JPH0241593B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a Sn-based plated steel sheet that has extremely low Fe elution from coating defects or coating end faces, etc. in a corrosive environment, and has extremely excellent corrosion resistance. (Conventional technology) Sn-plated steel sheets (tin plate) have traditionally had excellent appearance, corrosion resistance, workability, painting performance, and solderability.
It has outstanding suitability as a steel sheet for containers. However, the biggest drawback is that due to the soaring price of Sn metal,
The reason is that the price is extremely high. Therefore, efforts are being made to reduce costs by reducing the amount of Sn attached.
In that case, the problem is a decrease in corrosion resistance. The steel plate that solved this problem, for example,
There is a Sn-based coated steel sheet having a Ni-based base coating layer, as disclosed in Japanese Patent Application Laid-open No. 57-23091 and Japanese Patent Application Laid-Open No. 57-200592. These steel sheets 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. The steel plate (material) for Sn-based coated containers as mentioned above is
Although it is used in some places to take advantage of its properties, it is difficult to say that it has always achieved sufficiently satisfactory corrosion resistance. In addition, Sn-plated steel sheets are being considered as a material for alcohol-based fuel containers, but if the amount of Sn attached is reduced, problems such as red rust or perforation corrosion may occur from the plating pinholes during processing, so it is not always sufficient. It is said that satisfactory performance cannot be obtained. In order to solve this problem, a Ni-based base coating layer is applied to a steel sheet to which 0.2% to 5% of Cr is added to the plating original plate, as disclosed in Japanese Patent Application Laid-Open No. 59-126323. There is a Sn-based coated steel sheet with a Sn plating layer on the top layer. These steel plates have Cr in the steel, which has the effect of reducing the coupling current between the alloy layer with Sn containing Ni and the steel plate (plated steel plate), improving the corrosion resistance of the steel plate itself, making it an excellent product. Corrosion resistance can be obtained. However, the usage environment is becoming more severe, and the required performance tends to be more sophisticated. for example,
Regarding materials for cans, there are changes in the corrosive environment due to reductions in paint film thickness and diversification of contents.On the other hand, for fuel containers, there is a demand for longer lifespans of puncture-resistant corrosion, and changes in methanol, which is more corrosive than ethanol, are required. Application, deterioration of the corrosive environment such as the contamination of organic acids, etc. It cannot be said that the corrosion resistance performance is necessarily sufficient to meet these strict requirements. (Problems to be Solved by the Invention) In recent years, the characteristics of steel sheets for containers have been improved in response to the diversification of can manufacturing styles, the diversification of contents, and the consumer's preference for higher quality products. There is a demand for improved corrosion resistance (i.e., improved corrosion resistance life, etc.) by making thinner steel plates for containers that are less likely to rust or reduce container costs. For example, in response to the increase in the number of deformed cans such as closed-in cans, there is a particular need for contents containing Cl ^- ions to improve the corrosion resistance of parts that have undergone more severe processing than before. 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 can lid materials and the thickness of the score-processed parts, it is necessary to extend the corrosion-resistant life of the processed parts. At the same time, the score processing section is required 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. Furthermore, when a steel plate for iron-based containers is used for the tab of an easy-open-end can lid, corrosion resistance, particularly rust resistance, of the end face of the steel plate is required. Furthermore, the crown is required to have improved rust resistance on the end face of the crown. Furthermore, in the can manufacturing method, corrosion resistance of the welded end face portion is further required. In addition to the above-mentioned containers, it is desired to develop highly corrosion-resistant Sn-based coated steel sheets for alcohol fuels that are less prone to pitting corrosion at coating defects in processed or welded areas, both inside and outside the fuel container. ing. In conventional Sn-based coated steel sheets, depending on the type of contents, the Sn coating layer acts as a cathode, and Fe is removed from coating defects (pinholes, flaws due to processing, etc.).
There was a problem in that it leached out and induced perforation corrosion. On the other hand, on the external surface of the environment, the Sn coating layer acts as a cathode, and the couple corrosion current with the steel plate is also extremely large. As a result, Fe is removed from the coating defect or end face.
