At present, the polymer quenching media has become more and more widely used due to its unique advantages in environmental protection, technology, and cost. However, unlike water and oil, the polymer quenching medium is rich in organic nutrients, it is easy to breed bacteria, thereby accelerating the aging of polymer quenching media, shorten the service life of quenching media. The cooling rate in the convection stage is increased, so that the quenching quality of the fastener is difficult to be stabilized, which may clog the filtration system of the mesh belt furnace and affect the normal operation of the system.
In fact, many companies have had to replace used quenching agents ahead of schedule due to bacterial growth. When bacteria grow, they release acidic substances that cause the pH to decrease. The decrease in pH is the result of bacterial growth. By constantly testing the pH of the quenching medium of the polymer, the trend or signs of bacterial growth can be revealed and corresponding measures taken to prevent the growth of bacteria.
A lower pH is one of the important reasons for bacterial growth; experimental results have shown that PH values below 8.0 will significantly promote bacterial growth.
When the PH value is lower than 8 ~ 8.5, it should be raised in time to prevent the growth of bacteria and rust-proof performance. The pH can be adjusted by adding a stock solution or using a supplier's pH adjuster. The use of inorganic salts or alkalis such as NaOH, Na2CO3, which can contaminate the polymer quenching agent, affects the accurate measurement of the concentration and affects the heat transfer in the quenching process. Therefore, it is not advisable to use inorganic bases or inorganic salts to increase the pH at the site. Oxidation and carbon black generated during the quenching process will continuously accumulate in the system. Not only will it clog the filter but also it will breed bacteria. Therefore, it should be regularly cleaned to keep the quench medium as clean as possible.
For this reason, the quality of bacteria and polymer quenching medium and liquid water for use, the circulation of the quenching system, pH, impurities, and bacteria in the air are related to these factors, and corresponding measures should be taken to reduce the bacteria. Breeding, while ensuring the cooling performance of polymer quenching media.
Carbon steel quenching when the hardness is not uniform why?
Carbon steel is quenched with water when quenched, and there is a white network or blocky texture in the metallographic examination structure. When the hardness test is performed, there is a soft hardness unevenness on one side of the hardness test. When the chemical composition of the steel is fixed, when the large-section bolts are quenched, the cooling rate changes rapidly from the surface to the core due to the effects of hardenability. The white mesh or lumpy texture that appears at this time is usually considered. It is the eutectoid ferrite, the morphology of which changes from a discontinuous semi-mesh network to a coarse mesh, because under normal circumstances, the quenching temperature does not have a large deviation, and the probability of undissolved ferrite in the quenched structure is small. The morphology of proeutectoid ferrite is related to the cooling rate.
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