JPS5873713A - Manufacture of steel containing strong deoxidation element - Google Patents

Abstract

PURPOSE:To elevate additive yield of Ti and Ca which oxidize easily, by converting molten steel adjusted to a desired steel component to refined steel by use of a flux, and after that, adding Ti and Ca, agitating a molten bath electromagnetically in a continuous casting mold. CONSTITUTION:A component of molten steel is adjusted to an object composition by adding C, Si, Mn, Al, etc. except Ti and Ca whose deoxidizing force is extremely strong, by a vacuum treatment device or a ladle, etc. Non-metallic inclusions such as Al2O3, SiO2, MnO, etc. generated in this case are converted to slags by blowing by means of powder injection of CaO or Cao-CaF2, etc., and are removed, by which the molten steel is refined. This molten bath S is poured into a continous casting mold 10, is vibrated and agitated by 0.4-2m/ second in the horizontal direction by an electromagnetic agitating device 11, and from the vicinity of an inflow port of a tandish 14 or an immersing nozzle 13, a wire 16 of Ti and Ca are led in together with inert gas of 2.5-30cc per 1kg of molten steel. In this way, Ti and Ca which oxidize easily are added to the molten steel S with high yield and are converted to an alloy.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing steel containing strong deoxidizing elements.

In most cases, the molten steel poured into a continuous caster is usually adjusted to have all alloying elements within the desired range using a ladle or a top refining device (RH, DH, VAD), etc. Ru. Mn
, common elements such as si (those whose deoxidizing power is not very strong)
There are no particular problems with this type of method, but elements with strong deoxidizing power, such as ea%-Tt, have various problems. That is, C
a x Ti is a very good thing #11! Because of the labor pressure, when it is added in the refining equipment, etc., until it is poured into the subsequent continuous casting mold, ladle refractories, tundish refractories, etc. Reacts with the slag in the ladle tundish, causing Ca%
It produces oxides of TI and acts as an original alloying element.
Not only does Ti and Ca decrease (yield decrease), but their agglomerates deteriorate the internal quality and surface quality of the slab, making it impossible to obtain slabs of desirable quality.

For example, in the case of copper slabs for deep drawing provided for continuous depurification, it is common to provide slabs with compositions as shown in Table 1.

Table 1 (wt%) The general method for producing steel with such a composition is to first perform natural decarburization or forced decarburization in vacuum degassing to reduce the carbon in the steel to 0.0020% or less. (In most cases, the powder content in the steel is 11,000 pp or more.) Then, AI is deoxidized, and finally Ti is added. However, in the case where Ti is successively added to Al using a vacuum device, the primary deoxidizing components floating in the steel bath are A15Oa and Ti.
reacts, producing many TtO-based inclusions. Since the generated TiOz is highly reactive with refractories, it continues to react with the refractories, resulting in 1. As a result, the Sigh contained in the refractory on the surface J is discharged into the molten steel, and the 5in2 reacts with Ti in the molten steel, resulting in further Ti
Repeating the vicious cycle of producing O2-based inclusions,
It is unavoidable that the molten steel becomes highly contaminated with I"i0*.

Furthermore, during the process of forming the steel billets, the immersed nozzle refractories in the ladle and tundish, the tundish refractories, the immersed nozzle refractories in the tundish mold, and the bathtub repeatedly come into contact with the refractories. Si in refractories
'rj in the molten steel reacts with O2 or A I20g, and T j
'O2-based inclusions are produced and contamination is increased.

10,000 ladle, 5 in the slag floating in the tundish
Reactions of Ti in molten steel with i02, FeO% AlzOa, etc. cannot be ignored, and Tie reacts with Ti in the same way as refractories.

This causes the formation of Ti0J-based inclusions, and the actually finished slab becomes contaminated with Ti0J-based inclusions, so that the slab cannot sufficiently withstand the above objective 1.

This can also be said about Ca, which has a strong ability to forgive, just like Ti.

