What Is Iron Mixed With Phosphorus?

Under high temperature or reaction conditions
Under heating, ignition or a specific chemical environment, iron and phosphorus will react chemically:

Produce ferrophosphorus

Under high temperature (such as smelting process), iron and phosphorus combine to form iron phosphide compounds, mainly ‌Fe₂P‌ and ‌Fe₃P‌.
The product is an iron alloy containing 15%-25% phosphorus, and also contains impurities such as silicon and manganese.
‌Use‌: As a phosphorus additive in steel smelting, it improves the corrosion resistance and fluidity of metals