Brazing vs. Welding: Which Joining Process Should You Use?

A copper refrigerant line meeting a brass valve, or a thin-wall tube joined to a thicker fitting: these are the moments where the choice between brazing and welding gets decided on the shop floor, not in a textbook. The mechanical difference is precise. Brazing melts only the filler alloy above 840°F and pulls it into the joint by capillary action, while welding, the process covered in an Introduction to Welding, melts the base metals themselves and fuses them at the interface.

That single distinction drives everything downstream: joint strength in shear versus tension, distortion on thin sections, a central concern in TIG Welding, filler and flux selection, equipment cost, and whether a technique makes sense for HVAC copper, cast iron repair, aluminum assemblies, or aerospace hardware.

What Are Brazing and Welding, and How Do They Differ?

Brazing and welding both create permanent metal joints, but by different mechanisms: brazing relies on capillary action without melting the base metal, while welding fuses the base metals themselves at the joint.

What brazing actually does

Brazing joins metals with a filler metal that melts above 840°F but below the melting point of the base metals being joined. The molten filler is drawn into the tight gap between close-fitting parts by capillary action, then cools and solidifies to form a strong bond. The filler can be a different alloy from the base metals, which is why brazing is flexible for mixed-material assemblies. Because the base metal never melts, brazing can join dissimilar metals such as copper to steel or brass to stainless, and it preserves the original shape and properties of the parent parts.

What welding actually does

Welding goes further. It melts the edges or surfaces of the base metals at the joint, often adding a filler rod or wire that mixes with the molten pool. Filler material is optional in some processes, such as autogenous TIG welding, but the base metal always melts. When the pool solidifies, the parts become one continuous piece. This produces a joint that can approach or equal the strength of the base metal, but it demands compatible metallurgy and higher heat input. Most welding processes require the two sides to be similar in composition, or at least selected with compatible filler and procedure.

Where soldering fits

Soldering is the lower-temperature cousin. It uses a filler metal that melts below 840°F, typically with a soldering iron or torch, and relies on wetting rather than melting the base metals. The 840°F threshold is the common dividing line between soldering and brazing. Above that temperature, capillary-flow joining is called brazing; below it, the same physical idea is soldering.

Why the distinction matters

Choosing brazing over welding usually comes down to heat sensitivity, material mismatch, or joint design. Brazing lets you join thin sections, cast iron, aluminum, or dissimilar metals without warping or cracking them. Welding gives maximum joint strength for same-alloy structural work. Each has its place, but they are not interchangeable.

Brazing vs Welding vs Soldering: Temperature Spectrum at a Glance

The three processes are separated by one simple question: does the base metal melt? Soldering stays below 840°F, brazing crosses that threshold while keeping the base metal solid, and welding melts the base metal itself. The table below shows roughly where each process lands for aluminum, steel, and copper.

Temperature Thresholds and Heat Input: The 840°F Dividing Line

The number that separates brazing from soldering is 840 degrees Fahrenheit, or 450 degrees Celsius. Below that line, you're soldering. At or above it, you're brazing. Both processes join metal by melting a filler that flows into a fitted joint, but the base metal itself never reaches its melting point in either case. That single fact, the base metal staying solid, is what separates brazing and soldering from welding altogether.

Why the Threshold Matters

The 840°F mark isn't arbitrary. It roughly marks where filler alloys shift from soft, low-strength metals like tin-lead or tin-silver solders to harder, stronger alloys built around copper, silver, or nickel. Cross that line and you gain real mechanical strength suitable for pressure lines, structural brackets, and load-bearing assemblies, which is why HVAC refrigerant lines and plumbing joints often live right around this threshold depending on the job.

Heat Input Compared to Welding

MIG welding, like all welding, pushes both pieces of base metal past their melting point, often north of 2,000°F for steel, and fuses them directly. Brazing tops out in the 1,100 to 1,600°F range for most common filler metals, and that base metal stays fully solid throughout. Less total heat goes into the part. That translates into real energy savings on production runs and, more importantly, protects the microstructure of heat-sensitive alloys. Hardened tool steels, certain stainless grades, and thin-wall tubing can lose temper or develop brittle zones under welding heat, including TIG welding. Brazing sidesteps that risk entirely.

The Distortion Connection

Lower peak temperature also means less thermal expansion and contraction across the joint, which is the root cause of warping in welded assemblies. We'll cover distortion and joint strength in more detail shortly, but the short version is this: less heat in generally means less movement out.

Joint Strength: Are Brazed Joints Always Weaker Than Welds?

The strength of a brazed joint depends heavily on joint configuration, filler metal, clearance, and overlap. In lap shear, brazed joints can approach or exceed base-metal strength with sufficient overlap, while welded butt joints generally remain stronger in direct tension. The table below summarizes published values where available; missing cells reflect data that is not directly comparable across brazed and welded specimens.

Related Articles

Cost, Equipment, and Skill: One-Off Repairs vs Production

Oxyfuel brazing is the lower-cost entry point for one-off repairs, with small-shop startup around $300 to $800 compared with $800 to $1,500 for TIG and $400 to $1,000 for MIG depending on gas shielding. Training data also differ sharply: a dedicated oxy-fuel cutting course lists 60 lab hours, while the cited welding program lists 540 hours and a $3,999 annual cost. Comparable production-speed figures are not published in the current sources, so choose by joint size, material, and production volume rather than a single speed benchmark.