DEVELOPMENTS OF THE INSTITUTE :: FREEZING-UP TECHNOLOGY OF CONTINUOUS- ITERATIVE CASTING

This technology is applicable for production of hollow cylindrical castings with a specified length from special wear-resistant cast irons (СЧ - grey cast iron with lamellar graphite; ВЧШГ - high-strength cast iron with globular graphite; БВХЧ - white high-chromium cast iron with trigonal-type carbides) and also bronzes. It makes it possible to produce castings with preset structure and physical&mechanical properties in a continuous-iterative mode at the expense of directional solidification and heat treatment combined in a united production process. The casting process includes filling a steel water-cooled crystallizer with molten metal from a drag (bottom) of the crystallizer, soaking a casting to form it and its extraction from the crystallizer up with simultaneous introduction of a new portion of melt. The metal is fed into the crystallizer with the aid of a disposable metal feeder lined with the fire-resistant material. The process is executed in a continuous-iterative mode, whose rate is determined by the solidification rate of the casting with required width in the crystallizer.
The semiautomatic casting plant allows casting of up to 2500 kg of metal to be made under continuous conditions without readjustments.

1pouring cup ; 2сonnecting element; 3stationary crystallizer; 4movable crystallizer

Advantages:

The main distinctive feature of this technology is manufacturing hollow castings without using a core in the stationary (not rotated) water-cooled metal mold. Singularities of the casting formation mechanism ensure heightened density, specified structure and hardness, lack of blow-holes, slag inclusions, shrinkage porosity and cracks. The structural component distribution in the castings is not reproduced by any known productive methods for castings of that kind. The metal matrix structure required (in a range from pearlitic to ferritic one for gray cast irons) is obtained without additional heat treatment. . A complex solution of a problem of utilization of own reflexive waste (chips, technological crop ends and gates) whose fraction in a charge can reach 70 Е 80 % without lowering the quality of casting is also provided.

Possible application fields:

• cylinder sleeves for air compressors and internal combustion engines (sleeves from grey cast iron for an augmented drive of a Д 260 tractor " Belarus" withstand the hydraulic pressure of up to 40 Е 43 MPа without fracture)
• BХ— punch bushings for presses for manufacturing perforated lime-and-sand bricks (their operation life is 5 Е 6 times as large as that of commercially available bushings obtained by chill casting and 15 Е 18 times as large as that of cemented or borated steel bushings)
• a wide range of the piston and sealing rings from special alloy CЧ— and ВЧШГ cast irons. The rings have high elasticity and wear resistance. The sealing rings from ВЧШГ cast iron have the same thribologic parameters as the commercially available chrome-plated rings have. The hardness of rings from СЧ— cast iron is 98 Е 102 HRB, and that of rings from ВЧШГ cast iron is 102 Е 106 HRB. The difference of hardness magnitudes over a single ring does not exceed 2 HRB.