Name the susbtances which are mixed (allowed) with iron to make stainless steel.

Options

A. Nickel
B. Chromium
C. Aluminium
D. Both A and B

Explanation

To answer the question about the substances mixed with iron to make stainless steel, follow these steps:

### Step-by-Step Solution:

1. **Identify the Base Metal**:
- The primary component of stainless steel is iron.

2. **List the Common Alloys**:
- Stainless steel is made by adding various alloying elements to iron. The most common elements include:
- **Nickel (Ni)**: Improves corrosion resistance and toughness.
- **Chromium (Cr)**: Essential for corrosion resistance; at least 10.5% chromium is required for stainless steel.
- **Molybdenum (Mo)**: Enhances resistance to pitting and increases strength at high temperatures.
- **Silicon (Si)**: Improves oxidation resistance and strength.
- **Carbon (C)**: Increases hardness and strength.
- **Nitrogen (N)**: Enhances strength and corrosion resistance.
- **Aluminium (Al)**: Used for deoxidation and can improve corrosion resistance.
- **Sulphur (S)**: Sometimes added to improve machinability.
- **Titanium (Ti)**: Stabilizes the structure and prevents carbide precipitation.
- **Copper (Cu)**: Improves corrosion resistance and strength.
- **Selenium (Se)**: Enhances machinability.
- **Niobium (Nb)**: Stabilizes the structure and improves strength.

3. **Compile the List**:
- The substances mixed with iron to make stainless steel include:
- Nickel
- Chromium
- Molybdenum
- Silicon
- Carbon
- Nitrogen
- Aluminium
- Sulphur
- Titanium
- Copper
- Selenium
- Niobium

### Final Answer:
The substances mixed with iron to make stainless steel include Nickel, Chromium, Molybdenum, Silicon, Carbon, Nitrogen, Aluminium, Sulphur, Titanium, Copper, Selenium, and Niobium.

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