The heat treatment quenching oil selection principle and method

2020 - heat treatment quenching oil selection principles and method 06 - 23 Wang Lujun ( Gerth lakshmi ( Jiangxi) The transmission system co. , LTD. ) 1. Heat cooling curve of heat treatment process generally includes three heating, heat preservation, cooling process, the heating is for pearlite to austenite transformation, heat preservation is completely austenitizing, cooling method for craft different and different, mainly is to control the cooling speed, with different cooling rate respectively into pearlite, bainite and martensite or hybrid organization. Is usually want martensite quenching, quenching after during tempering respectively according to the different tempering temperature tempered martensite ( Low temperature) Austenite (, Troostite, medium temperature) , sorbite ( High temperature) 。 Eutectoid steel isothermal transformation curve as shown in figure 1, basic reflects the eutectoid steel under different temperature change to shift the incubation time and completion time and its products. Figure 1 eutectoid steel isothermal transformation curve of actual heat treatment except stepped isothermal quenching process in production of continuous cooling. Quenching speed to get martensite structure must be greater than the critical cooling rate, cooling speed of parts surface cooling rate generally greater than the core. Quenching oil one of principle: the choice of quenching martensite, both want cooling rate must be greater than the critical cooling rate, also want to consider reducing deformation, prevent crack, cooling rate must be moderate, not too big. As shown in figure 2. Figure 2 eutectoid carbon steel TTT curve with the CCT curve of 2. Ideal quenching method according to the laws of the steel cooling transformation, in the hope that cooling rate of the critical temperature of the region, through the C curve of the nose area as soon as possible, in order to avoid into pearlite or bainite structure, at the beginning of the martensitic transformation of the danger zone, cooling speed must be slow down in order to reduce shift to produce tissue stress caused by the deformation and crack. Double liquid quenching in water quenching first and then turn to the oil in the cooling of truth is so. Called single liquid quenching cooling medium have such cooling feature: the critical temperature of the region cooling speed, the danger zone temperature cooling speed to slow down. When quenching oil selection principle # 2: high temperature fast cold temperatures when slow cold, both hardness and deformation demands. As shown in figure 3. Figure 3 ideal signal 3 quenching method. Quenching oil cooling curve of the heat treatment quenching oil requires the cooling performance, cooling speed, temperature in the critical region parts parts in the danger zone temperature cooling speed to slow down. Figure 4 for good rich meal MT355 cooling characteristics of quenching oil under different oil temperature curve, shows the sample cooling time, cooling rate and the relationship between temperature, indicates the cooling capacity of quenching oil in different temperature. Figure 44. Hardness requirements and deformation influence the critical cooling rate of different materials, parts of hardness requirement is different also, when using the precision of parts, deformation control requirements are different, this needs according to the technique requirements of hardness requirements and control the deformation of the actual situation, select the cooling speed of quenching oil. After quenching oil selection, through the control of raw materials ( Parts material and product) Quality and choice of adjustment of quenching temperature, cooling speed and oil temperature, stirring time, into the oil time, etc. Various control measures, combining with the tempering after quenching process, tempering temperature and tempering time parameters to satisfy the requirement of the parts hardness test and metallographic organization requirements, through the process of heat treatment process parameters adjustment and control and coordinated with the cold and hot machining, control heat treatment deformation within a reasonable range. 5. Selection method of heat treatment quenching oil from heat treatment quenching process mentioned in front of the quenching oil selection principles: quenching oil cooling performance must meet the requirements of hardness ( Quick cooling speed requirements) And will never allow to produce cracks, control heat treatment deformation within the scope of the reasonable minimum ( Cooling speed slow) Find a best combination between the two, and the contradiction of cooling speed requirements are put forward in the temperature range for different requirement, it is developed for heat treatment of quenching oil provides a direction. In view of the testing conditions, heat treatment production practice at the factory before we can only according to the general knowledge and experience to make a rough quenching medium range to choose and use test to verify. Cooling apparatus features extensive use is to provide a testing tool analysis method, optimization of quench oil scientific choice for us, contrast analysis for help. We can have a condition inspection or outsourcing or require oil companies to provide cooling characteristics of quenching oil testing data report, which will provide a scientific basis for the selection of quenching oil. According to the above methods, there are many kinds of conform to the requirements of the use of quenching oil. According to the actual production situation and the company quality policy, to meet the requirements of the performance of cooling quenching oil and other technical indicators are compared and the comprehensive comparison, the sifting the most appropriate. Quenching oil stability and oxidation resistance, the cooling performance of repeatability and reproducibility, brightness, safety and cost are the factors to consider. QB / T0001 - 2007, JB/T7951, SH/T0220 cooling oil for heat treatment of kinematic viscosity, flash point, ignition point, water, pour point, corrosion, brightness, saturation vapour pressure ( Vacuum quenching oil) , thermal oxidation stability, cooling performance, maximum cooling rate, cooling time must meet the technical requirements are put forward. 6. Conclusion the selection principles and methods of the quenching oil were introduced. Quenching oil base oil, additives, factors influencing the performance of cooling, interlock. And quenching is extremely important steps in the process of heat treatment, must choose carefully. By analyzing and comparing the primary recommendation can use quenching oil and then supplemented by experimental verification, trade use effect, market survey, comprehensive consideration of technical requirements, safety, quality, cost, etc. , finally determine the choice of the quenching oil. Source: the metal processing ( Hot working) 》