- 238000007254 oxidation reaction Methods 0.000 description 5
- 230000000694 effects Effects 0.000 description 4
- 230000001590 oxidative effect Effects 0.000 description 4
- 230000009466 transformation Effects 0.000 description 4
- 229910000859 α-Fe Inorganic materials 0.000 description 4
- 239000002253 acid Substances 0.000 description 3
- 238000006243 chemical reaction Methods 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 238000003825 pressing Methods 0.000 description 3
- 229910052785 arsenic Inorganic materials 0.000 description 2
- 238000005422 blasting Methods 0.000 description 2
- 229910052804 chromium Inorganic materials 0.000 description 2
- 238000004140 cleaning Methods 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
- 238000005098 hot rolling Methods 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- 229910052748 manganese Inorganic materials 0.000 description 2
- 239000011159 matrix material Substances 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 238000005507 spraying Methods 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 229910052720 vanadium Inorganic materials 0.000 description 2
- 238000005406 washing Methods 0.000 description 2
- 206010039509 Scab Diseases 0.000 description 1
- 240000008866 Ziziphus nummularia Species 0.000 description 1
- 230000009471 action Effects 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
- 238000009749 continuous casting Methods 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 230000003670 easy-to-clean Effects 0.000 description 1
- 230000003116 impacting effect Effects 0.000 description 1
Classifications
-
- 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 scale of a cold rolled base stock after rolling, comprising the steps of: heating and preserving heat, descaling after a furnace, rough rolling and descaling, rough rolling, intermediate billet descaling, finish rolling and descaling, finish rolling, laminar cooling and coiling, wherein a plurality of rows of bottom water spray nozzles are arranged in the laminar cooling step, and a sparse cooling and concentrated cooling two-section 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 laminar cooling water pressure is controlled to be 4.7-5.3 bar; the concentrated cooling mode is used for cooling at a cooling speed of 40-50 ℃/s, the laminar cooling water pressure is controlled at 6.8-7.2 bar, and the hot rolled strip steel is cooled to 560-600 ℃ and then enters a coiling step. The method provided by the invention is used for checking that the surface of the finished strip steel is clean and smooth, no iron scale defect is generated, the thickness of the iron scale is only 6-8 mu m after 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, the problem of unclean 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 scale of a cold rolling base stock after rolling.
Background
Hot rolled strip is one of the most widely used varieties of all steel products with the largest yield specifications. With the rapid development of modern industrial economy, the use requirements of manufacturers on steel products are higher and higher, hot-rolled steel strips which replace cold with hot are a development trend of the steel industry, more users begin to use hot-rolled steel plates to replace cold-rolled steel plates, such as home appliances, automobiles, buildings and other industries, more hot-rolled steel strips gradually replace cold-rolled products with the same specification, and meanwhile, the requirements for manufacturing appearance structural members by hot-rolled products are also increased, so that the requirements of markets and users on the surface quality of the hot-rolled steel strip products are higher and higher, and the requirements on high-added value steel products are also more and more stringent. The cold-rolled base material is hot-rolled strip steel which is subjected to cold rolling processing in a cold rolling mill after hot rolling. The surface quality defects of the hot rolled strip steel are various, such as scab, skin tilting, inclusion, scratch, roll mark, scale pressing and the like, wherein the scale pressing defects are quality defects which are not Chang Pu times in the hot rolled strip steel product and have great influence on the use of downstream users. The thickness of the scale is 12-16 μm under the common condition, and the thickness of the scale at the black spots of the side plates can reach 20 μm. For serious iron oxide scale defects, the subsequent pickling treatment is difficult to completely remove, and the residual iron oxide scale defects still remain even after cold rolling, so that deep processing production such as stamping, coating and the like in the downstream working procedures are affected. In view of this, how to coordinate the rolling and cooling control process and the control process of the scale morphology 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 scale on a cold-rolled base material after rolling, which changes the scale components on the surface of the cold-rolled base material after rolling by adjusting a hot rolling process, thereby achieving the purposes of reducing the scale generation amount and improving the pickling efficiency.
