WO2003104528A1

WO2003104528A1 - Tin-plated steel plate and method for production thereof

Info

Publication number: WO2003104528A1
Application number: PCT/JP2003/006983
Authority: WO
Inventors: 中小路　尚匡; 重国　智文; 田中　匠
Original assignee: Ｊｆｅスチール株式会社
Priority date: 2002-06-05
Filing date: 2003-06-03
Publication date: 2003-12-18
Also published as: EP1518944B1; EP1518944A1; EP1518944A4

Abstract

A tin-plated steel plate which comprises a steel plate having a surface roughness of 1.5 μm or less in terms of Ra, a Fe-Sn alloy layer formed on the surface of the steel plate, a tin plating layer having a coating percentage of more than 99 % and a plated amount of 5 to 20 g/m² formed on the Fe-Sn alloy layer, and a chemical coating film containing P and Si formed on the tin plating layer, wherein the chemical coating film has an attached amount for P of 0.5 to 10 mg/m² and that for Si of 3 to 30 mg/m²; and a method for producing the tin-plated steel plate which comprises immersing a steel plate having the plating layer provided thereon in a chemical treatment fluid containing a phosphorus ion and a silane coupling agent or applying the chemical treatment fluid on the steel plate having the plating layer provided thereon, and then heating the resulting steel plate for drying.

Description

Tin-plated steel sheet and its manufacturing method

The present invention relates to a tin-plated steel sheet and a method for producing the same. In particular, the present invention relates to a tin-plated steel sheet requiring solderability and a method for producing the same. Background art

Conventionally, bonding using Pb—Sn alloy solder has been performed for home appliances such as audio products and personal computers. However, since Pb in the solder is harmful to the human body, the use of Pb has been regulated, and Pb-free soldering without Pb has been replaced. Conventionally, Pb-Sn alloy-plated steel sheets suitable for Pb-Sn solderability were used for chassis and component cases of home appliances, but in order to comply with Pb usage regulations, Pb was not used. There is a need for a new steel sheet having excellent free solderability. Furthermore, although the surface of conventional Pb-Sn alloy-plated steel sheets has been subjected to chromate treatment, there is a tendency in the consumer electronics industry to not use harmful hexavalent Cr, and new steel sheets for soldering have a chromate treatment. It is required that no processing be used.

A steel sheet for soldering that does not use Pb is disclosed in, for example, Japanese Patent Publication No. 6-999837 and Japanese Patent Publication No. 6-3334666. A film mainly composed of Sn-Zn, Zn_Ni, Sn-Ni and Fe-Ni is formed on a steel sheet, and a chromate film is formed on the film.

However, all of the steel sheets described in the above publication are inferior in Pb-free solderability because of using Zn, and are unacceptable to the home appliance industry because of having a chromate film.

Also, Japanese Patent Application Laid-Open No. 2001-32085 discloses a surface-treated steel sheet having a post-treatment film containing Si, which does not contain Cr on the surface of Sn or Sn alloy, and includes a steel sheet and a Sn plating layer. However, since it does not have an Fe_Sn alloy layer, the adhesion between the steel sheet and the Sn plating layer was poor, and there was also a problem with the Pb free solderability. As a technology related to chemical conversion treatment instead of chromate treatment for tin-plated steel sheets for cans, for example, Japanese Patent Publication No. 55-24516 discloses a technique in which a tin-plated steel sheet is used as a cathode in a phosphoric acid-based solution to perform DC electrolysis. A surface treatment method for a tin-plated steel sheet in which a conversion coating containing no Cr is formed on the tin-plated steel sheet is disclosed.In Japanese Patent Publication No. 1-32308, P or P is contained in the conversion coating. There is disclosed an electroplating tinplate for a seamless can in which a conversion coating not containing Cr and containing A1 is applied to the surface of a tin plating layer.

However, from a comprehensive viewpoint of performance such as paint adhesion and corrosion resistance, all of the conversion coatings described in the above publications are conventional chromate coatings formed using dichromic acid or a solution containing chromic acid. It cannot be said that the above performance is sufficiently obtained. Disclosure of the invention

An object of the present invention is to provide excellent wettability in Pb-free soldering, and excellent corrosion resistance and whisker property without using Pb and Cr, which are undesirable due to environmental problems. An object of the present invention is to provide a tin-plated steel sheet.

In order to achieve the above-mentioned object, the present invention provides a steel sheet having a surface roughness of 1.5 πι or less in Ra, a Fe—Sn alloy layer formed on the steel sheet surface, The present invention provides a tin-coated steel sheet having a coating rate of more than 99% and a coating weight of 5 to 20 g / m ² formed on the layer. The tin plating layer has a chemical conversion film containing P and Si as an upper layer. It said chemical conversion coating has a 0. 5~1 O mg P adhesion amount Zm ^2, S i adhesion amount of 3~3 O mg Zm ^2.

