JPS61513A - Manufacture of steel and its apparatus - Google Patents

Abstract

PURPOSE:To obtain steel having desired composition at low cost with use of one furnace by charging scraps into a smelting and refining furnace, smelting the scraps while blowing in an inert gas from the top, and regulating the composition while blowing in an inert gas and oxygen. CONSTITUTION:Scraps are charged into a smelting and refining furnace, and a lid 3 through which an electrode 5 is pierced is closed. The scraps are heated by arc and smelted while blowing in an inert gas from a bottom-blowing tuyere 1. Then the electrode 5 and the lid 3 are detached, and a lid 4 having a tuyere 6 for the secondary combustion and a smoke collecting port 41 is put on. An inert gas and oxygen are blown in from the tuyere 6, a large amt. of an inert gas and oxygen is blown in from the tuyere 1 to agitate strongly the melt, and refining is carried out. Necessary elements of an alloy are added to regulate the composition. Refined steel having desired composition is tapped through a tapping port 22. Consequently, steel having desired combustion can be manufacture in good yield with only one vessel.

Description

[Detailed description of the invention]

purpose of invention

[Industrial application field]

The present invention relates to a method and apparatus for manufacturing steel. According to the present invention, the two processes of scrap melting and refining can be carried out by one worker using one container.

[Conventional technology]

As the outside furnace refining method, RH, DHSFINKL-MO
There are HR, LF, AOD methods, etc., but these methods have advantages and disadvantages in various points such as degassing ability, desulfurization and deoxidizing ability, molten metal reheating ability, and refining efficiency. The applicant is
As a solution to these problems, we have established an out-of-furnace refining technology that achieves desulfurization and degassing in a short time by combining electrode heating and inert gas and slag-forming agent injection, which we have already disclosed under the name rGRAFJ method (special Kosho 5'l-55773
issue). The contents of Sagini's proposal are as follows. That is, the refining device includes a tiltable refining container, a tuyere for blowing an inert gas into a carrier gas and a slag-forming agent or an additive alloy into the molten metal, and an electrode for heating the molten metal and the slag-forming agent, When heating the electrode, use one whose tuyere is located above the molten metal surface. In a typical embodiment, the electrode is heated while blowing inert gas through a porous plug, and deoxidation, degassing, and desulfurization are mainly performed by slag refining. Next, the smelting furnace is tilted so that the tuyeres are at the bottom of the molten metal, and a large amount of inert gas and slag-forming agent are blown in at high pressure to perform deoxidation, desulfurization, denitrification, and dehydrogenation refining. The molten steel is transferred from a sliding nozzle to a mold or ladle.

[Problems to be solved by the invention]

In the above technology, a small amount of gas blown in during arc heating is handled by a porous plug placed below the molten metal surface, and a large amount of high-pressure gas blown in during refining is placed above the molten metal surface, while a porous plug is placed below the molten metal surface during refining. Each is blown through the tuyere. Therefore, it is necessary to tilt the refining furnace, which complicates the structure of the device and makes the work complicated. Another problem is that the porous plugs that have been used in the past are easily worn out. Furthermore, it is desirable that not only the refining of molten metal but also the melting and refining of cold materials such as cold scrap be performed in the same furnace. This greatly increases production efficiency and saves energy. By the way, if there were a tuyere that could adjust the amount of gas blown over a wide range, it would be possible to install it below the molten metal surface, eliminating the need to tilt the refining furnace, simplifying the structure of the equipment, and making it easier to operate. It also becomes easier. From this point of view, the present inventors have proceeded with the development of a tuyere that can adjust the flow rate over a wide range without changing the gas pressure much, and have completed a needle-type tuyere [furnace gas inlet J]. has already been proposed. (Special application 1986-6
No. 9539) Structure of the invention