In order to achieve the above purpose, the technical scheme adopted by the invention is as follows:
a method for controlling scale of a cold rolled base stock after rolling, comprising the steps of: heating and heat preservation, descaling after the furnace, rough rolling and descaling, rough rolling, intermediate billet descaling, finish rolling and 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-section cooling mode is adopted, so that the method specifically comprises the following steps: the front three rows of bottom water nozzles are closed, and a sparse cooling mode of closing the bottom water nozzles from the third row to the front two thirds of rows is adopted; the bottom water nozzles of the third row adopt a centralized cooling mode that all water nozzles are opened except the last three rows, and the last three rows of water nozzles are closed; wherein the sparse cooling mode cools 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; the concentrated cooling mode is used for cooling at a cooling speed of 40-50 ℃/s, the laminar cooling water pressure is controlled at 6.8-7.2 bar, and the hot rolled strip steel is cooled to 560-600 ℃ and then enters a coiling step.
According to the method for controlling the scale of the cold rolled base stock after rolling, the intermediate billet descaling step is provided with the descaling device, the descaling device is arranged between the flying shears and the descaling box in front of the finish rolling frame, 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.
According to the method for controlling the scale of the cold rolled base material after rolling, each scale breaking water nozzle is provided with a special-shaped nozzle, the special-shaped nozzle is jujube-pit-shaped, and the inclination angle of the special-shaped nozzle relative to the horizontal plane B is 12-15 degrees.
According to the method for controlling the rolled cold rolling base material iron scale, the bottom water nozzles in the laminar cooling step are arranged on the water nozzle racks in rows, each six rows of bottom water nozzles are cooling units, the bottom water nozzles in adjacent rows in each cooling unit are distributed in a staggered manner, each row of bottom water nozzles in each cooling unit are sequentially displaced in the same direction for a certain distance, the sequential displacement directions of the bottom water nozzles in each row in the adjacent cooling units are opposite, and the displacement distances are the same.
According to the method for controlling the rolled cold rolling base material iron scale, the nearest distance between the bottom water spray nozzles 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 the adjacent rows in the same cooling unit is L, and the L is 10-17 mm.
According to the method for controlling the scale of the cold rolled base material after rolling, the scale breaking device further comprises a first hot metal detector and a second hot metal detector, wherein the first hot metal detector is positioned in front of the flying shears, and the second hot metal detector is positioned 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 of the intermediate billet in the scale breaking step is 1.2-1.5 MPa.
In the method for controlling the scale of the cold rolled base material after rolling, in the rough rolling descaling step, all rolling passes are started for descaling by high-pressure water, and the outlet temperature of rough rolling is 1000-1030 ℃.
In the heating and heat preserving step, the billet heating temperature 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 heat equalizing section is controlled to be 0.4-0.6, and the furnace pressure is controlled to be 11-13 Pa.
The method for controlling the scale of the cold rolled base material after rolling is characterized in that the temperature of a finish rolling inlet is controlled to be 940-1000 ℃, the finish rolling speed is controlled to be 630-660 m/min, and the temperature range of a finish rolling outlet is 890-920 ℃.