Elution and red rust occur, and drilling corrosion is likely to occur. The purpose of the present invention is to solve the above-mentioned conventional problems and provide a Sn-based coated steel sheet with extremely excellent corrosion resistance and corrosion-resistant life. Therefore, the corrosion resistance of the plating original plate itself is improved and the Sn coating layer is given anode corrosion protection ability, and pinholes and
The present invention provides a Sn-based coated steel sheet with fewer coating defects such as unmetallic spots. (Means for solving problems) That is, the gist of the present invention is as follows: (1) C: 0.10% or less, SolAl: 0.005 to 0.08%,
A steel plate with a thickness of 0.001
A highly corrosion-resistant Sn-based plated steel sheet with a ~1.5μ Ni-based base coating layer and a 0.5μ-thick or more Sn-based coating layer on top. (2) C; 0.10% or less, SolAl; 0.005 to 0.08%,
Contains Cr; more than 5% to 20%, and further contains Ti, Nb,
A Ni-based undercoating layer with a thickness of 0.001 to 1.5μ on a steel plate containing 0.03 to 0.5% of one or more of Zr and V, with the remainder being iron and unavoidable impurities.
A highly corrosion-resistant Sn-based plated steel sheet with a Sn-based coating layer of 0.5μ or more thick on top. (3) C; 0.10% or less, SolAl; 0.005 to 0.08%,
A steel plate containing Cr; more than 5% to 20%, with the balance consisting of iron and unavoidable impurities, with a thickness of 0.001 to 20%.
A method for manufacturing highly corrosion-resistant Sn-based plated steel sheets, in which a 1.5μ Ni-based base coating layer is applied, a Sn-based coating layer with a thickness of 0.5μ or more is applied, and then heated and melted. (4) C: 0.10% or less, SolAl: 0.05-0.08%,
Contains Cr; more than 5% to 20%, and further contains Ti, Nb,
A steel plate containing 0.03 to 0.5% of one or more of Zr and V, with the balance being iron and unavoidable impurities, and a Ni-based base coating layer with a thickness of 0.001 to 1.5μ and a thickness of 0.5 or more This is a method for manufacturing highly corrosion-resistant Sn-based plated steel sheets, in which a Sn-based coating layer is applied and then heated and melted. (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 method, and then hot rolled, cold rolled, and annealed to reduce weight percentage.
So, C: 0.10% or less, acid-soluble Al (SolAl): 0.005~
Steel plate containing 0.08%, more than 5% to 20% Cr, or 0.03 with one or more of Ti, Nb, Zr, and V
A plating base plate containing ~0.5% is produced. More than 5% Cr contained in the plated base plate prevents Fe elution from coating defects and perforation corrosion in the corrosive environment where Sn-based coated steel sheets are used, improving corrosion resistance. Figure 1 shows the situation when a corrosion accelerating liquid is filled in the container.
This is a measurement of the couple corrosion current between the Sn coating layer and the plating original plate, and the anodic corrosion protection ability of Sn becomes significantly higher when the Cr content is 3% or more, especially when the Cr content is 5% or more. In addition, Figure 2 shows the measurement of the couple corrosion current between the Sn coating layer and the plating original plate when the outer surface of the container was immersed in a corrosion accelerating solution.If the Cr content exceeds 5%, the Sn coating layer can be protected from anodic corrosion. becomes. In this way, when a steel plate containing Cr is used as a plating base plate, the sacrificial anticorrosion effect of the Sn coating layer prevents Fe elution, red rust formation, or perforation corrosion from the exposed portion of the base metal of the plating base plate. Ru. Therefore, the Sn-based coated steel sheet of the present invention has significantly improved corrosion resistance and corrosion resistance life. In general, no matter how strict the control is in manufacturing Sn-coated steel sheets, it is difficult to completely eliminate defects in the coating layer such as pinholes and imperfections, and processing defects may occur during use, which may cause damage to the base steel. A covering layer defect is generated. At the same time, there are many situations where the end face of the Sn-coated steel plate is used with the bare metal exposed (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 prevents corrosion of the base metal at coating defects and end faces of the Sn-coated steel sheet by using a steel plate whose Sn coating layer has Cr as an essential component and which can provide sacrificial corrosion protection for the plating base plate. significantly suppresses As a result, an Sn-based coated steel sheet with an extremely long corrosion-resistant life can be manufactured by improving the corrosion resistance of the plated original sheet. To obtain such an effect
As mentioned above, the Cr content is more than 5% to 20%, preferably more than 8% to 12%. Cr content is 5%
Below, the sacrificial corrosion protection effect of the Sn-based coating layer in a corrosive environment cannot be obtained, and if the Cr content exceeds 20%, the uniform coverage and adhesion of the Sn-based coating layer will deteriorate. In particular, steel sheets with a two-phase composition of γ phase and α phase with a Cr content of 11% or less are less likely to cause grain coarsening during steel sheet manufacturing, and when subjected to severe forming processes, they are prone to "hardening" called ridging. ``It has the characteristic that it is difficult to cause this phenomenon. Furthermore, in the present invention, C and acid-soluble Al
It is also necessary to regulate the content of (SolAl). As the C content increases, the amount of chromium carbide precipitated increases, which deteriorates the mechanical properties and corrosion resistance of the steel and at the same time inhibits the uniform coverage of the galvanized layer. Therefore, the C content is 0.10% or less. In the present invention, when Ti, Nb, Zr, V, etc. are added, 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 and the like. Al is the amount of acid-soluble Al (SolAl) remaining in the steel.
