Six points to pay attention to when maintaining fasteners

As an important part of machinery, fasteners must be maintained regularly, so that the fasteners can play a better performance role and the machinery can operate normally. In order to prevent some problems with fasteners, the following points must be paid attention to during the daily maintenance of fasteners.

1. Pollution during rinsing

Fasteners need to be cleaned with silicate cleaning agent after quenching, and then rinsed, so be very careful when rinsing to prevent residues.

2. Unreasonable stacking of fasteners

The fasteners will show signs of discoloration after tempering. There may be oily residues after soaking in ether, indicating that the surface of the fasteners is not clean. After analysis, it is indicated that the fasteners are stacked unreasonably when heated, which leads to slight oxidation of the fasteners in the quenching oil.

3. Surface residues

There is a white residue on the high-strength screw, which was confirmed to be phosphide after analysis with an instrument. This reaction occurred because the acid washer was not cleaned and the rinse tank was not thoroughly inspected. (Guide: Knowledge of Fasteners: Requirements for Hot Dip Galvanizing of Nuts)

Fourth, alkali burns

High-strength screws are blackened by quenching heat and have a uniform and smooth oil-black outer surface. After testing, it was caused by alkali burns. Therefore, in steel fasteners, the surface alkalis cannot be removed in the quenching oil, so that the surface burns at high temperatures and aggravates the damage during tempering. It is recommended to thoroughly clean and rinse fasteners before heat treatment to completely remove the alkaline residues that cause fasteners to burn.

Five, improper rinsing

For large-size fasteners, polymer aqueous solution is often used for quenching. Before quenching, they are cleaned and rinsed with an alkaline cleaner. After quenching, the fasteners have rusted on the inside. Therefore, the rinsing water should be changed frequently to ensure that the fasteners will not rust during rinsing.

Six, excessive rust

High-strength fasteners often see some black streaks. The black streaks are the contaminants of the surface residues. The quenching oil is the evolution of the gas phase during the quenching process. Because the quenching oil is excessively aged, it is recommended to add new oil.

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