TheDreamCacher & Jamesonboo made some good words about being more specific. I'll put some examples from Dull's Skill that got an upgrade.

Name: Blueprints I & II
Grade: E
Classification: Plans
Effects: List of creations.

• Iron Walls/ 4 Iron Ingots
• Cannons/ 6 Iron Ingots

• 1-handed Weapons/ 3 Iron Ingots
• 2-handed Weapons/ 5 Iron Ingots

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Before anyone ask why I asked that? It's for my story Survival and Dull's skills. I want to know what's stronger than steel so I can turn it into Ingots for Dull to create and stronger weapons for him to built. So tell me this, what is stronger than Steel?