Types of Welding: Homogeneous, Heterogeneous, and Soldering

Types of Welding and Soldering

Homogeneous Welding

In homogeneous welding, the metals being joined are of the same nature as the filler material.

Heterogeneous Welding

In heterogeneous welding, the materials involved are of different natures.

Soldering

Soldering is a heterogeneous weld between two metals, potentially using a filler metal ('contribution') of a different kind. It typically involves fusion materials below 450°C. Common applications include welding cables, panels, and low-resistance joints in bodywork (carrocería). The process relies on a filler metal that melts and spreads across the surface of the base metals.

Tin-Lead Solder

The melting temperature for tin-lead solder is approximately 230°C. The process involves:

1. Cleaning the surfaces
2. Scraping
3. Applying flux
4. Heating the edges of the pieces
5. Applying the solder, which melts and spreads
6. Allowing it to cool
7. Cleaning the remaining flux

Brazing

Brazing differs from soldering in that the filler metal melts between 450°C and 950°C. It can withstand greater stresses and higher temperatures.

Brass Soldering (Brazing with Brass Filler)

Used for steel parts, typically in low-stress applications, and not exceeding 700°C. The process includes:

1. Cleaning the joints with solvent
2. Scraping
3. Heating with a torch
4. Applying a brass-impregnated rod
5. Cleaning the weld once cold

Torch Welding (Oxyacetylene Welding)

Perfect combustion is achieved by mixing gases (typically oxygen and acetylene) with a torch to produce a precisely controlled flame reaching 3100°C. It's a slower process and can cause structural changes in the metals. Two key phenomena are involved:

• Mullament (Wetting): The property of a liquid to spread easily on a solid body.
• Capillarity: Occurs on the surface of a liquid in contact with a solid wall; the fluid can move more or less easily.

Deformations and Tensions

To prevent deformations and tensions, tack weld the pieces on both sides. The process is as follows:

• The distance between tack welds should be 20 to 30 times the thickness of the plate.
• The size of the tack weld should be based on the thickness of the pieces.
• Tack weld from the center towards the ends.

Torch Equipment

• Bottles of oxygen and acetylene
• Oxygen and acetylene regulators
• Gas hoses
• Check valves
• Gas control valves
• Torch nozzle and welding tip

Pressure Regulators (Manoreductors)

Their mission is to reduce and regulate the pressure to a desired value and keep it constant. Oxygen is typically regulated from 200 kg/cm² and acetylene from 15 kg/cm².

Torch (Blower)

Responsible for achieving a stable flame with high calorific power by mixing gases in appropriate proportions.

Power Calculation: 100 * e = l/h (where 'e' is the thickness).

Hoses

Made of rubber, their mission is to carry the gas from the bottle to the torch.

Safety Valves

Allow the movement of gas in only one direction.

Torch Flame

• Dart: The brightest area of the flame.
• Primary Combustion Zone: The area closely surrounding the dart.
• Reducing Zone: The area with the highest flame temperature (3100°C), producing reducing gases that protect the fusion bath.
• Formeret: The last area of the flame (where gas reactions occur).

Welding Techniques

• Leftward Welding: The welding rod follows the torch, moving to the left.
• Rightward Welding: The torch moves to the right, ahead of the rod.