If the content is less than 0.005%, it is difficult to prevent the formation of bubbles due to oxidizing gas, which significantly increases the incidence of surface defects in steel, and becomes the starting point for deterioration of the corrosion resistance of steel materials. Also, excess acid-soluble Al exceeding 0.08%
In this method, Al-based oxides are dotted on the steel surface, which can be the starting point for deterioration of corrosion resistance, or cause blemishes, pinholes, etc. on the surface of the coating layer applied to the steel sheet, thereby impairing the integrity of the coating layer. Lose. Therefore, in the present invention, acid-soluble Al is 0.005
~0.08%. In addition to the above-mentioned steel components, the present invention also includes Ti, Nb,
Cr contained by containing 0.03 to 0.50% of one or more of Zr and V and combining with C in steel
This will further improve processability and corrosion resistance. If 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 will be small, and if the content exceeds 0.50%, the effect will be saturated. In addition, precipitation of these components tends to harden the material and deteriorate workability. The preferred content is 0.075-0.20%. If a steel plate with the above composition is used as is, it has superior corrosion resistance compared to conventional steel plates that contain unavoidable impurities such as Cr, but it is not suitable for container materials or fuel container materials. In this case, the corrosion resistance cannot necessarily be said to be sufficient. That is, the organic acids in the contents filled in the container,
Iron elution occurs due to moisture containing Cl ^- ions, and red rust occurs significantly. Furthermore, if the container's outer surface is stored in a corrosive atmosphere containing Cl ^- ions or in a high-temperature, high-humidity condition, red rust will develop in a relatively short period of time, and a steel plate alone will 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. There are drawbacks. Although the plated base plate made of the above-mentioned steel composition has relatively good corrosion resistance against gasoline or alcohol fuel, it may develop red rust or perforate due to moisture contained in the fuel or moisture containing Cl ^- ions. Prone to corrosion. In addition, in corrosive atmospheres where Cl ^- ions are present, such as on roads sprayed with road antifreeze salts (agents) or in areas with sea breezes, red rust and pitting corrosion are likely to occur. Therefore, in the present invention, taking into consideration the corrosion resistance, paintability, etc. required for container materials, fuel containers, etc., as described above, for the plating original plate,
Apply Sn coating layer. As described above, in a steel sheet containing more than 5% of Cr, the Sn coating layer provides a sacrificial corrosion protection effect for the plated original sheet. As a result, the steel plate of the present invention has excellent corrosion resistance and corrosion resistance life. Furthermore, in the present invention, a Ni-based base coating layer is provided between the surface of the plating original plate and the Sn-based coating layer. The Ni-based base coating layer forms a dense alloy layer with the upper Sn coating layer to reduce defects within the coating layer and improve corrosion resistance and adhesion of the coating layer to the original plate. This is because the Ni-based metal and the Sn coating layer have extremely excellent diffusion reactivity or wetting reactivity, both at room temperature and in the Sn-based coating treatment by heat melting treatment (melt treatment) or hot-melt plating method. By forming an alloy layer of Ni and Sn in this way, the sacrificial anticorrosion ability of the Sn coating layer is further strengthened. According to the present invention, the method of applying the Ni-based base coating layer and the Sn-based coating layer is not particularly specified, but for example, for the Ni-based base coating layer, the method of applying the plating stock solution, degreasing, pickling, etc. Electrical Ni plating or Ni alloy plating is performed after plating pretreatment, but a normal electroplating method may be used. Composition of Ni plating bath or Ni alloy plating bath,
