(1)With high melting point, which is 1668±5℃.
(2) With very high chemical activity, especially great affinity for oxygen, nitrogen, hydrogen, carbon and other interstitial elements, causing great difficulties in the selection of refractory materials and atmosphere in smelting;
(3) Metal material purity is extremely sensitive to its processing and service properties.
Based on the above three characteristics, titanium and titanium alloy ingot melting is carried out by vacuum melting method.The advantages of this melting method are as follows:
(1) Prevent the pollution of metal materials by harmful gases such as oxygen, nitrogen and hydrogen from the atmosphere;
(2) Metal pollution caused by non-metallic refractory materials is eliminated;
(3)Provide favorable thermodynamic and kinetic conditions for the purification of metal materials;
(4) Sequential solidification casting method is conducive to the floating of non-volatile insoluble impurities and can improve the structure of the ingot;
(5)Melting is carried out in a crucible that also serves as a spindle mold, which is convenient to adopt hot top sealing method for feeding and reduce the riser removal rate.
Pressure processing requirements for ingot casting
The ingot is a semi-finished product for making processed materials.The ingot shall meet the following requirements:
(1) Chemical composition and impurity content are qualified and evenly distributed;
(2) Internal tissue is uniform, without specific or individual coarse tissue;
(3) No metallic or non-metallic inclusions;
(4) No internal defects such as porosity, crack, shrinkage cavity, porosity and cold insulation;