V method casting and epc also called negative pressure casting, Vacuum by taking English (Vacuum) of the word “” V” for the name.It different from traditional sand casting’s,the biggest advantage is that do not use glue, V method casting is the use of plastic film sealing sand box, the air inside by draw out type vacuum extraction system, mold, both inside and outside differential pressure, the density of dry sand, the formation of the cavity and the core, box, pouring vacuum casting solidification, remove negative pressure, casting sand with the pieces.
V method casting and epc compared with the traditional sand casting, has the following advantages:
The first, because of the suction pouring casting sand holes stomata, product high compactness, smooth surface, less size outline clear and accurate;
Second, the energy conservation and efficient cleaner production.V method and mold technology can make the dry sand repeatedly use, need not drying type, coal consumption is reduced, but due to long vacuum machine operation, power consumption increases slightly, but greatly reduce dust, save human capital, and make the casting work more efficient, save labor and greatly reduce the labor intensity, less harmful gas in the process of casting, truly realizing green production.
V key point is to select the vacuum extraction system, method of production at the time of use vacuum extraction system, the first thing to determine the capacity of vacuum pump, mainly consider the following factors:
1, needs to work under vacuum at the same time, the size and number of the sand box;
2, at the same time, the number of mold casting;
3, the size and shape of the casting;
4, close to the membrane permeability on the surface of the mold, it controls through the plastic film on the gap amount of air into the mold, thus when pouring, it is necessary to use a small amount of mold coating, it helps to provide vacuum machine with a “secondary seal layer”
1, the manufacture with a suction box and stomatal type plate;
2, will be roasted in a plastic state of plastic film covering on the type plate heat, temperature between 80 ℃ to 120 ℃, and at the same time, the vacuum pump suction thin film shape stick on the plate mill;
3, to filter with exhaust tube sand box on the template has good covering plastic film;
4, to the sand filling without binder and additive in the dry quartz sand particle size is 100-200 purpose, borrow microtremor sand compaction, leveling, put a seal of thin film, open the valve to sand in the air, make the mold exists pressure difference inside and outside (about 300 ~ 400 MMHG).Due to the effect of differential pressure casting molding And has high hardness, wet durometer readings of up to 95 or so;
5, remove template in vacuum, then carries on the draft.Mold to continue until vacuum pouring casting solidification.According to the type under the rule of law;
6, the core and box, pouring;
7, after being metal solidification, stop for extraction of the mould, when the internal pressure is close to atmospheric pressure mold itself to pieces.
Vacuum extraction system consists of vacuum pumps, buffer tank, dust removal tank and pipeline valve link.Vacuum degree of vacuum pump and the selection of swept volume V method of modelling the key to success.In the production of high vacuum degree in commonly – 66500 pa (- 500 MMHG).
Buffer tank is a sealed container, its role is mainly stable vacuum pressure system, buffer system pressure influence on modelling, also have the effect of a filter dust.
Sandbox for a long time the recycle and pouring molten iron to the destruction of the sandbox screen pack is easily damaged, the sand was caused loss in the suction vacuum pump, had better be in into the vacuum pump money increase dust catcher, link dust removal tank the last into the liquid ring vacuum pump, to ensure that the service life of vacuum pump.
Foundry industry gave birth to a new kind of casting process – V method casting.V method casting shape, namely vacuum seal principle is the use of plastic film sealing sand box, use the air inside a pump type, both inside and outside the mold to form pressure difference and make the dry sand tight, in order to form the cavity.V method different from traditional sand casting’s biggest advantage is that do not use glue, and thus reduce the blasting work, and modelling and also greatly reduce the amount of labor of adhering sand cleaning of castings, sand recovery rate can reach more than 95%.
V method casting process to produce castings of good quality, smooth surface, clear outline, size accurate, uniform hardness, effectively prolong the service life of the casting, praised by users, become industry to be bestowed favor on newly.