The use of the fourth generation of sialon carbon-nitrogen high-strength composite materials for the overall pouring of the blast furnace cylinder, the fundamental solution to the traditional masonry brick lining complex construction, gas and other problems, widely used in blast furnace cylinder maintenance, new blast furnace cylinder design, greatly improve the construction efficiency at the same time, reduce the cost of repair. At present, some of the domestic blast furnace maintenance, furnace cylinder pouring has been extended to the furnace belly, furnace waist and other parts.

01 Advantages of the overall casting technology for the furnace cylinder

According to the different working conditions of each part of the blast furnace, the different reasons for the erosion of each part, the blast furnace lining material will have different degrees of corrosion, the general use of thermal repair method to quickly repair the blast furnace lining; and the furnace cylinder lining, take a short-term stop furnace overall pouring way to repair. The overall casting of the furnace cylinder is a typical application of amorphous castables, and its application environment is even more complicated than that of the blast furnace body. Therefore, for materials and processes, factors such as operating environment temperature, mechanical erosion, and chemical erosion should be considered. On the one hand, the working lining is protected by hanging slag, and on the other hand, the material needs to have the best performance.

There are usually two schemes for furnace cylinder maintenance: combined brick building and furnace cylinder integral pouring. The former is usually used for the design of new blast furnace hearth, while the latter is often used for medium repair process hearth repair. In recent years, the new blast furnace also generally adopts the overall pouring method to design the hearth lining, from the following aspects:

(1) the combination of brick masonry, prefabrication cycle is long, and need to be pre-built, processing is difficult;

(2) Tuyere combination brick, brick type design is relatively complex, masonry is difficult, prone to masonry deviation, resulting in late start-up gas;

(3) the combination of brick materials, and can not form an effective slag iron viscous layer, along the brick lining service life is low.

West China furnace cylinder overall casting (patent number: ZL 201610353176.4), the use of West China fourth generation Sialon carbon and nitrogen high-strength composite materials, through the mold casting method to repair the furnace cylinder lining, the overall construction period of 7 days, its advantages are:

(1) eliminate the ceramic cup two big gap (ceramic brick between the gap, ceramic cup and carbon brick between the gap), to prevent water vapor, alkali metal and other harmful elements erosion carbon brick, effective protection of carbon brick;

(2) The high temperature sharp temperature drop zone can be left in the castable, the temperature inside the carbon brick is reduced to below 800 ℃, the thermal stress in the carbon brick is reduced, the appearance of the carbon brick ring crack and the brittle layer is reduced, and the thermal conductivity of the carbon brick is maintained. In the application of blast furnace longevity, as long as the thermal conductivity of blast furnace carbon bricks persists, without losing thermal conductivity due to ring cracking and embrittlement, the longevity of blast furnace is guaranteed;

(3) The castable for the furnace cylinder has good slag hanging property, and can form a stagnant layer on the hot surface, which can further protect the carbon bricks for the furnace cylinder. The semi-thermally conductive castable for furnace cylinder pouring is closely bonded with the carbon bricks. Heat can be transferred to the cooling wall through the carbon bricks with high thermal conductivity, and the temperature of the casting layer can be reduced to below 1150 ℃, thus forming an iron-carbon solidified layer to protect the castable, and then the castable protects the composite slag skin mechanism of the carbon brick.

02 the fourth generation of Sialon carbon nitrogen high strength composite castable

(1) The use of metal (Si/Al) ductility to achieve plastic forming, the use of nitriding and reducing atmosphere in the blast furnace to achieve the use of in situ synthesis of high-temperature enhanced phase (Si3N4/SiAlON), and non-oxide substrate to form a perfect mosaic structure, while achieving:

◆ Excellent resistance to chemical erosion

The use of the process with self-repair function

◆Good thermal shock resistance

(2) With the metal-non-oxide composite material system as the substrate, through non-oxide surface modification, the use of sol-gel molding process to achieve:

◆Good liquidity

◆Fast drying performance

◆ Overall stability after drying

Huaxi Science and Technology's fourth-generation Sialon carbon-nitrogen high-strength composite castable solves the defects of traditional binder binding castable. It has excellent wear resistance, good chemical stability, higher flexural strength, better thermal conductivity, and high-quality slagging ability.

