Abstract
Objects of investigations are water solutions of polyalkylene glycol (PAG) which are used as the quenchants in the heat-treating industry. They are tested by standard cylindrical probe made of Inconel 600 material. The main and not solved yet is the problem of transition from data achieved for standard probe to data suitable for any form and size of real steel part. It opens possibility to make predictable calculations. Taken this into account, it has been investigated water solutions of PAG of different concentration. It is underlined that cooling intensity of quenchant can be evaluated by Kondratiev number Kn. The mentioned number Kn varies within 0≤Kn≤1 when generalized Biot Biv number varies within 0≤Biv≤∞. As a main achievement of investigation is established correlation between standard Kn number and Kn number of real steel part. In many cases, when film boiling is absent, the established correlation is a linear function. It allows optimizing quenching processes: obtain high surface compressive residual stresses, save alloy elements and improve environment condition. All of this is achieved by tolerating chemical composition of steel with size and form of quenched object as it is proposed by UA Patent No. 114174. Also, the number Kn allows interruption of quench process when surface compressive residual stresses are at their maximum value that essentially improves the quality of steel components. Moreover, interrupted cooling prevents quench crack formation, decreases distortion of quenched steel parts. The results of investigations can be used by engineers in the heat-treating industry and scientists for further research.
Highlights
As discussed in references [1,2,3], there are several ASTM Standards for testing cooling intensity of liquid quenchants
In heat treating industry intensive quenching (IQ) process is used that requires cooling time interruption at proper time depending on chemistry of steel and condition of cooling [6, 7]
Deformation of cooling rate curves is observed when quenching in 15 % and 20 % polyalkylene glycol (PAG) water solutions
Summary
As discussed in references [1,2,3], there are several ASTM Standards for testing cooling intensity of liquid quenchants. The designed standards allow maintaining liquid quenchants in stable condition and provide their perfect control by comparing cooling curves with each other Such approach works perfectly for industrial oils and elevated concentration polymers in water where, as a rule, cooling process lasts almost to bath temperature. To design computer program for cooling time interruption suitable for any steel, and any form and size of hardened product, heat transfer coefficients (HTC) are required for each specific condition of steel hardening. The problem is not solved yet and each specific technology every time requires additional costly experiments Author of the paper proposes a simple method of transition from standard probe to real steel parts of any form and size which could be made from different materials having different thermal properties
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