Constitutional Diagram of Ternary Fe-Ca-Si Alloys

Microstructural observations, thermal analyses, chemical analyses and X-ray diffractions have been made of the alloys melted with arc or high-frequency induction in argon atmosphere, the compositions of which lie in the field of two-liquid immiscibility and one-liquid phase. The results may be summarized as follows : With increasing content of silicon or of aluminium, the miscible gap of the field of the Fe (Mn)-Ca system became narrow and had a critical point at nearly 33% Fe (Mn)-33%Ca-34%Si(Al), at which the two-liquid phase became indistinguishable. Above 35% silicon or aluminium content, only one liquid solution existed over the entire composition range of the alloy system. It was assumed that a quasi-binary eutectic point should appear in the vicinity of 23%Fe-38.5%Ca-38.5%Si for a quasi-binary system existing between the binary intermediate compounds CaSi and FeSi. Freezing of alloys involving ternary three-phase equilibrium was completed at 1030℃ and the composition of this ternary non-variant point lay upon 5%Fe-35%Ca-60%Si. In the field of only one liquid solution there were four primary phase regions of Si, CaSi, FeSi and FeSi_2. As morphological features, Si appeared in rectangular form, FeSi in dendritic or spherical form, and CaSi and FeSi_2 in band or plate-like form

Production of Ferrosilicon for Nodularizer by Silicothermic Reaction(Metallurgy)

Silicothermic reduction method was applied to produce ferrosilicon which contains Mg and other alkali earth metals and which is a powerful nodularizer of graphite in cast iron. Ferrosilicon was melted in a high frequency induction furnace using a MgO-lined crucible and treated by fluxes of powdered MgO CaO, SrO, BaO or CaCO_3+MgCO_3. Mg content of the ferrosilicon increased with the reaction temperature. Contents of other alkali earth metals were approximately in proportion to their boiling points. The nodularizing characteristics of the ferrosilicon were compared by examining the cast iron treated by them microscopically. The fading tendencies of nodularizing action were evaluated indirectly from the effect of the holding time after inoculation on the chilling depth of gray cast iron treated by various ferrosilicon and calcium silicide. From the results of these tests, it was concluded that the ferrosilicon containing small amounts of Mg and Ca reduced from their oxides can be used as an effective nodularizer for cast iron

Process of Graphite Precipitation in Calcium Graphite Steel

The effect of calcium on the graphite precipitation from the γ phase of a hypereutectoid steel has been examined with an apparatus newly designed for the measurement of solidifying contraction. It was ascertained that the graphite precipitation in the solidifying process occurred over the range from the vicinity of the saturation curve E\u27S\u27 of the γ phase (Agr point) to the A_1 point, and that the graphitization took place most remarkably near the A_1 point. The addition of a large amount of metallic calcium or of Fe-Ca-Si alloy greatly affected the solidifying contraction curve, leading to a considerable expansion due to ferrite formation near the A_1 point. In this case the rise of the A_1 point was not observed, although Si content increased. The addition of Fe-Ca-Si alloy as the graphitizing agent increased the amount of residual calcium more than that in the case of the addition of metallic calcium

On the Embrittlement and Toughness of High Purity Fe-30Cr-2Mo Alloy

Experiments were conducted to explain unexpected embrittlement phenomena encountered in fabricating a high purity Fe-30Cr-2Mo alloy. By means of a hydrostatic tensile test with a Bridgman-Type specimen it was found that the fracture behaviour of the alloy is highly dependent on stress state. Under conditions of low triaxial stress, the alloy displays excellent ductility. Under conditions of high triaxial stress, however, the alloy shows less strain to fracture and a transition from ductile to cleavage fracture. The toughness of the Fe-30Cr-2Mo alloy can be significantly improved by thermomechanical processing

Formation of Lamellar and Spheroidal Graphite in Cast Iron in Relation to the Micro-Segregation of Silicon

By the addition of ferrosilicon to molten cast iron, not only is there the inoculating effect but also under certain conditions spheroidal graphite can be formed. In order to investigate the role of silicon as an additive, experiment was carried out using the potentiostatic technique as a means of etching the primary structure. When the melt was treated with large amounts of refined ferrosilicon, microregions in which silicon was highly concentrated were observed in the cast state and spheroidal graphites were mostly formed in such regions. This suggests that the formation of spheroidal graphite is related to the local super-saturation of carbon caused by adding silicon to the melt

Effects of Sulphur, Oxygen and Silicon on Graphite Precipitation in Calcium Graphite Steel

Effects of sulphur, oxygen and silicon on the graphite precipitation in calcium graphite steel were investigated. Sulphur greatly hindered the precipitation from γ solid solution. According as the amount from 0.03 to 0.18% of sulphur, primary cementite appeared not only in the matrix but also in the grain boundary. With increasing oxygen content above 0.008%, graphitization decreased and also primary cementite crystallized out preferentially from the γ solid solution. When the hypereutectoid steel was melted in vacuum, graphitization did not occur without a suitable addition of silicon. Fundamental conditions on graphite precipitation by the calcium treatment were summarized in the following three points : (1) effect of deoxidization and desulphurization, (2) instabilization of cementite to precipitate from the γ solid solution, and (3) formatian of crystal imperfections such as voids in the solidifying process. Effective acceleration of graphite precipitation due to silicon was also discussed

The Effect of Melting Condition on the Properties of High Chromium Ferritic Steels(Metallurgy)

The influence of melting atmosphere and impurity elements on the hot workability of Fe-30%Cr alloys and the effect of vacuum and Ca refining on the mechanical properties have been studied. The results obtained are as follows. The deformation resistance of zone refined heat with the lowest impurity content is from 23 to 13 kg/mm^2 in the temperature range of 850°to 1300℃. Increasing the interstitial elements such as C and N in the vacuum-melted heat raises the deformation resistance in any hot-working temperature. However, the contents of O up to 0.2%, S up to 0.1%, Mn up to 2%, Si and Al up to 0.5% have not any significant effect on the deformation resistance. The heats of more than 0.017%C reveal intercrystalline fracture from above 1200℃. The crack initiations due to the cluster of alumina or chromium oxide inclusion are also observed. It is ascertained that the globular type inclusions found in the vacuum and Ca refined heats consist mainly of calcium aluminate, and their tensile strengths are approximately 45 to 65 kg/mm^2 with elongations of 28 to 35% at room temperature -72°and -120℃, and the ductile fracture with a fine dimple pattern is observed