Structure and Viscosity of CaO–Al₂O₃–B₂O₃ Based Mould Fluxes with Varying CaO/Al₂O₃ Mass Ratios

Abstract

The effect of CaO/Al 2 O 3 ratio on the structure of CaO-Al 2 O 3-B 2 O 3 based glassy mould fluxes was investigated by employing 27 Al and 11 B Triple Quantum Magic-angle spinning nuclear magnetic resonance (3QMAS-NMR) and Raman spectroscopy. 27 Al and 11 B 3QMAS-NMR spectrums showed that Al 3 + mainly forms [AlO 4 ] as a network former and B 3 + mainly forms [BO 3 ] groups in CaO-Al 2 O 3-B 2 O 3 based glasses. Raman spectrum showed existences of different [AlO 4 ] structure units and BO 3 pyro-borate units. In addition, deconvolution results on Raman spectrums indicate that the degree of polymerization of aluminate network in CaO-Al 2 O 3-B 2 O 3 based glasses decreases with the increase of CaO/Al 2 O 3 ratio. The effect of CaO/Al 2 O 3 ratio on viscosity of CaO-Al 2 O 3-B 2 O 3 based glassy mould fluxes was investigated by employing the rotating-cylinder method. The viscosity decreases with increasing CaO/Al 2 O 3 ratio in CaO-Al 2 O 3-B 2 O 3 based mould flux. Correlation between viscosity and structural information of investigated mould fluxes was explored. KEY WORDS: structure; viscosity; 3QMAS-NMR; Raman spectroscopy; CaO-Al 2 O 3-B 2 O 3 based mould flux.

Structure and viscosity of CaO–Al2O3–B2O3–BaO slags with varying mass ratio of BaO to CaO

“…Figure 5 shows the Raman spectra of glassy samples investigated in the present work. The experimentally observed Raman spectra are similar to the previous Raman investigation results on CaO–Al 2 O 3 –B 2 O 3 , 23,37 CaO–Al 2 O 3 –B 2 O 3 –Na 2 O, 38 and CaO–Al 2 O 3 –B 2 O 3 –Li 2 O–Na 2 O 39 systems. The strong Raman bands around 550 cm −1 should be attributed to the transverse motion of bridging oxygen within Al IV –O–Al IV linkages 34,40,41 .…”

“…The strong Raman bands around 550 cm −1 should be attributed to the transverse motion of bridging oxygen within Al IV –O–Al IV linkages 34,40,41 . A small shoulder of 550 cm −1 band can be found at around 630 cm −1 , which can be attributed to the transverse motion of bridging oxygen within Al IV –O–B III linkages 38,39 . It can be speculated that parts of T 1 species in NMR spectra exist in the form of Al IV –O–B III linkages.…”

“…Therefore, the decrease in the area ratio of higher‐frequency band at 780 cm −1 to low‐frequency band at 550 cm −1 reflects the possible decrease of NBOs. The strong bond at around 920 cm −1 is frequently observed in some glassy aluminoborate slag with high concentration of network‐modifying oxides 37,39 . According to Raman study on borate glasses, this band can be assigned to be the vibration of orthoborate (BO 3 ) structural units 43–45 .…”

Viscosity of Na–Si–O–N–F Melts: Mixing Effect of Oxygen, Nitrogen and Fluorine

“…。しかしながら，実際のモールドフラック スは様々な成分を含む多成分系であり，最近では，三成分 系以上の多成分系を対象とした測定が進められている [6][7][8] 。 また，モールドフラックスには粘度や結晶化挙動の制御の ため，多くの場合，酸化物成分(例：CaO，Na 2 O，K 2 O)だ けでなく，フッ化物(例：CaF 2 ，NaF)も添加されることが 多い [9][10][11][12][13][14] 。 融体の粘度や構造に及ぼすフッ化物成分添加の影響解明 は，高温冶金学の研究分野において工業的にも学術的にも 重要な課題であり，多数の報告がなされている 15,16) 。融体 中でのフッ化物イオンの役割を融体の陽イオン組成変化の 影響から独立して理解するため，CaO と CaF 2 のモル比を変 化させた際の粘度変化を議論している報告がいくつか存 在する [17][18][19] 。最近では，モールドフラックスの粘度やレオ ロジー挙動を変化させる添加剤として窒化ケイ素(Si 3 N 4 ) が検討されており，窒化ケイ素を添加したオキシナイトラ イド融体の一部では非ニュートン流体としての挙動が報 告されている [20][21][22] 。一方で，オキシナイトライド融体にお ける非ニュートン性の発現機構は不明である。窒化ケイ素 は，ガラス材料の特性改善のための添加剤としても用いら れており 23) ，ガラス科学分野では陽イオンの組成比を一定 とした際の陰イオン組成(酸化物イオンおよび窒化物イオ ンの構成比)がガラスの特性に及ぼす影響が調査されてい る 24) 。この組成設計のコンセプトは，酸化物イオン，フッ 化物イオンおよび窒化物イオンのそれぞれが粘度に与える 影響を明らかにするのに有用である。Hanfi ら 25 6. Parameters obtained by the Gaussian fit to the 29 Si MAS NMR spectra.…”

Effects of BaO on the Viscosity and Structure of a New Fluorine-Free CaO-Al2O3-TiO2-Based Mold Flux for High Titanium Steel

“…Additionally, the surface quality of the strand is damaged because of the deterioration of the physicochemical properties of the mold flux. [8] The equation of the slag-steel reaction in this case is as follows:…”