Title of Invention: Steel sheet with improved resistance to yellowing and phosphate treatment and method for manufacturing the same
technical field
[One]
The present invention relates to a steel sheet having improved yellowing resistance and phosphate treatment properties and a method for manufacturing the same, and more particularly, by inhibiting the formation of an oxide film on the steel sheet surface after pickling-water washing or heat treatment-water cooling of the steel sheet, thereby preventing yellowing resistance and phosphate treatment It relates to a steel sheet having improved properties and a method for manufacturing the same.
background
[2]
Cold-rolled steel sheet is mainly used after phosphate treatment in order to secure coating film adhesion during the painting process. will receive In particular, the factors that frequently cause poor coating quality are the lack of uniformity and lack of coverage of the phosphate film. When the uniformity of the phosphate film is insufficient, there is a problem in that unevenness occurs on the surface after painting, and when the coverage of the phosphate film is insufficient, there is a problem in that corrosion resistance is reduced. Therefore, in order to secure the uniformity of the phosphate film, uniform reactivity between the base iron and the phosphate solution is required.
[3]
To this end, the steel sheet manufacturer must manufacture a cold-rolled steel sheet with uniform characteristics on the entire surface of the product, and the product processor must optimize the phosphate treatment conditions so that a uniform phosphate reaction occurs during chemical conversion. In addition, in order to solve the problem of insufficient coverage due to the non-formation of the phosphate film, it is necessary to manufacture a steel sheet having excellent reactivity with the phosphate solution.
[4]
However, the cold-rolled steel sheet is oxidized during the manufacturing process to form an oxide film on the surface. This oxide film is characterized in that it is formed thick or thin depending on the difference in steel composition, position of the steel plate, and operating conditions, and it affects the uniformity and coverage of the phosphate film when phosphating at product processing companies. This is because the oxide film interferes with the reaction between the steel sheet and the phosphate solution. If the thickness of the oxide film is non-uniform, the phosphate film is also formed non-uniformly. Also, if the thickness of the oxide film is thick, the phosphate film is not formed or the coverage is insufficient, resulting in deterioration of the coating quality. In addition, when the thickness of the oxide film is thick, yellowing is observed in the cold-rolled steel sheet itself, and the brightness is dark, which impairs the aesthetics. In particular, high-strength steel containing a relatively large amount of Si or Mn has a weak oxidation resistance, so yellowing occurs easily.
[5]
Patent Documents 1 to 3 propose a technique for solving the phosphate treatment properties among the above-mentioned problems.
[6]
Patent Document 1, among the steel components, when Mn is contained in the range of 2.3 to 2.5 wt%, the content of P is adjusted in the range of 0.01 to 0.07 wt%, and when Mn is contained in the range of 1.8 to 2.3 wt%, the amount of P It is a method of adjusting the content in the range of 0.07 to 0.09% by weight. However, the method of adjusting or changing the steel composition is not only an obstacle to securing the basic manufacturing specifications of the steel sheet, but also the technique disclosed in Patent Document 1 is not preferable because the effect of improving not only the phosphate treatment property but also the yellowing resistance is insignificant. .
[7]
Patent Document 2 manages the total of Cu and Cr elements in the steel component to 1000ppm or less, and manages the temperature of the Final Cooling Section (FCS) of the Continuous Annealing Line (CAL) to 110℃ or less. It is a technology for manufacturing cold-rolled steel sheets with excellent phosphate treatment properties by managing the surface roughness of temper rolling in the range of 0.9 to 1.4 μm. However, the technique disclosed in Patent Document 2 has a problem in that it is not easy to manage the illuminance, and the low-speed operation for securing the temperature of the longitudinal cooling section is inevitable, resulting in a decrease in productivity by 40 to 50%.
[8]
In Patent Document 3, copper of 0.2 to 20 mg/m 2 was additionally coated on the surface of the steel sheet to improve phosphate treatment properties. However, by coating the copper component, the appearance is dark, there is a problem that yellowing occurs, there is a disadvantage that the phosphate treatment improvement effect is also insufficient.
[9]
Patent Documents 4 to 7 propose a technique for solving the yellowing resistance problem among the above-mentioned problems.
[10]
Patent Document 4 discloses a technique for preventing corrosion of a hot-rolled steel sheet during a water washing process by neutralizing the pH of the washing solution using sodium hydroxide, and Patent Document 5 discloses at least one or two of alkylamines, alkyldiamines and alkyltetraamines. Disclosed is a stain and rust inhibitor for pickled steel sheets containing 40 to 80% by volume, 10 to 50% by volume of tetrahydro-1,4-oxazine as a high temperature stabilizer, and 10% by volume or more of anhydrous citric acid as an aqueous solution stabilizer has been Patent Document 6 discloses a technique for passivating the surface by treatment with an aqueous solution of a gluconate and polyquaternium compound, and Patent Document 7 discloses a reaction between a carboxylic acid and an alkali agent in a discoloration prevention treatment tank following acid washing. Disclosed is a technique for treating the discoloration inhibitor and removing the discoloration inhibitor in a subsequent washing bath.
