science

Fusion welding

Fusion welding is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Fusion welding rather than just read about it. In short: Fusion welding is a generic term for welding processes that rely on melting to join materials of similar compositions and melting points. Due to the high-temperature phase transitions inherent to these processes, a heat-affected zone is created in the material (although some techniques, like beam welding, often minimize this effect by introducing comparatively little heat into the workpiece).

Key takeaways

Fusion welding belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Fusion welding to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Fusion welding from memory before moving on to harder problems.

Reference excerpt

Fusion welding is a generic term for welding processes that rely on melting to join materials of similar compositions and melting points. Due to the high-temperature phase transitions inherent to these processes, a heat-affected zone is created in the material (although some techniques, like beam welding, often minimize this effect by introducing comparatively little heat into the workpiece). In contrast to fusion welding, solid-state welding does not involve the melting of materials.

Applications Fusion welding has been a critical factor in the creation of modern civilization due to its vital role in construction practices. Besides bolts and rivets, there are no other practical methods for joining pieces of metal securely. Fusion welding is used in the manufacture of many everyday items, including airplanes, cars, and structures. Beyond construction, a large community uses both arc and flame contact welding to create artwork.

Types

Electrical

Arc Arc welding is one of the many types of fusion welding. Arc welding joins two pieces of metal together by using an intermediate filler metal. The way this works is by completing an electrical circuit to create an electrical arc. This electrical arc is 6500 °F (3593 °C) in its center. This electrical arc is created at the tip of the filler metal. As the arc melts the metal, it is moved either by a person or a machine along the gap in the metals, creating a bond. This method is very common as it is typically done with a hand held machine. Arc welding machines are portable and can be brought onto job sites and hard to reach areas. It is also the most common method of underwater welding. Electrical arcs form between points separated by a gas. In the process of underwater welding a bubble of gas is blown around the area being welded so that an electrical arc may form. Underwater welding has many applications. Ship hulls are repaired and oil rigs are maintained with underwater arc welding. Resistance welding is done using two electrodes. Each comes into contact with one of the pieces being welded. The two pieces of metal are then pressed together between the electrodes and an electric current is run through them. The pieces of metal begin to heat up at the point where they come into contact. The current is passed through the metal until it is hot enough that the two pieces melt and conjoin. As the metal cools the bond is solidified. This process requires large amounts of electricity. In most cases transformers are needed to provide enough amps. Resistance welding is a very prevalent form of fusion welding. It is used in the manufacturing of automobiles and construction equipment.

Laser beam Conduction welding, also known as laser beam welding or radiation welding, is a highly precise form of fusion welding. "Laser" is an acronym for Light Amplification by Stimulated Emission of Radiation. The laser emits light in bursts called pumps. These bursts are aimed at the seam of the metals desired to be conjoined. As the laser bursts it is guided along the seam. These intense bursts melt the metal. The two metals when melted mix with each other. Once it has cooled the seam created is a strong bond. Lasers are efficient because they can be configured to make multiple welds at once. The laser beam can be split and sent to multiple locations greatly reducing the cost and amount of energy required. Laser beam welding finds applications in the automotive industry.

Induction Induction welding is a form of resistance welding. However, there are no points of contact between the metal being welding and the electrical source or the welder. In induction welding a coil is wrapped around a cylinder. This coil causes a magnetic field across the surface of the metal inside. This magnetic field flows in the opposite direction of the magnetic field on the inside of the cylinder. These magnetic flows impede each other. This heats the metal and causes the edges to melt together.

Chemical

Oxyfuel Flame contact is a very common form of welding. The most popular kind of flame contact welding is oxyfuel gas welding. Flame contact welding uses a flame exposed to the surface of the metals being welded to melt and then join them together. Oxyfuel uses oxygen as a primary ignition source in tandem with another gas such as acetylene to produce a flame which is 2500 °C at the tip and 2800-3500 °C at the tip of the inner cone. Other gasses such as propane and methanol can be used for oxyfuel welding. Acetylene is the most common gas used in oxyfuel welding.

Solid reactant Solid reactant welding uses reactions between elements and compounds. Certain compounds when mixed create an exothermic chemical reaction, meaning they give off heat. A very common reaction uses thermite, a combination of a metal oxide (rust) and aluminum. This reaction produces heat over 4,000 °F (2,200 °C). Solid reactant compounds are channeled to the two pieces of metal being joined. Once in place, a catalyst is used to start the reaction. This catalyst can be a chemical or another heat source. The heat created melts the metals being joined. Once it cools, a bond is formed. From welding together train tracks to entering bank vaults, solid reactant welding has many niche uses.

See also Autogenous welding – Form of welding where no additional filler material is added

References

Illustrations

Worked examples

Example 1 — a first encounter with Fusion welding

Start with the simplest possible case. Write down what Fusion welding claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Fusion welding before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Fusion welding ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Fusion welding

In research: Fusion welding appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Fusion welding in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Fusion welding is common in secondary-school and first-year university syllabi. It links to neighbouring topics Welding, so understanding it makes those chapters shorter.
In everyday life: Look for Fusion welding outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Fusion welding in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Fusion welding means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Fusion welding out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Fusion welding in simple terms?

Why does Fusion welding matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Fusion welding?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Fusion welding.