JPS589123B2 - Tenro Chibari Tai Kabutsuno Sonmousokudogensyouhou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a refractory mainly composed of MgO and CaO, and more specifically, as a slag material for a pure oxygen top-blown converter lined with a dolomite refractory. This invention relates to a method for reducing the wear rate of refractories used by adjusting the basicity of slag and the concentration of MgO in slag using coal and magnesium silicate minerals in amounts that satisfy the calculation formula shown below. be.

Dolomitic refractories containing MgO and OaO as main components are usually used as the lining material for pure oxygen top-blown converters used in steelmaking.

The raw materials used for this dolomitic refractory are dolomite clinker, synthetic dolomite clinker, and magnesia clinker.

Dolomite clinker is made by firing dolomite ore at high temperature, and the one produced in Japan usually contains 33% MgO and Ca.
It has a chemical composition of around 0.061%.

Synthetic dolomite clinker is made by adding lime to magnesium hydroxide obtained from seawater and calcining it, and it contains 74% MgO.
The chemical composition is approximately 24% CaO.

Magnesia clinker can be obtained by calcining magnesite, brucite, etc., but in Japan, it is usually seawater magnesia clinker made by calcining magnesium hydroxide obtained by adding coal to seawater, and has an MgO content of 95 to 99%. is usually used.

The above raw materials are pulverized, particle size adjusted, tar pitch is added, heated and kneaded, and molded into bricks.
Tar dolomite bricks are baked at 400°C.

Burnt dolomite bricks are made by adding organic binders such as wax, asphalt, cumaron resin, and attacking polypropylene to the pulverized raw materials whose particle size has been adjusted, molding them, and firing them at a temperature of usually 1,400 to 1,700°C.

The chemical composition of these bricks varies depending on the combination of various raw materials, but generally MgO50-90 is used as a converter lining material.
%, CaO45-8%, impurity amount (Fe2O3, Al2
The total amount of O3 and SiO2 used is in the range of 1 to 5%.

Converter furnaces use these refractories as lining materials, add hot metal, scrap iron, coal, fluorite, and other auxiliary materials, and refine them by blowing in oxygen to produce steel.In this overculm, CaO, S
Slag containing iO2, FeOn, MnO, P2O5, etc. is generated, and this slag reacts with the refractory, resulting in severe wear and tear.

When the refractory is worn down to a certain thickness, the converter must be taken out of operation and replaced with new refractory.

Therefore, in order to save work efficiency, the cost of furnace construction, and the cost of bricks, it is desirable to extend the life of the converter by reducing the wear rate of the refractory as much as possible.

To this end, improvements are being made to the material of the bricks and spraying repairs are being carried out.Another method is attempting to reduce the rate of wear and tear of the refractories by adjusting the composition of the slag.

For example, Japanese Patent Publication No. 42-12327 attempts to reduce the chemical dissolution rate of bricks by increasing the MgO concentration in slag by adding activated MgO or activated dolomitic coal to slag.

Sunda Tokko Sho 48-8691 uses serpentine to increase the MgO concentration in slag.

By the way, as mentioned above, in Japan, dolomite refractories containing MgO and CaO as main components are often used as lining materials for converters.

Through various experiments, the inventors discovered that in the case of dolomitic refractories, increasing the MgO concentration in the slag and lowering the basicity of the slag significantly reduces the wear rate of the refractories, and completed the present invention. It is something that

Figure 1 shows the CaO
The results of a rotary erosion test performed by varying the basicity of -SiO2-Fe2O3-based slag are shown.

Conventionally, it was thought that the erosion rate of MgO-based or MgO-CaO refractories decreases as the basicity increases.

According to the experimental results, in pure magnesia bricks, the higher the basicity, the smaller the erosion, while in the case of dolomite bricks, contrary to expectations, the amount of erosion becomes smaller in the relatively low basicity range of 2 to 3.5. Furthermore, when the basicity exceeds the above range, the amount of erosion increases.

Also, regarding bricks with 90% MgO, CaO-Fe2O3
Figure 2 shows the results of an erosion test performed by adding MgO to -siO2-based slag.
It was found that the addition of gO had a large effect in reducing the amount of erosion loss.

This is because as the CaO/SiO2 ratio of slag increases, C
It is thought that the aO--Fe2O3-based liquid phase increases, and dolomite refractories are inferior in resistance to this CaO--Fe2O3-based liquid phase, so it is presumed that as the basicity of the slag increases, the rate of erosion increases.

