JPS5839886B2 - Basicity adjustment method for bottom blowing converter - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for adjusting the basicity of a bottom-blown converter,
This paper proposes an advantageous method that can quickly and accurately adjust the basicity, particularly when applied to a bottom-blown converter, when there is a delay in slag formation due to excess CaO.

Conventionally, sand, gravel, etc. have been added to converters for the purpose of adjusting the basicity of slag.

This corresponds to the recent increase in the production of heavy steel, where the content of P and S is strictly regulated.
This operation is adopted in response to the fact that as the amount of CaO introduced for the purpose of this increases, the tendency to worsen slag formation in the steel bath becomes stronger.

In other words, easily available sand and gravel are poured into a steel bath,
The Si02% content in the steel bath was increased to promote slag formation.

Conventionally, sand has generally been supplied into the converter by charging it from the furnace mouth.

Basicity adjustment using this method had the following drawbacks.

(1) Since the powder is charged from the upper furnace opening, when powder is used to promote the reaction, it is sucked into the dust collection system and most of the powder does not reach the steel bath.

(2) Since the slag and molten steel are not sufficiently stirred, if they are introduced from above, the slag remains trapped in the slag layer on the surface or is unevenly distributed, making the slag formation unstable.

Therefore, the actual basicity does not match the calculated basicity,
The deviation from the blowing calculation becomes large.

In addition, this increases the error in the heat of slag formation, worsens the accuracy of blow-off temperature variation, and adversely affects component adjustment.

The purpose of this invention is to overcome the drawbacks of the conventional basicity adjustment method described above, and it is possible to carry out steel smelting and refining by injecting refining gas together with the siding cooling gas into the steel bath through the double pipe siding at the bottom of the furnace. To adjust the basicity during bottom-blowing converter blowing, SiO2 natural mineral powder with a particle size of 1 mm or less is injected into the refining gas or By blowing directly into the steel melt with the entrainment of an inert gas, the basicity of the bath surface slag can be adjusted, improving the retention of the 5i02 natural mineral powder supplied to the steel bath and reducing the slag formation rate. The aim was to achieve improvements.

In general, most of the earth's surface is composed of feldspar, quartz, and mica, and the 5i02-containing natural mineral powder used in this invention exists in large quantities as guinea sandstone, feldspathic sandstone, and the like.

Therefore, since it is easily available and inexpensive, it is extremely advantageous to use such sand as a basicity regulator in the present invention.

As for the ingredients, since 5i02% in the converter slag is 10 to 20 degrees, it is necessary to use sand containing 20 or more strips as 5i02%, and more preferably sand containing 50 degrees or more is more suitable. This is preferable since it only requires a small amount.

The basicity adjustment method according to the present invention involves crushing and sifting the sand into a powder with a diameter of 1 hour or less and placing it at the bottom of the furnace, in order to cause the sand to flow together with the carrier gas. The feature is that the refining gas or inert gas is blown directly into the steel bath through the siding from the central channel for blowing the refining gas into the siding.

The above-mentioned bottom blowing converter equipped with a blowing tuyere consisting of double metal pipes concentrically inside and outside has excellent agitation characteristics in the steel bath because the refining gas is injected from the bottom of the furnace. Since the generated FeO is quickly reduced to C during the levitation process,
It has the advantage of good iron retention and rapid progress of the decarburization reaction.

On the other hand, the generated P2O5 and the like are easily reduced by C, and the oxidation of Fe is also delayed, so that the transfer of P to slag is delayed and dephosphorization is significantly inhibited.

For this reason, in a bottom-blown converter, calcined lime CaO powder is generally injected into the steel bath together with refining gas and inert gas from the central flow path of the blowing tuyere.

However, if only CaO powder is supplied from the bottom of the furnace, especially in the first half of the blowing process when it does not reach the point where it becomes slag,
Only the transfer of CaO to the slag becomes faster, and the basicity of the slag becomes higher, which significantly impairs the fluidity.

Therefore, in this invention, a predetermined amount of sand, that is, 5i02 component natural mineral powder, is injected either alone or together with the burnt lime powder to quickly maintain the slag basicity at an appropriate level. .

In short, in the present invention, 5i02 basicity adjusting sand such as sand is directly injected into the steel bath from the bottom tuyere, either alone or together with burnt lime, so that while the sand floats through the steel bath. Because it melts quickly and is absorbed into the slag layer,
A highly reactive slag is generated effectively and quickly, and the blown sand comes into contact with the steel bath at 100 ends.

Therefore, compared to the conventional method, there is no difference between the calculated value and the actual basicity.

This is clearly shown in Table 1.

In addition, as shown in Table 3, since sand is injected together with CaO powder, the basicity can always be kept constant, especially after Si combustion in the latter half of refining, making it possible to control the end point of blowing. It is easy to use and has the effect of improving the accuracy of temperature and components.

Table 4 shows examples of the components of the sand used in this invention.

As explained above, according to the present invention, the retention and slag formation rate of the blown sand are improved, the basicity can be quickly and accurately adjusted during blowing, and the composition and temperature at the end of blowing can be adjusted. Excellent effects similar to those found in industry can be achieved, such as improving the rate of engagement.

Claims (1)

[Claims] 1 In adjusting the basicity during the bottom blowing converter blowing process, which involves refining steel by injecting tuyere-cooling gas into the steel bath through the double pipe walls at the bottom of the furnace, the grain size is 1 m.
SiO2-based natural mineral powder with a diameter of mφ or less can be used alone or with C.
A bottom blowing process characterized by adjusting the basicity of the bath surface slag by directly blowing the aO powder into the steel bath from the center flow path of the above-mentioned slag with the accompanying refining gas or inert gas. How to adjust the basicity of a furnace.