JPS6129092A - Arc electric furnace electrode - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] (Field of industrial use) The present invention relates to an electrode for an electric arc furnace.

(Prior Art) An electric arc furnace generates an arc between a graphite electrode and scrap steel or molten steel, and uses the heat of the arc to melt or refine the steel. Since it is easy to remove phosphorus, sulfur, and W1 elements, it has the same characteristics as high-grade steel refining furnaces, and has developed as the main steelmaking furnace of the modern steel industry.

As an example, to give an overview of a commonly used electric arc furnace, an electric furnace consists of a combination of a furnace body and electrical equipment.The furnace body has a furnace lid, and the inside of both is lined with refractory material. has been done.

The furnace body has a tapping port and tapping port for discharging molten steel into a ladle, and an operating port for inputting materials necessary for refining, scraping out slag, and collecting samples for analysis. The furnace lid has an insertion hole into which the electrode is inserted. Electrical equipment consists of a transformer and a power supply section that connects the electrodes and the transformer. The side walls of the furnace shell are cylindrical and the bottom is dish-shaped and made of thick steel plate. A water cooling box is installed at the operation opening, tap opening, interface between the furnace body and the furnace lid, etc. so as to provide water cooling. Inside the furnace body, both the side walls and the bottom of the furnace are made of refractory bricks, and the bottom of the furnace is covered with a basic or acidic refractory material on top of the bricks to withstand harsh steelmaking conditions. There is an operating opening on the side wall and a tapping opening on the opposite side. To charge raw materials, the furnace lid is lifted up, and raw materials are charged from the top of the furnace using packets. Is the electrode that guides electricity into the furnace, generates an arc, and melts the raw materials made of stone? [fl coke, made by using pitch coke as the main raw material, molding it with pitch tar as a binder, and after firing, heating it in an electric resistance furnace to 2500 tr to graphitize it.

The graphite electrodes are cylindrical in shape, threaded at both ends, and attached so that they can be connected using fittings. 11L
The electrode is gripped by an electrode gripper, and its load is supported by a support in the gripped state. The electrode gripper grips the electrode and also holds 'F1! It transmits current to the poles, and is water-cooled to prevent thermal effects.

(Problem to be solved by the invention) In recent years, electric arc furnaces have tended to be operated at high voltage and high power in order to increase efficiency, and in addition to electric arc heating, cutting and melting of scrap using oxygen gas has become more common. , auxiliary heating using fuels such as heavy oil, and oxidation refining in which oxygen gas is directly injected into molten steel using a lance have begun to be carried out. In oxidation refining, harmful phosphorus and other impurities are removed by blowing oxygen gas into molten steel, and non-metallic inclusions float to the surface as slag due to the intense boiling action caused by the reaction between carbon and oxygen gas. Hydrogen gas, nitrogen gas, etc. can be removed. However, these changes in operating conditions will increase the degree of oxidation in the furnace atmosphere, and under these conditions, the degree of wear of the graphite electrode will be significant.
~〈It will increase. In other words, since arc type electric furnaces are operated at high temperatures, if the atmosphere inside the furnace becomes an oxidizing atmosphere, graphite 1! The entire electrode is oxidized and consumed, which is a factor that increases manufacturing costs.

According to operational experience, oxidation accounts for more than 60% of the total wear due to electrode operation. In other words, oxidative consumption that occurs on the side of the electrode (also called side loss)
is greater than the wear that occurs at the tip of the electrode (also called terminal wear). Conventionally, attempts have been made to protect the electrodes from oxidation and extend the life of the electrodes as a method of preventing or reducing the wear and tear of the electrodes under such circumstances, but no essential oxidation protection measure has been obtained.

(Object and structure of the present invention) The present invention eliminates the drawbacks and problems of the prior art.

This book aims to provide an electrode for an electric arc furnace that can be replaced, and the above object can be achieved by providing the electrode for an electric arc furnace as described in the claims. That is, the present invention has an electrode formed by a non-consumable upper steel structure and graphite threadedly connected to a lower part of the steel structure, water cooling means is provided inside the steel structure, and □ the steel structure The present invention relates to an electrode for an electric arc furnace, the outer surface of which is protected by thermal spray coating of the surface with a tungsten film.

