Manufacture Technology

we presented the technology of layered castings based on the founding method of layer coating directly in
the casting process is known as the method of mold cavity preparation by monolithic or granular material of insert. Prepared castings consist of two fundamental parts: the base part and the working part (layer). The base part of a layered casting is usually typical foundry material (i.e., pearlitic grey cast iron with flake graphite or ferritic-pearlitic carbon cast steel), whereas the dependence of an insert type (i.e., monolithic or granular) working part (layer) is suitably plated with ferritic and austenitic alloy steels or a layer from a Cr-base alloy. The ratio of thickness between the base and working part is between 8:1 and 10:1.

The quality of the layered castings was evaluated on the basis of ultrasonic non-destructive testing, structure, and selected usable property research. According to work out technology, the prepared layered castings can work in conditions that require high heat resistance and/or corrosion resistance from the working surface layer of an element in a medium of industrial water, for example. Moreover, in the case of applying an insert based on Cr-base alloy powder on the working surface layer, it is possible to obtain high hardness and abrasive wear resistance.

The technology of layered castings is gaining in importance, particularly when the criterion for highly usable properties concerns only the working surface layer, and the rest of the casting is only the base part that is not exposed to the direct influence of factors causing abrasive or corrosion wear. This technology is the most economical way of enriching the surface of castings, as it allows for the production of layered elements directly in the casting process.

Therefore, this technology can be significantly competitive for the commonly used technologies of surfacing by welding and thermal spraying because, in addition to its economic advantages, it does not generate opportunities for the development of cracks in the heat-affected zone that may arise as a result of making the layer by using the welding method. In general, the technology of cast bimetals containing a working layer and a base part is carried out based on two systems; i.e., liquid-liquid and liquid-solid. An example of the former is a technology in which two independent gating systems are made, which guarantees a two-stage filling of the sand mold cavity.

According to this manufacturing method, the bimetallic elements of hammer or ball mills are cast in material configurations of resistant-to-abrasive-wear chromium cast iron working layer with a ductile low-carbon cast steel base. The basic technology of layered castings made in a liquid-solid system is the so-called method of mold cavity preparation. In this manufacturing method, the element enriching the surface of the casting is placed in the mold in the form of a granular or monolithic insert directly before the molten metal is poured. Therefore, this paper presents possibilities of using a Cr-base alloy as a granular insert and high-chromium and chromium-nickel alloy steels as monolithic inserts. In the case of the granular insert, the mold was poured by carbon cast steel, and in the case of the monolithic insert, the mold was poured by grey cast iron.