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How to clean high strength fasteners?

Release By: Dongyi Hardware    Time:12/20/2019 5:14:38 PM

1. The pollutants produced during washing are quenched and cleaned with silicate cleaning agent, and then washed and appear on the surface of XX solid material. The material was analyzed by infrared spectrometer, which was identified as inorganic silicate and iron oxide. This is due to incomplete rinsing on the surface of fastener residues due to silicate.

2. After the fasteners were stacked unreasonably, the fasteners showed signs of discoloration. They were soaked in ether to volatilize the ether, and the remaining oily residue was found. The content of this kind of material was high. It shows that the fastener is contaminated by cleaning agent and quenching oil during flushing, and melts at heat treatment temperature, leaving chemical burn scar, which proves that the fastener surface is not clean. It is the mixture of base oil and ether in quenching oil by infrared spectrometer. The ether may come from the addition of quenching oil. The analysis results of quenching oil in mesh belt furnace show that due to unreasonable stacking of fasteners, fasteners are slightly oxidized in quenching oil, but almost negligible. This phenomenon is related to the cleaning process, not to the problem of quenching oil.

3. The white residue on the surface of high strength screw was analyzed by infrared spectrometer, and the phosphide was confirmed. There is no acid cleaning agent for cleaning, and the bath has a high carbon solubility. The bath should be drained regularly and the concentration of alkali liquor should be detected frequently.

4. Alkaline combustion high strength screw quenching waste heat is uniform, smooth oil black surface. But there is an orange XX visible area in the outer ring. There are also visible light blue or light red areas. The raw material bar and wire rod are coated with phosphating film, which is convenient for cold heading and tapping. It is directly heat treated without flushing. It is cooled in quenching oil, cleaned with alkaline cleaning agent, dried (not washed), tempered at 550 ℃, and then retreated to the furnace to remove the oil immersion. It was found that there were red spots on the thread. The red area on the test screw is caused by alkali burn. Alkaline cleaners contain chlorinated substances. Calcium containing compounds burn steel fasteners during heat treatment and leave traces on the surface of fasteners. Steel fasteners can not remove the surface of alkaline objects in quenching oil, which will burn the surface in high temperature austenite state and improve the damage by tempering in the next step. It is recommended that fasteners be thoroughly cleaned and flushed prior to heat treatment to thoroughly remove alkaline residues that cause combustion of the burner.

5. The improper large-size fasteners are usually used for polymer water quenching, and the quenching is cleaned and washed with alkaline cleaning agent. After quenching, the internal parts of the fasteners rust. The analysis of infrared spectrometer confirmed that in addition to iron oxide, there were sodium, potassium and sulfur, indicating that there were alkaline cleaning agents inside the fasteners, which were probably potassium hydroxide, sodium carbonate or similar substances to promote rust. Check fastener flushing for excessive contamination. It is also advisable to change the flushing water frequently. In addition, adding antirust agent is also a good method.

6. Some black stripes are often seen on high strength fasteners with excessive corrosion. It is also found that in the test, inorganic and organic cleaning agents have been used to wash the heat before the fasteners, and they are still found to be black stripes after quenching. Even after careful cleaning by Aberdeen before heat treatment, they will be left behind after heat treatment. Infrared spectrum analysis showed that the surface residual pollutants showed higher sulfur and calcium concentrations. Use a small amount of isopropyl acetate, the folding force of a small piece of test paper in the black spot, and the black spots on the filter paper. It is confirmed that calcium, sulfur, iron, manganese and chromium are the main elements in the filter paper. There are calcium and sulfur in the rust, and this material is dried and quenched with oil, and during the evolution of the quenching gas phase. Due to the excessive aging of quenching oil, it is recommended to pour out the old oil and add new oil in the whole process cycle for process supervision and maintenance of quenching oil.


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