The best refractory fillers in foundry coatings are fused mullite powder and chemically purified zirconium dioxide powder, corundum powder and zirconium powder. However, fused mullite powder and pure zirconia powder are expensive, and corundum powder and zirconium powder are also expensive. This article describes the high-** paint, its high-grade fire-resistant filler ** source rich, cheap, paint performance and use of the effect of zirconium powder paint, corundum powder paint comparable, is worth promoting a cast steel, cast iron with shallow Color paint.
Coatings Coatings consists of 5 parts: refractory fillers, liquid carriers, suspending agents, binders and various additives.
Fire-resistant filler Fire-resistant filler is the main part of the coating. Its physical and chemical properties have a decisive influence on the coating effect, especially on the refractoriness and thermal chemical stability of the coating.
Corundum powder, zirconium powder, bauxite powder, chromite powder, quartz powder and graphite powder have high refractoriness, but corundum powder is expensive; chromite ore powder and graphite are black, which seriously pollutes the environment. The chromite ore powder is poor in domestic resources and needs to be imported from abroad. Graphite is likely to cause carbon increase in the production of steel castings. Although the quartz powder is white, the quartz dust easily causes the workers to get silicosis in the process of sand cleaning; Powder (rice white) and bauxite powder (light yellow) are both light-colored, have high refractoriness and low sintering point, and are easy to obtain sintering and peeling coatings. Therefore, bauxite powder is selected as the material in this paper. The refractory filler replaces Zircon powder.
Bauxite powder, also known as high **, is a silicon-aluminum refractories. It is made of high-alumina bauxite ore, which has been calcined at a high temperature of 1300 to 1500°C, and is obtained from a corundum bauxite bauxite clinker, which is then ground. The main mineral composition of bauxite is corundum (α-Al2O3) and mullite (3Al2O3·2SiO2). The refractoriness of bauxite clinker increases with the increase of Al2O3 content and the increase of calcination temperature, and its refractoriness ≥ 1770 °C. Bauxite does not generate a low-melting point substance with the metal oxide at the pouring temperature, and at the same time, the wettability of the molten steel and its oxide to the high level is relatively low. Therefore, it can be used as a good anti-adhesion effect for the coating. When high ** is used as refractory filler, it must pay attention to its purity, Al2O3 content should be ≥ 85%, impurity content should be less.
Ethanol is generally used as the liquid carrier. Ethanol is non-toxic, odorless, volatile and combustible. It is the most economical and safe carrier liquid. The purity of industrial ethanol is about 95%. It is difficult to ignite and burn the paint, and it is difficult to fully burn. A certain amount of methanol can be added and used in combination to improve its combustion performance. Methanol is more volatile than ethanol and burns faster, but methanol is more toxic. It is harmful to ocular nerve stimulation and should be used with caution.
The suspending agent bentonite is the most commonly used suspending agent in paints. The bentonite particles are very small (less than 0.1 μm). The carrier is wetted by the carrier and the carrier not only adsorbs on the surface of the particles but also enters into the colloidal layer between its crystal layers to make the carrier fluid into a colloidal solution. The bentonite particles form a spatial network structure in the colloidal solution, so that the bentonite slurry has a yield value, and the particles of the refractory filler particles do not easily sink. This paint uses lithium bentonite as a suspending agent. Lithium bentonite is obtained by ion exchange treatment of natural calcium bentonite. It cannot fully swell in ethanol and can only form colloids. Therefore, water must be added to make it fully swell, and then bentonite slurry is made by diluting with ethanol. Use after ~3 days.
Binder The paint uses a thermoplastic phenolic resin as a binder, it is soluble in alcohol, insoluble in water, the paint can have a higher surface strength, but the amount of gas generated is large, so the amount of addition in the paint should not be too much. The addition of polyvinyl butyral (PVB), as a thickener and binder, not only slows the loss of the carrier into the sand matrix, but also slows the sinking of the refractory filler and improves the suspension of the alcohol-based coating. And make the paint have a high thixotropy. Its combination with phenolic resin can make the coating bond strength higher, and the amount should not be too much to prevent the coating from pitting or bubbles after ignition.
Additives (1) Defoamers Common defoamers are n-butanol, n-pentanol and n-octanol.
(2) Sintering agent In order to enable the high-melting refractory filler to be sintered, a certain amount of sintering agent such as mica powder, feldspar powder, etc. may be added to promote the sintering and crusting of the refractory filler particles.
The production test results were achieved by brushing and spraying high-grade paints on the steel casting support (outside dimensions 320 mm×300 mm×255 mm, weight 68 kg) and cast iron box (overall dimensions 1000 mm×800 mm×500 mm, weight 93 kg). In terms of pouring conditions, the brushing, covering and anti-sanding properties are basically the same as those of the original zirconium powder coating. The surface quality of the casting is not significantly different from that of the original zircon powder coating. Shows that the high ** coating is an inexpensive cast steel, cast iron light-colored paint.
