Casting in HTS forms

The main advantage of the casting process in HTS is that the finished forms can be used repeatedly for casting parts. If your company is interested in reducing costs, then the HTS casting technology will be the optimal solution for you.

The term HTS-process in modern metallurgy refers to the method of manufacturing rods and molds for casting from free-flowing self-hardening mixtures. The composition of such mixtures (which undergo blowing with the help of various gas reagents) usually includes tar and sand components. The use of sand-clay molds in the casting process makes the production of castings much safer from an ecological point of view.

Advantages of HTS technology :

• low equipment cost and short production times;

• high strength of the produced forms/rods;

• HTS can be used in the production of castings of almost any configuration from ferrous and non-ferrous alloys;

• there are no influxes and deviations from linear dimensions;

• it is possible to obtain clean surfaces without treatment

    minimal allowances (2-3 mm) are given on the treated surfaces;
    casting pores and shells are practically absent;

• casting weight is lower due to smaller allowances and better surface quality.

The final cost of a casting produced by HTS technology is comparable to casting in the ground, despite the fact that the price per kg for casting in HTS molds is higher than for casting in the ground. It is also necessary to take into account a significant reduction in the number of marriages, a reduction in the time spent on mechanical processing of the part and an increase in the resource of the tool.

Metal casting in the mold

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A better way. A mold is made - a collapsible form (most often metal) into which casting is carried out. After solidification and cooling, the mold is opened and the product is removed from it. The mold can then be reused to cast the same part. Unlike other methods of casting into metal molds (die casting, centrifugal casting, etc.), in mold casting, the mold is filled with liquid alloy and solidified without any external influence on the liquid metal, but only under the influence of gravity.

Casting according to molten models (LVM)

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The method of casting - according to the molten model - has been known since ancient times. It is used for manufacturing parts of high precision and complex configuration, which are impossible with other casting methods (for example, turbine blades, etc.).

Made of low-melting material: paraffin, stearin, etc. . The model compound P50C50, which consists of 50% stearin and 50% paraffin, was most widely used; for large-sized products, salt compounds less prone to gouging are used.

The advantages of this method: the possibility of manufacturing parts from alloys that cannot be machined; production of castings with dimensional accuracy up to 11-13 quality and surface roughness Ra 2.5-1.25 μm, which in some cases eliminates cutting processing; the possibility of obtaining machine assemblies that would have to be assembled from separate parts using conventional casting methods.

Casting according to molten models is used in conditions of single (experimental), serial and mass production.

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Due to the high consumption of metal and the high cost of the LVM process, only critical parts are used.

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The process of casting for molten models is based on the following basic principle:
   • A copy or model of the final product is made of a low-melting material.
   • This model is surrounded by a ceramic mass that hardens and forms a shape.
   • Upon further heating (punching) of the mold, the casting model is melted and removed.
   • The cavity left in place of the removed wax is then filled with metal that exactly reproduces the original casting model.

Casting according to gasified models (LGM)

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One of the new promising types of casting in the 50s was casting according to gasifying models (LGM). Today, this method is successfully used all over the world by both world giants in casting production and small factories. In this way, parts weighing from 10 grams are equally successfully cast, while obtaining castings with a surface purity of Rz40.

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The technology involves the presence of a form made of foam plastic. Everyone has held this material in their hands at least once: packaging of household appliances, disposable dishes and modern wall insulation, packaging material for parcels. The shape is obtained by sintering foam powder in aluminum molds. As a result, a high-precision form is obtained, on which you can measure the building part and inspect the prototype.

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The model is connected to the sprue and forms a pot for pouring. Hot metal in the pouring process replaces the model that evaporated under the temperature, completely repeating its contours. The cooled part is pulled out of the sand, the casting is cut and cleaned of the remains of the non-stick coating without much effort.

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• Forming blocks of models in a furnace - for these purposes, a foundry furnace is used - a steel box in which the walls and bottom are equipped with vacuum wires for uniform discharge. The model block is placed in the center of the furnace so that the distance to the walls is approximately 50-70 mm and covered with sand. Then the pile is placed on a vibrating table, where with the help of motors, the sand cushion is compacted, prevailing in all planes. Then it is covered with a film, sprinkled with sand and connected to a vacuum apparatus to give the molding sand the necessary strength, as well as to ensure the removal of gases (products of thermal destruction);

• casting of the model – molten metal (alloy) is poured directly into the mold. It dissolves polystyrene and takes its place, at the same time it repeats the configuration of the model block as accurately as possible;

• removal of the finished (cold) casting - the filled blocks of the models are kept in the sand mold from 5-10 minutes to 2-5 hours (the time depends on the technical specifications of the production, the weight of the product and the thickness of the metal). After complete cooling, they are taken out and the remains of the non-stick coating are removed.

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This method of casting allows you to significantly reduce the cost of materials, it is less toxic and minimizes the time spent on additional mechanical processing of the workpiece. It opens up great possibilities for the production of parts from various alloys and various configurations, starting from parts of crushers and ending with complex castings (art casting, diesel engines, car wheels, etc.).