Key Points Of Foundry Technology Of Coated Sand

Release time：2021-10-12

Heating Temperature 200-300, curing time 30-150s, shot pressure 0.15-0.60 MPA. The sand core with the simple shape and the resin coated sand with good fluidity can select lower shooting pressure, lower heating temperature for thin sand core, longer curing time when the heating temperature is low. The resin used in coated sand isphenolic resin. The advantages of the core-making process are Proper Strength Property; good fluidity; good surface quality of sand cores (Ra 6.3-12.5 m); strong moisture absorption of sand cores; good collapsibility; easy cleaning of castings.

1.Mold temperature: Mold temperature is one of the main factors affecting the thickness and strength of the shell layer, generally controlled at 220 ~ 260, and selected according to the following principles:

(1) ensure that the resin on the coated sand is softened and cured with sufficient heat;

(2) ensure that the required shell thickness is formed and that the surface of the Shell (core) is not charred;

(3) shorten the time of crusting and hardening as far as possible to improve productivity.

2.Sand shooting pressure and time: Sand shooting time is generally controlled at 3 ~ 10s, too short time can not molding sand (core). The shooting sand pressure is generally about 0.6 MPA when the pressure is too low, it is easy to cause the phenomenon of insufficient firing or loose. 3. Hardening time: the length of the hardening time depends mainly on the thickness of the sand mold (core) and the temperature of the mold, generally around 60 ~ 120 S. If the time is too short and the shell layer is not fully solidified, the strength is too low, if the time is too long, the surface layer of the sand mold (core) will be scorched easily, which will affect the casting quality.

when shooting sand, the Compressed air quickly enters the sand shooting cylinder, pushes the sand through the sand layer gap, forms the sand airflow, causes the core sand to shoot into the core box with a higher speed, at the same time filling the core box to obtain the compactness.

There are many kinds of methods to solve the problems in the application of coated sand, which can be divided into two kinds: thermosetting method and cold-setting method. Any core-making method has its own advantages and disadvantages, which mainly depends on the product quality requirements, complexity, production batch, production cost, product price, and other factors to decide which core-making method to use. It is very effective to use coated sand to make sand cores with the high quality of inner cavity surface, high dimensional precision and complex shape. For example INLET AND OUTLET CHANNEL SAND core, waterway sand core, oil channel sand core, water channel sand core of cylinder body, inlet manifold, exhaust manifold shell core, flow channel sand core of hydraulic valve, automotive turbocharger, air duct, sand cores, etc… But in the use of coated sand often encounter some problems, there is only a brief talk about the work of the experience.