The surface roughness Ra is preferably 1 m or less.

It is preferable that the Fe—Sn alloy layer is an Fe—Sn alloy layer formed by a molten tin treatment.

The chemical conversion film is preferably a chemical conversion film formed using a chemical conversion treatment solution containing P and a silane coupling agent. It is desirable that the silane coupling agent has an epoxy group. Further, the present invention provides (a) a steel sheet provided with a tin-containing plating layer on both surfaces of the steel sheet, and (b) a steel sheet provided with the plating layer, comprising a phosphate ion and a silane coupling agent. (C) dipping or applying the chemical conversion treatment liquid, and heating and drying the steel sheet at 80 to 200 ° C. in a state where the chemical conversion treatment liquid is present on the plating layer of the steel sheet; d) A method for producing a tin-plated steel sheet, in which the dried steel sheet is washed with water, and (e) the washed steel sheet is washed and then dried again.

The chemical conversion treatment solution preferably contains a surfactant. BEST MODE FOR CARRYING OUT THE INVENTION

Tin-plated steel plate

Pb_Sn alloy solder contains 37% Pb and has a low melting point of 184 ° C. However, Sn-3.5% Ag-0.75% Cu alloy solder, which is the mainstream of Pb-free solder, has a high melting point of 219 ° C. Due to its high melting point, Pb-free solder has worse solderability than Pb-Sn alloy solder. For this reason, a steel sheet for soldering is required to have a higher soldering regeneration than before.

In addition, steel sheets for soldering are required to have corrosion resistance and whisker resistance. For this reason, the inventors conducted intensive research to solve the above-mentioned problems based on tin plating mainly composed of Sn which is a main component of Pb-free solder. As a result, a predetermined amount of tin-plated layer was formed on a steel plate having a surface roughness of 1.5 μπι or less with a length of < ' > It has been found that when a chemical conversion film containing P and Si is formed, all of the above performances can be satisfied.

More specifically, by forming a chemical conversion film containing an appropriate amount of P and Si on the upper layer of the tin plating layer, preferably with a chemical conversion treatment solution containing P and a silane coupling agent, excellent results are obtained. The wettability with Pb-free solder is obtained. In particular, this chemical conversion film is an effective protective film and suppresses the deterioration over time, so that excellent wettability with Pb-free solder is ensured even after the accelerated deterioration test. In addition, it has been found that this chemical conversion coating can provide excellent corrosion resistance and hoist resistance.

The tin-plated steel sheet of the present invention has a coating rate of 9 through the Fe—Sn alloy layer formed by the molten tin treatment on the surface of the steel sheet having a surface roughness of 1.5 μπι or less in Ra. A tin plating layer of more than 9%, and a chemical conversion film containing P and Si using a chemical conversion solution containing P and a silane coupling agent on the tin plating layer; leather The amount of P in the film is in the range of 0.5 to 10 mg / m ² , and the amount of Si in the film is in the range of 3 to 30 mg / m ² . The ratio (mass ratio) of SiZP in the chemical conversion film is preferably in the range of 5 to 30.

In addition, the tin-plated steel sheet is subjected to Sn plating on the steel sheet by a known electro-tin plating method, and then melted once by a molten tin treatment (reflow treatment) to form an Fe—Sn alloy layer at an interface with the steel sheet. Is formed as an intermediate layer, and it is preferable that the adhesion amount of the metal Sn layer after the formation of the Fe—Sn alloy layer is 5.0 to 20.0 g Zm ² .

Further, it is more preferable that the silane coupling agent has an epoxy group.

Hereinafter, the configuration of the present invention will be described in detail.

The tin-plated steel sheet according to the present invention has a tin-plated layer formed on the surface of a steel sheet having a surface roughness of 1 & 1.5 m or less through an Fe—Sn alloy layer formed by a molten tin treatment. This tin-plated layer is formed so as to cover almost the entire surface of the base, specifically, so as to have a coverage of more than 99%. If the tin plating layer covers the Fe—Sn alloy layer, that is, if the coverage in the surface area is less than 99%, not only sufficient solderability is not obtained, but also corrosion resistance becomes insufficient. is there.

In the present invention, after performing Sn plating on a steel sheet by a known electrotin plating method, the steel sheet is heated to a temperature equal to or higher than the melting point of Sn, and a molten tin treatment (also referred to as a riff opening one treatment) for temporarily melting the Sn plating is performed. Do. Electrodeposited stress is present in the Sn layer that has been electroplated, and needle-like crystals called whiskers grow from the Sn surface by the energy to release the electrodeposited stress. The growth of the whiskers causes a short circuit in the electrical circuit, so it is required that the whiskers do not grow. Once the electroplated Sn layer is melted, the electrodeposition stress is released, and whiskers are almost eliminated. Therefore, the tin melting treatment is essential in the present invention.

