JPH0567710B2 - - Google Patents

Description

[Detailed description of the invention]

(Field of Industrial Application) The present invention provides a Sn coating layer that has excellent paintability, corrosion resistance after painting, paint adhesion after painting (so-called secondary paint adhesion), corrosion resistance, and corrosion resistance on the end face. This invention relates to a method for producing steel sheets for containers. (Conventional technology) As a steel sheet for containers that is painted and used,
As in Publication No. 55-69297, there is a Sn-based coated steel sheet with a chromate coating layer consisting of a two-layer coating composition of a metal Cr layer and a chromium oxide layer mainly composed of hydrated oxides on the Sn plating layer, which improves paint adhesion. , has excellent corrosion resistance after painting. In addition, for example, Japanese Patent Application Laid-Open No. 57-1999 has developed a steel sheet with an Sn-based coating layer that improves the corrosion resistance of steel sheets for containers.
There is a Sn-based coated steel sheet having a Ni-based base coating layer, as disclosed in Japanese Patent Application Laid-open No. 23091 and Japanese Patent Application Laid-Open No. 60-5884. These steel plates are designed to improve corrosion resistance through the superimposition of the base coating layer and the Sn coating layer, and by reducing the exposed portion of the base metal due to the formation of a uniform and dense alloy layer due to the effect of the base coating layer. Although the above-mentioned Sn-based coated steel sheets for containers have been used in some areas to take advantage of their properties, it is difficult to say that they have achieved sufficiently satisfactory paintability and corrosion resistance. (Problem to be solved by the invention) In recent years, the characteristics of steel sheets for containers have changed due to the diversification of can manufacturing methods,
Or, in response to consumers' preference for higher-end products, improvements in performance such as better paintability and less rusting during storage, or thinner steel sheets for containers to reduce can cost, can be achieved. There is a demand for improvements in corrosion resistance (that is, improvements in corrosion resistance life), etc.
For example, in response to the increasing number of deformed cans such as connected cans, it is desired to improve the corrosion resistance after painting of parts that have undergone more severe processing than before, or to improve paint adhesion when stored for a long time. In addition, the material for can lids is required to be easier to open than before, and in response to the reduction in the thickness of the can lid material and the thickness of the score processed area, we are increasing the corrosion resistance and paint adhesion of the processed area after painting. At the same time, there is a need to improve the corrosion resistance, especially the rust resistance, of the sheared portion of the score where the iron surface is exposed on the outer surface of the can lid in the score processing section. Furthermore, when an iron-based material is used for the tab of an easy-open-end can lid, corrosion resistance, especially rust resistance, is required for the end face of the material. In addition, the crown is required to have improved rust resistance on the end face of the crown, corrosion resistance after painting of the processed portion of the crown, and improved coating precision adhesion. Furthermore, in the welded can making method, further improvements are required in the corrosion resistance and paintability of the welded end face. In addition, coating layers (Sn coating layer, coating layer) can be applied to various contents or by processing such as deformed cans.
There is a high demand for the development of materials with excellent corrosion resistance and corrosion resistance, which are less prone to elution of Fe from the base steel even if they are damaged, are less prone to perforation corrosion, and have excellent corrosion resistance and long life. In response to these demands, the present inventors conducted various studies and found that the conventional steel sheets for containers (so-called tinplate) as described above are made of aluminum-killed steel sheets in which no corrosion-resistance-enhancing elements are consciously added to the plated base sheet. Because it has been
It was found that the couple corrosion current between the Sn plating layer and the plating original plate was extremely large. As a result, in an atmosphere where there is almost no oxygen, such as inside a can, the corrosion rate of the Metsch original plate is high due to the anode dissolution of Sn, so even in the defective parts of the coating film and the areas where the coating film has eaves, the dissolution of Sn causes the coating to be coated. It was found that the film peeled off easily and corrosion progressed significantly from the parts where the paint film was peeled off. In addition, in a corrosive environment on the outer surface of the can, corrosion of the iron progresses due to anode melting of the iron at the end surface of the sheared part of the plating original plate or the defective part of the plating, and rust occurs.
