In the production process of die casting parts, many quality problems will be encountered, that is, as a common quality defect of die casting parts, under-casting is one of the defects. What are the reasons for under-casting of die-casting parts? The analysis is as follows:
During the forming process of die casting, some parts are not filled completely, which is called undercasting. When the lack of casting is serious, it can be regarded as the shape of the casting not meeting the requirements of the drawing. Generally speaking, undercasting is not allowed.
The reasons for undercasting are:
1) Poor filling conditions, irregular condensed metal in the undercast part;
When the pressure is insufficient, insufficient, and the metal at the front of the activity solidifies prematurely, the corners, deep recesses, thin walls (even thinner than the average wall thickness), cylindrical hole walls and other china die casting parts are under-cast.
- The mold temperature is too low;
- The alloy pouring temperature is too low;
- The position of the inner gate is not good, resulting in a large movement resistance.
2) The gas is obstructed, the surface of the under-casting part is lubricated, but the shape is irregular
It is difficult to set up an overflow system, gas accumulation;
When the molten metal moves, the turbulence is violent and envelops the gas.
3) There are residues in the plastic mold cavity
Improper amount of paint or spraying method may cause local paint deposition.
The inlay gap of the molded part is too large, or the sliding cooperation gap is too large, the metal enters during filling, and after the casting is released, it cannot be completely taken out and appears to be sandwiched in the gap. When the sheet metal (the thickness of the metal sheet is the size of the gap) is more convex than the surrounding surface, the height of the protrusion is changed to the wall thickness of the casting when the mold is closed, so that Future die castings will create grooves that penetrate (in terms of wall thickness) there. This penetrating groove becomes a special form of undercasting. This kind of undercasting phenomenon mostly occurs in the case of a deep cavity composed of inlays.
Insufficient casting material (including too thin remaining material section).
In the vertical die-casting machine, when injecting, the lower punch moves down so that the opening of the nozzle is not enough, resulting in a series of poor filling conditions.