At the time of the molten tin treatment, the electroplated Sn becomes a molten state and becomes fluid, so that it flows into the concave portions of the steel sheet with roughness, and the Sn amount is large in the concave portions and the Sn amount is small in the convex portions. For this reason, the corrosion resistance is inferior in the steel plate roughness convex portion due to the decrease of the Sn content, and it is likely to be a starting point of the generation of heat. This tendency is more remarkable as the steel plate roughness increases. In the case of the Sn adhesion amount according to the present invention, the present inventors assume that the steel plate roughness is 1.5 μm in center line average roughness (R a). It has been newly found that the corrosion resistance deterioration at the convexity of the roughness does not become a problem if it is made as follows. Therefore, the roughness of the steel sheet should be less than 1.5 ιη at Ra.

The Fe—Sn alloy layer is formed at the interface between the steel sheet and the Sn layer by the molten tin treatment. This Fe—Sn alloy layer improves the adhesion between the steel sheet and the tin-plated layer, prevents the Sn layer from peeling off during processing, and forms a bond between the steel sheet and the solder when the Sn layer dissolves in the solder bath during soldering. It is extremely important to ensure wettability. Therefore, in the present invention, it is essential that the Fe—Sn alloy layer is interposed between the steel sheet and the Sn layer. In order to exhibit the above effects, it is preferable that the amount of the Fe-Sn layer to be formed is 0.05 g / m ² or more in terms of the adhesion amount. Since this alloy layer is harder and more alloyed than the tin-plated layer, it reduces the workability because it is an alloy layer. Therefore, it is necessary to minimize the amount of alloying generated. The Fe-Sn alloy layer is 1 g Zm ² or less. And more preferably 0.7 gZm ² or less.

When a steel sheet that has been subjected to Ni-based pretreatment such as Ni flash plating treatment or Ni diffusion treatment is used, the amount of alloy formed during the molten tin treatment is suppressed, so that these Ni pretreatments can be used as appropriate.

The adhesion amount of the unalloyed tin plating layer after the molten tin treatment is preferably 5 to 20.0 g / m ² . That's adhesion amount is less than 5. O gZm ² of the tin plated layer, not only can not be obtained wettability with sufficient Pb pretended one solder, corrosion resistance is inadequate. On the other hand, if it exceeds 20.0 g / m ² , the solder wettability and the corrosion resistance performance are sufficient, but the cost increases, which is not preferable. The amount of Sn adhesion can be measured by a coulometric method or surface analysis using fluorescent X-rays.

The main feature of the constitution of the present invention is that a chemical conversion film containing P and Si is preferably formed on the tin plating layer by using a chemical conversion treatment solution containing P and a silane coupling agent. and is to the P and Si deposition amount of each 0.5 5 10. scope of OmgZm ² and 3 to 30 mg Zm ² in said chemical conversion coating.

(1) 0.5 to 10 and the P content in the chemical conversion coat to the deposition amount. In the range of OmgZm ²

It covers the Sn surface as phosphate and acts as a binder between Sn and Si compounds to form a chemical conversion film. This binder effect is not easily affected by the structure of the steel sheet surface, has little change depending on the surface roughness, and is not affected by the surface roughness. P content is required to be in to 0.5 to 1 of 0. OmgZm ² range that deposition amount. If it is less than 0.5 mg / m ² , the conversion coating is insufficiently coated, and over time, Sn oxide grows on the Sn surface and solder wettability deteriorates. If it exceeds 1 0. OmgZm ^2, because the solder wettability contact is inhibition of solder and Sn layer is poor. The amount of P attached was measured by surface analysis using fluorescent X-rays.

(2) The Si content in the chemical conversion coat to be in the range of 3 to 3 Omg / m ² and its adhesion amount

In the present invention, the molten tin treatment is essential as described above. During the molten tin treatment, the electroplated Sn becomes a molten state and becomes fluid, flows into the recesses of the steel plate roughness which is the plating base plate, and the Sn amount increases in the recesses and the Sn amount increases in the protrusions. Is reduced. Also, when the surface roughness is large, the surface area of the mother plate becomes larger than when the roughness is small. For this reason, in order to obtain sufficient solder wettability and corrosion resistance, the amount of Si in the chemical conversion film is required to sufficiently cover the protrusions with a small amount of Sn. There (in R a generally 0. 1 μπι~ 5. 0 μια) roughness range of industrially produced by the steel sheet (plating base plate) In, Si content in the chemical conversion coating film is 3 Om _g / m ² or more For example, even in the case of the present invention in which the molten tin treatment is performed, sufficient solder wettability and corrosion resistance can be obtained. On the other hand, a smaller amount of Si is more economically advantageous, so a smaller amount of Si is preferable. If the surface roughness Ra of the steel plate as the plating base plate is small, the surface area of the steel plate is small and the amount of Sn in the convex part can be increased, so that the Sn surface can be coated even if the amount of Si in the conversion coating is smaller, Sufficient solder wettability and corrosion resistance can be secured. The present inventors have found that even when the attached amount of Si in the chemical conversion coating film is less than 3 Omg / m ^2, 'the surface roughness of the steel sheet is plated base plate by controlling the surface roughness of the plating base plate It has been found that by setting the degree of Ra to 1.5 μm or less, sufficient solder wettability and corrosion resistance can be obtained. The surface roughness of the steel sheet can be adjusted by, for example, controlling the roughness of the temper rolling roll in temper rolling performed when manufacturing a plated mother plate. That is, as described above, when the amount of Si in the chemical conversion film is small, it is necessary to reduce the surface roughness of the plating base plate. Even when the adhesion amount of Si in the chemical conversion coating and 3~ 3 Omg / m ^2, in order to satisfy the properties such as good solderability and corrosion resistance, the surface roughness of the steel sheet is plated base plate Ra less than 1.5 μπι It is necessary to. Further, even when the adhesion amount of Si in the chemical conversion coating film with 3 Omg / m ² or less, the adhesion amount of Sn plating, from the viewpoint of stability of 5 g / m ² or more and them if it forces the corrosion resistance as described above Is more preferably 7.5 g / m ² or more, even more preferably 10 g / m ² or more.

