In my last fort I had excessive amounts of copper and silver, no tin, and very limited iron/steel (just enough to equip a decent military), so I levelled my weaponsmith up on copper/silver trap components. Then after getting legendary and beginning work on the good weapons for the military, he died in an extremely stupid way and - still having hundreds of silver/copper - I levelled a new weaponsmith from novice to legendary on more terrible trap components. I even melted and reforged the lower quality ones, and of course used masterpiece mechanisms, so they were about as good as copper/silver traps can get. I lined a loooong corridor with them and the results were hilarious: apparently silver and copper don't penetrate goblin iron armor too well. I had goblins dodging all the way down the corridor and back up it, I would lock them in there for months as the traps reactivated and continually failed to scratch them. I eventually saw a few goblins get over-exerted from dodging, and finally dying when they collapsed from exhaustion (although most took a lucky hit that severed an exposed hand/foot before they got exhausted, then gave in to the pain).
And the best part - after an epic battle between my military and a siege, the only survivor on either side was an incredibly skilled lasher just hanging out on my traps refusing to die. So I rounded up 5 or 6 peasants, put them in my best steel, and sent them in. Of course, a copper whip goes through masterpiece steel as if it was paper, I watched in horror as every peasant died the same way: first whip attack punched through the armor and shattered a bone, peasant gives in to pain, peasant collapses on my own traps and gets finely minced through multiple layers of masterpiece steel by silver/copper serrated blades.
Lesson learned: no matter how bad the trap components, no matter how good the armor, if you can get anyone to fall unconscious on traps (even a friendly), they won't be getting back up.