One of the simplest technologies for making castings from any type of metal is casting into the ground. Of course, we are not talking about ordinary black soil. For this purpose, molding mixtures based on sand are used. In most cases, its quartz variety is used, which has a high melting point and the necessary physicochemical properties. However, other types of bases are also used in metallurgy, which will be discussed in more detail below.
Classification of molding sands
The classification of fillers for foundry production is carried out in accordance with the state standard. Sands are divided into classes depending on the content of silica, as well as clay inclusions and other impurities. Fillers are divided into groups depending on the fraction.
To create molds and rods, sands of a certain size are selected. The separation of particles of a given size occurs on a special installation with several calibration sieves. The largest number of grains remaining on three adjacent sieves is called the main fraction, the middle sieve determines the group.
In addition, molding sand is classified into categories A and B. If after sieving most of the grains remain in the upper sieve, then such a filler belongs to A, if vice versa, then to B. When marking, the first digit is the class, then the group and category. For example, molding sand 1K02A is quartz, of the first grain size class, the second group and category A.
For the production of castings from non-ferrous metals and alloys, as well as small cast iron castings, weak and semi-bold bases are used. And in the manufacture of cast iron and steel castings, quartz sands of grades 1-4 are used for pouring cores and molds.
To reduce the likelihood of burning in the production of large-sized steel parts, the quartz base is replaced by refractory materials that do not react with the melt. In addition, the absence of changes in the structure of the filler under the influence of high temperature is of great importance. Such substances include chromium iron ore, zircon mixtures, magnesite and their compounds with chromium.
Recently, the technology of cold-hardening mixtures has become widespread in foundry production. In this case, when creating molds and cores, a sand base is used with the addition of chemical catalysts, thanks to which it quickly hardens. Such CTC technology allows you to abandon the heat treatment of half-molds, which significantly reduces energy costs for drying molds, and also speeds up the technological process of production.
Regenerate is also used as a base – a filler obtained after processing destroyed molds. Its use allows to significantly reduce the consumption of “pure” filler, which reduces the cost of production.
However, even the reuse of mixtures does not provide for waste-free production. When manufacturing parts, burnt spent molding sand invariably remains, which is classified as low-hazard waste. Therefore, such mixtures are used in road construction, soil reinforcement and other construction works.
Pros and cons of using molding sands for foundry production
The use of inexpensive materials for casting into the ground allows you to save money significantly. At the same time, there is no need to purchase expensive equipment. When using HTS production, it is possible to produce parts with high surface quality. However, even when using regenerated mixtures, it is not possible to completely eliminate the occurrence of waste, which must subsequently be disposed of.
E-mail: info@ukrfavorit.com.ua
Call: 0800 33 92 85 (free of charge)
Ukrfavorit Press Service
