If you’ve spent any time working on cars, you’re probably familiar with the concept of welding. It is often the go-to process when two pieces of metal need to be joined. But what about brazing? Isn’t it essentially the same thing? While both processes create a strong metal-to-metal bond, the principles behind brazing and welding differ significantly. We’ll explore these differences and clarify when you might choose one technique over the other in your DIY automotive projects.
What Is Welding?
Welding is the process of permanently joining metal pieces together by melting and fusing them under controlled heat conditions. The high temperature used in welding — whether it’s MIG, TIG, or stick welding — causes the edges of the base metals to liquefy and fuse once they cool. When done properly, a weld can be as strong, or even stronger, than the original pieces of metal.
The major drawback of welding is the very high heat involved, which can lead to warping or distortion, especially in thinner sheet metal. It also requires skill to achieve clean, strong welds. Poor welding technique can cause cracks, incomplete fusion, or excessive penetration.
Common automotive uses of welding include:
- Chassis and frame repairs – When patching or reinforcing structural components, welding is preferred for its high strength.
- Body panel work – MIG welding is often used to attach replacement panels or fill rust holes.
- Exhaust and tubing fabrication – Welding allows you to custom-fit pipes, ensuring a solid seal and long-lasting performance.
What Is Brazing?
Brazing also joins metals, but unlike welding, the base metals are not melted. Instead, a filler material is heated with a gas torch until it liquefies and flows into the joint. This is often a rod or wire composed of an alloy with a lower melting point than the base metals. Capillary action pulls this molten filler through the narrow gap between the two pieces being joined. Once it cools, the filler solidifies and bonds the parts together.
Because you don’t heat the base metals to their melting point, brazing occurs at a lower temperature than welding. As a result, there’s typically less distortion. This makes it ideal for joining thin-walled tubing or other delicate parts.
While most body and frame repairs call for welding, brazing has its place in the automotive world. You’ll often find brazed joints in:
- Radiators and heater cores – The thin tubes and fins in these heat exchangers benefit from the lower temperatures and capillary action that brazing provides.
- Air conditioning components -Condensers, evaporators, and lines frequently use brazed joints because they demand leak-free connections without risking damage to thin-walled aluminum or other alloy parts.
- Fuel and brake lines – In certain cases, brazed fittings can be used for low-pressure fluid lines. However, most modern systems rely on specialized connectors or welded fixtures.
- Small brackets and sensor housings – Brazing can join small parts with minimal heat damage, preserving sensitive components.
Key Differences Between Welding and Brazing
- Temperature – Welding requires high heat, often exceeding the melting point of steel (around 2,500°F). Brazing requires lower heat (typically between 800°F and 1,500°F), adequate to melt the filler but not the base metal.
- Joint Strength – Welding fuses the base metals for high tensile strength. Brazing relies on a metallurgical bond formed by the filler metal. Brazed joints can be very strong, but typically won’t match the sheer strength of a well-executed weld.
- Distortion and Heat-Affected Zone – Welding’s higher heat requirement can warp sheet metal and introduce residual stresses. Brazing uses lower heat that reduces the risk of warping, making it excellent for precise or thin applications.
- Suitable Metals – Welding requires matching filler rods and processes for different metals (steel, stainless, aluminum, etc.) Brazing is very effective for joining dissimilar metals (like steel to copper) and for metals with different thicknesses.
For the DIY enthusiast, knowing the differences between welding and brazing can expand your repertoire of metal-joining options. Welding offers raw strength and is often essential for structural or high-stress repairs. Brazing, on the other hand, shines when you need to join thinner, dissimilar, or more delicate metal parts without the risk of excessive heat damage. By understanding which method is best suited for each task, you’ll be well-prepared to tackle a wide range of projects.
looks like we’re all having fun with this!
Steve
you are 100% correct. MIG tacking is the way to go for autobody sheet metal. Fitzee’s Fabrication on YouTube is a great channel.
when I was a kid, we used gas and brass in the body shop. we had damp rags or a commercial heat-absorbing putty surrounding each tack to sink the heat and prevent warping.
Which brings up another tip: 50% of “good welding” is predicting/controlling/preventing the secondary effects of heat.
FYI, here’s a little blurb I wrote for folks unfamiliar with gas welding:
https://www.reddit.com/r/E30/s/G5UxlxD54d
Thanks for the additional insight on this, Paul.
A difference worth noting is that brazing is typically done with a gas torch, while most modern welding is done using an electric arc, whether it be stick, MIG or TIG technology. It takes time to bring a joint up to brazing temperature with a torch and during that time the base metal is absorbing the heat, so brazing can warp thin sheet, or result in metallurgical change in the base metal some distance from the joint. Electric welding is at temperature almost instantaneously, so the time for ‘heat soak’ to take place is much shorter. A common technique when joining thin materials with electric welding is to weld in very short spurts, allowing the weld to cool before hitting it again as a technique to control the heat and reduce the risk of burn through. Bicycle frames made with thin-wall, alloy steel tubing are almost always TIG welded instead of brazed, as TIG welding is faster which decreases production time and speeds the welding process, reducing heat soak. Reduced warping is also a major reason why MIG or TIG are preferred over torch brazing for sheet metal body panel repairs.
welding is joining 2 identical metals by heating to their melting point. spot welding implies no filler metal. otherwise, a filler rod of the same metal is used to “fill the gap..
brazing can join 2 identical metals as well. as noted., the brazing rod melts above 840F, but much below the base metals. joints are typically 20-50% the tensile strength of a welded joint. often used with cast iron repair.
brazing is the only metallic joining of 2 different metals, such as copper to brass. the filling rod is chosen based on metals, strength, cost, temp.
Soldering looks like brazing, but the filler melts below 840F and is weak, so a large contact area is needed…think male-female copper pipe joints. note that plumbing Solder melts around 350, but is very weak by 250; hence not used for HVAC. Here’s where people get sloppy…silver brazing rod…melting around 1000 and quite high tensile strength…is called “silver solder”, and is commonly used in HVAC.
if you plan to put an air-to-air heat exchanger on the output of your air compressor, note that discharge Temps are around 300, so silver brazing would be needed for non-threaded connections.
if this sounds interesting, try your local community college trade school night classes. one semester of any 1 type of welding is $85 where I live.
Very informative. I’ve been a welder for over 50 years, always good to hear information that is new and useful. Some of it that has been forgotten. Some of it new. Please keep it coming. Thanks 👍