[Means for solving the problem 1] The present invention applies the technology of the above-mentioned "furnace gas inlet" to the rG
It has been expanded by applying it to the RAFJ refining technology. The steel manufacturing method of the present invention basically involves charging scrap into a melting and refining furnace body equipped with a lower blowing tuyere that allows the amount of gas to be blown to be varied over a wide range as much as possible. , insert the electrode with a lid having an electrode hole, melt the scrap by arc heating while blowing a small amount of inert gas from the lower blowing tuyere, and then blowing a large amount of inert gas from the lower blowing tuyere. and/or refining while blowing oxygen and stirring vigorously, adding necessary alloying elements to adjust the composition, and tapping the thus obtained steel with the desired composition through a tapping port. Features. A preferable form of the method for manufacturing steel of the present invention in terms of oxygen blowing is as follows:
Scrap is charged into a melting and refining furnace body equipped with a lower blowing tuyere that can vary the amount of gas blown over a wide range, and the furnace body is covered with an electrode hole and an electrode is inserted thereinto.
Arc heating is performed to melt the scrap while blowing a small amount of inert gas from the lower blowing tuyere, then the electrode and the lid are removed, and a lid having a secondary combustion tuyere and a smoke collection port is placed,
Inert gas and/or oxygen is blown into the secondary combustion tuyere, and a large amount of inert gas and/or oxygen is blown into the lower blowing tuyere, and the necessary alloying elements are refined while being strongly stirred. Adjust the ingredients by adding
The method is characterized in that the steel having the desired composition obtained in this manner is tapped through a tapping port. The apparatus of the present invention for carrying out the above steel manufacturing method includes:
As shown in FIGS. 1 and 2 and B, a lower blowing tuyere 1 that can vary the amount of gas blown over a wide range, and a tapping port 22 (sliding nozzle in the illustrated example) are provided. It is characterized in that the furnace body 2 is combined with a lid 3 having an electrode hole into which an arc heating electrode 5 is inserted, and/or a lid 4 having a secondary combustion tuyere 6 and a smoke collection port 41. 21 is a slag outlet. [Function] By providing a lower blowing tuyere below the surface of the molten metal in the furnace that can adjust the gas flow rate, the opening of the tuyere can be prevented from being melted or damaged during arc heating, as shown in Figure 1. A small amount of inert gas can be blown out without causing blockages. Therefore, a porous plug is not necessary, and problems such as instability of the arc and strong stirring that causes the molten metal to come into contact with the electrode and increase the amount of C can be solved. On the other hand, during refining, as shown in FIG. 2 or B, the molten metal can be strongly stirred by blowing inert gas and oxygen gas from a large pot through the lower tuyere. If a secondary combustion tuyere is used as shown in Figure 2A, then oxygen gas is blown out together with inert gas or alone to cause secondary combustion of the CO generated in the furnace, and the resulting heat is used to Can reheat molten metal. [Embodiment 1] The needle type lower blowing tuyere 1 made by the present inventors described above is useful because the gas flow rate can be adjusted over a wide range. The structure when applied to the present invention is, as shown in FIG. It has a double cylindrical body consisting of an inner tube 11 and an outer tube 12, each having diameter portions 112 and 113, and a needle 15 that is partially inserted into the inner tube. It is provided with a means for driving it to a position between the position D1 and the retreated position ID2 in the inner tube, such as a hydraulic device (not shown). In carrying out the present invention, it is advantageous to use a twin furnace type in which two of the aforementioned melting-refining furnace bodies are used alternately for melting and refining. That is, as shown in FIG. 4, scrap 8 is charged into one furnace body 2A, a lid 3 having an electrode hole is placed on the furnace body 2A, an electrode 5 is inserted, and the scrap is melted by arc heating. The other furnace body 2B is covered with a lid 4 having a secondary combustion tuyere 6 and a smoke collection port 41, and inert gas and oxygen are blown thereinto for refining and component adjustment. After producing the desired steel 9, tap the steel as shown in Fig. 4 (■), then charge the scrap as shown in Fig. 4 (■), and replace the lids 3 and 4 of the two furnaces with each other. . Subsequently, as shown in FIG.
