JPS59196780A - Manufacture of single side-coated steel sheet - Google Patents

Abstract

PURPOSE:To inhibit the turning-round of a fluid for the pretreatment of a surface to be coated for the improvement of corrosion resitance, by forming the electric conductive coating film of specified resin which exhibits remarkable water-resisting power on the surface of a steel sheet to be handled as a back side. CONSTITUTION:After a steel sheet is washed with hot water 1, an aqueous solution is applied 2 onto a surface (b) to be uncoated by a roll coating method or the like, while holding said surface (b) to be uncoated downside. When an aqueous solution containing 5-50% singly polyethylene imine, silica sol-polyethylene imine or water-soluble acryl resin is used as said aqueous solution, an electric conductive coating film of 0.1-2.5mum in dried thickness is obtained. After the coating film is formed in this way, it is dried 3 at 40-300 deg.C to provide it with water-resisting power. Thereafter, phosphating treatment 4 and chromic acid sealing 5 are performed as pretreatment for coating. Paint is applied 6 onto only the surface (a) to be coated on which the precoating film has been formed by the pretreatment, to obtain a single side-coated steel sheet.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a single-sided coated steel sheet, which improves the corrosion resistance of the unpainted surface by forming an electrically conductive film without coating the unpainted surface during pre-painting treatment.

In recent years, in the field of electrical appliances and structural building materials, in-house painting of necessary parts has been stopped in order to rationalize processes, and sol-coating, which processes painted steel sheets into parts, has become popular. Conventionally, this coating has been applied to double-sided coated steel sheets that have a corrosion-resistant and weather-resistant color coating on the front side of the roof and colored zinc iron roots for walls, etc., and a rust-like service coating on the back side. Recently, the field of electric welders has been expanded to include the field of processing parts. However, with double-sided coated steel plates as mentioned above, the life membrane is a hindrance and cannot be used for electrical welding or soldering.For this reason, it is not used in the field of parts that undergo these processes. As a painted steel sheet, it has a corrosion-resistant and weather-resistant coating on the front side.
One-sided painting with un-candyed back side @ 4 Temporary use.

However, is it possible to paint the back side of a conventional single-sided coated steel plate using continuous coating using a roll coating method? Since the manufacturing process was discontinued and only the front side was painted, the unpainted front side was treated with phosphate treatment and chromic acid sealing before painting, and sometimes only chromic acid sealing was performed at temperatures below ℃. Therefore, the corrosion resistance of the back side is approximately 4 in terms of the height of white rust in the salt spray test.
It only lasted about 8 hours, and there was a drawback that rust occurred during storage if the product was held horizontally. Also, if crystals of phosphate-treated beams/crude salts are wound into a coil, they may be transferred to the coating on the front side, or they may build up on the forming roll during roll forming, and then be painted on the surface afterward. Another disadvantage was that the coating film was damaged during molding.

Therefore, in order to eliminate such drawbacks, the present inventors
An electrically conductive film made of one of polyethyleneimine, silica sol-polyethyleneimine/or water-soluble acrylic resin is formed on the unpainted surface of the ll+ to improve electrical weldability and solderability of the unpainted surface. We have developed a single-sided coated steel sheet that has corrosion resistance without sacrificing its properties.

As shown in Figure 1, the conductive film of this single-sided coated copper plate decreases rapidly when the film thickness exceeds 2.5 μm, and
If it is less than 0.1, the corrosion resistance may become neo-containing.
It was necessary to reduce the thickness to ~2.5μ. However, this coating thickness is within the range when a KiM coating is formed on a steel plate, and if there is an insulating glue/acid coating or a thick chromate coating between the coating and the steel plate base, the coating thickness will be 2.5 μm.
One piece I had to make thinner. For this reason, in order to prevent deterioration of corrosion resistance due to low film thickness, pre-painting treatment is usually performed to improve electrical conductivity. ,! It would have been better not to apply it to the unpainted surface where the shadow would form.

