JPS61138567A - Production of heat resistant coated steel plate excellent in nonadhesive properties - Google Patents

Abstract

PURPOSE:To obtain a steel plate excellent in nonadhesive properties and press- moldability or the like by coating a mixture of tetrafluoroethylene resin and other heat-resistant resin on a steel plate, baking it and thereafter performing rolling screw-down. CONSTITUTION:The paint consisting essentially of tetrafluoroethylene resin and other heat-resistant resin such as polyphenylene sulfide and polyether sulphon is coated on the surface of a stainless steel plate or a plated steel plate and baked. Thereafter the coated film is roll-depressed to perform the smoothing and the rolling of the surface of coated film. Thereby, the heat resistant coated steel plate having the excellent nonadhesive properties, press- moldability and corrosion resistance can be produced.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention is a coated steel plate suitable for food heating processing tools such as so-called betaware, oven top plates, heating plates, etc. The present invention relates to a method for manufacturing a heat-resistant coated steel sheet that has high heat resistance, excellent non-adhesiveness, press formability, and corrosion resistance.

[Conventional technology and its problems]

So-called betaware (chambers), oven top plates, etc. for baking bread and cakes are generally used under high temperature conditions of around 200° C., and since they come into direct contact with food, corrosion resistance and heat resistance are highly required. In addition, it has a so-called non-adhesive property (am property) that does not cause scorching and is easy to remove stains.
It is preferable that there be.

Steel sheets with superior corrosion resistance include coated steel sheets with corrosion-resistant paints, such as steel sheets coated with epoxy resin for the undercoat and acrylic, polyester, vinyl difluoride resin, etc. for the topcoat, but the continuous heat resistance temperature of these coatings is It is only about 120 to 130°0 at most, and deterioration of coating film performance is inevitable when used in a high temperature range.

In addition, such conventional coated steel sheets have insufficient non-adhesive properties, insufficient press formability, and easily crack when drawn.

In addition, for example, frying pans and heating plates are made by applying fluororesin processing to steel plates, but the non-stick properties and corrosion resistance are insufficient, and since they are manufactured by press molding - resin processing, press processing of steel plates In this case, there is a problem similar to the above-mentioned problem of poor moldability.

[Means to solve the problem]

In view of these conventional problems, it is an object of the present invention to provide a method for producing a coated steel sheet that has a heat resistance of 200'O or more and has excellent corrosion resistance, non-adhesiveness, and press formability. Therefore, in the present invention, a paint mainly composed of a mixture of tetrafluoroethylene resin and other heat-resistant resin is applied to the surface of a stainless steel plate or a plated steel plate, and after the paint film is baked, the surface of the paint film is Its basic feature is that roll reduction is performed for the purpose of smoothing and rolling.

In addition, the present invention provides a two-coat, two-bake painted steel sheet in which a primer containing a heat-resistant resin of polyphenylene sulfide resin, polyether sulfone resin, or a mixture of polyphenylene sulfide resin and polyether sulfone resin is applied to the surface of a stainless steel sheet or a plated steel sheet. After coating and baking, a paint mainly composed of a mixture of tetrafluoroethylene resin and other heat-resistant resins is applied on top of the coating, and after the coating is baked, the purpose is to smooth and roll the coating surface. Another basic feature is that roll reduction is performed.

The present invention will be explained in detail below.

The present invention relates to a method for manufacturing a coated steel plate suitable for food heating processing products such as so-called betaware, and stainless steel plates and various plated steel plates can be used as the raw steel plate. The above-mentioned plated steel plate includes Zn plated steel plate, At
There are plated steel plates, Zn-At alloy plated steel plates, Ni-plated steel plates, Zn-Ni alloy plated steel plates, stainless plated steel plates, Cr-plated steel plates (so-called tin-free steel plates), and the like. Among these steel plates, tin-free steel plates are preferred when painting adhesion and durability under high temperature conditions are important. This steel plate is made by applying electrolytic chromate treatment to the steel plate to form a coating consisting of metallic chromium and chromium oxide, and has extremely good oxidation resistance at high temperatures, even in an atmosphere of around 400°0. Almost no oxidation.

