As vehicle manufacturers continue to use ultra-high-strength steel (UHSS), advanced high-strength steel (HSS) and other forms of HSS, traditional welding methods don’t always fit the bill — especially when high heat could compromise structural integrity. That’s where metal inert gas (MIG) brazing, an increasingly recommended attachment method, plays a crucial role.
MIG brazing offers a unique solution for joining different types of steel. While this method is being specified more frequently in OEM repair procedures, many technicians are still unfamiliar with how to properly execute it.
Let’s explore the science, equipment, training and real-world application of MIG brazing.
Why MIG Brazing?
MIG brazing continues to gain traction in the collision repair industry for one core reason: heat sensitivity of modern vehicle materials. Vehicle makers are using more advanced HSS and UHSS in key structural and reinforcement areas — such as around the cabin or within door rings — to absorb and manage crash energy. These materials are extremely sensitive to heat.
Traditional MIG welding can alter the molecular structure of these metals, weakening them and compromising safety. MIG brazing, however, operates at a lower temperature, so you can attach panels without compromising the strength of underlying metals.
It’s a non-fusion process, attaching panels using capillary action rather than melting the base material. That makes it ideal for bonding outer mild steel panels to UHSS reinforcements without degrading their properties.
How MIG Brazing Works
Unlike fusion welding, most MIG brazing applications use a commonly recommended copper silicon (CuSi3) electrode wire that melts and flows over the base metals without fusing them. Through capillary action, the filler material adheres to both surfaces and to itself, forming a strong joint without the use of excessive heat. Note that vehicle makers may specify a different brazing electrode alloy in service information.
This lower heat input (approximately 1,650 to 1,750 degrees Fahrenheit compared to over 2,500 degrees Fahrenheit for MIG welding) means:
- Minimal burn-off of zinc coatings
- Lower risk of metal distortion
- Preservation of UHSS molecular structure.
However, because the filler doesn’t fully penetrate the base metal, proper surface prep is critical when performing MIG brazing during a repair. Any contaminants — like paint, rust or grease — can disrupt the flow of molten bronze and compromise joint integrity. Some vehicle makers recommend not removing any zinc coatings to preserve corrosion resistance on MIG-brazed joints.
MIG Brazing vs. MIG Welding
While both MIG brazing and MIG welding use similar equipment, the key differences lie in:
- Heat: MIG brazing uses lower temperatures.
- Process: MIG brazing is a non-fusion joining technique, not a true weld.
- Application: MIG brazing is often used where heat sensitivity or corrosion resistance is a concern.
Technicians who are proficient at MIG welding must adjust their technique slightly when MIG brazing. That includes:
- Using a push technique instead of a pull technique
- Longer electrode stick-out
- Lower voltage and wire feed speeds
- Accepting that the bead will appear more rounded or convex, which is normal and shouldn’t be flattened by increasing heat.
If you increase the heat to make the bead look flatter, you’re defeating the entire purpose of using MIG brazing.
Equipment Considerations
MIG brazing of an open butt joint can be performed with many standard MIG welders, but there are specific setup requirements:
- Wire: Copper silicon or copper aluminum alloy electrode wire (usually 0.8 millimeters)
- Liner: Teflon or plastic (to prevent wire deformation)
- Contact tip: Sized to the wire
- A four-roller system that allows even pushing of the wire to help prevent birdnesting
- Gas: 100% argon (not a 75/25 mix).
A MIG braze (left) vs. MAG weld.
For plug or slot brazes, a synergic pulse gas metal arc welding (GMAW) machine is required. These machines allow for precise control over the heat input and improve capillary flow between panels with recommended minimal gaps between panels.
Multiple torch machines allow technicians to toggle between MIG and MAG welding and MIG brazing — and multiple wire sizes or types — with minimal downtime.
OEM Recommendations and Use Cases
European automakers more often recommend MIG brazing in structural repairs. Jaguar Land Rover, for instance, frequently specifies the use of MIG brazing in structural areas such as:
- A-pillar and B-pillar reinforcements on the Range Rover Evoque
- Land Rover Discovery Sport structural components.
Honda and Acura vehicles are another example, with MIG brazing specified for repair procedures involving the UHSS outside stiffener ring replacement
You’ll often see MIG brazing specified for attaching mild steel to UHSS. Don’t ever assume the repair procedure will use the same attachment method that was used at the factory, as you may be instructed to use MIG brazing in the repair. That’s why it’s essential to always consult OEM repair procedures — not just rely on how a vehicle was originally assembled. It’s also important to check the procedures each time because they’re often updated.
Training, Testing and Practice
MIG brazing may feel familiar to experienced welders, but it requires deliberate practice to master.
Technicians preparing for procedures or training should:
- Practice on scrap material from the same vehicle or similar substrate.
- Match welding position to the real-world application (flat, vertical, overhead).
- Conduct destructive testing, such as peel tests, to verify capillary flow and joint strength.
A successful destructive test for MIG brazing, where bronze adhered to the UHSS steel with a clean tear from the mild steel.
A common peel test involves MIG brazing mild steel to UHSS, clamping the steel in a vice and peeling the mild steel away with locking pliers. A successful test shows bronze adhered to the UHSS with a clean tear from the mild steel.
Technicians should be in the habit of documenting preferred machine settings for different materials and gauges to reduce setup time and improve consistency.
Filling the Skills Gap
Automakers continue to recognize the benefits of MIG brazing and are adopting it as either an alternative or a required joining method in certain procedures.
Non-structural technicians can take the initiative to learn and practice not only to boost their confidence but also improve shop versatility and open up higher-earning opportunities when advancing to a structural role.
Technicians interested in learning how to MIG braze can get started by:
- Taking online I-CAR courses related to brazing and attachment methods
- Practicing with shop scrap metal
- Working with mentors in the shop to develop best practices.
Complete, Safe and Quality Repairs
Ultimately, MIG brazing is a method that ensures structural integrity, corrosion resistance and OEM compliance. Ignoring this technique — or performing it incorrectly — can result in weakened joints, liability risks and failure to meet manufacturers’ standards.
If you’re serious about being in this business, you need to be serious about mastering every type of attachment method, including MIG brazing.
Knowledge, as they say, is king. And when it comes to MIG brazing, applying that knowledge can make all the difference in delivering complete, safe and quality repairs — every time.
I-CAR’s Repairability Technical Support (RTS) portal is a valuable resource for collision repair professionals, offering access to OEM procedures, position statements and technical guidance organized by vehicle makers. For example, the article you can find on RTS, “Who Requires or Recommends MIG Brazing?” provides insight into which automakers specify MIG brazing as part of their repair procedures. Visit RTS.I-CAR.com for quick access to additional helpful articles and resources.
Also, check out these I-CAR courses related to MIG brazing:
- Introduction to MIG Brazing
- MIG Brazing Hands-On Skills Development
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