In the process of welding metals like stainless steel and aluminium

Options

A. oxyacetylene flame is used
B. liquid helium is used
C. liquid oxygen is used
D. liquid nitrogen is used.

Explanation

To solve the question regarding the welding process of metals like stainless steel and aluminum, we will follow these steps:

### Step-by-Step Solution:

1. **Understanding Welding**: Welding is a process used to join two or more materials, typically metals, by applying heat, pressure, or both to create a strong bond.

2. **Types of Welding**: There are various welding techniques, but for metals like stainless steel and aluminum, specific methods are preferred due to their properties.

3. **Oxy-Acetylene Welding**: One of the most common methods for welding metals such as stainless steel and aluminum is oxy-acetylene welding. This technique uses a flame produced by burning acetylene gas in the presence of oxygen.

4. **Components of Oxy-Acetylene Flame**:
- **Acetylene**: A colorless gas (chemical formula C2H2) that burns with a bright flame.
- **Oxygen**: A gas that supports combustion and is essential for achieving the high temperatures needed for welding.

5. **Process**: In the oxy-acetylene welding process, acetylene is ignited in a controlled environment with oxygen, creating a flame that can reach high temperatures (around 3,200°C or 5,792°F). This heat is sufficient to melt the edges of the metals being joined, allowing them to fuse together.

6. **Application**: This method is particularly effective for welding stainless steel and aluminum due to its ability to produce a concentrated heat source, which is necessary for these metals.

7. **Conclusion**: Therefore, the correct answer to the question is that in the process of welding metals like stainless steel and aluminum, an oxy-acetylene flame is used.

### Final Answer:
In the process of welding metals like stainless steel and aluminum, an oxy-acetylene flame is used.

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