Here, the adhesion amount of Si to be contained in the chemical conversion coating, even if the surface roughness Ra of the steel sheet is plated base plate 1. below 5 m is less than 3m _g / m ^2, coating of the chemical conversion film is not adequate and, now solder wettability oxidized Sn is grown in Sn surface is poor over time, and to degrade corrosion resistance, it is necessary to be 3 mg / m ² or more. Also, if the steel sheet surface roughness Ra is because with the mother board is less than 1. 5 μπι, even if the adhesion amount of Si you contained in the chemical conversion coating was in greater than 3 Omg / m ^2, sufficient wettability Although corrosion resistance can be obtained, the amount of Si contained in the chemical conversion film should be 3 Omg / m ² or less in consideration of economy. The measurement of the Si adhesion amount was performed by surface analysis using fluorescent X-rays.

In the present invention, the Si contained in the chemical conversion film is preferably contained by the silane coupling agent contained in the chemical conversion treatment solution. The general chemical formula of the silane coupling agent is X-Si-OR ₂ . _r3 (OR: alkoxy group). Silane coupling agents form alkoxysilyl groups (Si-ORs) that are hydrolyzed by water to form silanol groups, which adhere to the OH groups on the metal surface by a dehydration condensation reaction to form a strong film. .

Examples of the silane coupling agent include 3-methallyl xypropynoletrimethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, N-2- (Aminoethyl) 3-Aminopropyl trimethoxysilane, N-2 (Aminoethyl) 3-Aminopropylmethyldimethoxysilane, 3-Aminopropyltriethoxysilane, フ -Feninole-3-Aminopropyltrimethoxysilane, 3-Mercaptopropylmethyl Toxoxysilane, 3-chloro mouth propyl trimethoxy silane, vinyl triethoxy silane, Burtris (2-methoxy ethoxy) silane, presence of an amino group, Ν-2 (aminoethyl) 3-amino propyl trimethoxy silane, Ν-2 -(Aminoethyl) 3-aminopropylmethyldimethoxy Orchid, 3-aminopropyl triethoxysilane, etc. can be used, but in particular, X-Si-OR ₂ in the general formula of the silane coupling agent. _r . 2- (3,4-epoxycyclohexynole) ethyl with an epoxy group at X Rutrimethoxysilane and 3-glycidoxypropyltrimethoxysilane are preferred.

Further, as a method of forming the chemical conversion film containing P and Si, for example, it is preferable to perform the conversion by phosphoric acid-based conversion treatment. In this case, the source of P in the chemical conversion treatment solution is ion phosphate It is more preferable to use metal salts such as phosphoric acid, sodium phosphate, aluminum phosphate, potassium phosphate, and the like, and Z or monohydrogen phosphate at a conversion of 1 to 80 g / l. . As a source of Si, it is preferable to use a chemical conversion treatment solution containing the above-described silane coupling agent, but in such a case, if the pH in the chemical conversion treatment solution is adjusted to a range of 1.5 to 5.5, the silane coupling agent may be used. The agent can be uniformly dissolved in the chemical treatment solution.

Note that the chemical conversion treatment liquid, Sn, Fe, Ni metal salts, for example, can be appropriately added metal salts such as _{_{_{SnCl 2, FeCl 2, NiCl 2}}} , SnS0 4, FeS0 4, NiS0 4. In this case, an oxidizing agent such as sodium chlorate or nitrite, or an etching agent such as fluorine ion may be appropriately added as a promoter. In addition, a surfactant such as sodium lauryl sulfate or acetylene glycol may be appropriately added for the purpose of improving the uniformity of the chemical conversion treatment solution.

