WO2008104611A1

WO2008104611A1 - Method for producing a metal panel and resulting metal panel

Info

Publication number: WO2008104611A1
Application number: PCT/ES2007/000596
Authority: WO
Inventors: Carlos Tapia De La Fuente
Original assignee: Recubrimientos Plasticos, S.A.
Priority date: 2007-02-27
Filing date: 2007-10-23
Publication date: 2008-09-04
Also published as: ES2310112B1; ES2547277T3; EP2130951B1; ES2310112A1; EP2130951A4; EP2130951A1; PL2130951T3; DK2130951T3; PT2130951E

Abstract

The invention relates to a method for producing a metal panel, in which a steel sheet having a low carbon content of between 0.1% and 0.2% and a thickness of between 0.1mm and 2mm is subjected to a first phase comprising polishing involving sanding with an aluminium oxide emery cloth at a sanding speed of between 4 and 20 meters/minute, and a subsequent second phase in which the polished sheet is covered by means of electrodeposition with a layer of a sacrificial metal selected from chromium, tin and zinc in a quantity of between 40 and 500mg/m2.

Description

"MANUFACTURING PROCESS OF A METAL PANEL AND METAL PANEL"

Current situation

The sharp increase in stainless steel consumption in recent years in various industries such as the appliance

(refrigerators, dishwashers, ovens, washing machines, microwaves, etc.), the elevator, the cold rooms in hospitality, and all kinds of decorative metal furniture have in turn produced a sharp increase in their price. This tension in the market, together with the search for new coatings that allow to protect against stains and corrosion sources to stainless steel while maintaining its aesthetics, has caused a continuous development of new products that can be grouped into two blocks :

1) The development of new transparent organic coatings applied on real stainless steel, which allow it to maintain its aesthetic characteristics, but at the same time protect the material against corrosion and allow the use of steels of lower alloy and lower cost (an example of this type of products It is our trademark Inoxplate, composed of a ferritic stainless steel, AISI 430, covered by a transparent adhesive and a transparent PET film)

2) The development of organic film-based coatings that mimic the design of stainless steel but applied to low-carbon steel cold rolled, electro-galvanized or galvanized, which allows to obtain a similar aesthetic and that provides adequate corrosion resistance for sectors described above. Problem to solve

The problem of the first type of solutions is that its price is still high, since the substrate is stainless steel, and the corrosion resistance necessary for many applications is not as high as that of this product. On the contrary, its great advantage is the metallic aesthetic and the possibility of different designs.

The problem with the second type of solutions is that its aesthetics is not as good as that of real stainless steel, it is not metallic, it is plastic. On the contrary, its corrosion resistance is sufficient for many applications and its price is much more competitive.

In conclusion, the route of action of the large steelmakers in the market has been to improve the aesthetics of a low carbon steel substrate using mechanical methods to simulate that obtained in stainless steel, and apply a series of organic layers to enhance corrosion resistance.

But the known products (metal panels) are not satisfactory since they do not even meet the specifications of the mentioned industrial sectors because:

- The drawing of the material according to ECCA T6 test is less than 8mm (value required in the appliance, elevator, etc.) (The adhesion of the organic coating is lower than that required) - The folding resistance according to the ECCA T7 test is 0.5-1 T (required value 0-0.5T) (The metal coating cracks and the organic cracks in turn)

- The corrosion resistance in salt spray chamber according to ECCA T8 test is less than 150 hours (requirement 300-

500 hours) (The material corrodes and cannot be used (ECCA is the European Coil Coating Association, and its test codes are those standardized for the sector and customers in other sectors, in addition to being correlated with ISO, EN and ASTM).

The applicant has studied the problem and, according to the tests in its facilities, considers that the main cause of the problem is that: If one acts mechanically on a metal substrate of low carbon steel coated with a sacrificial metal (for example, zinc, chrome, tin ....) that improves its corrosion resistance (zinc in galvanized steel, tin in the tinplate, or chrome in the chromeplated sheet), the sacrificial metal is damaged, and although a Organic coating the behavior of the material is not valid.

