The use of fasteners must pay attention to details, performance is very important, regular maintenance is the focus, to ensure that the machinery runs normally. In order to prevent some problems with fasteners, we must pay attention to the following points when performing routine maintenance of fasteners.
I. Pollution during rinsing
After quenching, the fasteners need to be cleaned with silicate cleaner and then rinsed, so be very careful when rinsing to prevent residues.
Second, the stacking of fasteners is unreasonable
After tempering, the fastener will show signs of discoloration, and there may be oily residue after soaking in ether, indicating that the surface of the fastener is not clean. After analysis, it was indicated that the fasteners were stacked unreasonably when heated, resulting in slight oxidation of the fasteners in the quenching oil.
Second, the surface residue
White residues on the high-strength screws were analyzed with an instrument and confirmed to be phosphides. This reaction occurred because the acid washer was not cleaned and the rinsing tank was not thoroughly checked.
Fourth, alkali burns
High-strength screw quenching waste heat blackening has a uniform, flat oil black outer surface. Tested to be caused by alkali burns. Therefore, in the steel quenching oil, the surface alkali cannot be removed in the quenching oil, so that the surface is burned at high temperature, and the injury is aggravated during tempering. It is recommended that the fasteners be thoroughly washed and rinsed before heat treatment to completely remove alkaline residues that cause burns to the fasteners.
5. Improper rinsing
For large-size fasteners, polymer aqueous solutions are often used for quenching. Before quenching, they are washed and rinsed with an alkaline cleaner. After quenching, the fasteners have rusted on the inside. Therefore, the rinsing water should be exchanged frequently to ensure that the fastener will not rust during rinsing.
Six, excessive corrosion
High-strength fasteners often see some black streaks. This black streak is a contaminant on the surface residue. It is a dried quenching oil. It is the evolution of gaseous substances during the quenching process. Because the quenching oil is too old, it is recommended to add new oil.