{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,17]],"date-time":"2026-06-17T02:52:51Z","timestamp":1781664771925,"version":"3.54.5"},"reference-count":38,"publisher":"MDPI AG","issue":"12","license":[{"start":{"date-parts":[[2026,6,17]],"date-time":"2026-06-17T00:00:00Z","timestamp":1781654400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100008238","name":"Natural Science Foundation of Hebei Province","doi-asserted-by":"publisher","award":["E2024209062"],"award-info":[{"award-number":["E2024209062"]}],"id":[{"id":"10.13039\/501100008238","id-type":"DOI","asserted-by":"publisher"}]},{"name":"Tangshan Science and Technology Plan Funding Project","award":["24130206C"],"award-info":[{"award-number":["24130206C"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Materials"],"abstract":"<jats:p>During the continuous casting of high-titanium steel, traditional fluorine-containing mold fluxes are prone to causing fluoride contamination, equipment corrosion, and intensified slag\u2013metal interface reactions. There is an urgent need to develop highly adaptable fluorine-free mold flux systems. In this study, titanium-containing blast furnace slag was used as the primary base material, while borax, soda ash, and witherite were selected as fluoride-substituting mineral raw materials. The effects of these mineral raw materials on the melting properties, crystallization behavior, crystalline phases, and microstructure of fluorine-free mold fluxes were systematically investigated, and an optimized mold flux design suitable for continuous casting of high-titanium steel was further developed. The results indicate that borax significantly reduces the melting temperature and viscosity and markedly suppresses the growth of crystalline phases such as calcium borosilicate, nepheline, and perovskite by weakening the polymerization degree of the silicate network, thereby substantially decreasing the crystallization ability of the mold flux. Soda ash primarily acts as a strong fluxing and network-depolymerizing agent, promoting the formation of low-polymerized structural units. It also enhances the tendency toward ordered atomic arrangement, thereby markedly increasing nepheline precipitation and the overall crystallization ratio. Witherite exerts a relatively mild effect on slag structure and phase evolution; its moderate addition helps synergistically reduce the melting point, viscosity, and crystallization ratio, thereby supporting performance stability. The optimized fluorine-free mold flux, designed on the basis of these findings, maintains a suitable initial crystallization temperature and critical crystallization cooling rate while exhibiting lower melting temperature, viscosity, and crystallization ratio than conventional fluorine-bearing flux. The findings establish a theoretical basis for designing eco-friendly mold fluxes suitable for high-titanium steel and for enhancing billet quality.<\/jats:p>","DOI":"10.3390\/ma19122600","type":"journal-article","created":{"date-parts":[[2026,6,17]],"date-time":"2026-06-17T01:58:38Z","timestamp":1781661518000},"page":"2600","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Effects of Mineral Raw Materials on Melting\u2013Crystallization Properties and Microstructure of Fluorine-Free Mold Flux for High-Titanium Steel Continuous Casting"],"prefix":"10.3390","volume":"19","author":[{"ORCID":"https:\/\/orcid.org\/0009-0002-8017-8935","authenticated-orcid":false,"given":"Di","family":"Zhang","sequence":"first","affiliation":[{"name":"College of Mining Engineering, North China University of Science and Technology, Tangshan 063210, China"},{"name":"Collaborative Innovation Center of Green Development and Ecological Restoration of Mineral Resources, Tangshan 063210, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Xiuli","family":"Han","sequence":"additional","affiliation":[{"name":"College of Mining Engineering, North China University of Science and Technology, Tangshan 063210, China"},{"name":"Collaborative Innovation Center of Green Development and Ecological Restoration of Mineral Resources, Tangshan 