Page 12 - Кулик В.В.

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Such steel provides high resistance to damage, but low resistance to wear of the

tread surface of the model wheel.

It is established that complex alloyed steels with a combination of solid-

solution and precipitation hardening possess the optimum strength and fatigue

crack growth resistance characteristics, wear resistance as well as damage

resistance. Complex alloyed steel with solid-solution (~ 1% Si and ~ 1% Mn) and

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precipitation ([V‧N]‧10 = 20…25%) hardening at reduced carbon content
(0.52… 0.53%) is recommended for pilot testing in order to manufacture railway

wheels of a new generation.

Increasing fatigue crack growth resistance of the heat affected zone of repair
tread surface of railway wheels is achieved by the formation in this zone a mixed

structure of upper and lower bainite (~ 66%) and martensite (~ 34%) and holding

time of 2-3 h, interrupting the cooling of steel at 100С, that is, at a temperature

between the points of onset (M ) and the end (M ) of the martensitic transformation.
s
f
This exposure contributes to the increase of the fatigue threshold of the specimen

with a crack by 1.6 times, the cyclic fracture toughness by 1.8 times along with

virtually unchanged strength. This is caused by a drop of ~ 1.5 times the residual

stresses of the II type in the volume of laths of bainite and martensite (patent of

Ukraine No. 105440). In this case, both the known and modified Q-n-P treatments

are less effective.

Recommendations for increasing fatigue crack growth resistance of the heat

affected zone of repair tread surface material are included in the technical

regulation of repair of railway wheels, developed by the E.O.Paton Electric

Welding Institute of the NAS of Ukraine.

On the basis of the research results, a departmental regulatory document

“Additional requirements for steels of solid-rolled high-strength railway wheels”

was formulated. The developed standards are the basis for the creation of

Specifications for high-strength railway wheels of a new generation.

Scientific novelty of the obtained results.

1. A new concept for creating high-strength wheel steels is proposed,