The electrode for arc type electric furnace of the present invention will be explained in detail below.

An electric furnace using the electric furnace electrode of the present invention is the same as a conventional electric furnace. In other words, an electric furnace has a furnace body and a furnace lid, each of which is lined with a refractory material, and the furnace body has a tap port and a tap port for taking out molten steel, and is used to input materials necessary for refining and scrape out slag. There is an opening for the operation, and there is an electrode insertion hole in the furnace lid, into which the electrode is inserted.

The figure is an explanatory view showing a longitudinal cross section of the electrode for arc type electric furnace of the present invention. As shown in the figure, the electrode consists of a consumable part 2 made of artificial graphite and a non-consumable part L made of steel, and the consumable part 2 and the non-consumable part 1 are integrated with a screw. .

The artificial graphite in the consumable part 2 is formed using petroleum coke as the main raw material and pitch tar as a binder, and is heated in an electric furnace for 25 minutes after firing.
It is manufactured by graphitizing it by heating it to 0.00C, and the end is threaded so that it can be connected to the non-consumable part 1. By using the consumable part 2 as an electrode,
When it wears out and becomes short, remove it from the threaded part and replace it with a new graphite consumable part 2. The non-consumable part 1 is made of steel and has a water cooling jacket 3 inside, so that the electrodes are cooled through cooling water. Cooling the electrodes can reduce wear due to oxidation of the electrodes when exposed to oxidizing atmospheres at high temperatures. In addition, it is possible to prevent the splash from melting scrap and the splash from oxygen blowing refining from adhering to the electrode and causing it to wear out.Since the splash does not adhere to the electrode, the electrode is held securely and stably by the electrode holder. becomes possible.

The outer surface of the steel material of the non-consumable part 1 is further thermally sprayed with an oxidation-resistant coating. For example, if tungsten is coated on the steel surface of the non-consumable part 1 to a thickness of 0.1 to 0.811III by a method such as a plasma jet method, the life of the non-consumable part 1 of the electrode can be dramatically extended. . The tungsten coating layer has a very high melting point of 3.4007:', is difficult to wet with molten metal, and has a slow oxidation rate compared to other metals. If the thickness of the coating is less than 0.1, oxidation may progress through the pores present in the sprayed coating, and if it is thicker than 0,8, the coating may peel. As for 0.1-0.
8 meters is preferred. Note that oxidation-resistant metals other than tungsten, such as molybdenum, may also be used, and oxidation-resistant alloys may also be used.

(Effects of the Invention) As explained above, the electrode for arc type electric furnace of the present invention is composed of a non-consumable upper steel structure part and a consumable graphite part, and the upper steel structure part is internally It has a water cooling jacket and the outer surface is coated with an oxidation-resistant film, so there is less oxidative wear and tear, and when the lower graphite part wears out due to use, it can be replaced immediately, so the electrode Manufacturing costs can be significantly reduced.

Next, the present invention will be explained with reference to examples.

EXAMPLE The purpose of this study was to compare the manufacturing costs when a steel ingot of the same weight is melted using a normal graphite electrode and the electrode of the present invention in an electric arc furnace for steelmaking using an electrode with a diameter of 14 inches. When using the electrode of the present invention, the amount of electrode consumption is reduced by 27%,
The cost of manufacturing steel could be significantly reduced.

[Brief explanation of the drawing]

The figure is an explanatory view showing a longitudinal cross section of the electrode for arc type electric furnace of the present invention. 1... Non-consumable part, 2... Consumable part, 3... Water cooling jacket, 4... Oxidation-resistant thermal spray coating layer.

Claims (1)

[Claims] 1. In an electrode for an electric arc furnace; the electrode comprises a non-consumable, water-cooled upper electrode made of metal and a consumable lower electrode made of graphite that is screwed into the lower end of the upper electrode; An electrode for an electric arc furnace, wherein the upper electrode is held by a holding device so as to be able to move up and down. 2. The electrode for an electric arc furnace according to claim 1, wherein the surface of the non-consumable, water-cooled metal upper electrode is coated with a sprayed layer of tungsten.