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Factors Affecting the Printing Quality of Color Coated Steel Coils Part 1

HUNGTHAI METAL’s color-coated steel coil products have the characteristics of strong pattern texture, good quality, rich layers and bright colors, which can meet the production requirements of various patterns, and have multiple production lines.

  1. The quality of the printing roller
    The printing roller must have a suitable elastic coefficient, good inking performance, strong solvent resistance, suitable hardness and uniform hardness change in all directions, roundness and cylindricity must be accurate and the amount of deformation should be as small as possible.
  2. Selection of printing substrate
    Since the printing process adopts the transfer method, the requirements for the transfer roller and the printing substrate are higher. In the production process, a key item is the pressure adjustment of the transfer roller and the substrate. At the same time, the surface roughness and flatness of the substrate are required to be high. If the roughness is beaten or the thickness is uneven, the thickness of the film will be uneven, resulting in color difference.
  3. The choice of paint
    The type selection and color matching of each layer of paint is very important. Since the printing layer of the printed product is ink, in addition to the conventional requirements for each layer of paint, the printed product also requires high ink particle fineness and dispersion, good impact resistance, strong adhesion, heat resistance, light resistance, fluidity, Excellent drying, solvent resistance and processing resistance; at the same time, the selection of varnish is also strict. Because the quality of the paint will affect the surface quality and performance of the overall print.
  4. Coating film thickness selection control and viscosity selection
    Appropriately increase the ink viscosity, and on this basis, the dry film thickness should be reasonably controlled by the wet film thickness. In addition, pay attention to the matching relationship between the film thickness and color of each layer.
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Advantages and coating types of HUNGTHAI pre-painted steel coils

HUNGTHAI METAL is a professional manufacturer of color-coated steel coils, and can customize various specifications of PPGL/PPGI according to customer requirements. There are different kinds of high-quality color-coated steel coil substrates.

  1. Electro-galvanized substrate: the coating is thinner, and its corrosion resistance is not as good as that of hot-dip galvanized substrate;
  2. Hot-dip galvanized substrate: The thin steel plate is immersed in the molten zinc bath to make a layer of zinc adhere to the surface. This galvanized plate has good adhesion and weldability of the coating.
  3. Hot-dip Al-Zn substrate:
    The composition of this product is 55% AL-Zn, which has excellent anti-corrosion performance, and its service life is more than four times that of ordinary galvanized steel. It is a replacement product of galvanized sheet.
    Features:
    (1) It has good durability, and its corrosion resistance is longer than that of galvanized steel;
    (2) It has good heat resistance and is less prone to discoloration at high temperature than galvanized steel;
    (3) It has good thermal reflectivity;
    (4) It has processing performance and spraying performance similar to galvanized steel sheet;
    (5) It has good welding performance.
    (6) It has a good price-performance ratio, durable performance and very competitive price. Therefore, whether it is architects, engineers or manufacturers, galvanized steel sheets have been widely used in industrial buildings, steel structures and civil facilities, such as garage doors, gutters and roofs.
    Types of Color Coated Coils
    Polyester (PE)
    Good adhesion, rich color, wide range in formability and outdoor durability, medium chemical resistance, low cost.
    Silicon Modified Polyester (SMP)
    The coating film has good hardness, abrasion resistance and heat resistance, as well as good external durability and chalk resistance, gloss retention, average flexibility, and moderate cost.
    High Durability Polyester (HDP)
    Excellent color retention and UV resistance, excellent outdoor durability and chalk resistance, good film adhesion, rich colors, and excellent cost performance.
    Polyvinylidene Fluoride (PVDF)
    Excellent color retention and UV resistance, excellent outdoor durability and chalk resistance, excellent solvent resistance, good formability, dirt resistance, limited color, high cost.
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Quality Control of HUNGTHAI Color Coated Sheet Production Process

It is very important to ensure product quality for us. HUNGTHAI METAL has very strict quality inspection requirements and has been working hard to provide customers with perfect steel coils.