The formation of a chemical conversion film using a phosphoric acid-based chemical conversion treatment may be performed by applying or dipping the above-mentioned chemical conversion treatment solution to a steel sheet and then drying it.

From the above, according to the present invention, it is possible to form a chemical conversion film containing P and Si in the above-mentioned appropriate range on the tin plating layer formed on the surface of the steel plate, or to obtain a steel plate surface having a proper surface roughness. By forming a chemical conversion film containing P and Si in the above-mentioned appropriate range on the tin plating layer formed on the substrate, all of the wettability with Pb-free solder, corrosion resistance, and resistance to hoisting force are achieved. We succeeded in satisfying the performance of this. Next, an example of a specific manufacturing method according to the present invention will be described.

After applying Sn plating to the cold-rolled steel sheet, it is heated and melted (reflowed) at a temperature equal to or higher than the melting point of tin (231.9 ° C) to form an intermediate layer made of an Fe-Sn alloy and an upper metallic Sn layer. Subsequently, chemical conversion treatment is performed by immersion treatment. After reflow processing In order to remove stannic acid generated on the surface of the PC ₉₈₃ , the cathode treatment of 1 C / dm ^{2 in} a 15 _g / l sodium carbonate aqueous solution may be performed.

The chemical conversion solution contains 1 to 80 g / l of phosphoric acid in terms of phosphate ions, 0.001 to 10 g / l in terms of tin ions, stannous salt, and 0.1 to 1.0 g / l of sodium chlorate. Use an aqueous solution to which 0.5 to 20.0 mass% of a silane coupling agent is further added.

The conditions for the chemical conversion treatment are preferably such that the temperature is 40 to 80 ° C and the treatment (immersion) time is 1 to 5 seconds. The tin-plated steel sheet immersed in the chemical conversion solution is dried at 80 to 150 ° C, then washed with water and dried with warm air.

Note that the above is only an example of the embodiment of the present invention, and various changes can be made within the scope of the claims. Example

Next, embodiments of the present invention will be described in detail below.

Examples 1-1 to 1-7

A cold-rolled steel sheet made of low-carbon steel or ultra-low-carbon steel with a thickness of 0.4 to 1.8 mm, with a Fe--Sn alloy layer on both sides, with 5.0 to 2.0 g / m ² per side A conversion coating was formed under the conversion treatment conditions shown in Table 1 on a tin-plated steel sheet on which a tin plating layer with an adhesion amount of was formed. Table 2 shows the composition of the chemical conversion film formed at this time.

Comparative Examples 1-1 to 1-6

For comparison, a tin-plated steel sheet in which at least one of the intermediate layer, the tin-plated layer, and the conversion coating is out of the proper range of the present invention was also manufactured.

The surface roughness Ra of the cold-rolled steel sheet as the plated mother plate used in the above-described present invention examples and comparative examples is the center line average roughness measured by “Surfcom 500 A” manufactured by Tokyo Seimitsu Co., Ltd. The amount of Sn in the tin plating layer and the amount of P and Si contained in the chemical conversion film were measured by X-ray fluorescence. The Sn coverage was measured by surface observation using a scanning electron microscope (10-field observation at a magnification of 50,000). table 1

Silane coupling agent (a): y-glycidoxypropyltrimethoxysilane (epoxy) Silane coupling agent (b): 2- (3,4-epoxycycloxyl) ethyltrimethoxysilane (epoxy)

Silane coupling agent (c): N-2- (Aminoethyl) 3-Aminopropyltrimethoxysilane (Amine series)

(Performance evaluation)

The tin-plated steel sheets of Examples and Comparative Examples were evaluated for Pb-free solder wettability, corrosion resistance, and resistance to hoisting force.

(1) Evaluation of solder wettability

As P free solder, Sn-3.5% Ag-0.75% Cu solder made by Senju Metal was used. The solder temperature was set to 245 ° C, and the zero-crossing time until the solder was wet was measured by the equilibrium method using a SAT-5100J device manufactured by Les Riki to evaluate the solder wettability. Using a 0.6 mm sample, the sample was exposed to a test tank at a temperature of 105 ° C and a humidity of 100% RH at a pressure of 1.22xl0 ⁵ Pa for 8 hours to accelerate and degrade, and then evaluated. mm / sec, immersion depth: 3 mm Zero crossing time was 3 seconds or less.

(2) Evaluation of corrosion resistance Three cycles of the cyclic corrosion test were performed, with one cycle consisting of 8 hours of salt spray (based on JIS Z 2371) and 16 hours of suspension of spraying, and the corrosion resistance was evaluated based on the area ratio (%) of reddish brown.

(3) Whisker test

The sample was bent at a bending radius of 5 mm, and after 500 thermal cycles at -25 ° C and 120 ° C, the surface of the bent portion was observed with a scanning electron microscope to observe the occurrence of whiskers. Whisker resistance was evaluated by the occurrence and length of whiskers. As is clear from the evaluation results in Table 2, all of Examples 1-1 to 1-7 were excellent in all properties of solder wettability, corrosion resistance and whisker resistance. On the other hand, Comparative Examples 1-1 to 1-6 all show poor solder wettability, corrosion resistance, and whisker resistance, which are not practical levels.

