Deoxidation of Ti Melt by Newly Developed Two-Step Plasma Arc Melting Process Using Hydrogen
- PDF / 530,600 Bytes
- 6 Pages / 593.972 x 792 pts Page_size
- 10 Downloads / 168 Views
nd its alloys possess excellent properties such as high specific strength, corrosion resistance, and biocompatibility.[1] Moreover, Ti is the fourth most abundant structural metal in the Earth’s crust.[1] However, the global productions of Ti sponge and wrought Ti and its alloys are limited, with production in 2016 around 190,000 and 140,000 tons, respectively,[2] due to the high cost associated with processing.[3] Ti ore must be reduced to metallic Ti (Ti sponge) by the Kroll process; reportedly, this accounts for 1/3 of the cost to produce Ti parts.[4] It is difficult to use low-cost raw materials, such as off-grade Ti sponge and low-grade Ti scraps in the melting process for producing Ti parts due to difficulty of removing impurities.[5] Oxygen is a main impurity in these low-cost raw materials; therefore, the ability to deoxidize Ti in the melting process would enable one to lower the cost of Ti parts through the utilization of low-cost raw materials, such as through recycling scrap metal.
MASAHITO WATANABE, FUMIYA SATO, RAIKI ABE, KYOSUKE UEDA, and TAKAYUKI NARUSHIMA are with the Department of Materials Processing, Tohoku University, Sendai 9808579, Japan. Contact e-mail: [email protected] DAISUKE MATSUWAKA and FUMIAKI KUDO are with the Materials Research Laboratory, Kobe Steel LTD, Kobe 651-2271, Japan. Manuscript submitted December 18, 2018. Article published online May 28, 2019. METALLURGICAL AND MATERIALS TRANSACTIONS B
Takeda and Okabe[6] reviewed research on the refining process for Ti scraps. The removal of oxygen was reported in Ti-Al alloy melt using electron-beam melting by adding excess Al[7] and in Ti-6Al-4V alloy melt using pressure electroslag remelting by adding CaF2 flux and metallic Ca[8,9]; however, deoxidation of unalloyed Ti melt has not been reported. Tsukihashi et al. reported the thermodynamic effect on oxygen content from adding Ca[10] and Y[11] to Ti melts, and the lowest oxygen contents using Ca and Y resulted in 0.72 and 0.24 mass pct, respectively. Another possible deoxidation process for Ti melt is hydrogen plasma arc melting. Mimura et al.[12] reported the removal of metallic elements from a Ti melt using hydrogen plasma arc melting, but did not mention oxygen present in the Ti melt. The decrease in oxygen content of Ti melts by arc melting or plasma arc melting using hydrogen was previously reported.[13,14] However, there have been no reports on the reproducibility of oxygen removal from Ti melts through these processes and the process for removing oxygen from Ti melts has not been established. Herein, a new two-step plasma arc melting process for oxygen removal from Ti melts, comprising Ar-H2 plasma arc melting (first step) and subsequent Ar plasma arc melting (second step), is proposed and the change in the oxygen content of Ti melts is reported. Ti alloy containing 1.5 mass pct O (Ti-1.5 mass pct O) for melting experiments was prepared by non-consumable electrode Ar arc melting, using commercially pure Ti plates and TiO2 powder (> 99.5 mass pct) as raw materials. The oxygen co
Data Loading...
