What is meant by investment casting?
Investment casting, also known as lost wax casting, includes the processes of pressing wax, repairing wax, forming trees, dipping slurry, melting wax, casting metal liquid and post-treatment. Lost wax casting is to use wax to make the wax mold of the part to be cast, and then the wax mold is coated with mud, which is the mud mold. After the clay mold is dried, the internal wax mold is melted in hot water. After melting the wax mold, the clay mold is taken out and baked into a ceramic mold. Once it is fired. When the clay mold is generally made, the pouring mouth is left, and then the molten metal is poured through the pouring mouth, and after cooling, the required parts are made.
What are the different types of materials that can be used to make a sand mold for casting?
Casting sand is used in sand casting production, according to relevant statistics, every production of 1 ton of qualified castings, about 1 ton of new sand needs to be replenished, and with the increasing demand for high-performance castings in the automotive, railroad transportation, aerospace and other industries, so the scale of market demand for casting products continues to grow, at present, the sand used for casting is silica sand and non-silica sand two categories.
1. Silica sand: the main mineral composition is SiO2
Natural silica sand: used for non-ferrous alloy castings, cast iron parts and core sand for small and medium-sized cast steel parts.
Selected natural silica sand: used for various kinds of shaped sand and core sand with organic matter as binder.
Artificial silica sand: used for mould and core sand of cast steel parts.
2. Non-silica sand.
Sands for casting are limestone sand, quartz sand, corundum sand, clay sand, zirconium sand, etc. There are more types and different uses.
Casting sand raw materials are
Limestone sand
It is made from crushed limestone, and the main mineral composition is CaCO3, which is used for the mould sand and core sand of cast steel parts.
Quartz sand
It is a granular material made of quartzite, which is crushed and processed. It is milky white or translucent in color and is commonly used in the fields of casting, fireproof material, gold treatment and chemical industry.
Corundum sand
The main mineral composition is α-Al2O3, which is used as shell material for fusion mold and ceramic type casting.
Clay sand
It is mainly classified according to the clay content of the original sand, there is no specific requirement for quartz content, but the clay content needs to be less than 50%, commonly used in non-ferrous metal castings.
The pros of zircon sand investment casting
Zirconia sand is not only an important mineral for refining zirconium and hafnium metals, but also used in large quantities directly in ceramics and foundry industries. Zirconium is a silver-white, hard metal with a melting point of 1852°C and a boiling point of 4370°C. It has a series of excellent properties such as low toxicity, corrosion resistance, good mechanical properties and plasticity at high temperatures, corrosion resistance and special nuclear properties, so zirconium hafnium metal and its alloys are widely used in aerospace, aviation, atomic energy, electronics, metallurgy, chemical, energy, light industry, machinery and medical industries. In addition, zirconia sand and zirconium dioxide compounds also have excellent physicochemical properties, high melting point, high temperature intolerability, difficult decomposition, low bulk expansion, high thermal conductivity, not easily infiltrated by molten metal, high refractive index, and high corrosion resistance, so they are used in large quantities in the foundry industry, ceramic industry and refractory industry.
Zircon sand (zirconia) is used in refractory materials (zirconia corundum bricks, zirconia refractory fibers), foundry sand for casting (precision casting sand), precision enamelware, and also in the production of glass, metal (zirconium sponge), and zirconium compounds (zirconium dioxide, zirconium chloride, sodium zirconate, potassium fluorozirconate, zirconium sulfate, etc.). It can be used to make zircon bricks for glass kilns, zircon bricks for steel barrels, tamping materials and pouring materials; it can be added to other materials to improve their properties, such as synthetic cordierite with zircon sand to broaden the sintering range of cordierite without affecting its thermal shock stability; zircon sand is added to high alumina bricks to make spalling resistant high alumina bricks with much higher thermal shock stability; it can also be used to extract ZrO2. zircon sand can be used for casting High quality raw sand, zircon sand powder is the main component of foundry coatings.
The cons of zircon sand investment casting
1、The accuracy of the casting is restricted. Due to the investment casting process, the surface roughness of the casting is affected, so that the accuracy of the casting is limited.
2、Higher cost. The cost of zircon sand investment casting is higher than other processes, which is due to the fact that zircon sand investment casting requires higher precision, and the process with higher precision requires more input.
3、the material is limited. Zircon sand investment casting can only be used for casting non-metallic materials, can not be used for casting metal materials.
