CN114231822B - Method for improving surface coatability of cold-rolled automobile plate - Google Patents
Method for improving surface coatability of cold-rolled automobile plate Download PDFInfo
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- CN114231822B CN114231822B CN202111269247.XA CN202111269247A CN114231822B CN 114231822 B CN114231822 B CN 114231822B CN 202111269247 A CN202111269247 A CN 202111269247A CN 114231822 B CN114231822 B CN 114231822B
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C33/00—Making ferrous alloys
- C22C33/04—Making ferrous alloys by melting
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/26—Methods of annealing
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
- C21D8/0226—Hot rolling
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- 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
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
- C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
- C23C22/06—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6
- C23C22/07—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing phosphates
- C23C22/08—Orthophosphates
- C23C22/18—Orthophosphates containing manganese cations
- C23C22/182—Orthophosphates containing manganese cations containing also zinc cations
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- 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
- C23G1/081—Iron or steel solutions containing H2SO4
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- 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
- C23G1/088—Iron or steel solutions containing organic acids
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- 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
- C23G5/00—Cleaning or de-greasing metallic material by other methods; Apparatus for cleaning or de-greasing metallic material with organic solvents
- C23G5/06—Cleaning or de-greasing metallic material by other methods; Apparatus for cleaning or de-greasing metallic material with organic solvents using emulsions
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Abstract
The invention discloses a method for improving the coatability of the surface of a cold-rolled automobile plate, belonging to the field of surface treatment of metal materials. The method comprises the process flows of smelting and casting → hot rolling and coiling → acid pickling and cold rolling → continuous annealing → smooth oiling → oil removing and acid pickling → surface adjustment → phosphating treatment. The phosphating film layer on the surface of the cold-rolled automobile plate prepared by the method has the advantages of compact structure, uniform crystallization, granular shape, average grain size of 2-3 mu m, smaller porosity and higher coatability, and can effectively solve the problem of poorer coatability of the cold-rolled automobile plate improved by the existing method.
Description
Technical Field
The invention belongs to the field of metal material surface treatment, and particularly relates to a method for improving the coatability of the surface of a cold-rolled automobile plate.
Background
The automobile steel plate is phosphorized before coating, and aims to form a uniform and compact phosphorized film on the surface of the steel plate, so that the surface corrosion resistance is improved, and the adhesion of a primer is enhanced. Therefore, the coatability of the phosphated steel sheet is also an important measure of whether it can be widely used in automobiles. The phosphating reaction process of the surface of the automobile steel plate determines the phosphating film forming quality, and the uniform phosphating reaction not only requires that the substrate needs chemical components and uniform tissue structure distribution before coating, has no obvious element enrichment on the surface, high surface cleanliness, no pollution or defect and no corrosion, but also requires higher surface energy and a certain roughness value on the surface of the substrate, promotes the phosphating nucleation reaction, reduces the nucleation potential barrier, and also requires strict control of the components of a phosphating solution and film forming conditions.
CN105420607A of 3 months and 23 days in 2016 discloses a control method for improving the coating performance and surface quality of a cold-rolled automobile plate, which improves the coating performance of the cold-rolled automobile plate by controlling the element distribution condition, oxidation state, surface roughness and the like of the cold-rolled automobile plate. CN111647733A of 9-11.2020 discloses a method for improving the phosphating performance of a low-carbon aluminum killed steel automobile plate and the automobile plate.
The method ignores the influence of the residues of the substrate before coating, the cleaning difficulty of the antirust oil, the surface activity of the substrate, the components of the phosphating solution and the film forming conditions on the phosphating film forming quality. Therefore, there is a need to develop a new method for improving the coatability of cold-rolled automobile sheet surfaces.
Disclosure of Invention
The invention aims to solve the technical problem that the coating performance of the cold-rolled automobile sheet is poor by the conventional method.
The technical scheme adopted by the invention for solving the technical problems is as follows: the method for improving the coatable performance of the surface of the cold-rolled automobile plate comprises the process flows of smelting and casting → hot rolling and coiling → acid pickling and cold rolling → continuous annealing → smooth oiling → oil removing and acid pickling → surface adjustment → phosphating treatment.
