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Go to Grandus(Armor Vendor) and get quest : Faulty Shield.

Chain of quests:
1. Faulty Shield
2. One-Day Workshop Experience
3. Check Out Iron Ore
4. Magnetite in Storage
5. Workshop Forge

After completing #5, the knowledge "Refining a Steel Sword" will be available.

Continue the quest for the next knowledge.
6. Workshop Refining Technique

After completing #6, the knowledge "Calpheon Workshop Refining Method" will be available.

Continue the quest for the next knowledge.
7. Finished Goods Delivery
8. Apprentice Manager Certificate

After completing #8, the knowledge "Calpheon Workshop Apprentice Recruitment" will be available.