The casting of the front axle of a forklift truck is shown in Figure 1, and the outer dimension is 885 mm × 645 mm × 635 mm, unit weight 472 kg, main wall thickness 33 mm. The material is QT450-10 with spheroidization grade of 1-3; The size of graphite is 5 ~ 6 grades; The hardness of the hook is required to be 160 ~ 210 Hb, each piece needs to have an attached test bar, and the notchless impact energy is greater than 80 J at 23 ℃. The dimension tolerance is iso2768-m. no casting defects are allowed in the front mounting hook of the casting, and no air hole, sand hole, shrinkage cavity, porosity and other defects are allowed in all processing parts of the casting.
It can be seen from Figure 1 that the inner cavity and shape of the casting are complex, and the control points to prevent product scrap are as follows:
(1) The appearance and shape of castings are complex, so it is necessary to design the gating system reasonably to prevent the occurrence of cold shut, shrinkage cavity, shrinkage porosity and other casting defects.
(2) Usingmethod , it is easy to cause box collapse and sand sticking during pouring. It is necessary to strictly control pouring parameters to ensure the smooth filling of molten iron in the mold.
(3) The casting requires high dimensional accuracy and surface quality. The gating system should take effective measures to avoid slag sticking and sand wrapping.
(4) There are many machining holes and surfaces, so it is necessary to control the air hole defects. On the premise of ensuring the strength and concession of the sand core, reduce the amount of resin to reduce the gas generation of the sand core.
(5) The sand core under the complex inner cavity of the casting should be placed smoothly, and the gap between the sand cores should be filled and repaired with sealing paste.
(6) By adjusting and controlling the ratio of C and Si, carbon equivalent, alloy element content, and heat preservation time in the box, the good mechanical properties and hardness value of the material can be ensured.
(7) The reasonable sand particle size index is selected to ensure the surface roughness of the product.