Using best practices has been a standard at Tampa Sheet Metal for almost 100 years. Our shop has invested into the safety of the employees and that includes better equipment like a fiber laser and better sheet metal machines that give us the unparalleled consistency that our customers expect from a metal fabricator that can handle high volume parts.
Below are some common problems with wire welding from fabricator.com that we found interesting to share. If you have questions about welding, fiber laser, punch press machines and anything related to sheet metal, call us today and talk to one of our experienced employees and email us direct at Sales@tampasheetmetal.com
Common problems in wire welding
Welding typically is the most critical and scrutinized process in fabricated items, weldments, and pieces of equipment. The integrity of any finished product requiring welding is only as good as the welds joining together the different components and materials. Because of this critical nature, all quality assurance inspections and requirements revolve around the welding operation.
As with any fabrication process, there is a right way and wrong way to weld. And even when done correctly, it’s important to be aware of the other factors that can sabotage the job.
Solid-wire Welding Versus Flux-cored Welding
One type of welding that often is performed is solid-wire welding. The advantages of this type of welding are that it produces a very clean weld and it is better suited for thin metal. A solid wire does not puddle and flow as needed to fill a joint consistently, making it unsuitable for thicker metals. It is also harder to apply a weld joint accurately as it tends to stick to one side of the joint more than the other. If solid wire must be used on thicker material, you may need to use multiple weld passes and then gouge or grind out previous weld passes until the weld joint is fully fused.
Another type of welding is flux-cored welding, in which a hollow wire is filled with flux. The advantages of this process is that it is better suited for thick metal, it puddles and flows into weld joints consistently and accurately, is more forgiving, fuses equally, and provides good joint penetration.
The disadvantages are that the flux-cored wire puddles and runs out too flat and quickly when this method is used for thinner metals. The flux burns, leaving a charred discoloration on the weld that requires extensive brushing and cleaning to remove. If you have to use flux-cored wire on thin material, be sure to use welding tabs at the beginning and end of the weld joint to create “dams,” which will help keep the weld from flowing out of the joint.
Wire Welding Similar and Dissimilar Materials
Regardless of the material grades being welded or whether you are joining similar or dissimilar metals, if you follow proper procedures, you shouldn’t have a problem making a quality weld. The best way to achieve good welds is to develop a thorough welding plan for the specific project. Start at the beginning and follow the necessary steps one by one until complete.
First, study the plans and drawings to identify all the types of welds, material grades being joined, and the joint preparation required. Second, produce sample weld coupons that mimic the welds you will need. You can then send these coupons to a lab for bend/break testing either through a third-party certified welding inspector (CWI) or an in-house CWI. Last, create the procedure qualification report (PQR) and welding procedure specification (WPS) for each type of weld required on the project.
The PQR and WPS determine the parameters of the welding that needs to be done, such as amps, volts, travel speed, electrode, metal thickness, material type being joined, and the weld joint configuration. These are just a few critical items listed on these reports and specifications; they contain additional information as well that you need to follow.
What Makes a Bad Weld?
It only takes one wrong move to put the quality of the weld in jeopardy. Some examples are using the wrong filler metal for the materials being joined; not performing pre- or postheat processes; using the wrong shielding gas; running the wire at the wrong speed; using the amps or voltage outside the proper range; not applying the proper joint preparation; and even something as simple as having a fan blowing toward the weld station that can blow away the shielding gas. These factors all can result in a bad weld.
What makes a weld bad? Too much weld deposited, undercuts, pinholes, porosity, improper penetration, cracking, lack of fusion, and excessive weld spatter. For example, everything on the weld may look good visually even if you use the wrong filler metal or electrode. However, problems can arise later in the product’s life when it is in use. During the stress of operation, vibration, and hot and cold expansion and contraction of the metal and welds, the wrong filler metal may have less or more expansion than the metals it joined together. This difference could cause the welds to break, leading to product failure and physical or financial damage to the end user.
Properly certifying welders is a requirement for controlling weld quality. A welder qualification is similar to the weld procedure qualification (WPQ) in which test coupons are welded together. The coupon undergoes a bend/break test, and upon satisfactory results, the welder is granted a certification once he or she has passed. Certified welders are issued a stamp number, which is used during production to identify who performed the welding. This initiates accountability and traceability, which increase quality assurance of the welder.
Also, calibrating welding machines properly is an important factor in controlling quality. Over time welding machines tend to lose their calibration and performance. When this occurs, consult a calibration expert who can test the machines periodically to make sure the performance output matches the settings entered into the machine. A properly calibrated welding machine is a necessity to get the proper performance.
Finally, ensure the wire that you are using is in good condition. There are quality procedures that you need to follow when purchasing and storing new and used welding wire spools. Moisture and cool weather can damage the weld wire, whereas rust and other contaminants can damage the quality and integrity of the filler metal. Because of this, store welding wire in a temperature-controlled storage cabinet when it’s not being used.
Author: Steven Guisgond- not a TSM employee