Welding is done in tiny and delicate regions of a weld and is highly precision-based. It is basically done by depositing blobs of weld to the welding joints of metals.
Here, while doing micro-welding other than the joint that is fused the other areas do not get heated up easily.
The same TIG welding equipment is used but the size of it is much smaller than a pen. This ‘Micro TIG welding’ is the latest welding technology available today. Here, a 5mm thick edge or joint can be welded down to 0.007mm weld.
Pulsed Micro TIG Welding:
When the plasma arc between the tungsten electrode and work piece is burning hot at around 5000°C is known as ‘Micro TIG Welding’. An inert gas is applied at the welding joint because it helps in removing and displacing air from that region that promotes plasma arc generation. Inert gases like Argon is generally used.
Fine Spot Micro TIG Welding:Spot welding is a highly economical and easy welding process.
It is also known as ‘Resistance Welding’. Here, we use two electrodes, a positive and a negative one and are used to make contact with the metal to be welded.
After the pressure is applied, a pinch (or) pulse of electrical current is applied at that particular joint to melt the two edges of metals to fuse them together.
As a welding spot is created, it is known as ‘Spot Weld’.
Thermocompression Micro Welding:Thermocompression micro welding is the process of welding having the highest degree of precision using a specially-designed electrode.
Here, the electrode used is uniquely used to create a tiny isolated path to weld the joint with a very controlled amount of heat supplied to it.
Hence, an excess amount of heat or energy does not conduct through the metal melting it away.
Laser Micro Welding:
Laser micro-welding is a welding technique highly used in automatic machines.
In laser micro-welding collimated, that is parallel rays of light due to electromagnetic radiation is used to fuse metals together.
Laser welding, similar to pulse welding is used for welding edges frequently and regions that are difficult to reach.
Equipment:A minimum of 300 amps power supply is the primary requirement. We need a torch with an electrode and a torch stand for it. Something that need to be checked on regularly for the quality and quantity is the shielding gas that is present in the black cylinder on the left of the image.
Micro-welding of Copper and Stainless-Steel:The trend nowadays in welding is to weld dissimilar metals that is used in MEMS devices using thin metals.
These thin metals are susceptible to heavy heat damage.
Welding extremely thin stainless-steel foil (AISI 304) with copper foils of ten-micron thickness is done using a nano-second pulsed fiber laser.
There are two modes used in welding the aluminum and copper foils and is by using “weld brazing” and “full fusion” modes.
Nano-Welding:The latest inventions in welding is the technology of “nano-welding”. Metal nanowires are joined/welded together using white light.
Touchscreens of devices and photovoltaic cells can be fused and fabricated using these nanowires.
A researcher named Erik Garnett and his colleagues of Stanford University used a technique known as the “polyol” method to manufacture these nanowires made out of silver of radius around 15-40nm in radius and 3-10nm in length.
These nanowires get a polyvinylpyrrolidone (PVP) sheath around them.
Laser Micro-Welding for Ribbon Bonding:Ribbon bonding is done by using ‘Laser micro welding’ and is one of the newest and brightest inventions used in the electronics industry where they make nanochips and nano sensors.
The bond/weld between the copper ribbon and the conductive surface is done by using ultrasonic radiation alone in the earlier days.
Nowadays a fiber laser, galvanometric scanner, and a beam focusing on the weld is used to do ribbon bonding accurately.
Micro Friction Stir Welding:
The “Micro Friction Stir Welding” process is used to weld together any kind of dissimilar metals. It is widely used in thin walls, micro- electronic and electrical devices and microchips and micro – mechanical assemblies.
This process mainly works on the thermo-mechanical principle. It was invented and optimized by Wayne Thomas and his colleagues. Here, it does not work like a normal welding process involving any kind of molten metals, red-hot fire, distortion, and spattering.
This micro friction stir welding can be carried out in aluminum, zinc, and copper alloys with dimensions less than 1000μm. The structure is fine-grained and free of coarse grains that make fusion welds prone to holes and cracks. Refined tools with accurate geometries and proper material flow are necessary for an optimal weld.
Micro Orbital Welding:Micro orbital welding is an extension of “Orbital Welding”, where the welding is done by rotating the arc by 360. °mostly around a static workpiece or in a continuous process.
Here, most of the welding process is done and controlled by a computer and its automation.
And as it is done periodically by a machine, it is done for large welding operations that require the welding to be repeated continuously.
This process was invented by Rodrick Rohrberg of North American Aviation to give the world an idea about how much fuel and fluids kept leaking in the X-15 Rocket Research plane.
- Orbital welding is used widely for thick walls, tubes of small radius and unusual metals, and parts at extremely uncomfortable conditions.
- The expense for a single weld is around 5-10 times the initial cost used to build this entire Orbital Welding setup without a compromise in the performance and productivity.
- The technique used in this welding is basically a modification of Tungsten Inert Gas (TIG/GTAW) welding using electrodes and wire feed.
- The TIG welding method is inculcated into orbital welding because the heat input is monitored and controlled using orbital welding heads.
- The metals welded here are of high tensile-strength, corrosion-resistant, and distortion-free alloys and low-alloyed metals.
Micro Fissures Welding:
The word “fissure” means a “crack”. Generally, most of the low-alloyed steels that have additional chromium and molybdenum or vanadium get cracks on their weld surfaces during the post-weld heat-treatment process.
The temperatures in the chamber during those processes are about 350°C to 500°C. Such regions are commonly called as ‘Heat Affected Zones’ (HAZ) and are located at the coarse-grained surfaces of the weld.
Micro-cracks are found as colonies having an extensive branching to its root along the HAZ and weld regions.
|Below is an example of choosing the steel of choice:|
|5 Cr||lower risk|
|2.25Cr 1 Mo||↓|
|0.5Cr 0.5Mo 0.25V||higher risk|
Sean Coby is a welder par excellence and well respected among the welding community in Woodbridge, VA. He prides himself to be the fabricator and mechanic in the automotive/ diesel industry for the past more than eight years now. As the chief editor of his https://weldinginfocenter.com, he shares his experience to be safe during welding and to take proactive steps for becoming a successful welder like him.