Compared with the prior art, the method has the main advantages that: 1. laminar cooling adopts a sectional cooling mode of sparse front section and concentrated rear section, and sparse cooling is adopted for the front sectionBut controls the size of ferrite grains, improves the toughness and the stamping forming performance of the hot-rolled cold-rolled base material, and simultaneously generates single FeO; the three-time iron oxide scale FeO structural transformation is controlled by rapid cooling at the later stage, the iron oxide scale generation amount in the cooling process is reduced, and the transformation of the primary eutectoid or eutectoid reaction into alpha-Fe and Fe in the coiling process is inhibited 3 O 4 The mixture of the two layers forms 'four times of iron scales' with different structures, thereby ensuring the consistency of the components of the iron scales. 2. The descaling device is used for descaling a rough rolling intermediate billet, the scale is broken through the descaling device, the scale is subjected to strong blasting and impact through the descaling device, cracks are formed on the surface of the oxide layer, and then high-pressure water enters the interface between the oxide layer and the billet matrix through the cracks in the finish rolling high-pressure water descaling process, so that the secondary scale on the surface of the billet is effectively removed, and the surface quality of the intermediate billet is improved. 3. The method improves the setting mode of the existing laminar flow cooling bottom water nozzle, ensures that the whole width direction of the lower surface of the strip steel is uniformly and effectively cooled, greatly improves the transverse cooling uniformity of the surface of the strip steel, avoids the color difference of the surface of a product caused by watermark due to uneven temperature, and ensures the transverse distribution uniformity of iron oxide scales generated in the laminar flow cooling process. 4. The outlet temperature range of rough rolling is controlled, the traditional odd-pass descaling is improved to 5 rolling passes, high-pressure water descaling is started, the descaling effect is enhanced after even-pass descaling is increased, the generation of pressed-in iron oxide scale defects in the rolling process is avoided, and the surface quality of a rough rolling intermediate billet is further improved. 5. The heating temperature range is controlled, the oxidizing atmosphere in the furnace is gradually reduced, 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. On the premise of lower temperature before slab heat preservation, the generation amount of the iron oxide scale is reduced, and meanwhile, the main component of the generated iron oxide scale is FeO which is easy to clean. The method of the invention is adopted to check that the surface of the finished strip steel is clean and smooth, no iron oxide scale defect is generated, and the thickness of the iron oxide scale detected by the method is only 6-8 mu m, which is reduced by 50% compared with the traditional method. Tracking client acid washing, and improving the acid washing speed to 180m/min for pickling the board surfaceThe cleaning is smooth, the problem of unclean pickling is avoided, and the use requirement of a user is completely met.
Drawings
FIG. 1 is a schematic view of a bottom nozzle arrangement in a laminar cooling step (two cooling units are shown in the figure);
FIG. 2 is a schematic view of the scale breaking device in its installed position;
FIG. 3 is a D-view of FIG. 2 (not to scale);
FIG. 4 is a side view (not to scale) of FIG. 2;
fig. 5 is a view (not to scale) in the direction C of fig. 4.
The list of the reference numerals in the drawings is: 1. the 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 blank, 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 stock 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 0.15 percent of Mn, less than or equal to 0.3 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 0.008 percent of Ti, less than or equal to 0.02 percent of Ti, and the balance of Fe and unavoidable impurities (Cr, cu, sn, V, mo, nb). The method of the invention comprises the following steps: heating and preserving heat, descaling after the furnace, rough rolling and descaling, rough rolling, intermediate billet descaling, finish rolling and descaling, finish rolling, laminar cooling and coiling.
The heating and heat preserving step is to set the heating temperature range to 1240-1250 deg.c, gradually reduce the oxidizing atmosphere inside the furnace, control the air-fuel ratio of the first section to 0.8-1.0, control the air-fuel ratio of the second section to 0.6-0.8, control the air-coal ratio of the heat equalizing section to 0.4-0.6 and control the furnace pressure to 11-13 Pa. On the premise of lower temperature before slab heat preservation, the method reduces the generation amount of iron oxide scale, enhances the oxidizing atmosphere to fully burn the medium, improves the burning efficiency, simultaneously promotes the main component of the generated iron oxide scale to be FeO easy to remove, and in the heating and heat preservation process, the higher the temperature is, the oxidation generated in unit timeThe more the iron scale amount. With the increase of the heating temperature of the steel billet, the diffusion of various components is accelerated, the balance constant of the chemical reaction of the furnace gas and the steel is also changed, and conditions are created for accelerating the oxidation, so that the oxidation of the steel is aggravated. The heating temperature and the oxidation burning loss of the steel billet are in an exponential relation, and the rate of the increase is very rapid. Therefore, the oxidizing 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 reduced 3 O 4 The production amount of the steel is improved, and the descaling effect after the furnace is improved.