Table 2

Sn mesas layer Chemical conversion treatment layer Performance evaluation

Steel plate roughness Melted tin treatment Sn adhesion amount Sn coverage conversion treatment P adhesion amount Si adhesion amount Solder wettability Corrosion resistance Whisker resistance

Ra (/ m) (gZm ² ) (%) (m _E / m ² ) (mg / m ')' mouth cross time (sec) Red area area ratio (%) Length (m) Example 1 — 1 0.4 Yes 5.1 99.3 A 5.5 12.0 2.4 1 No occurrence Example 1 — 2 0.7 Yes 11.2 99.9 B 7.1 18.5 1.9 0 No occurrence 蓥 Example 1 — 3 1.0 Yes 16.8 99.9 C 3.9 6.5 1.6 0 No occurrence Room 1.2 Yes 19.8 9Θ.9 A 0.6 3.2 1.4 0 No emission Room application h 0.8 Yes 14.5 99.9 A 8.8 24.5 1.7 0 No emission Example 1 1 6 0.6 Yes 7.8 99.8 C 2.1 4.5 2.2 1 No emission Example 1 -7 1.4 Yes 9.3 99.9 B 1.6 4.0 2.1 3 No occurrence Comparative example 1-1 1.3 9.0 98.0 B 1.8 3.9 2.6 3 200 Comparative example 1 1 2 0.9 Yes 4.7 99.1 A 4.2 5.5 4.1 10 No occurrence Comparative example 1 -3 1.1 Yes 11.8 99.9 B 0.4 2.7 7.8 10 20 Comparative example 1 -4 0.6 Yes 5.1 98.0 C 0.5 2.9 8.1 25 20 Comparative example 1 1 5 0.8 Yes 9.3 99.9 A 12.0 27.0 6.8 0 No occurrence Comparative example 1 6 1.6 Yes 7.8 99.9 C 2.0 4.3 3.3 15 None

6983

13 Manufacturing method of tin-plated steel sheet

As a method of stably forming a chemical conversion film containing P and Si on the tin-based plating layer, we have been conducting intensive research, especially on a production method that can obtain a stable Si content of 3 mg Zm ² or more. As a result, the tin-plated steel sheet was immersed or applied in a chemical conversion solution containing phosphate ions and a silane coupling agent, and the chemical conversion solution was present on the plating layer of the steel sheet. It was newly found that a chemical conversion film could be stably obtained in a short period of time by heating to 80 to 200 ° C, drying it, then washing it with water and then drying it again.

It is more preferable to include a surfactant in the chemical conversion treatment liquid, since the film of the chemical conversion treatment liquid on the steel sheet during heating and drying becomes more uniform and a stable chemical conversion film can be obtained. Hereinafter, the configuration of the present invention will be described in detail.

The term “tin-based plated steel sheet” used in the present invention has a plated layer containing tin on one or both sides of the steel sheet. Examples of the tin-containing plating layer include Sn, an alloy layer containing one or more selected from Ni, Fe, Zn, Bi, and Cu, or a metal tin layer, and the metal tin layer. Examples include a plating layer formed between a steel sheet and an intermediate layer of a tin alloy layer containing one or two selected from the group consisting of Fe and iron, and the like, but are not particularly limited. Absent.

The present invention also includes a case where the intermediate layer includes two layers: a Fe—Ni alloy layer and a Fe—Sn—Ni alloy layer formed on the upper surface of the Fe—Ni alloy layer. At this time, the Fe / Ni alloy layer preferably has a Ni / (Fe + Ni) mass ratio in the range of 0.02 to 0.50. If the mass ratio of NiZ (Fe + Ni) is less than 0.02, it is composed of quadrangular prism-shaped crystals mainly composed of Fe--Sn alloy, which has many gaps and lowers the corrosion resistance.In addition, it is difficult to form a silane film continuously. This is because the effect of improving paint adhesion is small. On the other hand, if the Ni / (Fe + Ni) mass ratio exceeds 0.50, the crystalline state of the Fe—Sn—Ni alloy becomes sparse, the corrosion resistance of the steel sheet itself deteriorates, and the silane film is not formed densely. This is because the effect of improving paint adhesion is small. The present invention also includes a steel plate and a tin-containing plating layer which are appropriately plated with a base such as nickel plating.

As a method of forming a chemical conversion film containing P and Si, for example, it is preferable to carry out a phosphoric acid-based chemical conversion treatment. In this case, as a supply source of P in the chemical conversion treatment solution, It is possible to use 1 to 80 g / l of phosphoric acid, metal salts such as sodium phosphate, aluminum phosphate, potassium phosphate, etc. in terms of ion phosphate, and Z or monohydrogen phosphate. More preferred.

