Keywords: method, IVF, hardenability method, hardenability index method, steam film, boiling stage, transition temperature, characteristic temperature, average cooling rate, convection,

　　IVF (Swedish Institute of Production Engineering Research) hardening capacity method or hardening capacity index method, the formula is
　　HP = K₁+ K₂T_vp+ K₃CR-K₄T_cp
　　where: T_vp is the transition temperature (characteristic temperature) from steam film to boiling stage; CR is the average cooling rate between 600 and 500 ℃; T_cp is the transition temperature from boiling to convection stage; K₁, K₂, K₃, and K₄ are constants.
　　The calculation for hardening capacity of ISO 9950 standard quenching oil is
　　HP = 91.5 + 1.347Tvp + 10.88CR-3.85T_cp
　　the calculation formula for the hardening capacity of SH/T0220 standard quenching oil and the hardening capacity of aqueous organic solution is
　　HP = 300 + 0.9Tvp + 9CR +3T_cp　　 (quenching oil)
& nbsp; & nbsp; HP = 300 + 0.9Tvp + 9CR-40T & nbsp; cooling time of 150°C, s.

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