The rough rolling descaling step improves rough rolling descaling passes, improves traditional odd-pass descaling into 5 rolling passes, starts high-pressure water descaling, increases even-pass descaling, enhances descaling effect, avoids generation of pressed oxide scale defects in the rolling process, and further improves surface quality of rough rolling intermediate billets.
The invention adds the step of intermediate billet scale breaking, and aims to solve the problem of iron scale pressing in caused by incomplete intermediate billet iron scale removal. Referring to fig. 2 to 5, a scale breaking device is installed between the flying shears 10 and the scale removal box 14 for finish rolling scale removal in front of the finish rolling frame. 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 scale removing box to remove scales. Cracks generated by the impact of the high-pressure water on the surface of the oxide layer enter the interface of the oxide layer and the billet matrix, so that the secondary oxide scale on the surface of the billet is effectively removed. The surface quality of the intermediate blank is improved, so that the press-in defect of the oxide scale is effectively controlled, and the surface quality of the strip steel is 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 the scale breaking water nozzles and the intermediate billet is 70-75 degrees. The scale breaking water nozzles are provided with special-shaped nozzles 13-1, the special-shaped nozzles are jujube pit-shaped, and the inclination angle B of the special-shaped nozzles relative to the horizontal plane is 12-15 degrees, so that 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 intermediate blank, and water flow sprayed by the special-shaped nozzle is distributed in a fan shape and covers the whole surface of the intermediate blank. The pressure of the broken 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, wherein the first hot metal detector is positioned in front of the flying shears, and the second hot metal detector is positioned between the flying shears and the water collecting pipe. The two hot metal detectors are arranged because the first metal detector and the flying shears are linked, namely the strip steel signals are detected, and the strip steel is proved to come through, so that the circuit is closed; the second metal detector is turned on and water spraying is started. When the first and second hot metal detectors detect the intermediate billet signals, an electromagnetic valve connected with a water collecting pipe is powered on, and a scale breaking water nozzle starts to spray water flow to blast and impact the scale of the intermediate billet; when the strip steel is rolled to an F7 finishing mill (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 improvement of the invention, and the laminar cooling adopts a sectional cooling mode with sparse front section and concentrated rear section. The laminar cooling step is provided with a plurality of rows of bottom water spray nozzles, and the specific operation is as follows: the bottom water nozzles of the first three rows are closed, and the bottom water nozzles from the third row to the first two thirds (rounded) row adopt a sparse cooling mode of closing by separating rows; the bottom water nozzles in the last third row (rounding) adopt a centralized cooling mode that all water nozzles are opened except the last three rows, and the last three rows of water nozzles are closed; wherein the sparse cooling mode cools 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; the concentrated cooling mode is to cool at a cooling speed of 40-50 ℃/s, the laminar cooling water pressure is controlled at 6.8-7.2 bar, the hot rolled strip steel is cooled to 560-600 ℃, then the hot rolled strip steel enters a coiling step, and finally the hot rolled strip steel is cooled to room temperature through air cooling for 10 hours. The size of ferrite grains is controlled by sparse cooling in the front section, so that the toughness and the stamping forming performance of the hot-rolled and cold-rolled base stock are improved, and single FeO is generated. The three-time iron oxide scale FeO structural transformation is controlled by rapid cooling at the later stage, the iron oxide scale generation amount in the cooling process is reduced, and the transformation of alpha-Fe and Fe generated by the prior eutectoid or eutectoid reaction in the coiling process is inhibited 3 O 4 The mixture of the two layers forms 'four times of iron scales' with different structures, thereby ensuring the consistency of the components of the iron scales. In the process of low-oxide scale productionUnder the optimized characteristic action of high consistency of the components of the iron scale, the efficiency of the subsequent pickling process is improved, and the surface quality of the downstream cold-rolled product is ensured. The purpose of closing the front three rows of bottom water nozzles is as follows: firstly, the crystal grain has a growing process, so that fine grains are avoided; secondly, the influence of the cooling water backflow on the checking precision of the instrument is avoided. The purpose of closing the three rows of bottom water nozzles is as follows: the cooling water is prevented from flowing into the coiling machine, so that the uneven performance of the steel strip is caused.