Alternatively, it was found that pitting corrosion occurs, and rust occurs due to corrosion of the steel base in the defective parts of the coating film or parts with the coating eaves, and pitting corrosion occurs, which deteriorates the corrosion resistance life. Therefore, in order to solve these problems, the present invention improves the corrosion resistance of the plating original plate itself by adjusting the steel composition of the plating original plate, and also improves the corrosion resistance between the Sn-based coating layer and the plating original plate. By reducing the couplet corrosion current, it suppresses the dissolution of the Sn coating layer or base metal due to anode corrosion in a corrosive environment, and prevents deterioration of corrosion resistance after painting, paint adhesion over time, and corrosion resistance in defective parts of the paint film. The present invention provides a method for producing a high-performance steel plate for containers with a Sn coating layer that prevents the deterioration of corrosion resistance due to pitting corrosion in defective areas of the coating layer, and further prevents the occurrence of rust from end faces, etc. . (Means for Solving the Problem) That is, the gist of the present invention is as follows: (1) In weight%, C: 0.15% or less, acid-soluble Al: 0.005 to 0.10%,
The amount of adhesion per side of a steel plate containing 1.5 to 11% Cr, with the remainder being iron and unavoidable impurities.
After applying a Sn coating layer of 300 mg/m ² or more, heat melting treatment is performed, and then a chromate-based coating layer is applied with a coating amount of 1.5 to 150 mg/m ² per side in terms of metal Cr amount. A method for manufacturing Sn-based steel plate for containers with excellent paintability and corrosion resistance. (2) In weight%, C: 0.15% or less, acid-soluble Al: 0.005 to 0.10%,
Contains Cr; 1.5 to 11%, and further contains Ti, Nb,
After applying a Sn coating layer with an adhesion amount of 300 mg/m ² or more per side to a steel plate containing 0.03 to 0.50% of one or more of Zr and V, with the balance consisting of iron and unavoidable impurities, Heat melting treatment is applied, followed by a coating amount of 1.5 to 150 per side in terms of metal Cr amount.
A method for producing Sn-coated steel sheets for containers with excellent paintability and corrosion resistance, characterized by applying a chromate-based coating layer of mg/m ² . It is in. (Function) The details of the present invention will be explained below. Molten steel melted in a melting furnace such as a converter or electric furnace is made into a slab through continuous casting, ingot making, or blooming.
After hot rolling, cold rolling and annealing process, C: 0.15% or less, acid soluble Al: 0.005-0.10%,
A plated original plate containing Cr; 1.5 to 11%, with the remainder consisting of iron and inevitable impurities, or a plated original plate containing Ti,
A plated original plate containing 0.03 to 0.5% of one or more of Nb, Zr, and V is used. In the corrosive environment in which Sn-coated steel sheets are used, the Cr content in the steel should be 1.5% or more, due to the combined effect with the Sn coating to improve corrosion resistance and paintability.
Preferably it is 3% or more. Figure 1 shows the measurement of the couple corrosion current between the Sn coating layer and the Cr-containing steel plate when the container was filled with a corrosion accelerating liquid.
The content is extremely small, ranging from 1.5 to 11%. on the other hand,
Figure 2 shows the measurement of the couple corrosion current between the Sn coating layer and the Cr-containing steel plate when the outer surface of the container was immersed in a corrosion-promoting solution.The couple corrosion current decreases as the Cr content increases. It is extremely small at 3% or more. As a result, in conventional steel sheets that contain Cr as an unavoidable impurity, the couple corrosion current between the Sn coating layer and the Sn coating layer is extremely large, resulting in coating layer defects and coating layer eaves defects generated during processing. On the inner surface of the container, the loss becomes significant due to the dissolution of the Sn coating layer due to sacrificial corrosion protection. Therefore, the present invention aims to prevent the corrosion resistance life from being reduced due to the dissolution of the Sn coating layer by adding Cr to the steel. In addition, even in a corrosive environment on the outer surface of the container, the corrosion rate of exposed areas of the base metal at the above-mentioned defects and end faces of the coating layer is remarkable, causing red rust and perforation corrosion.
