Impact of unstable basalt raw material composition on actual production and improvement measures

2025-06-20

Similar to carbon fiber and Glass Fiber, the production of continuous basalt fiber requires raw material standardization. There are significant differences in the quality and application effects of basalt fiber products from different regions. Even within the same region, variations exist in basalt from different parts of the same mine.

In practice, three main problems have been identified:

(1) Some basalt ore raw materials have a narrow drawing temperature range, which is very close to the crystallization temperature. Such raw materials tend to crystallize immediately upon drawing, destroying fiber continuity and reducing tensile strength.

(2) Some basalt ore raw materials contain a high number of high-temperature resistant crystalline particles, such as olivine and corundum, making it difficult to obtain a homogeneous melt.

(3) The Chemical composition of different batches of basalt ore raw materials varies, which affects the stability of the performance of the continuous basalt fibers produced.

To address the instability of raw material composition, based on the aforementioned points, the following measures can be taken for improvement:

Select high-quality basalt ore raw materials. Basalt ore should be homogeneous, have a low degree of crystallization, no large phenocrysts, few fissures, low weathering, and no external impurities like quartz and chert. The chemical composition of the basalt ore should be within a reasonable range. Additionally, it should have a suitable acidity coefficient ( $M_{a}$ ) in the range of $3.5 \sim 5.8$ , and a viscosity ( $l g η$ ) of $0.5 \sim 1.4 Pa \cdot s$ . The viscosity ( $η$ ) of silicate melts is a function of temperature, pressure, and composition, and can be represented by the Arrhenius equation: $l g η = l g η_{0} + E_{η} / RT$ , where $η_{0}$ is a constant (pre-exponential factor) and $E_{η}$ is the activation energy of viscous flow for the melt. Basalt ore should maintain a wide temperature range during the drawing process, which makes melting and drawing relatively easy, and it should contain virtually no high-temperature resistant crystalline particles such as olivine and corundum.
Strengthen raw material homogenization. Qualified raw materials are crushed, screened, and homogenized using specialized equipment before being sent to the pre-kiln silo. To ensure the quality of the ore raw materials, the particle size must be kept largely consistent. Overly large particles can lead to melting difficulties, while overly small particles may reduce the quality of the melt.
Blend high-quality basalt ore raw materials. Due to the complex composition of natural basalt ore, with various minerals associated and coexisting, and different minerals having varying melting points, whether the raw material is completely homogeneous is one of the decisive factors affecting the drawing outcome. To better melt the material and improve the stability of the resulting fiber's performance, some production enterprises have adopted the "artificial batching" method, borrowing from glass fiber production. This involves preparing raw materials according to standards, selecting high-quality pure natural basalt, and adjusting it according to standard values using a "supply what's missing" and "pure to pure" approach—for instance, supplementing calcium if it's deficient. Additionally, for products with special performance requirements, selective doping modification can be performed to ensure all performance indicators meet design requirements, such as alkali-resistant fibers, high-temperature resistant fibers, and high-strength, high-modulus fibers. This requires selecting corresponding single-component mineral materials or other basalt ores for appropriate "doping modification" of the pure basalt raw material.