The definition of zircon sand investment casting
With low acidity, high melting point, and the ability to bond with all mailing and inorganic sand binders, zircon sand can be used as a molding substrate for sand casting and investment casting. With the development of domestic precision casting industry, the demand for zirconia sand in the casting field is also expected to continue to grow, further driving the zirconia sand market demand.
In terms of refractory materials, zircon sand can be used to produce zircon bricks, zircon corundum bricks, zirconium mullite bricks, etc. With the economic recovery and the development of urbanization in emerging economies as well as industrial and commercial construction markets, the demand for refractory materials is also expected to continue to grow. The demand for zirconia sand products in the refractories sector is also expected to continue to grow.
In addition, zirconia sand can be processed to form many zirconium compounds such as zirconium chloride oxide, zirconium sulfate, basic zirconium carbonate, and ammonium zirconium carbonate, which can be used in the cosmetics industry, printing, paints, and inks, among others. Zirconium can also be used as nuclear polar zirconium, as nuclear fuel casing material, pressure tubes, active zone support components, and nuclear fuel cores.
Zircon sand investment casting process
The investment casting process has a variety of advantages: good surface quality, high dimensional accuracy, suitable for complex shapes, can be used for a variety of alloys, production batch flexibility, so the investment casting process is increasingly widely used. Investment casting old shells contain a large number of wrong British sand “powder”, is a potential resource. Therefore, separating the pinning sand (powder) from the old shells of investment casting to be utilized can not only relieve the domestic demand, but also reduce the waste of land resources and protect the environment, which is a meaningful treatment.
The results show that a better process to separate the knotted sand from the old shells of fusion casting is: old shells by manual sorting, magnetic washing to remove debris, crushing, sieving, where the coarser part of the rod mill, so that the wrong British sand alone, and then sieved again, sieved sand material first magnetic separation to remove part of the iron, and then re-election, flotation, if the flotation of the wrong British sand iron content is too high, can be made by acid leaching to drop, and then the wrong British sand will be separated by the process route. Then the wrong British sand for rinsing, drying, that is to get wrong British sand. The separated knotted British sand can reach the secondary standard. Due to the small size of the wrong Ying powder, the re-election and flotation can not be separated out. Grinding method to rod mill is good, grinding time 10min, grinding concentration 60%. The experimental conditions of re-election are 11L/min of feed water flow, 15.5L/min of flushing water flow, and 3″ of lateral inclination of the bed. Flotation with sodium dodecyl benzoate as a trapping agent, with secoctanol as a regulator, no inhibitor, the required pH is 5.5, stirring time is 4min, can be used for flotation of sand material should be between 80 ~ 325 mesh.
Usage of zircon sand
Zirconia sand zirconia powder uses
1、Foundry industry
Zirconia sand (powder) is used in the thick wall of large cast steel parts and the veil of various alloy steel castings, as the surface layer material has the effect of refining the grain, so zirconia sand (powder) is a good shell-making refractory material, often used as the preparation of the surface layer and sand spreading material.
2. Refractory industry
Zircon sand can be used to produce zircon bricks, zirconia corundum electrofused bricks, sintered bricks, sinkhole bricks, zirconium pounding materials for glass kilns and pouring materials.
3. Ceramic industry
With a high refractive index of 1.93-2.01 and chemical stability, zirconium quartz powder is an excellent and inexpensive emulsion, which is widely used in the production of various architectural ceramics, sanitary ceramics, daily-use ceramics and handicraft ceramics, etc. It is widely used in the processing and production of ceramic glaze, and has a large application. Zirconium quartz powder is widely used in the production of ceramics, but also because of its good chemical stability, and therefore not affected by the firing atmosphere of ceramics, and can significantly improve the ceramic billet glaze bonding properties, improve the hardness of ceramic glaze.
4、Coating industry
Zirconium quartz powder has strong cooling ability for castings, good anti-adhesive sand, can effectively prevent surface defects of castings, the surface of castings is bright and clean, easy to clean. It is suitable for large and medium-sized cast steel parts and cast iron parts and non-ferrous alloy castings.
5、Glass industry
Can be used in the manufacture of color picture tubes in the television industry and emulsified glass in the glass industry.
6、Chemical industry
Zirconium quartz powder can be used as raw materials for cosmetics, cement, food preservation, tanning, and fiber (for making flame retardant fiber).