In addition, it has superior paint adhesion compared to Zn-plated steel sheets and the like. In addition, if paint adhesion is important, use stainless steel plates (stainless steel plates and stainless steel plated steel plates).
, a Zn-At alloy plated steel sheet, a Zn-Ni alloy plated steel sheet, and a Ni-based plated steel sheet. These steel plates have better corrosion resistance than ordinary cold-rolled steel plates, Zn-plated steel plates, Sn-plated steel plates, etc., and also have excellent paint adhesion. Paint adhesion largely depends on the removability of the oxide film that forms on the surface of the steel plate (or the plated surface in the case of plated steel sheets), and peeling off of this oxide film is one of the main causes of inhibiting paint adhesion. In this respect, each of the steel plates described above has a property that the formed oxide film is less likely to peel off compared to other steel plates such as Zn-plated steel plates, and therefore excellent paint adhesion can be obtained.

In addition, when using a plated steel plate as the material, coating adhesion can be improved by forming a film by phosphate treatment or chromate treatment, for example, At
- It can be said that this method is particularly effective when the At coefficient is low in the case of Zn alloy plating.

Moreover, it is possible to add other elements to the above-mentioned At-Zn-based plating, Zn-N1-based plating, and N1-based plating in consideration of corrosion resistance and the like.

In the present invention, a heat-resistant paint having general heat resistance at high temperatures (200°0 or higher) is applied to the surface of such a raw steel plate.

Painting is done with one coat and one bake or two coats and two bakes. First, in the case of one coat and one bake, a paint whose main component is a mixture of polytetrafluoroethylene resin (PTF'g) and another heat-resistant resin is used as a heat-resistant paint. Other heat-resistant resins that can be mixed with PTF E include polyphenylene sulfide (pps), polyether sulfone (pas
) etc., PTFI + PPS paint.

Used in the form of PTFI + PES paint.

Tetrafluoroethylene resin has heat resistance and processing lubricity, so it has excellent press workability, and therefore also has excellent properties in terms of non-adhesion (<mu property).

Such coatings can be applied using continuous strip coating equipment under normal coating conditions.

After painting, steel plates are generally baked at a temperature of 350'O or higher.

In the case of 2 coats and 2 bakes, first a paint containing polyphenylene sulfide resin (pps), polyether sulfone resin (PES), or a mixture of these resins (pps + pgs) as a heat-resistant resin is applied as a primer. This primer paint is applied at high temperatures (20
It has normal heat resistance at temperatures above 0 (0 or more).
Examples of primers include the following types of paints:

(a) Solvent: 60-70% (NMP + Tsurupetz) Heat-resistant resin: 20-30% (PE3) Rust-preventing pigment: St, Cr, @1% of fat φ) solution
Agent; 65% (NMP + Tsurpets) Heat-resistant resin: 20~
30% (pas) Rust-preventing pigment; Inorganic pigment. After forming the coating film, such a primer is subjected to baking treatment. This baking temperature is lower than the baking temperature after topcoating.
Generally lζ is carried out in a temperature range of 200-400°0.

A top coat (finishing) is applied on top of the primer coating, but this paint is made of polytetrafluoroethylene resin (PTF) as a heat-resistant resin, as in the case of the one-coat, one-bake steel sheet mentioned above.
I) is an essential component, and the main component is a mixture of tetrafluoroethylene resin and other heat-resistant resins.

After painting, the steel plate is subjected to a second beta baking treatment in a heating furnace. This baking temperature is about 350-400°0.

Among the above two coats, plastic is the best.

