The choice of gear quenching medium

by:Hengyang Furnace     2021-01-09
The choice of gear oil quenching medium currently used in gear quenching medium is mainly all kinds of quenching oil, water soluble quenchant and ordinary tap water. The following respectively discuss these in the gear quenching medium selection method and the matters needing attention. 1, the tap water is the most economic and clean quenching medium. Some low carbon content, hardenability and simple shape gear quenched and tempered hardening and induction heating quenching, often can use tap water. As a quenching medium, water cooling characteristic is: when the workpiece in high temperature stage cold quickly, and the workpiece in the stage of low temperature cooling too quickly. Poor cooling speed can make the hardenability and relatively large and thick workpiece hardening. Is this tap water. Use tap water quenching have three major drawbacks, however, the first is the low temperature cooling fast prone to make the most of the steel grade and workpiece quenching crack. The second is the comparison of the workpiece cooling high temperature stage quickly, slender and thin workpiece deformation quenching easily because of the improper into the water. Third, and many people are easy to overlook the faults, as the temperature increases, the quenching cooling steam membrane phase will grow, and artifacts in the stage of low temperature cooling rate also gradually reduced. Because of this reason, when the workpiece is relatively dense pile up ways into the water quenching, water only through the pile of the gaps between the workpiece outside contact inside the workpiece. Through the workpiece when the water temperature rise gradually. So that pile of workpiece contact outside temperature is low, and heap inside workpiece contact with the water temperature is high. The stack, and external different workpiece quenching cooling effect. Outside of the workpiece cooling fast, high hardness after quenching, quenching crack and easily. Stacked in internal artifacts of slow cooling, low hardness after quenching. Workpiece stacking the more densely populated, the movement of the water quenching the less unobstructed, the greater the difference. This defect that tap water is not applicable to small workpiece quenching dense pile up. When using oil quenching oil temperature, cooling steam membrane phase slightly shorter, and high oil temperature rise make the oil viscosity reduce liquidity is good, can help improve the cooling speed of oil, can make the pile up more intensive workpiece inside and outside the cooling effect. Ought to say, this is an advantage of quenching oil. Use tap water as a hardening liquid, should know the advantages and disadvantages of it. Good use of its advantages and avoid its disadvantages. Try to control the temperature of the water. Stacking ways when quenching, try to make the workpiece stacked loose some, and through stirring prompted quenching liquid flows between free from artifacts, to reduce the internal temperature of water. 2, water soluble quenchant tap water as the biggest drawback is the low temperature of quenching medium cooling speed is too fast, make a variety of steel workpiece quenching crack easily. Cause steel quenching crack is the main reason of the water in the martensitic transformation temperature ( Ms points) And the following the temperature range of cooling too fast. Because of this reason, the research and development of water-soluble quenching medium for the first goal is to reduce the water cooling rate at low temperature. Considering most of the structural steel Ms point around 300 ℃, usually to a workpiece cooling to 300 ℃ when the water-soluble quenching liquid cooling speed, the so-called 300 ℃ cooling rate the cooling performance of the quenching liquid. Usually can use water-based quenching medium 300 ℃ cooling speed to the grading of medium [ 2] So that workers choose heat treatment. In a nutshell, 300 ℃ water quenching liquid cooling rate is low, its ability to prevent the workpiece quenching crack is strong; 300 ℃ cooling rate is high, the hardening capacity is high also, of course the workpiece quenching cracks tend to be too big. Therefore, the choice of water-soluble quenching medium should first understand its cooling rate of 300 ℃. Same type of quenching medium varieties, have the same 300 ℃ cooling rate when the concentration is lower, and the lower cost of use. Aqueous quenching medium has many varieties, different varieties have different characteristics. PAG class medium cooling characteristics is adjustable, concentration measurement and control easily. It applies to both the overall quenching, can also be applied to all kinds of induction heating quenching, long-term stability and can use, so popular, become the heat treatment industry both at home and abroad the most widely used water quenching medium. Due to large liquid temperature influence on the cooling characteristics, using water soluble quenchant shall be equipped with good circulation cooling system, so as to adjust the liquid temperature in the use, the general said, the water-soluble quenching hardening liquid, the workpiece is unfavorable also under the condition of dense piles into the water, so as not to cause internal and external artifacts are obviously different quenching effect.
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