Most of them are done by hand.
Welding the blade and the handle.
200 degree high temperature vacuum quenching and cold treatment - 195 degree, greatly increased the hardness and toughness of steel.

[ 4CR Steel ]
- Carbon(C): 0.36 ~ 0.45%
- Chromium(Cr): 4.75 ~5.50%
- Molybdenum(Mo): 1.10 ~ 1.60%
- Vanadium(V): 0.30 ~ 0.60%
- Manganese(Mn): 0.20 ~ 0.50%
- Silicon(Si): 0.80 ~ 1.2%
- Phosphorus(P): 0.030%
- Sulfur(S): 0.030%