Preparation of quenching liquid
Clean the quenching tank and the cooling cycle of devices, then fill the quench tank with clean tap water to 50% of the working surface, add the YIY-PAG quenching agent according to a predetermined concentration ratio, and cycle mix, add tap water to the normal work surface, then cycle mix it about 2 to 3 hours . It can be used after the determination of the concentration.
2 Selection and determination of quenching liquid concentration
2.1 Selection of the concentration 
 medium carbon structural steel: 3-8%;
high carbon and alloy steel: 8-15%;
medium or high-alloy steel: 15-22%;
Based on: the chemical composition effect, small size effect, shape effect, heat treatment equipment, technical requirements and other factors to select its concentration. The specific concentration can be determined by coming to an agreement between the users and our company technical experts.
2.2 Measure and control of the concentration
The concentration of quenching liquid usually can be measured by the sugar-based hand-held Refractomete whose BX value is 0 to 15. The details are as follow: 
1) Proofread apparatus

 Drop a few drops of water on the eyeglass, then close the plastic lens (make sure the water fill the entire eyeglass), fast rotate and adjust the focal distance ratio of eyepiece by facing the light until clearly appearing the boundary of blue and white line, and to make boundary line over the "0" line. If the boundary line and "0" line don’t match together (over or under the "0"), the adjustment is as follows: 
  Above the "0" line

Write down the number of error grids between the boundary line and the "0" line. The actual value is the measured value with the minus the margin of error. 
Under the "0" line Rotate the adjustment screw on the instrument with the small screwdriver packed in the instrument, make the boundary line and the “0”line match together.
2) Measure Clean up the tap water on the lens and the lens trace with soft and thin cotton after proofreading the apparatus, then drop a few drops of quenching liquid by pipette (quenching liquid should mix up about 30 minutes before measure, and the pipette should clean several times with the quenching liquid before using) on the lens and cover the plastic lens, observe in the front of bright light and note the value of the BX corresponds to the blue and white boundary line.
3) Calculation The using concentration is the value of measured BX multiplied the concentration index of 2.5, the concentration fluctuation should be controlled to within ± 0.5% range. 
For example: the value of the measured BX = 2.2, if the boundary line to the "0" line drift error of is 0.2,
so the actual concentration value（%）=（2.2-0.2）×2.5=5.0%
When the quenching liquid has been used for a long-term, it can be contaminated, there is a certain deviation between the measured concentration value by Refractometer and the actual concentration value(usually higher than the actual concentration). So, the kinematic viscosity or cooling performance of quenching liquid should be measured periodic (usually 3-6 months), in order to modify the concentration multiplied index by the comparing result of measured values in the initial and after service.
3 The control quenching liquid temperature 
YIY-PAG series of quenching liquid should be used below its inverse melting point about 20 ℃. Usually, the production temperature should be controlled at 20-50 ℃. When the concentration is determined, the cooling rate will be reduced with rising the liquid temperature. In order to obtain a consistent quenching effect, the quenching liquid temperature should be controlled in a more narrow range (best of 30 ± 10 ℃) based on quenching the work piece hardness and mixing intensity of solution. For example, the temperature is too high in summer, the cooling system can not immediately reduce the quenching liquid temperature to provisions range, which can be improved by adding to the tap water. The Theliquid temperature is too low in winter, the quenching cooling rate can be increased by heating the quenching liquid or increasing the concentration of quenching solution.
4 Control of mixing Well mixing can improve the cooling characteristics of quenching liquid (in a certain concentration and fluid temperature, increasing mixing intensity can improve the cooling quench rate), so that different parts of the work pieces can obtain uniform cooling effect.  Good mixing will not only improve the uniformity of its own quenching fluid temperature and concentration, but also can slow the deterioration rate of quenching liquid. 
In order to obtain a good cooling effect of quenching and extend the life of the liquid, it is recommended by pipeline pump mixing, use of compressed air mixing is strictly prohibited. The relative movement speed of quenching liquid and the work piece surface should appropriately control at within 0.2-0.6 m/s. The variable speed mixing device can be designed and installed by it.
5 Measures of preventing the quenching liquid polluting

 In order to ensure a good cooling characteristic of quenching liquid, the quenching liquid should be maintained to avoid the rain, oil, oxide, dust and other foreign material polluting in the production field. Excessive pollution not only affects the cooling effect, but also may cause the entire quenching agent scrapped. theT common quenching liquid pollution can be divided into oil contamination, insoluble solid granule and solvent water pollution contamination. It will be treated depending on the particular circumstance.
Oil pollution: the majority of oils used in the factory do not dissolve in water. In general, small amount of floating oils on the surface effect the cooling characteristics of quenching liquid only a little. Therefore, the quenching liquid can still be used as long as the oils are fished out in a periodic time or absorbed by old newspapers. If the quenching fluid mixed with soluble oil, it will directly affect the cooling characteristics of quenching liquid, which should be avoided.
Insoluble solid particles pollution: such pollutions are mainly the oxide shins, carbon black, dust, etc. from the outsides. It will not affect the cooling characteristics of quenching liquid if the pollution is not very much and it does not affect the mixing and circulation of the quenching liquid. Suspended solid particles tend to increase the refractive index of the quenching liquid, which makes the reading concentration by Refractometer a little higher. Excessive oxide shins should by removed by filter. 
Water soluble substances pollution: This type of pollution mainly contains the soluble salt, alkali pollution, such as NaCl, NaOH and other substances. They tend to increase the quenching liquid refractive index and affect the cooling characteristics of quenching liquid, which should be avoided. 
Special treatment in production processing

 In the hot and humid summer, the quenching liquid should be mixed cycle about 1-2 hours every 3-7 days in order to enhance anti-corruption and self-quenching liquid anti-corrosion ability if there is a long time not using the quenching liquid.