Although the plating conditions are not particularly specified, the current density is generally 3 to 300 A/dm ² and the plating temperature is 80° C. or less. Examples of the composition of the Ni plating bath or Ni alloy plating and the plating conditions are as follows. (1) Ni plating composition; NiSO ₄・6H ₂ O 240g/ NiCl ₂・6H ₂ O 45g/
H ₃ BO ₃ 40g/ PH; 4.0 Current density: 15A/dm ² Plating bath temperature: 60℃ (2) Ni-Fe alloy plating composition Bath composition: NiSO ₄・6H ₂ O 240g/ NiCl ₂・6H ₂ O 45g/ FeSO ₄・7H ₂ O 60～80g/ H ₃ BO ₃ 40g/ PH; 1.5 Current density: 5～20A/dm ² Bath temperature: 50℃ (3) Ni-Sn alloy plating composition Bath composition: SnCl ₂・2H ₂ O 50g/ NiCl ₂・6H ₂ O 300g/ NaF 28g/ NH ₄ HF ₂ 35g/ PH; 2.5 Current density: 2.5 to 10A/dm ² bath temperature: 65℃ Also, a special example of Ni-Fe alloy base coating layer Alternatively, Ni electroplating may be performed using the composition and conditions as described in (1) above, and then heating and acid expansion treatment may be performed at a temperature of 550 to 900° C. in a non-oxidizing atmosphere. In particular, the method of applying a Ni-based base coating layer consisting of a Ni-Fe-based alloy diffusion layer by this heating diffusion treatment is as follows:
It is advantageous in the following points. The Cr-containing steel plate used in the present invention is generally easily oxidized during the annealing process. Therefore, prior to the annealing process, the steel plate as cold rolled (As Cold material) is degreased, pickled, and then Ni-based underplating is applied.
A method of performing heat diffusion treatment (temperature 500 to 900°C) simultaneously with annealing can prevent oxidation of the Cr-containing plating original plate surface during heating by Ni-based base treatment. At the same time, the processing strain of the As Cold material promotes mutual diffusion between the Ni base coating layer and the steel plate.
It is also excellent in that a Ni-Fe based diffusion base coating layer can be easily formed uniformly by short-time heat treatment. Next, the Ni-based base coating layer is made of Ni, Ni-Fe alloy,
Ni-Fe diffused layer, Ni-Sn alloy, Ni-Co alloy,
A Ni--P alloy or the like is used, but the thickness of this coating layer must be regulated to 0.001 to 1.5 microns, preferably 0.05 to 0.5 microns. If the thickness is less than 0.001 μm, the uniformity of coating the steel plate is insufficient, and the effect of reducing coating defects as described above due to the alloying reaction with the Sn coating layer cannot be obtained. Moreover, when the thickness exceeds 1.5μ, the effect is saturated and the relatively hard Ni−
A thick Sn-based alloy layer is generated and becomes the alloy layer during processing.
Cracks that reach the surface of the Sn-based coating are generated and corrosion resistance deteriorates. Furthermore, in the present invention, the steel plate coated with the Ni-based base coating layer is subjected to Sn-based coating treatment or further heat-melting treatment (melt treatment) after Sn coating, either as is or after being subjected to activation treatment such as pickling. In this case, the Sn coating conditions and the heating and melting treatment conditions after the Sn coating treatment are not particularly limited, and may be any conventional conditions. for example,

[Table] The test is carried out using fonic acid at a current density of 5 to 100 A/dm ² and a bath temperature of 30 to 60°C. In addition, the heat melting treatment was performed to improve the appearance by increasing the metallic luster of the Sn plating layer and to form a more uniform and dense alloy layer of the Ni or Ni alloy base coating layer and Sn, thereby further improving corrosion resistance. After Sn coating treatment, it is washed with water and then exposed to air or a non-oxidizing atmosphere (e.g. _N2 atmosphere) either as is or with an aqueous solution applied.
