Flat cover refers to the head  cover plate with flat surface of the shell. It is also called "flat head" when it is used as the head  "flat bottom" when it is used as the bottom head. Geometric shapes include circle, ellipse, oblong  rectangle. Under the action of pressure, the flat cover mainly produces bending stress,  the joint between the flat cover  other shells produces large discontinuous stress due to the sudden change of geometry. Therefore, under the same diameter  receiving jade, the thickness of the flat cover is larger than that of the head of other shapes.

The utility model has the advantages of simple structure  convenient manufacture. The disadvantages are poor mechanical properties, heavy consumption of materials. It is suitable for normal pressure, low pressure  small diameter high pressure applications. In addition to direct welding with other shells, there are also detachable bolts, such as manhole cover  handhole cover.

The surface temperature control of die casting die is very important for the production of high quality die casting. The uneven  improper mold temperature will also lead to the instability of the casting size, the deformation of the ejected casting in the production process, resulting in defects such as hot pressure, die sticking, surface depression, internal shrinkage cavity  hot bubble. When the mold temperature difference is large, the variables in the production cycle, such as filling time, cooling time  spraying time, will be affected to varying degrees.