R N (Nick) Younger MA FREng (1934–2010)

New macrosegregation criteria for quality problems in continuous casting of steel

“…These results agree well with many studies that investigated surface and internal defects. 5,17,[47][48][49][50][51][52] The authors concluded that the cooling conditions of the upper spray zone control the propagation of surface cracks and the initiation of halfway crack by controlling the potentially low hot ductility spots. 49 Kohno et al 48 and El-Bealy 5 pointed out that the air-water mist nozzle in the upper spray zones affect considerably the degree of homogeneity of the cooling pattern between rolls and therefore minimise the different surface crack propagation.…”

“…5,17,[47][48][49][50][51][52] The authors concluded that the cooling conditions of the upper spray zone control the propagation of surface cracks and the initiation of halfway crack by controlling the potentially low hot ductility spots. 49 Kohno et al 48 and El-Bealy 5 pointed out that the air-water mist nozzle in the upper spray zones affect considerably the degree of homogeneity of the cooling pattern between rolls and therefore minimise the different surface crack propagation. Donaldson 51 reported that overcooling in the upper spray cooling zones as well as excessive pinch roll pressure, especially in the upper spray zone, are factors responsible for the formation of high positive segregation level and therefore halfway crack formation.…”

Reoxidation of direct reduced iron in ambient air

“…1 Schematic representation of experimental arrangement The degree of reoxidation a is defined as a~w eight of oxygen gained by the DRI during reoxidation weight of oxygen required for conversion of metallic iron and residual FeO to Fe2O3 (3) In this definition, the residual oxygen in the DRI (as FeO) may be taken into consideration or it may be neglected. 21 In the present investigation, it is taken into account.…”

“…The sensitivity of DRI to reoxidation is affected by the reduction temperature at which it is produced from iron oxide pellets. 3 The lower the temperature, the larger the pore surface area and consequently the greater is the tendency for reoxidation. 4 A high carbon content leads to an increase in its stability against reoxidation, especially when the carbon is combined with iron as cementite.…”

“…9-14 A practical solution for its passivation against reoxidation is achieved by its cooling in a controlled, slightly oxidising atmosphere. 3 Reoxidation greatly influences the economics of steel making from DRI. The electric power consumption increases by about 12 kW h t 21 of liquid steel, and the yield decreases by 0?4% for each decrease in 1% in the degree of metallisation, when the metallic charge of a 70 t EAF contains about 88%DRI.…”