In flat knife applications (such as die-cutting, trimming, and stamping), professionals have long been troubled by two issues: pure steel flat knives wear quickly, while pure tungsten carbide flat knives are costly and brittle. In reality, "steel-inserted tungsten carbide flat knives" are already a mature solution in the industry. By combining a "steel base for toughness and support" with "tungsten carbide inserted in the cutting edge or functional area for wear resistance," this type of flat knife not only solves the short service life of pure steel flat knives but also reduces the cost of pure tungsten carbide flat knives by 30%-50%. It also avoids the brittleness risk of pure tungsten carbide, making it suitable for most medium-to-high-load flat knife cutting scenarios. This article breaks down the practical value of such flat knives from the perspectives of feasibility principles, common structures, manufacturing processes, core advantages, and applicable scenarios, helping you understand "why steel insertion is used," "how to choose the right structure," and "which common issues to avoid."
1. First, Clarify: The Feasibility of Steel-Inserted Tungsten Carbide Flat Knives—Material Complementarity Is the Core Logic
Flat knives can indeed be made with steel-inserted tungsten carbide, and the fundamental reason lies in the precise performance complementarity between steel and tungsten carbide. This complementarity offsets their respective shortcomings in flat knife applications, creating a "composite structure" better suited to industrial needs.
Performance Comparison Between Steel and Tungsten Carbide (From a Flat Knife Application Perspective)
| Performance Dimension |
Steel (e.g., 45# Steel, Cr12MoV) |
Tungsten Carbide (e.g., WC-Co Type) |
Complementarity Logic of Steel-Inserted Tungsten Carbide |
| Toughness (Impact/Deformation Resistance) |
High (withstands instantaneous impact during stamping/cutting, not easily bent or broken) |
Low (high hardness but high brittleness, prone to edge chipping or breaking under impact) |
The steel base (70%-90% of the knife’s weight) bears impact forces and provides support during cutting, preventing overall knife damage |
| Wear Resistance (Edge Life) |
Low (pure steel flat knives need sharpening after only 10,000-30,000 cuts on corrugated paper) |
High (tungsten carbide edges last 100,000-200,000 cuts without frequent sharpening) |
Tungsten carbide is only inserted in the "cutting edge" or "functional area" of the flat knife, focusing on core wear resistance needs and reducing the use of expensive materials |
| Cost |
Low (steel price: ~5-12 yuan/kg; low processing cost) |
High (tungsten carbide price: ~200-300 yuan/kg; processing requires diamond tools) |
Tungsten carbide accounts for only 10%-30% of the knife’s weight, making the overall cost 30%-50% lower than pure tungsten carbide flat knives and 10%-20% higher than pure steel flat knives—yet service life increases 5-10 times |
| Machining Flexibility |
High (can be turned, milled, and heat-treated; complex shapes processed with ordinary machines) |
Low (only grindable; complex shapes are difficult and costly to produce) |
The steel base can be processed into irregular shapes (e.g., arcs, steps), while only the tungsten carbide edge requires precision grinding—balancing shape flexibility and accuracy |
Key Conclusion: Steel-inserted tungsten carbide flat knives are not a "compromise solution" but an "optimized solution" for flat knives that require "impact resistance, wear resistance, and cost control." The "poor wear resistance" of pure steel flat knives and the "high cost, brittleness, and poor machinability" of pure tungsten carbide flat knives are all fully addressed by this combination.
2. Common Structural Types of Steel-Inserted Tungsten Carbide Flat Knives: Classified by Insertion Position and Scenario
Based on flat knife cutting needs (e.g., straight-line cutting, irregular die-cutting, high-load stamping), the design of steel-inserted tungsten carbide varies. There are 3 mainstream types in industry, each suited to specific scenarios:
| Structural Type |
Insertion Method |
Core Features |
Applicable Scenarios |
Typical Application Examples |
| Straight-Edge Insertion |
Long strip-shaped tungsten carbide (1-3mm thick, length matching the edge) is inserted into the cutting edge (single or double-sided) of the flat knife; the steel base forms the main body of the knife |
Wear-resistant across the entire edge length; simple structure; cost-effective |
Straight-line cutting scenarios (e.g., cardboard edge trimming, film cutting, thin metal sheet cutting) |
Corrugated paper edge-trimming flat knives, film-slitting flat knives, thin metal sheet-cutting knives |
| Partial Functional Area Insertion |
Tungsten carbide is inserted only in the "high-frequency cutting area" of the flat knife (e.g., sharp corners of die-cutting knives, partial edges of stamping knives); other areas are steel |
Targeted wear resistance; saves tungsten carbide; avoids waste in non-functional areas |
Irregular die-cutting or partial stamping scenarios (e.g., irregular carton blank die-cutting, plastic part edge stamping) |
Irregular carton die-cutting flat knives, plastic part stamping flat knives, leather irregular-cutting knives |
| Multi-Layer Composite Insertion |
Steel base + intermediate transition layer (e.g., copper/nickel alloy for enhanced bonding) + tungsten carbide edge (3-5mm thick); overall heat treatment for strengthening |
High bonding strength; impact-resistant edge; suitable for high-load cutting |
Thick or high-hardness material cutting scenarios (e.g., thick steel plate cutting, wood cutting, composite material stamping) |
Thick steel plate-cutting flat knives, wood-cutting flat knives, fiberglass composite stamping knives |
Selection Logic:
- For "full-length straight-line cutting" (e.g., cardboard edge trimming): Choose straight-edge insertion to ensure uniform edge wear resistance.