Types of zircon sand
Zircon sand (zircon) is produced as a parameral in various igneous rocks. It can be enriched in alkaline rocks and alkaline pegmatites, with well-known sources in southern Norway and the Russian Urals. Zircon is also often enriched in alluvial ores. The world’s important gem-quality zircon is produced in Laos, Cambodia, Myanmar, and Thailand. Zircon is the most important mineral raw material for the extraction of zirconium and hafnium, and is also used in the defense and aerospace industries. Zircon sand (zircon) is a silicate mineral, which can be divided into two variants, high and low type, according to its physical properties and chemical composition. Most of the crystals with complete crystallization are “high type”; those with very poor or no crystals are “low type”. There are also three types: high, medium and low. However, in terms of gemstone value, the high type is more valuable.
Zircon sand (zircon) is the second most refractive stone after diamond in terms of refractive index and has a high dispersion value. Zircon is commonly used in colorless, reddish-brown, maroon and green colors. However, the most popular colors are blue and colorless, with blue being the more valuable and usually artificially heat-treated. Many zircon stones on the market are heat-treated and then brought out for sale. This is because the treated stones are more beautiful and better marketed than the original stones. Zircon sand (zircon) has a tetragonal crystal system with a0=0.662nm and c0=0.602nm; Z=4. The structure has Zr and Si arranged interphase along the c-axis into tetragonal body-centered cells. The crystal structure can be considered to be formed by the association of [SiO4] tetrahedra and [ZrO8] triangular dodecahedra. The [ZrO8] triangular dodecahedra are tightly connected in the b-axis direction in a co-prismatic manner. Complex tetragonal bipyramidal crystal type, D4h-4/mmm (L44L25PC). The crystals are tetragonal bipyramidal, columnar and plate-like, and the morphology is closely related to the composition. The main monomorphs: tetragonal column m, a, tetragonal bipyramidal p, u, compound tetragonal bipyramidal x. It can be formed into knee-like bicrystals. It can be connected with yttrium phosphate in a regular way.
Zircon sand specification
The specifications of zircon sand are mainly as follows: 10/20#, 30/60#, 60/120#, 120/240#, 240/500#, 500/850#, 850/1200#, 1200/2000#, 2000/3000#, etc.
Where to buy zircon sand?
Zircon sand can be purchased at auto supply stores, machinery and equipment stores, hardware stores, etc.
Is zircon sand hazardous?
Zircon sand, like many other rocks and ores, is naturally occurring radioactive material (NORM) and is used in many applications such as tile, bathroom, casting and refractory materials, medical implants, consumer electronics, and jet engine parts manufacturing.
Zircon sand has a low level of radioactivity, comparable to other naturally occurring radioactive materials such as granite. Radiation can originate both internally and externally and can be protected by taking appropriate simple measures to protect personnel.
Possible sources of external radiationGamma radiation dose rates around bulk zircon sand are relatively low, typically in the range of 1-2 mSv per hour. A mSv is a unit of measurement of radiation dose equal to one millionth of a sievert. The radiation dose a person receives depends on the intensity of the source, the distance from the source, and the time of exposure to the radiation. Dosimeters are generally used to measure radiation dose.
Possible sources of external radiation
Gamma radiation dose rates around bulk zircon sand are relatively low, typically in the range of 1-2 mSv per hour. A mSv is a unit of measurement of radiation dose equal to one millionth of a sievert. The radiation dose a person receives depends on the intensity of the source, the distance from the source, and the time of exposure to the radiation. Dosimeters are generally used to measure radiation dose.
Possible sources of internal radiation
Zircon sand particles are too large to be inhaled directly by humans, but dust created during the dry grinding process of zircon sand may be inhaled directly. Fine dust particles may be generated when separating zircon sand from mineral sand or during bulk handling.Internal radiation may also be induced by oral ingestion, but a very large intake is required to achieve a measurable radiation dose.
How to control the quality of investment castings?
1、the correct choice of casting materials. Casting materials with good mechanical properties and corrosion resistance should be selected to ensure the quality of molten die castings.
2、Adopt reasonable moldmaking technology and process. According to the shape, size and structure of different castings, molten die technology and process should be used to ensure the quality of the casting.
3、Adopt effective quality control technology. Laboratory testing of the mechanical properties of the castings and inspection of the surface quality and structural quality of the molten die castings should be used to ensure the quality of the castings meet the requirements.
4、the use of appropriate heat treatment process. After the molten die castings are out of the cast, appropriate heat treatment process should be used to improve the performance and quality of the castings according to the performance of the casting material and the structure and performance requirements of the castings.