063210, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9966-4058","authenticated-orcid":false,"given":"Lei","family":"Liu","sequence":"additional","affiliation":[{"name":"College of Mining Engineering, North China University of Science and Technology, Tangshan 063210, China"},{"name":"Collaborative Innovation Center of Green Development and Ecological Restoration of Mineral Resources, Tangshan 063210, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ziyao","family":"Liu","sequence":"additional","affiliation":[{"name":"College of Metallurgy and Energy, North China University of Science and Technology, Tangshan 063210, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yue","family":"Yang","sequence":"additional","affiliation":[{"name":"College of Mining Engineering, North China University of Science and Technology, Tangshan 063210, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Lei","family":"Wu","sequence":"additional","affiliation":[{"name":"College of Mining Engineering, North China University of Science and Technology, Tangshan 063210, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ziyi","family":"Zhang","sequence":"additional","affiliation":[{"name":"College of Mining Engineering, North China University of Science and Technology, Tangshan 063210, China"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,6,17]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"645","DOI":"10.1007\/s12613-021-2399-7","article-title":"Titanium microalloying of steel: A review of its effects on processing, microstructure and mechanical properties","volume":"29","author":"Wang","year":"2022","journal-title":"Int. J. Miner. Metall. Mater."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"1926","DOI":"10.1016\/j.jmrt.2025.01.176","article-title":"Investigation of the microstructure and properties on high titanium wear-resistant steels","volume":"35","author":"Yang","year":"2025","journal-title":"J. Mater. Res. Technol."},{"key":"ref_3","doi-asserted-by":"crossref","unstructured":"Gao, W., Wang, S., Zhang, H., Wang, Q., Liu, H., Yu, H., and Sun, D. (2025). Low-Cost Application Strategies of Marine Titanium Alloys and Ti\/Fe Dissimilar Materials. Metals, 15.","DOI":"10.3390\/met15111205"},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"340","DOI":"10.1016\/j.msea.2016.09.070","article-title":"The effect of manganese content on mechanical properties of high titanium microalloyed steels","volume":"677","author":"Li","year":"2016","journal-title":"Mater. Sci. Eng. A"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"1479","DOI":"10.2355\/isijinternational.43.1479","article-title":"The role of mould fluxes in continuous casting\u2014So simple yet so complex","volume":"43","author":"Mills","year":"2003","journal-title":"ISIJ Int."},{"key":"ref_6","doi-asserted-by":"crossref","unstructured":"Liu, L., Han, X.L., Li, M.D., and Zhang, D. (2022). Influence of Mineralogical Structure of Mold Flux Film on Heat Transfer and Longitudinal Cracks of Slabs. Materials, 15.","DOI":"10.3390\/ma15092980"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"66","DOI":"10.1007\/s11663-007-9110-x","article-title":"A study of the crystallization behavior of a new mold flux used in the casting of transformation-induced-plasticity steels","volume":"39","author":"Wang","year":"2008","journal-title":"Metall. Mater. Trans. B"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"4240","DOI":"10.1007\/s42243-025-01607-0","article-title":"Dynamics of mold flux composition in high-titanium steel continuous casting: Modeling and prediction","volume":"32","author":"Mo","year":"2025","journal-title":"J. Iron Steel Res. Int."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"882","DOI":"10.1016\/j.jmrt.2020.12.106","article-title":"Mixing effect of slag compositions and additives on crystallization of mold flux for high-Ti steel continuous casting","volume":"10","author":"Yan","year":"2020","journal-title":"J. Mater. Res. Technol."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"2000314","DOI":"10.1002\/srin.202000314","article-title":"Effect of TiO2 and TiN on the viscosity, fluidity, and crystallization of fluorine-free mold fluxes for casting Ti-bearing steels","volume":"92","author":"Wang","year":"2021","journal-title":"Steel Res. Int."