[11]
However, the techniques described in the prior literature are not satisfactory in yellowing resistance, and in particular, there is a problem in that the yellowing resistance of high-strength steel, which has recently been greatly increased in demand, is further insufficient.
[12]
[Prior art literature]
[13]
[Patent Literature]
[14]
KR 2009-0103172
[15]
KR 1996-0063070
[16]
KR 1993-0031046
[17]
KR 2000-0082171
[18]
KR 2006-0079405
[19]
US 2002-201705
[20]
JP 2001-319765
DETAILED DESCRIPTION OF THE INVENTION
technical challenge
[21]
The present invention has been devised in view of the above circumstances, and in order to improve the phosphate treatment and yellowing resistance of the steel sheet, improving the phosphate treatment and yellowing resistance in the Water Cooling Section or Water Rinsing Section We want to provide the technology to carry out the processing.
means of solving the problem
[22]
According to an aspect of the present invention, as a steel sheet containing 0.5 wt% or more of Mn, 0.01 to 10 mg/m 2 Ca + Mg, 0.01 to 10 mg/m as a component excluding the steel component on the surface of the steel sheet after pickling, water washing and drying A steel sheet having improved yellowing resistance and phosphating properties is provided, containing P of 2, C of 0.01 to 20 mg/m 2 and O of 0.05 to 30 mg/m 2 .
[23]
The steel sheet may have a yellowness of 3.0 or less.
[24]
From the group consisting of N, Cl, F, Na, Al, Si, S, K, Ti, V, Cr, Mn, Co, Ni, Fe, Cu, Zn, Zr and Mo except for the steel component on the surface of the steel sheet At least one component selected may be further contained in an amount of 10 mg/m 2 or less (excluding 0).
[25]
According to another aspect of the present invention, there is provided a method for manufacturing a surface-treated steel sheet comprising at least one of the following treatment steps (1) to (6) on the steel sheet having improved yellowing resistance and phosphate treatment properties.
[26]
(1) forming a flash plating layer including at least one component of Ni, Fe, Cu, or Zn on the steel sheet having improved yellowing resistance and phosphate treatment;
[27]
(2) forming a phosphating layer on the steel sheet having improved yellowing resistance and phosphate treatment;
[28]
(3) plating at least one component of Zn, Al, Mg, and Si on the steel sheet having improved yellowing resistance and phosphate treatment by hot-dip plating or electroplating;
[29]
(4) applying a rust preventive oil on the steel sheet having improved yellowing resistance and phosphate treatment;
[30]
(5) forming a resin layer by applying a resin composition on the steel sheet having improved yellowing resistance and phosphate treatment;
[31]
(6) forming a coating layer by applying a paint on the steel sheet with improved yellowing resistance and phosphate treatment.
[32]
According to another aspect of the present invention, as a steel sheet containing 0.5 wt% or more of Mn, 0.01 to 10 mg/m 2 of Ca + Mg, 0.01 as a component excluding the steel component on the surface of the steel sheet after annealing heat treatment, water cooling and drying To 10 mg/m 2 of P, 0.01 to 20 mg/m 2 of C and 0.05 to 30 mg/m 2 of O, a steel sheet having improved yellowing resistance and improved phosphate treatment is provided.
[33]
The steel sheet may have a yellowness of 3.0 or less.
[34]
From the group consisting of N, Cl, F, Na, Al, Si, S, K, Ti, V, Cr, Mn, Co, Ni, Fe, Cu, Zn, Zr and Mo except for the steel component on the surface of the steel sheet At least one component selected may be further contained in an amount of 10 mg/m 2 or less (excluding 0).
[35]
According to another aspect of the present invention, there is provided a method for manufacturing a surface-treated steel sheet comprising at least one or more of the following treatment steps (1) to (6) on the steel sheet having improved yellowing resistance and phosphate treatment properties. do.
[36]
(1) forming a flash plating layer including at least one component of Ni, Fe, Cu, or Zn on the steel sheet having improved yellowing resistance and phosphate treatment;
[37]
(2) forming a phosphating layer on the steel sheet having improved yellowing resistance and phosphate treatment;
[38]
(3) plating at least one component of Zn, Al, Mg, and Si on the steel sheet having improved yellowing resistance and phosphate treatment by hot-dip plating or electroplating;
[39]
(4) applying a rust preventive oil on the steel sheet having improved yellowing resistance and phosphate treatment;
[40]
(5) forming a resin layer by applying a resin composition on the steel sheet having improved yellowing resistance and phosphate treatment;
[41]
(6) forming a coating layer by applying a paint on the steel sheet with improved yellowing resistance and phosphate treatment.