It is preferable that the immersion paint contains a rust preventive pigment in order to place emphasis on corrosion resistance performance, and as the rust preventive pigment, conventionally used inorganic pigments such as strontium pigments are used. On the other hand, from the viewpoint of ensuring lubricity and non-adhesiveness during the press working process, the finishing paint does not contain anti-rust pigments that would impair these properties. However, pigments for luster (for example, human t) and the like may be included.

After the steel sheet is painted and baked as described above, it is rolled down with a roll for the purpose of smoothing and rolling the surface of the paint film. Even if the above-mentioned heat-resistant coating film contains tetrafluoroethylene resin in the as-baked state, its non-adhesiveness and press moldability are not sufficient, and its corrosion resistance is also not sufficient.

To address these problems, it has been found that by rolling down the heat-resistant coating film after baking, the coating surface is rolled and smoothed, and non-adhesiveness, press formability, and corrosion resistance can be greatly improved. . Figure 1 shows the roll reduction (reduction amount o, 5
% ) and without roll reduction (BHF: Maximum wrinkle pressing pressure that can be squeezed in g)
This is a comparison of the press formability of the die: 40
．． 9m-3R, punch: 40j11-4R, L, wrinkle presser plate: deep drawing test J with 40.5 da, and the wrinkle presser limit was measured by increasing the wrinkle presser pressure. In addition, non-adhesiveness has a correlation with press formability, and its performance can be evaluated by press formability. According to this, press formability (
It can be seen that the properties (and non-adhesiveness) were suitably improved.

One of the reasons why roll reduction improves press formability and non-adhesive properties is that the rough coating surface is smoothed, but another major reason is that Uniformity of the tetrafluoroethylene resin applied to the surface of the coating film is extremely effective for moldability and non-adhesion. In other words, the polytetrafluoroethylene resin on the surface of the coating film is microscopically unevenly distributed as it is baked, but the unevenly distributed polytetrafluoroethylene resin on the surface is stretched and made uniform by rolling pressure. and
In this way, the action of the tetrafluoroethylene resin uniformly spread over the coating surface improves repress moldability and non-adhesiveness.

Furthermore, according to Fig. 1, as the coating thickness increases, the press formability and non-adhesiveness tend to decrease.Therefore, when increasing the coating thickness to ensure corrosion resistance, It is particularly effective to ensure press formability and non-adhesiveness using rolls.

Also, II! due to roll reduction! The porous structure of the film is crushed and the coating film structure becomes denser, thereby improving corrosion resistance.

The roll reduction as described above is sufficient to smooth the surface roughness of the coating film and roll the resin on the surface.
It is not necessary to involve rolling of the raw steel plate. On the other hand, it is generally preferable to keep it to a level that does not affect the properties of the steel sheet material.

The steel plate thus obtained has a general heat resistance of 200'O or more, excellent press formability and non-stick properties, and also excellent corrosion resistance.

In the above-mentioned one-coat, one-bake steel sheet, after painting,
A method can be adopted in which the steel plate is heated in a heating furnace to evaporate the solvent, and then baked at 400° or more with an induction heater.

Heating using an induction heater allows for rapid heating, and the coating is heated from the inside, that is, from the induction-heated material steel side, and baking is performed, so the remaining solvent can be properly evaporated. In addition, uniform baking can be obtained, and thereby excellent paint adhesion can be obtained. If such heating with an induction heater is performed immediately after coating the paint without evaporating the solvent, the solvent will be trapped within the paint film due to rapid heating, which will affect the adhesion of the paint film. There is also the problem that the rapidly evaporated solvent condenses inside the heater and adheres to the board again. Therefore, the solvent is sufficiently evaporated in a heating furnace before heating with an induction heater.

In addition, the steel sheet obtained by the method of the present invention can be coated with edible vegetable oil such as cottonseed oil before or after roll rolling to give the coating film an aged coating, thereby improving press formability and non-adhesiveness. As a result, it is possible to completely eliminate the need for applying edible oil, which is particularly required to ensure non-stick properties, when used for the first time after being manufactured into a food heating processing tool.

