Unshaped refractories

  • Time:Aug 23, 2023
  • Views: 10
Unshaped refractories are mainly composed of refractory aggregates, binders and additives. Refractory aggregates can be high-temperature stable granular materials such as alumina, silicon oxide, and silicon carbide. The binder is a material that binds the aggregates together by providing cohesive force. Common binders include water glass, phosphate, cement etc. Additives include plasticizers, anti-cracking agents, preservatives, etc., which are used to improve the plasticity, crack resistance and corrosion resistance of materials.

【1】 What is Unshaped Refractories

  Unshaped refractories, also known as monolithic refractories, refer to refractories that are directly constructed without going through a forming mold. Compared with traditional brick or block refractory materials, unshaped refractory materials are widely used for their flexibility, construction convenience and ability to adapt to various shape requirements.

  The construction methods of unshaped refractories mainly include the following:

  1. Castable: Mix refractory aggregate, binder and water to form a flowable slurry, then pour it into the construction site, and form a refractory layer after curing.

  2. Spraying: The unshaped refractory material is made into a sprayable paste slurry, which is sprayed onto the surface to be protected by a spray gun to form a uniform refractory layer.

  3. Infusion (Gunning): The semi-dry paste material is made from the amorphous refractory material, which is injected into the construction site through high-pressure injection or artificially, and finally a solid refractory layer is formed during the construction process.

  4. Assembly (Plastic): add an appropriate amount of water to the unshaped refractory material, stir it into a plastic shape, and directly assemble it to the desired position by hand or machine, and then dry or solidify to form a strong refractory layermore

【2】 Properties of Unshaped Refractories

  1. Application flexibility: Unshaped refractories are suitable for equipment surfaces and structural parts of various shapes and sizes. Due to its bulk or spray-on nature, it can be easily adapted to irregular surfaces, complex shapes or curved structures, providing greater construction flexibility.

  2. Refractory performance: Amorphous refractory materials have good refractory performance and can withstand thermal stress and chemical erosion in high temperature environments. They are usually made with refractory aggregates and refractory binders with higher refractory temperatures to ensure stability and durability in high temperature working environments.

  3. Good bonding performance: Unshaped refractory materials are usually mixed with special refractory binder and refractory aggregate, which can produce good bonding force and adhesion. This allows them to bond firmly to the substrate or lining surface to form a strong protective layer.

  4. Abrasion resistance: Unshaped refractory materials have certain wear resistance and can withstand mechanical wear and the impact of granular materials. This makes them suitable for working environments where resistance to abrasion or scour is required, such as iron nozzle linings, pulverized coal pipeline linings, etc. in the metallurgical industry.

  5. Corrosion resistance: Unshaped refractories have certain corrosion resistance to acid-base gases and molten metals. They resist attack from hot gases and chemicals, extending equipment life and maintaining structural integrity.

  6. Construction convenience: more

【3】 Application of Unshaped Refractories

  1. Repair and maintenance: Unshaped refractories are often used for repair and maintenance of high-temperature equipment such as furnaces, kilns, and heat treatment equipment. Due to the high plasticity and cohesiveness of the monolithic refractory, it can fill and plug cracks, worn parts or damaged areas in the furnace.

  2. Thermal insulation layer: Unshaped refractory materials can be used to construct thermal insulation layer to reduce heat conduction and loss. By coating or spraying monolithic refractories on the surface to form a thermal insulation layer, it can provide thermal insulation, reduce energy consumption, and improve the thermal efficiency of equipment.

  3. Coatings and Coatings: Unshaped refractory materials can also be used as coatings or coatings to increase the refractory properties of the material. These coatings can be applied to metal surfaces, masonry, insulation boards, etc. to provide fire protection against fire spread and heat transfer.

  4. Bonding and cementing materials: Unshaped refractory materials are often used as bonding and cementing materials to fix components such as refractory bricks, ceramic fibers, and refractory fiber felts. They can be mixed with water or specific cements to form a slurry or paste and are used to build complex shapes or join different parts of refractory structures.

  5. Fireproof Filling: Unshaped refractory materials can be used to fill voids, ducts or other spaces in building structures to provide fire insulation and protection. These fills can expand in the event of a fire and create a fire-resistant barrier, slowing the spread of fire and the spread of smokemore

【4】 Classification of unshaped refractory materials

       1. Castables: Castables are mixtures of refractory aggregates, binders, and additives that are mixed with water to form a moldable slurry. They are widely used for various applications such as lining of furnaces, kilns, and other high-temperature equipment.

  2. Ramming masses: Ramming masses are granular refractory materials that are used for lining applications by manual or mechanical ramming. They consist of refractory aggregates, binders, and sometimes additives. Ramming masses are commonly used in the construction of electric arc furnaces, induction furnaces, and other similar installations.

  3. Plastic refractories: Plastic refractories are malleable materials that can be easily formed or shaped by hand. They are composed of refractory aggregates, plasticizers, and bonding agents. Plastic refractories are commonly used for repairing or patching existing refractory linings, as well as for forming complex shapes during initial installations.

  4. Gunning mixes: Gunning mixes are dry or semi-dry refractory materials that are pneumatically applied using a gunning machine. They typically consist of refractory aggregates, binders, and additives. Gunning mixes are widely used for repairing and maintaining refractory linings in various high-temperature applications.

  5. Spraying mixes: Spraying mixes are similar to gunning mixes but have finer particle sizes and are designed for spray application. They are commonly used for coating or insulating purposes, providing thermal insulation or protection against chemical attack.

  6. Refractory mortars: Refractory mortars are specialized bonding agents used for joining refractory bricks or shapes together. They are typically composed of fine refractory powders, binders, and additives. Refractory mortars are crucial for creating strong and durable linings in various high-temperature applicationsmore

Classification of unshaped refractory materials

【5】 What kind of unshaped refractories are used in the ironmaking system

      The ironmaking system includes sintering machines, coking and blast furnaces and their ancillary equipment. The proportion of lining materials from shaped products to unshaped linings has gradually increased in recent years.

      The ignition furnace of the belt sintering machine is made of refractory plastic and high alumina refractory castables, and phosphoric acid refractory castables are also used to make prefabricated parts for hoisting construction. Corundum castables are used for the ignition device and the furnace top, and light heat-insulating castables or refractory fibers are used as linings for parts of the furnace with good working conditions.

      The heat insulation layer and the cladding layer of the coke oven roof are poured on-site with refractory castables. When the furnace head is damaged, it can be repaired with spray paint. In addition, CDQ equipment also uses heavy or light refractory castables, and the furnace door has changed from heavy castables to semi-heavy castables. Because the furnace door is frequently opened, too heavy heavy castables are not conducive to For on-site use, changing to a semi-heavy castable not only reduces the weight, but also improves the insulation effect.

<b>What kind of unshaped refractories are used in the ironmaking system</b>

      Blast furnaces use low-cement and high-alumina castables to make prefabricated blocks for hoisting and masonry, and resin-bonded aluminum-carbon non-burning bricks can be used for masonry. Silicon carbide castables are used for the construction of large-scale blast furnace water walls, low cement castables and silicon carbide fillers are used for the furnace bottom cushion and surrounding brick joints, and refractory press-in mud and refractory spray paint are used for repairs when the furnace lining is damaged. The filling between the furnace hearth and the furnace wall is injected twice with anhydrous pressure-in mud. In recent years, there are also spray coatings that are directly combined with silica sol, and are directly sprayed as linings. This is a new technology, although not many manufacturers use it, but the effect is very goodmore

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