The reason why the preferred range in terms of phosphate ion in the chemical conversion treatment solution is 1 to 80 _g / l is that if it is less than lg / 1, paint adhesion and corrosion resistance are poor, and on the other hand, it exceeds 80 gl This is because the conversion coating is likely to have defects, and the paint adhesion and corrosion resistance are reduced. In addition, unreacted phosphoric acid remains and the paint adhesion may be reduced. In the chemical conversion treatment solution, a silane coupling agent is used as a source of Si. The general formula for a silane coupling agent is X—Si—OR ₂ . _{r 3} (OR: alkoxy group), where an alkoxysilyl group (Si—OR) is hydrolyzed by water to form a silanol group, which adheres to the OH group on the metal surface by a dehydration condensation reaction. The pH of the chemical conversion solution is preferably in the range of 1.5 to 5.5. That is, by adjusting the pH of the chemical conversion treatment solution to a range of 1.5 to 5.5, the silane coupling agent can be uniformly dissolved in the chemical conversion treatment solution.

Examples of silane coupling agents include 3-methacryloxypropyltrimethoxysilane, 2- (3,4-epoxycyclohexyl) ethy ^^ trimethoxysilane, 3-glycidoxypropyltrimethoxysilane, N-2 -(Aminoethyl) 3-aminopropinoletrimethoxysilane, N-2 (aminoethyl) 3-aminopropylmethyldimethoxysilane, 3-aminopropyltriethoxysilane, N-phenyl-3-aminopropyltrime Toxoxysilane, 3-mercaptopropyl methoxysilane, 3-chloropropynoletrimethoxysilane, butyltriethoxysilane, vinylinotris (2-methoxyethoxy) silane, presence of amino group, N-2 (aminoethyl) 3-aminopropyl Todimethoxysilane, N-2- (aminoethyl) 3-aminopropylmethyldimethoxysilane 3 - § Mino etc. propyl tri-ethoxy silane but can be used, X-Si-OR ₂ in particular in General I numerology type silane cutlet coupling agents. 2- (3,4-epoxycyclohexyl) ethyl tri, methoxy silane and 3-daricidoxy propyl trimethoxy silane, in which an epoxy group is present in X of _r3 , are preferred.

Note that the chemical conversion treatment liquid, Sn, Fe, Ni metal salts, for example, can be appropriately added metal salts such as _{_{_{SnCl 2, FeCl 2, NiCl 2}}} , SnS0 4, FeS0 4, NiS0 4. In this case As an accelerator, an oxidizing agent such as sodium chlorate and nitrite and an etching agent such as fluorine ion may be appropriately added.

It is more preferable to appropriately add a surfactant such as sodium lauryl sulfate or acetylendalcol for the purpose of improving the uniformity of the chemical conversion treatment solution.

The tin-plated steel sheet is immersed in the above-mentioned chemical conversion treatment solution at 40 to 80 ° C for 1 to 5 seconds, squeezed with a roll or the like to form a film of the chemical conversion treatment solution with an appropriate thickness, and then subjected to the chemical conversion treatment. The steel sheet is heated to 80 to 200 ° C and dried while the liquid is present on the steel sheet. In the heating and drying step, the hydrolyzed silanol group of the alkoxysilyl group (Si-OR) and the OH group on the metal surface promote the dehydration condensation reaction, so that the formation of the chemically converted skin film is performed stably. is there. Since the dehydration condensation reaction is slow only by immersion treatment, it is difficult to obtain an amount of Si in the film of 5 mg Zm ² or more.

Heating must be carried out while the chemical treatment liquid is present on the steel sheet. Therefore, the heating method that blows hot air, which is usually performed industrially, is not preferable, and infrared heating, induction heating, and radiation heating Is preferred.

The heating temperature must be 80-200 ° C as the steel sheet temperature. If the temperature is lower than 80 ° C, the rate of the dehydration / condensation reaction is low, the formation of the chemical conversion film becomes unstable, and a sufficient amount of Si cannot be obtained. Although it proceeds, it is not preferable because not only oxidation of tin on the tin-based plating surface occurs, but also heating energy is excessively consumed. '

Immediately after heat-drying the chemical conversion solution, wash it with water to remove unreacted silane coupling agent and phosphate ions. If unreacted silane coupling agent or sulphate ions remain on the surface, paint adhesion and corrosion resistance are inferior and must be removed by washing with water. Drying after washing with water may be performed by ordinary hot air drying.

The film of the chemical conversion treatment solution is formed on the plating layer by a method of applying the chemical conversion treatment solution using a roll coater that can easily control the thickness of the solution on the steel sheet, instead of performing the above-described immersion treatment. You may go.

From the above, according to the present invention, it was possible to stably form a conversion film containing P and Si on a tin-based plating surface.

