South African chromium ore sand, particularly foundry-grade, is widely used in the foundry, refractory, and other industries due to its excellent properties. Below, I’ve summarized its key performance indicators and related information.
🧱 1. Key Chemical Composition
The core chemical composition of South African chromium ore sand is crucial to its performance, particularly the Cr₂O₃ content and the chromium-iron ratio (Cr/Fe ratio).
Chromium trioxide (Cr₂O₃): This is the most critical component in chromium ore sand, typically containing at least 46%. A high Cr₂O₃ content is directly related to its refractoriness and slag resistance.
Silicon dioxide (SiO₂): A harmful impurity with a content requirement of ≤1.0%. Lower SiO₂ levels help improve refractory properties.
Ferrous oxide (FeO): The content is typically ≤26.5%. The FeO content affects the Cr/Fe ratio.
Chromium/Fe Ratio: This is a key indicator of chromium ore quality, referring to the ratio of chromium to iron. The Cr/Fe ratio of South African foundry-grade chromium ore typically ranges from 1.55:1 to 1.60:1. A higher Cr/Fe ratio generally indicates improved ore refractoriness, slag resistance, and strength. The high Cr/Fe ratio is the reason chromium ore from the LG formation in South Africa is so high in quality.
Other impurities: Calcium oxide (CaO) ≤ 0.30%, magnesium oxide (MgO) ≤ 10.0%, aluminum oxide (Alâ‚‚O₃) ≤ 15.5%, and phosphorus (P) and sulfur (S) content are both required to be ≤ 0.003%. Strict control of these impurities ensures the ore’s high-temperature performance and performance.
For a more intuitive comparison, please see the table below:
Composition Typical Requirements/Range Description and Impact
Crâ‚‚O₃ ≥ 46.0% This core component directly determines refractoriness and slag resistance. SiOâ‚‚ ≤1.0% Harmful impurity, requiring strict control. A low content improves refractory properties. FeO ≤26.5% Affects the chromium-iron ratio, which in turn affects overall performance. Cr/Fe Ratio 1.55:1 – 1.60:1 An important indicator. A higher ratio generally indicates better refractory properties, slag resistance, and strength. CaO ≤0.30% Impurity, requiring control. MgO ≤10.0% Impurity, requiring control. Alâ‚‚O₃ ≤15.5% Impurity, requiring control. P ≤0.003% Harmful element, requiring strict control. S ≤0.003% Harmful element, requiring strict control. 📊 2. Physical Properties
The physical properties of South African chromium ore are equally important and affect its performance in the casting process.
Bulk density: Typically between 2.5 and 3.0 g/cm³.
Bulk density: Higher, typically between 4.0 and 4.8 g/cm³. This gives chrome ore good compressive strength and stability.
Refractory:
Sintering temperature: Typically above 1800°C.
Melting point: As high as 2180°C. This indicates that South African chrome ore can withstand extremely high casting temperatures.
pH: Typically neutral to slightly alkaline, ranging from 7 to 9, making it compatible with most foundry binders.
🔬 3. Particle Size Specifications
South African chromium ore is available in a variety of particle sizes to meet specific needs:
Common domestic particle sizes: 20-40 mesh, 20-60 mesh, 20-70 mesh, 30-70 mesh, 40-70 mesh (40-70 mesh is commonly required in procurement, accounting for ≥90%), 50-100 mesh, 70-140 mesh, etc.
Common international particle sizes (AFS): AFS25-35, AFS35-40, AFS40-45, AFS45-50, AFS50-55, etc.
