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Foam lost foam casting process control and taboo technology

Sources:本站 | Release date: 2017-09-09 | Browsing volume:
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Foam lost foam casting process control and taboo technology
 A: The definition of foam lost foam casting:
EPC, also known as foam solid casting, a foamed plastic polymer materials, such as EPS, STMMA or EPMMA be produced with cast part structure to be produced, exactly the same size of the real mold, (refractory wash dip through fortify , Smooth, breathable) and dried, buried in dry quartz sand by three-dimensional vibration modeling, molding sand box in the negative pressure poured molten metal solution, the polymer material model by heating gasification, and was Liquid metal instead of cooling and solidification forming a one-time casting new process for the production of castings casting method.

Second: the foam disappeared Die Casting called:
The main domestic call "dry sand real casting", "negative pressure real casting"

Three: Foam lost foam casting process control:
The main process include: Riser system design, pouring temperature control, pouring operation control, negative pressure control.
Casting system in the lost foam casting process has a very important position, is casting a key success or failure. Due to a wide variety of castings, different shapes, each casting specific production processes have their own characteristics, and vary widely. These factors have a direct impact on the accuracy of the casting system design results.
Gating system design and the traditional sand casting have some differences. In the pouring system design, should take into account the particularity of this process, pouring system section size and casting size, model cluster combination and the number of cases per case are related.
Model cluster combination can basically reflect the characteristics of castings, as well as the form of castings. Due to the existence of model clusters, the behavior of molten metal after pouring is very different from that of sand casting. In the pouring process, the model gasification needs to absorb heat, so the pouring temperature of the lost foam casting should be slightly higher than the sand casting. For different alloy materials, compared with the sand casting, the pouring temperature of the lost foam casting is generally controlled higher than the sand casting 30 ~ 50 ℃. This is higher than the 30 ~ 50 ℃ liquid metal heat to meet the model of gasification needs heat. Casting temperature is too low castings prone to inadequate pouring, cold insulation, wrinkles and other defects. Casting temperature is too high prone to sticky sand and other defects.
When designing the sectional size of each part of the casting system, the resistance caused by the existence of the model should be taken into account when the lost foam casting metal liquid is poured, and the minimum flow blocking area should be slightly larger than that of the sand casting.
Negative pressure is the necessary measure of black alloy lost foam casting. The role of negative pressure is to increase sand strength and stiffness of the important guarantee measures, but also the model gasification products excluded the main measures. Negative pressure and the size of the holding time and casting material and model cluster structure and paint related. For better breathability, coating thickness of less than 1mm of paint, the negative pressure on cast iron size is generally 0.04 ~ 0.06MPa, for the upper limit of castings. Negative pressure on the size of cast aluminum parts generally controlled at 0.02 ~ 0.03MPa. Negative pressure holding time according to the model cluster structure may be, the larger the number of model clusters per case, may be appropriate to extend the negative pressure hold time. Casting surface is generally solidified crust to a certain thickness to stop negative pressure. For the coating thicker and poor permeability of the paint, may be appropriate to increase the negative pressure and hold time.

Four: Foam foam casting taboo:
Lost Foam Casting The most taboo casting operation is intermittent casting, so easily lead to cold septal defects casting, that is, the temperature of the molten metal pouring is reduced, resulting in a cold interval with the pouring of the liquid metal. In addition, the lost foam casting casting system to use more closed gating system to maintain the stability of the casting. In this regard, the form of pouring cup and pouring operation is stable and close. Pouring should be kept pouring cup liquid level remained stable, so pouring dynamic pressure head steady.
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