Although this significantly reduces the corrosion resistance life of the Sn-coated steel sheet, it can be prevented by using a Cr-containing steel sheet such as the one of the present invention. As described above, when the steel is coated and used, the deterioration of the corrosion resistance life is caused by defects in the coating film that reach the base metal during processing and transportation, or at the end faces of the coating layer. In other words, in a corrosive environment such as the inner surface of a container where anode dissolution is significant due to the sacrificial anticorrosive action of Sn, the dissolution of Sn and the formation of corrosion products will cause paint film blisters (so-called blisters), and the corrosion of the paint film will also occur. The performance of the coating film deteriorates due to factors such as the tendency for the coating film to peel off when exposed for a long period of time. Also, Sn
The coating layer is a cathode (noble), but in a corrosive environment where the anode of the base metal is significantly dissolved, the coating film performance is unlikely to deteriorate, but it can significantly accelerate perforation corrosion from the defective parts of the exposed base metal, causing the paint film to deteriorate. Deteriorates later corrosion resistance. This kind of performance deterioration after painting is caused by Cr
This can be prevented by using a plated original plate containing steel. In general, no matter how strict the control is when manufacturing Sn-coated steel sheets, it is difficult to completely eliminate defects in the coating layer such as pinholes and imperfections. Layer defects are generated. At the same time, there are many situations where the end face of the Sn-coated steel plate is exposed to the base metal surface (for example, the welded part of a welded can, the scored part of a can lid, the end face of a crown, etc.). Therefore, the present invention uses a steel sheet containing Cr as an essential component, which significantly reduces the couple corrosion current between the Sn coating layer and the plating original plate, to prevent the plating defects and end faces of the Sn coated steel sheet, and the Sn
The dissolution rate of the coating layer is significantly suppressed. As a result, the corrosion resistance life of the Sn coating layer itself is increased, and
Combined with the effect of improving the corrosion resistance of the plating base plate, a Sn-based coated steel sheet with an excellent corrosion-resistant life is manufactured. This effect also improves the adhesion of the coating over time or the corrosion resistance after coating, even when the coating is used. On the other hand, if the Sn coating layer is more noble in potential (cathode) than the plating original plate, it will significantly suppress the priority and corrosion rate of the base metal in plating defects, end faces, etc. As a result, it suppresses the occurrence of perforation corrosion and red rust in areas where the bare metal is exposed, and has a significant effect of extending the corrosion-resistant life. In addition, when used as a coating, it suppresses pitting corrosion, suppresses the formation of corrosion products on the base metal, prevents coating peeling, and significantly improves coating adhesion and post-coating corrosion resistance. As mentioned above, the Cr content for obtaining such effects is 1.5 to 11%, preferably 3 to 9%. When the Cr content is less than 1.5%, Sn
The effect of reducing the couple corrosion current between the coating layer and the plating original plate cannot be obtained, and the effect of improving the corrosion resistance of the plating original plate itself cannot be obtained. On the other hand, when the Cr content exceeds 11%, the effect of improving the corrosion resistance of the plated original plate itself further increases, but the Sn
The effect of reducing the couple corrosion current with the coating layer cannot be obtained due to the corrosive environment, and it becomes difficult to obtain sufficiently good adhesion with the Sn coating layer, resulting in deterioration of weldability and workability. As mentioned above, the addition of Cr has a great effect in terms of corrosion resistance and coating performance, but in the present invention, the contents of C, acid-soluble Al, and other components are also limited for the following reasons. As the C content increases, more chromium carbide precipitates, which deteriorates the mechanical properties and corrosion resistance of the steel, and at the same time inhibits the uniform coating layer of the Sn-based coating layer. Therefore, the C content is 0.15% or less, preferably
Should be 0.10 or less. In the present invention, when adding Ti, Nb, etc., the C content is preferably 0.02% or less since it inhibits workability and uniform coverage of the coating layer due to precipitation of titanium carbide, etc. When the amount of Al (Sal, Al) remaining in steel is small, less than 0.005%, it is difficult to prevent the formation of bubbles due to oxidizing gas, which increases the incidence of surface defects in steel. This significantly increases the corrosion resistance of steel materials, and becomes the starting point for deterioration of the corrosion resistance of steel materials. In addition, excess acid-soluble Al exceeding 0.10% causes Al-based oxides to be scattered on the steel surface.
