Průval bramy jako důsledek změny chemického složení kontunuálně lité oceli

A breakout of a slab as effect of the change of chemical composition of a concast steel

conference paper

en

An important area of the caster is the so-called secondary cooling zone, which is subdivided into thirteen sections. In the secondary-cooling zone, where the slab is beginning to straighten out the breakout of the steel can occur in points of increased local chemical and temperature heterogeneity of the steel, from increased tension as a result of the bending of the slab and also from a high local concentration of non-metal, slag inclusions. Especially dangerous are the changes in the chemical composition of the steel during the actual concasting. In the case of two melts one immediately after the other, i.e. when melt of steel of quality A finished and right now the melt of quality B followed, this could lead to interruption in the concasting and a breakout. The material, physical, chemical and technological parameters, which both melts differed in were determined. The parameters from the temperature field were calculated by means of the model, for example maximal and minimal lenghts of isoliquidai and isosolidai, the range of so-called mushy zone with temperature between liquidus and solidus, the temperature of surface slab and so on. If the dimensionless analysis is applied for assessing and reducing the number of these all parameters, then it is possible to express the level of risk of breakout as a function of five dimensionless criteria.

V sekundární zoně chlazení, kde se brama začíná narovnávat, může docházet k průvalu v místě lokální chemické a teplotní heterogenity oceli vlivem rostoucího napětí vyvolaného ohýbáním bramy a také vysoké koncentrace nekovových, struskových vměstků. Zvláště nebezpečné jsou změny v chemickém složení oceli při kontinuálním lití. V případě dvou následných taveb může nastat přerušení kontilití a průval. Jsou stanoveny materiální, fyzikální, chemické a technologické parametry dvou různých následných taveb. Při použití dimenzionální analyzy pro upřesnění a redukci počtu parametrů, je možné vyjádřit stupeň nebezpečí průvalu jako funkci pěti bezrozměrných kriterií.

An important area of the caster is the so-called secondary cooling zone, which is subdivided into thirteen sections. In the secondary-cooling zone, where the slab is beginning to straighten out the breakout of the steel can occur in points of increased local chemical and temperature heterogeneity of the steel, from increased tension as a result of the bending of the slab and also from a high local concentration of non-metal, slag inclusions. Especially dangerous are the changes in the chemical composition of the steel during the actual concasting. In the case of two melts one immediately after the other, i.e. when melt of steel of quality A finished and right now the melt of quality B followed, this could lead to interruption in the concasting and a breakout. The material, physical, chemical and technological parameters, which both melts differed in were determined. The parameters from the temperature field were calculated by means of the model, for example maximal and minimal lenghts of isoliquidai and isosolidai, the range of so-called mushy zone with temperature between liquidus and solidus, the temperature of surface slab and so on. If the dimensionless analysis is applied for assessing and reducing the number of these all parameters, then it is possible to express the level of risk of breakout as a function of five dimensionless criteria.

kontinuálně litá brama, změna chemické složení, průval , kriteria

concast slabs, change of chemical composition, breakout, criteria

2011

06.04.2011

Tanger

Ostrava

978-80-87294-21-5

Sborník přednášek Teorie a praxe výroby a zpracování oceli (ročník 27)

1

89–94

6