Final answer:
The best mechanical properties for crane hooks formed from mild steel would likely be achieved at a forging temperature of 1000°C, resulting in good toughness and strength. Forging at 200°C can make the steel harder but more brittle, whereas forging at -50°C is impractical and would result in a hook with a high risk of fracturing.
Step-by-step explanation:
The mechanical properties of mild steel specimens that are forged to form crane hooks at different temperatures will vary significantly. When steel is forged at 1000°C, it is at a high temperature that allows for good workability and ductility, making it the optimal condition for forming crane hooks. Forging at this temperature should result in a hook with good toughness and strength.
Forging mild steel at 200°C is below its recrystallization temperature, which would lead to less desirable mechanical properties compared to the high-temperature forging. The material may be harder and stronger, but it would also be more brittle and less ductile, increasing the likelihood of failure under stress.
Forging at -50°C is not practical for mild steel, as metals become much more brittle at such low temperatures. The formation of a crane hook at this temperature would likely result in a very brittle product with a high risk of fracturing under normal use.
In conclusion, the best mechanical properties would likely be achieved in the hook forged at 1000°C, with the worst properties expected from the hook forged at -50°C.