Effects of the Invention
[42]
According to the present invention, in the manufacturing process of the steel sheet, by performing chemical conversion treatment to improve the phosphate treatment resistance yellowing resistance on the surface of the steel sheet in the water cooling section or water washing section, the surface quality of products using the same and various subsequent treatment products are improved has the effect of being
Best mode for carrying out the invention
[43]
Hereinafter, preferred embodiments of the present invention will be described with reference to various examples. However, the embodiments of the present invention may be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below.
[44]
In general, the continuous annealing process line for manufacturing a cold rolled steel sheet can be subdivided into two types of processes. One is that the steel sheet continuously enters the annealing furnace and completes heat treatment in a reducing atmosphere, then cools in the water cooling section and exits the annealing furnace. It is a manufacturing process In the other case, after the steel sheet continuously enters the annealing furnace and completes heat treatment in a reducing atmosphere, it is cooled in the water cooling section and exits the annealing furnace. It is the process of making cold rolled steel sheet. The post-treatment is usually carried out by pickling oxides present on the surface of the steel sheet while passing through the pickling section-washing section and the metal coating section-washing section, and, if necessary, performing a metal-based coating such as Ni, Zn, Cu and Fe. means processing.
[45]
An oxide film is formed on the surface of the cold-rolled steel sheet manufactured through the above process, and such an oxide film is mainly formed by oxidizing steel components in the water cooling section and the water washing section where the steel sheet comes into contact with water. The oxide film has a problem in that the quality of the post-process, such as phosphate treatment, is deteriorated, and the appearance is deteriorated by causing yellowing. In particular, since high-strength steel contains a large amount of strongly oxidizing components such as manganese, silicon, and aluminum, it is easily oxidized, and thus, the oxide film is thick and yellowing is more likely to occur.
[46]
Accordingly, the present invention provides cold rolling with improved phosphate treatment and yellowing resistance by performing chemical conversion treatment with the effect of promoting phosphate nucleation and inhibiting yellowing on the surface of the steel sheet in at least one of the water-cooled section and the water-washing section. We would like to provide a steel plate.
[47]
According to an aspect of the present invention, as a steel sheet containing 0.5 wt% or more of Mn, 0.01 to 10 mg/m 2 of Ca + Mg, 0.01 to 10 mg /m 2 as a component excluding the steel component on the surface of the steel sheet after pickling, water washing and drying of P, 0.01 to 20 mg/m 2 of C, and 0.05 to 30 mg/m 2 of O, a steel sheet having improved phosphating properties and yellowing resistance is provided.
[48]
In addition, according to another aspect of the present invention, as a steel sheet containing 0.5 wt% or more of Mn, 0.01 to 10 mg/m 2 of Ca + Mg, 0.01 to 10 mg/m 2 as a component excluding the steel component on the surface of the steel sheet after annealing heat treatment, water cooling and drying A steel sheet with improved yellowing resistance and phosphating properties is provided containing 10 mg/m 2 of P, 0.01 to 20 mg/m 2 of C and 0.05 to 30 mg/m 2 of O.
[49]
A steel sheet having an Mn content of less than 0.5% by weight does not require a separate treatment for this, since an oxide film is not severely formed in the water cooling and water washing steps. However, in the steel sheet containing Mn in an amount of 0.5% by weight or more, the steel components react with moisture and oxygen in the water cooling and water washing steps to form a large amount of oxide film, and thus, in the subsequent process, phosphating property, Ni flash (flash) ) Not only the quality of processability and paintability is deteriorated, but also yellowing occurs, so a treatment for this is required. Therefore, in the present invention, as a substrate for improving phosphate treatment and yellowing resistance, it is more preferable to apply to a steel sheet containing 0.5 wt% or more of Mn among the steel components of the steel sheet.
[50]
The steel sheet having improved phosphate treatment and yellowing resistance according to an embodiment of the present invention may include Ca, Mg, P, C and O as components excluding the steel component on the surface of the steel sheet. Ca, Mg, P and C are the composition of the chemical conversion solution contained in the cooling water of the water cooling section and the washing water of the water washing section after the annealing heat treatment of the steel sheet is dried on the surface of the steel sheet after drying, O is the cooling water and the washing water It may be detected from the composition of the chemical conversion solution included and the oxide component unavoidably formed on the surface of the steel sheet. The Ca, Mg, P, C and O are attached to the surface of the steel sheet in a predetermined amount after water cooling and water washing, thereby improving the phosphate treatment properties and yellowing resistance of the steel sheet.
