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Usage conditions and masonry methods of refractory materials in various parts of the converter

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Abstract: Taking the 180t converter of a certain steel plant as an example, this article introduces the use conditions of refractory materials in various parts of the converter and the common masonry methods of the converter body, which has guiding significance for the masonry construction of other converters.

Keywords: converter; refractory material configuration; masonry; construction method

Introduction

Converter steelmaking is characterized by high production efficiency, variety, good quality, high thermal efficiency, good raw material adaptability, low consumption, low cost, low infrastructure investment, and fast construction speed. It is widely used by the steel smelting industry at home and abroad and has become one of the main methods of modern steelmaking. The magnesia-carbon brick refractory materials in the working layer of the converter are built in different locations, and the damage mechanisms and damage speeds are different. Therefore, high-quality magnesia-carbon bricks of different brands and lengths should be used in a reasonable configuration. To achieve the purpose of adapting to steelmaking requirements, increasing furnace age, and reducing the cost per ton of refractory steel. Therefore, the implementation of comprehensive masonry is an important task and effective measure to ensure the safety of converter operation and improve the age of the furnace.

This article takes the converter masonry construction of a steel plant as an example to describe the commonly used masonry methods of converters.

Refractory usage conditions and refractory configuration in various parts of the converter

Comprehensive furnace building

When the used furnace lining was removed, it was found that the damage was caused by the fact that some severely corroded parts could not be used. Although many other parts could be used, they had to be abandoned in order to build new furnace linings.

Therefore, people have put forward the concept of comprehensive furnace building and balanced furnace lining, that is, selecting furnace lining bricks of different qualities according to the erosion status of different parts of the furnace lining.

The temperature at the furnace mouth changes drastically and is severely washed away by slag and high-temperature exhaust gas. Therefore, the refractory bricks used at the furnace mouth must have high thermal shock resistance and slag resistance.

The furnace hat area is mainly affected by the erosion of gas in the furnace and the splashing of slag during blowing. It is also affected by sudden temperature changes and erosion by dusty exhaust gas. Therefore, magnesium carbon bricks with strong slag resistance and good thermal shock resistance should be used. .

The lining bricks in the furnace wall area, especially those on the charging side, are washed away by molten steel and slag, and are required to have high high-temperature strength.

The slag line and trunnion area are the most demanding parts of the converter lining. They are washed and eroded by molten steel and slag, as well as by the gas in the furnace. They require the use of bricks with the best corrosion resistance.

In converter lining, taphole brick is another type of brick with special significance. Due to the large amount of steel flowing through, the taphole of a large converter is washed away by molten steel and has very harsh operating conditions. Generally, its service life is relatively short, which is far lower than the life of the furnace lining. Therefore, the taphole bricks must be replaced frequently. Taphole bricks can be divided into integral type and segmented assembly type in terms of style. At present, it is believed that the magnesium carbon integral taphole has better performance, long life and easy replacement. During the smelting process, due to the different working conditions of various parts, the corrosion conditions of various parts of the working layer are also different. Our company adopts a comprehensive masonry method to achieve balanced erosion of the entire furnace lining. For comprehensive furnace building, 3 to 6 different grades of bricks should be selected according to the specific conditions of different manufacturers, and built on the slag line, trunnion, furnace wall, molten pool and other parts respectively, in order to obtain the best economic benefits.

Figure 1 Construction diagram of a 180t converter in a steel plant

Figure 2 Layout of furnace bottom bricks and bottom blown bricks

According to the above requirements, the configuration plan of refractory materials for a 180t converter in a steel plant is shown in Figures 1 and 2. It can be seen from Figure 1: ① Furnace mouth and furnace cap: the permanent layer is made of non-standard bricks, the working layer is made of magnesia carbon bricks with a thickness of 500~650mm, and the furnace mouth and furnace shell are knotted with castables. ② Furnace body: One layer of 115mm thick sintered magnesia bricks is built as the permanent layer, and 650mm thick magnesia carbon bricks are built as the working layer. ③ Molten pool: One layer of 115mm thick sintered magnesia bricks is built on the permanent layer, and 700 ~ 750mm thick magnesia carbon bricks are built on the working layer. ④ Furnace bottom: 2 layers of 75mm thick sintered magnesia bricks are built on the permanent layer, and 750mm thick magnesia carbon bricks are built on the working layer.

