The Refinery [錬結] is where you can use swords that you no longer want or need to strengthen the stats of other swords. Refining can only strengthen Impact (打撃), Leadership (統率), Mobility (機動), and Impulse (衝力).
The stats added depend only on the sword used for Refining.
The first page lets you choose the sword you want to Refine, and the second page allows you to choose up to 5 swords as Refining material.
This can be considered an alternative to scrapping the swords in the [刀解] tab in the Forge.
You will lose all bonus stats after a sword reaches upgraded (特) status(Level 20 or 25) or achieves Kiwame (極) status. Try not to waste a lot of time and spare swords from refining if your sword is close to upgrading into their Toku form.
For every sword there is a maximum cap on the bonus stats gained from refining, for both their normal and upgraded forms. The absolute maximum stats for Toku and Kiwame swords can be found on the Sword Stat List.
Swords must fulfill the following conditions to show up as a sword to consume:
Be unlocked from the Formation menu (by default)
Are unassigned to any parties
Are not in Internal Affairs
Swords that are consumed will have any equipped troops and horses automatically removed and returned to the inventory.