Heat Treatment and Rust Resistance -Does it have an effect?

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Legendary_Jarl

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I was having an argument with a friend of mine today. He is a reenactor and wants to have a knife and a sword made from iron or mild steel for it to be "historically accurate". The other reason he mentioned was because "according to armorers" iron has better rust resistance than carbon steel.

My instinct told me that it would make perfect sense for the carbon steel to be MORE resistant to oxydation than iron because steel, even carbon steel, is a mixture that includes elements other than iron. My instinct, it seems was completely wrong. As it happens, apparently the molecular structure in which iron arranges makes it more resistance to oxydation than steel. The mixture of the steel generates certain gaps in the structure that allow for oxydation to occur at a faster rate and in more sections. This is the source that I found:

https://www.tf.uni-kiel.de/matwis/amat/iss/kap_9/advanced/a9_3_1.html

Anyways, my question is for anyone who may know wouldn't proper heat treatment aid in the formation of that outter uniform structure that would minimize/prevent oxydation?

If you could share any good sources with me I would appreciate it. All I found was studies of carbon content vs oxydation but at high temperatures.
 
Short answer.... Yes, absolutely! Certain HT protocols can leave much more, or much less free chromium in the matrix for corrosion resistance. I don't have time right now, but if I have time tomorrow I can type in a link or two.

I am sure others will weigh in with good links and info too.
 
The guys who actually know what they are talking about with regards to numbers will have to fill it in, but basically anything done to a bar of iron such as alloying, heat treating, forging (or lack of) and even finish will have some effect on the overall oxidation resistance of the material, and the type of oxidation that will happen first, or easiest. Something like surface/case hardening or similar will have an effect, compared to a otherwise raw iron bar, just as a perfectly polished surface will oxidize differently than a rough one. As far as I understand grain structure does play a part when it comes to how deep corrosion can go when it comes to pitting and subsurface corrosion.
 
To my knowledge, heating alloys to different temperatures for different lengths of time and then tempering for certain lengths of time at certain temperatures causes a transformation of elements within the alloy.

Once again, to my knowledge, some of the factors that are at play here are:

The temperatures at which the steel is heated, how long it is kept at that temperature, how quickly it is cooled and with what it is cooled with, the temperature at which it is tempered at, the duration for which it is held at that temperature, and how many times that process of tempering is repeated.


Depending on what purpose the maker has intended for the blade they heat treat the alloy to get specific attributes.

This is my understanding of it anyway.
 
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In my experience both of those steels rust about the same. That is to say they both rust pretty quick from what I've seen regardless of what heat treat steps are used.
 
Legendary_Jarl said:
I was having an argument with a friend of mine today. He is a reenactor and wants to have a knife and a sword made from iron or mild steel for it to be "historically accurate". The other reason he mentioned was because "according to armorers" iron has better rust resistance than carbon steel.

My instinct told me that it would make perfect sense for the carbon steel to be MORE resistant to oxydation than iron because steel, even carbon steel, is a mixture that includes elements other than iron. My instinct, it seems was completely wrong. As it happens, apparently the molecular structure in which iron arranges makes it more resistance to oxydation than steel. The mixture of the steel generates certain gaps in the structure that allow for oxydation to occur at a faster rate and in more sections. This is the source that I found:

https://www.tf.uni-kiel.de/matwis/amat/iss/kap_9/advanced/a9_3_1.html

Anyways, my question is for anyone who may know wouldn't proper heat treatment aid in the formation of that outter uniform structure that would minimize/prevent oxydation?

If you could share any good sources with me I would appreciate it. All I found was studies of carbon content vs oxydation but at high temperatures.
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That article you cite says that it is cementite that leads to corrosion issues in steel. Wrought iron, particularly ancient iron, is not necessarily free of cementite, however, as they were not producing pure iron. I was not aware of cementite being an issue with corrosion, but I am not a corrosion expert so perhaps I have simply not heard of this issue. However, with heat treatment it is possible to limit the amount of cementite in the microstructure, such as by dissolving cementite during austenitizing and quenching to form martensite.
 
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