Graphite electrode in the use of electric arc furnace steelmaking
As a Synthetic Graphite Electrode Factory, today I will share the five stages of EAF steelmaking, which can be divided into raw material collection, preparation before smelting, melting period, oxidation period and reduction period.
Collection of raw materials
Scrap is the main material for electric arc furnace steelmaking. The quality of scrap directly affects the quality and cost of steel and the productivity of Graphite Electrode. Therefore, there are several requirements for scrap steel:
(1) The surface of the scrap steel should be cleaned with less rust. The dirt and other impurities in the scrap steel will reduce the electrical conductivity of the charge, prolong the melting time, and also affect the dephosphorization effect during the oxidation period and erode the lining. When scrap steel is severely corroded or oily, it will reduce the yield of steel and alloying elements and increase the hydrogen content in steel.
(2) Non-ferrous metals such as lead, tin, arsenic, zinc and copper shall not be mixed in scrap steel. Lead has a high density, a low melting point, is insoluble in molten steel, and is easily deposited in the gap of the furnace bottom to cause a steel leakage accident. Tin, arsenic and copper are easy to cause hot brittleness of steel.
(3) There should be no sealed containers, flammable, explosive materials and toxic substances in the scrap steel to ensure safe production.
(4) The chemical composition of scrap steel should be clear, and the sulfur and phosphorus content should not be too high.
(5) The outer dimensions of scrap steel should not be too large (the cross-sectional area should not exceed 150mm × 150mm, and the maximum length should not exceed 350mm). Pig iron is generally used in electric arc furnace steelmaking to increase the carbon content of the charge, usually not more than 30% of the charge.
Preparation before smelting
Ingredients are an indispensable component of the graphite electrode steelmaking process. Whether the ingredients are reasonably related to whether the steelmaker can normally carry out the smelting operation according to the process requirements. Reasonable ingredients can shorten the smelting time. Pay attention to the ingredients: First, the batching calculation must be carried out correctly and the charge amount of the charge should be accurately weighed. Second, the size of the charge should be proportioned to achieve the purpose of good loading and quickening. Third, all types of charge should be used in accordance with the quality requirements of steel and smelting methods. Fourth, the ingredients must meet the process requirements.
In the electric arc furnace steelmaking process, the melting period is called from the start of energization until the charge is completely melted. The melting period accounts for about half of the total smelting time, and the power consumption accounts for about 2/3 of the total electricity consumption.
The task of the melting period is to quickly melt and heat the charge with minimum power consumption while ensuring the life of the furnace, and to make the slag during the burning period to stabilize the arc and prevent inhalation and early dephosphorization.
(1) The arc initiation phase. When the arc is energized, the furnace is filled with the charge, and the arc is close to the top of the furnace. If the input power is too large, the top of the furnace is easily burnt out, so the intermediate voltage and the rated power of the input transformer are generally selected about 2/3.
(2) The stage of penetration. At this stage, the arc is completely surrounded by the charge, and almost all of the heat is absorbed by the charge, and the lining is not burned. Therefore, the maximum power is used, and the general well-dressing time is about 20 minutes, which accounts for about 1/4 of the total melting time.
(3) The rising stage of the graphite electrode. After the graphite electrode is “welld through”, the molten pool is formed at the bottom of the furnace, and the lime at the bottom of the furnace and some elements are oxidized, so that a layer of molten slag is formed on the molten steel surface, and the surrounding charge continues to be melted by radiant heat, and the molten steel is increased. As the liquid level rises, the graphite electrode gradually rises. At this stage, the maximum power is still used to deliver electrical energy, which takes about 1/2 of the total melting time.
(4) Melting the end of the class. After the charge is melted by 3/4 or more, the arc can no longer be shielded by the charge. The high temperature zone under the three graphite electrodes has been connected into one piece. At this time, if the maximum power is supplied for a long time, the arc will strongly damage the furnace cover and the furnace wall.
Our company Graphite Electrode Joint For Sale, welcome everyone to consult.