[51]
Components attached to the surface of the cold-rolled steel sheet after water cooling, washing with water and drying are preferably attached to the total content of Ca and Mg, that is, Ca + Mg in a content of 0.01 to 10 mg/m 2 . When the adhesion amount of Ca + Mg is less than 0.01 mg/m2, sufficient phosphating property cannot be exhibited. There is a problem in that the stability of the chemical conversion solution is lowered.
[52]
P is preferably attached to the surface of the steel sheet in an amount of 0.01 to 10 mg/m 2 . When the adhesion amount of P is less than 0.01 mg/m2, sufficient phosphate treatment properties and yellowing resistance cannot be exhibited, and when the adhesion amount of P exceeds 10 mg/m2, there is a problem in that the steel sheet is stained and the surface is rather dark.
[53]
C is preferably attached to the surface of the steel sheet in an amount of 0.01 to 20 mg/m 2 . When the adhesion amount of C is less than 0.01 mg/m2, sufficient yellowing resistance cannot be exhibited, and when it exceeds 20 mg/m2, there is a problem in that the surface appearance is lowered and the phosphate treatment property in the subsequent process is lowered.
[54]
The steel sheet according to an embodiment of the present invention includes O together with the Ca, Mg, P and C, and the O is preferably attached in an amount of 0.05 to 30 mg/m 2 . When the adhesion amount of O is less than 0.05 mg/m2, there is a problem that sufficient yellowing resistance cannot be exhibited. There is a problem with making
[55]
In addition, according to another preferred embodiment of the present invention, except for the steel component on the surface of the steel sheet, in addition to Ca, Mg, P, C and O, N, Cl, F, Na, Al, Si, S, K, Ti , V, Cr, Mn, Co, Ni, Fe, Cu, Zn, Zr and Mo may be further included. These components may be included in one kind, of course, two or more kinds may be included.
[56]
At this time, the total adhesion amount of the N, Cl, F, Na, Al, Si, S, K, Ti, V, Cr, Mn, Co, Ni, Fe, Cu, Zn, Zr and Mo components is 10 mg/m 2 or less (However, 0 is excluded). When the total adhesion amount of the additional components exceeds 10 mg/m 2 , there is a problem in that the surface appearance of the steel sheet is deteriorated due to the occurrence of stains on the surface of the steel sheet.
[57]
As the coverage of the phosphate film formed by phosphating treatment is lower than about 90%, there is a problem in that the paintability is lowered. However, the steel sheet according to an embodiment of the present invention contains Ca, By attaching a predetermined amount of Mg, P, C and O, it is possible to achieve good coverage of the phosphate film of 90% or more when phosphate treatment is performed.
[58]
In addition, the cold-rolled steel sheet according to an embodiment of the present invention has a predetermined amount of Ca, Mg, P, C and O attached to the surface of the dried steel sheet after water cooling and water washing as described above, thereby suppressing yellowing of the steel sheet during water cooling and water washing. can The quality of the yellowing-resistant steel sheet is a value measured by a color difference meter (Minolta Spectrophotometer, CM3700d), and it is preferable that the yellowness of the steel sheet surface is 3 or less. When the yellowness of the surface of the steel sheet shows a low value of 3 or less, the surface appearance is excellent, but when the yellowness exceeds 3, the surface appearance is bad due to severe yellowing, and there is a problem of lowering the phosphate treatment property, which is a post process.
[59]
As described above, the cold-rolled steel sheet having excellent phosphate treatment properties and yellowing resistance according to an embodiment of the present invention can effectively inhibit the formation of an oxide film on the steel sheet during water cooling or water washing, while forming a film that promotes phosphate nucleation. Therefore, it is applicable to the manufacturing process of steel sheet that is subjected to water cooling and water washing, such as a hot-rolled pickling process, a hot-rolled pickling oiling process, a hot-rolled pickling plating process, a continuous annealing process, a stainless steel process, a hot-dip plating process, and an electric galvanizing process.
[60]
Cold-rolled steel sheet with excellent phosphate treatment and yellowing resistance as described above can be produced by applying a chemical treatment solution composition that can provide Ca, Mg, P, C and O in the same amount as above on the surface of the steel sheet, and cooling or washing the steel sheet with water. can
[61]
As described above, by adding and treating the phosphate treatment accelerator and oxidation inhibitor composition as described above in cooling water and water for water cooling or washing the steel sheet after annealing, a cold-rolled steel sheet having excellent phosphate treatment properties and yellowing resistance can be manufactured. At this time, the cold-rolled steel sheet provided in the present invention can be obtained by allowing Ca, Mg, P, C and O as described above to remain in a predetermined amount on the surface of the steel sheet. The content of Ca, Mg, P, C and O adhering to the surface of the steel sheet may be obtained by appropriately adjusting the composition in cooling water or washing water. In addition, it can be obtained by adjusting the treatment conditions of the cooling and water washing process, that is, time, temperature, concentration, and the like. As such, if Ca, Mg, P, C, and O can be attached to the content as described above, the method is not particularly limited.
