Tempering and what it means to 'draw it'

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In summary, quenching and tempering processes are used to reduce hardness and brittleness in steel. However, the specific tempering process used can also affect other properties, such as toughness. The statement from the book about tempered hammer heads being both hard and brittle may be due to a low tempering temperature or a longer tempering process. 'Drawing a blades temper' refers to overheating the metal, which can result in a softer blade.
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Elquery
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HI. So I feel I have a pretty basic but good understanding of quenching and tempering processes (talking about steels). Tempering as I understand it removes internal stresses, reducing the hardness and brittleness created during quenching, but increasing other properties like toughness. (it can get sticky here dealing with the different adjectives such as hardness, toughness, strength, etc.) But mainly I'm focusing on the reduction of hardness and brittleness.

So what happened is I read a book talking about tools - possibly not a completely reliable source but I don't know - and it said this "hammer heads are tempered during manufacture to withstand impact, though that hardness can also make them brittle."

This statement seems to go against my understanding of temper. My only thought is that perhaps the author means to imply that the specific tempering process for hammer heads is such that they are left hard and brittle (i.e. a low tempering temp after a quench).
It also in a latter section says: "never put a tool head in a fire to burn out [broken] handle wood. The wood may disappear, but so will the temper of the metal, making the tool brittle and dangerous to use." I can only imagine that instead of 'brittle' the author means that the steel loses some other impact quality that may allow it to chip. Or that it has reached some temperature where brittleness in reintroduced (I have read that there are a few 'zones' in tempering that actually reintroduce brittleness rather than reduce it.

And lastly, a question I've long had hanging in the head: When people speak of 'drawing a blades temper' due to over-heating (such as on a grinding wheel) does this simply mean that the metal has been heated above the initial tempering temperature thereby making it softer than intended?

Any words of knowledge and experience much appreciated.
Thanks
-T
 
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Yes, the statement from the book does go against your understanding of tempering. It is possible that the author is implying that the tempering process for hammer heads is such that they are left hard and brittle. This could be due to a low tempering temperature after a quench, or it could also be due to an overly long tempering process at a higher temperature. Regarding your last question, 'drawing a blades temper' does indeed mean that the metal has been heated above the initial tempering temperature, thereby making it softer than intended. This can happen when a blade is overheated on a grinding wheel, or in any other situation where the metal is exposed to too much heat.
 

1. What is tempering and why is it important?

Tempering is a heat treatment process used to improve the strength and toughness of a material. It involves heating the material to a specific temperature and then cooling it in a controlled manner. This process helps to reduce the hardness of the material, making it less brittle and more ductile, which is important for preventing cracking or failure under stress.

2. How does tempering affect the microstructure of a material?

Tempering causes changes in the microstructure of a material by redistributing the carbon atoms within the material. This helps to reduce the concentration of carbon in certain areas, making the material less brittle and more ductile. It also allows for the formation of small, dispersed particles within the material, which can improve its strength and toughness.

3. What is the significance of the temperature at which tempering is performed?

The temperature at which tempering is performed is crucial as it determines the final properties of the material. Different temperatures can result in different microstructures and properties, so it is important to carefully control the temperature to achieve the desired outcome. Typically, the higher the tempering temperature, the softer and more ductile the material will be.

4. Can tempering be used on all types of materials?

No, tempering is typically used on ferrous metals, such as steel and iron, as well as some non-ferrous metals like copper and aluminum. It is not suitable for non-metallic materials like ceramics and polymers. Additionally, the specific tempering process and temperature will vary depending on the composition and properties of the material being tempered.

5. What does it mean to 'draw' a material during the tempering process?

The term 'drawing' refers to the final stage of the tempering process, where the material is held at a specific temperature for a certain amount of time. This allows for the transformation of the microstructure to occur, resulting in the desired properties. Drawing is often done in air or oil, and the time and temperature can be adjusted to achieve different levels of hardness and strength in the material.

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