CN113351644A - Method for reducing occurrence rate of corrosion on surface of pickled plate - Google Patents
Method for reducing occurrence rate of corrosion on surface of pickled plate Download PDFInfo
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- CN113351644A CN113351644A CN202110602019.3A CN202110602019A CN113351644A CN 113351644 A CN113351644 A CN 113351644A CN 202110602019 A CN202110602019 A CN 202110602019A CN 113351644 A CN113351644 A CN 113351644A
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- 238000005096 rolling process Methods 0.000 claims abstract description 46
- 239000008237 rinsing water Substances 0.000 claims abstract description 33
- 238000010438 heat treatment Methods 0.000 claims abstract description 17
- 238000001816 cooling Methods 0.000 claims abstract description 8
- 238000005266 casting Methods 0.000 claims abstract description 6
- 238000005098 hot rolling Methods 0.000 claims abstract description 5
- 239000002253 acid Substances 0.000 claims description 29
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 claims description 19
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Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
- B21B1/22—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling plates, strips, bands or sheets of indefinite length
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D7/00—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials
- B05D7/14—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials to metal, e.g. car bodies
-
- 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
- B21B45/004—Heating the product
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
- C23G1/00—Cleaning or pickling metallic material with solutions or molten salts
- C23G1/02—Cleaning or pickling metallic material with solutions or molten salts with acid solutions
- C23G1/08—Iron or steel
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F26—DRYING
- F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
- F26B21/00—Arrangements or duct systems, e.g. in combination with pallet boxes, for supplying and controlling air or gases for drying solid materials or objects
- F26B21/001—Drying-air generating units, e.g. movable, independent of drying enclosure
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F26—DRYING
- F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
- F26B21/00—Arrangements or duct systems, e.g. in combination with pallet boxes, for supplying and controlling air or gases for drying solid materials or objects
- F26B21/004—Nozzle assemblies; Air knives; Air distributors; Blow boxes
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F26—DRYING
- F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
- F26B5/00—Drying solid materials or objects by processes not involving the application of heat
- F26B5/14—Drying solid materials or objects by processes not involving the application of heat by applying pressure, e.g. wringing; by brushing; by wiping
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
- B21B1/22—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling plates, strips, bands or sheets of indefinite length
- B21B2001/225—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling plates, strips, bands or sheets of indefinite length by hot-rolling
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- General Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Wood Science & Technology (AREA)
- Health & Medical Sciences (AREA)
- Molecular Biology (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Materials Engineering (AREA)
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- Organic Chemistry (AREA)
- Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)
Abstract
The embodiment of the invention discloses a method for reducing the occurrence rate of corrosion on the surface of a pickled plate, which comprises the following steps: heating a casting blank before rolling, rough rolling, finish rolling, cooling after rolling and coiling in sequence to obtain a hot rolled coil; will the hot rolling is rolled up and is leveled, pickling, sweeps, stoving and fat liquoring, obtains the pickling board of no surface corrosion, wherein, the pickling includes pickling section and rinsing section, the rinsing section adopts many times of rinsing, and the used rinsing water of rinsing all satisfies following condition at every turn:the volume is more than or equal to 4.0m3The temperature is 65-75 ℃, and the pH value of rinsing water used in the last rinsing is more than or equal to 5.5. The invention ensures the rinsing effect of the pickled strip steel by controlling the rinsing conditions, thereby effectively avoiding the surface intergranular oxidation region from being damaged and greatly reducing the occurrence rate of corrosion on the surface of the pickling plate.
Description
Technical Field
The embodiment of the invention relates to the technical field of ferrous metallurgy, in particular to a method for reducing the occurrence rate of corrosion on the surface of a pickled plate.
