Brazing, Soldering, and Welding

Their Differences, Applications, and IAQ Risks

The pots and pans you use for cooking, the frame of your favorite chair, and the circuit board that powers your cell phone. All of these are examples of objects made, in part, by thermal joining. But brazing, soldering, and welding – the methods used for joining metal parts – can do so much more. In fact, the bonding of metals is indispensable for large-scale infrastructure such as bridge construction, railroad tracks, and even assemblies used in outer space.  While strong, durable connections are crucial, the air quality problems associated with heating metal are not and therefore should be eliminated for the safety of the people who work in these trades.

Methods Defined

Brazing, soldering, and welding are all metal joining methods that use heat to permanently bond metal parts. The differences are in the temperatures, metals used, and the objects that require thermal joining.

Brazing is a liquid-solid phase bonding process whereby a joint filler metal is melted (the liquid), and the base material (the solid) is not. High-intensity heat sources, such as industrial furnaces, induction coils, or gas torches, insert filler metals into joints, thus bonding dissimilar metals. Fusion occurs at temperatures above 840° Fahrenheit.

Soldering is also a liquid-solid bonding process and, like brazing, does not join the base materials. Soldering utilizes lower-temperature heat sources like small propane torches, hot air guns, and soldering irons to join dissimilar metals and occurs at temperatures below 840° degrees.

Welding involves melting two or more like-kind metal parts together using heat and pressure. As the metal cools, bonding occurs. Welding heat sources include electricity, gas flames, and mechanical friction. Permanent bonding takes place at temperatures between 6000 – 10,000°.

Materials Used

Choosing which thermal joining process to employ will depend on the materials that require bonding, the desired outcomes, and the application. Examples of each method and the materials and applications for which they are best suited:

Brazing is best for joining dissimilar metal pieces, such as cast iron, bronze, and brass metals that require withstanding high pressure, regular use, and longevity. Fabrication of HVAC parts, hand tools, and gas piping are examples of applications where brazing is best.

Soldering works well for gold, silver, and copper when a lower joining heat is required. Soldering is ideal for electrical wires and jewelry, circuit boards, dental appliances, and delicate decorative metalwork.

Welding guarantees the highest structural strength and is the most reliable choice for fusing stainless steel, titanium, and aluminum used for auto fabrication, shipbuilding, and furniture production.

IAQ Concerns

The burning of metal – as well as thermoplastics, glass, and ceramics – that takes place during thermal joining emits a variety of contaminants that negatively impact indoor air quality (IAQ). Toxic gases and vapors, metal fumes, and fine particulate matter are all released into the atmosphere and, if not controlled, can be inhaled by workers. This occupational risk can result in short-term respiratory problems, long-term illnesses, some of which can result in death. The negative health impacts of thermal joining emissions cannot be overstated.

Control Measures

The removal of indoor air pollution is a multi-step process. Proper equipment maintenance, in addition to the use of air quality monitors and ensuring proper ventilation, are all vital. But the most effective way to guarantee that thermal joining pollutants do not enter the workplace is by using air cleaning equipment to remove pollutants at their source, before they can create a hazardous indoor environment.

At AIR Systems, Inc, our Extract-All® line of air cleaning products eliminates pollution at the source. Offering a full line of ambient and central systems, we recommend our portable fume extractors as they are specifically designed for brazing, soldering, and welding applications.

To safeguard your workplace and ensure your IAQ is healthy for all employees, contact an AIRSInc specialist today for a free indoor air quality assessment.