Granulator knives are core crushing and granulating tools in industries such as plastic recycling, rubber processing, and biomass energy. Their cutting performance and service life directly determine production efficiency and costs. Due to its ultra-high hardness (HRA≥90), wear resistance, and impact resistance, cemented carbide has become the preferred material for mid-to-high-end granulator knives. However, different materials (plastic, rubber, biomass) have significant differences in physical properties (hardness, toughness, abrasiveness, adhesion). Blind selection can lead to premature knife wear, uneven material crushing, increased energy consumption, and other issues. Focusing on tungsten carbide cemented carbide, this article uses clear tables and plain expressions to break down the selection parameters, structural design, and applicable scenarios of granulator knives by material type, helping industry practitioners accurately match requirements and improve granulation stability and economy.
1. First, Understand: Core Advantages and Basic Knowledge of Cemented Carbide Granulator Knives
Before selection, let’s briefly understand the core value of cemented carbide granulator knives to grasp "why differentiated selection is needed for different materials":
1.1 Core Advantages (Compared to Ordinary Steel)
- Wear Resistance: Tungsten carbide is 5-10 times more wear-resistant than high-speed steel and 3-5 times more than alloy tool steel, making it especially suitable for high-abrasion materials;
- Hardness: HRA≥90, capable of cutting materials with hardness ≤HRC60, without edge chipping caused by hard spots in materials (e.g., impurities in plastic, sand grains in biomass);
- Service Life: Under normal working conditions, the service life of cemented carbide granulator knives is 8-12 times that of ordinary steel, reducing downtime for knife replacement;
- Adaptability: By adjusting the tungsten carbide grade (cobalt content, grain size) and cutting edge structure, it can adapt to materials with different characteristics.
1.2 Basic Selection Dimensions (Detailed Later)
The core of granulator knife selection revolves around 3 dimensions:
- Tungsten carbide grade (determines the balance between hardness and toughness);
- Cutting edge structure (affects cutting efficiency and anti-adhesion effect);
- Knife body structure (adapts to granulator equipment and material feeding method).
2. Precise Selection by Material Type (Core Guide)
The characteristics of different materials directly determine the selection direction of granulator knives. Below are detailed selection schemes for three major material categories (plastic, rubber, biomass) with specific parameter references:
(1) Plastic Materials: Targeted Selection for "Hard/Soft/Recycled Materials"
Plastic granulation is the most mainstream application scenario. According to hardness and impurity content, it can be divided into hard plastic, soft plastic, and recycled mixed plastic, with different selection priorities:
| Plastic Type | Material Characteristics | Core Granulation Requirements | Cemented Carbide Selection Parameters | Recommended Cutting Edge Structure | Applicable Scenarios |
|---|---|---|---|---|---|
| Hard Plastic (PP/PE/ABS Hard Materials, Nylon) | High hardness (Shore D70-90), medium toughness, low abrasiveness, no adhesion | Sharp edge, low cutting resistance, no chipping | Grade: YG8/YG10 (cobalt content 8-10%, balancing hardness and toughness); Grain size: Medium grain (2-5μm) | Straight edge + micro-teeth (tooth pitch 2-3mm), edge angle 30-35° | New material granulation, high-hardness plastic molding pellets |
| Soft Plastic (PE/PP Film, Soft PVC, TPE) | Low hardness (Shore A50-70), high toughness, easy adhesion, no abrasiveness | Anti-adhesion, smooth cutting, no material winding | Grade: YG6/YG8 (cobalt content 6-8%, higher hardness); Surface treatment: Nitriding (improves smoothness) | Arc edge + polishing, edge angle 25-30° | Soft plastic film granulation, elastomer pellet processing |
| Recycled Mixed Plastic (Waste Appliance Shells, Plastic Bottle Fragments) | Uneven hardness, containing impurities (sand grains, metal debris), high abrasiveness, fluctuating toughness | High wear resistance, impact resistance, edge collision resistance | Grade: YG10/YG12 (cobalt content 10-12%, higher toughness); Grain size: Coarse grain (5-8μm) | Thick edge + chamfer design, edge angle 35-40°, edge thickness ≥2mm | Plastic recycling granulation, mixed waste crushing granulation |
Supplementary Notes:
- Common specifications of plastic granulator knives: Edge length 50-200mm, knife body thickness 8-15mm, customizable according to granulator cutterhead size;
- Solution for adhesion: For soft plastic granulation, in addition to selecting arc edges and nitriding treatment, heat dissipation grooves can be added to the knife body to reduce material adhesion caused by frictional heating.