Background
The acid washing is a process for removing the iron oxide scale on the surface of the metal by a chemical method, and is also called chemical acid washing. The hot rolled steel coil is rolled and coiled at high temperature, and iron oxide scales generated on the surface of the strip steel under the condition can firmly cover the surface of the strip steel and cover the quality defects on the surface of the strip steel. If the strip steel with the iron oxide scale is directly sent to a cold rolling mill for rolling, firstly, the strip steel is rolled under the condition of large rolling reduction, the iron oxide scale is pressed on a matrix of the strip steel, the surface quality inspection and the processing performance of a cold-rolled sheet are influenced, and even waste products are caused; secondly, after the iron scale is crushed, the crushed iron scale enters an emulsion system of a cooling and lubricating roller, so that circulating equipment is damaged, and the service life of the emulsion is shortened; third, it can damage cold rolls that have very low surface roughness and are expensive. Therefore, prior to cold rolling, the surface scale of the strip must be removed, and the defective portion of the strip must be cut off, which is usually done by a pickling line.
With the increasingly prominent advantage of 'hot band cooling' in the rolling industry, the application range of the pickled plates is more and more extensive, customers are all over the country, and in the steel coil storage and transportation process, due to the differences of transportation modes, transportation periods, storage environments, storage periods and the like, the corrosion resistance of the sold pickled steel coils in the prior art is different, so that the quality defect of corrosion is easily caused, the use of the customers is seriously influenced, and the corrosion quality objection is caused. Strip steel corrosion defect quality objections and quality complaints after pickling in 2018 are as high as 60, which causes huge cost loss and seriously affects the image of a company.
Therefore, how to develop a method for reducing the occurrence rate of corrosion on the surface of the pickled plate is a technical problem to be solved urgently.
Disclosure of Invention
The embodiment of the invention aims to provide a method for reducing the occurrence rate of corrosion on the surface of a pickled plate, so that the occurrence rate of corrosion on the surface of the pickled plate is greatly reduced.
In order to achieve the above object, an embodiment of the present invention provides a method for reducing occurrence rate of corrosion on a surface of an acid-pickled plate, including:
heating a casting blank before rolling, rough rolling, finish rolling, cooling after rolling and coiling in sequence to obtain a hot rolled coil;
will the hot rolling is rolled up and is leveled, pickling, sweeps, stoving and fat liquoring, obtains the pickling board of no surface corrosion, wherein, the pickling includes pickling section and rinsing section, the rinsing section adopts many times of rinsing, and the used rinsing water of rinsing all satisfies following condition at every turn: the volume is more than or equal to 4.0m3The temperature is 65-75 ℃, and the pH value of rinsing water used in the last rinsing is more than or equal to 5.5.
Furthermore, the rinsing section is provided with a squeezing roller, and the working pressure of the squeezing roller is controlled to be 0.5-0.6 MPa.
Further, the air purging direction in purging is 42-47 degrees with the horizontally moving strip steel.
Further, the drying temperature is more than or equal to 90 ℃.
Further, the oil coating amount in the oil coating is 700-1500mg/m2。
Furthermore, the pickling plate without surface corrosion is packaged by adopting an antirust film for rust prevention, and drying agents are respectively adhered to two sides of the pickling plate without surface corrosion.
Further, the temperature of heating before rolling is 1200-1260 ℃, and the time of heating before rolling is 200-280 mim.
Further, the flattening rolling force in flattening is 200-350 t.
Further, in the pickling section, a pickling tank is adopted to carry out pickling at the speed of 150-250 m/min, the temperature of acid in the pickling tank is controlled at 75-90 ℃, and the concentration of the acid is 45-30 g/L.
Further, the finish rolling temperature of the finish rolling is 800-880 ℃, and the coiling temperature is 500-650 ℃.
