No abstract

The present paper discusses the influence of experimental conditions on the quenching performance of poly(2-ethyl-2-oxazoline) (PEOX) aqueous solutions used as cooling medium, using a standard ISO Inconel alloy probe for measurements of cooling rate. The evaluation procedure is demonstrated on characterization of cooling power of water-based polymer (PEOX) solutions by using different concentration, temperatures, and agitation conditions of the cooling media. The results show that the different experimental conditions have a significant effect on the cooling performance. The polymer quenching mechanism and the comparative cooling characteristics of water, and water-based PEOX polymer solution with concentrations from 2.5 to 15 wt.% were discussed. The study involved the assessment of the quenching severity by calculating the hardening power (HP) via empirical equations. Calculation of heat transfer coefficients as well as prediction of microstructural constituents and the hardness profile in a cross-section of steel sample were carried out on the basis of inverse calculation from the recorded cooling curve.

Laboratoire d'e ´tudes physico-chimiques des mate ´riaux, application a `l'environnement (LEPCMAE),

Solutions of high molecular weight polymers are used widely in the heat treatment of metal alloys known as quenching. Water-soluble polymers offer a number of environmental, economic, and technical advantages, including eliminating the quench-oil fire hazard. The cooling power of water-soluble polymers such as polyethylene glycol (PEG) and salts aqueous solutions is studied with a cylindrical test probe of Inconel 600 by using a quenchometer. The dependences of the cooling rates, at each bath temperature, on polymer concentration and agitation are established. The present paper describes, through an understanding of the quenching mechanism, the effect that some parameters concerning the control of polymer quenchants have on their behavior. The effect of the salts on the quenching characteristics has also been studied. A study has been made of the relationship between the concentration of PEG, bath temperature, agitation, and cooling power in aqueous quenchants that contain up to 20 % of PEG. The presence of 5 % or less of the polymer in solution increased the cooling power of the quench in comparison with the water quenchant. However, increasing polymer concentration will decrease the cooling power as well as the maximum cooling rate because of the formation of the vapor blanket in the first phase of the quenching mechanism. The hardening power (HP) of the PEG quenchant solution was characterized on the cooling curve by the two critical points, CRF (the cooling rate at the ferrite/pearlite nose) and CRM (the cooling rate at the martensite start transformation), using an empirical relation giving HP in function of the measured polymer quenchant cooling characteristics. The highest HP was obtained in dilute solution of PEG having a concentration of 2.5 %, which reaches a value of 2051 at 20°C and 1951 at 45°C, under agitation.