Applications foundry sands

Iron oxide is also used for nonpigmentary applications, eg, ferrites (qv) and foundry sands making total world demand for iron oxide close to 1 X 10 t. The principal worldwide producers of iron oxide pigments are Bayer AG (ca 300,000 t/yr worldwide), and Harcros Pigments Inc., a subsidiary of Harrisons Crosfield PLC. In the United States, Bayer produces the Bayferrox line of iron oxide pigments in New Martinsville (see Iron compounds). 

Physical properties involve tests of the physical index parameters of the materials. For spent foundry sand, these parameters include particle gradation, unit weight, specific density, moisture content, adsorption, hydraulic conductivity, clay content, plastic limit, and plastic index. These parameters determine the suitability of spent foundry sand for uses in potential applications. Typical physical properties of spent green foundry sand are listed in Table 4.5. 

Embankment and fill applications are the biggest end-user of spent foundry sand. Natural soils are often composed primarily of sand, clay, and water. Most spent foundry sands have these same constituents, which suggests spent foundry sand as a good fill material. The immediate benefits include saving virgin soil materials and reduce the bottom line of the foundry industry. It is also reported that foundry sand as a fill material may present better performance then conventional materials, including better resistance to freeze-thaw distress. 

The physical properties of concern for construction fill applications are the relationship between moisture and density, plasticity, the liquid limit, and particle size distribution. The same set of construction machinery for conventional fills, such as bulldozers, compactors, and grabbers, is suitable for fill earth works containing spent foundry sand. 

Natural sand is a major component of most flowable fill mixes. Ferrous spent foundry sand can be used as substitute for natural sand (fine aggregate) in flowable fill.48 49 Spent sands from nonferrous foundries and foundry baghouse dust can contain high concentrations of heavy metals that may preclude their use in flowable fill applications. Some of the engineering properties of spent foundry sand that are of particular interest when foundry sand is used in flowable fill applications include particle shape, gradation, strength characteristics, soundness, deleterious substances, and corrosivity. 

Some end-use applications may prefer the characteristics of foundry solid waste. For instance, spent foundry sand is a uniformly graded fine aggregate containing chemically active iron and organics. Spent foundry sand can be superior to other types of granular materials, such as compacted soils or clays, for hydraulic barriers. In this case, spent foundry sand provides better performance at lower cost. 

Foundry resins, phenolic, 18 788—789 Foundry sand, chromite application, 6 493-494, 497 4A zeolite. See Zeolite 4A Four-component color matching system,... 

Resins. As mentioned above, both furfural and furfuryl alcohol are widely used in resin applications. Another resin former, 2,5-furandimethanol [1883-75-6] (BHMF), is prepared from furfuryl alcohol by reaction with formaldehyde. It is usually not isolated because oligomerization occurs simultaneously with formation (competing reaction). Both the monomer and oligomers are very reactive owing to difuntionality, and are used primarily as binders for foundry sand (72) and fiberglass insulation (147,148). 

The cyclic alkylene carbonates have also been applied as the cure-accelerators of phenol-formaldehyde (PF) [262-266] and sodium silicate [267] resin systems, which are widely used in foundry sand and wood binder applications. 

The use of polyurethane as a binder has found two interesting applications foundry cores and woodchip particleboard. The foundry industry has recognized the value of polyurethane adhesive binders to bind sand foundry cores for metal casting. This application is increasing steadily. The use of isocyanate binders for woodchip particleboard is receiving significant attention. The... 

A. Binder for Foundry Sand. The major industrial use o furan resins is as a binder for foundry sand. Low levels of resin binder (0.8 to 27 ) are used to bond the sand as cores and molds for molten metal. By use of continuous mixers and appropriate levels of strong, acidic catalysts, set and strip times as low as 45 seconds at ambient temperature are attainable (see Figures 1 and 2). The furan resins work ideally in this application since they have sufficient thermal stability to retain the shape of the mold until the metal sets, then subsequently carbonize to allow shake-out of the sand after the metal hardens. 

Foundry sand (FS) - In typical foundry processes, sand from collapsed molds or cores can be reclaimed and reused - Little information is available regarding the amount of FS that is used for purposes other than in-plant reclamation, but spent FS has been used as a fine aggregate substitute in construction applications and as kiln feed in the manufacture of Portland cement - Most of the spent FS from green sand operations is land filled, sometimes being used as a supplemental cover material at landfill sites 81-87... 

This is an example of the use of guanidine stabilized sodium polysilicate (Si02/Na20 ratio 5 1) prepared according to Example 1 of patent application Ser. No. 287,037, filed Sept. 7, 1972, as a binder for foundry sand cores. These sand cores were used to make aluminum castings in a nonferrous metal foundry. 

Phenolic resins are also extensively used in the binding of foundry molds. Both resol and novolak resins are used for this application. The sand is coated with the phenolic resin at a rate of 3 to 4%. The PF resin can be used both as an organic solvent solution and in powder form. Coating of the substrate can be done both at ambient or at higher temperature. In higher-temperature coatings novolaks are the preferred resins and in this application, waterborne resins (75% resin) can also be used. Hexamethylenetetramine as well as wax are added. Hexamine is often added separately from the resin to avoid precuring. 

Polymeric aerogels based on RF were developed in the last years for application in foundry practice as a new nanostructured binder for foundry sands. Their properties allow, for instance, to replace conventional polymeric binders, since they solve certain problems of core removal, penetration, surface reactions, blow holes, and other casting defects especially in light metal casting. RF aerogels as polymeric binders are at the verge of being used by industry. 

There are numerous systems in the lumber, furniture, textile, paper, food, tire, and ceramic industries, to name but a few. A brief description of these follows. In only a few cases, such as the postdrying of crackers, cookies, and biscuits or the drying of foundry sand cores are there many systems utilizing the same basic equipment. In most cases, the systems are customized or one of a kind so the number of actual applications is much larger. The same holds true for microwave drying. 

The management range of after foundry sands in production of burned ceramic building materials, depends obviously on economic and logistic conditions. However, it should be emphasized that an important element in taking a decision of the application of these wastes is the warranty of a continuous supply of reclaimed sands and their proper preparation. 

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