  1. Environmental Control
    As a high value-added product with both mechanical strength and decorative properties, the color-coated sheet has strict requirements on its surface. During production, a tiny dust or particle adheres to the surface or enters the paint, which will cause irreversible surface defects. Therefore, The entire coating production line should be absolutely clean, the ground should be brushed with dust-proof paint, the coating room should be managed in a closed manner, and the operators should strictly abide by the operating procedures.
  2. Substrate selection
    According to the purpose of the color-coated sheet, the color-coated substrate can be selected from cold-rolled sheet, electro-galvanized sheet, hot-dip galvanized sheet and galvanized aluminum alloy sheet, etc. Generally speaking, the dimensional accuracy and layout of color graphics products are completely determined by the substrate, and the unevenness cannot be changed during the production process, so the substrate needs to have good dimensional accuracy, and the strip edge should be free of burrs, jagged edges, and so on.
    It is required that the hot-dip galvanized strip needs to be small spangle or zero spangle, the surface is oiled and not passivated, and there should be no ungalvanized, zinc layer falling off, cracks, etc., and no blackboard and white rust will be produced during storage, otherwise it will cause the surface Defects will also reduce the adhesion of the coating and affect the performance of the color-coated board.
  3. Control of preprocessing
    The pretreatment includes cleaning and chemical treatment of the conversion layer. The purpose of the pretreatment is to increase the bonding strength of the coating and the substrate and increase the function of the coating. Therefore, the quality of the pretreatment directly affects the quality of the coating.
  4. Coating Control
    First of all, the surface of the roll is good, and secondly, it is mainly necessary to control the thickness and uniformity of the coating.
  5. Control of coating curing
    In order to completely volatilize the volume contained in the wet coating, the curing time, strip heating curve and strip PMT are mainly controlled during curing.

In the production process of color-coated sheets, from the input of raw materials to the packaging of products, corresponding inspections, measurements, tests and inspections must be carried out. So as to ensure that the entire process is completed according to the set process parameters.

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Pickling Defects and Prevention Part II
  1. The iron oxide scale is pressed in
    The reason is that in the production process, the iron oxide scale on the surface of the steel coil is not cleaned, and the iron scale fragments are formed by pressing into the surface of the strip steel during the rolling process. Such defects are difficult to remove, leave dents on the surface, and accumulate black particles that affect future production and product quality. Factories should strengthen the inspection of raw materials to prevent raw materials with such defects from entering the production process.
  2. Pickling bubbles
    The volume of the pickling bubbles varies, and it is not formed immediately during pickling, but only after heating.
  3. Pickling brittleness
    It is mainly manifested in the obvious reduction of the plasticity, toughness and crack resistance of the steel. Especially the strip steel with internal stress due to cold working deformation is more prone to this defect.
  4. Scratches
    This defect is mainly due to the presence of foreign objects on the surfaces of various rollers in the unit that are in contact with the strip, or the excessive wave shape of the strip causes the strip to contact the guide plate, causing scratches on the surface. We should always check the equipment to avoid such problems
  5. In order to prevent defects, the following points should be noted: 1. When the rolling process is in an abnormal state and causes low-speed operation or shutdown, acid should be released in time to prevent over-pickling defects in the strip. 2. Use acid and additives with qualified chemical purity, and the composition of pickling solution should be accurate. 3. Update the acid solution in time to prevent the content of impurities and iron salts from being too high.
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Steel coil Pickling Defects and Prevention Part 1


The strip steel after pickling with hydrochloric acid may have various defects. The reasons for various defects and how to prevent them are analyzed below. HUNGTHAI METAL has a complete quality supervision system and makes every effort to provide you with high-quality steel coil products.

