1. Pollution during rinsing: After the fasteners are quenched, they are cleaned with a silicate cleaning agent, and then rinsed. XX solid substances appear on the surface. This substance is analyzed by an infrared spectrometer and confirmed to be inorganic silicate and iron oxide. This is due to the residual silicate on the surface of the fastener due to incomplete rinsing.
2. Unreasonable stacking of fasteners: There are signs of discoloration after the fasteners are tempered, and oily residues are found after volatilization. Such substances are high-content lipids. It shows that the fasteners are contaminated by cleaning agents and quenching oils during the rinsing period, and melted at the heat treatment temperature, leaving chemical burn scars. Such substances prove that the surface of the fasteners is not clean. Analyzed by infrared spectrometer, it is a mixture of base oil and ether in quenching oil. Ether may come from quench oil additives. The analysis results of the quenching oil in the mesh belt furnace confirmed that the fasteners were slightly oxidized in the quenching oil due to unreasonable stacking when they were heated, but it was almost negligible. This phenomenon was related to the cleaning process, not the quenching oil The problem.
3. Surface residues: There are white residues on high-strength screws, which are confirmed to be phosphides through infrared spectrometer analysis. No acid cleaning agent was used to clean the rinsing tank, and it was found that the rinsing tank had a high carbon solubility. The tank should be poured out regularly, and the concentration of lye in the rinsing tank should be checked frequently.
4. Alkali burn: high-strength screws are blackened by quenching residual heat, and have a uniform and smooth oil-black outer surface. But there is an orange XX visible area on the outer ring. In addition, there are slightly bluish or reddish areas visible. The original bar and wire rod are coated with phosphating film to facilitate cold heading and tapping, directly heat treated without rinsing, cooled in quenching oil, cleaned with alkaline cleaning agent, blown dry (without rinsing), tempered at 550°C, heated The anti-rust oil was removed from the tempering furnace, and red spots were found on the screw threads.
5. Improper rinsing: For large-scale fasteners, polymer aqueous solution is often used for quenching. Before quenching, it is cleaned and rinsed with alkaline cleaning agent. After quenching, the fasteners have rusted on the inside. Analysis with an infrared spectrometer has confirmed that in addition to iron oxide, there are sodium, potassium and sulfur, indicating that there is an alkaline cleaning agent on the inside of the fastener, which is likely to be potassium hydroxide, sodium carbonate or similar substances, which promote its rusting. Fastener rinses are checked for excessive contamination and frequent rinse water changes are also recommended. In addition, it is also a good way to add anti-rust agent to the water.
6. Excessive rust: Some black stripes are often seen on high-strength fasteners. It is also seen in the test. The fasteners before heat treatment have been rinsed with inorganic and organic cleaning agents. After quenching, there are still black stripes even before heat treatment. If you wash it carefully, it will also leave streaks after heat treatment. Using an infrared spectrometer to analyze the residual pollutants on the surface, it was found that there were higher concentrations of sulfur and calcium. Using a small amount of acetic acid in isopropanol, wipe a small piece of test filter paper vigorously at the black spot, leaving the black spot on the filter paper. The filter paper was analyzed with an infrared spectrometer, and it was confirmed that calcium, sulfur, iron, manganese and chromium were the main elements.