(2) Rubber Materials: Focus on Solving "High Elasticity, Easy Adhesion, High Abrasiveness"
Rubber (natural rubber, synthetic rubber, waste tire rubber) has core characteristics of high elasticity, easy adhesion, and high abrasiveness (containing carbon black/fiber impurities). Granulator knives need to balance "cutting sharpness" and "impact/wear resistance":
| Rubber Type | Material Characteristics | Core Granulation Requirements | Cemented Carbide Selection Parameters | Recommended Cutting Edge Structure | Applicable Scenarios |
|---|---|---|---|---|---|
| Natural Rubber/Synthetic Rubber (New Material) | High elasticity, easy stretching, strong adhesion, low abrasiveness | Sharp edge, anti-adhesion, no cutting tearing | Grade: YG6X (fine grain, hardness HRA≥91, high sharpness); Surface treatment: PTFE coating (anti-adhesion) | Thin edge + serrated edge (tooth pitch 1.5-2mm), edge angle 25° | New rubber granulation, rubber product scrap recycling |
| Waste Tire Rubber (Rubber Powder Raw Material) | High hardness (Shore D60-80), containing steel wire/fiber impurities, extremely high abrasiveness, low elasticity | Ultra-high wear resistance, impact resistance, collision resistance | Grade: YG12X (coarse grain + high cobalt, balancing toughness and wear resistance); Knife body structure: Embedded cemented carbide tip | Thick edge + reinforced tip, edge angle 40°, tip thickness ≥3mm | Waste tire crushing granulation, rubber powder processing |
| Silicone/Soft Rubber (Medical Silicone, Silicone Rubber) | Ultra-soft elasticity, extremely easy adhesion, no abrasiveness, temperature-sensitive (fear of high temperature) | Low-temperature cutting, anti-adhesion, smooth edge | Grade: YG6 (high hardness); Surface treatment: Mirror polishing | Arc edge + wide edge design, edge angle 20-25°, knife body with heat dissipation holes | Silicone product recycling, soft rubber pellet processing |
Key Notes:
- Temperature control for rubber granulation: Rubber is prone to heat generation due to friction. Granulator knives should select cemented carbide with good thermal conductivity (e.g., YG6 series), and the knife body should be designed with heat dissipation structures to avoid material adhesion or deterioration due to high temperature;
- Impact resistance design: Waste tire rubber contains steel wire impurities. Granulator knives should adopt "embedded tips" instead of integral cemented carbide to avoid knife body fracture caused by impurity impact.
(3) Biomass Materials: Focus on "High Fiber, High Abrasiveness, Humidity Sensitivity"
Biomass (wood, straw, wood chips, biomass fuel) has core characteristics of high fiber content, high abrasiveness (containing lignin and sand grains), and large humidity fluctuations (10-30%). Granulator knives need to emphasize "high wear resistance" and "smooth cutting":
| Biomass Type | Material Characteristics | Core Granulation Requirements | Cemented Carbide Selection Parameters | Recommended Cutting Edge Structure | Applicable Scenarios |
|---|---|---|---|---|---|
| Wood/Wood Chips (Dry Material, Humidity ≤15%) | High fiber content, medium abrasiveness, high toughness, easy cutting | Wear resistance, sharp edge, no fiber winding | Grade: YG8/YG10 (balancing hardness and toughness); Grain size: Medium grain | Serrated edge (tooth pitch 3-4mm) + beveled edge design, edge angle 30-35° | Wood chip granulation, wood pellet fuel processing |
| Straw/Rice Husk (Silicon-containing, Humidity 15-30%) | High abrasiveness (silicon-containing), coarse fibers, humidity-sensitive, easy clogging | Ultra-high wear resistance, anti-clogging, good water drainage | Grade: YG10/YG12 (high cobalt, high wear resistance); Surface treatment: Hardening treatment | Wide-pitch serrated edge (tooth pitch 4-5mm) + chip removal grooves, edge angle 35-40° | Straw pellet fuel, rice husk recycling granulation |
| Hard Biomass (Branches, Hardwood Scrap) | High hardness, high fiber content, high abrasiveness, high toughness | Impact resistance, high wear resistance, strong cutting force | Grade: YG12/YG15 (high cobalt, high toughness); Knife body structure: Thickened knife body (thickness ≥12mm) | Thick serrated edge + reinforced back, edge angle 40-45° | Hardwood pellet processing, garden waste granulation |
Supplementary Notes:
- Wear characteristics of biomass granulator knives: Mainly edge blunting rather than chipping, so priority should be given to high-wear-resistant coarse-grain tungsten carbide grades;
- Humidity adaptation: For high-humidity biomass granulation, the knife body should be designed with chip removal grooves and drainage holes to avoid material clogging due to water absorption and adhesion.
