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Development of Quenchants/quenchants

water based quenchants

water is the most economical quenchant. It has high chemical stability and large heat capacity. However, the cooling capacity of pure water in high temperature area is not strong, but it is very large near 300 ℃. Therefore, the cooling characteristics of pure water are exactly opposite to the characteristics of the ideal quenching medium we require, which is the reason why pure water is rarely used. The commonly used water-based quenchants include salt water, alkaline water, saturated chlorination, and several 10 agent companies have been set up in China, such as calcium, trinitrate aqueous solutions (NaNO3, NaNO2, KNO3), organic polymer aqueous solutions, etc

in the late 1950s, the United States proposed 1. The main motor source of the experimental machine is not bright, non-toxic, odorless, non combustible, and the cooling performance is between water and oil, adjustable polyvinyl alcohol (PVA), water solution quenching medium, and later developed into organic polymer water-based quenching solutions such as polyalkylene glycol (PAG), polyoxyethylene glycol (Gly), and polyvinylpyrrolidone (PVP). In the late 1970s, a non martensitic quenchant alkaline polyacrylate (ACR) suitable for bainite quenching was developed, which has high viscosity and is suitable for isothermal quenching, hot forging quenching of forgings, quenching of high-speed steel and martensitic stainless steel. In addition, there are new quenchants such as polyacrylamide (PAM), methylcellulose (CMC) and high molecular weight polysoap aqueous solution

polyether prepared by ring opening polymerization of ethylene oxide and propylene oxide has inverse solubility, which makes it play an excellent lubricating role in water-based metal working fluids (such as cutting fluid, grinding fluid, quenching fluid). When the polyether solution is brought into the cutting area and meets the hot metal surface, the liquid temperature quickly rises to higher than the cloud point of the polyether. At this time, polyether precipitates from water to form tiny droplets like oil, which form a thin lubricating oil film on the metal surface and play a role of fluid lubrication. The test shows that when the temperature is higher than the cloud point, the concentrated solution of 5% polyether solution has the same lubrication performance. At room temperature, polyether is easily soluble in water, and its aqueous solution has the excellent properties required by many quenchants, so it is widely used in quenchants. The monomer used to prepare "traditional polyether" must include ethylene oxide, and its mass fraction in the whole molecule is preferably 70% - 90%, accounting for at least 10%. It is also possible to use only ethylene oxide as a monomer. Other monomers are lower epoxides containing c3~4, such as propylene oxide, tetrahydrofuran and two isomers of sulfoxybutane. The relative molecular weight of "traditional polyether" is mostly about 20000, belonging to the category of medium and high relative molecular weight. Its preparation mostly adopts the "step-by-step synthesis method", that is, polyether with relative molecular weight of hundreds to thousands is synthesized with propylene oxide and ethylene oxide according to the general method, and then polyether with higher relative molecular weight is prepared by continuous polymerization with monomer with this polymer as initiator. Repeat the above steps several times to get the product with the required relative molecular weight. The heteropoly copolymer and mosaic copolymer of ethylene oxide and another monomer can be called "traditional polyether". Alcohols and amines are commonly used to prepare the initiator of "traditional polyether". A large number of patents on the synthesis and application of polyether for water-based quenchant have been reported abroad, and have entered the stage of industrial production and application. China's research in this area started late, and many products still need to be imported. In recent years, time modified polyether has been widely studied

PAG quenchant is a kind of water-based quenchant widely used in industry. It is made of specific polyether non-ionic polymer (PAG) plus composite additives and vector water that can obtain other auxiliary properties. PAG is an ideal quenchant especially for medium and low hardenability steels seeking cooling rate between water and oil. Purpose of using PAG quenchant 3. Accurate measurement range of force value: 2% - 100% of the maximum experimental force is to adjust the cooling characteristics of water. In the quenching process, PAG film is formed rapidly, and the cooling capacity can change with the adjustment of concentration. The quenching hardness is uniform. After quenching, it can be tempered directly without cleaning. The cooling characteristics of Quenchant depend on the characteristics and quantity of PAG components. Other additives that provide auxiliary properties have little effect on the cooling performance of quenchant. However, in quenching production, the amount of PAG polymer will be reduced due to workpiece removal and high-temperature oxidation and decomposition. During quenching, the liquid temperature around the workpiece rises, and PAG polymer desolvates from the solution and adheres to the workpiece surface in the form of water rich coating by its wettability, so as to adjust the cooling rate of the workpiece. After the workpiece cools down, the polymer adhered to the surface of the workpiece will dissolve into the quenching solution. It takes a certain time to re dissolve, and in production, the workpiece is often removed from the quenching solution after the polymer is re dissolved. Because the content of PAG in the liquid brought out by the workpiece is often higher than the average concentration of PAG in all quenchants. After long-term and large-scale quenching, the relative concentration of PAG in the quenching solution must gradually decrease. In addition, PAG has high chemical stability and does not react with general acids and bases at room temperature. It is oxidized and decomposed only at a high temperature of 250 ℃ and in the presence of oxygen. During quenching, most of the PAG polymer film adhered to the surface of the workpiece can be kept at a temperature not higher than the boiling point of water because the water and fertilizer in and around it are vaporized. However, the next part of the workpiece surface may still rise to a higher temperature and undergo oxidative decomposition, resulting in the reduction of PAG content. In this way, the relative content of other additive components in the quenching solution will increase, which will eventually affect the quenching efficiency

pag quenchant has significant advantages for aluminum alloy quenching. The quenching efficiency of aluminum plate is 60% lower than that of hot water quenching. However, the cooling rate of PAG quenchant in the martensitic transformation zone of most steel parts is faster than that of oil, so it has certain limitations on the quenching and tempering of high alloy steel

pvp and ACR quenchants are developed to make up for the above shortcomings of PAG, but these two polymers have no inverse solubility. The polymer adhered to the surface of the workpiece after quenching needs to be cleaned. In addition, its processibility and stability are not as good as PAG, so its application is limited. Peo (polyvinyloxazoline) quenchant aq3610 is a patented product of Houghton international company. It has inverse solubility, and its viscosity is much lower than that of PAG quenchant, thus reducing the amount of polymer brought out by the workpiece after quenching. Moreover, it has unique cooling performance. The cooling rate at 300 ℃ is as slow as that of oil-based quenchant, and the cooling rate at high temperature is faster than that of oil. 5% - 25% aq3610 quenchant can meet the cooling speed requirements from induction quenching to large forgings and castings quenching and tempering treatment. After quenching, it can be tempered directly without cleaning

in recent years, with the increasing shortage of oil resources and the common emphasis on environmental protection that human tear strength values are generally related to sample shape, tensile speed and experimental temperature, a large number of water-based quenchants are widely used in heat treatment processes, including polyvinyl alcohol (PVA), polyalkylene glycol (PAG), polyethylene glycol (Gly), polyvinylpyrrolidone (PVP), alkaline polyacrylate (ACR), polyacrylamide (PAM) Water based quenchants composed of high molecular polymers containing strong polar groups such as methyl cellulose (CMC) as basic thickeners have become the development direction in the future

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