In the smelting and casting process, the alloy is smelted and cast into a casting blank according to chemical components, wherein the chemical components comprise, by mass, not more than 0.25% of C, not more than 0.30% of Si, not less than 0.05% or not more than 3% of Mn, not more than 0.01% of P, not more than 0.01% of S, not more than 0.02% of Al, not more than 0.01% of N, not more than 0.02% of As + Sn, and the balance of Fe and inevitable impurities.
In the hot rolling and coiling procedure, the casting blank is heated to 1150-1300 ℃ and is kept warm for 2-4h and then is rolled, and the final rolling temperature is more than or equal to 850 ℃; and coiling after rolling at the coiling temperature of 400-600 ℃ to obtain the hot rolled coil.
In the pickling and cold rolling process, the pickling speed is 80-120m/min, the cold rolling reduction is 40-60%, the saponification value of the emulsion is 100-200mgKOH/g, and the temperature of the emulsion is 50-70 ℃ to obtain the cold-hard strip steel.
Further, the saponification value of the emulsion is 150-180mgKOH/g, the temperature of the emulsion is 55-60 ℃, and the content of the miscellaneous oil in the emulsion is less than or equal to 3 percent; the corrosion inhibitor in the emulsion is at least one of urotropine, thiourea and thiourea-aluminum sulfate in the acid washing solution, and the mass fraction is 0.5-1.5%.
Furthermore, the total amount of the residues (residual oil and residual iron) on the surface of the cold-hard strip steel after cold rolling is less than or equal to 200mg/m2The surface reflectivity is more than or equal to 80 percent.
In the continuous annealing process, heating to 800-930 ℃ at the speed of 10-20 ℃/s, preserving heat for 30-200s, cooling to 350-450 ℃ at the speed of 50-100 ℃/s, and then air-cooling to room temperature to obtain an annealed steel plate; atmosphere of annealing furnace is N2-H2Mixed gas of (2), wherein H2The content is 0.5-20%, and the dew point temperature of the annealing atmosphere is-40-10 ℃.
Furthermore, the average grain size of the annealed steel plate is 8-10 μm, and the thickness of the oxide film layer is less than or equal to 3 μm.
In the leveling oiling procedure, the surface roughness Ra value of the leveled strip steel is controlled to be 0.7-1.3 mu m, and the Rpc value is controlled to be 80-130; the oiling adopts a spraying mode, the spraying temperature is 30-50 ℃, and the oil coating amount on the surface of the strip steel is 600-1000mg/m2。
Further, the oiling adopts rust preventive oil, and the viscosity (40 ℃) of the rust preventive oil is 15-20mm2/s。
In the oil removing and acid washing working procedure, alkali liquor is used for removing oil, and the oil removing temperature is 50-80 ℃; the pickling time is 5-15min, the pickling temperature is 30-50 ℃, and the surface energy of the pickled substrate is 1.5-1.8J/m2。
Further, the main components of the alkali liquor comprise 1 to 5 percent of alkali, 0.1 to 0.5 percent of emulsifier and 0.1 to 0.3 percent of trisodium phosphate according to the concentration; the alkali is NaOH and Na2CO3，Na2SiO3At least one of phosphate; the emulsifier is alkyl sulfonate, and the number of alkyl carbons is 12-14.
Furthermore, the pickling solution adopted by the pickling is hydrochloric acid-sulfuric acid mixed acid or phosphoric acid-citric acid mixed acid, wherein the concentration of the mixed acid is 2-5%, and the corrosion inhibitor is 0.5-1% of thiourea.
In the surface conditioning process, the adopted surface conditioning agent is colloidal titanium with the concentration of 0.08-0.12%, the surface conditioning temperature is room temperature, and the time is 30-90s.
In the phosphating treatment process, the phosphating treatment time is 2-3min and the temperature is 30-40 ℃.
Further, the total acidity of the phosphating tank solution adopted in the phosphating treatment is 18-22Pt, the free acidity is 1-3Pt, and the main component of the phosphating tank solution is ZnH2PO4，Zn(NO3)2，H3PO4，NaNO2，NaF，Mn(NO3)2(ii) a Wherein ZnH2PO41-3% concentration of Mn (NO)3)2The concentration is 0.1-0.3%.
