In order to improve wear resistance of cast steel, hard alloy powder layer was inserted by molten cast steel at 1843K. The vertical cross-section of the inserted layer was examined on the microstructure and the hardness. The results obtained are as follows. Sound inserted layer of 3mm in thickness was confirmed to be formed without any defects on the surface of cast steel.
A reaction layer with some lump shaped particles was formed in the interface between the inserted layer and the mother metal (cast steel). The lump shaped particles were identified to be Fe₃W₃C phase which had a cubic structure with a lattice constant of 11.1094×10^-8cm. The particles were considered to be formed by a reaction between the Co bond phase dissolving WC in hard alloy powder and the molten iron dissolving low concentration of C in molten steel. The hardness of cast steel was about Hv300, while the inserted layer exihibited high hardness of Hv600 to 800.
Especially, the reaction layer showed peak hardness of Hv1800, but the layer was not brittle. The toughness of the reaction layer was considered to be due to a mixed structure of tough bainite and retained austenite around the hard Fe₃W₃C particles. The present method using the inserted hard alloy powder layer is therefore to be very effective one for local hard facing of cast steel.

View full abstract

The dioxin from the arbage incineration is one of the most serious environmental problems in recent years. There is a method using calcium hydroxide [Ca (OH) ₂] as one of the dioxin preventive methods, reacting in the present garbage incineration and removing the chlorine in combustion exhaust gas. The formation mechanism of specific surface in the calcium hydroxide powder generated by reaction from quicklime is not sufficiently elucidated up to now.
Calcium hydroxide was thought to decrease specific surface area until now in the case where carboxylic acid is used as an addition in calcium hydroxide reaction.
In this paper, the applicability of carboxylic acid to calcium hydroxide reaction, and the morphology formation mechanism of the specific surface of calcium hydroxide is experimentally discussed. As a result, a new triple product factors of the alkyl chain length of the added carboxylic acid, the acidity and the interaction between carboxylic acid and water, were successfully introduced to be reasonably described the experimental result between specific surface area and amount of acid.
And, the optimum alkyl chain ength was experimentally pointed out to exist at 5 showing the maximum specific surface area of calcium hydroxide. Also, the increment effect to specific surface area by carboxylic acid addition was shown to be maximum at 0.05 of the amount of carboxylic acid.

View full abstract

The basicity of fused Na₂SO₄ at 1173 K was successfully controlled by the electrolysis of the salt with platinum electrodes. With progress of the electrolysis, the basicity of the fused salt decreased in the anolyte and increased in the catholyte. The changes in solubility of Al₂O₃, Cr₂O₃ and SiO₂ powders in the fused Na₂SO₄ were examined as a function of the basicity of it using the electrolysis method. The changes in the basicity of the fused salt both for increasing and decreasing resulted in an increase of the solubility of Cr₂O₃ and more significantly of Al₂O₃. On the other hand, the solubility of SiO₂ was independent of the basicity and was extremely low in the acidic region, whereas that increased with decreasing the basicity in the basic region.

View full abstract

It is shown through the use of tin crystal that the actual growth rate in the Bridgman growth process could be investigated by recording the temperature-time curves at given axial locations in the melt-solid system. Variations of the growth rate in the seeded and unseeded growth processes of tin crystal have been examined and discussed. The results are summarized as follows.
It is surmised for the seeded growth that the actual growth rate increased with the progress of solidification, and the average rate was 1.7 times the translation rate of the furnace. The increase of the growth rate may be related to the increase in solidified fraction of the melt. In the case of the unseeded growth, the initial growth rate was ten to forty times the translation rate of the furnace but rapidly decreased to about four times that with the progress of solidification. Thus, it is thought that the growth in initial stage proceeds at a high speed independently of the translation rate of the furnace, resulting in a high growth rate compared to the seeded process.

View full abstract