One or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:
the embodiment of the invention provides a method for reducing the occurrence rate of corrosion on the surface of a pickled plate, which comprises the following steps: heating a casting blank before rolling, rough rolling, finish rolling, cooling after rolling and coiling in sequence to obtain a hot rolled coil; will the hot rolling is rolled up and is leveled, pickling, sweeps, stoving and fat liquoring, obtains the pickling board of no surface corrosion, wherein, the pickling includes pickling section and rinsing section, the rinsing section adopts many times of rinsing, and the used rinsing water of rinsing all satisfies following condition at every turn: the volume is more than or equal to 4.0m3The temperature is 65-75 ℃, and the pH value of rinsing water used in the last rinsing is more than or equal to 5.5; the invention ensures the rinsing effect of the pickled strip steel by controlling the rinsing conditions, thereby effectively avoiding the surface intergranular oxidation region from being damaged and greatly reducing the occurrence rate of corrosion on the surface of the pickling plate.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
FIG. 1 is a flow chart of a method for reducing the occurrence of corrosion on the surface of a pickled plate according to an embodiment of the present invention;
FIG. 2 is a prior art corrosion defect picture, wherein FIG. 2(a) is the CL of the steel strip surface after pickling-Rust defects caused by residue, FIG. 2(b) is rust caused by oil leakageDefects, wherein fig. 2(c) shows corrosion defects caused by oil leakage of the equipment, and fig. 2(d) shows corrosion defects caused by water inflow of the package;
FIG. 3 is a diagram of the reduction of surface corrosion on the pickled plate surface according to example 1 of the present invention.
Detailed Description
The embodiments of the present invention will be described in detail below with reference to specific embodiments and examples, and the advantages and various effects of the embodiments of the present invention will be more clearly apparent therefrom. It will be understood by those skilled in the art that the present embodiments and examples are illustrative of the present invention and are not to be construed as limiting the present invention.
Throughout the specification, unless otherwise specifically noted, terms used herein should be understood as having meanings as commonly used in the art. Accordingly, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which embodiments of the invention belong. If there is a conflict, the present specification will control.
Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment and the like used in the examples of the present invention are commercially available or can be prepared by an existing method.
In order to solve the technical problems, the embodiment of the invention provides the following general ideas:
according to an exemplary embodiment of the present invention, there is provided a method for reducing the occurrence of rust on the surface of pickled plates, as shown in fig. 1, comprising:
s1, sequentially heating the casting blank before rolling, roughly rolling, finely rolling, cooling after rolling and coiling to obtain a hot rolled coil;
s2, will the hot-rolled coil is carried out levelly and smoothly, the pickling, is swept, is dried and is fat liquored, obtains the pickling board that does not have surface corrosion, wherein, the pickling includes pickling section and rinsing section, the rinsing section adopts many times of rinses, and the used rinsing water of rinsing all satisfies the following condition at every turn: the volume is more than or equal to 4.0m3The temperature is 65-75 ℃, and the pH value of rinsing water used in the last rinsing is more than or equal to 5.5.
From the above, it can be seen that the general idea of the method for reducing the occurrence rate of corrosion on the surface of the pickled plate provided by the embodiment of the invention is as follows:
the appearance characteristics of the corrosion defects on the surface of the pickled strip steel are combined, the generation reasons of the corrosion defects are analyzed, and the influence of the rinsing process on the corrosion on the surface of the pickled plate is found by combing the point positions of the corrosion defects possibly caused by the pickling line one by one:
acid liquor residue exists on the surface of the hot rolled plate after acid washing, acid liquor is remained after the hot rolled plate is squeezed by a squeezing roller at the outlet of an acid tank to form an acid liquor film, and free acid in the acid liquor film can chemically react with the surface of the strip steel if the hot rolled plate is not rinsed and dried, so that the surface of the strip steel is corroded to generate corrosion defects, and the formulation and optimization of a rinsing process are very important.