As mentioned above, the present invention has the following advantages: the reduction in yield when adding elements with strong deoxidizing power to molten steel, the difficulty in adjusting the composition, the surface of the slab,
This provides a very advantageous method for resolving deterioration caused by endogenous inclusions.

That is, the gist of the present invention is to add C to molten steel adjusted to the desired steel composition.
A flux mainly composed of aO is added to remove primary deoxidation products to obtain clean steel, and the molten steel is actively flowed in a continuous casting mold. Forcible removal of such substances lies in the addition of elements.

The present invention will be explained in detail below.

In the present invention, first, CXSI X'bAn, A1, etc. other than Ti and Ca, which have strong deoxidizing power, are added in a vacuum processing apparatus and/or a ladle to adjust the components.

That is, the desired steel composition in the present invention was adjusted below. Molten steel means that steel components other than metallic elements having a strong deoxidizing effect such as Ti1Ca have been added and adjusted.

Due to the steel Jj adjustment, the bath contains a considerable amount of primary deoxidation products, Al2O3, 5102, and MnO (7)-tl.
”, CaOzCab-CaF2 etc. / injection / or these artificial fluxes to molten steel.
Then, the conventional reflux bubbling is carried out to float and separate most of the deoxidized products suspended in the molten steel into clean steel. 'f'i,
In order to avoid a reaction with Ca, etc., I asked Shishifumachi Kashihiko.

In the continuous casting process of the present invention, a strong deoxidizing element (hereinafter referred to as a strong deoxidizing element) such as 1.i and Ca is added, but in order to uniformly dissolve and diffuse the added element, ,
The additive elements are supplied by actively flowing the molten steel in a copper-shaped circle, preferably forming it into a wire shape. More preferably, the wire is fed through a guide made of a suitable refractory material. At this time, it is preferable that the guide 9 penetrates the bath surrounding slag layer and opens at the position where the molten steel flows due to electromagnetic stirring.

Continuous casting in the present invention involves flowing the molten steel in the mold and adjusting Tt M in accordance with the casting speed from the tundish onward.
A strong deoxidizing agent such as Ca is added, but the following measures are taken to ensure uniform dissolution and diffusion.

An electromagnetic stirrer is installed in the mold, and Tt % is applied from the top of the mold.
The surface of the molten steel is covered with Ca or an alloy of these.
It is added to the mold steel by penetrating the first layer.

FIG. 1 is an explanatory diagram of the 11th to 10th part of the continuous casting method to which the present invention is applied. The tundish 14 is provided with an immersion nozzle 13 via a sliding nozzle 15, - the mold 1
A single layer 17 of ξ is formed on each steel S in 0. The mold 10 is equipped with an electromagnetic stirrer 11, and a refractory rod 12 is movable up and down. 16 is a strong deoxidizing source wire, 18 is an inert gas blower. There is.

In this case, the flow velocity of the molten steel in the electromagnetic stirrer is at least 0.4 m/! If it is not more than J', Ti will be uniform in the mold.
No dissolution of XCa occurs. If it is longer than 2.0 m for 7 seconds, powder etc. will be rolled in, which is undesirable.

The flow direction of the molten steel using electromagnetic stirring in the present invention is that if the molten steel flows in the vertical direction of the mold, the added Ti5Ca will actively contact the powder on the upper surface of the mold and have more chances to react with 5i02 etc. in the powder. It is preferred to provide horizontal flow.

Sin, which remains in common practice even if the above methods are used,
Al2oz, fVlno and °l'i added in the template
, a slight reaction with Ca is observed, and °1002-based valve inclusions are produced. Therefore, it is extremely effective to blow inert gas into the steel in order to promote its separation and flotation.

Another method of the present invention is to add a forced decomposition agent together with an inert gas from the vicinity of the molten steel outlet of the tundish.

This-? lJ will be explained for the second-.

In the figure, molten steel S is injected from a tundish 14 through a sliding nozzle 15 and into an amio from an immersion nozzle 13. A virtual stopper 19 is installed near the outlet of the sliding nozzle 15, and a strong deoxidizing source wire is supplied together with an inert gas 18 through the hollow part of the stopper, and reaches the mold together with the molten steel. 17 is powder.

