BUR #24690 has been approved by @nonamethanks.
create alias iron_ball -> metal_ball
create alias steel_ball -> steel_ball_(jojo)
remove alias steel_ball -> steel_ball_(jojo)
Current usage of both tags suggest as such:
Iron ball: Any ball made of metal, especially the ball and chain restraint trope.
Steel ball: Gyro Zeppeli and Wekapipo's steel balls.
Therefore, iron should be changed to metal to encompass more; steel should have a qualifier.