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Soldering vs Brazing vs Welding: What's the difference?

Date: 07-06-2021
Weldclass Academy

Soldering vs Brazing vs Welding

 

A simple and straight-forward explanation of the basic differences between the Soldering, Brazing and Welding processes for joining metals.

 

Terms

Often, these terms are used very loosely (especially soldering and brazing), and there can be a lot of similarities between these processes, which can make it difficult to define which process is which.  Here's our quick definitions;

Soldering: Joining of metals via capillary2 process, using filler metals (solder) with lower melting temperatures of around 500oc or less, using a soldering irons and/or flame torches.

Brazing: Joining of metals via capillary2 process, using filler metals (brazing rod/alloy) with higher melting temperatures of up to 900oc, using flame torches.

Welding: Joining of metal via fusion3 (melting the parent metal), using oxy-fuel flame torch or arc welding torch. While this applies to all type of arc welding (including Stick & MIG), in this article we focus on TIG welding as this is similiar to brazing or oxy welding, where a filler metal rod is used. 

For information on the which type of brazing or filler metal rod to use for joining different metals, download this filler and brazing rod guide.

 

Summary Table

This table compares the essential differences between soldering, brazing and welding processes.  

 

Soldering

Brazing

Oxy Welding

TIG Welding

Method

 LPG or Butane, or Soldering Iron LPG, Butane or Oxy-Fuel1 

Oxy-Acetylene1

TIG

Flame or Arc Temp

 ≤1,400oc 1,400-3,000oc

≥3,000oc

≥5,000oc

Filler Metal Melting Temp

≤500oc

≤900oc

≤1,500oc

Parent Metal Melted?

No

Yes

Action

Capillary2

 Fusion3

Shielding  / Cleaning

 Flux4 Flame / Flux5 Gas6

Filler Metal Used?

 Yes Mostly7


Comments:

1.  Suitable Oxy-Fuel processes:
Oxy Welding is only possible with Oxy-Acetylene (not Oxy-LPG). This is becuase an Oxy-Acetylene flame completely consumes all the oxygen in the welding zone, preventing oxidisation - whereas an Oxy-LPG flame does not. 
Oxy Brazing can be done with either Oxy-Acetylene or Oxy-LPG. Since brazing relies on flux for shielding, rather than the flame.

2. Capillary action is the ability of a liquid (in this case the molten filler metal) to flow in narrow (or even microscopic) spaces without the assistance of - or in opposition to - external forces like gravity. In very simple terms, soldering or brazing is "sticking" pieces of metal together, which is made possible due to capillary action. 

3. Fusion involves melting the parent metal, to weld (or "alloy") it together with the filler metal

4. Flux agents can be applied seperately (such as a flux fluid or paste), or can be present in/on the brazing rod/wire itself (for example: resin-core solder or flux-coated brazing rods).

5. As per point 1 above, an Oxy-Acetylene flame will consume all oxygen surrounding the weld, thereby shielding it from oxidisation.  Oxy welding of mild steel does not require a flux for shielding purposes, however it can be beneficial to use a flux or cleaning agent to remove impurities. Oxy welding of stainless-steel or aluminium usually do require a flux. 

6. Gas used for TIG welding is typically argon gas, or an argon based mixed gas

7. TIG welding mostly involves the use of filler metal (often referred to as 'TIG rod'). In some applications when welding thinner materials with close fit-up, filler metal may not be required.

 

Related Info & Products: 

Weldclass filler and brazing rod selection guide

Weldclass brazing rods range, including silver and bronze brazing alloys

Weldclass filler wire range, including wires for TIG & Oxy welding of steel, stainless-steel & aluminium

Oxy Equipment ID Guide to view the complete range of torches & equipment for Oxy brazing, welding and cutting.

More articles on Gas & Oxy Equipment

 

 

Brazing & Filler Rod Selection Chart

 

 

 

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Gas & Oxy Equipment