Keywords: Quench, evaluation, performance, probe, quenching medium, cooling, center silver probe, thermal oxidation resistance, sensitivity, reaction rate,

　　 Regarding the probe used in the evaluation of the cooling performance of the quenching medium, there are still big differences in the international academic community. The focus of the differences lies in the structure and material of the probe. There are basically two kinds of probes used in China.
　　 The 1 is Φ10x 30mm cylindrical center even silver probe, standard number SH/T0220. This kind of probe is actually a combination of French A.T.T.T Phi recommend by the quenching fluid group of the S.F.M joint committee; The 16x 48 cylindrical central even silver probe and the Japanese Osaka surface even silver probe are developed with different characteristics. Its advantages are good thermal oxidation resistance, high sensitivity and fast reaction speed, but the repeatability and reproducibility of the test are relatively low.
　　 The 2 is Φ12.5mm x 60mm cylindrical center nickel alloy, which is the Inconel600 probe specified in the ISO9950 standard. The advantage is that the repeatability and reproducibility of the test are good, but the thermal conductivity is low and the sensitivity is poor. It is not suitable for the cooling performance of quenching medium such as water, quenching salt and low concentration synthetic quenching liquid.

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