Can you MIG weld mild steel to stainless steel? The short answer is, in most cases, yes and an ER309L filler metal is typically used. However, understanding the nature of stainless steel and MIG is helpful to best tackle this dissimilar-metal joining application. In this article we will discuss how this process is possible and what its applications are.
Why Join Mild Steel to Stainless Steel
Mild steel, as used in this article, refers to a wide range of steel grades/compositions having a relatively low overall alloy composition. On the other hand, stainless steel has a chromium content above 11% so that the surface of the steel forms a protective layer of chromium oxide. The chromium oxide layer provides enhanced corrosion resistance compared to mild steel in many applications. Despite this benefit, there are many applications where you might mix mild steel and stainless steel.
Cost is often the driving force behind the dissimilar joining: stainless steel is significantly more expensive than mild steel. Combining mild steel and carbon steel is one way to control the cost of a component while still ensuring that corrosion resistance is available in key areas. However, dissimilar-metal welding can sometimes be used to better allow components to carry required stresses, and in some cases, do so at a minimal component weight.
An Introduction to MIG
MIG is an acronym that represents Metal Inert Gas welding. MIG is one of many arc welding processes—processes that utilize an electric arc to melt the base metal and filler metal. A defining feature of the process is that it is a “wire-fed process” meaning that a continuously fed wire is used to maintain the electrical arc and provide filler metal into the weld joint. As the acronym suggests, MIG is also defined by the use of a shielding gas having generally inert characteristics that displaces the atmosphere from the weld zone to protect against detrimental reactions.
MIG is a very common process for welding mild steel, welding stainless steel, and welding these two metals to each other. MIG can be used with a range of shielding gasses and wire diameters to fine-tune performance for a wide range of material thicknesses. Because there is no slag, deposition efficiency (the ratio of filler metal consumed versus completed weld weight) is quite high. Because there is limited need for stop/starts and post-weld cleanup, operator factor (time spent welding versus total project time) can be much higher than other processes. These factors combine with the ability to achieve high travel speeds to produce a productive process. If you don’t currently own the equipment needed for MIG welding, welder rentals can be a way for you to become familiar with the process or tackle short-run production with limited investment.
How to Weld Mild Steel to Stainless Steel
Typically, ER309L filler metals are used to join mild steel to stainless steel. ER309L is a filler metal classification that designates:
- That the filler metal can be used as an electrode for MIG or as a rod for TIG
- That the filler metal has a 309 nominal alloy composition
- That the filler metal is a low-carbon variant of the 309 nominal composition
ER309L is an austenitic stainless steel that is high in both chromium and nickel. The presence and quantity of nickel in this alloy helps to form a ductile weld microstructure. ER308/308L is a popular choice for joining 304/304L stainless steel to itself, but attempting to use this alloy for steel to stainless steel instead of ER309L may result in a crack-susceptible microstructure.
Shielding gas selection can influence the ease of welding and the quality of the results. Typically high-argon shielding gasses are used. 98% Argon/2% Oxygen or 98% Argon/2% Carbon Dioxide (CO2) are used for welding thicker materials, since these gasses help to achieve a smooth, stable spray transfer with minimal chemical interaction. Three-component gas mixtures, known as “tri-mixes”, typically consist primarily of helium with varying additions of argon and carbon dioxide. While not required for thin materials, they can offer improved performance when welding using the “short-circuit” mode of transfer commonly employed to help prevent burn-through or weld out of position.
Selecting parameters for steel to stainless steel weld joints is very similar to selecting parameters for welding stainless. The stainless filler metal requires a lower current to melt-off than mild steel filler metal, so expect to utilize lower wire feed speeds than you may be used to. Likewise, the weld pool will be more “sluggish” than when welding using mild steel filler metal, and penetration will be reduced. This means that you may need to use a wider included/bevel angle depending on the application to ensure good root and sidewall fusion. Try to avoid excessive heat input to minimize the risk of sensitization of the stainless steel base metal that can negatively affect corrosion resistance of that base metal.