Referring to fig. 1, laminar cooling bottom water nozzles 5 are installed in rows on respective water nozzle holders 4, and a cooling water tower 1 communicates with a plurality of bottom water nozzles 5 via 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 are sequentially displaced in the same direction for a certain distance, the sequentially displaced directions of the bottom water spray nozzles of each row in each adjacent cooling unit are opposite, and the displacement distances are the same. The nearest distance between the bottom water nozzle at the end of each cooling unit and the strip steel guard plate 3 is 25-40 mm, the farthest distance is 90-102 mm, and the displacement of the bottom water nozzles in the adjacent rows in the same cooling unit is L, wherein L is 10-17 mm. The laminar flow cooling bottom nozzles are arranged in 168 rows, and the structural arrangement of the first cooling unit 6 and the second cooling unit 7 is shown in fig. 1, and the other cooling units are arranged in the arrangement order shown in fig. 1. The invention improves the traditional design of centering alignment of bottom water nozzles into dislocation arrangement, and after improvement, in the laminar cooling process, 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 watermark due to uneven temperature is avoided, the transverse distribution uniformity of iron oxide scales generated in the laminar cooling process is ensured, and the effect of reducing the iron oxide scales at the edge of the strip steel is obvious.
Examples are provided below:
the chemical components of the hot-rolled cold-rolled base molten steel are as follows: 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 0.15 percent of Mn, less than or equal to 0.3 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 0.008 percent of Ti, less than or equal to 0.02 percent of Ti, and the balance of Fe and unavoidable impurities (Cr, cu, sn, V, mo, nb).
Casting into 10200mm x 1010mm x 200mm continuous casting blanks of 10200mm x 920mm x 200 mm. Heating and preserving heat in a heating furnace, wherein the soaking temperature is 1240-1250 ℃, after descaling with 20MPa high-pressure water after the furnace, conveying the steel sheet to a roughing mill for five passes, and starting 20MPa high-pressure water for descaling in each pass; the thickness of the intermediate blank was 38mm. The steel is sent to finish rolling through an intermediate roller way, the steel is broken by 1.2Mpa broken water before flying shears, then is rolled through seven finishing mill groups, the inlet temperature is controlled to be 940-1000 ℃, the finishing mill 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 bottom water nozzles 168 rows altogether, closing the first three rows and the last three rows, opening the fourth row to the 112 th row water nozzle at intervals, and cooling to 780-820 ℃ at a cooling speed of 20-30 ℃/s; and cooling the 113 th to 165 th rows to 560-600 ℃ at a cooling speed of 40-50 ℃/s for coiling. Finally cooling to room temperature by air cooling for 10 hours. The surface of the finished strip steel is clean and smooth, no iron scale defect is generated, the thickness of the iron scale is only 6-8 mu m after detection, the pickling speed of customers is tracked, the pickling speed can be increased to 180m/min, the surface of the pickling plate is smooth and clean, the problem of acid cleaning failure is avoided, and the use requirement of users is completely met.
The detailed technological parameters are shown in Table 1, the surface quality tracking conditions are shown in Table 2, and the mechanical properties are shown in Table 3.