- For "irregular die-cutting or partial cutting" (e.g., irregular carton die-cutting): Choose partial functional area insertion to avoid wasting tungsten carbide.
- For "cutting thick or high-hardness materials" (e.g., thick steel plates): Choose multi-layer composite insertion to enhance edge impact resistance and bonding strength.
3. Manufacturing Process of Steel-Inserted Tungsten Carbide Flat Knives: Key Steps and Quality Control
The core quality requirement for this type of flat knife is "firm bonding between tungsten carbide and the steel base"—poor bonding causes the tungsten carbide to detach or chip during cutting, rendering the knife useless. Below is a mature industrial manufacturing process, consisting of 5 key steps:
1. Steel Base Design and Processing (Fundamental Guarantee)
- Material Selection: Choose steel grade based on the scenario—45# steel for general cutting (low cost, easy processing); Cr12MoV for high-impact scenarios (hardness reaches HRC58-62 after heat treatment, with good toughness).
- Forming: Use lathes and milling machines to process steel into the flat knife base shape (e.g., rectangular, arc-shaped, irregular), and machine an "insertion groove" in the edge or functional area. The groove depth is 0.1-0.2mm deeper than the tungsten carbide thickness, and the width is 0.05-0.1mm wider than the tungsten carbide—reserving space for welding/press-fitting.
- Pretreatment: Perform "sandblasting + pickling" on the insertion groove surface to remove oxide layers and oil, enhancing bonding with tungsten carbide. Finally, conduct overall quenching and tempering heat treatment on the steel base (hardness reaches HRC28-32) to improve overall toughness.
2. Tungsten Carbide Edge Preparation (Core Functional Area)
- Material Selection: Choose tungsten carbide grade based on the cutting material—WC-Co (8%-10% Co content, balancing wear resistance and edge chipping resistance) for cutting paper/film; WC-TiC-Co (with TiC to improve hardness and wear resistance) for cutting metal/hard plastic.
- Forming: Press tungsten carbide powder into long strip or partial sheet edges matching the insertion groove, then sinter at 1400-1450℃ in a vacuum to form blanks.
- Rough Grinding: Use diamond grinding wheels to grind the edges to precise fit with the insertion groove (dimensional deviation ≤0.02mm), ensuring no gaps during subsequent bonding.
3. Insertion Bonding (Critical Step Determining Service Life)
There are 3 main bonding methods in industry, selected based on flat knife application:
| Bonding Method |
Process Characteristics |
Bonding Strength |
Applicable Scenarios |
| Silver-Copper Brazing |
Apply silver-copper solder (melting point 600-700℃) to the insertion groove, place the tungsten carbide edge, and heat in a furnace at 750-800℃ for 15-20 minutes to melt the solder and fill gaps |
Shear strength ≥180MPa; firm bonding |
Most scenarios (straight-edge and partial-insertion flat knives) |
| Cold Press-Fitting |
Press the tungsten carbide edge into the interference-fit insertion groove (edge 0.01-0.03mm larger than the groove) with a hydraulic press (200-300MPa) at room temperature; no heating required |
Shear strength ≥150MPa; no high-temperature deformation risk |
High-precision flat knives (e.g., electronic film-cutting knives) and thin-walled flat knives |
| Laser Welding |
Use a high-energy laser beam (1-3kW power) to weld the tungsten carbide edge to the steel base; small heat-affected zone (≤0.5mm) |
Shear strength ≥200MPa; strongest bonding |
High-load flat knives (e.g., thick steel plate-cutting knives, wood-cutting knives) |
4. Precision Machining and Edge Treatment (Ensuring Cutting Quality)
- Precision Grinding: Use diamond grinding wheels to precision-grind the tungsten carbide edge, ensuring the edge angle (e.g., 30°/45°) is accurate (deviation ≤0.5°) and the edge surface roughness reaches Ra ≤0.1μm (to avoid burrs during cutting).
- Overall Finishing: Perform precision milling or polishing on non-edge areas of the steel base to ensure the flat knife’s overall flatness (deviation ≤0.01mm), preventing uneven force during cutting.
- Rust Prevention: Chrome-plate the steel base surface (5-10μm thick) or apply anti-rust paint to prevent rust in humid environments.
5. Quality Inspection (Preventing Defective Products from Entering the Market)
- Bonding Strength Test: Use a tensile tester to check the tungsten carbide edge’s detachment force, which must be ≥120N (to ensure no detachment during cutting).
- Dimensional Accuracy Test: Use a 2D image measuring instrument to check the edge angle, flat knife flatness, and overall dimensions, ensuring compliance with design drawings.
