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ENSURING MECHANICAL PROPERTIES OF THE ROTATIONAL PARTS WORKING

IN THE CONDITIONS OF IMPACT LOADINGS

Pavlov E.V.

, Ph.D. (Engineering), Associate Professor, e-mail:

Southwest State University, 94, 50 let Oktyabrya str., Kursk, 305040, Russian Federation

Abstract

The rotational parts perceiving impact sign-variable loading have to possess the high level of

hardness and a limit of fluidity. Substantially mechanical properties are influenced by structure and

the maintenance of the alloying elements of materials of rotational parts.

The used steel brands contain rather large number of the nonmetallic inclusions which are

concentrators of tension and considerably reducing resistance to fatigue failure. Besides,

fundamental value renders a choice of a method of heat treatment. Operability of basic parts and a

resource of boring machines substantially depend on thermal hardening of the material of parts

providing the best combination of the demanded indicators of durability, hardness, impact strength.

For providing the maximum indicators of impact strength became with the hardness of 38 … 42

HRC most rational heat treatment is isothermal training. In the steel strengthened on technology of

isothermal quenching, cracks grow twice more slowly, than in the steel strengthened by quenching

and tempering. It should be noted that formation in the parts working in the conditions of impact

and cyclic loading, structures with a low durability is irrational. Despite high rates of impact

strength, steel in a low-strength state (less than 30 HRC) possesses low resistance to fatigue failure.

Keywords

Rotational parts, mechanical properties, heat treatment, isothermal quenching, impact strength,

fatigue failure