Which metal is used to make alloy steel for armour plates, safes and helmets

Options

A. Al
B. Mn
C. Cr
D. Pb

Explanation

To determine which metal is used to make alloy steel for armor plates, safes, and helmets, we can analyze the options provided:

1. **Understanding the context**: Alloy steel is a type of steel that is alloyed with various elements to improve its properties. In the case of armor plates, safes, and helmets, the alloy must provide strength, durability, and resistance to impact.

2. **Evaluating the options**:
- **Aluminium**: While aluminum is lightweight and has good corrosion resistance, it is not typically used in high-strength applications like armor plates.
- **Magnesium**: Magnesium is a lightweight metal, but it is not commonly used in steel alloys for armor applications.
- **Chromium**: Chromium is known for its hardness and is commonly added to steel to improve its strength and corrosion resistance. It is a key component in stainless steel and is often used in high-strength alloys for armor and protective gear.
- **Lead**: Lead is a heavy metal that is not suitable for structural applications due to its softness and density.

3. **Conclusion**: Based on the properties of the metals and their common applications, the metal used to make alloy steel for armor plates, safes, and helmets is **Chromium**.

### Final Answer:
**Chromium** is the metal used to make alloy steel for armor plates, safes, and helmets.