subject: The Basic Concepts Of Precision Casting [print this page] It includes: investment casting, ceramic molding, metal precision casting, pressure casting, lost foam casting.
The more common is the melting touch casting: choose the appropriate investment casting investment casting materials; to repeat the dip coating molten mold and sanding process, hardened shell and dry; then melt within the melting mode, access to the cavity; baking shell to get sufficient strength, burn residual pattern materials,; cast metal material required; shelling after the sand to get high precision product. According to product needs or heat treatment and cold.
Casting Development
Also known as lost wax casting precision casting, precision of its products, complex, close to the final shape of parts, from time to process or very little processing on the direct use, so casting is a near net shape forming of advanced technology.
Ancient China: Prince afternoon tripod, copper cut-off, bronze lion, are a masterpiece of casting. 40 years since the 20th century, investment casting for industrial production, the half-century has been developing a faster pace. In particular, the rapid development of European and American countries. Now Casting for the aerospace, weapons departments, almost used in all industrial sectors, especially electronics, petroleum, chemical, energy, transportation, light industry, textiles, pharmaceuticals, medical equipment, pumps and valves and other departments. China's rapid development in recent years. Investment casting investment casting technology to not only produce small castings, and can produce large castings, the largest size profile Castings nearly 2m, while the minimum wall thickness less than 2mm. While castings have become more sophisticated, in addition to alignment tolerances, the parts can achieve high geometric tolerances. Investment Castings casting surface angle value is also getting smaller and smaller.
Ceramic Mold Casting
Made with a ceramic slurry casting mold casting method of production. Ceramic slurry the TEOS hydrolysis and texture than pure, high thermal stability of fine sand, such as fire-resistant fused quartz, zircon, corundum and so mixed. In order to glue ceramic slurry knot in a short time, often by adding calcium hydroxide or magnesium oxide as a catalyst. As used in refractory and ceramic components and appearance are similar, so called ceramic. Ceramic Mold Casting in sand casting developed on the basis of a new process. There are two types of ceramic: 1. Ceramic made entirely of ceramic slurry water. The production process is the first look fixed on the type plate, coat sand box, and then tuned ceramic slurry into the sand box, unfinished plastic hardening modulus newcomer, is a mold at high temperature calcination. 2. By bush, bush and look at the gap between the ceramic slurry casting mold manufacturing. Bush sand available, can also be used metal type. Ceramic shell with a bush watering can save a lot of ceramic slurry, the production used more often. Ceramic casting surface roughness Ra10 ~ 1.25 micron dimensional accuracy of up to 3 ~ 5, to achieve little without cutting purposes. Ceramic Mold Casting short production cycle, high metal utilization. Maximum up to ten tonnes of castings, mainly for casting of large thick-walled precision casting and casting a single piece of small quantities of dies, forging dies, plastic mold, metal mold, die casting mold, glass mold and other molds. The life of ceramic casting molds by mechanical processing methods can be made with molds comparable, while manufacturing costs are higher than mechanical mold made of low processing methods.
Sand Casting brief
Casting production in all, 60 ~ 70% of sand casting is produced, and about 70% is clay sand production. Mainly due to sand casting and low cost than other casting methods, production process is simple, short production cycle. So as the car engine block, cylinder head, crankshaft, etc. are used for green sand casting process produced. When the wet type can not meet the requirements and then consider the use of clay, sand is dry sand, dry sand or other sand. Green sand mold castings from a few kilograms of weight can be up to tens of kilograms, while the production of dry clay can weigh hundreds of tons of castings.
In general, for medium and large castings, cast iron pieces can be hard resin from the sand, water glass sand cast steel can be to produce, obtain accurate dimensions, smooth surface of the casting, but the high cost.
Of course, the production of casting sand casting precision, surface finish, material density and microstructure, mechanical performance, it is often poor, so when casting more of these performance requirements, they should use other casting methods, such as investment casting (lost wax) casting, die casting, low pressure die casting and so on.
