Ethnographic Arms & Armour - View Single Post - Scottish Late 18th Century Blade

kronckew · 3rd December 2018, 07:56 AM

Have a look at https://hal.archives-ouvertes.fr/jpa-00222126/document

It also has a list of references at the end which may be useful.

Are you talking about heat treatment of steel, or just the tempering phase.

A synopsis of heat treating, the simple version:

High carbon steel, which can be hardened and tempered was not a science, but an art until the19c, but was done since the early Greeks.

HC Steel is heated to critical temp - around 800C. where it becomes non-magnetic. smiths often have a high strength magnet handy to check. It can then be quenched in the fluid most proper for the steel, ranging from air, water, various oils, etc. Historicaly even plunging into slaves, the blood would add a bit of case hardening carbon. when quenched, the steel is hard and a file (itself a hardened steel) will skate over it rather than cutting in. It is also brittle and can break if dropped or stressed.

It must be tempered, reheated well below the critical temp which reduces the hardness and 'toughens' the steel. The temperature is judged by eye by the smith, based on the colour the steel assumes, a nice blue is typical. More scientificly they can be heated in a modern temp. controlled oven to the temp. recommended by the steel supplier. It is then quenched in fluid again to lock the crystalline structure. The degree of tempering ischosen to give the required hardness, if too little, the edge will still chip brittley or too much and it will be too soft to hold an edge. This in the 18th century was still an art and results varied based on the competence of the smith.

Get it wrong, "lose your temper",and you may need to normalize or anneal the steel by re-heating it to critical and letting it slowly cool, either in air or packed in insulation, to reset the steel back to where it was before you heat treated it.

You can also 'differentially' heat treat by using an insulator like clay on parts of the blade, and/or by forge welding different carbon content steels on edgeg and the spine. when quenched you can get a hard edge for sharpness retention, and a softer spine for strength.

I've seen a Nepali Kami (smith) Harden AND temper a khukuri by heating it to critical, then pouring boiling water from a kettle onto the edge, but not the spine, the edge hardens, the spine cools slower & tempers itself. The kami allowed to do this is usually a master with a lot of skill. It's one form of differential heat treating.

Pattern welding to combine known high carbon steel to milder steel, then heat treating is also done, and called 'damascus'. It still has to be heat treated.

The answer to your question is 'probably', depends on how good the maker was. Some were likely very well tempered, some not so well. Depends on the maker and the acceptance standards and test of the purchaser. A good blade will pass the british proof tests, bending rather than snapping in two, but springing back in line. You probably should not try that at home.

19c they got better steels and better contolled heat treatments.

3rd December 2018, 07:56 AM	#2
kronckew Member Join Date: Mar 2006 Location: Room 101, Glos. UK Posts: 4,150	Have a look at https://hal.archives-ouvertes.fr/jpa-00222126/document It also has a list of references at the end which may be useful. Are you talking about heat treatment of steel, or just the tempering phase. A synopsis of heat treating, the simple version: High carbon steel, which can be hardened and tempered was not a science, but an art until the19c, but was done since the early Greeks. HC Steel is heated to critical temp - around 800C. where it becomes non-magnetic. smiths often have a high strength magnet handy to check. It can then be quenched in the fluid most proper for the steel, ranging from air, water, various oils, etc. Historicaly even plunging into slaves, the blood would add a bit of case hardening carbon. when quenched, the steel is hard and a file (itself a hardened steel) will skate over it rather than cutting in. It is also brittle and can break if dropped or stressed. It must be tempered, reheated well below the critical temp which reduces the hardness and 'toughens' the steel. The temperature is judged by eye by the smith, based on the colour the steel assumes, a nice blue is typical. More scientificly they can be heated in a modern temp. controlled oven to the temp. recommended by the steel supplier. It is then quenched in fluid again to lock the crystalline structure. The degree of tempering ischosen to give the required hardness, if too little, the edge will still chip brittley or too much and it will be too soft to hold an edge. This in the 18th century was still an art and results varied based on the competence of the smith. Get it wrong, "lose your temper",and you may need to normalize or anneal the steel by re-heating it to critical and letting it slowly cool, either in air or packed in insulation, to reset the steel back to where it was before you heat treated it. You can also 'differentially' heat treat by using an insulator like clay on parts of the blade, and/or by forge welding different carbon content steels on edgeg and the spine. when quenched you can get a hard edge for sharpness retention, and a softer spine for strength. I've seen a Nepali Kami (smith) Harden AND temper a khukuri by heating it to critical, then pouring boiling water from a kettle onto the edge, but not the spine, the edge hardens, the spine cools slower & tempers itself. The kami allowed to do this is usually a master with a lot of skill. It's one form of differential heat treating. Pattern welding to combine known high carbon steel to milder steel, then heat treating is also done, and called 'damascus'. It still has to be heat treated. The answer to your question is 'probably', depends on how good the maker was. Some were likely very well tempered, some not so well. Depends on the maker and the acceptance standards and test of the purchaser. A good blade will pass the british proof tests, bending rather than snapping in two, but springing back in line. You probably should not try that at home. 19c they got better steels and better contolled heat treatments. Attached Images Last edited by kronckew; 3rd December 2018 at 09:13 AM.