[62]
For example, 1 to 5% by weight of calcium chloride, 1 to 5% by weight of magnesium chloride, 5 to 15% by weight of phosphate ester, 5 to 15% by weight of ethylamine, 2 to 10% by weight of sodium carbonate, 1 to 10% by weight of ammonium acetate %, an oxidation inhibitor 0.1 to 2% by weight, and the remaining solvent is applied to at least one process of water washing or water cooling of the steel sheet, so that a cold-rolled steel sheet having excellent phosphate treatment properties and yellowing resistance can be manufactured. The solvent of the washing composition may be distilled water or water or distilled water or water containing a small amount of surfactant.
[63]
Meanwhile, the oxidation inhibitor is not particularly limited, but at least one selected from a phosphoric acid ester compound, an amine compound, a carbonate compound, a glycol compound, and an acetate compound may be used.
[64]
Meanwhile, according to another aspect of the present invention, at least one or more including the following treatment steps (1) to (6) and similar treatment steps on the steel sheet with improved yellowing resistance and phosphate treatment properties described above There is provided a method for manufacturing a surface-treated steel sheet comprising the step.
[65]
(1) forming a flash plating layer including at least one component of Ni, Fe, Cu, or Zn on the steel sheet having improved yellowing resistance and phosphate treatment;
[66]
(2) forming a phosphating layer on the steel sheet having improved yellowing resistance and phosphate treatment;
[67]
(2) forming a phosphating layer on the steel sheet having improved yellowing resistance and phosphate treatment;
[68]
(3) plating at least one component of Zn, Al, Mg, and Si on the steel sheet having improved yellowing resistance and phosphate treatment by hot-dip plating or electroplating;
[69]
(4) applying a rust preventive oil on the steel sheet having improved yellowing resistance and phosphate treatment;
[70]
(5) forming a resin layer by applying a resin composition on the steel sheet having improved yellowing resistance and phosphate treatment;
[71]
(6) forming a coating layer by applying a paint on the steel sheet with improved yellowing resistance and phosphate treatment.
[72]
Accordingly, the cold-rolled steel sheet according to an embodiment of the present invention includes a flash plating layer including at least one component of Ni, Fe, Cu, or Zn on the steel sheet; phosphating layer; a plating layer comprising at least one component of Zn, Al, Mg, and Si; anti-rust oil layer; resin layer; And at least one of the coating layers may be formed.
Modes for carrying out the invention
[73]
Hereinafter, the present invention will be described in more detail through specific examples. The following examples are only examples to help the understanding of the present invention, and the scope of the present invention is not limited thereto.
[74]
Example
[75]
Experimental Examples 1 to 4
[76]
As the composition of the steel sheet, a 980 MPa grade cold-rolled steel sheet having a thickness of 1.0 mm containing 1.1 wt% of Si and Mn as shown in Table 1 below was used.
[77]
The specimens were immersed in 500 ml (80° C.) of hydrochloric acid at a concentration of 5% by weight for 5 seconds to perform pickling, followed by washing with distilled water. For each specimen after pickling and water washing, yellowness was measured using a colorimeter (Minolta Spectrophotometer, CM3700d), and yellowing resistance was evaluated depending on whether yellowing occurred. The evaluation criteria are as follows.
[78]
○ - Yellowing resistance: When the yellowness is 3 or less
[79]
× - No yellowing resistance: when yellowness exceeds 3
[80]
On the other hand, each specimen after the pickling and water washing was subjected to surface conditioning under the following conditions, followed by phosphate treatment.
[81]
- Surface adjustment: Chemical name PL-Z (Daehan Parkerizing Co., Ltd.), concentration pH 7.5~11, treatment time 21 seconds, surface conditioning solution temperature 25~35℃
[82]
- Phosphate treatment: Chemical name PB-37 (Daehan Parkerizing Co., Ltd.), free acidity 0.6~1 point, treatment time 80 seconds, phosphating solution temperature 40~45℃
[83]
For each specimen subjected to the phosphate treatment under the above conditions, the adhesion state of the phosphate particles was observed with a scanning electron microscope (SEM), and the coverage of the phosphate particles was measured using an image analyzer to evaluate the phosphate treatment properties. At this time, the evaluation of the phosphate treatment was performed according to the following criteria.
