Why There Are Heat Cracks On Tooth Casting

There appear irregular cracks on some tooth casting, which are called the heat cracks. Then how the heat cracks come about?

The heat cracks appear during the process of solidification, when the casting is in the plastic property and deformation state. The shape of these cracks is tortuous and irregular. And its formation is mainly caused by the uneven shrinkage of the forming components. In the filling process of the parts, the matters such as the uneven distribution of mold temperature field, a relatively low forming pressure, and ineffectively feeding, will cause the uneven shrinkage of the forming parts. In the casting process, the solidification time of different casting parts are not the same, due to which there will exists two tensile stress in the opposite direction during the core pulling. If the two tensile stresses is greater than the stress effect of material under high temperature, the bucket tooth workpiece will break in the weak point, and then the heat cracks come about.

Fixing Method For Bucket Tooth And Bucket Lip After Assembly

In the whole process of using an electric excavator, maintaining long-term careful examination and being diligent in repair can always keep the bucket tooth closely matched with the bucket lip, so as to help the electric excavator shovel works and operates safely and efficiently.

Firstly, at the time of the installation of new electric excavator, accurate mapping size of outer assembly binding geometry parts of the inside bucket teeth and the bucket lip, and make out templates. Then after repeated testing and physical modification, finally draw the pattern out.

In the working process, use the bucket tooth model to test if the bucket tooth new parts assembly parts is qualified, with bucket lip model in the late using process of bucket to test the wear volume of the bucket lip. If the bucket lip has any wear or tear, use the intermittent time of maintenance and repair or replacement of bucket tooth equipment to bead weld on the wear parts of the surfacing, and polished it anastomose to the model, and then install the new bucket tooth.

Why The Excavator Bucket Tooth Casting Has Stomata

The stomata in bucket teeth casting is formed in the process of squeeze casting. In the process of liquid metal filling, the gas which has not been discharged will be entrapped into the liquid metal, and subsequently float. The floating rate of the gas is mainly related to the liquid metal viscosity. With the decrease of temperature, the liquid metal viscosity increases. When the liquid metal viscosity increases to a certain extent, the bubble buoyancy velocity tends to zero, then the bubble stops floating up but stay in the liquid metal. Then the stomata are informed.

The main reason for this situation is the unsmooth exhaust of casting mold. Gas in the cavity can not be discharged smoothly. In the filling process, the gas will be stored between the mold cavity and the liquid metal. Since the liquid metal can not completely dissolve the gas, and the part of the metal liquid which firstly contacts air will form a thin solidification shell in advance, the gas is which has not been discharged will gather in a certain internal region and finally the stomata appear. At the same time, as the squeeze casting is under high pressure to do the filling and solidification of liquid metal, the gas above will be compressed rapidly, thus creating conditions for the formation of bucket tooth stomata.

Abrasion Of Bucket Tooth Influences Cutting Force

According to the degree of abrasion of bucket teeth, we divided the bucket tooth into 3 levels. Level zero wear, i.e. the new bucket tooth without abrasion; the intermediate, namely the bucket tooth whose radial abrasion length is 6mm or so and the average abrasion surface is about 22mm; the heavy wear, namely the bucket tooth whose radial abrasion is more than or equal to 15mm and the average length of the wear surface is more than or equal to about 30mm.

The experiment proved that abrasion has the following effects of cutting force of bucket tooth. First, the cutting force increased, especially heavy wear, line cutting force is 6 times larger than that before the wear. Second, the normal force increased with the bucket tooth becoming dull due to the abrasion. The normal force of the intermediate wear increases about 3 times, while that of the heavy wear increased 8 times. Third, from a macro perspective, in the cutting process, with the intermediate or heavy wear the vibration of the machine itself is bad, and the digging resistance increases significantly. Obviously, it is extremely unreasonable of excavator working in such bad condition, and this will cause damage to the transmission parts, make the equipment power greatly overload, shorten the machine service life, and also reduce production capacity.

Excavator Working Principle

Excavator is a kind of fixed assets with large economic investment. In order to improve the service life of it, every excavator should be equipped with one responsible person.


In the construction site, the driver should first observe the geology of working surface and the surrounding environment condition to see if there are obstacles, so as to avoid scratch or damage to the vehicle.


After launch, there should not be any person standing in the bucket, the shovel arm or the track, to ensure safety in production.


When excavator at work, there should not be any person stay or walk in the radius of gyration range or under the bucket. People without Operation certificate should be forbidden to enter the cap, so as to avoid damage to electrical equipment.


Before moving the excavator, the driver should observe surroundings and whistle, in order to avoid accidents. Ensure the location which the excavator will be moved to is without any obstacles in the rotation radius of the space.


After the end of the work, the excavator should be moved away from the low-lying or a geosynclines’ edge. Park it on the ground. Close and lock the doors and windows. The driver must do a good job of equipment routine maintenance, and if there are problems with the vehicle, the responsible person should report the problems and repair it timely.

Excavator Daily Maintenance

Daily inspection is to ensure that the hydraulic excavator is able to maintain the efficient operation of the important link in long term, especially for the self-employed. In addition, doing perfect daily inspection can reduce the maintenance costs.

First, turn two laps around the machine to check the appearance and mechanical chassis, and see whether there is oil outflow on slewing bearing. Then check the deceleration and braking device and bolt fastener of the track. Tighten the screw, and the change what need changing in time. If your excavator is wheel excavator, you need to check the wheel and pressure stability.

Check whether there is large wear of excavator bucket tooth. It is shown that the wear tooth will substantially increase the resistance of the construction process, seriously affect the work efficiency, and increase the wear degree of the equipment spare parts.

Check the bucket rod and cylinder to see if there is a crack or leakage. Check the battery electrolyte, avoiding it is at a low level line.

The air filter is to prevent a large number of dusts into the important parts of excavators, so it should be regularly checked and cleaned.

Often check the fuel, lubricating oil, hydraulic oil, coolant, and so on. Add the proper oil in accordance with the instructions, and keep it clean.
                                        

The Application of the Excavator

Excavator is one of the main construction machinery of earth and rock engineering. It is mainly composed of power plant, transmission, action, slewing mechanism, operating mechanism, electrical equipment, work device and so on. The working device can be according to the requirements of different variable for several types, so it is widely used in highway, railway, construction, mining, national defense, and other projects. According to statistics, more than 60%’s earth and rock engineering is completed by excavator. At present, backhoe excavator is mainly used in highway engineering. Backhoe excavator is mainly used for excavation conditions in the highway construction, and its basic practices have ditch excavation and excavation of the side ditch.

To sum up, the excavator is applied in excavating material which is higher or lower than the bearing machine and load into transport vehicles or discharge to the stocking yard earthmoving machines. Excavating material is mainly loose soil, coal, sediment, and the soil and rocks. From the point of the development of construction machinery in recent years, the development of the excavator is relatively quickly, and the excavator as one of the main engineering machinery model in engineering construction, its right selection is more important. At the same time, when meeting with the geological disasters such as typhoon, earthquake, and mud-rock flow, excavators have also played a decisive role, alleviate sufferings to the victims.