Research on high efficiency cleaning equipment and process of resin sand core

The effect of different NaOH solution concentration, excitation force and core heating temperature on the efficiency of dissolution vibration cleaning was studied by using the dissolution vibration cleaning technology to clean the core. When the heating temperature of the core is 300 ℃, the influence curve of different NaOH solution concentration and exciting force (characterized by the angle of the eccentric block of the vibration motor, the same as below) on the efficiency of dissolution vibration cleaning.

As can be seen from fig. 10, the sand drop rate of the core increases with the increase of NaOH solution concentration. When the concentration of NaOH solution is 2.5-7.5 wt.%, the sand drop rate of the core increases first and then decreases with the increase of exciting force, and the sand drop rate is the largest when the angle between eccentric blocks is 3/18mm. However, when the cleaning liquid is water, the reaction of alkali solution dissolving the core does not occur, the sand drop rate is almost o. At this time, the magnitude of the excitation force has no obvious effect on the sand drop rate of the core sample, which indicates that vibration can only promote the cleaning speed of the core sample dynamically.

In the process of dissolving vibration cleaning, NaOH solution can dissolve and soften the core sample in the process of soaking the core. Silica sand (mainly SiO2) in the core and NaOH can undergo an exothermic chemical reaction. The heat released by the reaction will promote the reaction between SiO2 and NaOH. The sodium silicate generated by the reaction is soluble in water. During this process, the external force will accelerate the sodium silicate to fall off from the surface of the core sample, the sodium sulfate is released from the surface of the core sample, thereby accelerating the reaction. From the analysis of reaction thermodynamics, the greater the concentration of NaOH solution, the faster the reaction rate, and the greater the reduction of core mass in a certain period of time.

In the dissolution vibration cleaning process, the vibration can make the reaction of silica sand and sodium hydroxide solution fall off from the surface of the core sample quickly, and speed up the cleaning efficiency of the core. During vibration cleaning, the casting is thrown up and down to collide with the body. When the relative speed is the maximum, the sand drop rate is the best. At this time, the vibration motor collides with the casting once every time the spindle rotates. The time interval between the two impacts is the same as the vibration cycle of the vibration motor, and the cleaning effect is the best.

In the actual pouring process, the heating temperature of different parts of the core is different, so it is necessary to study the effect of different core heating temperature on the efficiency of dissolution vibration cleaning.

As the heating temperature of the core increases from 250 ℃ to 400 ℃, the cleaning efficiency of the core gradually increases. The influence of the heating temperature of the core on the cleaning efficiency is as follows:

(1) The higher heating temperature will cause the bonding bridge of the coated sand core sample and the binder film of the coated silica sand to burn more seriously, and the binder film will have defects such as cracks, thereby reducing the residual strength of the core, so it is easy to clean;

(2) the more serious the burning of the adhesive film. The more exposed silica sand, which increases the contact area of silica sand and NaOH solution, the more conducive to the occurrence of chemical reaction between silica sand and NaOH solution, thereby improving the cleaning efficiency of the core. Therefore, the heated temperature of the core has a greater impact on its post-casting cleaning.