What are the main components of wear-resistant and refractory castables?

Wear resistant and refractory castable is an amorphous refractory material designed specifically for high wear and high temperature environments, and its composition directly affects its wear resistance, high temperature resistance, and mechanical strength. The following is a detailed description of its main components:

1、 Refractory aggregate (accounting for 70%~80%)

Refractory aggregate is the main body of castable, providing basic wear resistance and high temperature stability. It is usually made of high hardness and high melting point materials:

Fused alumina

White corundum (Al ₂ O ∝ ≥ 99%): high hardness (Mohs 9 grade), high temperature resistance (melting point 2050 ℃), suitable for high wear parts.

Brown corundum (Al ₂ O ∝ ≥ 95%): containing a small amount of TiO ₂, with better toughness than white corundum, commonly used in metallurgical furnace lining.

Zirconia corundum (containing ZrO ₂): Excellent in thermal shock resistance and corrosion resistance, used in harsh environments such as glass kilns.

Silicon carbide (SiC)

Hardness is second only to diamond, with good wear resistance, but it is prone to oxidation at high temperatures and needs to be used in conjunction with antioxidants.

Sintered high alumina bauxite

Al ₂ O3 content is 75%~85%, with low cost, widely used in the lining of cyclone tubes in the cement industry.

Particle size distribution: Coarse aggregate (5-20mm) accounts for 35%~45%, and fine aggregate (0.15~5mm) accounts for 30%~35% to achieve tight packing.

2、 Powder and admixture (accounting for 10%~25%)

Powder filling of aggregate voids, optimizing construction performance and enhancing high-temperature strength:

Silicon oxide micro powder (smoke dust silicon)

Particle size ≤ 0.1 μ m, increased density and reduced water addition through the "micro powder filling effect".

Corundum powder/high alumina powder

Fineness ≤ 0.088mm, synergistically enhances wear resistance with aggregates.

Functional additives

Chromium oxide micro powder (Cr ₂ O3): enhances slag erosion resistance and is used in refining catalytic cracking units.

Zirconia micro powder: improves thermal shock resistance and is suitable for environments with sudden temperature changes.

3、 Adhesive (accounting for 5%~15%)

The binder determines the hardening method and high-temperature performance of the casting material, and common types include:

Hydraulic binder

Calcium aluminate cement: has high early strength, but CaO will reduce high temperature performance (such as creep resistance), and the dosage needs to be controlled.

ρ - Al ₂ O3: Calcium free binder, excellent high-temperature performance, but high cost.

Chemical binders

Phosphate: forms an aluminum phosphate network through thermal hardening, with a temperature resistance of up to 1600 ℃.

Silicasol: Sol gel combination, suitable for cementless system.

4、 Additive (small amount,<5%)

Reinforced fiber

Stainless steel fiber: enhances resistance to mechanical impact.

Explosion proof fiber: forms an exhaust channel during baking to prevent bursting.

dispersant

Polycarboxylate salts: reduce water addition and improve fluidity.

5、 Typical formula example

For circulating fluidized bed boilers:

Aggregate: sintered high alumina alumina 60%+fused alumina 20%+silicon carbide 10%

Powder: 8% silica micro powder+7% pure calcium aluminate cement

Additive: 2% steel fiber.

Heating furnace for steel trough:

Aggregate: 70% fused brown corundum+10% zircon micro powder

Adhesive: 10% aluminum phosphate+5% chromium oxide micro powder.

summary

The composition design of wear-resistant and refractory castables needs to be adjusted according to specific working conditions, such as temperature, wear medium, chemical erosion, etc. High alumina, corundum, and silicon carbide based formulations are mainstream choices, and optimization of binders and additives can further enhance performance.