By the way, as for the production equipment for painted steel sales, the A-type pre-treatment is the Suzo-V type, and the casing is the 1-Lecote-Fi type. 1. However, even in the case of single-sided coated steel sheets, it is efficient to use this type of manufacturing equipment. In this case, is it the valley resin that forms the conductive film? This must be done by applying an aqueous solution containing 5 to 50% and then drying the plate at 40 to 300°C, so the application is done at the same time as the front side painting, and the drying process is done at the same time as the drying of the coating film. It is advantageous both in terms of equipment and control. But painted like this [''
When spraying the back side of the pre-painting treatment zone, there is a problem in that the pre-treatment liquid gets around to the back side and a pre-treatment film is partially formed on the unpainted surface, causing sticking to electric weldability. Ta.

In order to eliminate such variations in electric weldability, the present invention provides a method for producing a single-sided coated steel plate in which the pretreatment liquid does not penetrate into the uncoated surface.

The present inventors have conducted extensive studies on a method for producing a single-sided coated steel sheet that has an electrically conductive film on the unpainted surface and does not have a partial pre-treatment film on the unpainted surface due to penetration of the force. As a result, each film of polyethyleneimine, silica sol-polyethyleneimine, or water-soluble acrylic resin had a
They discovered that when dried at 00°C (board temperature), it exhibits remarkable water resistance and can withstand pre-painting treatment. And to prevent the pre-treatment liquid from getting around, should this film be formed before the pre-painting treatment? It has been confirmed that whether the one-way fuzzy spray method or the deep-spray method is used, the formation of a pretreatment film on an unpainted surface is effectively prevented.

In other words, the invention is based on a method for manufacturing a single-sided coated steel plate in which a corrosion-resistant and weather-resistant colored dense layer is formed on one side of the steel plate and the other side is left unpainted. Polyethyleneimide/silica sol-polyethyleneimide (7 lengths and 1 length) is water sprayed with water-soluble acrylic resin or resin (by drying with a cloth, a conductive film is formed) The present invention provides a method for manufacturing a single-sided coated steel sheet, characterized in that the coated steel plate is coated on one side, and then the one side is subjected to pre-painting treatment and then coated and applied.

The present invention will be specifically explained below with reference to Examples.

FIG. 2 shows the steps of the manufacturing method of the present invention, divided into painted and unpainted surfaces. First, the steel is washed with hot water. This hot water washing is not particularly necessary if the original plate to be coated, such as a cold-rolled steel plate or a plated steel plate, is clean. After washing with hot water, an aqueous resin solution is applied to the unpainted surface to form a conductive film. It is preferable to form this electrically conductive film by applying the aqueous solution by roll coating to the lower side of the unpainted surface, since this prevents it from going around to the painted surface. As an aqueous solution, polyethylene V/Imi/, silica sol-
When water-soluble gyt containing 5 to 50% of polyethyleneimine or water-bathable acrylic resin alone is used, the dry film thickness is 0.1
An electrically conductive film of ~2.5μ is obtained.

After forming the conductive film in this way, the
Dry at ℃ (rice temperature) and evaporate the water.

This drying imparts 1 level of water resistance to the water-permeable reaction force Mulberry K. In this way, it is water resistant. After forming, phosphate treatment and chromic acid sealing are performed as conventional pre-painting treatments. The pretreatment of γLl:) does not form a pretreatment film even if it is applied to a temporarily unpainted surface of steel, so it is only formed on the painted surface side. Then, paint was applied only to the painted surface side which was subjected to the pre-treatment film formation method f to form 5 pieces of IfJ coated steel plate.

Table 1 shows the manufacturing conditions for single-sided coated steel sheets by the above method,
The performance of the products manufactured under the manufacturing conditions of Comparative Example 3 and the manufacturing conditions of No. 3 AkofL et al. is shown below. Phosphate treatment 2 and chromic acid sealing were sprayed only on painted surfaces, and were not sprayed on unpainted surfaces. - Also, is each sample painted with primer paint? This was done by baking at 210°C for 30 seconds, and then baking the top coat at 230°C for 35 seconds.

