Improving The Design In Bucket Teeth Center

In the analysis of total service life of bucket teeth, we must design the center position of bucket teeth by wear rule to solve the problem of large resistance in the early using stage. So bucket teeth center must be higher than installing center in designing. If the bucket teeth has been moved high, the slope on the bucket teeth will become smaller. At this time, its wear should be decreased and it is easy to shovel the ore.

Don’t move the center up too much. Because mostly moving up will make the service life of the bucket teeth decrease. But move the center up about 40mm will be better.

There are separate gas hole, blowhole and reaction blowhole in the kneading castings. In the constitute process of shrinkage hole and shrinkage porosity, mostly accompanied by gas separation. If it has too high gas content or too much gas all will increase the shrinkage or porosity composition. We can easily see that the stomatal distribution is random and often with large hole. They are mostly spherical and balls. So we can determine that porosity is belongs to the blowhole.

Why Does Bucket Teeth Casting Cause Hot Cracks

One day, worker find that there is transverse crack below the pulp cavity hole of bucket tooth. It is easy to be found on the casting surface. The crack section of is in serious oxidation and without any metallic luster. The crack shape is tortuous and irregular. The crack on the casting surface has large width and even present lacerate. So we can ensure that crack  belongs to thermal crack in essence.

Thermal crack is caused during the solidified process and the casting is in the plastic deformation statue. Metal liquid start to freeze under the wall heat transfer effect from the casting surface. Then appear a large number of dendrite and build a complete skeleton. If the casting frozen without any hindrance, bucket tooth casting shrinkage free and the internal  produce stress gradually. If the contracts of dendrite layer is limited by type and core, the dendrite layer will own tensile stress. When the tensile stress is more than the film strength limit. The dendrite will be pulled open. In order to ensure the casting not cause hot crack, there must be enough metal liquid and flow to the crack position.

There is a tensile stress in the core pulling process. At the same time, artifacts will produced resistance in the core pulling direction due to the runner has been solidified at this time. This resistance is an opposite direction of the tensile stress. If these two tensile stress have bigger effect than the yield stress under high temperature, it will make the bucket teeth pulled open and even form thermal crack.