Casting and production volume should be adapted
Such as sand casting, mass production factories should use advanced technology to create conditions for styling and core methods. Shock-style or old-fashioned shock compression molding machine production line productivity is not high enough, workers labor-intensive, noisy and does not meet the requirements of mass production, should be gradually modified. For small castings, can be used horizontal or vertical type of non-box type high-pressure molding machine production line, real-based modeling and high production efficiency, the area is also less; for the optional items have boxes of various high-pressure molding machine production line, gas impact molding line to accommodate the rapid, high-precision molding production line requirements, building core method can be used: cold box, hot box, the shell core making method such as efficiency. Medium-volume applications can be considered large cast resin sand molding and made from hard-core.
Single small-batch production of heavy castings, hand-shape is still an important way to adapt to a variety of complex shapes by hand are more flexible and does not require a lot of technology and equipment. Can be applied to water glass sand, VRH law water glass sand, organic ester water glass from the hard sand, dry clay, resin, sand and cement from the hard sand, etc.; for the production of heavy-duty one-piece casting, molding methods used to pit low-cost production fast. Mass production of styling products or long multi-box model, splitting flask molding method is more appropriate, although the mold, sand boxes and other starting high investment, but can save hours of work style, improve product quality compensation.
Low pressure casting, die casting, centrifugal casting and other casting methods, equipment and tooling for the price of expensive, so only suitable for mass production.
Modeling method should be suitable for the condition of plant
Such as the production of such large-scale machine tool bed casting, modeling method commonly used group-core, non-production pattern and sand box, to pit groups in the core; and other factory sand box modeling method is adopted, making appearance. Different production conditions (including equipment, facilities, staff quality, etc.), production practices, the experience varies, should be considered under these conditions for doing products and is not suitable (or not) do products.
To take into account the accuracy requirements and the cost of casting
Obtained by various casting precision casting different initial investment and productivity are also inconsistent, the ultimate economic benefits are different. Therefore, to achieve more, faster, better and cheaper, they should take account of aspects. Response to the chosen method of casting a preliminary cost estimate to determine the economic benefits but also guarantee the high demands of casting casting.
Economic crisis affecting the domestic foundry industry
1. The economic crisis has once again casting business to "reshuffle"
As the global recession, casting products in exports, weak domestic demand. Now casting a very limited market resources, the competition for the market resources of Guo Cheng Zhong, some products Zhiliang good, low-cost Qi Ye will win; Bufenguimo Xiao shortage of funds, as well as product quality and cost competitiveness of enterprises are only Ting production or semi-cut-off, if the economic crisis, a long time to some, these enterprises can only be closed down. The first half of 2007 and 2008, casting materials, high prices have made a number of poorly managed foundry business failures, the current economic crisis, the casting of Chinese enterprises will once again shuffle. Survival of the fittest, and thus conducive to China's foundry industry perspective, it may be a good thing.
2. Castings price reduction is the trend
Casting material is subject to the impact of falling prices, overall price reduction casting products is inevitable. The highest prices of raw materials in 2008 calculated on the basis of months, not including tax average market price of pig iron casting has dropped to 2,800 yuan / t or so, a decrease of about 40%; scrap down to 2,000 yuan / t or so, a decrease of about 53 %; foundry coke dropped to 2,400 yuan / t or so, a decrease of about 38%. Calculated on this basis, the major material cost per ton of castings lower than 2000 yuan price reduction if another factor to consider iron alloy, casting down the cost of more; the same time, Coke's price cuts also caused melting costs. This account is not only a clear casting manufacturer, casting the user will be counted, so the inevitable wave of casting products, price reductions, the key is how we cast business intelligence game with the user in the new round of price negotiations to achieve a win-win.
3. Foundry production and management factors that increase the difficulty
Economic crisis casting material prices fell, seemed to cast industry opportunities, but also caused unprecedented problems, the whole, the more challenges than opportunities.
