JPS591613A - Melting method with arc furnace - Google Patents

Abstract

PURPOSE:To melt the whole scrap in a short time without eroding the refractory material in an arc furnace in the stage of melting the scrap in the arc furnace by rotating the furnace body. CONSTITUTION:Scrap 64 which is a raw material for making steel is charged into an arc furnace, and 3 pieces of graphite electrodes 40 are suspended from above, and the arcs by large electric power are generated between the electrodes and the scrap 64, thereby melting the scrap. The scrap near the three electrodes 40 is first melted in this case, and the scrap 64 between the electrodes remains unmolten. As the scrap near the electrodes melts, the inside wall of the furnace near the molten scrap is heated and the temp. of the cooling water in cooling tanks 50b, 50d, 50f in said position rises. Said temp. is detected with a temp. sensor 56, and is fed to a discrimination circuit 58 which emits a starting signal SD to drive a motor for rotating the furnace body, thereby rotating the furnace body 30 deg. either to the left or right in a horizontal direction. The unmolten scrap is made near the three electrodes and is melted by large electric power. The entire scrap is thus melted in a short time without eroding the inside wall of the furnace.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a melting method in an arc furnace, and in particular to a melting method that can eliminate the limited operation of the power supply acid and obtain high productivity.

Conventionally, in arc furnaces for steelmaking, a plurality of electrode rods are inserted into a container-shaped furnace body approximately parallel to the vertical central axis, and a Nuku-5 tube is inserted into the furnace body. A pair of materials to be melted, such as the following, is melted by an arc. In general, in such melting operations, when high power is supplied to the electrode rod in order to shorten the melting time, the well-known hot nubot is formed and the refractories that make up the furnace wall of the arc furnace are locally damaged. I am only 9 years old. On the other hand, at the beginning of melting, maximum power is applied, and after the Nuclap on the furnace wall near the electrode rod has melted, the voltage is lowered to create a short arc, minimizing the occurrence of hot Nuclap while increasing the melting time. A method to cauterize is already provided.

However, since this conventional method lowers the arc voltage to minimize the occurrence of hot spots, it is not possible to continuously apply maximum power, and it is not necessarily a highly productive melting method. The invention was made against the background of the above circumstances, with the overall purpose of shortening melting time and increasing productivity by maintaining the amount of power supplied without causing local damage to the refractories that make up the furnace wall. The gist of this is that while performing the melting operation of the material to be melted by an arc,
The furnace body and the electrode rod are rotated relative to each other around the vertical center axis of the furnace body, so that the material to be melted can be melted without limiting the electric power supplied to the electrode rod.

In this way, the furnace body and the electrode rod are not rotated relative to each other during melting, so a part of the furnace wall is not continuously exposed to the high temperature area near the electrode rod, and the furnace wall is cooled. This prevents localized wear and tear on the refractories that make up the structure.

Second, maximum power can be continuously supplied to the electrode rod, the melting time can be greatly shortened, and high productivity can be obtained.

Hereinafter, an example of the method of the present invention will be explained in more detail based on the drawings.

In FIG. 1, a furnace stand 14 with retaining teeth 12 formed in the horizontal direction is fixed to the upper surface of the base 1o.Short legs 18 are provided with engaging teeth 16 formed on an arc. is the engaging tooth 12
and 16 are placed on the furnace stand 14 in a mutually engaged state, and one end of the short leg 18 is supported by a tilting drive device 2o that extends and contracts in the longitudinal direction, so that the furnace body 26, which will be described later, is not tilted. It has become. Note that 21 is a ladle that receives molten steel from the furnace body 26. A plurality of rollers 22 are provided on the short legs 18 and arranged circumferentially, and the arc furnace 2
Four furnace bodies 26 are rotatably supported by rollers 22 about their vertical central axes.

That is, as shown in detail in FIG.
is rotatably supported by a bearing 28, and
Connected to reducer 8° via chain 32, reducer 8
It is designed to be rotationally driven by a motor 84 connected to the motor 84. The roller 22 has flanges 8 on both ends thereof.
6, and a rail 37 with a rectangular cross section fixed annularly at the bottom of the furnace body 26 is received between the flanges 86, so that the furnace body 26 is aligned with its vertical central axis -
It is supported so that it can be rotated around.