Furthermore, the thickness of the film layer after the phosphating treatment is 1-2 μm.
The invention has the beneficial effects that: the preparation method of the cold-rolled automobile plate adopted by the invention improves the surface quality of the steel plate by controlling the components of the casting blank, hot rolling, cold rolling, annealing, leveling and other processes, and also limits the processes of degreasing, pickling, surface adjustment, phosphating and the like which are usually ignored in the prior art. The method has the advantages that a lot of factors influence the phosphating film forming of the automobile plate, and the high-quality phosphating film cannot be prepared only by controlling the characteristics of grain size, surface element distribution, surface roughness and the like, so that the method limits the emulsion in the rolling process, ensures that the surface of the substrate has higher cleanliness and less residues, avoids the enrichment of harmful elements on the surface of the substrate, and further improves the phosphating performance of the automobile plate; in order to ensure the degreasing and cleaning effects, the invention limits the surface coating oil quantity and the quality of the antirust oil of the strip steel, and further improves the phosphating and film forming quality of the automobile plate.
By adopting the alloy components and the process control method, the surface of the prepared cold-rolled automobile plate has no obvious element enrichment phenomenon, and the surface has a uniform phosphating reaction process; meanwhile, the acid-washing oil-removing degreasing process designed by the invention can improve the surface cleanliness and the surface energy of the cold-rolled automobile sheet; the invention provides a method for controlling the phosphating film-forming quality of an automobile plate in a full flow, and the formed phosphating film layer has a compact structure, uniform crystallization, granular shape, an average grain size of 2-3 mu m, smaller porosity and higher coatability.
Drawings
FIG. 1 is a map of the surface appearance of the phosphating film of the surface of a cold-rolled automobile plate prepared in the embodiment 1 of the invention;
FIG. 2 is a topographic map of the phosphating film on the surface of the cold-rolled automobile plate prepared in the embodiment 2 of the invention.
Detailed Description
The technical solution of the present invention can be specifically implemented as follows.
The method for improving the coatable performance of the surface of the cold-rolled automobile plate comprises the process flows of smelting and casting → hot rolling and coiling → acid pickling and cold rolling → continuous annealing → smooth oiling → oil removing and acid pickling → surface adjustment → phosphating treatment.
In the smelting and casting process, the alloy is smelted and cast into a casting blank according to chemical components, wherein the chemical components comprise, by mass, not more than 0.25% of C, not more than 0.30% of Si, not less than 0.05% or not more than 3% of Mn, not more than 0.01% of P, not more than 0.01% of S, not more than 0.02% of Al, not more than 0.01% of N, not more than 0.02% of As + Sn, and the balance of Fe and inevitable impurities.
In order to avoid the coarsening of the grain structure caused by over-burning, reduce the deformation resistance of the blank during finish rolling and facilitate the subsequent pickling and cold rolling process, the casting blank is preferably heated to 1150-1300 ℃ and is kept for 2-4h for rolling in the hot rolling and coiling process, and the final rolling temperature is more than or equal to 850 ℃; and coiling after rolling, wherein the coiling temperature is 400-600 ℃, and the hot rolled coil is obtained.
In order to completely remove the scale on the surface of the steel sheet, avoid the formation of surface defects, and improve the ductility and the texture uniformity of the steel sheet, it is preferable that the pickling speed in the pickling and cold rolling step is 80 to 120m/min, the cold rolling reduction is 40 to 60%, the saponification value of the emulsion is 100 to 200mgKOH/g, and the temperature of the emulsion is 50 to 70 ℃ to obtain the cold-hardened steel strip.
To liftThe effect of high acid cleaning ensures that the surface of the substrate has higher cleanliness and less residues, so that the saponification value of the emulsion is more preferably 150-180mgKOH/g, the temperature of the emulsion is 55-60 ℃, and the content of the miscellaneous oil in the emulsion is less than or equal to 3 percent; the corrosion inhibitor in the emulsion is at least one of urotropine, thiourea and thiourea-aluminum sulfate in the acid washing solution, and the mass fraction is 0.5-1.5%. More preferably, the total amount of the residues (residual oil + residual iron) on the surface of the cold-hard strip after cold rolling is less than or equal to 200mg/m2The surface reflectivity is more than or equal to 80 percent.
