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Apr 5, 2018

Out-of-Position Welding: Selecting Filler Metals and Welding Processes


While it’s acknowledged in the welding industry that flat/horizontal, in-position welding is preferred, there are some applications where out-of-position welding is necessary. Vertical and overhead welding may be the only options in some applications, for example when welding a very large piece that cannot be moved or when the workpiece is fixed in place. 

Due to these factors, out-of-position welding is used in many industries, including shipbuilding, offshore, structural, pipeline, and in general fabrication where moving the piece isn’t practical. 

There are several keys to success when welding out of position, including choosing the right welding process and filler metals and using optimal parameters for the application.

Welder welding out of position on structural steel

Vertical and overhead welding are inherently more
difficult than flat/horizontal, in-position welding
because the welder must work against gravity. Choose
the right welding process and filler metals to help.

Key challenges and common mistakes 
Vertical and overhead welding are inherently more difficult than in-position welding because the welder must work against gravity — the liquid weld pool has a natural tendency to sag or drip, which makes it harder to produce quality welds.

The answer to this dilemma with most processes is to weld slower and with lower welding parameters or heat input, which reduces weld pool fluidity. However, doing so results in much lower productivity. 

Common mistakes made when welding out of position include:  

-Not using the optimal welding process for the application

-Not adjusting from in-position welding parameters, resulting in higher heat inputs than necessary

-Assuming the same techniques used for in-position welding also work for out-of-position welding

-Assuming a filler metal used for in-position (flat and horizontal) can be used for out-of-position welding 

Welders can’t always use the same techniques and parameters that they use on flat and horizontal welding and expect the same success with out-of-position welding. In addition to welding slower and with less heat input, it may also be necessary to manipulate the weld pool to produce an acceptable bead. This can be done by using a weave technique with most processes. 

Choosing the right process
Some welding processes make it easier to weld out of position, while others can be more difficult. Consider some key criteria for making the selection. 

Productivity requirements: If the application calls for the welder to climb up and down scaffolding just to complete two or three small welds at a time, the productivity of the welding process itself likely isn’t an important factor. Compare those types of applications to high-volume production environments where welding productivity is critical to the overall operation. When welding productivity is important, look for a process that delivers faster results. 

Welding environment: Welding outdoors versus in a shop should be considered. Gas-shielded processes typically work better indoors, while welding processes that don’t require shielding gas are better-suited to outdoor work such as structural or pipeline welding. 

AWS classification chart for SMAW electrodes
Figure 1

Welder skill: Some processes have a wider parameter range and can be more forgiving to welder technique and consistency and therefore, are more forgiving for out-of-position welding. If an operation has less experienced welders, it may be helpful to choose a process that makes it easier to produce good welds out of position. 

To determine which process meets the needs of a specific application, consider the advantages and limitations of each. 

Shielded metal arc welding (SMAW)
Because it does not require shielding gas, SMAW offers great portability and flexibility for outdoor applications. Many welders also are familiar with SMAW and often have the necessary equipment on hand.  

However, because SMAW is a slower process, it’s best suited for out-of-position applications where welding productivity isn’t as critical, such as those with less welds to complete. Also keep in mind that there is a built-in stop/start at the end of every electrode when using SMAW. 

Electrodes for this process are classified by positional capabilities, so look for an all-position classification for vertical or overhead welding. (See Fig. 1) Choosing a smaller diameter electrode allows for using lower amperages to help control the heat in out-of-position welding. 

The challenges of stick welding out of position can be minimized by using a lower amperage setting and manipulating the arc with a weave technique, which helps make the weld bead wider and flatter.

 
 

Flux-cored arc welding (FCAW)
There are two types of flux-cored arc welding: gas-shielded and self-shielded. With both types, the filler metal is classified by position, so look for a wire that is designated for vertical and overhead welding. (See Fig. 2) 

Flux-cored wire is the easiest to use for out-of-position welding because it’s very forgiving to variations in welder technique. This is especially true for gas-shielded flux-cored wire. 

Self-shielded flux-cored wire — because it does not require a shielding gas — is well-suited for outdoor applications as an alternative to SMAW. This wire is less portable than SMAW due to the addition of a wire feeder, but it offers much greater productivity. The higher deposition rates mean more filler metal is being deposited into the weld. In addition, stopping and starting is not required as frequently in the wire process, compared to SMAW.

Gas-shielded flux-cored welding is often the preferred option for indoor out-of-position applications. It produces very little spatter, delivers high deposition rates and requires less precleaning of the material compared to gas metal arc welding (GMAW). 

AWS classification chart for flux-cored wires
Figure 2

 

The slag systems in all-position FCAW filler metals allow for much higher heat inputs and deposition rates compared with other processes. It’s possible to more than double deposition rates for out-of-position welding with FCAW compared to GMAW. Also, excellent bead quality is possible in FCAW with no manipulation. 

For these reasons, FCAW wires are considered more forgiving and easier to use for vertical and overhead welding — even for less experienced welders. 

The FCAW processes are well-suited to applications that require a lot of welding, especially out-of-position welding. In many applications, it’s possible to use the same welding parameters for in-position welding as those for out-of-position welding because FCAW allows for a wide parameter window. This saves time and helps improve productivity.  

Gas metal arc welding (GMAW)
The GMAW process has two options for filler metals: solid wire and metal-cored wire. These filler metals, however, aren’t classified based on their position capabilities. 

Out-of-position welding with this process must use short-circuit transfer or pulsed GMAW, to achieve a lower heat input and produce acceptable welds. Be aware that the lower heat input will decrease the productivity and deposition rates of the process. Vertical down welding is often used to avoid the productivity losses of vertical up, but vertical down is very prone to lack of fusion and not acceptable in many welding applications.

Welding out of position with GMAW often requires the welder to spend more time dialing in the machine, and it usually requires a weave technique to produce a good weld appearance. The lower heat input needed for out-of-position GMAW can also result in lack of fusion in the weld. 

When comparing GMAW to gas-shielded FCAW, the flux-cored process is more productive and tolerant to parameter variations. GMAW can be — and often is — used to make acceptable welds out of position. However, if there is a lot of welding required, this may not be the best available option.

Gas tungsten arc welding (GTAW)
Like GMAW, GTAW is also an all-position welding process and the filler metals are not classified based on position capabilities. Successfully welding out of position with GTAW requires attention to technique and heat input. 

Lower heat is again critical when GTA welding out of position. A weave technique can be used with GTAW, but it is not as critical as it is with GMAW or SMAW.

Fabricators would not make a welding process change to GTAW to improve out-of-position welding, but those who are already using GTAW can successfully use the process for these welds.

Choosing the right process and filler metals 
It’s more difficult to control the various factors in out-of-position welding — from heat input and travel speed to weld puddle manipulation. Achieving success when welding out of position is all about choosing the right process for the job and knowing the proper parameters and techniques. And as with any welding application, continued practice always helps to gain the best results.