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Is There A Difference Between Welding And Soldering?

Posted by Kaempf & Harris on February 28, 2018

Like many sheet metal terms, soldering and welding are used interchangeably. However, while these two operations are similar, their process and sub-techniques are different.

The main difference between welding and soldering is melting. In soldering, metal fabricators heat the metal to be bonded but never melt them. In welding, metal fabricators melt the base metal.

Soldering is most similar to brazing because it uses capillary action to flow the metal into the joint until it cools and hardens. For more information about brazing, click here.

To learn more about the difference between soldering and welding from Kaempf & Harris, read on:

The Big Difference

Kaempf & Harris has created an easy outline with the help of ME Mechanical, a newer online resource for mechanical engineers and engineering students, to explain the key differences between soldering and welding:

  • Welding joints are the strongest, followed by soldered joints then brazed joints.
  • Welding requires about 6,500 degrees Fahrenheit, while soldering requires about 840 degrees Fahrenheit.
  • Workpieces and the metal base are heated and melted in welding. Soldering requires no heating of the workpieces.
  • According to ME Mechanical, “Mechanical properties of base metal may change at the joint due to heating and cooling” during a weld. In soldering, mechanical properties don’t change at all.
  • Skill requirements for a welder are typically higher than a solderer. However, the heat cost is about the same.
  • Heat treatments are always required for a weld, whereas soldering doesn’t ever require heat treatments.
  • Welding requires no preheating of the workpiece. However, soldering requires preheating for a high quality joint.

The Process

According to Machine Design, “Soldering is a low-temperature analog to brazing.”

As defined by the American Welding Society, “soldering takes place with fillers (also known as solders) that melt at below 840 degrees Fahrenheit. Metals that can be soldered include gold, silver, copper, brass, and iron.”

Lead was the main metal for this sheet metal technique. However, environmental concerns are pushing the sheet metal industry to lead-free alternatives.

“The filler, called solder, melts. When it solidifies, it’s bonded to the metal parts and joins them. The bond isn’t as strong as a...welded one.”

Flux, a chemical cleaning and purifying agent, is used in soldering and welding to clean the metal surfaces. Flux eases solder in order to flow over the pieces to be joined.

“Soldering is also used to join electrical components,” according to Machine Design. “The joint is not necessarily strong or structural, but electrically connects the parts with conductive solder.”

In the welding process, fusion is caused. Fusion is the generic sheet metal fabrication term for joining together metals of similar compositions and melting points. A pool of molten material called the weld pool is formed due to the high melting points of the workpieces.

This pool cools to form a joint that’s stronger than the base metal, and pressure in the form of heat might be used to assist in weld production.

Welding also requires a form of shield to protect the filler metal from being contaminated or oxidized, which is the loss of electrons and causes iron oxide (better known as rust) to form on the metal.

The Techniques

Types of soldering include the following:

  • Brazing
  • Hard or silver soldering
  • Soft soldering

Types of welding include the following:

  • Electric resistance welding
  • Electroslag welding
  • Flux-cored arc welding
  • Gas metal arc welding
  • Gas tungsten arc welding
  • Glass welding
  • Oxy-fuel welding
  • Plastic welding
  • Shielded metal arc welding
  • Submerged arc welding

If you want to learn more about welding, click on the button below to download Kaempf & Harris’ Cheat Sheet To Welding Terms:

Topics: welding, sheet metal fabrication, Techniques

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