Fusion Welding vs Solid State Welding: Difference and Comparison

Key Takeaways

1. Fusion welding involves melting the base metals being joined, while solid-state welding does not melt the base metals. Fusion welding techniques like MIG, TIG, and stick welding melts the metals using an arc or flame to form a weld pool that cools into a joint. Like friction stir and ultrasonic welding, solid-state welding creates a bond through extreme pressure and friction without melting.
2. Fusion welds have higher strength and flexibility compared to solid-state welds. The melted and mixed metal in the weld pool creates a metallurgical bond and homogeneous joint. Solid-state welds have less mixing of parent metals resulting in lower joint strength.
3. Solid state welding is advantageous for materials sensitive to high heat like aluminum and magnesium. The lack of melting allows more control over the heat affected zone and avoids issues like alloy composition change, porosity, and embrittlement. Fusion welding can alter alloying elements in the weld area leading to weakness.

What is Fusion Welding?

Fusion welding is a type of welding process that involves joining two or more pieces of metal by melting them at the joint and allowing them to solidify into a single, continuous piece. The term “fusion” refers to the melting and blending of the base materials to create the weld joint.

In fusion welding, a heat source is applied to the materials to raise their temperature to the point where they become molten. Depending on the specific welding method, this heat source can be an open flame, an electric arc, a laser, or an electron beam. Once the materials are molten, they are brought together, and when they cool and solidify, they form a robust and metallurgical bond.

What is Solid State Welding?

Solid-state welding is a group of welding processes that create a bond between two materials without melting them into a fully liquid state. Unlike fusion welding, where the base materials are melted to form a weld, solid-state welding achieves bonding through a combination of pressure, temperature, and time, all within the solid-state phase of the materials involved. This process is also known as “solid-state bonding” or “solid-state joining.”

The absence of full melting in solid-state welding has several advantages, including preserving material properties and joining dissimilar materials that might not be compatible with traditional fusion welding methods. The process occurs at temperatures below the melting point of the parent materials, which reduces the risk of introducing defects and allows for precise control of the bonding process.

Difference Between Fusion Welding and Solid State Welding

1. The fundamental difference lies in the state of the base materials during the welding process. In fusion welding, the materials are heated to a molten state and fully melted at the joint, forming a fusion of the parent materials. In contrast, solid-state welding achieves bonding without melting the materials to a fully liquid state, preserving the original material properties.
2. Fusion welding requires relatively high temperatures to melt the base materials and create the weld joint. In solid-state welding, the temperature is lower, as the process relies on localized heating through friction, ultrasonic vibrations, or other methods, without reaching the materials’ melting point.
3. Fusion welding can cause significant distortion and residual stresses in the welded components due to the high temperatures involved. On the other hand, solid-state welding produces lower levels of distortion and residual stress since it occurs at lower temperatures and with less thermal input.
4. Fusion welding produces a continuous, homogenous joint with a complete fusion of the base materials. The joint quality might vary in solid-state welding depending on the specific process used. Some solid-state welding methods, like friction stir welding, can create joints with excellent mechanical properties and minimal defects, while others may have limitations in specific applications.
5. Fusion welding is well-suited for joining similar materials with compatible melting points. However, it may be challenging to weld dissimilar materials effectively due to their different thermal properties. On the other hand, solid-state welding offers advantages in joining dissimilar materials since it avoids full melting, allowing for the bonding of materials with significantly different characteristics.

Comparison Between Fusion Welding and Solid State Welding

Parameter of Comparison	Fusion Welding	Solid State Welding
Heat Input	High heat input, leads to the complete melting of materials	Lower heat input, reducing the risk of distortion and preserving material properties
Joint Strength	Generally strong joint due to complete fusion of materials	Strong joints, particularly in certain solid-state processes
Applicability to dissimilar	Challenging to weld dissimilar materials due to differences in melting points	Advantageous for joining dissimilar materials with differing properties
Metallurgical Changes	Can cause metallurgical changes and heat-affected zones	Minimal or no metallurgical changes since no full melting occurs
Joint defects	Prone to defects like porosity, cracks, and inclusions	Generally produces fewer defects due to lower heat input and controlled process

References

1. https://www.cambridge.org/core/journals/mrs-bulletin/article/phenomenological-modeling-of-fusion-welding-processes/04984333CB143DBF4886530F36102D5E
2. https://www.sciencedirect.com/science/article/pii/S0924013617304181

Last Updated : 27 August, 2023