What are the specific components and manufacturing processes 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. Its composition and manufacturing process directly affect its performance and application effectiveness. The following is a detailed description of its specific composition and manufacturing process:

1、 Specific components

Refractory aggregate

High hardness materials: fused alumina (white corundum, brown corundum), silicon carbide, fused zirconia corundum, sintered high alumina alumina, etc., accounting for 70%~80%.

Particle size distribution: Multi level particles (coarse aggregate 5-20mm accounts for 35%~45%, fine aggregate 0.15-5mm accounts for 30%~35%) are used to achieve tight packing, improve wear resistance and strength.

Powder and admixture

Fine powder: corundum powder, high alumina powder, silica micro powder (smoke dust silicon), chromium oxide micro powder, etc., with a fineness of ≤ 0.088mm, accounting for 10%~25%.

Functional additives: such as silicon carbide (to improve wear resistance), zircon micro powder (to enhance corrosion resistance).

binder

Hydraulic binder: high-purity calcium aluminate cement (with low CaO content, reducing high temperature performance loss), ρ - Al ₂ O3 (without calcium binding, excellent high temperature performance).

Chemical binders: phosphate, water glass (air hardening, acid resistant and wear-resistant).

admixture

Dispersant: High efficiency water reducing agent (such as polycarboxylate salt) optimizes fluidity.

Enhancer: Stainless steel fiber (resistant to mechanical impact), explosion-proof fiber (prevents baking and bursting).

2、 Manufacturing process

Raw material pretreatment

The aggregate is crushed and screened to the target particle size, and the powder is ground to the ultrafine powder level (≤ 0.088mm).

Ingredients and Mixing

Dry mixing: Mix aggregates, powders, binders, and additives in proportion for 2-3 minutes to ensure uniformity.

Wet mixing: Add 5%~6.5% clean water (or specified liquid) and stir until the flowability meets the standard (vibration construction type requires a slump of 80-120mm).

Construction and Forming

Pouring/vibration: After pouring into the mold, compact it by vibration to avoid layering or porosity.

Prefabricated parts: Some parts need to be prefabricated and fired at high temperatures (such as heating furnace slide rail bricks that need to be fired at 1500 ℃).

Maintenance and baking

Maintenance: Wet curing at room temperature for 5-7 days (covered with wet burlap bags), or steam curing to accelerate hardening.

Baking: Slowly bake according to the heating curve (such as 50 ℃/h) to 300-600 ℃, eliminate free moisture, and prevent cracking.

3、 Key process control points

Moisture control: Excessive water addition can lead to an increase in porosity and a decrease in strength.

Particle size distribution: The compact packing design (where the gaps between coarse and fine aggregates and powder complement each other) is the core of wear resistance.

High temperature performance optimization: Reduce the formation of low melting phases by using low cement (CaO<2.5%) or no cement (ρ - Al ₂ O3 bonding).

4、 Typical formula example (for circulating fluidized bed boilers)

Aggregate: 60% fused alumina+15% silicon carbide

Powder: 10% silica micro powder+8% pure calcium aluminate cement

Additive: Steel fiber 2%+dispersant 0.5%.

By optimizing the composition and process, wear-resistant and refractory castables can achieve a room temperature wear of ≤ 10cm ³ (ASTM704C) and a high temperature service temperature of over 1500 ℃. The specific formula needs to be adjusted according to the application scenario (such as CFB boilers, metallurgical furnaces).