A Simple Explanation of Welding

Welding is probably the best know method of joining significant bodies of metal together.

Soldering is also a well-known method of joining metals, but the “joint” (join point) is weaker because the metals being joined don’t actually melt, making it more applicable in electronics and fine art or jewelry-making than structural work. It’s not infrequent that we use silver soldering in some of our projects around the shop. Brazing and Riveting are the other two forms of metal joining with brazing being similar to soldering (in that the work pieces aren’t melted) and riveting is done by drilling holes in the work pieces through which bolts are passed onto which permanent heads are created on either side.

English_-_Gun_Shield_-_Walters_511414Joined metals are at the foundation of modern civilization and here in Pensacola, on the Gulf Coast, and nationwide – if not worldwide – skilled welders of various specialties are numerous.  We wanted to add a simple explanation of the different types of welding for our friends and customers who are interested in learning, want further clarification or would like a reference resource. We want our clients to have as much of an understanding of the processes and methods we use so that the quality of our work and our attention to detail won’t go unappreciated (or unshared).

As far as the broad categories of welding go, Arc Welding and Gas Welding are the processes most common in small to medium sized metalwork or welding shops like Renaissance Man (as opposed to Energy Beam, Solid State or Resistance welding which are more likely to be found in large commercial production facilities).

Arc Welding is the process in which a power source is applied to an electrode, creating an electrical current which arcs through the air, connecting with a base material located at the weld point, exciting the molecules of the work metal to be joined to the point at which the molecules between the distinct pieces of metal become merged.

Gas Welding simply uses heat from a gas flame to excite the molecules of the work metals into a joinable temperature. Gas Welding is less popular – especially in industrial applications – than it was in the past, and the join points are less durable than with other weld methods, but the methods, tools and materials are relatively attainable and it remains a popular and sensible approach to pipes, tubes and repair work.

Common Methods of Gas Welding

Oxy-Acetylene Welding

The most common gas welding technique in which a blend of oxygen and acetylene gas are feed into the welding torch and ignited, creating the highest flame temperature from gas fuels. As fuel gasses go, acetylene is expensive and an unstable gas, requiring specific handling and storage procedures.

Oxy-Gasoline Welding

In cases where fabrication is cost-limited, pressurized gasoline can be used to fuel welding torches, particularly in situations where acetylene canisters cannot be obtained. Particularly in developing countries and poor areas, a common practice among jewelry-makers is to weld using a torch fueled by hand-pumped gasoline.

MAPP Gas Welding

Methylacetylene-propadiene-petroleum (MAPP) is more inert than many of the other other gas mixtures, making it safer and more popular with hobbyists and recreational welders (who also need to consider the issue of storing the materials). MAPP can also be used at very high pressures, allowing it to be used in high-volume cutting operations.

Butane/Propane Welding

Butane and propane are heavier gases which can be combined or used individually. They, like MAPP, are less expensive than acetylene and easier to transport, but have a lower flame temperature. Propane torches are more frequently used for soldering, bending and heating.

Hydrogen Welding

Hydrogen can be used at higher pressures than other fuel gases, making it especially practical and common in underwater welding. There is also hydrogen welding equipment that works by splitting water into hydrogen and oxygen (through electrolysis) as the fuels sources to be used in the welding process. This type of electrolysis is often used with small torches, such as those used for jewelry making.

Common Methods of Arc Welding

Electroslag Welding

Electroslag welding came into practice in the mid-1950s. It’s a fast welding process employed to join large materials such as thick steel plates. The plates or materials are usually arranged in a vertical position, as the Electroslag weld is designed to weld at this angle without causing distortion to the welder. The name ‘Electroslag’ was derived from the use of water filled copper areas within the device, which were included and designed solely to prevent melted ‘slag’ from pouring into other areas as it liquefied.

Flux-Cored Welding

Flux-cored (“flux-core”) welding was created and put into use in the early years of the 1950’s. Its purpose was to give another option to the popular use of ‘stick welding’. The Flux-Core process is mostly used for projects that require fast speed as it is an automatic form of welding. Many construction workers use this process on the job because of the speed and the ability to use flux-core welding in multiple situations on various materials. Flux-core and stick welding are our go-to methods for many outdoor projects, as wind can be a factor. Being in Pensacola, right on the gulf coast, a lot of our railings end up being on waterfront balconies. And yes, it gets breezy.