In this step, the electrode 5 is inserted and the scrap is melted by arc heating. When the refining in the furnace 2A is completed, the steel is tapped as shown in FIG. 4V, and scrap is charged as shown in FIG. 4■. During this time, arc melting progresses in the other furnace 2B. Then, the state returns to the state shown in FIG. 4I, and the above operation is repeated thereafter. [Example] Materials having the following composition were charged into a furnace and melted and refined according to the steps described below to produce 5US304. Chopper 430KaSUH368
00K (I FCr H5720K (1' MNi 22OK. Ca0 to 100! J Iron hammered board scrap
610K (to 13,500!) After arc heating for about 60 minutes while blowing Ar at 60ONm 3 /min from the bottom blowing needle tuyere, 600Kg of hammered iron plate scraps were installed in parallel and arc heating was performed for about 45 minutes. Most of the charged scrap was melted. Arc heating was continued, and when the temperature reached 1630°C, the arc heating electrode and lid were removed and the Me-N
i 2OK (1, Ga 025K (+) and lightly calcined dolomite 50K () were put in, and a lid with secondary combustion tuyere and smoke collection port was placed. The temperature inside the furnace when the lid was placed was:
The temperature was 1545°C. Ar gas was blown at a rate of 65ONm3/min and oxygen gas was blown at a rate of 230ONm3/min from the bottom blowing needle tuyere, and Ar gas was blown at 15ONm3/min and oxygen gas was blown at 1.
Blow at a rate of 30ONII 13/min, the first for 20 minutes.
Stage refining (decarbonization) was carried out. Furthermore, from the downward blowing needle tuyere, Ar gas 65ONm3/min and oxygen gas 18
0ONm3/min is blown into the secondary combustion tuyeres.
Gas 15ONII13/min, oxygen gas 80ONn+ 3
/min, and second stage refining (decarburization) was performed for about 15 minutes. After introducing Ca025Ko and MNi 65KO, 185ON Ar gas was added from the bottom blowing needle tuyere.
The third stage refining was carried out for about 15 minutes by blowing 150 m3/min of oxygen gas and 25 ON m3/min of oxygen gas from the secondary combustion tuyeres. The temperature had reached 1770°C. After that, Ar gas 60ONm3/
FSi 2 to 8K (], FCr
)-16 was added, 3Kg of FSi 2 and 1Kg of FS were added, and the molten steel was poured into the sliding nozzle while blowing nitrogen at 300 to 40 ONII 13/min from the bottom blowing needle tuyere. I visited the ingot through. The obtained steel has the following composition: C: 0.039%, Si: 0.26%, Mrl: 1
゜94%, P: 0.020%, S: 0.015%, CO
:0. 03%, Ni: 8, 11%, Cr: 18.50
% and MO:Q, 038%, which satisfied the standards of 5US304. The component recovery rates of the above examples are shown in the table. Cr recovery rate is 99.9%, Ni recovery rate is 99.5%.
It can be seen that this is a very high value. In the conventional technology,
The recovery rate of Or is 96%, and the recovery rate of Ni is 97%. In addition, the yield of tapped metal, which was 97% in the conventional method, was improved to 98.8%. Tapping metal yield - tapping time/charging amount - (0 mouths, roasting - year Initial loading Later loading Total composition (%) (ko)
(Ka) AC2,0268,30
,268,5 SiO,4615,557,072,5Mn
2.48 83.8 0
B3.8P O,0140,500,
5S O,0100,30,50,8CI
O,031,001,ONi 7.
26 275.4 26.0 271.4
Cr 17.91 605.4 10°7 616. IMo O,0170,60
0.6X recovery rate - A/B x 100 (%) Amount + 810S amount)
Loss (%) Component (%>
(kg)B(ka)0.039 1.3
67.2 -0.26 8,7
63.8, -1.94 64.6
19.2 77.10.020 0.7
+0.2 -0.015 0.
5 0.3 -0.03 1.
0 0 1008.11 270.0
1.4 99.518.50 615
．． 9 0.2 99.90.038
1.3 ±0 100Bat 23
65.0 20.8 99.1 Effects of the Invention According to the present invention, steel production from scrap melting power to refining and casting can be carried out in the same furnace. The device is simple and easy to operate. The fact that the furnace body does not need to be tilted (17) means that the required height from the hot water level h\ to the edge of the furnace can be reduced, which means that the volume of the furnace can be used all at once. means. Not having to transfer high-temperature molten metal greatly contributes to saving thermal energy (of course). In particular, in the twin furnace type, which is the preferred embodiment, the two types of furnace lids are exchanged continuously. used for
Since there is no heat loss due to cooling of the furnace body, there is only power loss, so the energy saving effect is remarkable. Of course, the combination of a second-stage furnace body and a set of two furnace lids is advantageous in terms of equipment construction costs, as only one power source is sufficient. In addition, high yields of expensive raw materials such as Cr, J, and Ni are useful for cost reduction. Eliminating the need for highly wearable, difficult to manage, and damaged core porous plugs is advantageous from the standpoint of improved device maintenance and safety.