The solution proposed by the applicant consists in reversing the coating and satin phases over time, being arranged in the new process that is first satin and then coated.

Other problems and solutions will be explained later.

Specifically, the manufacturing process of a metal panel of the present invention is characterized in that a low carbon steel sheet between 0.10% -0.20% and thickness between 0.10-2.00mm is It submits: -TO-

a) in a first phase to a mechanical satin by sanding with aluminum oxide sandpaper being the sanding speed between 4-20 meters / minute, and then

b) to a second phase in which the satin sheet is coated by electrodeposition, with a layer of a sacrificial metal chosen from chromium, tin and zinc with an amount between 40-500mg / m ² .

It is also characterized in that the steel sheet already coated with the layer of the sacrificial metal is subjected to cleaning baths, the last one being carried out with water with a conductivity of less than 50 // S / cm.

With the solution of the invention is achieved:

1) The base substrate is a low carbon steel (0.10% -0.20%) cold rolled or galvanized or tinplate thickness (0.10-2.00mm), so the cost is reduced of the product

2) This substrate is mechanically satin in a process similar to that of stainless steel, achieving a design and aesthetic very similar to that of this steel

3) Subsequent to satin is coated with a thin layer of chromium, tin or zinc (40mg / m2 ~ 500mg / m ²⁾ having two functions. On the one hand it acts as a sacrificial metal to improve the corrosion resistance of the base metal, and on the other, it homogenizes the surface and gives it a brighter and metallic appearance, similar to that of stainless steel. By electrodepositing this thin layer of chromium after mechanical satin, it is possible to prevent the satin from damaging the sacrificial material and this is intact to be able to achieve good adhesion in the organic coating

With this new process it is possible to obtain the values required by customers in the aforementioned tests, and the applicability to such sectors of an aesthetic product similar to stainless, with mechanical and anticorrosive properties more than acceptable for the product, and with a much lower cost.

Process description

The process consists of the following phases:

1) The base substrate of the product is a low carbon steel (0.10% -0.20%) (its mechanical characteristics, elastic limit, breaking limit and elongation cover all the values of the standard), whose thickness It is between 0.10-2.00mm and is mechanically satinized by rollers or aluminum oxide sanding belts in any internationally approved standard finish (Grades between 60-320 or "Scotch Brite" finish) in a process whose range of speeds is 4-20 meters / min.)

2) The satin substrate is coated by electrodeposition with a sacrificial metal (chromium, tin or zinc) (it could be a mixture of them) in an amount between

40-500mg / m ² , obtaining a homogeneous, bright surface, and maintaining the satin design applied on the base substrate.

Metal of sacrifice is called metal that will be corroded by environmental conditions, instead of the iron (Fe) component of steel. 3) The material obtained is chemically treated by means of a series of cleaning, chemical degreasing and washing baths, the last bath with demineralized water having a conductivity of less than 50μS / cm.

4) The product is prepared to apply an adhesive on the outer face or exposed part, whose base resin can be polyester, polyurethane or acrylic, in a layer of 10-50 wet microns (before the curing process) and a polyester primer , polybutyral, epoxy or polyurethane by the inner face or part not seen. The material is introduced into an oven that can reach a metal temperature of 150-210 ⁰ C to cure the liquid organic coating, and a PET film is applied to its outlet, which seals the product.

5) (Optional phase) After cleaning baths, and optionally, a transparent water-based primer can be applied to further increase corrosion resistance in especially demanding products to deposit a thin layer of a material noble (for example, zirconium, titanium) (not exceeding 10mg / m ² ). This primer is cured in an oven that allows to reach a metal temperature of 100 ⁰ C to evaporate the water from the primer.

6) (2 ^to Optional phase) Optionally, a protective film can be placed after the application of the PET film to allow the client to manipulate and shape the steel without damaging the coatings.

The product resulting from this process presents substantial improvements over a conventional product, as follows from the following tests. Tests Conventional Product Product of the invention

ECCA T6

(Erichsen drawing) less than 6mm greater than 8mm

ECCA T7 Bending strength 0.5-1 T (substrate cracking) OT without cracking

ECCA T8

Corrosion resistance in

Salt spray chamber Less than 1 50h 300-500h ECCA T9

Immersion resistance

In water Less than 100h 500h

ECCA T13

Aging resistance Heat 20Oh at 120 ⁰ C 500h at 1 20 ⁰ C

Examples:

Example 1

Substrate: Cold rolled steel with low carbon content (0.1%) and thickness 0.50mm.

