Yes, white corundum can be used for sandblasting high-speed steel (HSS) products, but its application requires careful matching with the material properties of HSS (high hardness, high toughness, often used for precision components like cutting tools and molds) and sandblasting objectives (e.g., removing oxide scales, deburring, or surface roughening for pretreatment). The right type, grit size, and process parameters of white corundum must be selected to avoid damaging the workpiece or compromising subsequent processing accuracy.
I. Why White Corundum Is Suitable for HSS Sandblasting: Core Compatibility
High-speed steel typically has a hardness of HRC 60–65 (equivalent to Mohs hardness ~6.5–7.0), while white corundum has a much higher Mohs hardness of 8.8–9.2. This hardness advantage allows it to effectively remove surface oxides, rust, casting/forging burrs from HSS, or achieve controlled surface roughness (Ra) for pre-coating or electroplating preparation.
Additionally, white corundum offers other compatible benefits:
- High purity: Low impurity content (e.g., Fe₂O₃, SiO₂), especially for fixed-furnace white corundum (Al₂O₃ ≥ 99.5%). This prevents residue on the HSS surface after sandblasting, avoiding negative impacts on subsequent heat treatment, coating adhesion, or component precision.
- Controllable angularity: The angularity of white corundum particles can be adjusted via crushing processes (e.g., tilting-furnace white corundum has slightly rounder particles, while fixed-furnace white corundum is more angular). This allows selection of “aggressiveness” tailored to HSS sandblasting needs.
- Good chemical stability: It does not react chemically with HSS (mainly composed of Fe, Cr, Mo, W, etc.), preventing surface corrosion or discoloration after sandblasting.
II. Key Selections: White Corundum Type, Grit Size, and Process Parameters
The core goal of HSS sandblasting is often “efficient impurity removal + no damage to substrate precision,” so parameters must be selected strategically:
1. White Corundum Type: Prioritize “Tilting-Furnace White Corundum”
Comparing fixed-furnace and tilting-furnace white corundum, tilting-furnace white corundum is more suitable for HSS sandblasting for the following reasons:
- It has finer crystals (<50 μm) and slightly looser structure, offering better toughness (less prone to cracking into sharp debris). This reduces the risk of scratching the HSS surface, making it ideal for precision HSS components (e.g., tool edges, mold cavities).
- It is more cost-effective than fixed-furnace white corundum, making it suitable for mass sandblasting of HSS workpieces (e.g., standard cutting tools, general-purpose molds).
- For HSS with extremely thick oxide scales or hard burrs (e.g., large forged HSS parts), a small amount of fixed-furnace white corundum can be mixed (to leverage its high hardness for faster impurity removal). However, sandblasting pressure and distance must be strictly controlled to avoid excessive impact.
2. White Corundum Grit Size: Choose Based on Sandblasting Objectives
Grit size determines the surface roughness of HSS after sandblasting and the efficiency of impurity removal. Common selections are as follows:
| Sandblasting Objective | Recommended Grit Size (Mesh) | Characteristics & Application Scenarios |
|---|---|---|
| Removing thick oxide scales/stubborn burrs | 24#–46# (Coarse Grit) | Large particles with strong impact; suitable for initial sandblasting of HSS forgings/castings to quickly remove thick rust or large burrs. |
| General impurity removal + surface roughening pretreatment | 60#–100# (Medium Grit) | Balances impurity removal efficiency and surface roughness; suitable for routine cleaning of HSS (e.g., oxide scale removal after heat treatment) or pre-coating preparation (Ra 1.6–6.3 μm). |
| Precision deburring + fine surface finishing | 120#–200# (Fine Grit) | Fine particles with gentle impact; suitable for deburring precision HSS components (e.g., tool edges, mold cavities) without damaging edge sharpness or cavity precision. Results in a smoother surface (Ra 0.8–1.6 μm). |
3. Sandblasting Process Parameters: Avoid Damaging HSS
Although HSS is hard, precision components (e.g., tools, gauges) have strict requirements for surface integrity. The following parameters must be controlled:
- Sandblasting pressure: Recommended 0.3–0.6 MPa (low pressure for precision parts, high pressure for rough-machined parts). Pressures exceeding 0.8 MPa may cause plastic deformation or microcracks on the HSS surface, reducing service life.
- Sandblasting distance: Recommended 150–300 mm. Distances <100 mm lead to excessive local impact, while distances >400 mm reduce sandblasting efficiency.
- Sandblasting angle: Recommended 45°–60° inclined sandblasting. Avoid 90° vertical sandblasting, as it easily creates dents on the workpiece surface (especially for thin-walled parts or tool edges).
- Abrasive humidity: Control white corundum moisture content <0.5%. Damp abrasives tend to clump, leaving water stains or causing secondary rust on HSS after sandblasting. Use dry compressed air with dry abrasives.
III. Precautions: Avoid Common Issues
- Pretreatment cleaning: Remove oil from the HSS surface (e.g., wipe with alcohol or acetone) before sandblasting. Oil mixed with white corundum will leave residues, affecting subsequent processing.
- Post-treatment protection: Sandblasting increases HSS surface roughness, making it prone to moisture adsorption. Conduct rust prevention promptly (e.g., spray rust-inhibiting oil, dry and seal) to avoid rusting.
- Avoid sandblasting special components: For precision HSS gauges (e.g., micrometer measuring heads) or sharpened tool edges, avoid sandblasting (or use extremely low pressure + fine grit). Sandblasting may damage dimensional accuracy or edge sharpness—chemical polishing or ultrasonic cleaning is more suitable for these parts.
Summary
White corundum is an excellent choice for HSS sandblasting. Tilting-furnace white corundum (medium-fine grit, 60#–100#) is preferred, paired with “low pressure, medium distance, inclined angle” parameters. This achieves efficient impurity removal and roughening while protecting the precision and service life of HSS. For extremely thick oxide scales or cost-sensitive projects, adjust the white corundum type and grit size flexibly, with the core principle of “no substrate damage.”
