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Why Carbide Tools

Why Carbide Tools

Most of the time, carbide cutters will leave a better surface finish on the part, and allow faster machining than high-speed steel or other tool steels. Carbide tools can withstand higher temperatures at the cutter-workpiece interface than standard high-speed steel tools (which is a principal reason for the faster machining). Carbide is usually superior for the cutting of tough materials such as carbon steel or stainless steel, as well as in situations where other cutting tools would wear away faster, such as high-quantity production runs.

Applications of Carbide

Inserts for metal cutting

Carbide is more expensive per unit than other typical tool materials, and it is more brittle, making it susceptible to chipping and breaking. To offset these problems, the carbide cutting tip itself is often in the form of a small insert for a larger tipped tool whose shank is made of another material, usually carbon tool steel. This gives the benefit of using carbide at the cutting interface without the high cost and brittleness of making the entire tool out of carbide.

Most modern face mills use carbide inserts, as well as many lathe tools and endmills. In recent decades, though, solid-carbide endmills have also become more commonly used, wherever the application's characteristics make the pros (such as shorter cycle times) outweigh the cons (mentioned above).

Insert coatings

To increase the life of carbide tools, they are sometimes coated. Five such coatings are TiN (titanium nitride), TiC (titanium carbide), Ti(C)N (titanium carbide-nitride), TiAlN (titanium aluminium nitride) and AlTiN (aluminium titanium nitride). (Newer coatings, known as DLC (diamond-like carbon) are beginning to surface, enabling the cutting power of diamond without the unwanted chemical reaction between real diamond and iron.) Most coatings generally increase a tool's hardness and/or lubricity.

Inserts for mining tools

Mining and tunneling cutting tools are most often fitted with cemented carbide tips, the so-called "button bits". Artificial diamond can replace the cemented carbide buttons only when conditions are ideal, but as rock drilling is a tough job cemented carbide button bits remain the most used type throughout the world.

Rolls for hot-roll and cold-roll applications

Since the mid-1960s, steel mills around the world have applied cemented carbide to the rolls of their rolling mills for both hot and cold rolling of tubes, bars, and flats.

HSS vs. Carbide Steel

High Speed Steel is a high carbon tool steel, containing lots of tungsten and cobalt and is rich in molybdenum, tungsten and vanadium. A Carbide steel is a compound of carbon with another alloy metallic element. Commonly, referred to tungsten carbide, which is a common example of a metal carbide.  Carbide tools enable harder materials to be machined, potentially up to 70+HRC.

The main difference between them is mainly listed below:

  • The red hardness of high-speed steel is 650℃, but the Carbide steel can reach 800-1000℃.
  • Carbide steel has more high cutting speed and is 4- 7 times higher than high – speed steel.
  • Carbide is much harder, so it has a longer tool life and faster cutting data than conventional high speed steel.
  • HSS tools also cost less than Carbide tools and are often a good solution in high-mix, low-volume applications.
  • HSS doesn’t have the wear resistance and lifespan of carbide, so it tends to be more resilient and less brittle and is the best choice for deep cuts with small tip sizes in harder materials.

About Price

Much of the price difference is an issue of materials. Tungsten carbide is primarily tungsten with a few percent cobalt. Any steel has a really high percentage of iron. Iron is much, much cheaper than tungsten or cobalt.

Steel, even high speed and tool steel, is made in huge quantities. By comparison tungsten carbide is made in relatively small quantities. As an example, a ton of steel is very little steel whereas a ton of tungsten carbide is a huge amount of tungsten carbide.

You can machine tungsten carbide once it’s been sintered and fully hardened but it takes a long time and requires the use of diamond tooling.

When tungsten carbide is formed, and before it is fully sintered and hardened, it is softer than sidewalk chalk and you can whittle it into shape.  However tungsten carbide shrinks during the final sintering so you have to whittle the pre-sintered part into something oversize. You want to leave yourself a little fudge room which means it will require some machining after it is sintered and fully hardened.

So tungsten carbide is much more expensive than steel because the materials are much more expensive, because it is not made in anywhere near the volume steel is and because it is much harder to make.

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