In traditional welding, a complex process is used to join two pieces of material (typically metals) using electricity to create a powerful arc that melts those materials, and often a filler material, to join them into one piece.
Traditional arc welding has a lot of benefits but also some drawbacks. It typically leaves a visible lump of material where the base metals were melted and fused, and this can only be cleaned up so much without weakening the weld. It can also be slow for longer or more complex welds. In particular, the weld joint usually requires a lengthy cross-section to make a strong connection.
While this is all fine for many applications – and indeed, arc welding is commonly used in many industries – its drawbacks make it less than ideal for specific situations, specifically when you want to join something with a small profile to a work surface.
Take, for example, the need to attach a bolt to a flat surface. The bolt has a small cross-section, and there’s no room for filler materials if appearances and tolerances are to be maintained.
What’s the solution?
What is Stud Welding?
Stud welding is the practice of joining two pieces of material in a weld, where one of those materials is a “stud.” A stud, or weld stud, is generally a fastener. The project requires that it be connected to the primary work surface or substrate without marring the surface or leaving unsightly or inconvenient weld beads.
Stud welding uses a process to generate a current between the fastener and the base material, creating an arc between the two, near-instantly melting them and fusing them. No filler material is needed, only a little bit of pressure.
One of the most significant advantages of stud welding is its ease of use. Stud welding is nearly an automatic process, similar to a nail gun or a staple gun. While safety protocols must be followed, there’s no need for a steady hand, knowledge of weld beads and patterns, or even concerns about the materials involved. Often, the individual using a stud welder is considered an operator, not a welder.
Another significant advantage is the speed of welding. Welding traditionally around the base of a stud in a Tee Joint would be a long, slow process with a substantial risk of inconsistency or burn-through on thinner materials.
A welding mount would help, especially if it has an auto-rotate function, but that’s not always available. Stud welding, by comparison, takes a fraction of a second to activate and fuse, dramatically speeding up the process. While the savings of half a second doesn’t seem like much, the time savings add up when you need to repeat this stud welding process dozens, hundreds, or thousands of times.
Stud welding is typically used in situations where traditional welding is insufficient or where the opposite surface of the stud cannot or should not be marred by the welding process.
It’s fast, easy, and strong and can join different materials (like aluminum, brass, copper, and steel) to one another without needing filler material.
There are multiple different kinds of stud welding systems available and a range of stud guns to apply to those welding systems. Knowing the difference can help you choose the most useful for your projects.
Stud welding is used in many applications, from HVAC insulation to metal fabrication to bridge building. It is also commonly seen in fabricating electrical enclosures and switch cabinets, vending machines, medical technology, aerospace, military applications, vehicles and shipbuilding, and much more.
Are There Disadvantages to Stud Welding?
The stud welding process is fast, effective, and extremely strong. The point of failure on a stud weld is rarely the weld itself.
It’s also straightforward to do, such that the operators don’t need to be master welders to handle stud welding equipment safely and effectively. All of that said, it’s not a perfect process, and it has a few distinct disadvantages.
One major disadvantage is that it’s not typically best used in high-strength structural steel fabrication, stainless steel, or high alloy steels. It also has a typical upper limit on how large the stud can be.
Additionally, as with all welding processes, safety is an immense concern. Even though stud welding is easy and accessible, and much of the process is handled automatically by the gun, it still requires proper protective equipment, safety equipment, and great care. It is, after all, still using a high enough blast of electricity to melt metal in an instant. Molten metal, heat, radiation, and other considerations are all important.
Stud welding is commonly handled by trained professionals or robotic equipment to mitigate many of these disadvantages, including CNC machines. Automating much of the process will remove the risk of harm from human operators while ensuring consistent, high-quality welds.
Drawn Arc Stud Welding
First, of the two main stud welding processes, drawn arc stud welding is slightly slower than the alternative. It’s also a more complex process, requiring additional parts. In exchange, it’s better for more extensive, thicker materials and heavier materials like steel.
In this process, a stud is positioned in the stud welding gun. It is firmly against the work surface and held in place using spring tension. It is then shrouded by a ferrule, a ceramic shield containing the heat of the arc and the molten metal from the weld when it triggers.
When triggered, the weld gun will lift the fastener from the work surface a predefined distance.
Simultaneously, a brief, controlled electric arc is sent into the materials, creating an arc and extreme heat between the fastener and the surface. The ferrule contains and concentrates the heat and molten material to the area of the weld; this also removes the need for shielding gas.
Once this arc is triggered, the stud gun will release the spring, plunging the stud downwards with a predetermined amount of force, merging the two molten ends of the fused materials.
Instantly, the two materials are joined in a robust and thorough weld. No additional filler or other materials are necessary.
This whole process happens in less than a second, usually on the order of 150-500 milliseconds. The machine is called a stud gun because it fires that quickly. Due to the process involved, drawn arc stud welding is typically performed on more significant and thicker materials, with more leeway and time necessary to properly melt the surface. However, that time is still measured in milliseconds.