Coatings Coatings consists of 5 parts: refractory fillers, liquid carriers, suspending agents, binders and various additives.
Fire-resistant filler Fire-resistant filler is the main part of the coating. Its physical and chemical properties have a decisive influence on the coating effect, especially on the refractoriness and thermal chemical stability of the coating.
Corundum powder, zirconium powder, bauxite powder, chromite powder, quartz powder and graphite powder have high refractoriness, but corundum powder is expensive; chromite ore powder and graphite are black, which seriously pollutes the environment. The chromite ore powder is poor in domestic resources and needs to be imported from abroad. Graphite is likely to cause carbon increase in the production of steel castings. Although the quartz powder is white, the quartz dust easily causes the workers to get silicosis in the process of sand cleaning; Powder (rice white) and bauxite powder (light yellow) are both light-colored, have high refractoriness and low sintering point, and are easy to obtain sintering and peeling coatings. Therefore, bauxite powder is selected as the material in this paper. The refractory filler replaces Zircon powder.
Bauxite powder, also known as high **, is a silicon-aluminum refractories. It is made of high-alumina bauxite ore, which has been calcined at a high temperature of 1300 to 1500°C, and is obtained from a corundum bauxite bauxite clinker, which is then ground. The main mineral composition of bauxite is corundum (α-Al2O3) and mullite (3Al2O3·2SiO2). The refractoriness of bauxite clinker increases with the increase of Al2O3 content and the increase of calcination temperature, and its refractoriness ≥ 1770 °C. Bauxite does not generate a low-melting point substance with the metal oxide at the pouring temperature, and at the same time, the wettability of the molten steel and its oxide to the high level is relatively low. Therefore, it can be used as a good anti-adhesion effect for the coating. When high ** is used as refractory filler, it must pay attention to its purity, Al2O3 content should be ≥ 85%, impurity content should be less.
Ethanol is generally used as the liquid carrier. Ethanol is non-toxic, odorless, volatile and combustible. It is the most economical and safe carrier liquid. The purity of industrial ethanol is about 95%. It is difficult to ignite and burn the paint, and it is difficult to fully burn. A certain amount of methanol can be added and used in combination to improve its combustion performance. Methanol is more volatile than ethanol and burns faster, but methanol is more toxic. It is harmful to ocular nerve stimulation and should be used with caution.
The suspending agent bentonite is the most commonly used suspending agent in paints. The bentonite particles are very small (less than 0.1 μm). The carrier is wetted by the carrier and the carrier not only adsorbs on the surface of the particles but also enters into the colloidal layer between its crystal layers to make the carrier fluid into a colloidal solution. The bentonite particles form a spatial network structure in the colloidal solution, so that the bentonite slurry has a yield value, and the particles of the refractory filler particles do not easily sink. This paint uses lithium bentonite as a suspending agent. Lithium bentonite is obtained by ion exchange treatment of natural calcium bentonite. It cannot fully swell in ethanol and can only form colloids. Therefore, water must be added to make it fully swell, and then bentonite slurry is made by diluting with ethanol. Use after ~3 days.
Binder The paint uses a thermoplastic phenolic resin as a binder, it is soluble in alcohol, insoluble in water, the paint can have a higher surface strength, but the amount of gas generated is large, so the amount of addition in the paint should not be too much. The addition of polyvinyl butyral (PVB), as a thickener and binder, not only slows the loss of the carrier into the sand matrix, but also slows the sinking of the refractory filler and improves the suspension of the alcohol-based coating. And make the paint have a high thixotropy. Its combination with phenolic resin can make the coating bond strength higher, and the amount should not be too much to prevent the coating from pitting or bubbles after ignition.
Additives (1) Defoamers Common defoamers are n-butanol, n-pentanol and n-octanol.
(2) Sintering agent In order to enable the high-melting refractory filler to be sintered, a certain amount of sintering agent such as mica powder, feldspar powder, etc. may be added to promote the sintering and crusting of the refractory filler particles.
The production test results were achieved by brushing and spraying high-grade paints on the steel casting support (outside dimensions 320 mm×300 mm×255 mm, weight 68 kg) and cast iron box (overall dimensions 1000 mm×800 mm×500 mm, weight 93 kg). In terms of pouring conditions, the brushing, covering and anti-sanding properties are basically the same as those of the original zirconium powder coating. The surface quality of the casting is not significantly different from that of the original zircon powder coating. Shows that the high ** coating is an inexpensive cast steel, cast iron light-colored paint.
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