300 ℃ cooling rate evaluation method

　　The first index of water-soluble quenching medium is to reduce the cooling rate in the low temperature stage while maintaining or basically maintaining the fast cooling rate in the high temperature stage. The most representative temperature of the low temperature stage is around 300 ℃. The cooling rate obtained when the steel is cooled to around 300 ℃ is called the   Cooling rate at 300 ℃  Theory and experiments have proved that the cooling rate of the quenching medium at around 300 ℃ plays a decisive role in the quenching of most steel workpieces. Therefore, the cooling rate value of 300 ℃ is selected to grade the quenching medium, and the latest international standard (ISO/DIS950) method is selected to determine the cooling rate of the pantone medium at 300 ℃, which is used as the reference value of the 3001 cooling rate of steel parts for grading.

table 2-14 common quenching medium grading results

serial number medium grade description

1 tap water 90 water temperature 30 yi, unstirred

2 NaOH aqueous solution 5% (mass fraction) 100 water temperature 30 ℃, unstirred

3 NaCl aqueous solution 5% (mass fraction) 90 water temperature 30 ℃, unstirred

4 saturated calcium chloride 50 liquid temperature 40~70 ℃, unstirred

5 3 nitrate aqueous solution 70 liquid temperature 30 ℃, unstirred

6 trichloride aqueous solution 80 liquid temperature 30 ℃, unstirred

7 PAG quenching agent I5%(mass fraction) 20-30 ℃, different varieties), no agitation

8 today 8-20(PAG) 15% (mass fraction) 20 liquid temperature 30 ℃, no agitation

90 diesel 30 oil temperature 40?50 ℃, unstirred

10 20# diesel 0 oil temperature 40?50 ℃, unstirred

11 fast quenching oil 0-20 (depending on variety) oil temperature 40-50 ℃, unstirred

12 alkali bath 0 oil temperature 160 ℃ dissolution temperature, unstirred

　　Note:

　　(1) No. 9~12 are water-insoluble quenching media. The corresponding grades are listed here only to illustrate the cooling rate of 300 ℃. Because their cooling rate distribution is very different from that of water-soluble quenching medium, the quenching effect when used for quenching is very different from that of water-soluble quenchants of the same level.

　　(2) quenching medium with variable PAG content and thus adjustable cooling characteristics. Usually reduce the content and increase the level; increase the content and decrease the level. This table is rated at 15%, which is basically the lowest possible level for various PAG quenchants.