The standard for judging the quality of the rinsing effect is the residual Cl on the surface of the strip steel-Content of (C), and residual Cl on the surface of the strip-The content of (b) cannot be judged intuitively in time, so the pH value of the last rinsing water is used as an evaluation standard. Passing through a series of residual Cl on the surface of the strip steel-The comparison result of the content of the acid and the pH value of the final rinsing water ensures that the rinsing effect of the pickled strip steel can be ensured when the pH value of the final rinsing water is not lower than 5.5, thereby preventing the Cl on the surface of the strip steel-The rust quality caused by the residue is objected. The pH of the final rinsing water is lower than 5.5, and residual Cl on the surface of the strip steel exists-The corrosion defect is easily caused to be adversely affected due to excessive corrosion;
the amount of the rinsing water is closely related to the number of passes of the rinsing water, and the amount of the rinsing water is less if the number of passes of the rinsing water is more. At present, the pickling line mostly adopts five-stage countercurrent rinsing to respectively and independently rinse strip steel, and the consumption of rinsing water used in each rinsing is not less than 4.0m3H is used as the reference value. If it is less than 4.0m3The surface rinsing is insufficient, and the adverse effect of acid liquor residue is easy to occur;
the control of the rinsing temperature is another key index of the rinsing process, and the increase of the rinsing water temperature can reduce the viscosity of water and improve Cl-The diffusion capacity of ions in water enables the rinsing to be more effective, and meanwhile, the temperature of the strip steel can be increased, so that the drying of the strip steel after rinsing is facilitated. Through test comparison and rinsingWhen the temperature is increased to 65 ℃ or above, the rinsing effect can be improved; if the temperature of the rinsing water is lower than 65 ℃, the activity of the rinsing water is low, so that insufficient rinsing is easily caused; if the temperature of the rinsing water is higher than 75 ℃, the secondary heating phenomenon appears on the surface of the strip steel, which is easy to cause secondary chemical reaction and is not beneficial to the control of the surface quality of the strip steel;
in summary, the embodiment of the present invention controls: the rinsing water used for each rinsing satisfies the following conditions: the volume is more than or equal to 4.0m3The temperature is 65-75 ℃, the pH value of rinsing water used in the last rinsing is more than or equal to 5.5, so that the rinsing effect of the pickled strip steel is ensured, the surface intergranular oxidation area is effectively prevented from being damaged, and the surface corrosion incidence rate of the pickled plate is greatly reduced.
As an alternative embodiment, the application of the pre-rinsing mode can be used, which can reduce the content of residual acid in the rinsing area of the strip after pickling and can keep the strip wet, so that the application of the pre-rinsing mode is beneficial to the rinsing effect of the strip.
As an optional implementation mode, the inventor of the application finds that the guarantee of the drying effect can further reduce the occurrence rate of the corrosion defects of the strip steel. The drying system generally comprises a group of efficient squeezing rollers, a compressed air blowing system and a dryer with a heater, a circulating fan and a suction fan, and the working principle of the drying system is to blow and remove residual water stains on the surface of the strip steel by utilizing hot air. The drying effect is based on the standard that no water mark is visible on the surface of the strip steel, and the surface quality detector shows no water mark defect. The guarantee of belted steel surface stoving effect can be realized through the crowded dry effect of crowded dry roll, the state of purge system, the optimization of stoving technology, specifically:
(1) the rinsing section is provided with a squeezing roller, and the working pressure of the squeezing roller is controlled to be 0.5-0.6 Mpa. The wringing rollers are important components in the pickling line, all the wringing rollers are rubber covered rollers, the wringing effect of the wringing rollers in the rinsing section is influenced by the strip steel plate shape, the abrasion degree of the roller surface of the wringing rollers, the working pressure of the wringing rollers, the rubber material of the wringing rollers, the installation precision of the wringing rollers and the like, and particularly the roller surface state and the working pressure of the wringing rollers play a decisive role in the wringing effect. Therefore, the uniform pressure is required to be ensured on the two sides of the squeezing roller in the rinsing section, and the pressure is controlled to be between 0.5 and 0.6 MPa; meanwhile, the replacement period of the rinsing section wringing rollers is shortened, and particularly the last group of efficient wringing rollers need to be organized and replaced every time the final group of efficient wringing rollers are fixed and repaired. If the working pressure of the squeezing roller is less than 0.5Mpa, the pressure is small, the squeezing effect is deviated, and if the working pressure of the squeezing roller is more than 0.6Mpa, the equipment can not bear the pressure easily;