Returning to FIG. 1, a furnace lid 8 is fitted into the opening of the furnace body 26, and eight vertical electrode rods 4o are arranged at equal intervals through the central opening of the furnace V38. , so as to be inserted into the furnace body 26. A central lid 42 through which the electrode rod 4o passes is suspended by a frame 44 from the central opening of the furnace lid 88.

As shown in FIGS. 8 and 4, the furnace body 26 is composed of a silk-like furnace bottom 46 and a cylindrical furnace side 48 comprising a cooling water tank. The furnace side part 48 has one circumferential direction (<
A plurality of divided water tanks 50a to 50 (in this embodiment, two stages) are provided. As shown in FIG. 4, pipes 52 and 54 for circulating cooling water are connected to the water tanks 50a to 5of, respectively, and a return pipe 5 is connected to the water tanks 50a to 5of.
4 are each provided with a plurality of nine temperature sensors 56 for detecting the temperature of the water tanks 50a to 5of. The temperature sensor 56 measures the temperature of the cooling water returned from the water tanks 50a to 50 or the furnace body 26 near the water tanks 50& to 50f.
Temperature signal 8T representing the temperature If corresponding to the internal temperature state
a to STf are respectively supplied to the discrimination circuit 58. The determination circuit 58 detects the possibility that a hot spot may occur near the water tank 5 (l to 50f) in the furnace body 26 and damage the refractories.
When a condition occurs, a certain temperature that the aquarium reaches is preset, and the temperature indicated by the specified number of temperature signals STa to STf exceeds that certain temperature. At this time, a starting signal 8D for rotating the furnace body 26 is output.

Next, a method of melting the tLA arc furnace configured as above will be explained.

A device (not shown) pulls up the electrode rod 40 and charges the scrap 64 into the furnace body 26 with the furnace lids 88, 42 removed and cleaned.
2 is fitted into the furnace body 26 again. After that, electrode rod 4
0 is gradually inserted into the furnace body 26, and the electrode rod 4
Maximum power is applied to 0. For this reason, an arc is generated between the electrode rod 40 and the Nuta Wrap 64, and the scrap 64 around the electrode rod 40 is not efficiently melted. Electrode rod 4
0 is inserted into the furnace body 26, and after a certain period of time has elapsed, as shown in FIGS. separation f
Scrap 64 remains on the furnace wall surface.

In the above state, among the water tanks forming a part of the furnace wall, the water tanks 50b, 50d, and 50f are located close to the electrode rod 40, and the inner surface of the water tanks 50)), 50d, and 59110' are located close to the electrode rod 40. Since the upper scrap 64 is melted first, the temperature of the cooling water circulating in the water tanks 501), 50(1,5Or) is lower than that of the other water tanks 50a, 501'3.

508'z The temperature signals STa to STf that are higher than the temperature of the circulating cooling water and represent those temperatures are detected by the discriminating circuit 5.
8.

A state in which the inner wall surface of the furnace body 26 located near the electrode rod 40 is exposed to the high temperature molten steel near the electrode rod 40, and there is a risk that the refractories in that area may be damaged.
When the temperature of at least one of 0b, 50d, and 50r exceeds a predetermined temperature, the discrimination circuit 58 outputs a start signal SD. For this reason, driving power is supplied to the motor 34 from a drive circuit (not shown), and the furnace body 26 is rotated at a predetermined angle with respect to the electrode rod 40 (in this embodiment, from the reference position to the left and right). (30 degrees each) rotation drive.

As a result, the remaining scrap 64 is not relatively moved to the position closest to the electrode rod 40 and is rapidly melted, and the scrap 64 has already melted and the temperature around the electrode rod 40 is high. The inner wall surface of the furnace body 26 located near the parts, that is, the water tanks 501), 50d, and 50f in FIG.
A furnace bottom 46 located below the inner surface of the furnace and the slats is spaced apart from the electrode rod 4°. Therefore, scrap 64
is melted extremely efficiently by a powerful arc based on the maximum power supply, and the inner wall surface of the furnace body 26, which was located close to the electrode rod 40, is moved away and generated near the electrode rod. Local damage to refractories etc. caused by hot pots can be suitably prevented.

