Cylinder liners, bushings for different purposes, piston and O-rings are made from hollow cylindrical work pieces of fixed lengths, obtained by means of continuous cyclic freeze casting technology of special wear-resistant cast iron - grey cast iron with flake and flake-vermiculite graphite, high-strength cast iron with spheroidal graphite, high chromium white cast iron with trigonal carbides).
The main feature of this technique is the possibility of forming hollow castings in a water-cooled metal mold without the use of a rod, which results in increased density, predetermined structure and hardness, absence of blowholes, slag inclusions, shrinkage porosity and cracks. The distribution of structural components in the casting cannot be made by any of the known technique used for producing similar castings.
The continuous cyclic freeze casting method allows us to get castings with the required structure of metal matrix in the range of pearlite to ferrite matrix without additional heat treatment. Strength and wear-resistant properties of the parts produced from such castings significantly surpass analogues obtained by centrifugal casting and casting in sand-clay molds.
In particular, punch bushings from white high chromium cast iron with trigonal carbides for hollow lime brick presses have a service life 5-6 times higher than mass-produced ones received by gravity die casting of cast iron of the same chemical composition, and 15-18 times higher than carburized or borated steel ones.
According to the information of PO “Minsk Motor Works” liners of high-powered engines D245 and D260, manufactured from work pieces obtained by freeze casting of grey cast iron, can resist hydraulic pressure up to 40-43 MPa, whereas the best mass-produced bushings, made from work pieces cast in sand-clay molds or by centrifugal casting, are destroyed at the pressure of 28-32 MPa.
Liners made from work pieces produced by continuous casting, also differ in the predetermined distribution of structural components across wall thickness that, in addition to high strength properties, results in increased wear and cavitation resistance.
We produce a wide range of piston rings and O-rings from special alloy grey cast iron, cast iron with flake-vermiculite graphite, high-strength cast iron with spheroidal graphite. The rings have high elasticity and wear resistant properties. O-rings from high-strength cast iron with spheroidal graphite are not inferior to mass-produced chrome ones in respect of their tribological properties.
The hardness of the rings from grey cast iron is 98-102 HRB, and from high-strength cast iron with spheroidal graphite - 102-110 HRB. The difference in hardness within one ring does not exceed 3 HRB units. The metal base of cast iron consists of superfine pearlite with a small amount of ferrite in the form of isolated fine inclusions.
This feature of the structure gives rings from grey cast iron some plasticity reserve, which significantly reduces the probability of breakage when installing on the piston and makes them competitive with the rings previously made from high-strength cast iron with spheroidal graphite.
For example, according to the information of PO “Minsk Motor Works” the installation of the O-rings produced by “TEHNOLIT” on the hydraulic drive couplings of the front drive axle of “Belarus-1025 -1221 – 1522” tractors instead of previously used ones allowed reducing oil leaks through the friction clutch from 2 - 2.5 l/min to 0.4-0.7, preventing interplant defects and completely avoiding complaints regarding FDA drive coupling.
The rings were provided with specifications registered by Gosstandart of the Republic of Belarus (TU RB 100316761.456-2000). We produce similar O-rings for transmissions for tractors K700, T150, “Amkador”, BelAZ, MZKT, etc.
The company “TEHNOLIT” has no complaints regarding the quality of material used for the manufacture of products.