[84]
○ - Good phosphating property: 90% or more coverage
[85]
× - poor phosphating performance: less than 90% coverage
[86]
The results of yellowing resistance and phosphate treatment are shown in Table 1 below.
[87]
[Table 1]
division Specimen steel composition (wt%) quality characteristics
Psalm No. manganese phosphate yellowing resistance
Experimental Example 1 Psalm 1 0.3 ○ ○
Experimental Example 2 Psalm 2 0.5 × ×
Experimental Example 3 Psalm 3 2.8 × ×
Experimental Example 4 Psalm 4 3.5 × ×
[88]
As shown in Table 1, in the case of Specimen 1 containing less than 0.5% by weight of manganese in the composition of the steel, no yellowing occurred, and thus yellowing resistance and excellent phosphate properties were obtained. On the other hand, manganese In the case of Experimental Examples 2 to 4 applied to Specimens 2 to 4 having a content of 0.5 wt% or more, yellowing occurred and phosphate properties were lowered. From these results, it can be confirmed that the steel containing 0.5 wt% or more of manganese needs to provide anti-yellowing ability by anti-yellowing treatment.
[89]
Examples 1 to 15 and Comparative Examples 1 to 8
[90]
Using the same specimen 3 as the specimen used in Experimental Example 3 containing 2.8% by weight of Mn, pickling and water washing were performed under the same conditions as in Experimental Example 3, wherein water washing was performed instead of distilled water of Experimental Example 3, as follows It was immersed in 500 ml of the prepared washing solution for 10 seconds and washed with water.
[91]
The washing solution is composed of distilled water containing 3% by weight of calcium chloride, 3% by weight of magnesium chloride, 10% by weight of phosphate ester, 8% by weight of ethylamine, 6% by weight of sodium carbonate, 5% by weight of ammonium acetate, and a small amount of the remaining surfactant. A washing solution prepared by adding 0.5 wt% of a chemical conversion solution for improving yellowing resistance and phosphate to distilled water was used as a basic washing solution.
[92]
By performing water washing by appropriately changing the content of one or two or more of the constituent components of the washing solution, the amount of adhesion of the components adhering to the surface of the steel sheet, except for the steel component, was variously adjusted as shown in Table 2. At this time, the content of Ca, Mg, P, C, and O, excluding the steel component attached to the surface of each steel sheet, is determined by wet method, fluorescence X-ray spectroscopy (XRF), glow discharge spectroscopy (GDS), energy dispersive fluorescence spectroscopy (EDS). etc. were analyzed, and the results are shown in Table 2 below. According to the adhesion amount of each of these components, each specimen is described in order, and the yellowing resistance in each specimen is also described in Table 2.
[93]
On the other hand, when chemical conversion treatment is performed using the phosphate treatment improver and oxidation inhibitor, in addition to Ca, Mg, P, C and O components, Cl, N, Na, S components are additionally attached to the surface of the steel sheet. Although there were components, the additional components did not have a significant effect on phosphate treatment and oxidation resistance up to a predetermined content or did not show a certain tendency, so they were denoted as other components in this example.
[94]
Then, the surface of each sample washed with water was subjected to surface conditioning and phosphating in the same manner as in Experimental Example 1, then phosphate treatment was evaluated in the same manner as in Experimental Example 1, and surface appearance properties were evaluated in the following manner. . The evaluation results are shown in Table 2.
[95]
Surface appearance characteristics were evaluated based on the following criteria by visually observing the surfaces of the specimens washed with water and phosphate-treated specimens in each Example and Comparative Example, and whether or not stains were generated.
