High temperature cooling and thermal fatigue test of brake drum

A, sample preparation

A square ingot with a wall thickness of 1.5cm by 1.5cm was cut from the flange bottom of the failed brake drum which was not affected by the high temperature phase transition, and was ground away by the layer affected by the residual stress of the line cutting surface (note that no new residual stress was generated during grinding). Finally, all surface roughness of the ingot was treated to ≤3.2 m.

Ii. Test operation

The specimen was heated to 880℃ for one minute, then taken out and quickly put into 20℃ water for cooling. Such cyclic operation was performed until the crack was observed by the naked eye, and then blow-dried for metallographic observation.

Iii. Test results

After tests, cracks visible to the naked eye appeared in the 30 test blocks during the high temperature and chilling for 31, 14, 35, 28, 41, 29, 36, 28, 30, 26, 28, 32, 33, 37, 29, 34, 27, 33, 28, 28, 30, 33, 36, 27, 30, 32, 40, 29 and 30 times successively. The crack morphology is consistent with the failure position of brake drum.

Four, conclusion

Thermal fatigue fracture caused by high temperature chilling is indeed one of the main causes of brake drum cracking and cracking.