What is the preparation principle of wear-resistant refractory castable?

The preparation principle of wear-resistant and refractory castables involves the selection of raw materials, particle size distribution, optimized combination of binders and additives, and strict control of production processes. The following is a detailed analysis of its core principles:

1、 Raw material selection and optimization

High hardness aggregate

Mainly using high wear-resistant materials such as corundum (Al ₂ O ∝ ≥ 85%), silicon carbide (SiC), and special grade high alumina bauxite as aggregates to ensure high temperature resistance to erosion and wear.

Aggregates need to undergo high-temperature calcination (clinker) to avoid cracking or peeling of raw materials due to unstable volume.

Micro powder and ultrafine powder

Adding silica fume (SiO ₂ micro powder), α - Al ₂ O3 micro powder, etc. to fill the gaps between aggregates, improve density and flowability, while promoting low-temperature bonding strength and medium temperature sintering performance.

Micro powder can also reduce water consumption, improve the slag penetration resistance and high-temperature strength of castables.

Binder system

Hydraulic bonding: Calcium aluminate cement (pure calcium aluminate or high-purity calcium aluminate) is a commonly used binder that forms low-temperature strength through hydration reaction.

Chemical bonding: Phosphates, water glass, etc. harden through chemical reactions and are suitable for high-temperature environments.

Cohesive bonding: The cementless system relies on the gelling effect of micro powders (such as SiO ₂+MgO) to reduce the formation of low melting phases at high temperatures.

2、 Particle size distribution and compact packing

Multi level proportioning design

Aggregates are usually made of 3-4 grade particles (0-10mm), with coarse particles (such as 3-5mm) providing skeleton support, and fine particles (<1mm) and powder filling the gaps to achieve tight packing.

The critical particle size is adjusted according to the construction thickness, for example, thicker lining bodies require larger particle sizes (such as 8-10mm) to reduce shrinkage.

Explosion prevention and volume stability

Add bluestone powder (which expands when converted to mullite at high temperatures) or clay to counteract high-temperature shrinkage.

Explosion proof agents (such as metal aluminum powder) release gas when heated, forming micro porous channels to prevent steam pressure from causing explosions.

3、 Production process flow

Raw material pretreatment

Crushing (jaw crusher), crushing (cone crusher), screening (electromagnetic vibrating screen efficiency>90%).

Fine grinding (ball mill) is used to prepare powder, ensuring a fineness of ≤ 0.088mm.

Pre mixing and ingredients

Trace additives (such as water reducers and coagulants) need to be pre mixed with the powder to ensure uniform distribution.

The electronic scale provides precise ingredients and the forced mixer mixes for 5 minutes.

Construction and maintenance

The amount of water added should be controlled between 5.5% and 6.5%, as excessive amount will reduce the strength.

Wet curing for 5-7 days (covered with wet burlap bags), baking with three-stage heating (110 ℃ to remove free water, 350 ℃ to remove crystallization water, and 600 ℃ to heat uniformly).

4、 Key Performance Control

Improved wear resistance

Silicon carbide (SiC) aggregate has high hardness (Mohs 9.5) and is suitable for extreme wear parts such as CFB boiler cyclone separators.

Steel fiber reinforcement (adding 1-3%) can improve impact resistance and peel resistance.

High temperature adaptability

The corundum based castable has a temperature resistance of up to 1650 ℃ and is resistant to acidic slag; Magnesium castables are resistant to alkaline corrosion and are used in metallurgical furnaces.

Circulating fluidized bed boilers (850-1050 ℃) require optimization of aluminum content (Al ₂ O ∝ ≥ 80%) and micro powder ratio.

5、 Typical formula example

Casting materials for CFB boilers: sintered alumina+fused alumina aggregate, calcium aluminate cement+SiO ₂ micro powder combination, SiC enhanced wear resistance.

Anti caking castable: Silicon carbide matrix, added with anti caking agent (such as ZrO ₂) to reduce cement kiln caking and cleaning damage.

Through the synergistic effect of the above principles, wear-resistant and refractory castables can achieve comprehensive performance of high strength, wear resistance, and heat shock resistance, meeting the demanding requirements of industrial high-temperature wear environments.