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ADVANTAGES OF THE COUNTER-PRESSURE CASTING METHOD
The acting “counter pressure” suppresses the release of the gases present in the melt keeping them in a dissolved state thus eliminating the gas porosity in the casting.
The solidification of the metal in the die cavity proceeds, being under
the action of the gas pressure in the die housing and that of the melt
pressure at the die inlet. That significantly:
- Improves the conditions for melt infiltration and efficient feeding of the casting and prevent the formation of the associated with shrinkage of the metal defects like macro porosity and cavities.
- Improves conditions to eliminate or reduce “natural” micro porosity, result of better infiltration of the melt between arising crystallites and plastic micro deformation them in the process of crystallization.
- Prolong time of contact between die and solidifying metal in die cavity before creation the shrink gap increase the depth of fine macro structure result of longer intensive heat transfer to die. That increase the mechanical properties of the cast material and combined with above advantages improve structural strength of the casting.
An integral structure can be obtained even in thick sections in the upper part of castings without the use of risers. If, however, small risers are used in some cases, they work under the same gas pressure, their efficiency being increased many times. That makes the yield of usable castings from the metal poured very high.
Since the whole casting process takes place in closed vessels, the CPC technology provides much better working conditions and minimizes air pollution as well and protective gases could be used with success.
The precision control of creating Pressure Differential
(delta P) permit:
- Precise control of the rate of casting and filling the die. Rate of casting does not depend on the pressure acting on the melt.
- Precise control of the mould filling time. Accurate proportioning of the mechanical energy of the flowing melt, required to fill the mould without turbulence and breaking the melt free surface. Increasing the pressure difference in the end of the die filling in order to obtain a better reproduction. Casting in sand moulds and in permanent moulds with sand cores without any danger of their destruction, regardless of the applied working pressure.
- Realization of directional solidification by suitable changes in the mould filling speed.
Links to articles related to the counter-pressure casting method:
MODERN CASTING - Counter-Pressure Casting System Eases Aluminum Pouring for High Integrity ComponentsINTERMET - Pressure Counter Pressure Casting (PCPC) for Automotive Aluminum Structural Components