High-strength fastener cleaning problems often occur after heat treatment and tempering. The main problem is that the rinsing is not clean. The lye is left on the surface due to unreasonable stacking of the fasteners, and surface rust and alkali burn or quenching oil are improperly selected to rust the surface of the fastener.

1. Pollution generated during rinsing

After the fasteners were quenched, they were washed with a silicate cleaning agent, then rinsed, and XX solid matter appeared on the surface, and the material was analyzed by an infrared spectrometer to confirm inorganic silicate and iron oxide. This is caused by the fact that the rinsing does not completely leave silicate on the surface of the fastener.

2. Unreasonable stacking of fasteners

After the fasteners are tempered, there are signs of discoloration, soaked in ether, and the ether is evaporated to find the remaining oily residue. These substances are high-content lipids. It is indicated that the fastener is contaminated by the cleaning agent and the quenching oil during the rinsing period, and melts at the heat treatment temperature, leaving a chemical burn scar, which proves that the surface of the fastener is not clean. Analysis by infrared spectrometer is a mixture of base oil and ether in the quenching oil. Ether may be derived from the addition of quenching oil. The quenching oil analysis results in the mesh belt furnace confirmed that the fasteners were unreasonably stacked due to the improper heating, and the fasteners were slightly oxidized in the quenching oil, but they were almost negligible. This phenomenon is related to the cleaning process, not the quenching oil. The problem.

3, surface residue

A white residue on the high-strength screw was analyzed by an infrared spectrometer and confirmed to be a phosphide. No acid cleaning agent was cleaned, and the bath solution was found to have a high carbon solubility. The bath should be drained periodically, and the concentration of the lye in the rinsing tank was often checked.

4, alkali burns

The high-strength screw quenching residual heat black has a uniform, flat oil black outer surface. However, there is an area visible to the naked eye in the outer ring. In addition, there is a slightly light blue or light red area visible. The original bar and wire rod are coated with a phosphate film to facilitate cold heading and tapping. Direct heat treatment without rinsing, cooling in quenching oil, alkaline cleaning agent cleaning, drying (no rinsing), tempering at 550 °C, heat The state was removed from the tempering furnace and the rust-preventing oil was removed. As a result, red spots were found at the screw threads.

The red area on the tested screw is caused by alkali burn. The alkaline cleaning agent containing chloride substance and calcium-containing compound will burn the steel fastener during heat treatment and leave marks on the surface of the fastener.
Steel fasteners do not remove surface alkalines in quenching oil, causing surface burns in high temperature austenite and aggravating damage in the next tempering. The suggestion is in the heat

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