(2) a compressed air purging system in front of a dryer is mainly used for purging by utilizing high-pressure air to remove a thick water film on the surface of a strip steel. The state of the purging system is very critical, the purging air pipes are more arranged into two groups and are respectively purged in the positions on two sides of the strip steel inlet and outlet in an inclined mode, and the purging direction of air in purging and the strip steel moving horizontally are 42-47 degrees. Meanwhile, the nozzle is not blocked or leaked, so that a good purging effect is ensured. If the angle between the air purging direction and the horizontally moving strip steel is less than 42 degrees, the purging area is small, purging cannot be performed completely, and if the angle is more than 47 degrees, purging pressure is affected, and purging is insufficient;
(3) the dryer adopts a hot air drying system, and takes away the tiny moisture on the surface of the strip steel by utilizing hot air, thereby drying the plate surface. The drying temperature is a key process control point and is required to be not lower than 90 ℃, so that the drying effect of the pickled strip steel is ensured. If the drying temperature is lower than 90 ℃, the drying effect is not good;
as an alternative embodiment, the inventor of the application finds that the guarantee of the oiling effect can further reduce the occurrence rate of the corrosion defects of the strip steel. The electrostatic oiling technology is mostly adopted for oiling the pickled strip steel, and an electrostatic oiling machine is a key device for coating antirust oil on the surface of the strip steel in high quality so as to prevent the surface of the strip steel from being rusted. The device quickly atomizes the antirust oil liquid flowing out from the gap of the cutting edge of the knife beam by the action of a high-voltage electrostatic field and the influence of point discharge, and the antirust oil liquid is adsorbed on the surface of the strip steel to form a uniform and thin oil film, so that the aim of preventing the surface of the strip steel from being rusted is fulfilled, and the occurrence of a rust quality objection caused by oil leakage or uneven oil coating on the surface of the strip steel is avoided. The standard for testing the oiling effect is that the surface of the strip steel is free from missing coating visually, and simultaneously, the antirust oil sprayed by the upper and lower knife beams of the oiling machine is in a uniform rain curtain shape visually. The assurance of belted steel surface fat liquoring effect can be realized through fat liquoring volume precision, antirust oil quality inspection, oiling machine periodic maintenance, specifically:
(1) the accuracy of the oil coating amount is directly related to the anti-rust effect of the surface of the strip steel, in order to ensure the product quality of the strip steel, the oil coating amount is determined by steel types and customers according to the application, the production area, the use period, the acceptable range of the customers and the like of the product, and the oil coating amount is set to be 700-1500mg/m2And meanwhile, the metering pump of the oiling machine is periodically calibrated, and the deviation between the set oiling amount and the actual deviation is controlled within +/-15%. If the oiling amount in the oiling process is less than 700mg/m2The oiling amount is small, and the antirust effect is poor; if the oiling amount in the oiling process is more than 1500mg/m2The oil quantity is large, so that the oil removing difficulty of customers is easily caused, and the cost is increased;
(2) the anti-rust oil used by the electrostatic oiling technology requires good atomization performance and low moisture content, does not spark in the using process, and can ensure the safe and normal operation of the electrostatic oiling machine; meanwhile, the method requires less impurities and does not block an oil supply system and a jet knife beam; the viscosity is moderate, and a uniform oil film is formed on the surface of the strip steel. On the other hand, the rust-preventive oil is stored in the oil tank of the oiling machine in a circulating manner for a long time, and the rust-preventive oil is easy to deposit at the bottom of the oil tank along with the passage of time, so that the quality of the oil product cannot be ensured, and the inspection of the oil product of the rust-preventive oil is very important. The method requires regular detection of the oil product of the anti-rust oil and simultaneous detection of crude oil of the anti-rust oil and old oil discharged from a base material of an oil tank of the oiling machine, thereby ensuring the qualification of the oil product, wherein the qualification standards are that mechanical impurities are less than or equal to 0.02 percent and water is less than or equal to 0.05 percent.
(3) In order to ensure a good oiling effect, the oiling machine needs to be maintained regularly, and key cleaning and maintenance points comprise an upper knife beam and a lower knife beam of the oiling machine, the inner wall of a box body of the oiling machine, an insulation plate, an atomized steel wire, an oil tank of the oiling machine and the like.
