Impact Mechanism of Interfacial Polymer Film Formation in Aqueous Quenchants

Abstract

The results of studies of the cooling ability, rheological and surface-active properties of aqueous solutions of polyalkyleneglycol, sodium salt of carboxymethyl cellulose and polyacrylamide are presented. The choice of polymers is due to the problem of studying the mechanism of the cooling process in aqueous solutions of polymers. Comparison of the results of complex studies and video surveillance made it possible to propose a substantiated version of the mechanism of heat transfer during cooling of a metal sample in aqueous solutions of polymers. At the moment of shock boiling, a substance is formed in the wall layer, which is a nanosol (for PAG solutions) or a nanogassuspension (for Na-CMC and PAA). Under the action of a shock wave, it is directed from the heated metal surface to the interface between the polymer solution-vapor film, forming an interfacial polymer shock film. One of the stages of the shock mechanism of the formation of a polymer film is the adsorption increase in the polymer concentration on the surface of the bubbles formed during shock boiling; the next stage, the polymer shell of the bubbles, is spent on the formation of an interfacial polymer film. Heat fluxes and heat transfer coefficients are presented as a function of polymer concentration and surface temperature. The research results can be useful for assessing the effect of an interfacial polymer film on the ratio of the initial, first q cr 1 and second q cr 2 critical heat fluxes density, which determines the passage of heat transfer stages in water-polymer quenching media (WPQM).

Cooling process optimization during hardening steel in water polyalkylene glycol solutions

“…Evaluation Kn numbers for PAG-35 solutions. Authors of [18] investigated cooling intensity of PAG solutions with molecular mass equal to Mm=35•10 3 (PAG-350). Instead of standard cylindrical probe 12.5 mm they used cylindrical probe 10 mm diameter.…”

“…Cooling parameters obtained by testing cylindrical probe 10 mm diameter at bath temperature 20 °C with no agitation[18] …”