The whole pouring process and effect of 03 furnace cylinder

1. Pouring and repairing the carbon bricks with local erosion on the side wall of the furnace;

2, furnace bottom leveling, set up springboard for pouring, pouring furnace bottom coaster;

3. Build formwork on the side wall of the furnace cylinder and pump pouring;

4. Use 1500mm high formwork for thickening casting in the iron mouth area;

5. Demoulding shall be carried out after 8 hours of curing after pouring;

6. Oven according to the provided oven scheme.

04 Furnace Cylinder Pouring Tuyere Expansion Problem

The integral pouring technology of tuyere belt was originally applied to the rapid maintenance of blast furnace. After the furnace was started, the problem of gas blow-by or failure to "withdraw the middle sleeve" occurred, which was the reason why the material expansion was not properly handled during the pouring process. These two cases are derived from:

(1) If there is no expansion joint between the middle sleeve and the castable, the problem of "against the wind sleeve" of the cast body expansion will occur, and the wind sleeve will become warped, which will make the process of "retreating the sleeve" difficult, and blow-by will occur after installation;

(2) An expansion joint is set between the middle sleeve and the castable. If the expansion joint is not set properly, the problem of blow-by at the tuyere after the furnace is started will occur, which is the most common problem.

In view of the above problems, the common solution is to use asbestos rope to wind the tuyere middle sleeve, or use ceramic fiber blanket to wrap the tuyere middle sleeve to offset the expansion of the pouring body, and then use the method of blocking the material and cold surface grouting at the top of the middle sleeve to solve the problem of blow-by in the tuyere. As mentioned above, the material itself has a metal phase absorption expansion, so the tuyere pouring technology has been more mature, and the various problems caused by material expansion have been completely solved.

05 Application Expansion

The application of the whole pouring technology of Huaxi furnace cylinder has been widely used in the maintenance of large, medium and small blast furnaces in recent years. The maintenance cycle is short, using this short and fast maintenance method, efficient and long life. The following list two kinds of expansion applications:

1. West China cooling wall hot surface pouring technology (patent number: ZL 201811449733.8)

Huaxi's original new cooling wall hot surface casting technology has two construction methods, one is to cast the mold outside the furnace, the other is to cast the mold inside the furnace, combined with the actual situation on site to decide to use the outside pouring method.

The cooling stave hot surface pouring technology takes advantage of the respective advantages of metal materials and non-metallic materials. It has excellent performance, easy slag skin, and convenient installation and use on site. It can form slag skin well for the hot surface of the cooling stave and improve the protection of the cooling stave. Performance, fundamentally solve the problem of water leakage and damage of the cooling system, greatly increase the service life of the cooling stave, and realize the efficient, safe and stable operation of the blast furnace.

2, Huaxi integrated whole furnace pouring technology (patent number: ZL2020109906820) is a new type of long-life blast furnace hearth overall pouring technology, according to the different parts of the blast furnace erosion mechanism, the use of a variety of carbon-nitrogen composite pouring materials. The whole pouring molding, seamless docking, prevent wear iron corrosion resistance is good, furnace cylinder pouring layer and ring carbon brick contact, thermal conductivity is very high. It is one of the signs of the development level of blast furnace long-life ironmaking technology, and it is the most efficient and effective method for intelligent lining, energy saving and consumption reduction.

06 Conclusions

The overall pouring technology of the furnace cylinder of Huaxi Science and Technology has been widely used in blast furnace maintenance and new blast furnace design. This paper briefly introduces the process and the pros and cons, briefly as the following conclusions:

(1) The furnace cylinder is cast as a whole, which fundamentally solves the complex construction and gap problems of traditional masonry brick lining;

(2) The fourth generation of West China Sialon carbon and nitrogen high-strength composite materials, after continuous research and development and improvement, more suitable for the furnace operating environment, longer life;

(3) New blast furnace lining design, after a comprehensive comparison, more and more choose the overall casting method to make lining;

(4) The application of blast furnace integrated whole furnace pouring can effectively improve the operating life of blast furnace lining, which is conducive to the efficient and safe operation of blast furnace.