The history of welding: from forge welding to arc and laser

Joining two pieces of metal into one is one of the most basic tasks in metalworking. The idea is ancient, but the methods a welder uses today are predominantly less than a hundred and fifty years old. The history of welding is the story of how electricity, gas and later light replaced the hammer as the tool that binds steel together — and how a craft became a regulated, documented trade.

§The oldest welding: hammer and glow

The original welding method is forge welding, which dates back to the bronze and iron ages. The principle is simple to describe and difficult to execute: two pieces of iron are heated white-hot in the forge and then hammered together so the surfaces melt into each other and become one piece. It requires the right temperature, clean surfaces and perfectly timed hammer blows. For thousands of years this was the only way to 'weld' — and the smith's skill was crucial to whether the joint held.

Forge welding had its limits. It was best suited for small assemblies, and every single joined piece required time at the forge. Large structures were instead assembled with rivets and bolts — think of iron bridges and ship hulls from the 1800s, which were riveted, not welded.

§1800s: electricity and flame are discovered

The modern foundation for welding was laid in the 1800s. Early in the century the electrical arc was described when it was discovered that current arcing across a gap develops intense heat. In the 1880s this arc was used for welding — first with ball electrodes where the heat from the arc melted the metal. Soon after came the idea of using a metal electrode that itself melts and becomes the added material.

At the same time, gas welding was developed around the beginning of the 1900s when it was discovered that a mixture of acetylene and oxygen burns hot enough to melt steel. Gas welding quickly became widespread because it required no power source and provided good heat control — and it is still used for heating, brazing and certain repairs.

§The coated electrode

An important step was the coated electrode, which was developed in the early 1900s. The coating around the metal wire created a more stable arc and formed a protective slag and gas over the weld pool, so the oxygen and nitrogen in the air would not damage the weld. Manual arc welding with coated electrode—MMA—was for many years the dominant method and is still invaluable for construction and repair work, especially outdoors.

“When people learned to protect the weld pool from air welding became reliable enough to carry bridges and ships. The rest of the 1900s was about making it faster cleaner and easier to control.”

§The two world wars and the new methods

The need to build ships, vehicles and aircraft quickly in the first half of the 20th century put enormous impetus behind welding technology. Two methods, still the backbone of modern welding, were developed in this period: TIG welding with the non-melting tungsten electrode under inert gas was perfected and patented in the early 1940s, and MIG welding — wire welding under gas protection — followed in the late 1940s. The MAG variant with active shielding gas for steel came in the following decades.

§From craft to regulated trade

As welded structures came to bear life and load — buildings, cranes, pressure vessels, district heating pipes — it was no longer enough that a joint 'looked good'. A need arose to be able to document that the weld actually held. This led to the standards and certification system that characterizes the profession today: qualification of welders, approved welding procedures, and inspection of finished welds. The health risks of welding fumes were eventually also recognized, and working environment rules and training in safe work followed.

I Danmark er denne udvikling tæt knyttet til arbejdsmarkedsuddannelserne — AMU-systemet — der gør det muligt for både unge og erfarne at bygge konkrete svejsekompetencer op trin for trin og certificere sig inden for de metoder, de arbejder med. Svejsning gik dermed fra at være noget, man lærte ved sidemandsoplæring, til et fag med formel uddannelse, prøver og papirer.

§Welding today

The modern welder has a broad arsenal: MMA for robust outdoor work, MIG and MAG for production, TIG for fine and stainless work, plus gas welding and thermal cutting. In industry, welding robots take over long, uniform series, while humans remain essential for the complex, the crooked and what cannot be turned to the easy position. Newer processes like laser welding push the boundaries further.

But underlying all the advanced work lies the same basic idea as in the blacksmith's forge thousands of years ago: two pieces of metal must become one, and the joint must be strong and clean. The difference is that while the old blacksmith only had his glow and his hammer blow, the modern welder has electricity, gas, light, protection, standards and documentation — and can thus bind steel together in ways no blacksmith in ancient times could have dreamed of.