Are you a victim of inexplicable blade failure?
Mar 11, 2009 22:51:42 GMT
Post by Matt993f.o.d on Mar 11, 2009 22:51:42 GMT
So when a sword breaks the first thing a lot of people do is blame the steel. Others blame the heat treatment. After looking at the evidence, the majority blame the flubbed cut! ;D
But what if you didnt screw up the cut, and what if the steel you are using is a known quantity?
Usually the first thing that gets blamed with every broken sword is the steel or heat treatment, even when a poor cut is the simplest explanation.
Providing the steel is not something silly, and providing the cut was not screwed up, it is then worth examining the heat treatment.
Let us assume that the broken sword in question is made out of a good steel, and was not abused or subjected to a poor cut. It has broken anyway.
Heat treatment is complex, and can be ruined easily. There are many problems that can be caused by bad heat treatment. Here, I am concerned with heat treatment problems that can cause swords to BREAK.
-The steel can be overheated whilst hardening, resulting in enlarged grain; Steel has a crystalline structure, and overheating prior to the quench can lead to enlargement of the granular structure of the steel. Larger grains have fewer grain boundaries and although large grained steel can be just as hard as small grained steel, it will always be inherently weaker.
-The blade could be insufficiently tempered. Assuming the blade achieved full hardness after the quench, and was not subject to grain enlargement, but WAS insufficiently tempered to achieve a suitable temper, the steel could be left above the working hardness range, and thus would be left brittle, and easy to break. Insufficient tempering can also be the cause of edge chipping.
So if you have broken a sword whilst performing normal cutting drills, and don't feel that the breakage was the result of a poor cut or incorrect steel choice, the most sensible thing to do is to look at the fragments of steel from your broken sword. Observe the granular structure of the steel, which should be clearly visible.
-Good granular structure is fine and silky. Individual grains should be so small as to require magnification to be seen. I have heard this structure described as looking like "grey satin".
-Poor grain structure is large and coarse, with clearly visible grains.
If the broken sword has good grain structure, and assuming a poor cut was not responsible, a likely cause for failure is that the blade was undertempered. You can test for insufficient temper by applying an edge flexibility test such as the brass rod test, where the edge is flexed over a brass rod; edges that are too soft will bend, edges that are too hard will chip, good edges will flex.
If the broken sword has a nasty coarse grain structure, this is the most likely cause for inexplicable blade failure.
If you are a victim of inexplicable blade failure, please post pictures of the broken end of your blade fragments, so that we can observe the grain structure of the steel.
But what if you didnt screw up the cut, and what if the steel you are using is a known quantity?
Usually the first thing that gets blamed with every broken sword is the steel or heat treatment, even when a poor cut is the simplest explanation.
Providing the steel is not something silly, and providing the cut was not screwed up, it is then worth examining the heat treatment.
Let us assume that the broken sword in question is made out of a good steel, and was not abused or subjected to a poor cut. It has broken anyway.
Heat treatment is complex, and can be ruined easily. There are many problems that can be caused by bad heat treatment. Here, I am concerned with heat treatment problems that can cause swords to BREAK.
-The steel can be overheated whilst hardening, resulting in enlarged grain; Steel has a crystalline structure, and overheating prior to the quench can lead to enlargement of the granular structure of the steel. Larger grains have fewer grain boundaries and although large grained steel can be just as hard as small grained steel, it will always be inherently weaker.
-The blade could be insufficiently tempered. Assuming the blade achieved full hardness after the quench, and was not subject to grain enlargement, but WAS insufficiently tempered to achieve a suitable temper, the steel could be left above the working hardness range, and thus would be left brittle, and easy to break. Insufficient tempering can also be the cause of edge chipping.
So if you have broken a sword whilst performing normal cutting drills, and don't feel that the breakage was the result of a poor cut or incorrect steel choice, the most sensible thing to do is to look at the fragments of steel from your broken sword. Observe the granular structure of the steel, which should be clearly visible.
-Good granular structure is fine and silky. Individual grains should be so small as to require magnification to be seen. I have heard this structure described as looking like "grey satin".
-Poor grain structure is large and coarse, with clearly visible grains.
If the broken sword has good grain structure, and assuming a poor cut was not responsible, a likely cause for failure is that the blade was undertempered. You can test for insufficient temper by applying an edge flexibility test such as the brass rod test, where the edge is flexed over a brass rod; edges that are too soft will bend, edges that are too hard will chip, good edges will flex.
If the broken sword has a nasty coarse grain structure, this is the most likely cause for inexplicable blade failure.
If you are a victim of inexplicable blade failure, please post pictures of the broken end of your blade fragments, so that we can observe the grain structure of the steel.