Inside, the Sn coating layer is melted at 240-350°C, preferably 250-300°C. The flux can be treated by dipping or spraying, for example, in plating baths and ferrostan baths, phenolsulfonic acid
2 to 10 g/(in terms of sulfuric acid) of SnSO ₄ is applied and melted. Regarding the Sn-based coating treatment, in addition to the electroplating method described above, other coating methods such as hot-dip plating method or vacuum evaporation method may be employed. The thickness of the Sn coating layer is 0.05μ or more, preferably
It is necessary to provide 0.15μ or more. If the thickness is less than 0.05μ, the uniform coverage of the Sn-based coating layer is insufficient;
The anti-corrosion function is lost relatively quickly due to the elution and consumption of Sn by the anodic corrosion protection of the Sn coating layer in the defective parts of the coating, so the corrosion resistance life is not necessarily sufficient. On the other hand, the upper limit of the thickness is not particularly defined, but it depends on the application, for example, 0.05 to 1.5μ for container materials, and 1 to 1.5μ for fuel container materials.
A coating thickness of 10μ is often used. Furthermore, when the present invention is used as a container material, it is often coated, but when stored for a long period of time, the appearance changes color due to the oxide film that forms on the surface of the Sn coating layer. There is a time. Therefore, in the present invention, after Sn coating treatment or heat melting treatment, water washing is performed to remove residues on the steel surface, and then chromic anhydride, chromate (ammonium chromate, sodium chromate, etc.) or heavy It is recommended to perform chromate treatment using a mixed aqueous solution of one or more chromates (ammonium dichromate, sodium dichromate, etc.) and an aqueous solution to which SO ₄ ^-2 ions, fluoride, etc. are added. . The treatment bath or treatment conditions for the chromate treatment are not particularly limited, but the treatment may be performed using, for example, the following chromate bath and chromate conditions. (1) Chromate bath composition; 60g/ CrO ₃ −0.3g/
SO ₄ ^- ₂ current density: 7.5A/dm ² bath temperature: 60℃ Chromate coating amount (Cr equivalent): 14.5mg/m ² (2) Chromate bath composition: 30g/sodium dichromate Current density: 10A/dm ² Bath temperature: 45℃ Amount of chromate coating: 6mg/m ² The present invention manufactured with the above component composition improves the corrosion resistance of the steel sheet (metsuki original sheet) itself by forming a uniform and dense alloy layer with the Sn coating layer containing Ni. By reducing the number of coating defects and ensuring the sacrificial anticorrosion ability of the Sn-based coating layer, the effect of improving corrosion resistance and corrosion resistance life is extremely significant. In other words, the present invention has a sacrificial anticorrosion effect by the Sn coating layer on Fe exposed parts such as flaws, coating end faces, etc., where coating defects are generated or due to processing, etc. Due to the effect of reducing the corrosion rate of the plating original plate itself, the amount of Fe elution is significantly reduced, and the risk of perforation corrosion in exposed Fe parts is significantly reduced, resulting in a remarkable improvement in corrosion resistance. Next, in the specification of steel components, it is natural that Ti, Nb, etc., and Mn, P, Si, S, etc., which are contained as unavoidable impurities in the steel manufacturing process at the current industrial level, are included. Similarly, it is preferable that the amount of Co, S, etc. contained as unavoidable impurities in the Ni or Ni alloy base plating layer is smaller. (Example) Examples of the present invention will be described below. Table 1 shows the results of various Cr-added steels with different steel compositions, which were subjected to pretreatment that is carried out in normal electroplating for degreasing and pickling, followed by plating with a Ni base coating and plating with a Ni-Sn alloy base coating. , Ni−Fe
Base coating plating by alloy electroplating and Ni
A predetermined amount of Ni--Fe base plating was performed using diffusion treatment after plating the base plating. Next, for coated steel sheets that have been subjected to Sn plating layer or heat melting treatment after Sn plating and chromate treatment by CrO ₃ - SO ₄ ^-2 cathodic electrolytic treatment, unpainted sheets and painted sheets, beverage can containers. The results of a corrosion resistance test are shown below. As comparison materials, Sn with a Ni-based base plating layer using aluminum-killed steel and rimmed steel without the addition of Cr.
