Residues in the mould cavity are one of the reasons that cause under-casting


During the production process of die-casting parts, the […]

During the production process of die-casting parts, there will be many quality problems, that is, as a common quality defect of die-casting parts, one of which is under-casting, which causes the under-casting of die-casting parts. as follows:


During the forming process of die-casting parts, some parts are incompletely filled, which is called under-casting. When the under-cast part is serious, it can be regarded as the shape of the casting does not meet the requirements of the drawings. It is usually not allowed for undercasting.


The reasons for undercasting are:


1) Poor filling conditions, irregularly condensed metal under-cast parts;


When the pressure is insufficient and insufficient, the metal at the flow front solidifies too early, causing corners, deep recesses, thin walls (even thinner than the average wall thickness), cylindrical hole walls and other parts to be under-cast.


The mould temperature is too low;


The pouring temperature of the alloy is too low;


The position of the gate is not good, forming a large flow resistance.


2) Gas obstruction, the surface of the under-cast part is smooth, but the shape is irregular


Where it is difficult to open a drainage system, the gas accumulates;


When the molten metal flows, the turbulent flow is intense, which entraps the gas.


3) There are residues in the mould cavity


Improper amount of paint or spraying method can cause localized paint deposition.


The gap between the moulded parts is too large, or the gap of the sliding fit is too large. When filling, the metal enters. After the casting is taken out, it is not completely brought out and appears to be clipped on the gap. When a piece of sheet metal (the thickness of the metal sheet is the size of the gap) is more protruding from the surrounding profile, it will change the height of the protrusion to the wall thickness of the casting in the case of mould clamping, so that Subsequent castings produce grooves that penetrate (to the wall thickness) at this point. This penetrating groove becomes a special form of under casting. This under-casting phenomenon occurs mostly in the case of deep cavities composed of mosaics.


Insufficient pouring material (including the remaining material section is too thin).


On the vertical die-casting machine, the lower punch moves downward during injection to make the nozzle orifice insufficient, resulting in a series of poor filling conditions.

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