低周波炉による鋳鉄溶湯の特性とその炉前管理

抄録

  The effects of raw materials, melting condition and composition of the iron melted in line frequency furnace on its solidification characteristics and casting properties were investigated by using statistical method, in an intention to find the critical factors in controlling of melting operation.
  The results were as follows.
(1) Quick analysis of composition before casting: The composition can be estimated accurately by measuring the solidification temperature range (ΔT) in thermal analysis. The relation between solidification temperature range and composition can be expressed by following equation.
          %C − 1/(6.4)%Si=3.985−0.00664·ΔT
  By chilling test also the carbon equivalent can be estimated, but only roughly. The strengh, however, can not be estimated by either thermal analysis or chilling test.
(2) Control factors: Control of element such as carbon or silicon, must be done more severely than in cupola operation. The effects of these elements on the characteristics of line frequency furnace melt is stronger than on cupola melt.
  Tensile strength was determined by carbon content and amount of steel scrap (SS%) in charge as shown in following equation.
          T.S.kg/mm²=76.26-16.44%C-0.394SS%
Consequently it is important to control the weight of steel scrap in charge as well as carbon content to obtain the constant strengh.
(3) Line frequency furnace iron v.s. cupola iron: If both iron had been melted from the same charge and had the same composition, chilling and shrinkage tendency were stronger in line frequency furnace iron than in the other. The tensile strength of the iron melted in line frequency furnace was higher by about 7 to 8 kg/mm² than the iron from cupola.
  It was found that eutectic temperature of line frequency furnace iron showed about 10°C lower than cupola melted iron, but showed higher nitrogen content. These facts were considered to be a cause of difference in many characteristics between both iron melts.