Based on the influence of the annealing process on the matrix structure and the performance of the strip steel, the influence on the thickness of the oxide layer in the surface layer of the steel plate and the influence on the forming performance, the annealing process preferably heats the steel plate to 800-930 ℃ at the speed of 10-20 ℃/s, keeps the temperature for 30-200s, cools the steel plate to 350-450 ℃ at the speed of 50-100 ℃/s, and then cools the steel plate to room temperature to obtain the annealed steel plate.
In order to reduce iron oxide on the surface of the steel strip, it is preferable that the atmosphere in the annealing furnace is N2-H2In which H is2The content is 0.5-20%, and the dew point temperature of the annealing atmosphere is-40-10 ℃.
The average grain size of the annealed steel plate is 8-10 mu m, and the thickness of the oxide film layer is less than or equal to 3 mu m.
The pretreatment process of coating (oil removal and acid pickling-surface conditioning-phosphating) and the surface energy of the substrate are main factors influencing the phosphating and film forming quality of the automobile plate, and the improper pretreatment process of coating directly influences the phosphating effect of the automobile plate and further influences the coatability of the automobile plate, so the oil removal, acid pickling-surface conditioning-phosphating process must be limited.
In the leveling oiling procedure, the surface roughness Ra value of the leveled strip steel is controlled to be 0.7-1.3 mu m, and the Rpc value is controlled to be 80-130; the oiling adopts a spraying mode, the spraying temperature is 30-50 ℃, and the oil coating amount on the surface of the strip steel is 600-1000mg/m2。
Usually, the surface of the strip steel needs to be subjected to antiseptic treatment, the quality and the oil quantity of the antirust oil directly influence the degreasing and cleaning effect, further influence the phosphating and film forming quality of the automobile plate, and in order to achieve better oiling and antirust effects, the surface of the strip steel is preferably subjected to the antiseptic treatmentThe oiling is performed by using anti-rust oil, and the viscosity (40 ℃) of the anti-rust oil is 15-20mm2And s. More preferably, in the oil removing and acid washing process, alkali liquor is used for removing oil, and the oil removing temperature is 50-80 ℃; the pickling time is 5-15min, the pickling temperature is 30-50 ℃, and the surface energy of the pickled substrate is 1.5-1.8J/m2。
In order to achieve better oil and fat removing effect, it is preferable that the alkali liquor comprises 1-5% of alkali, 0.1-0.5% of emulsifier and 0.1-0.3% of trisodium phosphate; the alkali is NaOH and Na2CO3，Na2SiO3At least one of phosphate; the emulsifier is alkyl sulfonate, and the number of alkyl carbons is 12-14. More preferably, the pickling solution used for pickling is a hydrochloric acid-sulfuric acid mixed acid or phosphoric acid-citric acid mixed acid, wherein the concentration of the mixed acid is 2-5%, and the corrosion inhibitor is 0.5-1% thiourea.
In the surface conditioning process, the adopted surface conditioning agent is colloidal titanium with the concentration of 0.08-0.12%, the surface conditioning temperature is room temperature, and the time is 30-90s.
In the phosphating treatment process, the phosphating treatment time is 2-3min and the temperature is 30-40 ℃.
Preferably, the total acidity of the phosphating tank solution adopted in the phosphating treatment is 18-22Pt, the free acidity is 1-3Pt, and the main component of the phosphating tank solution is ZnH2PO4，Zn(NO3)2，H3PO4，NaNO2，NaF，Mn(NO3)2(ii) a Wherein ZnH2PO41-3% concentration of Mn (NO)3)2The concentration is 0.1-0.3%.
The thickness of the film layer after the phosphating treatment is 1-2 mu m.
The technical solution and effects of the present invention will be further described below by way of practical examples.
Examples
The invention provides two groups of examples for preparing cold-rolled automobile plates by adopting the method, and the main chemical components of the casting blanks of the examples 1 and 2 are shown in the table 1.
