In the production process of Lead Die Casting , the labor union encountered various quality problems, and the reasons were numerous. During the production process, we must make correct judgments on the quality problems that occur, and find out the real causes, so that we can propose corresponding practical and effective improvement measures to continuously improve the quality of die castings.
The first is undercasting: that is, during the forming process of the die casting, the filling of certain parts is not complete, we call it undercasting. When the lack of casting is serious, it can be regarded as the shape of the casting does not conform to the drawing. Usually, we don't allow undercasting to exist in the production process.
The reasons for the under-casting are: (1) The filling condition is poor, and the under-casting part shows irregular condensed metal. When the pressure is insufficient or insufficient and the metal at the flow front solidifies prematurely, under-casting occurs in corners, deep recesses, thin walls (even thinner than the average wall thickness), and cylindrical hole walls. Excessive mold temperature, low-alloy pouring temperature, and poor position of the inner gate, resulting in relatively large flow resistance.
(2) The gas is obstructed, the surface of the under-casting part is smooth, but the shape is irregular and it is difficult to set up an overflow system. When the gas accumulates in the flow of the molten metal, the turbulence is severe and envelops the gas.
(3) There are residues in the mold cavity. The amount of paint or improper spraying method caused the coating to be partially deposited. The inlay gap of the molded part is too large, or the sliding fit gap is too large. It can be completely taken out and be sandwiched in the gap. When this kind of sheet metal protrudes more on the surrounding molding surface, the height of the protrusion is changed to the wall thickness of the casting when the mold is closed, so that the subsequent castings will have a penetrating groove there. . This penetrating groove will become a special form of undercasting. This kind of undercasting phenomenon mostly occurs in the case of a deep cavity composed of inlays. On the vertical die-casting machine, when injecting, the lower punch moves down to make the nozzle orifice insufficient, resulting in a series of poor filling conditions.
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