3. 3-Step Universal Selection Method (Quick Matching, No Mistakes)
Regardless of the material, the following 3 steps can be used to quickly select cemented carbide granulator knives without complex calculations:
Step 1: Analyze Core Material Characteristics (Key Premise)
- Hardness: Hard materials (e.g., hard plastic, hardwood) → Select high-hardness tungsten carbide (YG6/YG6X);
- Toughness/Elasticity: High-elasticity materials (e.g., rubber, soft plastic) → Select grades balancing toughness (YG8/YG10);
- Abrasiveness: Impurity-containing/high-abrasion materials (e.g., recycled plastic, straw) → Select high-cobalt coarse-grain grades (YG10/YG12);
- Adhesion: Easy-adhesion materials (e.g., soft plastic, silicone) → Select polished/coated treatment + arc/serrated edges.
Step 2: Determine Cutting Edge and Knife Body Structure
- Sharpness Requirement: New materials, soft materials → Thin edge, small angle (25-30°);
- Impact Resistance Requirement: Impurity-containing, hard materials → Thick edge, large angle (35-45°);
- Anti-winding/Anti-clogging: Fiber materials, soft materials → Serrated edge, chip removal grooves.
Step 3: Verify Adaptability (Combined with Equipment and Working Conditions)
- Granulator Type: Flat-die granulator → Select straight/beveled edges; Ring-die granulator → Select arc/serrated edges;
- Production Efficiency: High-output requirements → Select multi-tooth edges (improve cutting efficiency);
- Maintenance Cost: Frequent knife replacement affects efficiency → Select high-wear-resistant grades (YG10/YG12) to extend service life.
4. Common Selection Mistakes (Avoid These to Improve Efficiency)
- Blindly Pursuing High Hardness: Focusing only on hardness and ignoring toughness, leading to edge chipping when processing high-elasticity/impurity-containing materials (e.g., using YG6 to process waste tire rubber);
- Neglecting Surface Treatment: Not applying anti-adhesion treatment (polishing/coating) to easy-adhesion materials (e.g., soft plastic, silicone), resulting in material winding around the edge and reduced efficiency;
- Single Cutting Edge Structure: Using straight edges instead of serrated edges for fiber materials (e.g., straw, wood), leading to fiber winding and high cutting resistance;
- Ignoring Knife Body Structure: Using integral cemented carbide knife bodies for impurity-containing materials instead of embedded tips, leading to knife body fracture due to impact.
5. Typical Application Cases (Intuitive Reference)
| Application Scenario | Material Type | Recommended Granulator Knife Configuration | Selection Logic | Expected Service Life |
|---|---|---|---|---|
| Waste Plastic Film Recycling Granulation | PE Film (Soft Plastic, Easy Adhesion) | Grade YG8, arc edge + nitriding treatment, edge angle 25° | Anti-adhesion + sharp cutting, adapting to soft materials | 800-1200 hours |
| Waste Tire Rubber Granulation | Tire Rubber (Steel Wire-containing, High Abrasiveness) | Grade YG12X, embedded serrated edge, edge angle 40° | High wear resistance and impact resistance, avoiding fracture from impurity impact | 500-800 hours |
| Wood Pellet Fuel Processing | Hardwood Chips (High Fiber, Abrasive) | Grade YG10, serrated edge + chip removal grooves, edge angle 35° | Wear resistance + anti-winding, improving cutting efficiency | 1000-1500 hours |
| Silicone Product Recycling Granulation | Medical Silicone (Easy Adhesion, Temperature-sensitive) | Grade YG6, mirror-polished arc edge + heat dissipation holes | Anti-adhesion + low-temperature cutting, avoiding silicone deterioration | 600-1000 hours |
Conclusion: The Core of Selection is "Material Characteristics → Parameter Matching"
There is no "one-size-fits-all" option for cemented carbide granulator knives. The core is to match the tungsten carbide grade, cutting edge structure, and knife body design according to the material’s "hardness, toughness, abrasiveness, and adhesion": select high-hardness grades + thin edges for hard materials, anti-adhesion treatment + arc edges for soft materials, high-toughness grades + thick edges for impurity-containing materials, and serrated edges + chip removal grooves for fiber materials.
As a tungsten carbide industry practitioner, we can provide customized granulator knife solutions—matching the optimal tungsten carbide grade, cutting edge structure, and surface treatment method according to your specific material type, granulator parameters, and output requirements, helping improve production efficiency and reduce knife replacement costs. If you need precise configuration recommendations for specific scenarios (e.g., special material granulation, high-output working conditions), please contact us for customized advice!