In the production process of Shandong Aluminum alloy die castings, many quality problems will be encountered, that is, as a common quality defect of die castings, one of which is under casting. What are the causes of under casting
In the forming process of die casting, some parts are not filled completely, 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 drawing. In general, under casting is not allowed.
The causes of under casting are as follows
1) The filling condition is not good, and there is irregular condensed metal in the under cast part;
When the pressure is insufficient, insufficient, and the metal in the active front solidifies prematurely, under casting occurs in the corner, deep concave, thin wall (even thinner than the average wall thickness) and cylindrical hole wall.
The mold temperature is too low;
The pouring temperature is too low;
The gate position is not good, forming a large resistance.
2) The surface of under cast part is lubricated, but the shape is irregular
Where it is difficult to set up a drainage system, the gas will accumulate;
When the molten metal moves, the turbulence is violent and the gas is entrapped.
3) There is residue in the cavity of plastic mould
Improper amount of coating or spraying method will result in local coating deposition.
成型零件的镶拼缝隙过大,或滑动合作间隙过大,填充时窜入金属,铸件脱出后,并未能被带出而呈现片状夹在缝隙上。当之种片状的金属(金属 片,其厚度即为缝隙的大小)又凸于周围型面较多,便在合模的情况下将凸出的高度变成适为铸件的壁厚,使今后的铸件在该处产生穿透(对壁厚来说)的沟槽。这 种穿透的沟槽即变成欠铸的一种特殊形式。这种欠铸现象多在由镶拼构成的深腔的情况下出现。
The assembling gap of the molding parts is too large, or the sliding cooperation gap is too large, and the metal rushes into when filling. After the casting comes out, it can not be taken out, and the sheet is clamped on the gap. When the kind of sheet metal (the thickness of the metal sheet is the size of the gap) protrudes more on the surrounding mold surface, the height of the projection will be changed into the wall thickness of the casting under the condition of mold closing, so that the future casting will have a groove through (for the wall thickness). This kind of penetrating groove becomes a special form of under casting. This kind of under casting phenomenon often appears in the case of deep cavity made of inlay.
Insufficient pouring material (including too thin residual material section).
On the vertical die casting machine, the lower punch moves down to make the nozzle orifice not enough, resulting in a series of poor filling conditions.