Category:
Mineral
Material Type:
non-metal
Alternative Names:
Tags:
Smelter Slag
Mineral
Basic Information
Composition & Structure
Composition:
Variable — CaO-SiO₂-Al₂O₃-FeO with minor MgO, MnO
Microstructure:
Amorphous glassy matrix with possible crystalline phases (melilite, spinel, wollastonite)
Description
Smelter slag is the glassy or partially crystalline byproduct of metal smelting. Metallographic examination is critical for quality control — microstructure reveals crystallization degree, entrained metal prills, and mineral phases indicating process efficiency. Preparation is challenging because the glassy matrix is extremely brittle and prone to chipping.
Mechanical Properties
Hardness:
400-700 HV (varies)
Hardness (HV):
550 HV
Hardness Category:
medium hard
Physical Properties
Density:
2.5-3.5 g/cm³
Melting Point:
1200-1500 °C
Material Characteristics
Work Hardening:
No
Magnetic:
No
Corrosion Resistance:
moderate
Sectioning
Diamond wafering blade - fine grit / low concentration. MOST CRITICAL STEP — chipping/cracking during sectioning may be impossible to remove. Very low feed rate. Never use abrasive cut-off wheels on glassy slag.
Mounting
Castable with epoxy or acrylic. Vacuum impregnation recommended for crack-filling.
Grinding
Planar grinding with semi-fixed diamond on metal mesh cloth. Do NOT use coarse SiC paper. 30μm diamond on CERMESH until plane.
Recommended Sequence:
Polishing
6μm diamond on TEXPAN with SIAMAT (5 min), 1μm diamond on GOLDPAD with SIAMAT (5 min), SIAMAT colloidal silica on TEXPAN at 100/100 rpm (5 min).
Recommended Sequence:
Etching
Examined as-polished. Polarized light is the principal technique — crystalline phases are birefringent, glass is isotropic. Reflected polarized light shows metal prills. Dilute HF (1-5%) can enhance contrast between silicate phases.
Common Etchants:
Heat Treatment
Not applicable — slag is a smelting byproduct. Microstructure controlled by cooling rate.
Standards
- ASTM C989
- ASTM E1382
Applications
- Smelting process quality control
- Slag cement production
- Road base aggregate
- Mineral wool insulation
Typical Uses
- Blast furnace iron smelting QC
- Copper smelting process control
- Steelmaking slag analysis
- Environmental compliance testing