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Jake Wilson

Joined: 08 Sep 2009

Posts: 11

PostPosted: Tue 22 Sep, 2009 2:24 pm    Post subject: blade steel and izod impact tests         Reply with quote

Howdy folks.

I have been looking at various heat treating books, and I have noticed something interesting. The izod impact test information. These tests hit a notched bar with a certain weight and check the amount of energy absorbed after fracture, basically a measure of ductility. The thing I noticed is the extremely low izod impact numbers for any medium to high carbon matter what the tempering done. The numbers go from 40-50 for 1030 steel to around 5-10 for 1060 - 1095 steels. Granted the 1030-1040 steels can't be hardened very well, but anyone have any thoughts on the impact toughness. Why would a 1040 steel not be favored over a 1070 steel. Is the izod test not a very good measure of the usability and toughness of a sword blade. I'm curious if anyone here familiar with the izod testing (or charpy) can add something here.

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Maurizio D'Angelo

Location: Italy
Joined: 09 Feb 2009
Likes: 3 pages
Reading list: 3 books

Posts: 649

PostPosted: Tue 22 Sep, 2009 5:15 pm    Post subject:         Reply with quote

All the technical specifications of the materials already reported the data you ask.
For exsample:
steel 1070:
Hrc 50
resistance=1785 N/mmq
crash test = 19 Joule (Diam. 5mm charpy) here your answer.
I hope this is helpful
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Aleksei Sosnovski

Joined: 04 Mar 2008

Posts: 313

PostPosted: Tue 22 Sep, 2009 11:51 pm    Post subject:         Reply with quote

Sword blade needs to have several qualities.

For reenactment blades with thick rounded "edges" softer spring steel may be used (40-45 Rc I think. Softer means tempered that way, because any steel that contains at least 0.45% of carbon will be too hard and brittle for a sword after quenching). Such steel is more resilient and thanks to thick edges the sword still will not get deep nicks.

However for a sharp sword or a sword with a blunt but thin edge softer steel is not very good. On an strong edge-to-edge contact with harder blade the softer sword will get a deep nick which is a stress point that eliminates any advantages of more resilient steel. Also on a sharp sword the edge will roll on contact with opponent's weapons and armor and thus will very quickly become too dull to cut effectively. So hardness is also very important. And the last but not least, sword must be able to withstand continuous dynamical loads. When a sword is being used metal tends to "get tired", microscopic cracks appear and eventually the blade breaks.

Steel with higher carbon content is usually used for several reasons. First, it is easier to harden (can be hardened in oil instead of water, will harden to greater depth and is less likely to develop soft spots). For same reasons alloy steels are being used. Plus alloy steels can be much better than carbon steels in other aspects (hardness, resilience, abrasion resistance, etc. depending on particular steel). Second, it is often easier to get because it is a common tool steel. And third, it is often of higher quality because it is tool steel. the last two points are at least true for me: I cannot get decent quenchable carbon steel with less than 0.8% carbon. Damn it, I want to make hardened armor and I want something like 1040 steel for that!

In conclusion I would like to say that it is not really important whether 1050 or 1095 steel is used for a sword (considering that both steels are of equal quality and differ only in carbon content). What really matters is the quality of the heat treatment.
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