Studium tepelné vodivosti porézní vrstvy oxidů

Study of thermal conductivity of the porous oxide layer

článek ve sborníku ve WoS nebo Scopus

en

Steel production and processing are connected with high temperatures. Due to a reaction between hot surface of the steel and oxygen contained in surrounding atmosphere, oxides are formed on the surface of the steel. Created layer of oxides is called scales and has influence on cooling and quality of steel. Thickness and structure of scale layer are influenced by chemical composition of the steel, temperature and atmosphere during oxidation. Scale layer can be considerably porous which has a significant influence on thermal conductivity of this layer, because air pores have much lower thermal conductivity compared to scales. Steel samples were prepared and porosity of scale layer was studied. Further, the average thermal conductivity of porous scale layer was determined for different regimes of oxidation by FEM modelling. It was found that the average thermal conductivity of porous scale layer is influenced not only by porosity of scale layer, but also by distribution of air pores, which can has a significant effect.

Výroba a zpracování oceli probíhají za vysokých teplot. Vlivem reakce mezi horkým povrchem oceli a kyslíkem obsaženým v okolní atmosféře dochází na povrchu oceli ke vzniku oxidů, kterým se říká okuje. Vrstva okují ovlivňuje proces chlazení a kvalitu oceli. Množství a strukturu okují ovlivňuje složení oceli, teplota a atmosféra, při nichž dochází k růstu okují. Vzniklá vrstva okují může být značně porézní, což má výrazný vliv na její součinitel tepelné vodivosti, protože vzduch obsažený v pórech má oproti oxidům výrazně nižší tepelnou vodivost. Na ocelových vzorcích byla zkoumána poréznost vrstvy okují a pro různé režimy oxidace byl stanoven průměrný součinitel tepelné vodivosti porézní vrstvy okují. Bylo zjištěno, že průměrný součinitel tepelné vodivosti porézní vrstvy okují je ovlivňován nejen porézností vrstvy okují, ale také rozložením pórů ve vrstvě, které může průměrný součinitel tepelné vodivosti výrazně ovlivnit.

Steel production and processing are connected with high temperatures. Due to a reaction between hot surface of the steel and oxygen contained in surrounding atmosphere, oxides are formed on the surface of the steel. Created layer of oxides is called scales and has influence on cooling and quality of steel. Thickness and structure of scale layer are influenced by chemical composition of the steel, temperature and atmosphere during oxidation. Scale layer can be considerably porous which has a significant influence on thermal conductivity of this layer, because air pores have much lower thermal conductivity compared to scales. Steel samples were prepared and porosity of scale layer was studied. Further, the average thermal conductivity of porous scale layer was determined for different regimes of oxidation by FEM modelling. It was found that the average thermal conductivity of porous scale layer is influenced not only by porosity of scale layer, but also by distribution of air pores, which can has a significant effect.

Oxidy, okuje, poréznost, součinitel tepelné vodivosti

Oxides, scales, porosity, thermal conductivity

13.05.2019

Institute of Thermomechanics of the Czech Academy of Sciences

Praha

978-80-87012-71-0

Engineering Mechanics 2019 Book of Full Texts

1

315–318

4