Later, in a cleanup process, the ferrule is broken off of the weld, leaving a cleaner and specifically-shaped surface designed by the interior of the ferrule.
In some cases with huge studs, a shielding gas may be used in addition to a ferrule. A variation of drawn arc stud welding is also available, called short cycle stud welding. This variation functions similarly but uses a higher current and a shorter cycle for faster welds. This technique is typically used on materials in an awkward middle size between the sizes best handled with drawn arc stud welding and the smaller sizes best handled by capacitor discharge welding. It’s also used for aluminum stud welding. Shielding gas is also more common for this size of stud welding.
Capacitor Discharge Stud Welding
The second common kind of stud welding is capacitor discharge stud welding. As the name implies, this form of welding uses a high-powered capacitor to store energy, discharging it all at once in a flash that melts the joint’s surface and fuses two materials.
Capacitor discharge studs are typically formed with a special tip that serves as a tiny guide for the precise location of the discharge arc. Like with the alternative form of stud welding, capacitor discharge stud welding uses a spring to push the stud into the molten pool of material, making a smooth, consistent joint.
The process here is straightforward. The capacitor in the stud gun is charged, and a stud is loaded into it. The gun is then positioned and fired, automatically completing the entire process.
The gun operator needs only to load the gun and adequately place it; the machine handles everything else. This method is commonly used in automated machinery because the program can also automatically position and load.
Capacitor discharge stud welding is ideal for smaller-diameter studs and thinner base materials.
Because it happens so fast, most of the heat is limited to the stud, and only a relatively small amount of the base material is melted, reducing any chance of discoloration or marring to the reverse side of the base material.
Variations on Stud Welding
While the two main processes above are common forms of stud welding, the mechanism can also be used in other situations.
A common variation is insulation in HVAC, particularly at industrial scales. In this process, insulation is wrapped around a metal base and must be fixed; this is done using cupped pins, essentially like giant thumbtacks. These pins are the studs used in the welding process, and their tips are the contact point between the base material and the pin itself.
Stud welding processes fuse the two, and a series of such pins are used to fix the insulation in place at regular intervals across a work surface.
An alternative to this process adheres pins to the work surface upon which the insulation is placed, and the welding process applies caps to those pins. Many thermal power plants and industrial furnaces are insulated in this manner.
Sometimes, friction welding can also be used. Friction welding eschews the electric current in favor of mechanical forces. It spins the stud at a high RPM, pressing it against the work surface so that the sheer friction of the two materials heats them up to the melting point, fusing them together. Friction welding is not technically a form of stud welding. However, it does not use the same equipment, is not used for the same purposes, and operates via an entirely different mechanism.
Another variation in stud welding is nut welding. A traditional stud welding process adheres a bolt to a surface, which nuts can then be threaded onto for various fabrication purposes. The opposite process adheres a nut to the base material, into which a bolt can be threaded later.
Since nuts are circular, a different process must be used. This more complex process uses a magnetic field to rotate an arc around the circular cross-section of the nut while shielding gas protects the molten area.
This circular weld pool then receives the nut as it plunges downwards, fusing the two. The center hole can be punched out or bored to accept a bolt.
Variations on Stud Welding Guns
Stud welding guns come in a wide range of capabilities and additional features. Some can be auto-loading, allow for more than one type of welding, or have optional shield gas piping built in. The machine you choose will depend on your needs.
The three main types of stud gun welders are the resistance welding stud gun welder, the capacitor discharge (CD) stud gun welder, and the arc stud gun welder.
- The resistance welding stud gun welder is a portable, low-power machine designed for projects requiring quick and easy spot welding on thin-gauge metals such as aluminum and stainless steel. The power generated by this type of stud welder is suitable for most small welding jobs.
- The capacitor discharge (CD) stud gun welder is a more powerful yet still portable welding machine used for both thin- and thick-gauge materials. This type of stud gun welder is popular because it can create a strong weld without manually adjusting parameters like current or voltage.
- Finally, the arc stud gun welder is the most powerful of all stud gun welders. It creates an exceptionally strong weld that can hold heavy loads for long periods. While this type of stud gun welder is more expensive than the other two types, it is ideal for those who plan to do heavier-duty welding projects.
No matter which type of stud gun welder you choose, it’s important to remember that each has its own advantages and disadvantages. Therefore, choosing the style that best suits your needs and budget is essential.
Choosing a Stud Welding Gun
If you’re still determining what you’re likely to need, you can always rent stud welding machines to try them out.
Rental equipment is accessible and inexpensive compared to purchasing equipment outright, though, of course, you need to exercise due caution.
If you have any questions about the stud welding process, the various available equipment, or other general welding forms, feel free to reach out! Whether you comment on this post, please read the rest of our blog or drop us a line directly; we’re always ready to help. We’re equally available for small-time hobbyists, industrial-scale welding operators, and everyone in between. Just let us know!