JPS6335738A - Manufacture of steel by bottom blowing in electric furnace - Google Patents

Abstract

PURPOSE:To shorten the time required to manufacture steel by charging scraps into a furnace while blowing gas from a gas blowing hole pierced in the hearth and by sticking molten steel remaining in the furnace to the scraps to effectively transfer the heat of the molten steel to the scraps. CONSTITUTION:While gas is blown from a gas blowing hole 4 pierced in the hearth 3 of an electric furnace so as to prevent molten steel 8 remaining in the furnace from flowing out, scraps 7 are charged into the furnace. Electric current is then supplied and immediately gas is blown into the furnace to swell or splash the molten steel 8. The molten steel 8 is stuck to the scraps 7 in the furnace, so the heat of the steel is rapidly transferred to the scraps.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a bottom-blown steelmaking method that uses a residual metal method in an electric furnace.

[Problems with conventional technology]

AC or DC electric arc furnaces are widely used as a melting and refining method for ordinary steel and alloy steel, and recently, oil and oxygen injection has also been used in combination, and the melting time has been considerably shortened. Also, as a means of promoting chemical reactions during the prime stage,
A technique has also been proposed in which gas is injected from the bottom of the furnace. The present inventors first improved this method of blowing gas from the bottom of the furnace,
We proposed a melting method in which the molten steel generated by energization is sprayed from the bottom of the furnace. However, even with this method, sufficient effects could not be achieved because there was no molten metal blown up as a splash in the initial stage of scrap melting.

[Means to solve the problem]

The present invention was created as a result of research and repeated experiments in order to solve the above-mentioned problems.The purpose of this invention is to convert the heat of molten steel that has been left in the furnace into electricity. The goal is to effectively utilize the bottom-blowing melting method of the furnace to shorten the melting time in steelmaking.

In order to achieve this object, the present invention intentionally leaves molten steel in the furnace, and charges the scrap while blowing gas to the extent that the remaining molten steel in the furnace does not flow out using a gas injection port provided at the bottom of the furnace. Immediately after energization, gas is continuously or intermittently blown into the furnace, causing the molten steel to rise or splash and adhere to the amorphous scrap that occupies the space inside the furnace. .

Traditionally, there is a steelmaking method using an electric furnace called the residual metal method (a method in which a part of the molten steel that has been melted and refined by energization is left in the furnace, and scrap is charged into it for melting and refining). However, this term applies to the steelmaking furnace body (including molten metal obtained by melting and refining), which has a huge heat capacity.
The present invention aims to utilize the amount of heat for melting scrap in the next charge, and is essentially static, and is not a dynamic heat utilization method like the bottom-blowing melting method described above.
This method of utilizing static heat is combined with the dynamic bottom-blown steelmaking method to create a synergistic effect.

FIG. 1 schematically shows the principle of the present invention in a sectional view of an electric furnace.

A side wall 2 made of refractory bricks and a hearth 3 made of a dry stamp are provided inside the iron skin 1, and a gas blowing plug 4 is further set in a siding brick 5 in this hearth. The figure shows the initial stage of melting, and the electrode 6 is still only partially immersed in the upper surface of the scrap 7. However, since the present invention also uses the residual metal method, the lower part of the scrap is immersed in the molten metal 8.

Immediately after the start of melting of the scrap, the molten steel 8 is blown up as a molten steel pillar or splash in the height direction of the scrap by strong gas blowing from the plug 4, and hits the scrap or rises through the voids of the scrap,
Some of it sticks to the scrap, and some of it loses its upward energy and drips through the gaps in the scrap. Due to such strong gas injection, the heat balance in the furnace rapidly approaches equilibrium and melting is promoted.

〔Example〕

A 50T electric furnace was modified to a bottom-blowing electric furnace, and a comparative test was conducted under the following conditions.

Non-concentrically in the hot zone hearth, two on the tapping hole side from the core hearth and one on the charging hole side from the core hearth.
A total of 3 gas injection plugs were installed, and about 10 tons of molten metal from the previous charge remained in the furnace, and while blowing gas gently, scrap was charged and the furnace condition was judged.
N1/Plug N2 gas is injected into the furnace to melt the scrap, and even after the melting is complete, strong gas injection is continued (the height of the molten metal is regulated at 50 to 500 mm) to promote the chemical reaction. While doing so, I refined it. 1st
The table shows the method of the present invention (A) bottom blowing melting and refining method (B) amount of remaining hot metal f4
Table 2 shows the six charge comparison operation data for each of the three methods (C), and shows the comprehensive evaluation for each method in numerical values. If the amount of remaining hot metal is too small, the synergistic effect will not increase, and if it is too large, the steelmaking efficiency (T/Hr) will not increase. Total amount of molten metal 1O~30
% is preferable.

From the above comprehensive evaluation, it can be seen that the method of the present invention is superior in terms of both power consumption per ton of product and special production, even when compared to the latest bottom-blown melting and refining method (B), or compared to a simple residual metal steelmaking method. I can understand that it is much better.

As can be understood from the above explanation, the present invention uses both powerful gas injection and the residual metal method, aiming for a synergistic effect. Therefore, as long as the principle of the present invention is utilized, it is possible to blow into the furnace. There are no essential restrictions on the installation position of the plugs, the number of the plugs, or the amount of gas blown in.Although N and gas were used in the examples, depending on the expected effect, the material of the plugs, etc.
It goes without saying that oxidizing gas and reducing gas can be used.

〔Effect of the invention〕

As detailed above, when the method of the present invention is used, it has a significant effect of shortening steelmaking time and improving steelmaking efficiency per unit time, even compared to the most advanced electric furnace bottom-blowing melting and refining method. has been proven.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of the lower half of an electric furnace showing the implementation status of the present invention. 1... Steel skin 2... Side wall 3... Hearth 4... Gas injection plug 5... Bricks around the tuyere 6. ... Electrode 7 ... Scrap 8 ... Molten steel

Claims (1)

[Claims] Using the gas inlet installed in the hearth, scrap is charged while blowing gas to the extent that the remaining molten steel in the furnace does not flow out.
A residual metal characterized by blowing gas into the furnace continuously or intermittently immediately after energization, causing the molten steel to rise up or splash, and to be attached to or sprayed onto the amorphous scrap that occupies the space inside the furnace. Electric furnace bottom-blown steelmaking method