Pre-laying of furnace bottom bricks

The center brick is a truncated cone shape with a thick bottom and a thin top, and is set at the center of the furnace bottom. The long wedge-shaped bricks with a large bottom and a small top are close to the center bricks and are built in a ring after being close to each other. After the first ring of bricks is laid, the outer brick surface is rounded (to minimize the ring gap) and then the second ring of bricks is laid, and so on. Since the new brick type is laid for the first time, the new brick type must be pre-layed and pre-processed. This pre-laying is usually performed at the brick manufacturer. Use cement to make a pre-laying platform in the shape of a pot bottom according to the same dimensions as the converter bottom, simulating the entire process of building the converter bottom (Figure 3). The center of the central brick is set at the center of the bottom of the pre-laying platform. After each ring of bricks is laid, the brick shape is determined to minimize the ring joint. Cut and polish the closing door bricks, polish and shape the external brick surface, and number each ring of bricks in sequence. As shown in Figure 4. When laying on site, strictly follow the numbering.

Figure 3 Cement pre-laying platform

Figure 4 Pre-brick type number

Construction sequence and methods

Preparation before building the furnace

1) Equipment required on site: a forklift, furnace masonry hanging plate, furnace masonry loading platform, special lifting equipment, special spreaders, paddle mixer, electrical welding equipment, water and electricity facilities and special lighting.

2) Masonry workers must be equipped with tools: 2 500mm brick cutting machines (one for use and one for backup), and pneumatic hammers equipped with hammer heads of different sizes. 2 jacks over 5t, masonry tools such as trowel, sledge hammer, hand hammer, rubber hammer or wooden hammer, brush, small bucket, broom, shovel, level, level, etc.

Construction sequence and method

Construction sequence

The masonry is carried out in five parts: furnace bottom, molten pool, furnace body, taphole, and furnace cap. The masonry is built on top. The steel plate of the furnace shell is composed of permanent layer and working layer in order. The permanent lining is made of fired magnesia bricks, and the working lining is made of magnesia carbon bricks. Both magnesia bricks and magnesia carbon bricks are laid in a dry way, and key parts of the permanent layer can be laid in a wet way.

Construction methods

1) The masonry of the furnace bottom. The permanent layer is built with magnesia bricks, and two layers of standard bricks are used. The masonry adopts the “one-line” masonry method, which requires the steel shell at the bottom of the furnace to be closely connected and the brick joints to be staggered. When laying the second layer of permanent bricks, the center line should be perpendicular to the center line of the first layer. When building to the outside, use ramming material to fill the gap between the bricks and the steel plate tightly, and pound with a hand hammer or wooden board. When each layer of bricks is laid to the position of the bottom blowing air supply component, an opening is reserved, and the center point of the opening on the furnace bottom steel shell is used as the center base point to ensure that there is room for adjustment when installing the breathable bricks and to reduce the amount of brick cutting. After each layer of masonry is completed, use magnesia fire clay dry powder to spread an even layer, fill the brick joints tightly, and then sweep them with a broom. After laying the furnace bottom magnesia bricks, build the furnace bottom working layer, and install the center brick at the center of the furnace bottom. Set the starting line: Starting from the center of the center brick, the entire furnace bottom is built in a circular shape, with a total of 12 rings (excluding the center brick). When the gas supply bricks are built to the reserved holes, the gas supply bricks are installed.

2) Installation of breathable bricks. The refractory parts of the 12 breathable bricks in this furnace have the same outer dimensions. When installing, the breathable bricks should be installed at the center of the furnace shell opening as much as possible. If the position is inappropriate and cannot be installed properly even through position adjustment, the following three methods can be used to deal with it:

① When processing bricks around breathable bricks, it is required that processed bricks must not be used around breathable bricks, and the size of processed bricks must meet the masonry requirements.

② Expand the opening on the furnace shell, ensure that the bottom-blown ventilation bricks are placed on the ring, and process the furnace bottom bricks as little as possible.

③ Use the breathable brick and wood model for trial placement before installing the breathable bricks. The gaps after installation must be filled tightly with refractory materials. Care must be taken during the installation process to ensure that the tail pipe of the breathable brick is not damaged. It is required to protect the bottom blow pipe and the upper surface of the breathable brick with tape before masonry.