At the starting point of corrosion resistance deterioration or on the surface of the coating layer applied to the steel sheet, smudges, pinholes, etc. occur, impairing the integrity of the coating layer. Therefore, in the present invention, acid-soluble Al is 0.005
~0.1%, preferably 0.01-0.08%. In addition to the above-mentioned steel components, the present invention also includes Ti, Nb,
Cr contained in steel by combining one or more of Zr and V with 0.03 to 0.50% and combining with C.
This will further improve processability and corrosion resistance. When the content of steel components such as Ti is less than 0.03%, the effect of preventing chromium carbide precipitation and improving workability and corrosion resistance is small, and when the content exceeds 0.50%, the effect reaches saturation. In addition to being uneconomical, precipitation of these components tends to harden the material and deteriorate workability. The preferred content is 0.075-0.20%. If a steel plate composed of the above-mentioned composition components is used as is, it has superior corrosion resistance compared to conventional steel plates that contain unavoidable impurities such as Cr, but the corrosion resistance is not sufficient as a material for containers. No, no. That is, iron is leached out due to organic acids, moisture containing Cl ^- ions, etc. contained in the container, and the occurrence of red rust is also significant. In addition, the outer surface of the container may be exposed to corrosive atmospheres containing Cl ^- ions, high temperatures, etc.
When stored in high humidity conditions, red rust occurs in a relatively short period of time, and steel plates alone do not have sufficient corrosion resistance. Furthermore, even if the steel plate is directly painted, if it is exposed to a corrosive atmosphere for a long period of time, the corrosive aqueous solution that has penetrated under the coating will generate corrosion products on the steel plate, causing the coating to peel and deteriorating the coating performance. do. Therefore, in the present invention, a Sn coating layer and a chromate coating layer are applied to the plating original plate in order to impart the corrosion resistance and coating performance required for container materials. Therefore, steel sheets containing Cr as an essential component
When a Sn coating layer is applied, as described above, the couple corrosion current between the Sn coating layer and the plating original plate is significantly reduced. As described above, this effect significantly improves the corrosion resistance life and coating performance in a corrosive environment due to the color fastness improvement effect of the plating base plate and the combined effect with the Sn coating layer. The Sn coating method to obtain this performance improvement effect is not particularly stipulated. After cleaning and activating the surface of the steel plate, the Sn coating method is applied by electroplating, hot-dip plating, or vacuum evaporation. For example, in the electroplating method where a coating layer is applied, a ferrostane bath, a halogen bath, a borosilicate bath, etc. are used to apply a coating layer to both sides of the steel sheet by cathodic electrolytic treatment with the desired coating amount.
A Sn coating layer is applied. The amount of the Sn coating layer is
A coating amount of 300 mg/m ² or more is required per side.
That is, if the amount of Sn coating layer is less than 300mg/ ^m2 ,
The lack of uniform coverage increases the occurrence of unplated spots and pinholes, and although the coupled corrosion current between the plated original plate and the Sn coating layer decreases, the range in which anodic corrosion protection can be applied to the Sn coating layer on the inner surface of the container is limited. Therefore, it is difficult to prevent the melting of the base steel. Furthermore, even in a corrosive atmosphere where the Sn coating layer is cathodic, there are many exposed parts of the steel base, which promotes anodic corrosion protection of the base steel, increases the amount of dissolved steel, and increases the risk of pitting corrosion. Therefore, the Sn coating amount is 300 per side.
mg/m ² or more, preferably 700 mg/m ² or more. In particular, when the Sn adhesion amount is 700mg/ ^m2 or more, the end face produced by processing is affected by the covering effect due to fogging of the Sn coating layer.
It is particularly preferable because it further promotes the anticorrosion effect on end surfaces such as sheared surfaces and processed surfaces. Further, the upper limit of the Sn coating amount is not particularly specified, but from the point of view of economic efficiency, a coating amount of about 15 g/m ² or less, preferably about 7.5 g/m ² or less is sufficient. Furthermore, in the present invention, in order to further improve the performance, after providing the Sn coating layer, the temperature is increased from just above the melting point (231°C) of Sn to 300°C, preferably from 240 to 280°C.
The Sn coating layer is heated and melted at a temperature of °C. Through this treatment, the Fe-Sn alloy layer is combined with the plating original plate through an alloying reaction between the plating original plate and the Sn coating layer.
