Explosive Welding

This is an interesting topic. Many car enthusiasts would understand the concept of welding or soldering. These differ in two ways:
– Welding takes place at a very high temperature and literally melts the two surfaces together often using a third filler to form a very strong bond.
– Soldering is used at a lower temperature and uses a metal filler that melts at a lower temperature than the two items being connected. The molten filler then cools and bonds the surfaces together.

Car manufacturers use robots to create car shells using “resistance spot welding” that uses heat from the resistance of an electric current to melt the two sheets of steel. At the same time the robot will clamp the two pieces together to ensure a tight connection. Multiple spot welds would be used to connect the body underpinnings together.

Now engineers are working on “explosive welding” to help form car body panels rather than the large and noisy stamps that are prevalent today.

What is it?
The idea came from a byproduct of war. It was found that shrapnel was often welded to armour plating after a direct hit. Normally this would require an extreme amount of heat, however it was discovered that this could happen at room temperature if the collision was at a high enough speed – and certain chemicals were present.

Its first use was to cover steel with another substance for use in factories where plates were needed for further chemical reactions. Simply put, explosives were used to throw a nickel alloy against the steel plate and bingo it was covered! Engineers in France have figured out that they can replicate the process without the explosives – thus making it much safer! They have also figured out that they can weld and shape components at the same time and importantly they can bond different materials using this method, now called Magnetic Pulse Welding.

Rather than using a tunnel under a mountain as they used to do with the explosives, the boffins can now do this in millimetres! The shaping of parts still needs a mould however without the need for a heavy mechanical stamp. The benefits seem to be quite widespread: the process uses less energy and therefore uses less heat. It is quieter and apparently the welds look better and are as strong as normal welding. The stamping is apparently sharper as well providing a more visual appeal to the panel.

This potentially would make the carbon footprint lower for each vehicle built and would reduce wastage along the way too. By bonding different materials together also reduces the need to sandwich together the materials for strength and thus would provide a better looking and lighter finished product.