회사 소식 How Are Tungsten Carbide Tools Made?

If you work with tungsten carbide tools—whether drill bits, cutting inserts, or wear-resistant parts—you know they’re tough, long-lasting, and essential for heavy-duty jobs. But have you ever wondered how these tools are made? The process is a mix of precision engineering and powder metallurgy, designed to turn fine powders into hard, durable tools. Tungsten carbide tool manufacturing follows 5 core steps: raw material preparation, powder mixing, compaction, sintering, and post-processing—each step carefully controlled to ensure the tool’s hardness, strength, and performance. In this article, we’ll break down each stage in simple terms, explain key details like materials and equipment, and even highlight differences in making common tool types. All content is based on real industrial practices, so it’s practical and easy to apply to your work.

Before diving into the process, let’s cover the two main ingredients—without these, there’s no tungsten carbide tool:

The first stage is preparing the powders to ensure they’re clean, dry, and the right size—this affects how well the tool holds together later.

• Sieving the powders: WC and binder powders are passed through fine sieves (100–200 mesh) to remove clumps or impurities (like dust or large particles). Clumps would create weak spots in the final tool.
• Drying: Powders are dried in an oven (80–120℃) for 2–4 hours. Moisture can cause bubbles or cracks during later steps (e.g., sintering), so dryness is critical.
• Weighing: Powders are measured precisely by weight (e.g., 90% WC powder + 10% cobalt powder) using digital scales. Even a 1% error in binder content can make the tool too brittle or too soft.

Pro tip: High-quality tools start with high-purity powders (99.5%+ purity). Low-purity WC powder with impurities like carbon or iron will reduce tool life.

Next, the WC powder, binder powder, and any additives are mixed together. The goal is to create a homogeneous “feedstock" (mixed powder) where binder is evenly distributed around WC particles—this ensures the tool has consistent hardness and strength.

• Equipment used: Industrial ball mills (either wet or dry) are the most common.
  • Wet mixing: Powders are mixed with a liquid (like alcohol or water) to prevent dust and ensure better blending. After mixing, the liquid is removed via drying.
  • Dry mixing: Used for simpler tools—powders are mixed with a small amount of lubricant (e.g., wax) to reduce friction during later compaction.
• Mixing time: Typically 4–24 hours, depending on powder size. Finer powders need longer mixing to avoid clumps.
• Check for uniformity: A small sample of the mixed powder is examined under a microscope to confirm no WC particles are clumped together—uniformity is non-negotiable here.

Now, the mixed powder is pressed into the rough shape of the final tool (called a “green blank" or “green compact"). This step turns loose powder into a solid, handleable shape—though it’s still fragile (like a dried sandcastle) and needs sintering to harden.

• Equipment used: Hydraulic presses (manual or automated) with custom steel molds. Molds are designed to match the tool’s final shape (e.g., a drill bit mold, a cutting insert mold).
• Pressure applied: 150–600 MPa (megapascals)—that’s 1,500–6,000 times atmospheric pressure! Higher pressure = denser green blank = stronger final tool.
• Key details:
  • Lubricant (added during mixing) helps the powder flow into the mold and release easily after pressing.
  • Green blanks have ~80% of the final tool’s density—they’re strong enough to handle but will shrink during sintering.

Example: To make a tungsten carbide drill bit, mixed powder is pressed into a mold shaped like a drill bit blank. The blank is then removed and set aside for sintering.

Sintering is the most critical step—it transforms the fragile green blank into a hard, dense tungsten carbide tool. This is where the powder becomes a solid material.

• Process overview: Green blanks are placed in a sintering furnace and heated to high temperatures in a controlled atmosphere (usually argon or nitrogen gas to prevent oxidation).
• Temperature and time:
  • Heating phase: The furnace is heated slowly (5–10℃ per minute) to 1,300–1,600℃ (depending on binder type—cobalt-bonded tools use ~1,450℃).
  • Holding phase: The temperature is held for 1–4 hours. During this time, the binder metal melts and flows around the WC particles, “gluing" them together. The blank shrinks (5–20% in size) as gaps between powder particles close.
  • Cooling phase: The furnace cools slowly (2–5℃ per minute) to room temperature. Rapid cooling would cause cracks, so slow cooling is key for strength.
• Result: A dense, hard tool with ~98–99% of its maximum density. The green blank’s fragility is gone—now it’s a true tungsten carbide tool, though it still needs finishing.

Sintered tools are close to their final shape, but they need post-processing to meet exact size, surface finish, and performance requirements.

1. Grinding: Uses diamond grinding wheels (since tungsten carbide is harder than steel) to refine the tool’s size and shape. For example, a sintered drill bit is ground to sharpen the cutting edge and ensure the shank fits a drill chuck.
2. Polishing: For tools that need a smooth surface (e.g., seal rings or precision cutting inserts), polishing removes grinding marks and creates a reflective finish.
3. Edge treatment: Cutting tools (like milling inserts) have their edges “honed" (slightly rounded) to prevent chipping during use.
4. Quality inspection: Every tool is checked to ensure it meets standards:
   • Hardness testing (using a Rockwell hardness tester—typical HRA 88–92).
   • Dimensional checks (using calipers or CNC measuring machines to confirm size).
   • Visual inspection (looking for cracks, pores, or surface defects).

Not all tungsten carbide tools are made exactly the same—small adjustments are made based on the tool’s purpose. Here’s a quick breakdown:

1. Myth: “Tungsten carbide tools are cast like steel."
   Fact: No—casting can’t create the uniform WC-binder structure needed for hardness. Tungsten carbide tools rely on powder metallurgy (mixing, compaction, sintering), not casting.

2. Myth: “Sintering is just 'heating until it’s hard’—no precision needed."
   Fact: Sintering requires strict control of temperature, atmosphere, and cooling rate. Even a 50℃ temperature error can make the tool too brittle or too soft to use.

The making of tungsten carbide tools is a precise process—every step, from powder mixing to sintering, affects the tool’s performance. High-quality tools come from consistent powder quality, accurate mixing ratios, and controlled sintering conditions.

If you’re sourcing tungsten carbide tools or curious about optimizing a specific tool’s manufacturing for your application (e.g., a drill bit for concrete vs. metal), feel free to reach out. We can help explain how process tweaks impact tool life and performance.