Titanium and titanium alloy melting crucible, the invention relates to titanium and titanium alloy melting crucible. The crucible comprises a shell, a boron nitride lining and a barrier layer, which is coated with the boron nitride lining and the barrier layer is attached to the inner surface of the boron nitride lining in contact with titanium and titanium alloy liquid. The crucible of the invention does not react with titanium, does not stick, has good fluidity, large volume, low cost, easy maintenance and long service life; In particular, due to the existence of the barrier layer, effectively reduce boron and nitrogen increase, the boron content or nitrogen content of titanium and titanium alloy after smelting can be controlled below 100ppm, effectively improve the quality of titanium alloy.
Due to the high melting point and chemical properties of titanium is very active, melting, liquid titanium can almost react with all crucible refractory materials such as zirconia, magnesium oxide, silicon oxide and alumina, therefore, leading to its melting can not use conventional refractory crucible manufacturing vacuum induction melting. At present, titanium and titanium alloys are melted by vacuum consumable electrode arc shell furnace and forced water-cooled copper crucible. In the vacuum arc shell furnace, a thin layer of "shell" is solidified on the wall of the copper crucible to protect the titanium liquid from contamination by the crucible material and heat insulation, so as to form a molten pool in the crucible. Due to the rapid cooling of water-cooled copper crucible and the formation of coagulation shell, the temperature field of titanium liquid was not uniform, and the titanium alloy kept in liquid state for a short time, the composition of titanium alloy castings was not uniform after casting. For example, the phase transition point of Ti-Ni shape memory alloy is very sensitive to the composition. Compared with vacuum induction furnace, the melting of titanium alloy consumes 40 ~ 60kW /kg of power. In order to solve the above problems, it has been proposed to use calcium oxide as crucible for melting titanium and titanium alloy. But calcium oxide is difficult to be sintered, and the calcium oxide crucible is easy to hydrolyze under air. In addition, the oxygen content of titanium alloy melted by calcium oxide crucible will increase, affecting the performance of titanium alloy.
Using boron nitride and an appropriate amount of flux as raw materials, the crucible blank is pressed by cold isostatic pressing, and sintered at 1800℃ for 1 hour, the crucible finished products can be smelted, and the laboratory scale application has achieved good results, has no reaction with titanium at high temperature, does not bond with the alloy; The advantages of low energy consumption, uniform composition of the alloy after smelting and pouring, stable performance. But the public patent technology, due to the use of boron nitride proper flux by cold isostatic pressing sintering after blocking forming manufacturing overall technical scheme of the crucible, unable to meet the requirements of industrial production, because the industrialized production of the melting pot volume is big.