- Test Cutting: Perform test cuts with actual materials (e.g., corrugated paper, thin metal sheets) to check cut quality (no burrs, no edge chipping). No obvious edge wear should occur after 1,000 consecutive cuts.
4. Core Advantages of Steel-Inserted Tungsten Carbide Flat Knives: Clear Value Compared to Pure-Material Flat Knives
To intuitively demonstrate its advantages, the table below compares steel-inserted flat knives with pure steel and pure tungsten carbide flat knives across cost, service life, and performance:
| Comparison Dimension |
Steel-Inserted Tungsten Carbide Flat Knife |
Pure Tungsten Carbide Flat Knife |
Pure Steel Flat Knife |
| Material Cost |
Medium (30%-50% lower than pure tungsten carbide; 10%-20% higher than pure steel) |
High (all tungsten carbide; 2-3x the cost of steel-inserted) |
Low (all steel; lowest cost) |
| Service Life (Standard Conditions) |
100,000-200,000 cuts (no frequent sharpening) |
150,000-250,000 cuts (longest life but prone to chipping) |
10,000-30,000 cuts (shortest life; frequent sharpening needed) |
| Impact Resistance |
High (steel base resists impact; edge chipping rate ≤0.5%) |
Low (brittle; edge chipping rate ≥5%; prone to breaking under impact) |
High (impact-resistant but edge wears quickly) |
| Machining Flexibility |
High (irregular shapes possible; controllable cost for complex designs) |
Low (complex shapes are costly and difficult to process) |
High (irregular shapes possible but edge wears poorly) |
| Comprehensive Cost-Effectiveness (Life/Cost Ratio) |
High (unit cutting cost is only 1/5-1/3 of pure steel flat knives) |
Medium (unit cutting cost is 1.5-2x that of steel-inserted) |
Low (high hidden costs from frequent sharpening/knife replacement) |
Key Conclusion: Steel-inserted tungsten carbide flat knives offer the "highest comprehensive cost-effectiveness"—while their upfront cost is higher than pure steel, their service life increases 5-10 times, resulting in lower unit cutting costs. They are also more impact-resistant and flexible to machine than pure tungsten carbide flat knives, making them the first choice for over 90% of medium-to-high-load flat knife scenarios.
5. Clarifying Common Myths: 3 Misconceptions About Steel-Inserted Tungsten Carbide Flat Knives
Myth 1: "Inserted tungsten carbide easily detaches, making it less durable than pure tungsten carbide."
Fact: With proper processing (e.g., correct bonding method selection, thorough pretreatment), the bonding strength of steel-inserted flat knives fully meets industrial needs. Reputable manufacturers report a tungsten carbide detachment rate of ≤0.3%, and service life is only 20%-30% shorter than pure tungsten carbide flat knives—yet cost is 30%-50% lower, delivering higher overall cost-effectiveness. Detachment typically occurs in low-quality products from manufacturers that skip "sandblasting pretreatment" or "post-welding insulation"; choosing qualified suppliers avoids this issue.
Myth 2: "Steel-inserted flat knives have lower cutting precision than pure tungsten carbide flat knives."
Fact: Flat knife cutting precision depends on "edge grinding accuracy" and "overall flatness," not whether tungsten carbide is inserted. Reputable steel-inserted flat knives have an edge angle deviation of ≤0.5° and overall flatness of ≤0.01mm—comparable to pure tungsten carbide flat knives (angle deviation ≤0.3°, flatness ≤0.008mm). They fully meet high-precision cutting needs (e.g., electronic film cutting with a cut deviation of ≤0.1mm).
Myth 3: "All flat knives should use steel insertion; pure steel flat knives are unnecessary."
Fact: Pure steel flat knives still have value in low-load, low-frequency cutting scenarios. For example, in scenarios like "occasional small-batch waste paper cutting" or "low-precision cardboard trimming," the low cost of pure steel flat knives (10%-20% lower than steel-inserted) and no need for complex processing make them more advantageous. The service life advantage of steel-inserted flat knives cannot be realized here, leading to unnecessary cost waste.
6. Conclusion: Steel-Inserted Tungsten Carbide Flat Knives—The "Cost-Effectiveness King" for Flat Knife Applications
The question is not "can flat knives be made with steel-inserted tungsten carbide" but "how to select the right structure and process based on the scenario." By leveraging material complementarity, this design perfectly solves the pain points of pure steel (poor wear resistance) and pure tungsten carbide (high cost, brittleness) flat knives, becoming the mainstream solution for medium-to-high-load flat knife cutting.
For professionals in the tungsten carbide industry, recommendations should focus on the customer’s "cutting material (soft/hard), load (low/high), and precision requirements":
- For general soft material cutting: Choose "straight-edge insertion + silver-copper brazing."
- For high-precision cutting: Choose "cold press-fitting."
- For high-load hard material cutting: Choose "laser welding + multi-layer composite insertion."
This approach helps customers balance performance and cost.
If your enterprise faces issues like frequent flat knife wear, frequent knife replacement, or high costs, or needs custom irregular steel-inserted tungsten carbide flat knives, feel free to reach out. We can provide customized structure designs and process solutions based on your cutting scenario (material, frequency, precision).
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