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"102545","DOI":"10.1016\/j.calphad.2023.102545","article-title":"Effect of TiO2 on viscosity and structure for CaO\u2013SiO2\u2013Al2O3-based mold flux","volume":"81","author":"Geng","year":"2023","journal-title":"Calphad"},{"key":"ref_12","doi-asserted-by":"crossref","unstructured":"Wang, X.J., Jin, H.B., Zhu, L.G., Xu, Y., Liu, R., Piao, Z.L., and Qu, S. (2019). Effect of CaF2 on the viscosity and microstructure of CaO\u2013SiO2\u2013Al2O3 based continuous casting mold flux. Metals, 9.","DOI":"10.3390\/met9080871"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"1766","DOI":"10.1007\/s11663-019-01579-z","article-title":"Effects of fluorine on solidification, viscosity, structure, and heat transfer of CaO\u2013Al2O3-based mold fluxes","volume":"50","author":"Yang","year":"2019","journal-title":"Metall. Mater. Trans. B"},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"441","DOI":"10.2355\/isijinternational.46.441","article-title":"Crystallization of CaO\u2013SiO2\u2013CaF2 slag as a candidate for mold flux","volume":"46","author":"Nakada","year":"2006","journal-title":"ISIJ Int."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"1103","DOI":"10.1007\/s12540-014-6013-7","article-title":"Characteristics of medium carbon steel solidification and mold flux crystallization using the multi-mold simulator","volume":"20","author":"Park","year":"2014","journal-title":"Met. Mater. Int."},{"key":"ref_16","first-page":"1784","article-title":"Qualitative and mechanism research of volatiles in the most commonly used CaO-SiO2-CaF2-Na2O slag during casting process","volume":"53","author":"Zhang","year":"2013","journal-title":"ISIJ Int."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"317","DOI":"10.1007\/s11663-013-9796-x","article-title":"Structurally based assessment of the influence of fluorides on the characteristics of continuous casting powder slags","volume":"44","author":"Schulz","year":"2013","journal-title":"Metall. Mater. Trans. B"},{"key":"ref_18","first-page":"100305","article-title":"Recent advancements in fluoride impact on human health: A critical review","volume":"20","author":"Tiwari","year":"2023","journal-title":"Environ. Sustain. Indic."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"155129","DOI":"10.1016\/j.scitotenv.2022.155129","article-title":"Fluoride toxicity in cropping systems: Mitigation, adaptation strategies and related mechanisms. A review","volume":"833","author":"Makete","year":"2022","journal-title":"Sci. Total Environ."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"27188","DOI":"10.1016\/j.ceramint.2024.05.016","article-title":"Influence of TiO2\/SiO2 and BaO\/CaO ratios on viscosity, crystallization and structure of high-TiO2 mold slags for casting of high-Ti steel","volume":"50","author":"Zhang","year":"2024","journal-title":"Ceram. Int."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"70396","DOI":"10.1111\/jace.70396","article-title":"Kinetics of nonisothermal crystallization of SiO2\u2013TiO2\u2013CaO\u2013BaO\u2013Al2O3-based fluorine-free mold flux for high-Ti steel","volume":"109","author":"Zhang","year":"2025","journal-title":"J. Am. Ceram. Soc."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"35","DOI":"10.1007\/s12613-025-3176-9","article-title":"A critical review of the challenges of developing continuous casting mold fluxes for high-Ti steels","volume":"33","author":"Chen","year":"2026","journal-title":"Int. J. Miner. Metall. Mater."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"1320","DOI":"10.1007\/s12613-023-2621-x","article-title":"Influence of substituting B2O3 with Li2O on the viscosity, structure and crystalline phase of low-reactivity mold flux","volume":"30","author":"Mo","year":"2023","journal-title":"Int. J. Miner. Metall. Mater."