Tag Archives: sand casting

castings/">investment casting, also known as \"lost wax casting\" lost wax method to our origins in the late Spring and Autumn Period. Warring States, Qin and Han dynasties, the lost wax method is more popular, especially Sui Tang Zhiming, the Qing period, mostly cast bronze using the lost wax method.
Lost wax casting method is generally used for the production of small out of the bronze cast of this approach is neither range marks, nor traces of gasket, casting hollow objects with it better.
Casting technique for the development of the world s metallurgical have a great impact. Modern investment casting industry, is from the traditional lost wax method evolved. While much of the wax material, tooling, molding materials, process methods, etc., they are quite different, but their principle is the same process. Mid-1950s, Austin American engineer named after him was founded the modern investment casting technology, has been the traditional lost wax method from the Chinese inspiration.
Casting characteristics
Production of investment casting alloy types are carbon steel, alloy steel, heat-resistant alloys, stainless steel, precision alloys, permanent magnet alloy, bearing alloys, copper alloys, aluminum alloys, titanium and cast iron, etc.
Castings are generally more complex shapes, castings can be cast out of the smallest hole diameter 0.5mm, the minimum casting wall thickness 0.3mm. In production can be some of the original parts from the combination of several components, by changing parts of the structure and design as a whole from the parts and direct investment casting cast out, to save processing time and the consumption of metal, so that part structure more is reasonable.
Casting weight of dozens of cattle, mostly zero (ie, tens of grams to several kilograms), heavy castings with casting the production of more trouble, but the production of large castings of weight reached about 800 cattle.
Casting process is more complex and difficult to control, use and consumption of materials more expensive, so it applies to produce complex shapes, high precision machining or other difficult small parts, such as turbine engine blades.
Casting Process Design
As if casting process design, investment casting process design tasks:
(1) analysis of the structure of the process of casting;
(2) choose the right technology solutions, to determine the casting process parameters, based on the above casting diagram drawing;
(3) design pouring risk system to determine the module structure.
Casting the casting method
Casting casting methods commonly used are:
1) heat and gravity casting methods are the following.
This is the most widely used form of a cast that shell after being removed from the roaster, at high temperatures by the casting. At this point the metal to cool slowly in the shell, in the case of high mobility of filling the mold, so the casting can be a good copy of the shape of the cavity to improve the accuracy of the casting. However, the thermal-type casting in coarse grains will slow cooling, which reduces the mechanical properties of castings. In casting steel castings, castings cooling surface is also easy to slow oxidation and decarbonization, reducing the casting surface hardness, finish and dimensional accuracy.
2) Vacuum casting
Vacuum casting shell on the box, through the tiny pores in the shell cavity of the gas sucked out, so that the liquid metal to better cavity filling, copying the shape of the cavity, improve casting accuracy, preventing porosity, water lack of defects. The method has been applied in foreign countries.
3) under the pressure of crystallization
Shell will be pouring on the pressure tank, immediately after the closure of the pressure tank, the tank access to high-pressure air or inert gas, so that solidification of the casting under pressure to increase the density of the casting. Maximum pressure reached in the foreign 150atm.
4) directional crystallization (solidification)
Some castings, such as turbine blades, magnet, etc., if their crystal structure is arranged in a certain direction of the columnar grains, their performance will improve a lot, so directionally solidified casting technologies are rapidly developed.
Casting the clean-up
Castings mainly for the clean-up:
(1) removed from the casting shell;
(2) Remove from the water system to take castings;
(3) removal of the casting shell on the adhesion of refractories;
(4) cleaning up after casting heat treatment, such as the addition oxide, although remnants of the gate edge and cutting and so on.