Satin: Satin process applied to the substrate mechanically by means of aluminum oxide sandpaper in a standardized grade called "Scotch Brite", which simulates the same stainless steel finish.

Chrome coating: Electrodeposition of chromium on the satin substrate with a layer equivalent to 140mg / m ² .

Chemical treatment: chemical cleaning by means of a series of degreasing and washing, the latter with demineralized water with a conductivity of less than 50μS / cm.

Application of liquid organic coating: application of a polyester adhesive (1 5 microns) on the exposed face and a epoxy primer (10 microns) on the unseen face. Curing of the product in an oven at a metal temperature above 150 ° C.

PET film application: application of a bright PET film.

Protective film application: application of a protective film (50 microns thick).

Example 2

Substrate: Cold rolled steel with low carbon content (0.12%) and thickness 0.40mm.

Satin: Satin process applied to the substrate mechanically by means of aluminum oxide sandpaper in a standardized grade and called "Grade 220" in the market, which simulates the same finish as stainless steel.

Chrome coating: Electrodeposition of zinc on the satin substrate with a layer equivalent to 5Omg / m ² .

Chemical treatment: chemical cleaning by means of a series of degreasing and washing, the latter with demineralized water with a conductivity of less than 50μS / cm. Application of a water-based primer to depose Titanium in an amount less than 10mg / m ² .

Liquid organic coating application: application of an acrylic adhesive (25 microns) on the exposed face and an epoxy-polyester primer (10 microns) on the unseen face. Curing of the product in an oven at a metal temperature above 150 ⁰ C.

PET film application: application of a dyed matte PET film Protective film application: application of a protective film (50 microns thick).

Example 3

Substrate: Galvanized steel with low carbon content (0.12%) and thickness 0.60mm.

Chrome coating: Electrodeposition of chromium on the satin substrate with a layer equivalent to 100mg / m ² .

Chemical treatment: chemical cleaning by means of a series of degreasing and washing, the latter with demineralized water with a conductivity of less than 50 // S / cm. Application of a water-based primer to depose Zirconium in an amount less than 10mg / m ² .

Liquid organic coating application: application of a polyester adhesive (15 microns) on the exposed face and an epoxy primer (10 microns) on the unseen face. Curing of the product in an oven at a metal temperature above 150 ⁰ C.

PET film application: application of a transparent matte PET film.

Claims

1 .- Manufacturing process of a metal panel, characterized in that a sheet of low carbon steel between 0.10% -0.20% and thickness between 0.10-2.00mm is subjected to:

2.- Manufacturing process of a metal panel, according to previous claim, characterized in that the steel sheet already coated with the layer of the sacrificial metal is subjected to cleaning baths, the last one being carried out with water of a lower conductivity at 50 // S / cm.

3.- Manufacturing process of a metal panel, according to previous claims, characterized in that after the cleaning baths a transparent primer based on water with a noble material is applied, to deposit a thin layer with an amount less than 10mg / m ² of zirconium or titanium, then proceeding to the evaporation of the water from the primer.

4. Process of manufacturing a metal panel, according to any of the preceding claims, characterized in that then apply an adhesive, on the outer face or exposed part, whose base resin can be polyester, polyurethane or acrylic, in a layer of 10-50 wet microns (before the curing process) and a polyester, polybutyral, epoxy primer or Polyurethane on the inner face or part not seen, introducing the metal panel in an oven at a metal temperature of 150-210 ⁰ C to cure the liquid organic coating, and at its exit a PET film is applied to seal the product.

5.- Metal panel, characterized in that it consists of a low carbon steel sheet between 0.10-2.00mm with a mechanically satin outer face, and a coating, on the satin outer face, of a layer of a sacrificial metal chosen from chromium, tin and zinc with an amount between 40-500mg / m ² .