THERMAL TREATMENT OF FRICTION DISCS

Heat treatment of friction discs. Friction discs with a round and spline profile of a hole with a diameter of 250 to 450 mm and a thickness of 4 to 8 mm were made of steel 20 with cementation and subsequent quenching into water with special heating on the floor of an electric furnace.

The discs were cooled in special jigs.

Hardness after heat treatment HRC 48-54.

Uneven deformation of the disks leads to the fact that the installed allowances for grinding planes (up to 2.0 mm per side) are not preserved, as a result of which the residual stresses are unevenly distributed, an uneven working surface is obtained and a considerable variation in the durability of products is observed.

To prepare for the cementation of the plane of the disk, made of sheet steel, pre-polished to remove the oxide film, which contributes to the deformation during the quenching process.

The authors have developed and mastered the manufacture and heat treatment of friction discs with minimal deformation along the plane (maximum deflection 0.3 mm instead of 2 mm according to the old technology), from 65G sheet steel.

The sheet thickness is selected taking into account the allowance for final grinding (not higher than 0.3 mm per side).

Before the heat treatment, the planes of the disks are not subjected to mechanical treatment, since the preliminary machining of the planes contributes to the deformation after the heat treatment.

Pre-grinding increases the leash after quenching in comparison with the preliminary rough machining (turning, milling). Uneven machining of the planes gives the same results.

Currently, heat treatment of friction discs is carried out according to the following technology:

1. In a chamber electric furnace with a three-sided (side walls and under) heating load massive round pan, 50 mm thick, with an outer diameter and a hole diameter corresponding to the dimensions of the hardened disk. The flat surface of the pallet must be grooved.

2. After warming up to the set temperature, a disk is placed on the pallet.

3. The disk is heated in a furnace to 820-930 ° C. Heating and shutter speed depend on the size of the disc.

4. After heating, the disk is sharply turned with pliers with needle protrusions from the working part to the vertical position, quickly lowered into the quenching oil tank and cooled without shaking the disk in oil.

5. Vacation at 240-250 ° С.

6. Disks for straightness check on the marking plate.

7. Hardness is controlled on a Rockwell instrument.

Ya.A. ARENKO, B.A. Ryasnyansky
ISSN 0026-0819. “Metallurgy and heat treatment of metals”, № 10. 1968
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