Next, an example of a specific manufacturing method according to the present invention will be described. After applying Sn plating to the cold-rolled steel sheet, a heat melting (reflow) treatment is performed at a temperature higher than the melting point of tin (231.9 ° C), and the Fe-Sn alloy layer (intermediate layer) and the metallic Sn layer (upper layer) are treated. A tin-based plating layer consisting of two layers is formed, followed by chemical conversion by immersion. In addition, in order to remove the stannic oxide formed on the surface after the reflow treatment, the cathode treatment of 1 C / dm ² may be performed in a 15 g / l aqueous solution of sodium carbonate.

The chemical conversion solution contains 1 to 80 g / l of phosphoric acid in terms of phosphate ion, 0.001 to in terms of tin ion: L0 g / 1 stannous chloride, and 0.1 to: LO g / 1 sodium chlorate. Further, an aqueous solution to which 0.5 to 20.0 mass% of a silane coupling agent is added is used.

The conditions for the chemical conversion treatment are preferably such that the temperature is 40 to 80 ° C and the treatment (immersion) time is 1 to 5 seconds. After the chemical conversion treatment, the tin-plated steel sheet is squeezed with a ringer roll to control the film of the chemical conversion treatment liquid to a predetermined thickness, heated to 110 ° C by an infrared heating device, dried, and immediately washed with water. And dry with warm air at 35-90 ° C.

The above description is only an example of the embodiment of the present invention, and various changes can be made within the scope of the claims.

Next, embodiments of the present invention will be described in detail below.

Example 2-1 to 2-8

On both surfaces of the cold-rolled steel sheet consisting of thickness 0.1 to 2.0 mm low carbon steel or ultra-low carbon steel, to form a tin-based plated layer of the plated structure shown in Table 3 at a coverage of one side per 10 g / m ² Then, immersion or roll coating is carried out using the three types of chemical conversion treatment liquids A to C shown in Table 1, and after heating and drying, immediately wash with water and dry with warm air to form a chemical conversion coating. Was formed. Table 3 also shows the heating method and heating temperature when heating and drying to form a chemical conversion film.

Comparative Example 2-1 to 2-4

For comparison, tin-plated steel sheets were produced by a production method in which the method of forming the chemical conversion coating was out of the proper range of the present invention.

(Evaluation of chemical conversion film)

For each tin-plated steel sheet of Example and Comparative Example, the amounts of P and Si in the chemical conversion film were measured by X-ray fluorescence surface analysis. Table 3 shows the evaluation results.

(Evaluation of corrosion resistance)

Each of the tin-plated steel sheets of Examples and Comparative Examples was subjected to a salt spray test (according to JIS Z 2371) for 24 hours, and the corrosion resistance was evaluated based on the reddish area (%). Table 3 shows the evaluation results.

As is evident from the evaluation results in Table 3, in all of Examples 2-1 to 2-8, the amount of Si in the chemical conversion film was 3 mg Zm ² or more stably and showed good corrosion resistance. On the other hand, in each of Comparative Examples 2-1 to 2-4, the amount of Si in the chemical conversion film was less than 3 mg / m ² , indicating that it was not at a practical level.

Claims

The scope of the claims

1.3, a steel sheet having a surface roughness of 1.5 / m or less; a Fe—Sn alloy layer formed on the steel sheet surface; and a coating rate formed on the Fe—Sn alloy layer. A tin plating layer having an adhesion amount of 5 to 20 gZm ² exceeding 99%, and a conversion coating containing P and Si on the tin plating layer; 1 Omg / m P coating weight of ^2, tin plated steel sheet having a 3 i adhesion amount of 3 to 3 0111 _§ 111 ^2.

2. The tin-plated steel sheet according to claim 1, wherein the Fe—Sn alloy layer is a Fe—Sn alloy layer formed by a molten tin treatment.

3. The tin-plated steel sheet according to claim 1, wherein the Fe—Sn alloy layer has an Fe—Sn alloy amount of at most 1 g / m ² .

4. The tin-plated steel sheet according to claim 1, wherein the chemical conversion film is a chemical conversion film formed using a chemical conversion solution containing P and a silane coupling agent.

5. The tin-plated steel sheet according to claim 4, wherein the silane coupling agent has an epoxy group.

6. The tin-coated steel sheet according to claim 1, wherein the conversion coating has a mass ratio of Si ZP of 5 to 30.

7. Provide a plating layer containing tin on one or both sides of the steel plate,

The steel sheet provided with the plating layer is immersed in or coated with a chemical conversion treatment solution containing ion phosphate and a silane coupling agent,

In the state where the chemical conversion treatment solution was present on the plating layer of the steel sheet, the steel sheet was dried by heating to 80 to 200 ° C,

Wash the dried steel sheet with water,

After washing with water, dry again, Manufacturing method of tin-plated steel sheet.

8. The method for producing a tin-plated steel sheet according to claim 7, wherein the chemical conversion treatment solution contains a surfactant.