Arc melting is an electrothermal metallurgical method that uses electrical energy to generate an arc between electrodes or between electrodes and the melted material to melt metals. Arcs can be generated using either direct current or alternating current. When using alternating current, there will be an instantaneous zero voltage between the two electrodes. In vacuum melting, due to the low gas density between the two electrodes, it is easy to cause the arc to extinguish. Therefore, DC power supply is generally used for vacuum arc melting.
According to different heating methods, arc melting can be divided into two categories: direct heating arc melting and indirect heating arc melting. The main technical and economic indicators of arc melting include melting time, the quantity of solid furnace material melted per unit time (production capacity), unit solid furnace material electricity consumption, refractory materials, electrode consumption, etc.
1、 Direct heating arc melting
The electric arc generated by direct heating arc melting is between the electrode rod and the melted furnace material. The furnace material is directly heated by the electric arc, which is the source of heat for melting. There are two main types of direct heating arc melting: non vacuum direct heating three-phase arc furnace melting method and direct heating vacuum consumable arc furnace melting method.
(1) Non vacuum direct heating three-phase arc melting method. This is a commonly used method in steelmaking. The steelmaking electric arc furnace is the most important type of non vacuum direct heating three-phase electric arc furnace. The electric arc furnace commonly referred to by people refers to this type of furnace. In order to obtain high alloy steel, it is necessary to add alloy components to the steel, adjust the carbon content and other alloy content of the steel, remove harmful impurities such as sulfur, phosphorus, oxygen, nitrogen, and non-metallic inclusions below the specified range of the product. These smelting tasks are most convenient to complete in an electric arc furnace. The atmosphere inside the electric arc furnace can be controlled to be weakly oxidizing or even reducing through slag making. The alloy composition in the electric arc furnace has less burning loss, and the heating process is relatively easy to adjust. Therefore, although arc melting requires a large amount of electrical energy, this method is still used in industry to melt various high-grade alloy steels
(2) Direct heating vacuum arc furnace melting method. It is mainly used to melt active and high melting point metals such as titanium, zirconium, tungsten, molybdenum, tantalum, niobium, and their alloys. It is also used to melt alloy steels such as heat-resistant steel, stainless steel, tool steel, and bearing steel. The metal melted by a direct heating vacuum consumable arc furnace has a decrease in gas and volatile impurity content, and the ingot generally does not have central porosity. The ingot crystallization is more uniform, and the metal properties are improved. The problem with direct heating vacuum consumable arc furnace melting is that it is difficult to adjust the composition of metals (alloys). Although the equipment cost of the furnace is much lower than that of the vacuum induction furnace, it is higher than that of the electric slag furnace, and the smelting cost is also much higher. Vacuum self consuming electric arc furnace was first applied in industrial production in 1955, initially for melting titanium, and later for melting other high melting point metals, active metals, and alloy steels.
2、 Indirect heating arc melting
The arc generated by indirect heating arc melting is between two graphite electrodes, and the furnace material is indirectly heated by the arc. This smelting method is mainly used to melt copper and copper alloys. Indirect heating arc melting is gradually being replaced by other melting methods due to its high noise and poor metal quality.
Post time: Jan-25-2024