Melting or Bonding: What You Need to Know About Welding vs. Soldering

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Frank Wilson

Frank Wilson

Senior Editor

Whether you’re just starting as a hobbyist or are interested in learning how to weld or solder for a living, you may wonder what the differences are between them. While both are used for joining metal parts, there are several important distinctions.

Welding involves melting both metals to join them, while soldering requires melting a connecting metal called a filler. However, that’s not the extent of the differences between these two processes. If you understand what each method is used for, you’ll be able to determine which fabrication process is right for your project or career.

Last Updated on March 23, 2021

Welding vs. Soldering

Welding vs. soldering is a complex topic, as both fabrication processes involve heat and often a molten metal to join metal workpieces. There are numerous differences between the two fabrication processes, however. In welding, you join two metals by melting them, often using a filler material.

If you weld them together correctly, the weld should be as strong as the metal parts individually. However, if you don’t, you may alter the joint’s mechanical properties, causing a weak bond. One of the most critical variables is temperature. When welding metals, the temperatures involved may exceed 6,500°F.

Soldering requires a temperature of less than 840 °F — that’s lower than the melting point of aluminum. As a result, the metals you can solder are different from those you can weld.

In soldering, you use a filler material, known as solder, to join two metal parts. The solder melts and, once solidified, bonds to the two parts. You may also encounter soldering if you want to join electrical components — the solder acts as a conductive material rather than a bonding agent. 

Other Welding Differences

In welding vs. soldering, another critical difference is the strength as welding creates stronger joints. The workpiece doesn’t need to be heated before welding, and the metal requires heat treatment to boost its mechanical properties.

Soldering vs. Brazing

Soldering and brazing are similar because they rely on the melting of a filler material to fabricate metal parts. This contrasts with welding, which causes fusion by directly melting the base metal, alone or in combination with a filler. The key difference between brazing and soldering is temperature. Brazing occurs at a higher temperature, and brazed joints are stronger than those that have been soldered. 

Brazing and soldering also use capillary action to cause the liquid filler metal to flow into the gap between the two parts.

Contamination

When welding, it’s crucial that you avoid contaminants. Anything that isn’t the workpiece or the filler material is a potential contaminant. These range from organic materials to atmospherics. Simply put, if foreign material or gases are introduced to the weld, it could interfere with the part’s chemical makeup and mechanical properties.

Cleaning the workpiece may require special cleaning chemicals, distilled water, and a lint-free cloth or polishing until there’s no residue remaining. 

However, prevention is always the best remedy, and if you can clean parts and ensure they are neatly packaged or stored before welding, that’s the best way to avoid contamination.

Safety Precautions

Whether welding, soldering, or brazing, you need to wear protective equipment and proper clothing and take necessary precautions to minimize injury risk. You’ll be working with hot materials, some of which are toxic, so safety is paramount.  

Long-sleeved tops and pants and closed-toe shoes or boots are essential. However, you should also wear goggles or safety glasses and face shields when soldering. Soldering and brazing material can splash, and lead soldering is highly toxic. 

Welding poses unique risks because the temperatures involved are even higher, and metal melt. Fire-resistant clothing, dedicated welding gloves, and a helmet with a shaded lens are necessary for protecting your eyes from intense ultraviolet radiation. 

Welding produces infrared (IR) and ultraviolet (UV) radiation. While you can feel the former as heat, which can damage your eyes, the latter is more subtle. You can’t feel the damage caused by UV radiation, but it can cause a condition known as “welder’s flash.” To protect your eyes, it is vital to wear proper eye protection when engaging in this activity.

Different Types of Welding

Some of the most common types of welding include:

MIG

Metal inert gas (MIG) welding, also known as gas metal arc welding, uses a consumable wire electrode that a machine feeds from a spool. One of the easiest types of welding to learn, MIG allows you to weld a variety of thin and thick materials and is relatively clean.

TIG

Tungsten inert gas (TIG) welding, also known as gas tungsten arc welding (GTAW), is a type of arc welding that uses a non-consumable tungsten electrode. To protect the weld from atmospheric contamination, you use a separate shielding gas, such as argon. TIG welding is known for being clean but slow.

Stick

Also known as shielded metal arc welding (SMAW), this type relies on a consumable electrode that gradually melts, forming a weld pool that joins the metal parts. 

As the flux coating on the electrode is destroyed, it produces a shielding gas that protects against atmospheric contaminants. The electrode, which you use to create the arc, is also the filler material you use to fuse the metal pieces. Since they’re the same, the electrode, being consumable, melts. 

Oxyacetylene

Oxyacetylene welding, also known as oxy-fuel welding, combines pure oxygen with a fuel gas to melt metal. This is one of the oldest forms of welding and doesn’t require electrical current.

Different Types of Soldering

While there are many types of solder, there are, broadly, three categories:

Lead-based solder

Lead-based, or soft solder, consists of lead and tin—the more tin, the greater the soldering material’s strength. Lead is included to slow the solidification process and to reduce the incidence of tin whiskers.

Lead-free solder

As the health hazards associated with lead became more widely known and understood, there has been a growing movement to eliminate lead from solder. Following the EU ban on lead in consumer electronics, the demand for lead-free solder has increased. To avoid tin whiskers, other processes, such as annealing, may be used.

The number of alloying elements used in soldering materials varies considerably and includes everything from antimony and bismuth to nickel and silver, all with their own unique properties.

Final Thoughts

Regardless of which fabrication process you determine is right for your project or career prospects, it’s essential to understand some of the key differences from heat to materials. Whichever process you use for your projects, ensure that you safely engage in the activity by wearing appropriate protective gear and cleaning and maintaining your tools.