TABLE 1 example billet chemical composition%
| C | Si | Mn | P | S | Al | N | As | Sn | |
| Example 1 | 0.024 | 0.003 | 0.135 | 0.009 | 0.007 | 0.018 | 0.005 | 0.006 | 0.004 |
| Example 2 | 0.024 | 0.003 | 0.135 | 0.009 | 0.007 | 0.018 | 0.005 | 0.006 | 0.004 |
The specific experimental procedures for examples 1 and 2 were as follows:
1. smelting and pouring the chemical components in the table 1 into casting blanks, heating the casting blanks of the embodiments 1 and 2 to 1300 ℃, preserving heat for 2h, rolling and coiling, wherein the final rolling temperature is 880 ℃, and the coiling temperature is 600 ℃ to obtain hot rolled coils;
2. carrying out acid pickling and cold rolling on the hot rolled coil, wherein the specific process parameters are shown in table 2, and obtaining cold-hard strip steel;
example 1 Total amount of residues (residual oil + residual iron) on the surface of the chilled steel strip was 50mg/m2Surface reflectance of 85%;
example 2 Total amount of residues (residual oil + residual iron) on the surface of the chilled steel strip was 100mg/m2Surface reflectance is 90%;
TABLE 2 Cold Rolling Process by acid pickling
3. Carrying out continuous annealing treatment on the cold-hard strip steel, wherein the specific process parameters are shown in table 3, and obtaining an annealed steel plate;
the annealed steel sheet of example 1 had an average grain size of 10 μm and an oxide film layer thickness of 3 μm;
the average grain size of the annealed steel sheet of example 2 was 8 μm, and the thickness of the oxide film layer was 2 μm;
TABLE 3 annealing procedure
4. Carrying out leveling oiling treatment on the strip steel, wherein the specific process parameters are shown in a table 4;
TABLE 4 smooth oiling procedure
5. Degreasing the oiled steel plates of examples 1 and 2 with an alkali solution containing 0.5% dodecylsulphonate, 2% NaOH, 1% Na as an emulsifier for 3min at 50%2SiO3(ii) a The steel plates after oil removal in the embodiments 1 and 2 are subjected to acid cleaning and rust removal treatment at 30 ℃, and the adopted acid cleaning solution is 1.5% hydrochloric acid-0.5% sulfuric acid mixed acid and 1% thiourea corrosion inhibitor;
the steel plate of example 1 was pickled for 5min to obtain a substrate having a surface energy of 1.7J/m2；
The steel plate of example 2 was pickled for 10min to obtain a substrate having a surface energy of 1.7J/m2；
6. Carrying out surface conditioning on the substrates obtained in the acid-washed examples 1 and 2, wherein the adopted surface conditioning agent is colloidal titanium, the concentration of the surface conditioning agent is 0.1%, and the surface conditioning is carried out for 30s at room temperature;
7. the surface-adjusted steel plates of examples 1 and 2 were subjected to 2% ZnH2PO4，0.2％Mn(NO3)2The phosphating bath solution is used for phosphating, wherein the free acidity of the phosphating solution is 3Pt, the total acidity is 22Pt, the phosphating time is 3min, and the phosphating temperature is 40 ℃, so that the cold-rolled automobile plate coated with the surface phosphating film is obtained.
The surface phosphating films of the cold-rolled automobile plates obtained in the examples 1 and 2 are detected:
FIG. 1 is a map of the surface of a phosphating film of a cold-rolled automobile plate prepared in example 1 of the invention, and FIG. 2 is a map of the surface of a phosphating film of a cold-rolled automobile plate prepared in example 2 of the invention, wherein it can be seen that the average grain size of the phosphating film prepared in example 1 is 2 μm, and the average grain size of the phosphating film prepared in example 2 is 3 μm; the phosphating film prepared by the method has the advantages of compact structure, uniform crystallization, granular shape, smaller porosity and higher coatability.