In the present invention, since inert gas is injected into the submerged nozzle between the tundish and the mold, extremely good agitation can be obtained within the nozzle and mold, and the molten steel flow rate in that area can be reduced to 0.
4 B/sec or more has the advantage of promoting floating of inclusions within the mold.

In this case, the inert gas pressure is 2.5 c per molten steel.
e/Fe-Kg'~30 CC-/Fe 4g is preferred. If it is less than 2.5 CC/Fe-ceramic, please add enough Ca,
Ti cannot be uniformly dissolved in the nozzle, and 30CC
/Fe, Kf or higher, the molten steel level within the mold will fluctuate greatly, and problems such as powder entrainment may occur.

The method of adding a strong deoxidizing source to molten steel according to the present invention has been described above, but the present invention is not limited to these methods. Of course, it does not depart from the scope of the present invention to insert a wire containing a strong deoxidizing element into the immersion nozzle.

Example 1 When tapping molten steel into a ladle in a converter, Fe-Mn
12 K9/l XFe-8i 4.4 Kq/l
XAl 2 O, 8 Kg/l was added to obtain steel with the following composition.

Table 2 (wt chi) Before tapping 0.100,010.200.0100.005
TR, 300 marks o, 12'o, 2o 1.000
．． 0100.00510.0251 s.

Then, in a ladle, add CaO powder 5K9/l and CaF21
By injecting Kt/l into molten steel, T and O are 25
After reducing the temperature to ppm, the molten steel is poured into a mold equipped with an in-mold electromagnetic stirrer that moves the molten steel horizontally into the mold. A flow rate of 1 m/wc is applied to the molten steel, and Ca-Al wire is fed from four supply devices. , Ca addition amount is 100
When f/ton was supplied, the Ca concentration of the slab was 0.0.
06%, a high Ca yield of 60% was obtained, and the spheroidization treatment of sulfides in the slab could be completed.

The casting speed at this time was 0.8 m/'J.

Example 2 250 ladle self-molten steel is degassed by RH degassing equipment.
Alloy composition adjustment was carried out as shown in Table 3.

Table 3 Alloys added during treatment were: Fe-Mn 1.5 Kg
/l, AIo, and 4 sukes/l. ,,:,:,,,:
5゜Then, o powder QKf/l of CaO: CaF*=5:1 was injected into the molten steel in the ladle, and T.
After reducing the O to 30 ppm, when injecting into the continuous casting mold, feed the Fe-Ti wire from the stopper to 30 CC/F.
When Ti was supplied together with an inert gas of K9 at a rate of 560 f/l, the Ti in the slab was
It was possible to add Ti at a concentration of 0.05% and a Ti yield of 90%. The casting speed at this time was 1.6 m/min, and the molten steel flow rate was 1.
．． The depth was 5m.

[Brief explanation of the drawing]

FIG. 1 is a detailed explanatory diagram of the present invention, and FIG. 2 is an explanatory diagram of another embodiment of the present invention.

Claims (1)

[Claims] 1. Add a CaO-based flux to the molten steel adjusted to the desired steel composition to remove primary deoxidation products to obtain clean steel, and add it to the molten steel flowing section after the tundish. A method for producing steel containing strong deoxidizing elements, which comprises adding strong deoxidizing elements such as Ti and Ca in accordance with the casting speed. 2 Continuous casting Molten steel in the mold horizontally 0.4 m-2, 0
2. The method for manufacturing a steel containing strong deoxidizing elements according to claim 1, which comprises electromagnetically stirring at a rate of m/sec and adding strong deoxidizing elements such as Ti and Ca from the upper part of the mold. 3 TI from near the tundish outlet or from the immersion nozzle
% Ca Q'J strong deoxidizing element, 2.5 CC/Fe
- A method for producing element-added steel according to claim 1, wherein the forced removal is added together with an inert gas of 9 to 30 CC/Fe-Kp.