One minute to understand the composition of coated sand

Ordinary coated sand is composed of quartz sand, thermoplastic phenolic resin, curing agent and calcium stearate, without any additives. Applicable to the production of general cast iron parts. High strength and low gas coated sand is a new product of common coated sand. It is prepared by adding relevant additives and using new technology. Its strength is more than 30% higher than that of ordinary coated sand, and the gas generation rate is obviously reduced. Suitable for the production of complex precision cast iron parts. High-temperature coated sand has the characteristics of high strength at high temperature and long heat resistance time, and is suitable for the production of complex thin-walled cast iron parts such as automobile engine cylinder block, cylinder head, container corner, etc. Coated sand has good strength and excellent low temperature collapsibility, suitable for the production of non-ferrous metal castings. Other special coated sand, in order to meet the needs of different products, developed a series of special coated sand.

At the same time, the newly developed fast curing coated sand can increase the curing speed by 30-70% on the basis of various properties, effectively improve production efficiency and save energy. The required inspection indexes of coated sand specified in the industry standard of coated sand are: normal temperature flexural strength, thermal flexural strength, loss on ignition, particle size and melting point. Optional test indicators include: normal temperature tensile strength, hot tensile strength, gas evolution, fluidity. In recent years, the performance of coated sand has been greatly improved, and some new detection indicators have been added accordingly:

(1) High temperature compressive strength 3354 simulate the actual situation of the casting, and test the compressive strength of the coated sand core at 1000-1500.

(2) The heat-resistant time is the time when the coated sand core is tested to maintain strength at high temperature (700-1500) without deformation or collapse.

(3) shelling resistance, testing the shelling resistance of coated sand.

The main problems in the detection of coated sand are:

1. The detection means of most enterprises are not perfect. Basically stay in the detection of normal temperature strength, melting point, particle size and gas evolution in the primary stage.

2. The precision and stability of domestic coated sand detection equipment are not high. Under the field conditions of different manufacturers, the performance index of coated sand tested by the same equipment is sometimes very different. For example, the tensile strength at room temperature may differ by more than 10kg and the gas release may differ by more than 5ml. Advanced coated sand testing instruments include high temperature performance tester, gas generator, thermal strength tester, etc.

According to statistics, there are nearly 1,000 coated sand production enterprises, most of which have an annual production capacity of less than 1000 tons, and less than 10 have an annual production capacity of more than 10000 tons. The technical level and testing methods of each plant are quite different, and the current situation of coated sand production is discussed from the aspects of raw materials, production equipment, production process and testing.