The precision journey of the tungsten carbide inserts

The precision journey of the tungsten carbide inserts

Metal processing is inseparable from the inserts. A high-quality insert must have these characteristics:

  • High wear resistance
  • Long tool service life
  • High metal removal rate
  • High reliability

Even under severe conditions (such as complex cutting and deep cavity), dry cutting or wet cutting maintains high performance, can control small tolerances of workpiece dimensions and excellent surface quality.

We shall take you to see how the cemented carbide inserts is produced.

A typical blade is made of 80% tungsten carbide and a metal matrix. The role of the metal matrix is to bond-to bond cemented carbide powders together. The most common binder is cobalt. The production process of the blade is very complicated, it takes more than two days to complete, and there will be a lot of challenges in the middle. In addition to absolute precision and reliability, cleanliness is a prerequisite. Quality assurance must be done in the whole process, and no sloppy is allowed.

The precision journey of the carbide insert will go through the following five stages: proportioning→grinding→sintering→polishing→cleaning and coating

Proportioning

The proportion is the first stage, and the proportion of each powder must be just right. Tungsten is a limited raw material, which comes from tungsten mines or recycled cutting inserts. The raw materials for cobalt, titanium and other binders must be checked well also.

Nevertheless, each batch of raw materials must be meticulously tested in the laboratory for safety. Then the main components are automatically distributed to containers at different stations along the weighing line. For some indexable carbide inserts, a small amount of special ingredients need to be added manually.

Grinding

The powder is mixed with ethanol, water with organic compounds then ground to the suitable particle size: usually 0.1-5μm in diameter.

After successful mixing, it will turn into a gray slurry with a consistency similar to that of a yogurt drink. After the slurry is dried, the powder is formed and sent to the press for processing and injected into the cavity of the specific tool insert mold. The machine tool can apply 50 tons of pressure when manufacturing a single tungsten carbide insert.

The inserts that come out will still be weighed. At this stage, the carbide insert are still very fragile, so the next step is to enter the sintering furnace.

Sintering

The sintering furnace can sinter thousands of inserts at a time. The lathe inserts is heated to approximately 1,500°C to melt the pressed powder into a cemented carbide.

The size of the sintered carbide inserts will be compressed to about half of the previous process.

After another quality inspection, the cutting insert is ground to the required thickness.

Polishing

This is a key step in the whole processing. There has been a joke in the factory: “If you sneeze, the tolerance will change immediately.”

Using a 6-axis grinder can ensure very tight tolerances. Because cemented carbide is very hard, a PCD grinding wheel is used for grinding to the correct thickness. Under normal circumstances, the carbide turning insert has to be sharpened again to achieve its precise geometry and size.

Cleaning and coating

The coating of carbide cutting inserts is divided into two different coating methods: chemical vapor deposition (CVD) and physical vapor deposition (PVD).

By covering the coating, the carbide inserts become harder, tougher, and even more wear-resistant.

After all steps are completed, the cutting inserts tool can be packaged at any time, but even after multiple inspections throughout the process, manual inspections are still required with the naked eye. The quality inspector must wear gloves when handling the indexable inserts. In addition, compared with drawings and batch orders, and mark the correct material with laser is required.

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