The major component of fused potassium silicate (FPS) fertilizers, produced from steel-making slag, was studied. FPS compounds have received considerable attention as slow-release potassium fertilizers beneficial for crops. This major component was found to be a single phase compound, K2Ca2Si2O7, which had not been previously identified. In order to confirm the presence of the newly identified compound, we synthesized a potassium calcium silicate mixture, K2O-2CaO-2SiO(2), by fusing a mixture of K2CO3, CaCO3, and SiO2. The X-ray diffraction patterns of the synthesized K2O-2CaO-2SiO(2) were largely consistent with those of FPS fertilizer, and Energy Dispersive X-ray Spectroscopy indicated that this compound was a single phase with a K:Ca:Si molar ratio of 1:1:1. It is concluded that the major component of FPS fertilizer is a compound of K2O-2CaO-2SiO(2), newly identified as K2Ca2Si2O7. FPS fertilizers exhibit the characteristic, controlled by their K2Ca2Si2O7 content, of slowly releasing potassium into water and soil.

Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, USA, July 29 – August 2, 2012.

The galvannealing behaviors of Ti-IF steel and P-added steel are affected by the application of sulfur before annealing. For this study of those effects, the amounts of sulfur on the steel surface were 5-500 mg/m2.In each steel, application of 500 mg/m2 of sulfur increased the number of ζ crystals, which were densely and randomly distributed. Furthermore, the galvannealing rate of each steel was higher than in steels without sulfur application.The ferrite grains of the annealed surface with 500 mg/m2 of sulfur were finer than those with less than 50 mg/m2 of sulfur. Moreover, small (Fe,Mn) S particles formed along the fine grain boundaries. The thickness of the area consisting of those fine grains, which were as large as 2 μm, was approximately 0.8 μm.The (Fe,Mn) S particles were formed as the steel was annealed after application of sulfur on the surface. The recrystallized ferrite grains on the surface were fine because the particles suppressed the grain growth. In galvannealing of the steel, the fine ferrite grain boundaries are the outburst reaction sites: they increased galvannealing sites and raised the galvannealing rate. Results show that the galvannealing rates of steels with added Ti-IF and P were almost equal.

A mechanism of improvement in the corrosion resistance of ferritic stainless steels by Cu addition was studied by field exposure tests. XI'S analysis of passive films and electrochemical evaluation.Corrosion area ratio alter a I-month field exposure test was the smallest with 0.4%Cu addition among 21%Cr-0 similar to 2.0%Cu stainless steels. and chromium concentration of the passive films was higher with the Cu-bearing stainless steels than the Cu-free stainless steel. After an 18 month field exposure test. chromium concentration of the passive films of high Cr and Cu bearing stainless steels was higher than that of low Cr and Cu bearing stainless steels. This result suggested an existence of a synergistic elect between Cr and Cu.Cu in ferritic stainless steels accelerates cathodic reaction and reduces anodic reaction when the steels dissolve in the active potential region. Therefore. Cu in the steels increases the open circuit potential at the passivation stage, and the increase of open circuit potential promotes the enrichment of chromium concentration of passive films on the Cu-bearing ferritic stainless steels. The cycle of dissolution and passivation strengthens the passive films on the Cu-bearing stainless steels.On the other hand. the 1-month field exposure test revealed corrosion area ratio of stainless steels bearing more than 1% Cu was larger than that of a 0.4%Cu-bearinu stainless steel. Stainless steels containing more than 1% Cu contain epsilon-Cu in matrix. It is considered that precipitation of e-Cu deteriorate the corrosion resistance of these stainless steels.

鋼板の表面および表面の処理層中に存在する元素の化学結合状態を解析する手法として,放射光を用いた X 線光電子分光および X 線吸収端微細構造法を紹介する.これらの手法は,非破壊での深さ方向分析,結合状態の識別等の点で,既存の表面分析法では取得困難な情報を得ることができる.本解説では,手法の特徴と鉄鋼材料への適用例を述べる.

The galvanizing reaction is retarded when phosphorus-added steel is used as a substrate. We have found that both the galvanizing and the galvannealing reactions are highly promoted when thiourea solution is coated on the cold-rolled steel surface before the annealing process. Both a plan-view and cross-sectional characterization of thiourea-coated steel was performed using low-voltage scanning electron microscopy and a focused ion beam. A fine grain structure is formed in the surface region of approximately 1 microm in thickness. In this region, (Mn, Fe)S particles are formed by the reaction between sulphur from thiourea and manganese from steel. These (Mn, Fe)S particles have a pinning effect on the cold-rolled steel grains and greatly retard recrystallization when the steel is annealed. It is concluded that the promotion of the galvannealing reaction is due to the increased diffusion paths of zinc and iron materialized by the fine grain structure of the thiourea-coated steel.

Chromate coatings on Zn or Zn alloy coated steel sheets often include silica for the aim to improve corrosion resistance. In the case of dry-in-place chromate coatings containing acrylic resin (hereafter referred to as an organic–inorganic composite coating), an addition of silica, however, did not show an improvement in corrosion resistance. The microstructures of the organic–inorganic composite coatings were observed by transmission electron microscopy (TEM) and the chemical states of Cr were investigated by the total electron yield X-ray absorption near edge structure (TEY-XANES) method. TEM samples were successfully prepared by dry ultramicrotomy preventing water-soluble components in the coatings from dissolving out. TEY-XANES revealed the chemical states of components even in the organic matrix. Using these methods, it was found that the addition of silica changed just the morphology of the chromium compound in the organic–inorganic composite coating but not the chemical state of Cr. This is a reason for the addition of silica being not effective at improving corrosion resistance. The combination of dry ultramicrotomy-TEM and TEY-XANES spectroscopy was proven to be a powerful tool for characterizing organic–inorganic composite coatings.