Sinostar MACH's Coated Sand Casting technology is very competitive in the industry.

Coated sand casting in the foundry field has a long history, casting production is also quite large;

Shandong Province is currently China's casting film sand manufacturers are more concentrated areas, Sinostar MACH professional film sand casting parts has been more than 15 years of history, the basic technology has been very mature, the current use of film sand casting production of precision steel castings face a number of problems that need to be solved, such as sand sticking (scars), cold barriers, porosity, etc., how to solve these problems remain to be our further exploration and Solve these problems.

Knowledge and understanding of coated sand (coated sand belongs to organic binder type, core sand)

1. Features of coated sand: suitable strength performance; good fluidity, the prepared sand molds and cores have clear contours and dense structures, which can produce complex sand cores; sand molds (cores) have good surface quality and rough surface The degree can reach Ra=6.3～12.5μm, the dimensional accuracy can reach CT7～CT9 grade; the collapsibility is good, and the casting is easy to clean.

2. Scope of application: coated sand can be used to make molds and cores. The molds or cores of coated sand can be used in conjunction with each other or with other sand molds (cores); not only can be used for metal gravity Casting or low-pressure casting can also be used for iron sand-coated casting and thermal centrifugal casting; it can be used not only for the production of cast iron and non-ferrous alloy castings, but also for the production of steel castings.

Preparation of coated sand

1. Composition of coated sand

It is generally composed of refractory materials, binders, curing agents, lubricants and special additives.　　

(1) Refractories are the main body of coated sand. The requirements for refractory materials are: high refractoriness, less volatile matter, rounder particles, and firmness. Generally choose natural scrubbing silica sand. The requirements for silica sand are: high SiO2 content (cast iron and non-ferrous alloy castings are required to be greater than 90%, steel castings are required to be greater than 97%); mud content is not greater than 0.3% (for scrubbing sand)-[Water-washing sand mud content requirements Less than; particle size ①distributed on adjacent 3 to 5 sieve sizes; rounded grain shape, angular factor should not be greater than 1.3; acid consumption value is not less than 5ml.　　

(2) Phenolic resin is generally used as the binder.

(3) Urotropine is usually used as the curing agent; calcium stearate is generally used as the lubricant, which prevents the coating sand from agglomerating and increases fluidity. The main function of additives is to improve the performance of coated sand.

(4) The basic proportion of coated sand is the proportion of distribution (mass fraction, %). Note: Raw sand 100 is scrubbing sand, phenolic resin is 1.0～3.0 accounting for the weight of raw sand, and urotropine (aqueous solution 2) is 10-15 The weight of calcium stearate is 5-7 for the weight of the resin, and the weight of the additive is 0.1-0.5 for the raw sand. 1:2) 10-15 accounted for resin weight, calcium stearate 5-7 accounted for resin weight, additive 0.1-0.5 accounted for raw sand weight.

2. Production process of coated sand 　　　

The preparation process of coated sand mainly includes cold coating, warm coating, and thermal coating. At present, almost all the production of coated sand adopts the hot coating method. The thermal coating process is to first heat the raw sand to a certain temperature, then mix and stir with the resin, urotropine aqueous solution and calcium stearate, then cool, crush and sieving. Due to the difference in formula, the mixing process is different. At present, there are many types of coated sand production lines in China. There are about 2,000 to 2,300 semi-automatic production lines for manual feeding, and nearly 50 computer-controlled automatic production lines have effectively improved production efficiency and product stability.

3. The main product types of coated sand　　

(1) Ordinary coated sand Ordinary coated sand is traditional coated sand. Its composition is usually composed of quartz sand, thermoplastic phenolic resin, urotropine and calcium stearate. No additives are added, and the amount of resin added is usually It is relatively high under certain strength requirements, and does not have the characteristics of high temperature resistance, low expansion, and low gas evolution. It is suitable for the production of castings with low requirements.

(2) High-strength, low-gassing type coated sand features: high strength, low expansion, low gas evolution, slow gas evolution, anti-oxidation. Brief introduction: high-strength, low gas-generating coated sand is an updated product of ordinary coated sand. By adding relevant characteristic "additives" and adopting new The compounding process greatly reduces the amount of resin, its strength is more than 30% higher than that of ordinary coated sand, and the gas generation volume is significantly reduced, and can delay the gas generation speed, which can better meet the needs of casting production. This kind of coated sand is mainly used in the production of iron castings, small and medium steel castings and alloy steel castings. At present, there are three series of this kind of coated sand: GD-1 high-strength low-gassing coated sand; GD-2 high-strength, low-expansion, low-gassing coated sand; GD-3 high-strength, low-expansion, low-gassing and anti-oxidation coating .

(3) High temperature resistant (type) coated sand (ND type) features: high temperature resistance, high strength, low expansion, low gas generation, slow gas generation, easy to collapse, anti-oxidation Introduction: high temperature resistant coated sand is produced through a special process formula technology with excellent high temperature performance (high strength at high temperature, A new type of coated sand with long heat resistance time, small thermal expansion, low gas evolution) and comprehensive casting performance. This type of coated sand is particularly suitable for the production of complex thin-walled precision cast iron parts (such as automobile engine cylinder blocks, cylinder heads, etc.) and high-demand steel castings (such as container corners and train brakes; middle shell parts, etc.) , Can effectively eliminate casting defects such as sand sticking, deformation, hot cracking and pores. At present, the coated sand has four series: VND-1 high temperature resistant coated sand. ND-2 high temperature resistant, low expansion and low gas generation coated sand ND-3 high temperature resistant, low expansion, low gas generation and oxidation resistant coated sand ND-4 High temperature resistant, high strength bottom, low expansion and low outgassing film

(4) Easily collapsible coated sand has good strength and excellent low-temperature collapsibility performance, which is suitable for the production of non-ferrous metal castings.

(5) Other special requirements coated sand In order to meet the needs of different products, a series of special coated sands have been developed, such as: coated sand for centrifugal casting, chilled coated sand, wet coated sand, anti-sticking sand, and Veining, anti-orange peel coated sand, etc.