JPS6086205A - Reparing method of bottom of converter - Google Patents

Abstract

PURPOSE:To repair the bottom of a converter speedily by charging a basic refractory material-based aggregate and repairing material composed of carbon resin into the bottom of a converter and blowing in oxygen from above. CONSTITUTION:Magnesia, dolomite, etc. are used as basic refractory material- based aggregate and also approx. 2-30wt% of carbon resin is used against the total quantity of aggregate of coal-based pitch, asphalet pitch, etc. Approx. less than 10wt% of wetting agent (ethylene glycol, etc.) against the total quantity of aggregate is added to a repairing material consisting of aggregate and carbon resin. After this procedure, this mixture is charged into the bottom of a converter with oxygen injected from above thus to effect repairs. It is possible to add carbon material (natural graphite, etc.), antioxidant (aluminum, etc.) and fibers (stainless steel fiber, etc.) to the repairing material, if necessary.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a method for repairing the bottom of a converter.

(Object of the Invention) The recently developed top-bottom blowing converter blows oxygen from the upper lance and at the same time blows oxygen and other gases from the tuyere at the bottom of the furnace. Molten steel yield and alloy yield are improved compared to furnaces.

However, in this converter, the area around the tuyeres at the bottom of the furnace is severely damaged due to the stirring action of the molten steel due to gas injection and the oxidation caused by oxygen gas. Therefore, repairs have been carried out using monolithic refractories, but conventional materials have sufficient durability and are difficult to repair, resulting in a reduction in the operating rate of the converter due to the time required for minor repairs.

The present invention aims to solve the above-mentioned conventional problems by providing a method for rapid repair using a repair material with excellent durability.

(Structure of the Invention) The present invention provides a repair material made of aggregate mainly made of a basic refractory material and carbon resin when the bottom of a converter is being heat-retained. This is a method for repairing the bottom of a converter furnace, which is characterized by charging oxygen into the bottom of the converter and spraying oxygen from above.

First, the repair material will be explained. The main aggregates are basic refractory materials such as magnesia, dolomite, calcia, maguro, and spinel. If necessary, a small amount of a known refractory material such as silicon carbide or silicon oxide may be added.

Carbon resin melts due to the heat retention at the bottom of the furnace during repair, and after the volatile matter has dissipated, residual carbon provides strength and corrosion resistance to the repair material through the action of carbon bonds.

Although the addition ratio is not particularly determined by ISa, it is preferably 2 to 30 w in terms of outer weight relative to the aggregate. 2wt% less than a
The effect of the addition is insufficient in phrases. 30 wt%'(i'
: If it exceeds this, the proportion of aggregate will decrease accordingly, and conversely, the corrosion resistance and two strength properties will tend to decrease, and the oxidation resistance will also be unfavorable.

□ Examples of carbon resins include coal-based pitch, petroleum-based pitch,
Examples include asphalt pitch, phenolic resin, furan resin, and epoxy resin.

In addition, carbon materials and antioxidants as necessary.

Fibers and the like may be added. Addition of Ao carbon material can further improve the corrosion resistance of the repair material due to its low wettability with molten steel.

Examples of carbon materials include natural graphite, artificial graphite, and Pitchco.
coke, carbon black, foundry coke.

'18: One or more types of polar debris. The addition ratio is preferably 4.0 wt% or less based on the aggregate. 40w
If it exceeds t%, oxidation resistance decreases.

Aluminum and silicon are antioxidants.

Examples include metal powder other than magnesium, ferrosilicon, or solera alloy, boron carbide, and boron oxide.

A preferable addition amount is 8 wt% or less, preferably 05 to 6 wt%, based on the external weight of the refractory material.

As for the fibers, stainless steel fibers are preferable from the viewpoint of heat resistance. Although the appropriate amount to be added depends on the dimensions of the fiber, it is preferably 1°wt% or less.

In order to make it easier to fill the repair material into the repaired area, it is preferable to add a wetting agent that has the effect of imparting cohesive force to the repair material. Examples of wetting agents include one or more of polyhydric alcohols such as evaporated ethylene glycol, glycerin, and propylene glycol, mineral oils such as anthracene oil and kerosene, and vegetable oils such as coconut oil and rapeseed oil.

The amount added is preferably 0.5 to 5 wt. When the weight exceeds 10 wt, the porosity of the repair material becomes high and corrosion resistance tends to decrease.

Instead of using a wetting agent, the repair material may be heated and kneaded in advance to form a lump by melting the carbon resin. However, it is difficult to manufacture because it is difficult to mix without heating and kneading.

Repairs are carried out after the molten steel has been discharged from the converter, while the bottom of the furnace is still warm. This table is used to melt the carbon resin in the repair material, flow and diffuse the repair material, and make it adhere. Therefore, it is preferable for the heat retention to be such that the surface temperature is 500'C or higher.

