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What is casting coating

What is casting coating

Publishdate:2020-03-03 Views:134



Casting coating is a casting auxiliary material which covers the surface of the core to improve its surface fire resistance, chemical stability, resistance to molten metal erosion and sand sticking resistance. The casting coating can be made into slurry, paste or powder, and coated on the core surface by spray, brush, invasion, flow and other methods.


the main raw material is special diatomite. 5-8% bound water, organic matter and impurities in diatomite are removed; Al2O3, SiO2; suspending agent for casting coating (lithium based attapulgite, organic soil, etc.).


bauxite, mainly composed of alumina, is hydrated alumina containing impurities, which is a kind of earth like mineral. White or grayish white, brown yellow or light red due to iron content. 45 g / cm3, hardness 1-3, opaque, brittle. It's extremely difficult to melt. It is insoluble in water, but soluble in sulfuric acid and sodium hydroxide solution. It is mainly used for aluminum smelting.


quartz sand is a kind of hard, wear-resistant and stable silicate mineral with stable chemical properties. Its main mineral composition is SiO2 The color of quartz sand is milky white or colorless translucent, hardness is 7, brittle and cleavage free, shell like fracture, grease luster, density is 2.65, bulk density (1-20 mesh is 1.6 ~ 1.8), 20-200 mesh is 1.5. Its chemical, thermal and mechanical properties have obvious anisotropy, insoluble in acid, slightly soluble in KOH solution, melting point 1750 ℃.


Kyanite [1], also known as anhydrite, is a silicate mineral, which is a natural refractory raw material with high fire resistance and large volume expansion at high temperature. Kyanite is triclinic, usually flat columnar crystal with parallel stripes on the crystal surface. The color is light blue or cyan, bright gray white and so on. The hardness is 5.5-7.0, and the specific gravity is 3.53-3.65. The mullite was gradually transformed into mullite at high temperature above 1100 ℃ and completely transformed into mullite at 1450 ℃. It can be decomposed into corundum and liquid phase at 1810 ℃, which is an ideal mineral to replace corundum refractory.


graphite powder is soft and black gray; it has greasy feeling and can pollute paper. The hardness is 1-2, and the hardness increases to 3-5 along the vertical direction with the increase of impurities. The specific gravity is 1.9-2.3. Under the condition of isolating oxygen, its melting point is above 3000 ℃, and it is one of the most heat resistant minerals. At room temperature, the chemical properties of graphite powder are relatively stable, insoluble in water, dilute acid, dilute alkali and organic solvents.


chromite is a kind of mineral, mainly composed of iron, magnesium and chromium oxides: (Fe, Mg) cr2o4, is a kind of spinel. It is a mineable chromium ore with complex mineral composition, variable magnesium content and sometimes aluminum and iron elements. There are about 30 kinds of chromium minerals in nature, but only chromite is of industrial value. Chromite is refractory and can be used as refractories, as well as chromium compounds such as chromium trioxide, sodium dichromate and potassium dichromate.


Scope of application: metal mold surface, iron mold / aluminum mold / copper mold; function: 1. Heat insulation coating, balanced temperature, avoid the impact and corrosion of liquid metal, so as to protect the mold and prolong the service life of mold for more than 1 / 3; 2. Prevent casting products from cracking and white iron formation caused by local cooling too fast; 3. Adsorption time as long as 7 days, good air permeability Each time, acetylene fumigation can be used to replace the use of mold release agent, and one casting can be smoked once; 1. Compared with phosphate coating, its unique physical properties determine its advantages; 2. Good air permeability; 3. Obvious heat preservation and heat insulation effect, melting point above 1650 ℃; 4. Strong adhesion after spraying and should not peel off, usually need to be repaired after a week Like other coatings, spraying is needed every time you open the mold, which saves the tedious work of assembling and disassembling molds due to gunning and patching every day; 5. The price is relatively cheap, which greatly reduces the expensive production and casting costs caused by the use of alcohol based coatings or imported coatings; 6. Greatly improves the production efficiency.


it is suggested to use the ratio of 100g coating powder + 100g neutral sodium silicate + 300g water, pour it into soybean milk machine and mix it fully, then pour it into the spray gun and spray it on the hot (200-300 ℃) metal mold surface, the thickness is 0.2mm, and the thickness of local thin part can be sprayed 0.3-0.4mm according to the product requirements, and it can be dried. About 20-30 molds can be sprayed. In case of any discrepancy, the manufacturer's demand shall prevail!