Gas Metal Arc Welding

The process of Gas Metal Arc Welding (GMAW), created in the 1940’s, is another automatic welding process. This method consists of the use of a welding gun which automatically feeds the weld metal through the gun for use. The weld gun also automatically distributes a protective gas as a shield from the natural elements. This process saves a lot of time and is best for a large quantity of welding work. It was originally developed for use with aluminum metals. Today, this method is mostly used by those welders in the automobile repair and manufacturing industries.

Gas Tungsten-Arc Welding

Gas Tungsten-Arc Welding is considered to be one of the most difficult and time consuming of welding processes used today (along with Plasma Arc Welding). This is because it requires a great amount of focus and skill due to the small area of space between the ’arc’ of the flame and the material being welded. Usually, small strips of metal that do not contain much iron are welded with this process. Though it is difficult, it produces extremely strong high quality welds when done correctly. Welders manufacturing bicycles and aircraft, both commercial and military, use Gas Tungsten-Arc Welding often while many other welders will never come across this process. Very little change has been made to this process since its release back in 1941.

MIG (Metal Inert Gas) Welding

GMAW.welding.af.ncsThe primary form of welding we use in the shop, Metal Inert Gas Welding is a process of welding that uses a gas to shield the weld metal. The gas keeps the metal being welded from being effected from natural elements in the environment, such as oxygen. This allows the welder to operate at a continuous rate, making the process fairly quick. Operation of the equipment does not require an extreme level of skill by welders, however, the equipment used in MIG Welding can only be used indoors due to the gas involved in the welding process. MIG Welding was originally released in the 1940’s but underwent many upgrades until being perfected in the 1960’s.

Plasma Arc Welding

Plasma Welding is very much like that of Gas Tungsten-Arc Welding (GTAW). The two processes are often compared because they basically work in the same fashion, only using a different type of torch. This method was developed in 1954, though even today, it is still being improved upon. Plasma Welding also requires more concentration than GTAW because of the smaller arc and precision of the weld. In Plasma Welding, the electrical current is passed through an extremely small nozzle which passes through the protective gases, enabling extreme accuracy when welding small areas. Plasma Welding can heat metals to very extreme temperatures which can result in deeper welds. Like GTAW, this welding process is generally used in the aircraft manufacturing industry.

Shielded-Metal Arc Welding

Shielded-Metal Arc Welding (SMAW) is also referred to as ‘stick welding’. This process is known to be the most popular and widely used processes in welding today. The first form of SMAW was created in 1938 but the process and equipment continues to undergo upgrades. It is a manual welding process that is very simple and inexpensive to operate. The results often are not as ‘neat’ as other methods and molten splatter is a common occurrence. Stick welding is mostly used by construction welders working on steel structures and other industries that require welding but do not have large budgets.

Submerged Arc Welding

The Submerged Arc Welding process can only be used properly on materials containing high iron contents, such as stainless steel. The device used in this process can be automatic or semi-automatic making it a fairly fast welding process. While it is a fast process, the electrical arc must constantly be covered by ‘flux’ in order to protect the metal from the atmosphere during the welding process. This cover also prevents any welding spatter which makes it safer for welders than some of the other forms of welding. The process is named after this need to be ‘submerged’ in a flux cover.

TIG (Tungsten Inert Gas) Welding

Tungsten Inert Gas welding is much like the process of Metal Inert Gas (MIG) welding. The main difference between these two forms of welding is that TIG uses a tungsten current form, while MIG uses a metal electrode. Because TIG uses tungsten, it requires an additional filler placed inside the welding device as tungsten does not melt in the welding process. Tungsten is unique as it can be heated to a higher temperature before melting than all other metals. Tungsten Inert Gas Welding is usually used in industries that work with stainless steel. We use TIG welding a good bit around the Renaissance Man shop.

Resources:

http://en.wikipedia.org/wiki/Metalworking
http://en.wikipedia.org/wiki/Welding
http://en.wikipedia.org/wiki/Electrolysis
http://www.gowelding.org/articles/types-welding

 

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