Repairs must be carried out without clogging the tuyere provided at the hearth bottom. For this purpose, from the hearth tuyere ■・PG
If the repair material is put in while blowing out gas such as , oxygen, or diluted oxygen, the area corresponding to the siding can be repaired without being blocked.

There is also a method of filling the repair material with a tuyere forming member inserted and then pulling out this member to form the entire tuyere.

When the repair material is put in, the heat retention at the bottom of the furnace melts the carbon resin, and its flow diffusion and wettability allow the repair material to adhere to the repaired area. After a certain period of time, the volatile content of the carbon resin and the solvent will dissipate and the aggregate will be bonded to carbon. However, in the present invention, by spraying oxygen from above, the temperature of the repair material is increased and the volatile content and solvent are dissipated. It promotes carbonization through dispersion and greatly reduces repair time.

For blowing oxygen, an existing oxygen lance provided for blowing oxygen into the molten steel can be used. Oxygen pressure and flow rate are determined by the heat retention temperature at the bottom of the furnace.

It is a partial cross-sectional schematic diagram of the converter hearth bottom, which is appropriately determined depending on the repair thickness, the material of the repair material, etc. (]) id hearth lining,
(2) is a large tuyere, (3) is a repair material filled in the damaged area, and (4) is an oxygen lance.

(Example) Example 1 Compounding composition of repair material Magnesia clinker-4~1mi 50wt%tt 1
．． H or less 50wt% Pitch Outer hook 20wt% Ethylene glycol /l 5wt% After using a top-bottom blowing converter for 3 charges, the surface of the bottom of the furnace is heated to 1000°C, and the above damage is applied to the damaged area around the tuyere. Added repair material. This injection was carried out while blowing out gas from the tuyere so as not to block the tuyere.

Next, the oxygen lance was lowered and kept at a position 2 m from the bottom of the furnace, and oxygen was sprayed. The repair material was oxidized by oxygen and the volatile matter ignited, increasing the surface temperature and promoting carbonization.

Example 2 Compounding composition of repair material Magnesia clinker - 14~1mm 50wt11mm
Below 45wt% silicon carbide 1 wt ratio or less Swt ratio pitch outer 10wt% pitch coke // 4w 1% glycerin /7 3wt metal aluminum powder // 1 wj ratio or more was transferred in the same manner as in Example 1 The bottom of the furnace was repaired.

Example 3 Compounding composition of repair material Dolomite clinker-4~], tnm 40wt% Magnesia clinker-4~Jim 30wt%〃111Im
Less than 30wt% Pitch Outer 20wt% Carbon black tt Swt Kerosene // 4wt Stainless steel fiber // 1-wt Stainless steel fiber // 1wt% (SU
S430) The bottom of the converter furnace was repaired in the same manner as in Example 1 using the repair materials listed above.

Example 4 Compounding composition of repair material Magnesia clinker-4~]-mm 5C1vt%y
lw or less 40wt natural phosphorous lead ]Owt thiphenol resin Outer layer 1.5wt% Propylene glycol 5wt% Al-Mg alloy The bottom of the furnace was repaired.

Example 5 Compounding composition of repair material Dolomite clinker - 4 to 1 mm 25 wt% 1 mm or less 25 wt% Magnesia clinker - 4 to 1 mm 25 wt% III
I+11 or less 25 wt pitch Outer pitch 20 wt The compounded composition described above was heated and kneaded at 250°C to obtain a lump the size of a kobushi.

The bottom of the converter furnace was completely repaired in the same manner as in Example 1 using the repair materials described below.

Comparative examples are those in which the repair materials shown in each example are used, but oxygen gas is not sprayed during repair, and the results of comparing the durability and repair time are shown in the following table.

(Effect of the invention) The durability of repair materials differs depending on the material, but when looking at the same material, all of the examples of the present invention in which carbonization was promoted by spraying oxygen have durability compared to the comparative examples. It's improving. This seems to be because the repair material has strong carbon bonds when sprayed with oxygen, but in the comparative example, it is hardened by heat retention at the bottom of the furnace, so there is not enough carbon bonding. Although the above explanation has been made using an example of a top-bottom blowing converter, the present invention is not limited to this, but can also be applied to a top-blowing converter or a converter similar to a converter if an oxygen blowing lance is provided.

On the other hand, the repair time is significantly shortened by oxygen spraying, which greatly contributes to reducing the number of repair man-hours and improving the operating rate of the converter.

2.・Tuyere-resistant large fish 3...Repair material Preface 11

Claims (1)

[Claims] When repairing the hearth bottom of a converter, while the hearth bottom is retaining heat, a repair material consisting of aggregate mainly made of basic refractory material and carbon resin is put into the hearth bottom, and the repair material is poured into the hearth bottom from above. A method for repairing the bottom of a converter furnace characterized by spraying oxygen.