The performance investigation of -J6 in Table 1 was conducted in the following manner.

(11 Salt water spray test JIS Z 2371Vc was carried out for 720 hours, and the rate of rust occurrence was evaluated according to the following criteria.

Evaluation point Rust area ratio (%) 0 4 l to 103
l l ~ 302
31-701
71 ~ 990 10υ (2) Humidity test Conducted for 720 hours in a humidity tester at 50°C and 98% RH,
It was evaluated using the same criteria as the salt spray test.

(3) Weldability test Welding current is 5 to 9 KA using 35° x 4 fin ψ electrodes.

Spont welding was performed under the conditions of a pressurizing force of 150 to 100 cycles and a current application time of 10 cycles, and the tensile force per spot after welding was evaluated according to the following criteria.

0250 Items peeled off with K9 or higher 0200~249 Items peeled off with KP △ ioo~l
One that peeled off at 99 Kp. One that peeled off at xloo less than 9. (4) For soldering, cut the Sb-Pb solder wire of 2 wires ψ in the order of 5. This? After it was placed on the film coated with chloride Franks, it was exposed once with a hand towel and its spread over 9 areas was evaluated according to the following criteria.

Evaluation symbol Spreading area (6 lines ψ or more △ 5 m ψ × less than 5 m ψ (5) Appearance Number of N cases of pre-painting treatment liquid or cases in which the pre-treatment film is unevenly formed ×, Pre-painting treatment The sample was evaluated as ○ if the liquid did not adhere to the sample and the pretreatment film did not form a bag.

As is clear from the third coating, according to the present invention, there is no formation of a pretreated film on an unpainted surface, and there is no deterioration in film performance due to phosphate treatment or chromic acid sealant.

As described above, although the manufacturing method of the present invention requires a heating device to form a permeable film, it is possible to obtain a single-sided zero-coated steel plate in which no pre-treated film is present on the unpainted surface.

Therefore, according to the present invention! :) The obtained single-sided ω steel plate has uniform conductivity on the wide end surface, and there is no d5 bonding.

[Brief explanation of drawings]

Figure 1 shows a hot-dip galvanized steel plate with a thickness of 0.5 mm on one side of which a conductive film of silica sol-polyethylene V-noimi was formed, at a current density of 7 KA and a pressing force of 150 to 9. Powering time 10
This is a graph showing the relationship between the current conductive film thickness, the tensile stiffness of each contact part, and the weld failure rate when spot welding is carried out under certain cycle conditions. FIG. 2 is a manufacturing process diagram of the non-inventive embodiment. Patent Applicant: Nisshin Steel Co., Ltd. Agent, Shindo, Full Procedural Amendment, May 1980, Lambda Incident Display, 1982 Patent Application No. 70789 2, Title of Invention: Process for Manufacturing Single-Side Coated Copper Plate 3 Amendment Relationship with the patent case Patent applicant address 3-4-1 Marunouchi, Chiyoda-ku, Tokyo Name
(458) NTR Steel Co., Ltd. Representative Director Okabe
Grant Meshin Nihonbashi Horidome Room 704 6. Column 7 of the detailed description of the invention in the specification to be amended, Contents of the amendment, page 3, 4th line from the bottom, 1...If it exceeds 2.5 μm, it will drop sharply. When the amount is exceeded, the tensile strength decreases rapidly and is corrected to ``.

Claims (1)

[Claims] A corrosion-resistant and weather-resistant colored coating is formed on one side of the steel plate-g
n. In the method for manufacturing a single-sided coated steel plate with the other side unpainted, first, the other side of the steel plate contains one of polyethyleneimine, silica sol-polyethyleneimine, or water-soluble acrylic resin. A conductive film is formed by applying an aqueous solution to a cloth and drying it, and then pre-painting and painting the one surface. A method for producing a single-sided coated steel sheet.