},{"key":"ref_24","doi-asserted-by":"crossref","unstructured":"Gu, S., Wen, G., Ding, Z., Tang, P., and Liu, Q. (2018). Effect of Shear Stress on Isothermal Crystallization Behavior of CaO-Al2O3-SiO2-Na2O-CaF2 Slags. Materials, 11.","DOI":"10.3390\/ma11071085"},{"key":"ref_25","doi-asserted-by":"crossref","unstructured":"Zhang, D., Han, X.L., Liu, L., Guo, J.J., Yang, Y., and Wu, L. (2025). Physical Properties of Mold Flux and Mineralogical Characteristics of Flux Film for Low-alloy Peritectic Steel Continuous Casting. Materials, 18.","DOI":"10.20944\/preprints202508.0615.v1"},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"1957","DOI":"10.2355\/isijinternational.ISIJINT-2018-232","article-title":"A review of fluorine-free mold flux development","volume":"58","author":"Wang","year":"2018","journal-title":"ISIJ Int."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"14078","DOI":"10.1016\/j.ceramint.2020.02.208","article-title":"Viscosity and structure evolution of CaO\u2013SiO2-based mold fluxes with involvement of CaO\u2013Al2O3-based tundish fluxes","volume":"46","author":"Yan","year":"2020","journal-title":"Ceram. Int."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"1070","DOI":"10.2355\/isijinternational.ISIJINT-2021-470","article-title":"Effect of B2O3 on ESR Slag Viscosity for Remelting 9CrMoCoB Steel","volume":"62","author":"Geng","year":"2022","journal-title":"ISIJ Int."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"27311","DOI":"10.1016\/j.ceramint.2023.05.286","article-title":"Influence of BaO and MgO on viscosity, crystalline phase, and structure of CaO-Al2O3-10%SiO2-20%CaF2-based system","volume":"49","author":"Mo","year":"2023","journal-title":"Ceram. Int."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"348","DOI":"10.2355\/isijinternational.38.348","article-title":"Development of Double and Single Hot Thermocouple Technique for in Situ Observation and Measurement of Mold Slag Crystallization","volume":"38","author":"Kashiwaya","year":"1998","journal-title":"ISIJ Int."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"322","DOI":"10.1016\/S1006-706X(16)30052-8","article-title":"Analysis of crystallization behavior of mold fluxes containing TiO2 using single hot thermocouple technique","volume":"23","author":"Lei","year":"2016","journal-title":"J. Iron Steel Res. Int."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"2100193","DOI":"10.1002\/srin.202100193","article-title":"Effect of Na2O on properties, structure, and crystallization of CaO-Al2O3-based mold fluxes","volume":"93","author":"Wang","year":"2022","journal-title":"Steel Res. Int."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"125403","DOI":"10.1016\/j.matchemphys.2021.125403","article-title":"Effect of MgO on solidification and crystallization properties of ultrahigh-basicity mold flux","volume":"276","author":"Chen","year":"2022","journal-title":"Mater. Chem. Phys."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"728","DOI":"10.1016\/j.matdes.2015.06.054","article-title":"A new method for estimating the isothermal devitrification and crystallization of mold powder slags from non-isothermal DSC data","volume":"83","author":"Maldonado","year":"2015","journal-title":"Mater. Des."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"606","DOI":"10.1007\/s11663-013-9803-2","article-title":"Crystallization kinetics and structure of mold fluxes with SiO2 being substituted by TiO2 for casting of titanium-stabilized stainless steel","volume":"44","author":"Wang","year":"2013","journal-title":"Metall. Mater. Trans. B"},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"6633","DOI":"10.1016\/j.ceramint.2025.12.415","article-title":"Viscosity, structure, and crystallization behavior of CaO-SiO2-CeO2-La2O3-P2O5-CaF2 slag with different Al2O3 contents","volume":"52","author":"Zhao","year":"2026","journal-title":"Ceram. Int."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"51","DOI":"10.2355\/isijinternational.ISIJINT-2019-234","article-title":"Structure and viscosity of CaO-Al2O3-B2O3 based mould fluxes with varying CaO\/Al2O3 ratio","volume":"60","author":"Jiang","year":"2020","journal-title":"ISIJ Int."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"452","DOI":"10.1016\/j.jenvman.2018.06.068","article-title":"Hazardous aluminum dross characterization and recycling strategies: A critical review","volume":"223","author":"Mahinroosta","year":"2018","journal-title":"J. Environ. 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