You probably know the story about the Head of the Patent Office proposing it be closed because everything that could be invented had been. Well – spoiler alert – it’s probably an apocryphal tale, but it still tells us something: technology keeps marching onwards.
Improving on a mature process
Welding is a great example of technological advancement. You can probably name several types of welding processes, but the list keeps growing. In our fabrication shop it’s mainly MIG although we also have a couple of resistance or spot welders. (They’re particularly useful for sheet metal fabrications.)
If you watch our skilled welders at work it’s hard to believe any improvements could be possible. Welding has challenges though, which creates opportunities for innovators. In particular, we’d all like:
- Less spatter, to reduce clean-up time.
- Less heat input, to reduce distortion and help with thinner materials.
- Improved ability to weld dissimilar materials.
- Better arc control, to help address problems caused by poor fit-up.
- Faster travel, so we can make welds in less time (and put less heat in.)
Advanced welding processes
To tackle these problems, technologists developed several innovative welding processes. Six that are becoming more mainstream are:
- Magnetic arc
- Electron beam
Here’s an overview of what they are and how we might use them.
1. Magnetic arc welding
In this improvement on conventional MIG a magnetic field constrains and rotates the arc. This improves accuracy, enables faster travel and results in a clean finished appearance. It can be used anywhere MIG is used now. The equipment is more expensive, but it’s an attractive process for when aesthetics are important.
A solid-state welding process, (along with explosive and ultrasonic,) this is always fun to watch. The pieces to be joined are set moving in opposite directions, then brought together hard. Friction creates intense heat that rapidly fuses them together.
Friction welds have excellent mechanical properties, sometimes better than those of the parent materials. Porosity is rare and it works for dissimilar materials, like joining aluminum to steel. Automotive companies use friction welding extensively for tasks like joining castings to forgings.
Like friction welding, this is something of a brute force technique. A small quantity of explosive is used to press one metal hard against another, the force actually causing the metals to fuse. One of the main applications of explosive welding is cladding sheet and tube material and it’s often used in the manufacture of heat exchangers.
Consider this friction welding miniaturized. It uses extremely high frequency sound to oscillate the materials, which creates enough heat to fuse them together. The welding head, termed the sonotrode, is pressed briefly against the surfaces being joined and makes a very localized weld, much like a spot welder.
Ultrasonic welding is used extensively for plastics, and has some uses in electronics and electrical assembly. It’s not really a metal fabrication process though.
We use lasers for cutting because the thin, intense beam of light produces a lot of heat. That heat can also be used for welding. Being concentrated into a small area, laser welding is good for making narrow and deep welds at high speed. It’s particularly effective with steel, stainless steel, aluminum and titanium.
6. Electron beam
Probably the most science-fiction type of welding, this fires high energy electrons into the material where they create heat. (At heart the electron beam welder is very similar to the cathode ray system used in old TV’s.) The resulting welds are very high quality.
Electron beam welding equipment is hugely expensive, not least because it’s best done in a vacuum. It’s niche is welds that need extremely deep penetration, where it’s many times faster than arc welding.
Welding still advancing
Some welding processes have been around a long time, but that doesn’t mean it’s impossible to improve on them. We’re still a nation of inventors, even if Charles H. Duell, US Patent Office Commissioner may have thought otherwise back in 1899. Makes you wonder what will be invented next!