Claims (2)
1. The method for improving the coatability of the surface of the cold-rolled automobile plate is characterized by comprising the following steps of: the method comprises the process flows of smelting and casting → hot rolling and coiling → acid pickling and cold rolling → continuous annealing → smooth oiling → oil removing and acid pickling → surface adjustment → phosphating treatment;
in the smelting and casting process, smelting and casting into a casting blank according to chemical components, wherein the chemical components comprise, by mass, not more than 0.25% of C, not more than 0.30% of Si, not less than 0.05% or not more than 3% of Mn, not more than 0.01% of P, not more than 0.01% of S, not more than 0.02% of Al, not more than 0.01% of N, not more than 0.02% of As + Sn, and the balance of Fe and inevitable impurities;
in the hot rolling and coiling process, a casting blank is heated to 1150-1300 ℃, heat preservation is carried out for 2-4h, and then rolling is carried out, wherein the final rolling temperature is more than or equal to 850 ℃; coiling after rolling, wherein the coiling temperature is 400-600 ℃, and obtaining a hot rolled coil;
in the pickling and cold rolling process, the pickling speed is 80-120m/min, the cold rolling reduction is 40-60%, the saponification value of the emulsion is 100-200mgKOH/g, and the temperature of the emulsion is 50-70 ℃ to obtain the cold-hard strip steel;
in the continuous annealing process, heating to 800-930 ℃ at the speed of 10-20 ℃/s, preserving heat for 30-200s, cooling to 350-450 ℃ at the speed of 50-100 ℃/s, and then air-cooling to room temperature to obtain an annealed steel plate; atmosphere of annealing furnace is N2-H2In which H is2The content is 0.5-20%, and the dew point temperature range of the annealing atmosphere is-40 ℃ to 10 ℃;
in the leveling oiling process, the surface roughness Ra value of the leveled strip steel is controlled to be 0.7-1.3 mu m, and the Rpc value is controlled to be 80-130; the oiling is carried out in a spraying mode, the spraying temperature is 30-50 ℃, and the oil coating amount on the surface of the strip steel is 600-1000mg/m2；
In the oil removing and acid washing process, alkali liquor is used for removing oil, and the oil removing temperature is 50-80 ℃; the pickling time is 5-15min, the pickling temperature is 30-50 ℃, and the surface energy of the pickled substrate is 1.5-1.8J/m2；
In the surface adjustment procedure, the adopted surface conditioning agent is colloidal titanium, the concentration is 0.08-0.12%, the surface conditioning temperature is room temperature, and the time is 30-90s;
in the phosphating process, the phosphating time is 2-3min and the temperature is 30-40 ℃.
2. The method of improving paintability of a cold rolled automotive sheet surface according to claim 1, wherein: the saponification value of the emulsion is 150-180mgKOH/g, the temperature of the emulsion is 55-60 ℃, and the content of the miscellaneous oil in the emulsion is less than or equal to 3 percent; the corrosion inhibitor in the emulsion is at least one of urotropine, thiourea and thiourea-aluminum sulfate, and the mass fraction is 0.5-1.5%.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202111269247.XA CN114231822B (en) | 2021-10-29 | 2021-10-29 | Method for improving surface coatability of cold-rolled automobile plate |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202111269247.XA CN114231822B (en) | 2021-10-29 | 2021-10-29 | Method for improving surface coatability of cold-rolled automobile plate |
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| Publication Number | Publication Date |
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| CN114231822A CN114231822A (en) | 2022-03-25 |
| CN114231822B true CN114231822B (en) | 2022-11-01 |
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| CN104388827A (en) * | 2014-12-01 | 2015-03-04 | 武汉钢铁(集团)公司 | Self-lubrication alloying galvanized steel plate for automobiles and preparation method of self-lubrication alloying hot galvanized steel plate |
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| CN106011652B (en) * | 2016-06-28 | 2017-12-26 | 宝山钢铁股份有限公司 | A kind of excellent cold rolling low-density steel plate of phosphorus characteristic and its manufacture method |
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| CN109136739B (en) * | 2018-06-29 | 2020-08-04 | 唐山钢铁集团有限责任公司 | Control method for coatable performance surface quality of dual-phase steel cold-rolled high-strength automobile plate |
| CN109136755B (en) * | 2018-08-31 | 2020-11-24 | 包头钢铁（集团）有限责任公司 | Cold-rolled high-strength steel for automobiles and production method thereof |
| CN111647733B (en) * | 2020-05-11 | 2022-03-22 | 首钢集团有限公司 | Method for improving phosphating performance of low-carbon aluminum killed steel automobile plate and automobile plate |
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