Based on this experimental result, when applying it to a converter, if lightly calcined dolomite is used as a magnesia source, if the basicity is lowered, the amount of CaO will decrease, which is undesirable from the viewpoint of dephosphorization and desulfurization reactions. It is considered necessary to simultaneously add the SiO2 source in this manner.

In this sense, it is desirable to use a magnesium silicate mineral containing both MgO and SiO2.

Magnesium silicic minerals include MgO28-50%, SiO
Minerals containing 230-62%, such as serpentine (main component 3MgO
, 2SiO2, 2H2O) dungite (main component 2 (Mg-F
e) O-SiO2), talc (main components 3MgO, 4SiO
2.H2O) can be used.

Now, if the MgO content in these magnesian silicic minerals is [MgO]M (%), the amount used is WM, the amount of coal is WL, the amount of Si in hot metal is [Si]p (%), and the amount of hot metal is WP. The basicity B is, and from the experimental results shown in Figures 1 and 2, B=
It can be seen that 2 to 3.5 and A=0.08 or more are preferable.

Moreover, when A exceeds 0.07, the viscosity of the slag increases, which is undesirable, and A=0.08 to 0.07 is optimal.

In order to make the method of the present invention even more effective, the slag formation speed is very fast and the most efficient method is to use briquettes made by pulverizing and mixing limestone and magnesium silicate minerals and sintering them at a temperature of around 1300°C. It is true.

Examples will be described below.

Example 1 The wear rate of bricks was compared between normal operation using a 100 t pure oxygen top-blowing converter and the method of the present invention.

The chemical composition of the hot metal and the steel produced are shown in Table 1.

The chemical composition of the serpentine used is shown in Table 2.

FIGS. 2 and 3 show the relationships among B, A, WL, and WM determined using the above-mentioned equations (1) and (2).

Now B = 3, A = 0.05, that is, 4.5 tons of lime, 0 serpentine
．． Using 75 tons, low carbon steel was used 60 times and medium carbon steel was used 40 times.

Note that the molten pig iron blending ratio is 80%.

The results of investigating the expansion of the furnace inner diameter at the trunnion part are 1.
．． 54 mm, so the wear rate is 0.77 mm/time.

The wear rate when similar operations were carried out using the conventional method was 0.95.
The wear rate was reduced by implementing the method of the invention at mm/times.

Example 2 In this example, limestone and serpentine were mixed and fired to create a slag-forming agent.

Now if B=28, A=0.07, WL=4.5, WM
= 1.08, and if the IgLoss of limestone is 42%, the mixing ratio is 91% limestone and 9% serpentine.

These raw materials are ground to a particle size of 200 mesh or less using a tube mill, mixed to the above ratio, added with 5% moisture, and shaped using a briquette molding machine to form an almond shape with a length of 40 mm.

Then, it is fired at 1300°C in a rotary kiln.

A 100 t converter was operated using the slag forming agent thus produced.

The chemical composition of the hot metal and the steel to be produced are the same as in Table 1.

The amount of slag-forming agent added was 5.6 tons, and the hot metal blending ratio was 80%.

The wear rate in this case was 0.70 mm/time, which was a 27% improvement compared to the conventional method.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the relationship between erosion dimensions and slag basicity of MgO 78% dolomitic brick, MgO 90% dolomitic brick, and MgO 98% magnesia brick caused by CaO-SiO2-Fe2O3 system slag. Figure 2 shows the erosion dimensions due to CaO-SiO2-Fe2O3-based slag, the basicity of the slag, and the amount of MgO/CaO+S.
The relationship diagram of iO2 amount, Figure 3 shows [Si]P=0.7, [M
gO]M=37.9%, [SiO2]M=87.6%, B, A and WL relationship diagram. Figure 4 shows [Si] P = 0.7, [MgO] M = 37.9
It is a relationship diagram between B and WM when %[SiO2]M=37.6%. X...MgO 78% dolomite brick, y...MgO
90% dolomite brick, 2...MgO 98% magnesia brick.

Claims (1)

[Claims] 1. In a pure oxygen top-blown converter for steelmaking lined with a refractory containing MgO and CaO as main components, coal and magnesium silicate minerals are added so as to satisfy the above two equations. A method for reducing the wear rate of refractory lining in a converter, which is characterized by adding it to the inside of the furnace. However, WL: Coal amount (ton) WM: Magnesium silicate mineral amount (ton) [MgO]M: MgO content of magnesium silicate mineral (%) [SiO2]M: SiO2 content of magnesium silicate mineral (%
) WP; Amount of hot metal (ton) [Si]p; Si content in hot metal (%)