〔Example〕

Painted steel plates were manufactured under the conditions shown in Table 1, and their press formability (non-adhesiveness) and heat resistance were examined under the following test conditions. The results are shown in Table 2.

・Press formability test (lubricity) Die: 4G, 91II-3R, punch: 401! l
-4R1 wrinkle presser plate: In a deep drawing test using 4G and 5jf, the wrinkle presser pressure was increased and the limit wrinkle presser pressure was measured.

・Heat resistance test OT B
By end+tape peeling.

◎: No peeling ○: Point peeling Δ: Peeling 11! Approximately 10% Corrosion resistance was investigated by a wet test at 98 degrees Celsius and 50 degrees Celsius. As a result, sample material (4)
On the other hand, red spot spots were generated in sample material (1) after 170 hours, whereas red rust spots were generated in sample material (1) after 170 hours.

〔Effect of the invention〕

According to the present invention described above, in addition to having general heat resistance at high temperatures, excellent press formability, non-adhesiveness,
Furthermore, it is possible to produce a coated steel plate having corrosion resistance, and it is possible to provide a steel plate particularly suitable for use in food heating processing products such as betaware, oven top plates, and heating plates at a low cost.

[Brief explanation of the drawing]

FIG. 1 shows the press formability of a steel plate subjected to roll reduction and a steel plate not subjected to roll reduction after coating with the heat-resistant paint used in the present invention in relation to the coating film thickness. Patent applicant: Nippon Kokan Co., Ltd. Inventor: Kazutaka Shimomura Ryodo Tatsu Jaume Shido
Takashi Yamachi, Patent Attorney, Sho Yoshihara, Three procedural amendments (voluntary), February 21, 1985, Commissioner of the Patent Office, Manabu Shiga (Examiner of the Patent Office)
1. Indication of the incident Showa No. 9, Waiting Request No. 2boo // No. 2,
Name of the invention Non-transfer M / 1tl = Inequality 42 resistance high meter sound threshold 2 Yo, Nomoto Ihimoto (412) Japan 4 tube (-1 set company 4
, Agent 5, the date of the amendment order, correct contents/In the specification of the present application, page 5, line 5, at the beginning of the text, it says ``Work supplies,'' and then adds ``etc.'' In the first line of page 6 of the second edition, the word "paint adhesion" is corrected to "corrosion resistance." 3. Line 20 of page 8 of the same book reads as follows (this has been corrected. It becomes rough, and due to this," is added. In the 3rd line of page 13 of Yodo 8, replace "J" with "After painting, it is possible to bake it in a heating furnace as it is, but in addition to this," The following is added between lines 11 and 12 on page 14 of the same book: ``The heat-resistant coated steel sheets obtained in the above manner can be used not only for food heating processing tools but also for building ducts, etc. Note that the method of the present invention can also be applied when the material plate is a metal plate other than a steel plate, such as a KT plate. Correct as shown in the attached sheet.

Claims (2)

[Claims] (1) Apply a paint mainly composed of a mixture of tetrafluoroethylene resin and other heat-resistant resin to the surface of a stainless steel plate or plated steel plate, and after baking the paint film, smooth the surface of the heavy film and roll it. A method for manufacturing a heat-resistant coated steel sheet with excellent non-stick properties, which is characterized by performing targeted roll reduction. (2) After applying a primer containing a heat-resistant resin of polyphenylene sulfide resin, polyether sulfone resin, or a mixture of polyphenylene sulfide resin and polyether sulfone resin to the surface of a stainless steel plate or plated steel plate, baking It is characterized by applying a paint whose main component is a mixture of ethylene chloride resin and other heat-resistant resins, and after baking the paint film, rolling it down with a roll for the purpose of smoothing and rolling the paint film surface. A method for manufacturing heat-resistant coated steel sheets with excellent adhesion.