弊社鋳造技術関連文献　概要集

1) 石灰を耐火物に用いた2,3の金属間化合物の真空溶解
2) 石灰を耐火物に用いたチタン鋳物の製造
3) クロムの誘導溶解および鋳造
4) 石灰るつぼで溶製したチタン鋳物の内部健全性の改善
5) A New Process of Producing Titanium Alloy Castings
6) チタン鋳物の表面反応層におよぼす鋳型材および粘結剤の影響
7) 石灰るつぼで溶製したチタン鋳物の見かけの凝固収縮率

1) 石灰を耐火物に用いた2,3の金属間化合物の真空溶解

(Vacuum Melting and Casting of Some Intermetallic Compounds with Lime Refractory)

Melting and casting experiments of the intermetallic compounds Ni₃Al, NiTi, and TiAl were carried out under reduced pressure of argon using lime as a crucible and mold material. The crucible and mold were made by hand-tamping reagent grade calcium oxide powder mixed with calcium chloride-ethanol solution and firing at 950 C for 3hrs. Solid investment molds made from fused lime slurry were also tested. Comparative experiments were conducted with commercially available alumina, magnesia, and fused lime crucibles and with ceramic shell investment molds made from a mixture of zircon flour and ethyl-silicate. All heats were prepared by charging electrolytic nickel, aluminum ingot, and sponge titanium directly into an induction furnace. It was confirmed that lime crucibles can be safely used to melt all of these alloys but others are only acceptable for Ni₃Al melt. Lime molds were easy to remove from castings and cast parts had very limited case depth with enough surface finish quality. Castings made with ceramic shell molds showed tendencies to cracking and surface hardening.

2) 石灰を耐火物に用いたチタン鋳物の製造

(Production of Titanium Castings with Lime Refractory)

The suitability of calcined lime as crucible and mold materials for making titanium castings was tested. Crucubles and molds were prepared by handtamping reagent grade calcium oxide powder mixed with an ethanol solution of anhydrous calcium chloride and firing at 950 C for 3hr in air. Some experiments were conducted with investment molds made of lime by the lost wax process. It was confirmed that induction melting of both sponge and scrap titanium was possible in the lime crucible under an argon atmosphere so far as excessive heating and soaking of melts was avoided. The same crucible could be reused beyond 3 melts. Oxygen contents of unalloyed castings were in a range from 0.2 to 0.4 percent. Titanium alloys were produced by directly adding pure metals or mother alloys into the melts. Nominal and analyzed compositions of alloys agreed within 0.5 percent. Unalloyed titanium, Ti-5%Al-2.5%Sn, Ti-6%Al-4%V and Ti-15%V-3%Cr-3%Al-3%Sn alloys were castable with bright surfaces in lime molds. Castings of Ti-0.3%Mo-0.8%Ni, Ti-8%Mn, Ti-10%V-3%Al-2%Fe and Ti-13%V-11%Cr-3%Al alloys had thin layers of adhering lime. A shrinkage factor of about 20/1000 was estimated. In conclusion, the lime is a satisfactory refractory to make castings for non-critical uses where a small amount of oxygen contamination is permissible.

3) クロムの誘導溶解および鋳造

(Induction Melting and Casting of Chromium)

Crucible and mold materials for producing chromium castings were investigated．Electrolyticchromium was induction−melted in alumina，magnesia，andhme crucibles under an argonatmosphere of 50kPa．The tests revealed that thehme crucible made by hand tamping calcinedcalcium oxide powder was superiorin resistance to cracking and meltintrusion．Alumina crucible was attacked by the melt more and magnesia cricible was subjected to thermal shock more than the other ones．Deoxidation and desulfurization down to 40ppm O and l0ppm S were achieved by the addition of about one mass percent of aluminium to the melt in the lime crucible．Nitrogen contents of chromium after melting were the same as those of the chromium charged．Ceramic shell molds made of a slurry of zircon sand and ethyl-silicate reacted vigorously with chromium melt．Good results were obtained by using solid investment molds made of fused lime powder mixed with calcium chloride−ethanol solution．Of the oxides studied，only lime showed promise of success as a crucible and mold material for making chromium castings．

4) 石灰るつぼで溶製したチタン鋳物の内部健全性の改善

(Improvement of the Internal Soundness of Titanium Castings Prepared by Induction Melting in Lime Crucible)

Experimental work was carried out to develop a technique for making titanium castings free from porosity by static molds. Plates, 2cm thick, 6cm wide, 8cm high were vertically cast without risers and used to assess porosity. The soundness was ascertained from a simple visual inspection of a longitudial section through the casting. Castings had extensive gas pores regardless of types of melting stock, e. g. sponge or rolled bar when and poured under reduced pressure of argon. Porosity was also observed in castings made in the copper mold previously heated at 500K in vacuum to exclude the effect of interaction of the metal with the mold and the effect of gases in the mold. The addition of various elements less than 2 mass per cent, bottom gating and control of melting rate were not effective for the prevention of porosity insofar as melting and casting were done under reduced conditions. Soundness was improved by increasing the pressure of argon during melting and casting processes and porosity free castings were obtained under the pressure above 250kPa. Briding of the charge in the crucible could be avoided when melting was conducted under pressurized conditions. Fron these results it was deduced that calcium gas generated by the reaction between lime crucible and titanium melt is one of the causes of porosity in the castings produced by this process and the boiling of calcium is suppressed by the pressure of argon.

5) A New Process of Producing Titanium Alloy Castings

A cost-saving process was developed for producting cast parts of titanium alloys for noncritical applications using crucibles and molds made of lime. Induction melting of sponge and scrap titanium was possible in the lime crucibles under argon atomosphere so for as excessive heating and holding of the melt were avoided. Lime molds were easy to remove from castings and cast parts had very limited case depth with enough surface finish quality. The gas porosity in the castings was reduced effectively by applying pressure of argon during melting of titanium. Casting parts weighing up to 10kg have been successfully produced by the newly developed process.

6) チタン鋳物の表面反応層におよぼす鋳型材および粘結剤の影響

7) 石灰るつぼで溶製したチタン鋳物の見かけの凝固収縮率