Choosing the appropriate glass bead material for sandblasting/shot blasting treatment requires a comprehensive judgment based on factors such as workpiece material, treatment objectives (such as cleaning, strengthening, polishing), surface quality requirements, and cost. The core material characteristics of glass beads are determined by their chemical composition, which directly affects hardness, wear resistance, roundness, and the effect on the surface of the workpiece. The following is a specific analysis:
###1. Main material types and characteristics of glass beads**
The material of glass beads is based on glass and can be divided into the following categories according to their chemical composition, each with its own applicable scenarios:
1. Sodium calcium glass beads (most commonly used)**
-* * Composition * *: Mainly composed of silicon dioxide (SiO ₂), containing oxides such as sodium (Na ₂ O) and calcium (CaO), accounting for about 70% -80%.
-* * Features * *:
-Moderate hardness (Mohs hardness 6-6.5), moderate brittleness, high roundness (mature processing technology).
-Low cost, can be reused 3-5 times (easily broken after wear and tear, requires regular screening).
-* * Applicable scenarios * *:
-Conventional surface cleaning (such as removing rust, oxide scale, oil stains), deburring (metal/plastic parts).
-The treatment of soft or medium hardness workpieces (aluminum, copper, cast iron, plastic) to avoid excessive damage to the workpiece caused by hard materials.
-Pre treatment with moderate surface roughness requirements (Ra 3.2-6.3 μ m), such as roughening before painting and electroplating.
2. borosilicate glass beads (high hardness type)**
-* * Composition * *: Contains a high proportion of boron oxide (B ₂ O ∝, usually 10% -15%), silicon dioxide accounts for more than 80%, and almost no sodium, calcium or other melting components.
-* * Features * *:
-High hardness (Mohs hardness 6.5-7), strong wear resistance, better toughness than sodium calcium glass, and can be reused up to 5-8 times.
-High roundness, uniform impact, and less likely to produce sharp debris (reducing scratches on the surface of the workpiece).
-* * Applicable scenarios * *:
-Surface strengthening (such as improving fatigue strength) and fine cleaning (removing stubborn oxide layers) of hard workpieces (carbon steel, alloy steel, mold steel).
-Processing that requires precise surface roughness (Ra 1.6-3.2 μ m) for precision mechanical parts and aerospace components.
-Large scale production that requires long-term recycling to reduce costs (such as automated sandblasting lines).
3. * * High lead glass beads (special purpose)**
-* * Composition * *: Lead containing oxide (PbO) 20% -40%, with a high density (3.0-4.0 g/cm ³, higher than the 2.4-2.6 g/cm ³ of ordinary glass beads).
-* * Features * *:
-High density, high impact energy (stronger impact force for the same particle size), but hardness similar to that of soda lime glass.
-Due to lead content and poor environmental friendliness, its application is currently limited.
-* * Applicable scenarios * *:
-Special strengthening treatments requiring high impact force (such as surface densification of thick walled castings) are gradually being replaced by lead-free high-density glass beads.
4. * * Recycling glass beads (economical)**
-* * Composition * *: Made from broken and sieved waste glass (such as wine bottles and glass products), the composition is complex (may contain multiple impurities).
-* * Features * *:
-The cost is extremely low, but the roundness is poor (mostly irregular particles), the hardness is unstable, and impurities (such as metal shavings and ceramics) may scratch the surface of the workpiece.
-* * Applicable scenarios * *:
-Rough cleaning with extremely low requirements for surface quality (such as rust removal of waste steel) is not recommended for precision or appearance parts treatment.
###2. Core criteria for selecting glass bead materials**
1. * * Workpiece material hardness**
-Soft workpieces (aluminum, copper, plastic, hardness ≤ HB100): Priority should be given to using sodium calcium glass beads (with moderate hardness to avoid workpiece deformation or excessive surface damage).
-Medium hard workpieces (cast iron, low carbon steel, HB100-200): sodium calcium glass beads or low borosilicate glass beads can be used (adjusted according to roughness requirements).
-Hard workpieces (high carbon steel, alloy steel, mold steel, HB ≥ 200): Choose borosilicate glass beads (high hardness, able to effectively clean or strengthen the surface, and slow self wear).
2. * * Processing Objectives**
-Cleaning (rust removal, oxide scale removal, coating removal):
-Ordinary cleaning: Sodium calcium glass beads (low cost, efficiency meets requirements).
-Stubborn impurities (such as thick rust, high-temperature oxide layer): borosilicate glass beads (high hardness, strong impact force, more thorough cleaning).
-Surface strengthening (improving fatigue strength):
-To induce plastic deformation (forming compressive stress) on the surface of the workpiece through glass bead impact, it is necessary to select borosilicate glass beads (with good toughness, not easily broken, and able to stably transmit impact force).
-* * Fine polishing/low roughness requirement (Ra ≤ 1.6 μ m) * *:
-Select * * high-purity borosilicate glass beads * * (high roundness, low impurities, avoid scratches, and can achieve a smooth surface under small particle size).
3. Surface quality requirements**
-If the workpiece needs to be subsequently painted or electroplated (with uniform surface roughening but no scratches): choose sodium calcium or borosilicate glass beads with high roundness (to avoid surface defects caused by irregular particles of recycled glass beads).
-Appearance parts (such as stainless steel decorative parts): High purity borosilicate glass beads must be used (with few impurities, uniform surface after treatment, and no spots).
4. * * Cost and Economy**
-Batch conventional processing: Sodium calcium glass beads (low cost, suitable for mid low frequency use).
-Long term cyclic use (such as automated production lines): borosilicate glass beads (high single purchase cost, but multiple repeated uses, lower overall cost).
###III. Summary of Selection Steps**
1. Clarify the workpiece material (hardness, vulnerability) and processing objectives (cleaning/strengthening/polishing).
2. Based on the hardness and surface quality requirements of the workpiece, preliminarily screen the material type (sodium calcium/borosilicate/special material).
3. Determine specific materials based on production scale (batch/single piece) and cost budget (such as selecting sodium calcium for batch conventional processing and borosilicate for precision parts).
4. Trial spray verification: Use a small amount of glass beads to test the treatment effect (roughness, surface integrity), and then apply it in bulk.
Through the above dimensions, it is possible to accurately match the glass bead material and processing requirements, ensuring both effectiveness and cost control.
