The basic requirements for foundry sand should meet the following requirements: ① high purity and cleanliness, silica sand, for example, iron sand requires SiO2 content of more than 90% larger castings requires SiO2 content of more than 97%; ② high refractoriness and thermal stability; ③ suitable particle shape and particle composition; ④ not easily wetted by liquid metal; ⑤ cheap and easy to get.
Particle shape and particle shape composed of foundry sand and particles of sand flow, compactness, permeability, strength and permeability properties of liquid metal influence, is an important indicator of the quality of foundry sand.
Foundry sand particle shape shape generally three kinds. ① round sand: particles are circular or nearly circular, smooth surface, no protruding edges. ② polygonal sand: particles into polygonal, and more obtuse. ③ cusp-shaped sand: particles into a cusp-shaped, and mostly acute angle. Particle shape foundry sand generally angular coefficient (ratio of actual surface area of the sand / sand theoretical specific surface area) to represent.
Particles of sand particles is represented by mesh, the method of measurement is to go through the mud washed minutes after drying dry sand into the standard sieve, sieve and then placed on the sand sieving, the sieves after each stay on sand were weighed, after the usual standard sieve sand highest concentration of three adjacent sieve mesh representation of the head and tail particles.
Types and uses different mineral composition according to the foundry sand into sand and non-siliceous sand two categories.
Silica sand main mineral composition of SiO2. ① natural silica sand: sand and core sand for non-ferrous alloy castings, iron castings and small and medium castings. ② selection of natural silica sand: organic matter used as a binder in a variety of sand and core sand. ③ artificial sand: for castings and sand core sand.
Non-non-siliceous sand siliceous sand more types of different purposes. ① limestone sand: crushed limestone from the main mineral composition is CaCO3, steel castings for sand and core sand. ② zircon sand: The main mineral composition is ZrO2 · SiO2, and alloy steel castings for large pieces of sand or sand core surface is composed of sand corundum α-Al2O3, for investment casting, ceramic casting system shell material. ⑥ olivine sand: The main minerals olivine (MgFe) 2SiO4, for cast iron, non-ferrous alloy castings and high manganese steel castings and sand core sand. 不銹鋼精鑄件
Silica sand resources adequate resources in nature, but is suitable for casting high SiO2 content of natural silica sand is not too much. China in 1951, the territory of the casting sand resources have carried out the census, but mainly confined to the vicinity of the main traffic arteries and the industrial city. Census results show that China's natural resources are available for silica sand casting is very rich, the distribution of a wide range. Jirem League of Inner Mongolia, natural silica sand reserves amounted to several million tons, particle shape close to a circle, SiO2 content of about 90%. Jinjiang, Fujian Dongshan sea sand, SiO2 content of 94 to 98%, with low clay content, are good natural silica sand. Jiangxi Duchang, stars, Yongxiu County has a large number of Quaternary lacustrine deposition and silica sand, SiO2 content of about 90% iron content is low, less alkaline oxides, uniform size, the lake is a good sand. Guangzhou, Hunan and other places has a wealth of easily broken weathered sandstone, sand adult workers to be processed, its SiO2 content of more than 96%, can be used for production of steel castings. |
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