[Brief explanation of the drawing]

1 and 2 are cross-sectional views of the refining apparatus of the present invention, with FIG. 1 showing the state during arc melting, and FIGS. 2A and 2 B both showing the state during refining. FIG. 3 is preferably provided in the refining apparatus of the present invention,
FIG. 2 is an enlarged cross-sectional view of a portion of FIGS. 1 and 2 showing the structure of the tuyere. FIG. 4 is a conceptual explanatory diagram showing a preferred embodiment of the manufacturing method of the present invention. 1... Bottom blowing tuyere 2... Furnace body 3... Arc heating lid 4... Refining lid 5... Arc heating electrode 6... Secondary combustion tuyere patent applicant Jindo Special Steel Co., Ltd. Agent Patent Attorney Suga So Otsutsu 1111 Figure 2 A Calculation 2 Figure 3 Procedural Amendment (White Side July 10, 1980 Commissioner of the Patent Office Manabu Shiga 1, Indication of Case 1988 Patent Application No. 120574 2, Name of the invention Steel manufacturing method and apparatus 3, Person making the amendment, Incident and relationship Patent applicant address 66, Hoshizaki-cho, Minami-ku, Nagoya, Aichi Prefecture Name (371) Daido Steel Co., Ltd. Company 4, agent 〒1
04 Address: Yasuda Fudosan Tsukiji Building, 2-15-14 Tsukiji, Chuo-ku, Tokyo v (541) 3792 Unit "'Nm" in column 6 of the detailed explanation of the invention in the specification, and in the following part of the statement of contents of the amendment 3 / minute" is corrected to "N237 minutes." Page 12, line 3, line 14, line 15, line 16/17, line 17, line 20 and line 20/page 13, line 1, page 2, 2 places), 6th line, 8th line, 12th line and 16th line

Claims (5)

[Claims] (1) Scrap is charged into a melting and refining furnace body equipped with a lower blowing tuyere and tapping port that can change the amount of gas blown into the furnace, a lid having an electrode hole is placed, and an electrode is inserted; The scrap is melted by arc heating while blowing a small amount of inert gas from the lower blowing tuyere, and then a large amount of inert gas and oxygen is blown from the lower blowing tuyere to perform refining while stirring strongly. A method for producing steel, which comprises adjusting the composition by adding alloying elements, and tapping the thus obtained steel having a desired composition through a tapping port. (2) Charge the scrap into a melting and refining furnace body equipped with a lower blowing tuyere and tapping port that can change the amount of gas blown into the furnace, cover with a lid having electrode holes, and insert electrodes; The scrap is melted by arc heating while blowing a small amount of inert gas through the lower tuyere, then the electrode and lid are removed, and a lid having a secondary combustion tuyere and a smoke collection port is placed on the secondary combustion tuyere. Inert gas and/or oxygen is blown in from the combustion tuyere, and a large amount of inert gas or inert gas and oxygen is blown in from the lower blowing tuyere. Refining is carried out with strong stirring, and necessary alloying elements are added. to adjust the ingredients,
A method for producing steel, which comprises tapping the thus obtained steel having a desired composition through a tapping port. (3) Two of the above-mentioned melting and refining furnace bodies are used, one of the furnace bodies is charged with scrap and covered with a lid having an electrode hole, and an electrode is inserted to perform scrap melting by arc heating, Meanwhile, the other furnace body is covered with a lid having secondary combustion tuyere and smoke collection port, and inert gas and oxygen are blown into the furnace to refine it, adjust the composition, and produce the desired steel. After that, scrap is charged, the lids of the two furnaces are replaced, and one furnace is used for refining and composition adjustment, and the other furnace is used for melting scrap by arc heating. The method for manufacturing steel according to claim 2, which comprises repeating the above operations. (4) A furnace body equipped with a lower blowing tuyere and tapping port that can vary the amount of gas blown over a wide range,
A steel manufacturing device characterized by combining a lid having an electrode hole into which an electrode for arc heating is inserted, and/or a lid having a tuyere for secondary combustion and a smoke collection port. (5) As a lower blowing tuyere, a double cylindrical body consisting of an inner tube and an outer tube, each consisting of a small diameter part whose tip opens into the furnace and a large diameter part connected to the small diameter part and which has a gas supply pipe connection port. a needle with a part inserted into the inner tube, and the needle is driven so that its tip is located between the forward position at the open end in the furnace and the retracted position at the large diameter part of the inner tube. The steel manufacturing apparatus according to claim 4, which uses a needle tuyere equipped with the apparatus.