As an alternative embodiment, the inventors of the present application have found that improving the packaging quality can further reduce the incidence of strip corrosion defects. The packaging quality of the pickled strip steel is very critical, particularly in summer, because of the fact that water vapor in the external environment is large and the accidental phenomenon that acid mist is not easy to disperse exists in a production factory, all commodity coils are completely packaged by adding the anti-rust films and the anti-rust paper, so that the steel coil is completely sealed, the phenomenon that the steel coil is corroded by the environment is avoided, and meanwhile, the occurrence of corrosion quality objections caused by packaging water inflow and the like in the transportation process of the strip steel is avoided. In summer, the offline temperature of the pickling plate is as high as 30-45 ℃, partial water still exists in the closed environment of the pickling plate packaged immediately after offline, the pickling plate is solidified after being verified by multiple tests and contrasts, and in summer each year, two drying agents are respectively adhered to two sides of the inner package of each pickling plate roll, so that the occurrence of corrosion quality objections caused by large water vapor is prevented.
As an alternative embodiment, the inventors of the present application found that the guarantee of the functional accuracy of the equipment can further reduce the occurrence rate of the corrosion defects of the strip steel, specifically:
in order to ensure the rust-proof effect of the pickling line after the strip steel is rinsed, the running state of key quality equipment in contact with the strip steel is required to be ensured, and the strip steel is ensured to be in a closed state after being pickled as much as possible, so that the influence of the external environment on the surface quality of the strip steel is reduced, and strip steel corrosion quality objections caused by abnormal conditions such as water leakage and equipment oil leakage are prevented.
The roll surfaces of a wringing roll, a pinch roll, a tension roll, a press roll and the like which are in contact with the surface of the pickled strip steel need to be in good states, and abnormal conditions such as degumming or adhesion of foreign matters and the like do not exist, so that the potential corrosion problem caused by uneven contact of the roll surfaces and the like is prevented.
And key quality equipment such as a drying roll, a pinch roll, a tension roll and the like is periodically and timely replaced by combining the service cycle of each roll surface, so that the good running state of the equipment is ensured.
As an optional implementation mode, the temperature of the heating before rolling is 1200-1260 ℃, and the time of the heating before rolling is 200-280 mim. The range can reduce the depth of an intercrystalline oxide layer on the surface layer of the strip steel, and if the heating temperature is too high, the heating time is too long, which is not beneficial to reducing the occurrence rate of corrosion on the surface of the pickling plate; if the heating temperature is lower than 1200 ℃, the heating time is shorter than 200mim, the slab rolling is not facilitated, and the risk of scrap steel is large;
in an optional embodiment, the finish rolling temperature of the finish rolling is 800 to 880 ℃. If the finish rolling temperature is higher than 880 ℃, the corrosion incidence rate of the surface of the pickled plate is not reduced; if the finishing temperature is lower than 800 ℃, the hot rolling performance control is not facilitated, and the use requirements of customers cannot be met;
in an alternative embodiment, the coiling temperature is 500 to 650 ℃. If the coiling temperature is higher than 650 ℃, the corrosion incidence rate on the surface of the pickled plate is not reduced; if the coiling temperature is lower than 500 ℃, the hot coiling performance control is not facilitated, and the use requirements of customers cannot be met;
in an optional embodiment, the temper rolling force is 200-350 t. If the flattening rolling force is more than 350t, the corrosion incidence rate of the surface of the pickled plate is not reduced; if the flattening rolling force is less than 200t, the hot coil shape control is not facilitated;
in an optional embodiment, in the acid washing section, acid washing is performed at a speed of 150-250 m/min by using an acid washing tank, the temperature of acid in the acid washing tank is controlled at 75-90 ℃, and the concentration of the acid is 45-30 g/L. The pickling effect is facilitated, when the pickling speed is too low, the soaking time of the strip steel in the pickling tank is too long, the over-pickling defect is caused, and when the pickling speed is too high, the pickling of the strip steel is insufficient, and the under-pickling defect is caused to be adversely affected; when the temperature of the acid is too low, the pickling effect is poor, the hidden danger of insufficient pickling exists, when the temperature of the acid is too high, the hidden danger of excessive pickling exists, and the phenomenon that the pressure born by equipment such as a squeezing roller in a pickling tank is too high is caused; the acid concentration is too low, and acid pickling is not performed; excessive acid concentration, over-pickling, acid liquor waste and the like;
the method for reducing the occurrence rate of rust on the surface of the pickled plate according to the present application will be described in detail with reference to examples, comparative examples and experimental data.