In this way, according to the present embodiment, the electrode rod 40 and the furnace body 26 are rotated and expanded relative to each other while the maximum power is supplied to the electrode rod 4o, so that the nukrag 64 is caused by the arc based on the maximum power. Extremely efficient melting, arc furnace 24
Productivity will be greatly improved. Moreover, since the inner wall surface of the furnace body 26, which is located close to the electrode rod 40 and is exposed to the high temperature around the electrode rod 40, is moved in the direction away from the furnace body 26, the inner wall surface of the furnace body 26, which is located close to the electrode rod 40 and is exposed to the high temperature around the electrode rod 40, is not moved in the direction of separation. Local damage is total<j
W/ It's likeness.

According to this embodiment, the situation inside the furnace is grasped by the temperature rise of the water tank forming a part of the furnace wall, and this prevents the furnace body 26 and the electric rod 40 from rotating relative to each other. n, so
Compared to the case where a method of continuous slow relative rotation or a time control method of relative rotation after a certain period of time is used, even if the dissolution time varies in relation to the properties of the Nuclap 64, the side surface of the electrode rod 40 is It has the advantage of completely eliminating the risk of electrical discharge or breakage.

In addition, since it is possible to ascertain the occurrence of hot spots in the furnace due to the temperature rise of the water tanks 50a to 50f that are close to the electrode rod 40, it is possible to detect hot spots in the furnace compared to detection using thermocouples or the like. This has the advantage of eliminating problems such as damage to thermocouples due to wear and tear and responsiveness, resulting in high reliability.

Furthermore, since the furnace body 26 and the electrode rod 40 are configured to rotate relative to each other within a certain angular range, the furnace body 26
There is an advantage that the structure of cooling pipes, exhaust ducts, etc. connected to 6 can be easily and simply constructed.

Although the method of the present invention has been described above based on the drawings showing an example of the method of the present invention, the method of the present invention can also be applied to other aspects.

For example, the electrode rod 40 may be rotated about an axis relative to the furnace body 26. In short, the electrode rod 40 and the furnace body 26 only have to be rotated fL relative to each other.

In the embodiment described above, the furnace body 26 and the electrode rod 40 are approximately 6
Although it is rotated with a relative angular width of 0 degrees, the angular range can be changed variously depending on the number and arrangement of the electrode rods 40. For example, when the electrode rods 40 are two pieces, the rotation angle is approximately 90 degrees. Angular width is preferred.

In the embodiment described above, the relative rotation between the furnace body 26 and the electrode rod 40 is caused by an increase in the temperature of the water tank forming a part of the furnace wall of the furnace body 26. Even if the relative rotation is performed continuously depending on the speed of t', or if the relative rotation is performed after a predetermined period of time, a certain effect can be obtained.

In addition, in order to detect the heating status inside the furnace body 26, it is necessary to not only increase the temperature of the water tank, but also use a thermocouple buried in the furnace wall of the furnace body 26 and a radiation pyrometer that detects the temperature of the furnace wall. It goes without saying that other temperature detection means such as the above may also be used.

[Brief explanation of drawings]

FIG. 1 is a cutaway front view of essential parts of an arc furnace to which an example of the method of the present invention is applied. FIG. 2 is a sectional view of a main part showing the rotational drive section of the arc furnace of FIG. 1. 3 and 4 are a cross-sectional view and a vertical cross-sectional view, respectively, illustrating the melting state of the arc furnace shown in FIG. 1. 26: Furnace body 40: Electrode rods 50a to 50
f: Water tank (cooling water tank) 64 Niscrap (material to be melted) Applicant Daido Steel Co., Ltd. Figure 1 Figure 2

Claims (3)

[Claims] (1) By inserting a plurality of electrode rods into a container-shaped furnace body in a direction approximately parallel to the vertical central axis of the furnace body and generating an arc, the fLft to be melted is charged into the furnace body. When melting the material, while performing the melting operation of the material to be melted by the arc, the furnace body and the electrode rod are rotated relative to each other around the vertical central axis of the furnace body, thereby supplying power to the electrode rod. An arc furnace melting method characterized in that the material to be melted is melted without limiting power. (2) The arc furnace melting method according to claim 1, wherein the relative rotation between the furnace body and the electrode rod is performed within a predetermined range of angles. (3) The furnace body is provided with a cooling water tank forming the furnace wall in the vicinity of the electrode rod, and the temperature of the cooling water tank is predetermined; f'L
The arc furnace melting method according to claim 1 or 2, wherein the furnace body and the electrode rod are rotated relative to each other when a certain fc temperature is reached.