It is generated as an intermediate layer between Sn coating layers, and pinholes in the Sn coating layer are further reduced, so dissolution of the Sn coating layer due to Sn anode corrosion protection or iron dissolution from the plated original plate in the corrosive atmosphere of the Sn cathode is further suppressed. The corrosion resistance life of Sn-coated steel sheets is further improved.
This heating and melting treatment is not particularly specified, and may be the same as the conventional heating and melting treatment method for Sn-plated steel sheets. For example, heat melting treatment can be performed in a short time of 0.3 to 3 seconds at a heating temperature of 240 to 280℃.
The heating atmosphere is _N2 gas atmosphere, MiX gas atmosphere, or an aqueous solution of Sn phenolsulfonate.
Furthermore, coating is carried out in the air or in the above atmosphere by applying a flux such as an aqueous solution of Sn phenolsulfonic acid and phytic acid or an aqueous solution of ZnCl ₂ . In the present invention, a chromate-based coating layer is applied to prevent yellowing during storage and improve coating performance.
The amount of the chromate-based coating layer is regulated depending on its use and purpose, but for all purposes, the amount of the chromate coating layer should be in the range of 1.5 to 150 mg/m ² per side in terms of the amount of metal Cr. In other words, 1.5mg/m ² or more is sufficient to prevent yellowing during storage, and if it is less than 1.5mg/m ² , uniform coverage of the surface of the Sn coating layer is insufficient, and the oil applied afterwards Even with these combined effects, it is difficult to prevent yellowing during storage. In addition, to ensure performance after painting, Sn
It is necessary to further improve the effect of the chromate film on the surface of the coating layer, and the coating amount is 1.5mg/m ²
The amount is preferably 7.5 mg/m ² or more. In other words, when the chromate coating layer is 1.5mg/m2 ^or more, the uniform coverage of the chromate coating is improved,
The adhesion of the paint to the surface of the Sn coating layer further ensures paint adhesion through the chromate film. On the other hand, the upper limit of the amount of chromate coating is 150 mg/m ² or less, preferably 50.mg/m ² or less. When the amount of chromate coating exceeds 150 mg/m ² , the above-mentioned effect is saturated, and cracks are formed in the chromate coating due to processing, which also causes galling. In addition, chromate coatings are used to improve coating performance, especially paint adhesion over time when exposed to corrosive environments for long periods of time, and corrosion resistance after coating. A chromate coating layer consisting of is effective. The chromate film with this coating structure has a metal Cr layer with a coating amount of 1 to 30 mg/m ² per side, and a chromium oxide layer mainly composed of hydrated oxide in a range of 5 to 50 mg/m ² in terms of the amount of metal Cr. is preferred. The method of providing this chromate film layer is not particularly stipulated, and Cr ⁺⁶
Immersion treatment or cathodic electrolysis treatment is performed using chromic acid, chromate, dichromate containing ions, and an aqueous solution containing SO ₄ ^-2 ions and fluoride. For example, Na ₂ Cr ₂ O ₇ aqueous solution, CrO ₃
Chromate treatment with a hydrated chromium oxide layer as the main component is performed by immersion treatment in a -PO ₄ ^-3 aqueous solution or cathodic electrolysis treatment. In addition, when providing a chromate coating consisting of a metal Cr layer and a chromium oxide layer mainly composed of hydrated oxide, a CrO ₃ −SO ₄ ^-2 bath, CrO ₃ −Na ₂ SiF ₆ −
It is provided by cathodic electrolysis treatment using an NH ₄ F bath with adjusted current density. The chromate coating treatment for improving coating performance is applied to the products of the present invention after processing (for example,
A similar effect can be obtained when a surface cleaning treatment is performed after the Di molding process. (Example) Examples of the present invention will be described below. Using a steel plate with a steel composition whose Cr content was mainly varied as shown in Table 1, it was degreased using a degreasing bath containing 3% NaOH aqueous solution with 0.3% surfactant added, and after washing with water, a 20% H ₂ SO ₄ aqueous solution was applied. Current density at 50 °C using