Be aware that the finished weld is a mixture of alloys; the corrosion resistance of the weld metal will not be equivalent to the stainless steel base metal, and it may be important to locate these dissimilar weld joints away from sources of corrosion in some situations. Also be aware that not all stainless alloys are created equal. Stainless steel can be austenitic, martensitic, or ferritic which provides insight into their microstructure and typical compositions. Austenitic stainless steels—one of the most common types by tonnage—are generally easy to weld, while martensitic and ferritic stainless steels can be more of a challenge.
Next Steps
Contact us today to find the MIG welder that is best suited for the stainless to mild steel welding that you are looking to perform. “Sizing” a machine to your application can help you to get the feature set you need without unneeded expense. Our knowledgeable team can also provide guidance into the world of stainless steel and dissimilar-metal welding to help you select the best consumables, accessories, and knowledge.
Lincoln MIG welders offer many benefits for all welding businesses, no matter how big or small. The MIG welding process is most commonly used for repairs and fabrication. So, it’s wise to consider quality equipment from one of the biggest welding brands in the USA.
Learn how MIG welding works and how your shop can benefit from Lincoln MIG welders. We’ll also discuss different MIG welder models from Lincoln and their unique advantages.
What is MIG Welding And How Does it Work
Gas metal arc welding (GMAW), popularly known as MIG welding, is an arc welding process that requires a shielding gas and a solid wire that acts as an electrode and a filler metal.
The automatic wire feeder pushes the wire through the MIG gun and into the welded joint. When the electrically charged wire (from the power source) makes contact with the grounded metal, the resistance to electrical flow melts the wire and the welded material.
The MIG gun also releases the shielding gas through the nozzle as soon as you press the gun’s trigger. The shielding gas protects the joint from the atmosphere to prevent oxidation, porosity, and other weld defects. The most commonly used shielding gas for MIG welding is a mixture of 75% argon and 25% carbon dioxide. But 100% CO2, tri-mix gasses, and other gas mixtures are sometimes required. The gas selection mainly depends on the welded material, costs, and desired weld characteristics.
MIG welding is commonly used as a semi-automatic process, but it’s fully automated in large production facilities. This welding process dominates the welding industry thanks to many advantages like ease of use, fast travel speed, high deposition rate, ability to weld in all positions, low hydrogen content, minimal post-weld cleaning, and practically unlimited electrode length.
You can use the MIG welding process to weld almost all metals with exceptional weld quality. Some welders like the Lincoln Power MIG 350MP can even achieve TIG-like, “stack-of-dimes” weld appearance on aluminum with a modified MIG waveform. But unlike TIG, MIG is far faster and easier to learn.
Why Choose Lincoln MIG Welders
Lincoln Electric is one of the largest welding equipment brands in the world. With over 125 years in the industry, Lincoln serves welders from general and light fabrication to offshore, pipeline, shipbuilding, construction, power generation, and automotive industries.
Using Lincoln MIG welders has many advantages, so let’s name a few and discuss some MIG welder rentals you can get from Red-D-Arc.
Lincoln Arc Technologies
Numerous proprietary arc technologies provide Lincoln power sources with a reliable, stable arc you can count on. The Diamond Core Technology delivers a forgiving arc with low spatter and a wide voltage sweet spot for the set wire feeding speed. It makes welding steel, stainless steel, and aluminum easier, even for out-of-position welding.
More advanced welders like the Power MIG 350MP or Lincoln Power Wave machines offer patented waveform technologies like Pulse-on-Pulse and Power Mode. Specialized arc modes allow you to improve weld quality and productivity in industry-specific applications.
Reliability
Lincoln MIG welders are tough, durable, and reliable. Featuring potted and trayed PC board protection and industrial cast aluminum drives, even their least costly units offer above-average reliability.
Angled cast aluminum drive systems include split guides for excellent wire support through the entire drive system. The brass-to-brass gun bushings improve electrical current flow, while the input bushing protects the wire from damage. The internal tachometer feedback drive system maintains constant wire feed speed, which results in consistent welds. The wire drive systems may vary according to the Lincoln MIG welder model, but if their welder includes an integrated wire drive, you can count on reliable wire feeding.
