Titanium alloy is a high-end, high value-added product in the special steel industry. At present, one of the topics of titanium alloy smelting is to develop a new process to obviously eliminate the defects of various inclusions in the ingot and ensure the uniformity of the chemical composition of the ingot. Conventional vacuum consumable arc melting is used, but the problem of inclusions cannot be completely solved. In recent years, hearth smelting methods have emerged and have been industrialized. There are two main types of methods:
1. Semi-continuous hearth melting with independent heating source.
In this method, after the solid charge is melted, the metal on the route from the smelting zone to the crystallizer remains liquid, and the cold bed furnace effectively separates and removes high specific gravity inclusions through specific gravity difference. It can be divided into plasma cold bed furnace and electron beam cold bed furnace.
Is more effective for removing low-density inclusion electron beam furnace. The obvious advantage of the plasma cold bed furnace smelting system is that it can maintain different steam pressures to obtain alloy components. During the smelting process, there is no obvious loss of easily evaporable elements such as Al, Cr, Mn, etc. At the same time, because of the increased crystallization rate, it can be significantly reduced The β-stabilizing elements are aggregated into the liquid phase, thereby preventing the production of β-spots.
U.S. General Motors titanium alloys have achieved obvious results with this method. In recent years, cold bed furnace smelting technology abroad is an important means to further improve the purity of metals and prevent the inclusion defects of titanium alloy compressor disks for aircraft engines.
2. Condensed shell consumable electrode melting
This type of hearth melting is characterized by a large melting current. The cold metal crucible plays the role of the hearth, and the smelted metal continuously flows into the crucible, and is poured into the casting mold at the end of the smelting.
Because shell smelting is a variant form of hearth smelting, it has a high scouring and impurity removal capability and can remove various inclusion defects. Its comprehensive smelting effect is equivalent to the first type.
Russia ’s Upper Salda Metallurgical United Enterprise used a shell furnace to smelt different titanium alloys. A large number of ingots have proved that shell melting has a strong ability to remove impurities. Under standard operation, no case was caused by inclusions. Metal scrap accident.
Compare the two types of methods. If furnace hearth smelting is used as a means to produce consumable electrodes for subsequent vacuum consumable arc melting, the condensed shell smelting has obvious advantages over hearth furnaces. In the case of the same refining and impurity removal capacity, the initial preparation cost and metal processing cost of the shell smelting are low; the metal smelted before pouring into the ingot is all in the liquid state, which has the potential of making the ingot obtain high chemical uniformity , So as to ensure the uniformity and safety of alloy strengthening. However, the smelting methods and equipment recently introduced in China are mostly based on hearth furnaces. Perhaps the Russian condensate consumable electrode smelting furnace is relatively new to the industry. However, as the two methods of juxtaposition, there should be reasons for their juxtaposition, and interested scientific researchers can study and promote them to China.