Abstract
In order to establish a method for phase analysis of rare earth elements in hot rolled steels, the chemical behavior of various compounds of rare earth elements, both synthesized and extracted from the steels, were investigated.
The extraction of compounds of rare earth elements from the steels was carried out well by electrolysis in non-aqueous medium, and the extracts were found by X-ray diffraction to contain sulfide, oxysulfide (RE) 2O2S and/or oxide of rare earth elements.
The procedure for phase analysis of rare earth elements in steel is as follows:
(1) 0.5-2g of sample is electrolytically decomposed in 600 ml of methly alcohol containing 5% triethanolamine and 1% tetramethyl ammonium chloried at a current density of 50mA/cm2 under nitrogen atmosphere, and the extracted residue is filtered.(Separation of combined rare earth elements)
(2) Amount of metallic rare earth elements is calculated by subtraction of combined rare earth elements fraction from the amount of total rare earth elements.
(3) The extracted residue is then treated with the 50ml of I2-methly alcohol (10%) at room temperature for 30 min and filtered again.(Separation of oxy-sulfide and oxide of rare earth elements)
(4) Amount of sulfide of rare earth elements fraction is calculated by subtraction of the amount of oxy-sulfide and oxide of rare earth elements fraction from the combined rare earth elements fraction.
The method for phase analysis was applied to several hot rolled steels containing various amount of rare earth elements and sulfur.
The result showed that the anisotropy (C/L) of impact values, the ratio of impact value normal to rolling direction and the one parallel to it under the same condition, is considerably effected by the yielding rtio (r) of sulfide of rare earth elements
(r= S as RE sulfide/S as (Mn sulfide+RE sulfide)).
The relation was observed to be approximately represented by the formula.