Lincoln MIG welders are manufactured at ISO 9001:2000 and 14001:2004 certified facilities. These certificates mean that every Lincoln MIG welder is produced according to international environmental standards with a high-quality management system and a strong customer focus.
Ease of Use
Designed with productivity in mind, Lincoln MIG welders are quick and simple to set up. Featuring infinite adjustability, an easy-to-set wire drive, and provided settings charts, Lincoln MIG machines work well even for novice welders.
More advanced models like the Power MIG 255C and Power MIG 350MP also feature digital displays and Synergic MIG welding (Power MIG 350MP) for easier setup. While features vary between models, all Lincoln welders are relatively easy to use.
Lincoln Power MIG 180C
The Lincoln Power MIG 180C wire feed welder is a lightweight, portable MIG/Flux-cored welder that welds up to 3/16″ thick steel and aluminum. If you use a gasless flux-cored wire, you can weld up to 1/2″ thick steel.
You can deposit filler material quickly and achieve excellent penetration with the wire feeding speed (WFS) of up to 500 IPM. Plus, Diamond Core Technology and infinite voltage and WFS adjustability allow you to fine-tune your welds just right. The Power MIG 180C is designed for light industrial welding and general repairs on auto body and farm work. It’s spool gun compatible (plug and weld), and features a no-hassle tool-less design for polarity switching and wire spool mounting.
Lincoln Power MIG 255c
The Lincoln Power MIG 255C wire feed welder is far more powerful than the MIG 180C. The Power MIG 255C outputs up to 300A with a maximum WFS of 700 IPM, allowing you to weld thick materials faster with a high deposition rate. As a result, you can bridge gaps quicker and achieve excellent penetration.
While heavy at 220 lbs, the Power MIG 255C has a built-in set of wheels for efficient movement. This machine features an industrial wire drive, digital displays, a 115V auxiliary receptacle, and is spool gun ready (up to 3/64″ aluminum wire diameter). The Power MIG 255C is a powerful MIG/Flux-cored welder designed for industrial production, welding shops, maintenance, and repair work.
Lincoln Power MIG 350MP
The Lincoln Power MIG 350MP Push-Pull One-Pack is a heavy-duty multi-process welder that supports MIG, Flux-cored, TIG, and stick welding processes. But, it also includes advanced Lincoln waveforms like Pulse-On-Pulse for double pulsed MIG welding and Power Mode for low voltage application on thin materials.
The Power MIG 350MP also supports standard pulsed MIG for improved performance on thin stock, and you can use Synergic MIG for easier weld adjustments. With up to 350A and 700 WFS, you can employ advanced waveforms to weld thick metal more efficiently than with the MIG 255C. Plus, the Power MIG 350MP has a longer duty cycle than the Power MIG 255C (60% at 300A vs. 250A at 40%). The Power MIG 350MP is an excellent machine for versatile metal fabrication, auto body, and repair jobs.
If your operators must use welding processes other than MIG and FCAW, the Power MIG 350MP has the advantage. But, if you often fabricate or repair aluminum parts, the Power MIG 350MP is among the best MIG welders you can use. Thanks to Pulse-On-Pulse, you can achieve TIG-like welds using an efficient MIG welding process. Plus, the Power MIG 350MP supports a push-pull gun, which is more productive for aluminum welding than a spool gun.
Rent or Lease From Red-D-Arc
Red-D-Arc has a vast rental welding and cutting equipment fleet strategically placed across North America. Sometimes it’s not cost-effective to purchase welding equipment. While Lincoln MIG welders offer excellent quality, it may be more profitable to rent or lease their machines.
Contact us today to get a quote on welder rental rates, or ask our experts to help you choose suitable equipment. Our goal is to provide all of our customers with the right equipment for the job at hand. So, we can help you make the proper welder selection depending on which features are most needed for your application.
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?
Stud welding.
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!