[96]
○-Good surface appearance: no staining at all
[97]
△-Medium surface appearance: Minor stains occur, but at the level that can be sold as a genuine product
[98]
×-Bad surface appearance: heavily stained
[99]
[Table 2]
division Steel sheet surface adhesion amount (mg/m2) quality characteristics
Ca + Mg P C O Etc
Anti -yellowing Phosphating
_ surface
appearance
Comparative Example 1 0 0.5 1.1 2 0 △ × △
Example 1 0.01 0.5 1.1 2 0 ○ △ ○
Example 2 0.5 0.5 1.1 2 0 ○ ○ ○
Example 3 10 0.5 1.1 2 0 ○ ○ ○
Comparative Example 2 15 0.5 1.1 2 0 ○ ○ ×
Comparative Example 3 0.5 0.005 1.1 2 0 △ × △
Example 4 0.5 0.01 1.1 2 0 ○ ○ △
Example 5 0.5 0.5 1.1 2 0 ○ ○ △
Example 6 0.5 10 1.1 2 0 ○ ○ △
Comparative Example 4 0.5 15 1.1 2 0 × ○ ×
Comparative Example 5 0.5 0.5 0.005 2 0 × × △
Example 7 0.5 0.5 0.01 2 0 ○ ○ △
Example 8 0.5 0.5 1.1 2 0 ○ ○ △
Example 9 0.5 0.5 20 2 0 ○ ○ △
Comparative Example 6 0.5 0.5 30 2 0 ○ × ×
Example 10 0.5 0.5 1.1 0.05 0 ○ ○ △
Example 11 0.5 0.5 1.1 2 0 ○ ○ △
Example 12 0.5 0.5 1.1 30 0 ○ ○ △
Comparative Example 7 0.5 0.5 1.1 40 0 × × ×
Example 13 0.5 0.5 1.1 2 0.01 ○ ○ ○
Example 14 0.5 0.5 1.1 2 0.5 ○ ○ ○
Example 15 0.5 0.5 1.1 2 10 ○ ○ △
Comparative Example 8 0.5 0.5 1.1 2 15 ○ △ ×
[100]
As can be seen from Table 2 above, Ca + Mg is attached to the surface of the specimens having phosphate treatment and yellowing resistance after water washing in the range of 0.01 to 10 mg/m 2 , and P is in the range of 0.01 to 10 mg/m 2 It can be seen that C is attached in the range of 0.01 to 20 mg/m 2 , O is attached in the range of 30 mg/m 2 or less, and other components are attached in the range of 10 mg/m 2 or less. have. In addition, the specimens having the components in this range were evaluated as having good surface appearance. However, in Comparative Examples 1 and C, in which Ca + Mg was less than 0.01 mg/m 2 , and Comparative Examples 3 and C in which the adhesion amount of P was less than 0.01 mg/m 2 , In Comparative Example 5, the adhesion amount was less than 0.01 m), the yellowness was greater than 3 or the phosphate coverage was measured to be less than 90%, indicating poor yellowing resistance and poor phosphate treatment.
[101]
On the other hand, in Comparative Examples 2, 4, 6, 7 and 8, in which the amount of Ca + Mg, P, C, O, or other components adhered in excess beyond the range limited by the present invention, phosphate treatment properties, yellowing resistance and surface appearance Among them, the quality of at least one or more of them was rather deteriorated.
[102]
From the above results, it can be seen that when the content of Ca + Mg, P, C and O is attached to the surface of the steel sheet after washing with water within the range suggested in the present invention, not only the phosphate treatment property is excellent, but also the yellowing resistance is excellent. can
[103]
In addition, in Examples 13 to 15 and Comparative Example 8, while the content of Ca + Mg, P, C and O was attached to the surface of the specimen after washing with water within the range of the present invention, other such as Cl, N, Na, S components, etc. The quality characteristics of the specimen when additional components are attached are evaluated. Here, in the case of Examples 13 to 15, phosphate treatment properties, yellowing resistance, and surface appearance all showed excellent results.
[104]
On the other hand, as in Comparative Example 8, when the total adhesion amount of the other components exceeded 10 mg/m 2 , severe staining was observed on the surface of the steel sheet. Therefore, it may be more preferable that the other components are attached to the surface of the water-washing steel sheet, but the content should not exceed 10 mg/m 2 It can be confirmed that a desirable effect is obtained.
[105]
On the other hand, in order to confirm the relationship between the surface appearance and the surface chromaticity, Comparative Examples 4, 6 and 7, which showed poor surface appearance results, and Examples 2, 5, and 14, which showed good surface appearance results separately from solution stability was measured for yellowness, and the results are shown in Table 3 below.
[106]
[Table 3]
division surface chromaticity quality characteristics
yellowness Anti-yellowing phosphate surface appearance
Comparative Example 4 3.8 × ○ ×
Comparative Example 6 3.5 ○ × ×
Comparative Example 7 4.1 × × ×
Example 2 1.0 ○ ○ ○
Example 4 3.0 ○ ○ △
Example 14 2.0 ○ ○ ○
[107]
Referring to Table 3, when the surface chromaticity of the steel sheet after washing with water satisfies 3.0 or less, which is the range of the present invention, it can be confirmed that phosphate properties, yellowing resistance and surface appearance are excellent.
[108]
Examples 16 to 18 and Comparative Examples 9 to 10
[109]
Examples 16 to 18 and Comparative Examples 9 to 10 are cold-rolled steel sheet manufacturing conditions that do not include a post-treatment process, that is, the annealed steel sheet is cooled in the water cooling section, exits the annealing furnace, and then passes through temper rolling and lubrication. In this process, the effect on phosphate treatment and yellowing resistance was evaluated according to the above-mentioned criteria by a method of cooling by composing a chemical conversion solution in the cooling water of the water cooling section in the same manner as in Example 1, and evaluating the results. It is shown in Table 4 below.