S1, sequentially heating the casting blank before rolling, roughly rolling, finely rolling, cooling after rolling and coiling to obtain a hot rolled coil;
s2, will the hot-rolled coil is carried out levelly and smoothly, the pickling, is swept, is dried and is fat liquored, obtains the pickling board that does not have surface corrosion, wherein, the pickling includes pickling section and rinsing section, the rinsing section adopts many times of rinses, and the used rinsing water of rinsing all satisfies the following condition at every turn: the volume is more than or equal to 4.0m3The temperature is 65-75 ℃, and the pH value of rinsing water used in the last rinsing is more than or equal to 5.5.
The process parameters in the comparative examples were different and are specifically shown in table 1. The conditions not listed in the table can be adopted by the common method in the prior art, and each set of experiments in the examples and the comparative examples comprises 10 samples, and 10 acid-washed plates are obtained respectively;
TABLE 1 Process parameters
Statistics are carried out on the occurrence rate of the rust on the surfaces of 10 pickled plates obtained from each group, and the results are shown in table 2.
TABLE 2
From the data in table 2, it can be seen that:
in comparative example 1, the volume of rinsing water was 3m3H is less than or equal to 4.0m of the embodiment of the invention3The range of the acid-washing plate/h and other process parameters are the same as those of the acid-washing plate in the embodiment 1, the surfaces of the 10 acid-washing plates are rusted, and the rusting occurrence rate reaches 100 percent.
In the comparative example 2, the temperature of rinsing water is 60 ℃ which is less than the range of 65-75 ℃ in the embodiment of the invention, other process parameters are the same as those in the embodiment 1, and the occurrence rate of corrosion reaches 100%;
in the comparative example 3, the temperature of rinsing water is 80 ℃, which is larger than the range of 65-75 ℃ in the embodiment of the invention, other process parameters are the same as those in the embodiment 1, and the occurrence rate of corrosion reaches 100%;
in the comparative example 4, the pH of the last rinsing water is 5, which is smaller than the range that the pH is more than or equal to 5.5 in the embodiment of the invention, other process parameters are the same as those in the embodiment 1, and the corrosion incidence rate reaches 100 percent;
the embodiment 1-the embodiment 3 have no corrosion problem, and the surface quality of the pickled plate is good; the embodiment of the invention is shown to meet the following conditions by controlling the rinsing water used in each rinsing:the volume is more than or equal to 4.0m3And the temperature is 65-75 ℃, and the pH value of rinsing water used in the last rinsing is more than or equal to 5.5 ", so that the rinsing effect of the pickled strip steel is ensured, the surface intergranular oxidation area is effectively prevented from being damaged, and the surface corrosion incidence of the pickled plate is greatly reduced.
In the embodiment 4, the working pressure of the drying roller is 0.4Mpa which is less than the range of 0.5-0.6Mpa in the embodiment of the invention, and the occurrence rate of corrosion reaches 50%;
in the embodiment 5, the working pressure of the drying roller is 0.4Mpa which is less than the range of 0.5-0.6Mpa in the embodiment of the invention, and the occurrence rate of corrosion reaches 60%;
in the embodiment 6, the included angle between the air purging direction and the strip steel is 20 degrees, which is smaller than the range of 42-47 degrees in the embodiment of the invention, and the occurrence rate of corrosion reaches 20 percent;
in the embodiment 7, the drying temperature is 80 ℃ which is less than the range of more than or equal to 90 ℃ in the embodiment of the invention, and the occurrence rate of corrosion reaches 40 percent;
in example 8, the amount of oil applied was 600mg/m2Less than 700 to 1500mg/m in the embodiment of the present invention2The corrosion incidence rate reaches 30 percent;
in example 9, the amount of oil applied was 2000mg/m2Is larger than 700 to 1500mg/m in the embodiment of the present invention2The corrosion incidence reaches 60%;
as can be seen from the above, the rinse process parameters in examples 4 to 9 are within the range of the examples of the present invention, and the corrosion occurrence rate is somewhat reduced as compared with comparative examples 1 to 4, but the corrosion occurrence rate is higher in examples 4 to 9 as compared with examples 1 to 4.