This shows the corrosion resistance of plated steel sheets. Γ evaluation test method Corrosion resistance targeting coating/defects Using a 0.25 x 50 x 50 mm evaluation material, seal the end face and surface, make scratches that reach the base steel on the evaluation surface, and add (1.5% citric acid + 1 .5% NaCl)
An immersion test was conducted in 400 ml of an aqueous solution at a temperature of 50°C for 300 hours in a _N2 gas atmosphere with almost no oxygen. After the evaluation test, the parts were examined using a cross-sectional microscope and the corrosion resistance was evaluated based on the state of perforation corrosion in the flaws. The evaluation was performed based on the following criteria.

[Table] Corrosion resistance targeting coating/defects Using the same evaluation material, after making scratches that reach the base steel, 400ml of 1.5% citric acid aqueous solution was applied.
During the test, an immersion test was conducted at a temperature of 50°C for 480 hours in an _N2 gas aeration atmosphere with almost no oxygen, and the amount of Fe eluted was measured and the state of perforation corrosion from the scratch area was investigated. 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 0.24 mm, the end surface was subjected to (-5℃ freezing test 60 min) → high temperature and high humidity (temperature 49℃, humidity ≧98%, 60 min)
→Evaluation was performed by observing the number of cycles at which rust occurs on the sheared surface, with one cycle being left indoors (180 minutes at 30°C). The evaluation criteria were as follows. ◎…Rust occurs after 10 cycles or more 〇… 〃 8~9 〃 △… 〃 5~7 〃 ×… 〃 Occurs after 4 cycles or less Using evaluation material with a plate thickness of 0.25 mm, 44φ x 8 mm deep by cup drawing A material for evaluation of processing was prepared, the sheared surface was placed at the bottom, and the corrosion resistance was evaluated by observing the occurrence of red rust from the end surface in an outdoor exposure test.
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 days or more and within 6 days. △...Rust occurs in an exposure test of 3 days or more and within 4 days. ×...Rust occurs. Occurred in an exposure test within 2 days Performance evaluation targeting paint film defects Paint film performance evaluation After coating the evaluation material with epoxy phenol paint to a thickness of 5 μm, scratches reaching the base metal were added. , (1.5% citric acid + 1.5% NaCl)
Almost no oxygen exists in the aqueous solution at 27℃
After 96 hours immersion test in _CO2 vented atmosphere,
Immediately after drying, peel off the cellophane tape and investigate the peeling status of the paint film from the defective parts of the paint film, mainly the scratches, to evaluate the performance of the paint film after time on the inner surface of the container. Ta. The evaluation criteria were based on the following method. ◎...Almost no peeling of the paint film was observed at the scratched area. 〇…Slight peeling of the paint film is observed at the scratched area. △...Paint peeling is clearly observed at the scratch area. ×...Paint film peeling is significantly observed at the scratch area. Corrosion Resistance of Paint Film Defects The corrosion resistance of the above evaluation materials was evaluated by measuring the depth of perforation of the scratches after a 200-hour immersion test at 55°C in a CO ₂ aerated atmosphere. The evaluation criteria were based on the following method.

[Table] Performance evaluation for the score processing part of can lid material Using evaluation material with a board thickness of 0.21 mm, the score remaining thickness was 75μ
After processing for easy-open can lids, sealing the inner side, and heating in an aqueous solution (1.5% citric acid + 1.5% NaCl) in an oxygen atmosphere at 55°C.
Performance evaluation was performed after a 96-hour immersion test. Paint film performance evaluation After the above evaluation test, cellophane tape was removed immediately after drying, and based on the peeling status, the paint 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.

[Table] Evaluation of perforation corrosion After the above evaluation test, the state of perforation corrosion in the scored portion was investigated using a cross-sectional microscope to investigate its corrosion resistance. The evaluation criteria were based on the following method.

【table】

[Table] Evaluation of formability Using the evaluation material with a plate thickness of 0.28 mm, a cylindrical drawing to a depth of 60 mm was performed from a blank size of 150 mmφ.