[110]
[Table 4]
division Steel sheet surface adhesion amount (mg/m2) quality characteristics
Ca + Mg P C O Etc
Anti -yellowing Phosphating
_ surface
appearance
Comparative Example 9 0.5 0.005 1.1 2 0 ○ × △
Example 16 0.5 0.01 1.1 2 0 ○ ○ △
Example 17 0.5 0.5 1.1 2 0 ○ ○ △
Example 18 0.5 10 1.1 2 0 ○ ○ △
Comparative Example 10 0.5 15 1.1 2 0 △ ○ ×
[111]
Referring to Table 4 above, even when applied to a general cold rolling process having only a water-cooled section without a post-treatment process, the content of Ca + Mg, P, C and O adhered to the steel sheet surface after water washing within the range suggested by the present invention. In this case, it can be seen that the phosphate treatment property, the yellowing resistance and the surface appearance are at a satisfactory level. Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and the claims are not limited thereto. It will be apparent to those skilled in the art that various modifications and variations are possible without departing from the technical spirit of the present invention as described.
Claims
[Claim 1]
A steel sheet containing 0.5 wt% or more of Mn, after pickling, water washing and drying, as a component excluding the steel component on the surface of the steel sheet, 0.01 to 10 mg/m 2 Ca + Mg, 0.01 to 10 mg/m 2 P, 0.01 to 20 mg/ m 2 of C and 0.05 to 30 mg/m 2 of O, the steel sheet having improved yellowing resistance and phosphate treatment.
[Claim 2]
The steel sheet according to claim 1, wherein the steel sheet has a yellowness of 3.0 or less.
[Claim 3]
According to claim 1, N, Cl, F, Na, Al, Si, S, K, Ti, V, Cr, Mn, Co, Ni, Fe, Cu, Zn, Zr except for the steel component on the surface of the steel sheet and at least one component selected from the group consisting of Mo in an amount of 10 mg/m 2 or less (excluding 0).
[Claim 4]
A method for manufacturing a surface-treated steel sheet comprising at least one of the following treatment steps (1) to (6) on the steel sheet with improved yellowing resistance and phosphate treatment according to any one of claims 1 to 3. (1) forming a flash plating layer including at least one component of Ni, Fe, Cu, or Zn on the steel sheet having improved yellowing resistance and phosphate treatment; (2) forming a phosphating layer on the steel sheet having improved yellowing resistance and phosphate treatment; (3) plating at least one component of Zn, Al, Mg, and Si on the steel sheet having improved yellowing resistance and phosphate treatment by hot-dip plating or electroplating; (4) applying a rust preventive oil on the steel sheet having improved yellowing resistance and phosphate treatment; (5) forming a resin layer by applying a resin composition on the steel sheet having improved yellowing resistance and phosphate treatment; (6) forming a coating layer by applying a paint on the steel sheet with improved yellowing resistance and phosphate treatment.
[Claim 5]
A steel sheet containing 0.5 wt% or more of Mn, after annealing heat treatment, water cooling and drying, 0.01 to 10 mg/m 2 Ca + Mg, 0.01 to 10 mg/m 2 P, 0.01 to 20 mg as a component excluding the steel component on the surface of the steel sheet A steel sheet with improved resistance to yellowing and phosphate treatment containing C of /m 2 and O of 0.05 to 30 mg/m 2 .
[Claim 6]
[6] The steel sheet according to claim 5, wherein the steel sheet has a yellowness of 3.0 or less.
[Claim 7]
According to claim 5, N, Cl, F, Na, Al, Si, S, K, Ti, V, Cr, Mn, Co, Ni, Fe, Cu, Zn, Zr except for the steel component on the surface of the steel sheet and at least one component selected from the group consisting of Mo in an amount of 10 mg/m 2 or less (excluding 0).
[Claim 8]
A method for manufacturing a surface-treated steel sheet comprising at least one of the following treatment steps (1) to (6) on the steel sheet with improved yellowing resistance and phosphate treatment according to any one of claims 5 to 7. (1) forming a flash plating layer including at least one component of Ni, Fe, Cu, or Zn on the steel sheet having improved yellowing resistance and phosphate treatment; (2) forming a phosphating layer on the steel sheet having improved yellowing resistance and phosphate treatment; (3) plating at least one component of Zn, Al, Mg, and Si on the steel sheet having improved yellowing resistance and phosphate treatment by hot-dip plating or electroplating; (4) applying a rust preventive oil on the steel sheet having improved yellowing resistance and phosphate treatment; (5) forming a resin layer by applying a resin composition on the steel sheet having improved yellowing resistance and phosphate treatment; (6) forming a coating layer by applying a paint on the steel sheet with improved yellowing resistance and phosphate treatment.