Description of the attached figures 2-3:
FIG. 2(a) shows Cl on the surface of the pickled steel strip-Rust defects caused by residues, wherein fig. 2(b) shows rust defects caused by oil leakage, fig. 2(c) shows rust defects caused by oil leakage, and fig. 2(d) shows rust defects caused by water inflow of the package; the rinsing process, the drying effect, the oiling effect and the packaging quality can influence the corrosion incidence rate of the surface of the acid-washing plate;
fig. 3 is a picture of reducing surface corrosion on a pickled plate surface according to embodiment 1 of the present invention, which shows that the method for reducing the occurrence rate of corrosion on a pickled plate surface according to the embodiment of the present invention can greatly reduce the occurrence rate of corrosion quality objections, and is simple to operate and easy to control.
Finally, it should also be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.
While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all such alterations and modifications as fall within the scope of the embodiments of the invention.
It will be apparent to those skilled in the art that various modifications and variations can be made in the embodiments of the present invention without departing from the spirit or scope of the embodiments of the invention. Thus, if such modifications and variations of the embodiments of the present invention fall within the scope of the claims of the embodiments of the present invention and their equivalents, the embodiments of the present invention are also intended to encompass such modifications and variations.
Claims (10)
1. A method of reducing the incidence of rust on the surface of pickled board, comprising:
heating a casting blank before rolling, rough rolling, finish rolling, cooling after rolling and coiling in sequence to obtain a hot rolled coil;
will the hot rolling is rolled up and is leveled, pickling, sweeps, stoving and fat liquoring, obtains the pickling board of no surface corrosion, wherein, the pickling includes pickling section and rinsing section, the rinsing section adopts many times of rinsing, and the used rinsing water of rinsing all satisfies following condition at every turn: the volume is more than or equal to 4.0m3The temperature is 65-75 ℃, and the pH value of rinsing water used in the last rinsing is more than or equal to 5.5.
2. The method for reducing the occurrence rate of corrosion on the surface of the pickled plate as claimed in claim 1, wherein the rinsing section is provided with a wringing roller, and the working pressure of the wringing roller is controlled to be 0.5-0.6 MPa.
3. The method of claim 1, wherein the air purge direction during said purging is 42-47 ° relative to the horizontally moving strip.
4. The method of claim 1, wherein the drying temperature is at least 90 ℃.
5. The method for reducing the occurrence rate of corrosion on the surface of the pickled plate as claimed in claim 1, wherein the oil coating amount in the oil coating is 700-1500mg/m2。
6. The method for reducing the occurrence rate of corrosion on the surface of the acid-pickled plate as claimed in claim 1, wherein the acid-pickled plate without surface corrosion is packaged by rust-proof film, and drying agents are respectively adhered to two sides of the acid-pickled plate without surface corrosion.
7. The method for reducing the occurrence rate of corrosion on the surface of the pickled plate as claimed in claim 1, wherein the temperature of heating before rolling is 1200-1260 ℃, and the time of heating before rolling is 200-280 mm.
8. The method for reducing the occurrence of corrosion on the surface of an acid-pickled plate according to claim 1, wherein the flattening rolling force in the flattening is 200 to 350 t.
9. The method for reducing the occurrence rate of corrosion on the surface of the pickled plate as claimed in claim 1, wherein in the pickling section, a pickling tank is used for pickling at a speed of 150-250 m/min, the temperature of acid in the pickling tank is controlled at 75-90 ℃, and the concentration of the acid is 45-30 g/L.
10. The method for reducing the occurrence rate of corrosion on the surface of the pickled plate as claimed in claim 1, wherein the finish rolling temperature of the finish rolling is 800 to 880 ℃, and the coiling temperature is 500 to 650 ℃.
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