Carbide vs Steel ¿What are the differences to consider...

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Jose Luis Discussion started by Jose Luis, on Wednesday, 27 September 2017 15:59
Carbide vs Steel

Ultra carbide hard tungsten carbide and similar hard metals became widely available in the 1930s, and quickly revolutionized most of the technologies that require cutting hard or abrasive materials. Until the invention of these alloys, tempered steel was the only practical material for sculptor's tools, and the establishment and maintenance of carving tools was an important part of the formation of a sculptor.

Tools had to be repaired or replaced frequently, and a sculptor needed to know how to forge and grind tools, and how to harden and temper them so that the material could be adapted to the hand.

Tungsten carbide is not exactly a metal in itself, but one of the two metal compounds such as tungsten and carbon (Tungsten Carbide, WC or Tungsten Semi Carbide, W2C) that are produced in gray powders.

Tungsten carbide powder is sintered into a cobalt metal matrix (sintering is an alloy process in which the finely powdered metals are fused together by extreme pressure, rather than being fused into a true solution.

Tungsten carbide prepared in this way is the hardest metal material commonly used. Only certain precious stones silicon carbide gel (carborundum) are harder, and unlike tungsten carbide, these materials can only be used in the form of abrasives, not as cutting edges.

Carbide tools are a little more expensive, but it's cheap in the long run because they last longer than steel, up to 100 times longer, and allow you to work hard materials into shapes that would otherwise be difficult or impossible. They also require much less frequent maintenance, and the maintenance they require is generally simpler.

For industrial use, tungsten tipped tools have almost entirely replaced steel for cutting hard or abrasive materials such as stone, as well as for much less abrasive materials such as wood. However, in stone carving, tungsten is not always an exact substitute for steel.

Carbide is more fragile than steel. This limitation gives many carbide tools and is a significantly different working sensation.

For granite and similar stones tungsten is almost always recommended, but for softer stones, for many tools, steel allows sharper cuts as it is thinner and gives deeper penetration and a better result, more easily, for many applications.

Steel tools are usually forged from a single piece of steel, with the end hardened by heat treatment. Tungsten, on the other hand, typically consists of a pointed steel tool body with a tungsten carbide insert, or inserts, welded together, i. e. soldered using brass.

For chisels and similar tools, carbide is usually set in a notch or perforated hole in the tool steel body.

Carbide is darker than steel, and the bond line between brass carbide and steel is usually visible, making carbide tools easy to recognize. When these tools fail, it is usually either in this brazing joint or by breaking the tip itself. The fault may or may not be repairable, depending on the manufacturer and the cost of the tool. Small carbide milling cutters for grinders are sometimes machined from a single piece of carbide.

When polishing the cutting edges on a steel wheel, it is important to keep them cool by turning them off frequently in water or oil, and to limit the time they are in contact with the wheel. This is because the hardening of steel begins to change at as little as 425 degrees Fahrenheit, which is easy for the heat of friction to burn the tip, leaving it softly useless. If, when grinding, you can see the metal near the change in color of the tip (do not shine, but turn yellow, blue or purple) you have to stop.

It is more, or less impossible to burn the part when sharpening a tool with your hand on a grinding stone, which may also be more convenient to touch while you work. Wheels that run wet also bypass this danger.

With carbide, the exact opposite is true: hardening while grinding can ruin the tool. This is because while heat does not moderate carbide hardness, its extreme hardness makes it prone to be affected by abrupt temperature changes. All materials expand or contract in response to temperature changes, so that when any tip of the hot tool is immersed in water, the cooling wave moving through it causes adjacent metal regions to fight each other as they change in size at different times. This does not affect tungsten, because it is slightly elastic, but carbide is so rigid that these stresses can cause internal fractures, weakening it, just as a glass of wine can break if it is immersed in hot water. Fortunately, most carbide can withstand very high temperatures.

Multi-purpose carbide drill bits drill through any combination of steel thickness, concrete, gypsum, and almost anything else, including granite, without the need for a liquid coolant. Hard as it may be, even carbide wears out over time and needs to be sharpened.

In fact, it is easier to regrind the carbide than it is to regrind the steel, because it can be done continuously without overheating. It is first ground with a fine silicon carbide wheel and then polished with a fine diamond grinding stone. Carbide is a bit like glass, as it tends to break more easily when scratched.

Do you agree? What do you think?

Don Dougan
Don Dougan Though I agree with what is said here, for most of my carving (in marble and limestone) I prefer to work with high carbon tool steel chisels. I... Show more Sunday, 20 September 2020 17:45
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