After cleaning and activating the surface by anodic pickling for 1 second at 20 A/dm ² , followed by cathodic pickling for 1 second and water washing, the Sn-based coating layer and chromate shown in Table 1 are applied. A coating layer was provided and various performance evaluation tests were conducted. The performance evaluation was carried out using the following methods, and the performance evaluation results are shown in Table 1. As a result, the product of the present invention has extremely superior performance in terms of coating performance, corrosion resistance, end surface rust resistance, etc., as compared to comparative materials, and has extremely excellent properties as a material for containers. ●Evaluation test method Corrosion resistance targeting coating layer defects Using a 0.25 x 50 x 50 mm evaluation material, seal the end and back surfaces, put a scratch eave that reaches the base steel on the evaluation surface, and (1.5% citric acid + 1 .Five%
NaCl) in 400 ml of aqueous solution at a temperature of 50°C, 288
An immersion test was conducted in an _N2 gas aeration atmosphere with almost no oxygen present for several hours, and the amount of Fe eluted from the scratch eaves corresponding to the defective coating layer and the scratch eaves were evaluated. The corrosion resistance was evaluated based on the state of perforation corrosion in the eaves. The evaluation criteria were as follows. Fe elution amount/evaluation ◎……Fe elution amount per 1 cm ² of the evaluation material
Less than 2.5ppm ○...Fe elution amount ^per cm2 of evaluation material
2.5ppm or more - less than 5ppm △...Fe elution amount is 5ppm per ^1cm2 of the evaluation material
More than 7.5 ppm ×……Fe elution amount per 1 cm ² of evaluation material
7.5ppm or more Drilling corrosion resistance/evaluation ◎... Maximum drilling corrosion depth from the scratch eaves is less than 25% of the plate thickness ○... Maximum drilling corrosion depth from the scratch eaves is 25% or more of the plate thickness ~ 40 Less than % △... Maximum drilling corrosion depth from the scratch eaves is 40% or more and less than 60% of the plate thickness ×... Maximum drilling corrosion depth from the scratch eaves is 60% or more of the plate thickness Coating layer defect area After inserting a scratch eave that reaches the base steel using the same material evaluated for corrosion resistance (1.0% citric acid + 0.25
% phosphoric acid) in 400 ml of aqueous solution at a temperature of 50°C,
An immersion test was conducted for 288 hours in an N ₂ gas aeration atmosphere with almost no oxygen present, and the amount of Fe eluted was measured, the state of perforation corrosion from scratches was investigated, and the corrosion resistance was evaluated. The evaluation criteria were based on the following method. Evaluation of end surface rust After shearing the evaluation material with a thickness of 0.25 mm, the end surface was frozen (-15°C, 30 min) → high temperature and high humidity (temperature 49°C, humidity ≥98%,
60min)→Leave indoors (2 hours at 30℃) for 1
Evaluation was made by observing the number of cycles at which rust occurs on the sheared surface. The evaluation criteria were based on the following method. ◎...Rust occurs in 5 or more cycles ○...Rust occurs in 4 or more cycles △...Rust occurs in 3 or more cycles ×...Rust occurs in 2 or more cycles Plate Thickness Using 0.25mm evaluation material, create a processing evaluation material of 44φ x 8mm depth by cup drawing, with the sheared surface located at the bottom.
An outdoor exposure test was conducted to observe the occurrence of red rust from the end face, and to evaluate its location resistance. The evaluation criteria were based on the following method. ◎... Rust occurs in an exposure test of 7 days or more ○... Rust occurs in an exposure test of 5 or more days to less than 6 days △... Rust occurs in an exposure test of 4 days or more to less than 5 days Occurred during the test ×... Rust occurred during the exposure test for 3 days or more Performance evaluation targeting defective parts of the coating After coating the evaluation material with epoxy phenol paint to a thickness of 5μ, it reached the base metal. Add Scratch Eaves (1.5% citric acid + 1.5
%NaCl) aqueous solution at 27°C in a CO ₂ aeration atmosphere with almost no oxygen, the coating film centered on the scratched area was removed immediately after drying with cellophane tape. The performance of the paint film over time was evaluated on the inner surface of the container by investigating the state of paint film peeling from defective areas. The evaluation criteria were based on the following method. ◎...Almost no peeling of the paint film was observed at the scratched area. ○... Slight peeling of the paint film is observed at the scratched area. △...Paint film peeling at the scratched area is clearly observed. ×... Significant peeling of the paint film at the scratched area is observed. Paint film performance evaluation After coating the evaluation material with epoxy phenol paint containing Zn-free pigment to a thickness of 5.5μ,
100 pieces of 1mm x 1mm square base that reach the base metal
Make a mass and add it to a 1.5% citric acid aqueous solution.
