Theoretical and Practical Aspects of the Formation of the Variational Structure of Centrifuged Products from Heavy Concrete

Viability of further research of variatropy is justified, as well as its extended use with the purpose of increasing quality of ferroconcrete building constructions. Raw components and equipment used for manufacturing of centrifuged products and variatropic objects are described. Laboratory centrifuge equipped with a direct current engine and thyristor units has been developed and used. Method of applying pressure to a unit mass during centrifuging has been studied. It has been identified that in order for mix particles rising to their most superior position to stick to the mold walls, it is necessary that gravitational force of mg particle and centrifugal force are equal. Effect of hydrodynamic pressure on particles constituting concrete mix has been studied using several formulas and provisions. It has been revealed that centrifugal molding may be used to seal low-viscosity plastic mixes; however, its use causes disintegration of concrete mix. In order to slow down this process, it is necessary to increase viscosity of the entire system and restrict the upper limit of aggregate fineness.

Bronze Sealing Rings Defects and Ways of its Elimination

In the article data about application nanopowder on a structure of coatings of the form are submitted at a casting of lead-tin bronzes. Elimination of gas porosity on a surface bronze cast preparations of high pressure compressors piston rings was the primary goal of such application protectively-dividing coverings. For experimental works mark of multicomponent bronze has been chosen. Its structure includes tin, lead, zinc and nickel. Casting from this bronze received a method of centrifugal molding. Influence of a structure of used protective - separating coating of a foundry core on a surface smoothness was probeed. Was compared action of coatings of a following composition: anti-burning-in coating (a blend of a low dispersible powder of chromium oxide with calcinated vegetable oil); anti-burning-in material ASPF-2/RgU (on the basis a low dispersible powder of graphite and the calcinated vegetable oil); the patent № 2297300 (blend of a ultradispersible powder of dioxide of zirconium with inpowderrial oil. Molding without use of coverings leads porosity depth to 4-5 mm and to a marriage significant amount (to 50 %). Use ASPF-2/RgU completely eliminates welding casting to a casting mold, but porosity on a surface remains. Application of coverings of a casting mold containing in quality of a filler ultradisperse powders oxide metals with low heat conductivity allows in to lower much a roughness and to eliminate gas porosity on a cast surface from lead-tin bronze. A gas time of a surface still remains, but them becomes much less and their form changes. Depth of defects doesn't exceed 1-1,5 mm that doesn't fall outside the limits the admission.