Tell you the classification of coated sand

Classification of Coated Sand

With the continuous expansion of the application range of coated sand, different casting processes, different material requirements and different structures of castings put forward different performance requirements for coated sand. Since the 1990 s, coated sand with different properties has been developed in China. According to its performance characteristics, the coated sand in the domestic market can be divided into two categories: dry and wet. The dry category includes: ordinary, high temperature resistant, high strength and low gas, easy to collapse, centrifugal casting, etc. Wet coated sand includes two kinds of mechanical and manual. The main components, characteristics and scope of application of all kinds of coated sand are as follows:

1. Coated sand with high strength and low gas

On the basis of ordinary coated sand, through the addition of relevant characteristics of "additives" and the use of new preparation process, the amount of resin is greatly reduced, the amount of gas is significantly reduced, and the rate of gas generation can be delayed. The coated sand has the characteristics of high strength, low expansion, low gas generation, slow gas generation, etc., and is especially suitable for iron castings, small and medium steel castings requiring low gas generation, such as valve body sand core.

2. Ordinary coated sand

Its composition is usually composed of quartz sand thermoplastic phenolic resin, urotropine and calcium stearate, without relevant additives. The amount of resin added is usually relatively high under certain strength requirements, and does not have the characteristics of high temperature resistance, low expansion, and low gas generation. It is suitable for the production of cast iron parts with low requirements and simple structure.

3. Centrifugal casting coated sand

The coated sand is suitable for centrifugal casting process, and it can be used to replace coating to produce centrifugal casting pipe. According to the casting pipe material and diameter size and technical requirements, can be processed into different properties of centrifugal casting coated sand. The difference with other types of coated sand is that the density of the coated sand is higher, the gas generation is lower and the gas generation speed is slow.

4. High temperature resistant coated sand

The sand generally refers to the high thermal strength of the coated sand, long heat resistance time, and small high temperature deformation, rather than its high refractoriness. It is through a special process formulation technology (usually in the silica sand coating to add a certain amount of inert materials such as milling sand, high chromium ore, carbon containing materials or other inert materials, etc.), to produce a new type of coated sand with excellent high temperature performance and comprehensive casting performance. It has the characteristics of high temperature resistance, high strength, low expansion, low gas, slow gas and so on. It is especially suitable for the production of complex thin-walled precision cast iron parts (such as automobile engine cylinder block, cylinder head, etc.) and high-demand cast steel parts (such as container angle and train brake buffer shell, etc.), which can effectively eliminate the casting defects such as sand sticking, deformation, thermal cracking and porosity.

5. Wet hand-coated sand

The wet compressive strength of the coated sand can be arbitrarily adjusted within 0.1 ~ 0.3MPa. The storage period is more than 3 months. It is suitable for manual molding or core making (similar to tung oil sand and fat sand). After demoulding at room temperature, the mold (core) is placed in an oven or oven for heating. The heating temperature is 250~350 ℃, and the heating time is 3~10min. The cured mold (core) has the characteristics of high strength, low gas emission, small creep deformation, and no moisture absorption. The coated sand is suitable for the production of single piece, small batch and high precision castings, especially suitable for township enterprises. It is worth noting that when the type (core) is heated and cured, it must wait for the furnace temperature to reach the required temperature before it can be heated, and it must not be heated with the furnace temperature.

6. Wet mechanical coated sand

It is a kind of coated sand which is wet at room temperature. Long-term storage at room temperature will not naturally solidify (can be stored for more than 1 year). According to the technical requirements of different castings, coated sand with various characteristics such as wet high strength and low gas emission can be used. The coated sand can completely replace hot core box sand (the shooting head of core shooting machine does not need to be modified to produce various materials and various types of castings).

7. Coated sand that is easy to collapse

It is a kind of coated sand developed for non-ferrous metal (especially aluminum alloy) casting is not easy to clean sand. The sand has good strength and excellent low temperature collapsibility. It is used to produce non-ferrous metal (aluminum alloy, copper alloy, etc.) castings. It does not need to reheat the castings to clear the sand. It only needs to cool the castings after pouring for 24 hours and then vibrate the sand.

This article is finished by coated sand, the point of view of this article does not represent the point of view of this site.