The occurrence of cracks and the occurrence of galling in the outer coating layer were examined, and relative comparisons were made between the evaluation materials to evaluate their moldability. The evaluation criteria were based on the following method. ◎…Very good 〇…Good △…Poor ×…Very poor

【table】

【table】

[Table] Example 2 Table 2 shows the results when mainly changing the Cr content.
Using Cr-added steel, we perform pre-treatments such as degreasing and pickling that are normally carried out in electroplating, and then
Table 3 shows the results of a corrosion resistance test on alcohol-containing fuel for the present invention, in which a Ni-based base plating was performed, followed by a Sn plating layer or a heat melting treatment after the Sn plating. . As comparison materials, we showed the corrosion resistance of Sn-based plated steel sheets using aluminum killed steel and Ti killed steel without the addition of Cr or the like. Corrosion resistance of the outer surface of the Γ evaluation test (A) Corrosion resistance of the salt spray test Corrosion resistance of the outer surface of the fuel container after 480 hours of the salt spray test was evaluated. Evaluation material is 100×300
mm test specimens with cross-cut scratches reaching the base metal were used. The evaluation standard was the number of red rust occurrences in 300 gobans of 10 x 10 mm size for a test piece size of 100 x 300 mm, expressed as a percentage of 100. ◎... Red rust occurrence rate less than 5% 〃... 〃 5% or more and less than 25% △... 〃 25% or more and less than 50% ×... 〃 More than 50% (B) Corrosion resistance by CCT test Cycle corrosion test (CCT test)
Salt water spray (5% NaCl 35℃ x 4 hours) → Dry (70℃, humidity 60% 2 hours) → Wet (49℃)
Humidity 98% 2 hours) → Cooling (-20℃ x 2 hours) → Salt spray Corrosion resistance was evaluated by measuring the amount of decrease. ◎…Plate thickness reduction less than 0.25mm 〃… 〃 0.25 or more to less than 0.45mm △… 〃 0.45mm or more to less than 0.75mm ×… 〃 0.75mm or more (C) Using a 0.8 x 100 x 150 mm test piece, diameter 1 ~
After colliding and chipping a 2 mm Alundum against the surface of the coating layer of the test piece at a pressure of 1 Kg/cm ² for 10 seconds at a rate of 1.5 g per 1 cm ² , the above CCT test was conducted for 45 cycles to determine the amount of thickness reduction in the area where red rust occurred. was measured and evaluated according to the evaluation criteria in (B) above. Test on fuel container inner surface From a test piece with a blank size of 0.8 x 150 mmφ,
Punch diameter 75mmφ, wrinkle holding force 1T 75mmφ×
A cylindrical container with a height of 40 mm was created, filled with 100 c.c. of a corrosion accelerating solution for the following alcohol fuels, sealed and evaluated. (D) Gasohol target test (20% ethanol + 0.03% succinic acid + 0.15% 1% NaCl water + residual gasoline) solution, 3
Monthly evaluation test conducted. (E) Test on gasohol (70% methanol + 10% isopropyl alcohol + 0.03% formic acid + 0.3% 1.2% NaCl water + residual gasoline) A 3-month evaluation test using a solution. (F) 100% alcohol test (99% methanol + 0.01% formic acid + 0.5% of 0.99%
% NaCl aqueous solution) was used to carry out evaluation tests for three months, and the evaluations were made according to the following evaluation criteria.