TABLE 1 Process parameter control Condition
Table 2 surface quality tracking conditions
TABLE 3 mechanical statistics
| Sequence number | Yield strength (MPa) | Tensile strength (MPa) | Elongation (%) | Yield ratio | Cold bending property |
| 1 | 254 | 334 | 49 | 0.7 | Good quality |
| 2 | 260 | 338 | 50.5 | 0.75 | Good quality |
| 3 | 256 | 333 | 49 | 0.74 | Good quality |
| 4 | 239 | 322 | 49 | 0.78 | Good quality |
| 5 | 265 | 331 | 49.5 | 0.75 | Good quality |
| 6 | 255 | 334 | 52 | 0.72 | Good quality |
| 7 | 259 | 342 | 51 | 0.76 | Good quality |
| 8 | 265 | 347 | 50 | 0.78 | Good quality |
Claims (9)
1. A method for controlling the scale of a cold rolling base stock after rolling is characterized by comprising the following steps: the method comprises the following steps: heating and heat preservation, descaling after the furnace, rough rolling and descaling, rough rolling, intermediate billet descaling, finish rolling and 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-section cooling mode is adopted, so that the method specifically comprises the following steps: the front three rows of bottom water nozzles are closed, and a sparse cooling mode of closing the bottom water nozzles from the third row to the front two thirds of rows is adopted; the bottom water nozzles of the third row adopt a centralized cooling mode that all water nozzles are opened except the last three rows, and the last three rows of water nozzles are closed; wherein the sparse cooling mode cools 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; the concentrated cooling mode is used for cooling at a cooling speed of 40-50 ℃/s, the laminar cooling water pressure is controlled at 6.8-7.2 bar, and the hot rolled strip steel is cooled to 560-600 ℃ and then enters a coiling step;
the bottom water nozzles in the laminar cooling step are arranged on the water nozzle racks in rows, each six rows of bottom water nozzles are cooling units, the bottom water nozzles in adjacent rows in each cooling unit are distributed in a staggered mode, each row of bottom water nozzles in each cooling unit are sequentially displaced in the same direction for a certain distance, the sequentially displaced directions of the bottom water nozzles in each row in the adjacent cooling units are opposite, and the displaced distances are the same.
2. The method of controlling rolled cold rolled base stock scale according to claim 1, wherein: the intermediate billet descaling step is provided with a descaling device, the descaling device is arranged between the flying shears and the descaling box in front of the finish rolling frame, 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 of controlling rolled cold rolled base stock scale according to claim 2, wherein: each scale breaking water nozzle is provided with a special-shaped nozzle, the special-shaped nozzle is jujube-pit-shaped, and the inclination angle B of the special-shaped nozzle relative to the horizontal plane is 12-15 degrees.
4. A method of controlling rolled cold rolled base iron scale according to claim 3, wherein: the shortest distance between the bottom water 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 nozzles in the adjacent rows in the same cooling unit is L, and the L is 10-17 mm.
5. The method for controlling scale of a cold rolled base stock according to claim 4, wherein: the scale breaking device further comprises a first hot metal detector and a second hot metal detector, wherein the first hot metal detector is positioned in front of the flying shears, and the second hot metal detector is positioned between the flying shears and the water collecting pipe.
6. The method for controlling scale of a cold rolled base stock according to claim 5, wherein: the pressure of the water for breaking the intermediate billet into scales is 1.2-1.5 MPa.
7. The method for controlling scale of a cold rolled base stock according to claim 6, wherein: in the rough rolling descaling step, all rolling passes are started to remove the scale by high-pressure water, and the outlet temperature of rough rolling is 1000-1030 ℃.
8. The method of controlling rolled cold rolled base iron scale according to claim 7, wherein: in the heating and heat preserving step, the billet heating temperature 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.
9. The method of controlling rolled cold rolled base iron scale according to claim 8, wherein: the temperature of the finish rolling inlet is controlled to be 940-1000 ℃, the finish rolling speed is controlled to be 630-660 m/min, and the temperature range of the finish rolling outlet is 890-920 ℃.
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