There are many different welding processes and wires and it can be difficult to choose which will best suit your application.
Let’s examine the differences between the GMAW solid wire and FCAW flux cored wire welding processes. These processes are very popular and have some similarities, but also some very big differences. To determine which process to use, it is necessary to check some important variables. Some of the variables would be: thickness of the material to be welded, shielding gas, wire feed speed, welding current, work location and appearance of the weld. There is no single solution for all cases and all the variables listed above will affect the decision to be made to use solid or tubular wire.
Arc welding with shielding gas and metal wire is identified by AWS as GMAW, and is also popularly known as MIG welding (Inert Gas and Metal Wire Welding) and uses a continuous solid wire as filler metal and a shielding gas. supplied by a high pressure cylinder. Carbon steel wire is usually coated with copper to protect it from oxidation, improve electrical conductivity, increase contact tip life, and improve arc performance. All other types of wire can also be applied using the GMAW process: stainless steels, nickel alloys, aluminum, etc.
The welder must set the machine to DC+ (direct current, positive polarity). Shielding gas is generally a mixture of argon and carbon dioxide or pure carbon dioxide. The purpose of the shielding gas is to protect the molten metal against reaction with atmospheric air. The shielding gas flows through the handle and gun and exits through the gun nozzle with the wire to protect the metal molten pool. Molten metal is very reactive with oxygen, nitrogen and hydrogen in the atmosphere.
MIG welding is generally preferably carried out indoors where there is protection from gusts of wind because a slight breeze can blow the arc shielding gas and cause porosity in the weld, so welding outdoors is generally avoided unless one has adequate protection against wind through protective screens.
Arc welding with cored wire identified by AWS as FCAW is different because it uses a wire that contains a flux in the core of the wire which, when burned by the arc temperature, produces protective gases and fluxes that help to produce a perfect weld. There are two types of tubular wires: gas shielded and self-shielded.
Gas shielded flux cored wires require a shielding gas for welding and the slag is easy to remove. The most commonly used shielding gases are very similar to those in the GMAW process, in which pure CO2 or a mixture of argon + CO2 can be used. The welding operator may decide to use a flux-cored wire with gas shielding when welding thick metals or in out-of-position applications. Gas shielded flux cored wires have a flux that solidifies faster than the molten weld metal, forming a shield that holds the weld pool in overhead and upward vertical welding. As in GMAW welding, gas shielded cored wire must be applied with DC+ (direct current, positive polarity).
Self-shielded cored wire does not require external shielding gas. The weld pool is protected by the gas generated when the wire flux is burned. A gun pull angle is specified to improve operator visibility. Self-shielded cored wire is different from gas-shielded wire because it must operate on direct current with negative polarity. Self-shielded cored wire is considered portable because it does not require an external shielding gas. The protective flow is very efficient and can withstand gusts of wind. Self-shielded cored wire is widely used in the construction industry where outdoor welding is very common. It is a perfect choice for this service because it is not necessary to transport a gas cylinder and protect the welding with suitable screens. This process is much more efficient than manual welding with coated electrode (SMAW) because it uses a wire feeder that makes this process semi-automatic. In agricultural applications, self-protected wire is of great help because quick repairs can be made to repair a broken machine in the middle of the field in quick time. A disadvantage of this process is that there is more slag than in the gas shielded process and it may be inconvenient to remove the slag and clean the weld.
In summary, there are many advantages and disadvantages to both the GMAW (MIG) process and the FCAW cored wire process. Some advantages of the GMAW process are that there is less splashing and no slag which saves time in slag removal and overall cleaning time. The appearance of the weld will be better due to the lower spatter level than cored wire. The arc is softer and less likely to burn through thin gauge material.
The GMAW process is the easiest type of welding to learn and tends to be more forgiving if the operator has any difficulty maintaining the correct arc length or maintaining a constant welding speed. If the operator has sufficient skill and has suitable welding guns, shielding gas, guide tubes, feed rollers and the appropriate wire, the GMAW process can weld a wide variety of materials, including thin materials and different types of materials such as stainless steels, nickel alloys or aluminum.
Some disadvantages of the GMAW process are that it requires an external shielding gas which is not cheap. In most cases you must rent or lease a cylinder from a gas supplier and pay the cost of refilling the cylinder. When using shielding gas, additional equipment is also required, such as hoses, regulators, solenoid valves on the wire feeder and gas flow meter. The GMAW process is not the most practical choice for a quick repair at no additional cost when portability and convenience are desired. The GMAW process can be used for out-of-position welding but is much slower than cored wire because it is generally limited to short circuit transfer, which is restricted by many welding codes due to its tendency to produce lack of fusion. It also requires that the steel being welded is very clean.
Some advantages of self-shielded wire are the fact that it is great for welding outdoors since the flux inside the tubular wire offers efficient protection even in gusty wind conditions. An external shielding gas and additional equipment are not required, so it is much cheaper and quicker to start welding. This process is more suitable for applications with thick materials. Some advantages of gas shielded cored wire are that the slag solidifies very quickly which helps to increase deposition rates especially in the upward vertical position. One of the disadvantages of the cored wire process is cleanup. With the self-protected tubular wire with all the protection provided by the internal flow of the wire, the slag can be very difficult to remove and clean. This can be a very big job producing higher costs.
To conclude, you cannot be shortsighted and think that one process solves all problems. Many factors determine which process should be used. Some variables mentioned in this article will help determine the choice of process such as material thickness, shielding gas, wire feed speed, voltage settings, location where the work is being carried out and the appearance of the weld. Both GMAW welding with solid wires and FCAW welding with tubular wires have their advantages and disadvantages, so it is very important to know what will work best for your needs.
