Tungsten Industry Story: The Teeth of Industry - Tungsten Carbide Hard Alloy

This article is selected from the third prize work "Cemented Carbides - One of the Most Successful Engineering Materials for Humanity" of the Science Popularization Essay Competition of the China Tungsten Industry Association. The author is Wang Xiaoling from the Profile Business Department of Zigong Cemented Carbides Co., Ltd.

Materials are a symbol of the level of human civilization development, and the development and updating of materials can promote the progress and leap of human civilization. This article will introduce tungsten carbide hard alloys that have made significant contributions to the manufacturing industry.

1. What is hard alloy

Hard alloy is an alloy material made from hard compounds of refractory metals and bonded metals through powder metallurgy process. The structure of hard alloy is similar to that of concrete. The binder that plays the role of "cement" in tungsten carbide hard alloys is mainly cobalt (Co), while tungsten carbide (WC) plays the role of "sand and stone".

Tungsten carbide cobalt hard alloy

concrete

2. The Origin of Hard Alloys

1923-2023

It has been exactly a hundred years since the invention of hard alloy.

In the early 1920s, Carl, an engineer at OSRAM, a German light bulb company ▪ Karl Schr ö ter invented WC Co hard alloy in search of an alternative material for expensive diamond molds used for drawing tungsten filaments. In 1923, he applied for the first hard alloy patent (German Patent No. 420689) and was authorized in 1925.

Hard alloy stretching mold

In 1926, the military giant Krupp, which obtained patent authorization, produced the first batch of commercial hard alloys, which were used as cutting heads for mechanical processing, greatly improving processing efficiency, causing a sensation in the world and quickly becoming strategic materials at high prices. At that time, the price of one gram of hard alloy was higher than one gram of gold.

3. Types of hard alloys

01 Tungsten cobalt hard alloy

This type of hard alloy only contains tungsten carbide and cobalt, or pure WC-Co hard alloy with very small amounts (generally not exceeding 1%) of other added components. The international standard (ISO) refers to it as K-type hard alloy, while the national standard in China refers to it as tungsten cobalt (YG) type hard alloy; For example, YG6 (WC-6Co), a hard alloy with a cobalt content of 6% (mass fraction) and tungsten carbide, is the first commercial hard alloy in the world.

02 Tungsten cobalt titanium hard alloy

In addition to tungsten carbide and cobalt, tungsten cobalt titanium (WC TiC Co) cemented carbide with a certain amount (over 1%) of titanium carbide (TiC) is also added. The international standard is called Class P, and the national standard is called Class YT. The amount of titanium carbide is usually less than the amount of tungsten carbide; If the amount of titanium carbide exceeds the amount of tungsten carbide, it becomes a "titanium carbide based hard alloy" or a more specialized term for "titanium carbide based cermet".

03 Tungsten cobalt titanium tantalum (niobium) hard alloy

The third type is WC TiC TaC (NbC) - Co cemented carbide with a certain amount of tantalum carbide (TaC) and/or niobium carbide (NbC) added to the second type. The international standard is called M, and the national standard is called YW.

There are also WC Ni hard alloys that replace cobalt with nickel (Ni), or steel bonded hard alloys that replace cobalt with ferroalloys (steel). Engineers can replace WC and Co in WC Co partially or completely with titanium carbide, tantalum carbide, niobium carbide, molybdenum carbide, chromium carbide and other metal carbides, or nickel, iron, chromium and other metals, and design different compositions to obtain cemented carbides with different properties to meet the requirements of different applications.

4. Performance of hard alloys

(1) High hardness and good wear resistance

The hardness of hard alloy ranges from 80 to 94 HRA, while even tool steel after quenching and hardening has a high hardness of only 80 HRA or slightly higher. For a long period of time, hard alloy was the material with the hardness second only to diamond. In fact, the trade name of the first generation of hard alloy was "Widia" (derived from the German word Wie Diamant, meaning "diamond like"), which was invented to replace diamond. So, it can be said that hard alloys are made for hardness.

(2) High strength and elastic modulus

The bending strength of typical hard alloys can reach 3000-5000 MPa (N/mm2) and are not easily deformed.

(3) Heat and corrosion resistance

It generally has good resistance to atmospheric, acid, alkali and other corrosion, and is not easily oxidized. These characteristics make it an excellent material for wear-resistant structural components used in high-temperature and corrosive environments.

5. Use of hard alloys

Hard alloy is widely used, from national defense and military industry, industrial manufacturing, geological drilling, mining and oil extraction, rock drilling and construction, agricultural production to our daily lives, hard alloy products can be seen everywhere.

Tool material

As a machining tool, it is an important use of hard alloy, consuming over half of the hard alloy production. Hard alloy has been a good material for machining cutting tools since its inception, earning the reputation of "industrial teeth".

Mold material

Hard alloy is mainly used as cold working molds such as cold drawing molds, cold punching molds, cold extrusion molds, and cold pier molds.

Cold heading molds

drawing die

Measuring tools and wear-resistant parts

Hard alloy is used for easy to wear surface inlay and parts of measuring tools, precision bearings of grinding machines, guide plates and rods of centerless grinding machines, and wear-resistant parts such as lathe centers.

Special hard alloy

With the advancement of technology, the production of hard alloy materials has also developed rapidly, and the downstream industry has more technical requirements for products. As a result, the demand for hard alloy materials in the market continues to increase. The production technology of hard alloy materials has also been improved, and corresponding special hard alloy materials are currently widely used in military industry, aerospace, mechanical processing, metallurgy, oil drilling, mining tools, electronic communication, construction and other fields. Cemented carbide products with high technology content and high quality stability are also used in high-tech weapon equipment manufacturing, scientific and technological progress, Nuclear Energy and other fields.

Note: This article is reprinted from: Chinese Tungsten Industry Academic Journal (if there is any infringement, please contact us promptly to delete it)