Recommended refractories for soaking furnaces

The refractory materials for building furnaces are gradually changed from refractory bricks to amorphous refractory materials, and the service life of the furnace body has been greatly improved. The upper single-side burner heat exchange soaking furnace (see picture) has the advantages of compact furnace pit layout, large ingot loading, good steel burning quality, high fuel utilization rate and easy automatic control. It is an important furnace for today's development. type.

1. Refractory material for furnace body The furnace body is composed of furnace bottom, furnace wall and furnace cover, which is square or rectangular, also known as furnace pit. Furnace walls are divided into side walls and end walls. Depending on the height of the ingot, the furnace wall height is generally 3 to 5m, and the wall thickness is about 580mm. When the furnace wall is high. Tensile bricks or metal anchors should be arranged in the middle and upper parts of the wall to enhance the stability of the furnace wall. Furnace wall refractory bricks are quickly damaged by high temperature, sudden temperature change, slag erosion, and mechanical wear and collision of steel ingots by loader clamps. Therefore, the service life of the furnace wall is the service life of the soaking furnace. The middle and lower parts of the furnace wall are generally built with silica bricks. The strength and softening temperature of silica brick are high, the thermal expansion rate above 760℃ is small, and the volume stability is good.
In addition, a thin metamorphic layer is formed on the surface, and no structural peeling occurs, so the service life is long, generally 1 to 2a. At the bottom of the furnace wall, a protective layer of magnesia-carbon refractory bricks or magnesia-chrome bricks should be built to resist the erosion of iron oxide slag. The upper part of the furnace wall is generally built with clay bricks and high-alumina refractory bricks, and sand-sealing bricks are built on top of it, and quartz sand is installed inside to facilitate the insertion of sand-sealing knives around the furnace cover to ensure the tightness of the furnace pit. When the furnace wall is built with high-alumina refractory bricks, the service life of the upper single-side burner soaking furnace used for slagging operation is about 2a. When large-scale prefabricated blocks of phosphoric acid or water glass refractory castable are used in the middle and upper parts of the furnace wall, mechanized hoisting can be realized, the construction speed is fast, the labor intensity is low, and its service life is improved compared with clay refractory bricks.
High-alumina refractory plastics or clay combined with high-alumina refractory castables are used together with high-alumina anchoring bricks with a center distance of 400-600mm. They are rammed or poured into furnace walls on site, with good integrity and high high temperature strength. , Strong peeling resistance, service life is generally 3 ~ 6a. Since 1990, the furnace mouth and other parts have been poured with corundum mullite refractory castable, ultra-low cement or cement-free refractory castable, and its service life has exceeded 2a. Below the end wall, there is an exhaust gas port, that is, the entrance of the flue. Generally, refractory bricks or unshaped refractory materials are used to make an arch to facilitate the vertical load of the furnace wall and ensure its good working condition. The thickness of the furnace bottom is generally 640-800% 26mdash; mm, and it is generally built with clay heat-insulating refractory bricks and clay bricks.
The bottom of the furnace is subjected to loads such as steel ingots and hearth materials, and is also affected by high temperature and slag. The bricks used for the working layer vary with furnace types and operating conditions. When liquid slag discharge is used, the working layer of the furnace bottom is built with magnesia bricks or magnesia chrome bricks, and one furnace can be used. When dry slag discharge is used, the working layer of the furnace bottom is built with high-alumina refractory bricks, and a layer of serpentine or olivine hearth material with a thickness of 400-500mm mixed with a small amount of coke particles is removed to facilitate the placement of steel ingots and dischargers. scum. The furnace bottom generally uses 1 to 3 furnaces. The center of the furnace bottom center of the burner soaking furnace is made of high-alumina refractory bricks to form a combustion port, which is 400-800mm higher than the furnace bottom.

2. Refractory material for furnace cover The furnace cover is composed of a metal frame, a refractory lining and a heat-resistant steel sand sealing knife. The furnace cover is divided into two types: arch type and hanging flat roof, which are opened and moved by the uncovering machine for loading and discharging. The furnace cover lining is easily damaged by mechanical vibration, sudden temperature change and high temperature flame erosion. Therefore, clay refractory bricks or high-alumina refractory bricks with good thermal shock resistance are generally used as linings. The furnace cover of the center burner soaking furnace is directly scoured by high temperature flame and air flow. The operating temperature is high, and the slag can reach about 1500 ℃. The life of the cover of the dry slag soaking furnace is about 1a. The furnace cover of the single-side upper burner soaking furnace is poured as a whole with high-alumina refractory castables with a density of about 1.8g/℃m3, and high-alumina hanging bricks with a spacing of 300mm are embedded in the lining. The lining body is light in heat insulation, small in heat capacity, energy saving, small in vibration, and has a service life of more than 1a. When high-alumina refractory plastics or clay-bonded refractory castables are used to make working linings, the upper surface is used as a thermal insulation layer, which not only saves energy, but also increases the service life to more than 2a. The burner brick is used in conjunction with the burner to organize the flame and stabilize the combustion. The burner brick is an important part of the single-side upper burner soaking furnace and the four-corner burner soaking furnace. The former is installed on one side of the end wall of the furnace pit, and the lower part is provided with a waste gas port, and the flame or airflow moves in a U-shape in the furnace; swirling airflow. The burner brick is in the shape of a bell mouth, and its structure is suitable for secondary hot air combustion, so its size and quality are relatively large. Generally, it is composed of 2 or 4 clay bricks or high-alumina refractory bricks, and phosphoric acid or low-cement series refractory bricks can also be used. The castable is made and built into the furnace wall. Under normal operation, the service life of the burner brick is 8 to 15 months.

3. Refractory material for regenerator The regenerator is an important part of the regenerative soaking furnace, and it communicates with the exhaust gas ports at the lower part of the walls at both ends of the furnace pit. The surrounding walls, shared partition walls and shared vaults of the regenerator are generally built with clay refractory bricks. Partition wall masonry must be tight to prevent collusion between gas and air. Each interior is lined with clay checker bricks to increase thermal storage capacity. The upper part of the checkered brick masonry should be made of high-alumina checkered bricks to resist the chemical erosion of smoke and dust.

4. Refractory material for heat exchanger The heat exchanger is an important part of the bottom center burner soaking furnace, the four-corner burner soaking furnace and the upper single-side burner soaking furnace, and is used to preheat air or gas. The heat exchangers of the first two types of furnaces are arranged outside the side walls of the furnace pit, and the latter type is arranged outside the end wall where the burners are installed, both located in the flue and communicated with the furnace through the exhaust gas port. The lining of the heat exchanger is built with clay refractory bricks, and the brick types include four-hole clay special-shaped refractory bricks, circular or octagonal clay or clay silicon carbide tube bricks, etc. Its characteristics are that the preheating temperature of air and gas is high, but the air leakage rate is large, and the service life is about 1a. When high-alumina silicon carbide refractory castable is used, the circular tube brick is formed by centrifugal method, the length of which is more than 2m, the air leakage rate is reduced due to the few joints, and the service life is also increased by about 50%.

5. Refractory material for flue and chimney The flue and chimney structure and lining material of the soaking furnace are the same as those of the heating furnace.