3) Construction of the solution pool. The furnace bottom is designed as a spherical bottom, and the molten pool and the furnace bottom are made of arc transition masonry. The gap between the working lining and the permanent lining is filled with ramming material and tamped flat with a pneumatic hammer. Refractory brick masonry should be strictly operated, and the level after 12 layers of masonry should be ensured as much as possible to lay a good foundation for the furnace body masonry. When laying each layer of bricks, ensure that the entire ring is flat and close to the furnace bottom bricks. There are 12 layers of molten pool bricks in total, which are built according to the design drawings and brick shapes. Each door needs to be cut when laminated. It is required that the cut brick shape should be reasonably large on the outside and small on the inside, and the size of the cut brick should be greater than 1/2 the thickness of the brick. The upper and lower door bricks are staggered by more than 60 degrees.

4) The masonry of the furnace body. When building the furnace body, the permanent layer is laid first, using the side-laying method, with a permanent lining thickness of 115mm, and a total of 18 layers. The working lining of the furnace body has a total of 25 layers, and the layers are staggered. Each section of masonry is laid alternately in clockwise and counterclockwise directions, and the closing bricks are measured and cut to size. The processing requirements are the same as those for molten pool brick masonry. In the design, the materials of the feeding side, the tapping side and the trunnion are different, so the masonry in this area should be laid strictly according to the markings of the bricks to avoid laying bricks of different materials incorrectly.

5) The masonry of the steel tap hole. The sleeve bricks and seat bricks are assembled and installed. The assembly should ensure that the sleeve bricks and seat bricks are concentric and the gaps are tamped firmly with ramming material. After placing the overall taphole seat bricks, lay other surrounding furnace cap bricks. Wet masonry is used around the seat bricks, and no expansion joints are left within 1m around the tap hole. After the furnace cap bricks are built 2 to 3 layers above the tap hole, fill and tighten the surrounding area of the tap hole with ramming material.

6) The masonry of the furnace cap and furnace mouth. The area between the permanent lining of the furnace cap and the steel plate is tightly packed with magnesium filler. There is no permanent lining after the 53rd to 55th layer of working lining. After the working lining is completed, there will be a 50 ~ 80mm gap under the furnace mouth cooling plate. This gap is filled with dry thick magnesia castables and plugged tightly with wooden wedges. To prevent the furnace from loosening, it is strictly forbidden to use magnesia carbon bricks to prevent expansion and deformation of the water-cooling parts.

7) Expansion seam retention method. In order to compensate for the expansion of the refractory material during the heating process of the kiln, expansion paper is inserted into the brick body. During the bricklaying work in different parts of the furnace, the placement and distribution of the inserts are different. The expansion material used is 1mm thick cardboard. For the vertical expansion joint of the furnace body, add 1 layer of 1mm yellow cardboard for every 3 layers (starting from 13th layer), and horizontally for every 6 pieces of each ring, use 1 layer of 1mm yellow cardboard. For the longitudinal expansion joint of the furnace cap, add 1 layer of 1mm yellow cardboard for every 3 layers (end after 46 layers), and for the transverse expansion joint, add 1 layer of 1mm yellow cardboard for every 6 pieces per ring (end after 44 layers).

8) Finishing work of masonry. After the masonry work is completed, lift out the masonry platform in sequence, being careful not to damage the furnace lining bricks. After the platform is lifted out, clean up the debris in the furnace and do not leave any residual bricks in the furnace. After the masonry is laid, the furnace bottom and the corner area of the molten pool are pounded with ramming materials to create a furnace slope for protection.

Summary

This article discusses the use conditions and refractory configuration of various parts of a 180t converter in a steel plant. It introduces the entire masonry process of the converter in detail according to the masonry sequence and construction methods, which has guiding significance for the masonry of other converters. Therefore, the implementation of comprehensive masonry is an important task and effective measure to ensure the safety of converter operation and improve the age of the furnace.

LMM YOTAI established in 2007. Our production technology comes from Japanese Yotai. As an experienced and international player in the refractories industry. We have succeeded in expanding both the breadth of its product range and the depth of its services. From raw material selection, refractory portofio & optimization, installation & services & recycle of used refractories on site to further reduce client’s Opex & Capex in refractory consumption per ton steel output, meanwhile improve product quality of client.

Our Product have been supplied to world’s top steel manufacturer Arcelormittal, TATA Steel, EZZ steel etc. We do OEM for Concast and Danieli for a long time

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