  1. Excessive pickling
    Black spots composed of associated elements appear on the surface of the strip during pickling. To prevent excessive pickling, pay attention to reducing the stoppage of the process section, and pay attention to the acid release in time when the process section is stopped. The common method is to add a corrosion inhibitor to the acid solution, and the effect is good.
  2. Insufficient pickling
    Because the pickling is not fully completed, the surface of the strip steel becomes black and there is residual iron oxide scale, which is the most common defect in the pickling production process. In order to prevent this phenomenon, the temperature of the acid liquid should be guaranteed, and the vapor pressure of the paint should be guaranteed.
  3. Water Stains
    The cause of the water stains: the damage of the squeeze roller causes the residual rinsing water, or the ferric hydroxide is formed on the surface of the strip to form the trace of water. Such defects have an impact on the surface quality of the high-quality cold-rolled sheet.
    In order to prevent this problem, it is necessary to insist on using demineralized water for production, and replace the squeeze rollers regularly to ensure good working conditions.
  4. Corrosion holes
    After pickling, a little acid solution remains on the surface of the strip, or the strip is not completely dry after cleaning, or it stays in the high-temperature cleaning water for too long, causing the pickling solution to corrode locally, thus causing this defect.
    When such a defect occurs, the console needs to be notified in time to reduce the speed and prevent the strip from breaking.
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Prepainted galvanized steel coil PPGI

Advantages of HUNGTHAI color-coated steel coils
  1. What is color coated steel coil

1) Color steel coil, which is called color coated coil or color coated steel plate in our daily life. It is a kind of chemical transfer of strip steel that is continuously degreased on the production line through phosphating and so on. After the treatment process, the strip steel coated with organic paint is baked at high temperature. Usually, the surface of this steel plate has a bright and contrasting color. We also call this steel plate color steel plate. and color-coated panels.

2) Color steel coil is a composite material, which has both advantages of steel plate and organic material. It not only has the mechanical strength and easy forming properties of steel plates, but also has excellent decorative properties and corrosion resistance of organic materials.

3) The coating varieties of color steel coil can be divided into: polyester, silicon modified polyester, polyvinylidene fluoride, high weather-resistant polyester, clinker sol.

  1. The role of color steel coils

1) The coated steel plate is cured by using the leading particle anti-scratch coating coating technology at home and abroad, which is more than 5 times more scratch-resistant than the general construction plate, and can resist the scratch of sharp objects. Mainly used in garage doors, rolling shutter doors and windows, home appliances and other fields.

2) The special color-coated board can cooperate with the heating principle of solar polysilicon, has excellent decoration effect and maintenance effect, and is widely recognized by the solar energy industry. The main colors are pearl silver, golden yellow, printed LOGO board.

3) Colorful coated color steel coil is an extension product of hot-dip galvanized steel coil. Deep Processing. It is composed of cold-rolled steel coil base material, galvanizing and coating. Because of its excellent weatherability, formability and recyclability, it is increasingly becoming a substitute for wood. It adopts the leading particle anti-scratch coating coating technology at home and abroad for curing, and its anti-scratch performance is more than 5 times higher than that of general building boards, which can resist the scratches of sharp objects. Mainly used in garage doors, rolling shutter doors and windows, home appliances and other fields.

  1. The advantages of color steel coil

1) The weight is light, because the color steel plate itself is light in weight and convenient in transportation, which can save the construction period.

2) Environmental protection and saving, the prefab house made of color steel plate can be reused, which is environmentally friendly and saves money, no pollution and no noise.

3) High strength, because it is a steel structure, strong bearing capacity, compressive and bending resistance.

4) The appearance is smooth and easy to clean, the appearance of colorful galvanized steel plate is not rough, the anti-corrosion period is long, and it is suitable for repeated use.

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Pickling Principle of HUNGTHAI Color Steel Coil China

Pickling is HUNGTHAI Metal’s one of the important steps in making cold rolled steel coil, we provide you with high quality cold rolled steel coil.

The scales of iron oxide formed on the surface of the strip are insoluble in water, and when they are immersed in acid or sprayed on the surface, they undergo a series of chemical reactions with the acid. Due to the loose, porous and cracked properties of the iron oxide scale on the surface of carbon structural steel or low-alloy steel, and the repeated bending of the iron oxide scale on the pickling unit, these pores and cracks are further increased and enlarged, so the acid solution is in contact with While the iron oxide scale reacts chemically, it also reacts with the steel through cracks. Therefore, the pickling principle can be summarized into the following four aspects.

1. Dissolution
Various paste oxides in the iron oxide scale on the surface of the strip are dissolved in the acid solution to generate ferric and ferrous chlorides or sulfates that can be dissolved in the acid solution, thereby removing the iron oxide scale from the surface of the strip. This effect is generally called dissolution.