[Table] Many occurrences
(G) Test for fuel containers and seam welds The inner surface coating layers corresponding to the inner surface of the fuel container are overlapped, and a 0.8 mm test material is used, and a 4 mm
Pressure force 400Kg with wide trapezoidal electrode, welding speed 2.5
Seam welding was performed at a welding time of ^2-2∞ m/min to create a test piece as shown in Figure 3.The test piece was filled with the solution shown below, and a plastic lid was placed on top for 3 months. Evaluation was made by observing the appearance afterwards. In FIG. 3, 11 indicates a welded portion, and 2 indicates a test liquid. Γ Gasohol target test solution (80% methanol + 5% isopropyl alcohol + 0.01% formic acid + 0.1% NaCl water 0.3% + residual gasoline) 3-month evaluation test Γ Evaluation criteria ◎...Red rust on the bottom and sides Occurrence rate Less than 5%〇…〃 5~less than 10%△…〃 10~less than 20%×… 〃20% or more (H) Test for gasoline (70% gasoline + 30% of 1% NaCl water) Accelerator solution for gasoline Evaluation test and implementation for 3 months using. The evaluation test used the evaluation criteria for the tests (D) to (F) on the previous page. (I) Solderability In order to evaluate the solderability of the Sn-Zn alloy (Sn≒80-90%) plated steel plate used for fuel container piping and the outer surface of this evaluation material, ZnCl ₂ -HCl flux and 60 Using %Sn−40%Pb solder,
The solder climbing property between the Sn-Zn alloy plating surface and the coating layer surface and the strength of the solder joint were measured, and a relative evaluation of the evaluation materials and comparative materials was performed comprehensively. ◎...Very good 〇...Comparatively good △...Slightly inferior ×...Very poor (J) Formability Blank size 0.8 x 500 x 500 mm, after applying lubricating oil, 150 x 150 mm square punch under the conditions of wrinkle pressing pressure 30T Square tube drawing was carried out using the method, and evaluation was made based on the limit of the drawing depth and the occurrence of galling on the outer surface of the square tube drawing material. ◎...No damage due to galling of the coating layer, very good moldability 〇...No damage due to galling of the coating layer, and fairly good moldability △...Depending on the degree of processing, some damage may occur due to galling of the coating layer ×... Extremely poor moldability

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【table】 [Brief explanation of drawings]

Figure 1 shows the measurement results of the coupling corrosion current between the Sn coating layer and the Cr content of the Cr-containing steel sheet in a (1.5% citric acid + 1.5% NaCl) aqueous solution (promoting solution targeted at the inner surface of the container). , Figure 2 shows the Sn coating layer and
Ni-Fe diffusion coating layer on Cr-containing steel sheet (heat treated at 780℃ for 60 seconds after 0.11μ Ni underplating on Cr-containing steel sheet)
1% NaCl + 0.3% of the Cr content of the steel plate with
Figure 3 is a diagram showing the measurement results of couple corrosion current for Na ₂ SO ₄ aqueous solution (promoting solution for external corrosion), and is an explanatory diagram of the test piece in the test for fuel containers and seam welds. 1: Welded part, 2: Test liquid.

Claims (1)

[Claims] 1 A steel plate containing C: 0.10% or less, SolAl: 0.005 to 0.08%, Cr: more than 5% to 20%, with the balance being iron and unavoidable impurities, and having a thickness of 0.001 to 1.5μ. A highly corrosion-resistant Sn-based plated steel sheet characterized by having a Ni-based base coating layer and a Sn-based coating layer with a thickness of 0.05μ or more applied thereon. 2 Contains C: 0.10% or less, SolAl: 0.005 to 0.08%, Cr: more than 5% to 20%, and further contains one or more of Ti, Nb, Zr, and V.
0.03 to 0.5%, with the remainder being iron and unavoidable impurities, a Ni-based base coating layer with a thickness of 0.001 to 1.5μ,
A highly corrosion-resistant Sn-based plated steel sheet, which is characterized by having a Sn-based coating layer with a thickness of 0.05μ or more applied thereon. 3 A steel plate containing C: 0.10% or less, SolAl: 0.005 to 0.08%, Cr: more than 5% to 20%, with the balance consisting of iron and unavoidable impurities, and a Ni-based base coating with a thickness of 0.001 to 1.5μ. layer,
After applying a Sn-based coating layer with a thickness of 0.05μ or more on top of it,
A method for manufacturing highly corrosion-resistant Sn-based plated steel sheets, which is characterized by heating and melting treatment. 4 Contains C: 0.10% or less, SolAl: 0.05 to 0.08%, Cr: more than 5% to 20%, and further contains one or more of Ti, Nb, Zr, and V.
0.03 to 0.5%, with the remainder being iron and unavoidable impurities, a Ni-based base coating layer with a thickness of 0.001 to 1.5μ,
After applying a Sn-based coating layer with a thickness of 0.05μ or more on top of it,
A method for manufacturing highly corrosion-resistant Sn-based plated steel sheets, which is characterized by heating and melting treatment.