There are two main classification methods for sand casting gating system of mud pump body: one is that it can be divided into open type, semi closed type and closed type according to the cross-sectional area of each part of sand casting gating system of mud pump body; The other can be divided into bottom injection, top injection, middle injection and step injection according to the injection position.
1. It is classified according to the cross-sectional area of each part
Σ: sectional area of sprue; Σ: cross-sectional area of runner; Σ: sectional area of ingate
a) When ∑ straight > ∑ transverse > ∑ inner, it is closed
The flow control section is located in the inner sprue. After the sand casting of the mud pump body is started, it is easier for the liquid metal to fill the gating system and show a state of pressurized flow. The sand casting pouring system of the mud pump body has good slag retaining capacity, but the speed is fast during mold filling, and the metal liquid scours the mold wall seriously, which is easy to cause splashing, entrainment and suction during mold filling, resulting in oxidation of the metal liquid. The sand casting gating system of mud pump body consumes less liquid metal and is easy to clean. It is suitable for iron castings.
b) When ∑ straight < ∑ horizontal < ∑ inner, it is open type
The flow control section is located in the sprue. During mold filling, the inner and transverse sprues are usually difficult to fill, showing a pressureless state. The slurry pump body sand casting gating system has poor slag retaining effect, low filling speed, stable filling process, and small scouring force of liquid metal on the mold wall. The sand casting gating system of mud pump body consumes more liquid metal and is difficult to clean. It is commonly used in steel castings, non-ferrous alloy castings and nodular iron castings. Gray iron castings are also occasionally used.
c) When ∑ inner ＜∑ straight ＜∑ transverse, it is semi closed
The flow control section is located in the inner sprue. The mud pump body can be filled with the gating system during sand casting, but later than the closed type. The filling speed is higher than that of open type, but less than that of closed type. The filling process is relatively stable and the slag retaining effect is general. Sand casting gating system of mud pump body is commonly used in gray iron parts and nodular iron parts.
2. Classification according to injection location
a) Top injection
The liquid metal flows into the cavity from the top, and the mold filling speed is fast, which can avoid defects such as insufficient pouring and cold shut. After mold filling, the top temperature of sand mold casting of mud pump body shall be higher than the bottom temperature, so as to form a sequential solidification from bottom to top, which is conducive to riser feeding. However, during sand casting and pouring of mud pump body, the metal liquid washes the mold wall seriously, which is prone to splash, air entrainment, air suction and other phenomena, resulting in defects such as pores, sand holes and oxides. At the same time, the slag retaining effect of sand casting and pouring system of mud pump body is also poor.
b) Middle note type
It can be subdivided into flow control type, steady flow type, filter screen type, sawtooth type and slag collection ladle type. At the same time, it has the advantages and disadvantages of top injection and bottom injection, and the slag retaining effect is general. It is commonly used for sand castings of mud pump body with uniform wall thickness and flat pouring.
c) Bottom injection
The filling process is stable, and the impact of liquid metal on the mold wall is small, which can avoid splashing, oxidation and other phenomena; In the process of mold filling, the runner is basically full, and the sand casting gating system of the mud pump body has a good slag retaining effect; Conducive to exhaust. However, after the mold filling, the temperature at the bottom of the sand casting of the mud pump body is high, and the temperature distribution of the sand casting of the mud pump body is not conducive to the formation of sequential solidification and feeding of the riser; Overheating is easy to occur at the inner sprue, resulting in shrinkage porosity, shrinkage cavity, coarse grain and other defects;
d) Step injection
The liquid metal is filled in layers from bottom to top with the liquid level, and the filling process is relatively stable, which is conducive to exhaust. After mold filling, the temperature of the upper part of the sand mold casting of the mud pump body is higher than that of the lower part, forming a bottom-up temperature distribution, which is conducive to sequential solidification and riser feeding. Using multi sprue pouring can effectively reduce the overheating problem at the sprue. However, the sand casting pouring system of the mud pump body is complex, the modeling is difficult, the “random pouring” phenomenon is easy to occur in the mold filling process, or the liquid metal is easy to be injected from the bottom, resulting in the unsatisfactory temperature distribution of the sand casting of the mud pump body.