After a 240-hour immersion test at 27°C in an _N2 aeration atmosphere with almost no oxygen, the cellophane tape was removed immediately after drying, and based on the condition of the coating film, the inner surface of the container was coated after aging. Membrane performance was evaluated. The evaluation criteria were based on the following method. ◎...Paint peeling area less than 5% ○...Paint peeling area 5% or more and less than 10% △...Paint peeling area 10% or more and less than 20% ×...Paint peeling area 20% or more Can lid Performance evaluation for the score processed part of the material Using the evaluation material with a plate thickness of 0.21 mm, the score remaining thickness
75μ image - after processing for open can lid, sealing the inner side, and immersion test at 50℃ in an aqueous solution (1.5% citric acid + 1.5% NaCl) for 120 hours in an oxygen atmosphere. Performance evaluation was performed. Coating film performance evaluation After the above evaluation test, cellophane tape was removed immediately after drying, and based on the peeling status, the coating film performance after time was evaluated by an accelerated test on the outer surface of the container. . The evaluation criteria were based on the following method. ◎... The peeled area of the paint film is less than 0.40 mm around the score processed area. ○... The peeled area of the paint film is 0.40 mm or more and less than 0.60 mm around the score processed area. △... The peeled area of the paint film is less than 0.40 mm around the score processed area. 0.60 mm or more to less than 1.0 mm at the center ×...The peeled area of the paint film is 1.0 mm or more around the score processed area Puncture corrosion evaluation After the above evaluation test, the perforation corrosion status of the score process area was investigated by cross-sectional observation. , its corrosion resistance was investigated. The evaluation criteria were based on the following method. ◎……Maximum drilling corrosion depth is 20 of the score residual thickness
Less than % ○……Maximum drilling corrosion depth is 20 of the score residual thickness
Less than % to less than 40% △……Maximum drilling corrosion depth is 40 of the score residual thickness
Less than % to less than 60% ×……Maximum drilling corrosion depth is 60 of the score residual thickness
% or more Evaluation of formability Using the evaluation material with a thickness of 0.28 mm, perform cylindrical drawing to a depth of 60 mm from a blank size of 150 mmφ, examine the occurrence of cracks and galling of the outer coating layer, and evaluate each A relative comparison was made between the materials to evaluate their moldability. The evaluation criteria were based on the following method. ◎...Very good ○...Good △...Poor ×...Very poor

【table】

【table】

【table】

【table】 [Brief explanation of drawings]

Figure 1 is a diagram showing the relationship between the amount of Cr added in steel and the coupler corrosion current (1.5% citric, O ₂ less atmosphere, Sn coating layer anode) for the can contents between the Sn coating layer and the content of the can. Figure 2 shows the amount of Cr added in steel.
FIG. 3 is a diagram showing the relationship between couple corrosion current (1% NaSO ₄ +0.35% NaCl aqueous solution, oxygen saturation, Fe anode) when targeting the outer surface of the container between the Sn coating layer and the outer surface of the container.

Claims (1)

[Claims] 1% by weight: C: 0.15% or less, acid-soluble Al: 0.005 to 0.10%, Cr: 1.5 to 11%, the balance being iron and unavoidable impurities. After applying a Sn coating layer of /m ² or more, heating and melting treatment is performed, followed by applying a chromate-based coating layer with a coating amount of 1.5 to 150 mg/m ² per side in terms of metal Cr amount. A manufacturing method for Sn-based steel plate for containers with excellent paintability and corrosion resistance. 2% by weight, C: 0.15% or less, acid-soluble Al: 0.005-0.10%, Cr: 1.5-11%, 0.03-0.03% with one or more of Ti, Nb, Zr, and V
0.50%, with the balance consisting of iron and unavoidable impurities, with an adhesion amount of 300mg/m2 ^or more per side.
After applying the coating layer, heat melting treatment is performed, followed by a coating amount of 1.5 to 150 mg per side in terms of metal Cr amount.
A method for producing a Sn-coated steel sheet for containers, which has excellent paintability and corrosion resistance, and is characterized by applying a chromate-based coating layer of m ² .