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    Six common problems in the cleaning of fasteners

    Six common problems in the cleaning of fasteners

    文字:[大][中][小] 2018/6/25     浏览次数:506    

    In order to use fasteners better, we need regular maintenance when we use fasteners, such as regular cleaning of fasteners, so that the use efficiency of fasteners can be improved. But when we clean the fasteners, we often find some problems. There are mainly six common problems.


    1. Pollution caused by rinsing


    After the fastener is quenched, it is cleaned with a silicate cleaning agent and then rinsed with XX solid material on the surface, which is analyzed by infrared spectrometer, which is proved to be inorganic silicate and iron oxide. This is due to improper rinsing on the surface of the fastener.


    2. It is not reasonable for the fastener to be stacked


    When the fastener is tempered, there are signs of discoloration. It is soaked in ethyl ether to make ether volatile and the remaining oily residue is found. This substance is a high content of lipids. It indicates that the fastener is polluted by detergent and quenching oil during the rinsing period and melts at the heat treatment temperature. Analysis by infrared spectrometer is a mixture of base oil and ether in quenching oil. The ether may come from the additives of the quenched oil. The analysis of the quenching oil in the mesh belt furnace confirms that the fastener has a slight oxidation in the quenching oil when the fastener is not reasonable when the fastener is heated, but it is almost negligible. This phenomenon is related to the cleaning process, not the problem of the quenching oil.


    3, surface residue


    White residues on high strength screws were analyzed by infrared spectrometer and proved to be phosphide. The acid cleaning agent is not cleaned, and the bath liquid is found to have high carbon solubility. The bath liquid should be reversed regularly and the concentration level of the lye in the rinse tank is often detected.


    4, alkali


    High strength screw hardened black heat with uniform and smooth outer surface of oil black. But in the outer ring there is an orange XX visible area. In addition, there are visible areas of light blue or light red. The original rod and rod are coated with phosphating film for cold heading and tapping, without rinsing direct heat treatment, cooling in the quenching oil, cleaning the alkaline cleaning agent, blowing dry (not rinsing), tempering at 550 degrees C, extracting the rustproof oil from the tempering furnace, and finding the red spots at the screw thread.


    The red area on the test screw is caused by the alkali. The alkaline detergent containing the chloride and calcium compounds will cause the steel fastener to be damaged during heat treatment, leaving a stain on the surface of the fastener.


    Iron and steel fasteners can not remove surface alkalinity in quenching oil and aggravate damage in the next step of tempering. The suggestion is to clean and rinse the fasteners before heat treatment and remove the alkaline residues that cause damage to fasteners.


    5. Improper rinsing


    The large size fasteners are often used to quench polymer water solution, wash and rinse with alkaline detergent before quenching, and the fasteners after quenching have been rusty inside. It is proved by infrared spectrograph that besides iron oxide, there are sodium, potassium and sulfur, which indicates that the inside of the fastener is sticky with alkaline cleaning agent. It is probably potassium hydroxide, sodium carbonate or similar substances to promote its rust. It is also recommended to check the rinsing water frequently if there is excessive contamination on the fasteners rinsing. In addition, adding rust inhibitor to water is also a good way.


    6. Excessive corrosion


    High strength fasteners often see some black stripes. In the test, the fasteners were rinsed with inorganic and organic cleaning agents before heat treatment. After quenching, there were still black stripes and even fine cleaning before heat treatment, and stripes were left after heat treatment. Infrared spectroscopy was used to analyze the residual contaminants on the surface and found a higher concentration of sulfur and calcium. With a small amount of acetic acid, isopropyl alcohol, a small piece of test paper is forced to wipe at the black spot, leaving the spots on the filter paper. Using infrared spectrometer to analyze filter paper, it is proved that calcium, sulfur, iron, manganese and chromium are the main elements.


    Calcium and sulfur in the rust spot indicate that this substance is a quenched oil that is dried and also evolved during the quenching process. Because of the over aging of the quenching oil, it is recommended to pour out the old oil and add new oil, and supervise the process and maintain the quenching oil in the whole process cycle.



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