Steel; cementite, heat-treating, and all that sort of stuff

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In summary, cementite is a chemical compound that forms during the cooling process of some steels and helps to increase their hardness and brittleness. Heat-treating and quenching can also increase the hardness of steel, but at the cost of making it more brittle. Ceramics are not commonly used for blades due to their brittleness, but they do have some advantages over steel.
  • #1
cucumber
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hello.

need to know several things;

1. what exactly is the stuff that i keep reading about called "cementite", and what does it do to the metal
on an atomic scale to make it harder and more brittle?

2. how does heat-treating and quenching (ie. heating a steel blade, let's say, and then dunking it into oil,
or whatever it is they use) help to harden steel?

3. do they use ceramics for blades nowadays, and if they do, what advantages/disadvantages
do they have?

4. i forgot, might be added later on...


if you have an answer to any of the above, it would be splendiferous to hear it. thanks.
 
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  • #2
1. Cementite is a chemical compound consisting of iron and carbon, with a formula of Fe3C. It forms during the cooling process of some steels, when the ratio of carbon to iron is between 6.67% and 7.8%. It is hard and brittle and helps to increase the hardenability of steel. On an atomic scale, cementite provides an additional barrier to the movement of dislocations, making it harder and more brittle.

2. Heat-treating and quenching can help to harden steel by changing the microstructure of the material. When steel is heated, its crystal structure changes, resulting in a softer material. Quenching the steel quickly locks the atoms into place, which makes it harder. The increased hardness provided by heat-treating and quenching can also make steel more brittle.

3. Ceramics are not typically used for blades, due to their brittleness and lack of toughness. However, they do have some advantages over steel, such as higher temperature resistance, lower weight, and corrosion resistance. The main disadvantage of ceramics is their cost, which is usually much higher than that of steel.
 
  • #3


Hello there, thank you for your questions about steel, cementite, and heat-treating. I am happy to provide some information to help you better understand these topics.

1. Cementite is a compound that forms in steel when it contains a high amount of carbon. It is a hard, brittle, and highly ordered structure that forms within the steel matrix. On an atomic scale, cementite is made up of iron and carbon atoms arranged in a specific way that makes it stronger and more brittle than the surrounding steel. This is because the carbon atoms in cementite are tightly bound to the iron atoms, creating a rigid structure that makes it difficult for the steel to deform.

2. Heat-treating and quenching are processes used to harden steel. When steel is heated to a high temperature and then rapidly cooled, the atoms within the steel rearrange themselves into a more ordered structure. This creates a stronger and harder material. Quenching, which involves rapidly cooling the steel in a liquid such as oil or water, helps to lock in this new structure and prevent the steel from returning to its original, softer state.

3. While ceramics are sometimes used for blades, steel is still the most common material used for knife blades. Ceramics can have advantages such as being extremely hard and retaining sharpness for longer periods of time. However, they are also more brittle and can chip or break more easily than steel. Additionally, ceramics are more difficult to sharpen and are not as versatile as steel when it comes to different types of cutting tasks.

I hope this helps answer your questions. If you have any further inquiries, please feel free to ask. Have a great day!
 

1. What is steel made of?

Steel is primarily made of iron and carbon, with small amounts of other elements such as manganese, chromium, and nickel. The amount of carbon present in the steel determines its strength and hardness.

2. What is cementite and what role does it play in steel?

Cementite is a compound of iron and carbon that forms in steel during the heat-treating process. It is a hard and brittle substance that contributes to the strength and wear resistance of the steel.

3. What is the purpose of heat-treating steel?

Heat-treating is a process used to alter the physical and mechanical properties of steel. It involves heating the steel to a specific temperature and then cooling it at a controlled rate to achieve desired characteristics such as hardness, toughness, and ductility.

4. Can all types of steel be heat-treated?

No, not all types of steel can be heat-treated. The ability of steel to be heat-treated depends on its carbon content and other alloying elements. Steels with higher carbon content are generally more suitable for heat-treating.

5. What are the different types of heat-treating processes?

There are several types of heat-treating processes, including annealing, tempering, quenching, and hardening. Annealing involves heating the steel to a specific temperature and then cooling it slowly to make it softer and more ductile. Tempering involves reheating the steel after quenching to improve its toughness and reduce brittleness. Quenching involves rapidly cooling the steel to increase its hardness, while hardening involves heating the steel and then quenching it to make it harder and more wear-resistant.

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