2. Mechanical peeling effect
In addition to the various oxides of iron, the iron oxide scale on the surface of the strip is also mixed with some metallic iron, and the iron oxide scale is porous, so the acid solution can pass through the gaps in the iron oxide scale. and produce a lot of hydrogen. The expansion pressure generated by this part of the hydrogen can separate the iron oxide scale from the surface of the strip. We call this reaction mechanical exfoliation.

3. Osmosis
The acid solution enters through the gap of the iron oxide scale and reacts with FeO. Since FeO and Fe2O3 are easy to react with the operator, the phenomenon that the iron oxide scale falls off due to the dissolution of the lower FeO in the acid occurs. This phenomenon is called osmosis.

4. Reduction
When metallic iron reacts with acid, hydrogen atoms are first produced. Part of the hydrogen atoms combine with each other to form hydrogen molecules, which promotes the separation of the iron oxide scale. The other part of the hydrogen atoms reduces the oxides and salts of high-valent iron to low-valent iron oxides and salts that are easily soluble in acid solutions by virtue of their reducing power.

Hungthai metal have a complete quality supervision system and professional production equipment, and our goal is to provide all customers with the highest quality steel coils.

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HUNGTHAI Different Kinds of Hot-Dip Galvanized Sheet

The production process of hot-dip galvanized strip is composed of degreasing, recrystallization annealing, hot-dip galvanizing, leveling and passivation oiling. HUNGTHAI is a professional steel manufacturing in china enterprise, galvanized steel coil exporter china and galvanized steel coil manufacturer.


Hot-dip galvanized sheets can be classified according to different rules.

  1. According to processing performance: general purpose, mechanical occlusion, stamping, deep drawing, special killed steel deep drawing, non-aging deep drawing, etc.
  2. According to the substrate: it can be divided into two categories: hot-rolled galvanized sheet and cold-rolled galvanized sheet. Hot-rolled galvanized steel sheets are mostly used for construction boards with low requirements, and cold-rolled hot-dip galvanized steel sheets are more widely used.
  3. According to the weight of the zinc layer; the galvanized steel sheet is suitable for anti-corrosion purposes, and the weight of the zinc layer should be adapted to the requirements of the customer.
  4. According to the surface structure: HUNGTHAI‘s products have four kinds of spangles: Regular Spangle, Small Spangle, Large Spangle, Zero Spangle.
    Regular Spangle The diameter of the spangle is generally greater than 4mm, and it is used for commercial purposes such as civil or construction.
    Small Spangle is usually less than 4mm in diameter, Small Spangle is usually used as the substrate of color coated board, or various containers, household appliances, electrical equipment casings, etc.
    Zero Spangle is invisible to the naked eye, with a diameter of less than 1mm, and is mainly used in automobile manufacturing, home appliances or color-coated substrates.
  5. According to the surface quality: inspect and classify the product surface.
  6. According to the surface treatment: In order to ensure that the surface of the galvanized product will not be oxidized before the user uses it, it needs to be treated, such as passivation, oiling, phosphating, paint sealing and no treatment.
    HUNGTHAI METAL can provide customers with all kinds of steel coils and has a strict quality control system. Customers in need are welcome to cooperate.
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Steel Coil The Secret Of High Quality

Hungthai Metal Color Coated Steel Coil The Secret Of High Quality

Hungthai Metal is a steel manufacturing in china. In order to obtain prepainted galvanized steel coil and prepainted galvalume steel coil with good color coating performance, we will pre-process the substrate.

Hungthai Metal adopts unique substrate pretreatment technology to make the surface of galvanized steel coil and galvalume steel coil adhere to a layer of phosphate conversion coating, which greatly improves the life and weather resistance of color coated steel coil.

The phosphate conversion coating technology of Hungthai Metal is to put galvanized steel coil and galvalume steel coil into a solution containing phosphophyllite for chemical treatment. Phosphate treatment, referred to as phosphating.

