Techniques of folding modern steel

[Habaxi]

Do you know any techniques that a swordsmith can do to reduce the damage when folding a katana made of modern steel?, as you know modern steel is already pure and dont need folding, the folded ones are only for Aesthetics like (hada) appearance or just Japanese traditions, so folding it reduce the carbon content as the result of repeated heating which is also known as (annealing the steel), i heard that you can fold it but with certain techniques that reduce the loss of carbon, i already know about the tatara furnace but modern steel katanas mostly isnt made in it cuz its an  Expensive and time consuming method for a modern katana. 

[ROKUJURO]

Haidar,

you probably did not mean "folding a KATANA", but folding and fire-welding the steel.

You are completely correct, folding modern steel to itself makes no sense. This is of course different in case you want to make a modern Damascus steel, using at least 2 different steel alloys. But that is not what you want in a KATANA.

There are indeed methods to reduce carbon loss in fire-welding: 

1) You need a big fire so very little oxygen can reach the steel.

2) Charcoal as energy supplier is better than mineral coal

3) Keeping the billet well covered with clay slurry before heating up

4) Keeping the welding temperature as low as possible

5) Using a flux like borax or rice-straw ashes

6) Starting the process with a high-carbon low-alloy steel so that after the forging, the blade retains a carbon content of about 0,7 or 0,8 % of carbon in the cutting edge.

X) there are still more methods like keeping oxygen away by wrapping the billet in stainless steel foil a.s.o.  

"KATANA" has no plural form.

[AlexiG]

It all depends on the composition of the steel. There was a video of working on a billet of tamahagane steel and it is malleable and foldable at a given Japanese forge temperature, while western steel was very brittle with the same process. 

Bugei use a mix of T-10 and 1055 steels for their swords and they are managing multiple folds OK. Many Japanese smiths have forged pieces with western steel successfully. Not sure how they managed it but my suspicion is that they worked at higher temperature.

 

Some of that is in this thread:

 

[Bazza]

A darn good re-read from 2010.  Thanks Alexi.  So much to read, so little time...

 

BaZZa.

[Habaxi]

9 hours ago, ROKUJURO said:

Haidar,

you probably did not mean "folding a KATANA", but folding and fire-welding the steel.

You are completely correct, folding modern steel to itself makes no sense. This is of course different in case you want to make a modern Damascus steel, using at least 2 different steel alloys. But that is not what you want in a KATANA.

There are indeed methods to reduce carbon loss in fire-welding: 

1) You need a big fire so very little oxygen can reach the steel.

2) Charcoal as energy supplier is better than mineral coal

3) Keeping the billet well covered with clay slurry before heating up

4) Keeping the welding temperature as low as possible

5) Using a flux like borax or rice-straw ashes

6) Starting the process with a high-carbon low-alloy steel so that after the forging, the blade retains a carbon content of about 0,7 or 0,8 % of carbon in the cutting edge.

X) there are still more methods like keeping oxygen away by wrapping the billet in stainless steel foil a.s.o.  

"KATANA" has no plural form.

 

9 hours ago, ROKUJURO said:

Haidar,

you probably did not mean "folding a KATANA", but folding and fire-welding the steel.

You are completely correct, folding modern steel to itself makes no sense. This is of course different in case you want to make a modern Damascus steel, using at least 2 different steel alloys. But that is not what you want in a KATANA.

There are indeed methods to reduce carbon loss in fire-welding: 

1) You need a big fire so very little oxygen can reach the steel.

2) Charcoal as energy supplier is better than mineral coal

3) Keeping the billet well covered with clay slurry before heating up

4) Keeping the welding temperature as low as possible

5) Using a flux like borax or rice-straw ashes

6) Starting the process with a high-carbon low-alloy steel so that after the forging, the blade retains a carbon content of about 0,7 or 0,8 % of carbon in the cutting edge.

X) there are still more methods like keeping oxygen away by wrapping the billet in stainless steel foil a.s.o.  

"KATANA" has no plural form.

Thank you for your effort. English is not my first language, and I thought that "katana" referred to the blade itself without considering the other parts (that's why I said "folding a katana"). Thank you again for correcting me.

 

 

[ROKUJURO]

Haidar's question was, in principle,

"Do you know any techniques that a swordsmith can do to reduce the damage when folding modern steel to make a KATANA?" 

I tried to answer to this.

I do not think that ORANDA TETSU or NANBAN TETSU have to do with this, but taking up this subject, I would like to remind that European steel of these times (about 1600, plus/minus 100 years) was made in big quantities, but as a raw, impure material. It had to be treated with the OROSHIGANE process to make it suitable for sword making.

And of course there were no secret ORANDA techniques to make this a superior steel other than what Europeans were used to do. This was basically the reduction of carbon as the steel was first produced as cast iron in the early blast-furnaces of the time.

And finally, as mentioned by Eric, it is likely that the VOC only traded the steel, but it was very probably not made in Holland.