INDUCTION HARDENING OF BEARING PARTS

It is known that induction heating is effective in flow-line mass production that precludes
resetting of equipment, or in individual production where the application of ordinary
heating methods is difficult.
Induction hardening of rolling elements, of cold-pressed rings with 60-80-mm diameter,
and of races of large bearings with up to 2-m diameter therefore found widespread application
at the plant GPZ I.
Hardening of Rolling Elements of Steel ShKhl5. Hardening after induction heating is
applied to balls with 12-50-mm diameter and conical rollers with 15-22-mm diameter, made of
steel ShKhl5.
The rolling elements are heated prior to quenching in an induction installation whose
power is supplied by a frequency converter VPCh-100/8000.
The installation consists of a loading mechanism, a vertical or horizontal inductor, a
slit sprayer, rotating roller, lifting devices for feeding components to the inductor, and a
tempering furnace.
The balls are loaded into a hopper from which they are lifted by a vertical elevator,
and then they are fed into a vertical multiturn inductor 1 m long. In installations intended
for the hardening of conical rollers the inductor is arranged horizontally.
A denser arrangement of the coils in the first half of the inductor ensures accelerated
heating with gradually decreasing heating rate in the second half of the inductor. The components,
heated to 920-940°C, are fed onto horizontal rotating rollers where during their
motion they are cooled by water from the slit sprayer (water temperature 15-25°C, flow rate
13-15 m3/h). The temperature prior to quenching is set by the specified voltage of the inductor
(260-350 V), and it is additionally checked with an optical pyrometer.
The heating and cooling times of balls and rollers are presented in Table I.
It is envisaged that after the components have been fed to the inductor, heating will be
automatically switched off, with subsequent scrapping of components when the installation
is switched on.
From the hardening installations the components travel to the drum-type screw furnace
for tempering. The tempering temperature is 150-165°C, tempering time 2-2.5 h, cooling after
tempering in air, the capacity of the installation is 180-250 kg/h. Hardness of the balls
after hardening and tempering is HRC e 63-67, of rollers HRC e 62-66. The microstructure is
cryptocrystalline or finely crystalline martensite.

induction hardening bearing