The phosphating of Hungthai Metal adopts the unique mixed solution technology of hopeite and phosphophyllite, which greatly improves the life of galvanized material and galvalume steel coil. To ensure that the color coating of color coated steel coil is not easy to peel off, so that customers can obtain high quality PPGI and PPGL.

The reason why the phosphating film can improve the color coated steel coil is that the phosphating film is a porous structure, so it has a good absorption of oil, grease, soap and other properties, and improves the protection of galvanized material and galvalume steel coil. Phosphate film greatly improves the adsorption of various organic films, so it also greatly improves the corrosion resistance of paints and other organic films.

When the metal is phosphated, the corrosion of the damaged area is only local. This is because the metal surface is firmly adsorbed on the metal surface, the non-conductor — the phosphating film insulation. The phosphating film also prevents the electrolyte from being in the horizontal direction. Diffusion, therefore metal corrosion under the organic film is suppressed, greatly improving the lifetime of galvanized steel coil and galvalume steel coil exposed to air.

After phosphating, three steps of water washing, passivation and drying are also required. These processes also affect the quality of the phosphating film.

The most important thing here is the passivation treatment of the galvanized material and galvalume steel coil, because the phosphating film is microscopically porous and uneven, and passivation has the effect of further dissolving and sealing the phosphating film, reducing its porosity and corrosion resistance. Enhanced, the effect is remarkable. Especially when the phosphating film is thin, its porosity is large, the corrosion resistance of the phosphating film itself is limited, and some are even rapidly oxidized and rusted during the drying process. A passivation treatment is performed after phosphating, so that the metal in the pores of the phosphating film can form a passivation layer, so that the pores of the phosphating film can be closed and filled.

After passivation treatment, the phosphating film can also dissolve the loose layer on the phosphating surface and various water-soluble residues contained in it, so that the phosphating film will not be rapidly corroded and rusted in the air, thus improving the phosphating The rust resistance and corrosion resistance of the film itself.

As a responsible ppgi coil exporter China and PPGI manufacturer China, Hungthai Metal keeps innovating to ensure the quality of prepainted galvanized steel coil and PPGL, giving customers good prices and good quality, and looking forward to cooperating with you.

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Salt spray test for detection of Hungthai Metal

Salt spray test is one of the important experiments for Hungthai Metal to test the corrosion resistance of galvanized steel coil, galvalume steel coil and color coated steel coil.

Corrosion is the destruction or deterioration of a material or its properties under the action of the environment. Most corrosion occurs in the atmospheric environment, which contains corrosive components and factors such as oxygen, humidity, temperature changes and pollutants.

Salt spray corrosion is a common and most destructive atmospheric corrosion. The corrosion of salt spray on the surface of metal materials is caused by the electrochemical reaction of the chloride ions contained in the metal surface through the oxide layer and protective layer of the metal surface and the internal metal. At the same time, chloride ions contain a certain amount of hydration energy, and are easily absorbed by pores and cracks on the metal surface to displace and replace oxygen in the oxide layer, turning insoluble oxides into soluble chlorides, and making the passive surface an active surface. .

Salt spray test is an environmental test that mainly uses artificial simulated salt spray environmental conditions created by salt spray test equipment to evaluate the corrosion resistance of products or metal materials. It is divided into two categories, one is natural environmental exposure test, and the other is artificial accelerated simulated salt spray environmental test.

The artificial simulated salt spray environment test is to use a kind of test equipment with a certain volume space – the salt spray test box, in its volume space, artificial methods are used to create a salt spray environment to assess the product’s salt spray corrosion resistance performance and quality .

Compared with the natural environment, the salt concentration of chloride in the salt spray environment can be several times or dozens of times that of the general natural environment, which greatly increases the corrosion rate. The salt spray test is carried out on the product to obtain the result. time is also greatly shortened. For example, if a product sample is tested in a natural exposure environment, it may take 1 year to wait for it to corrode, but in the artificial simulated salt spray environment, it only takes 24 hours to obtain similar results.

In order to better test the performance of galvanized steel coil, galvalume steel coil and color coated steel coil, Hungthai Metal’s salt spray test time is far more than 24 hours, reaching more than 96 hours to ensure the corrosion resistance and life of your products.

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