The welds connecting the different components and materials of any fabricated item define the integrity of the finished product. Achieving high-quality welds requires the right angles, motions, knowledge of materials and more.
Ci Metal Fabrication, a custom industrial metal fabricator located in Meridian, Miss., doesn’t take those statements lightly. The company utilizes highly skilled craftsmen to meet the precise specifications of its customers when performing presswork, power forming, cutting, shearing and, especially, welding.
The following information should be useful to anyone looking to achieve top-notch wire welds. It is based on Ci Metal’s experience that has been growing ever since it opened its doors in 1967. It’s also based on the company’s extensive experience welding products that feed into a variety of industries, including power generation, pulp and paper, chemical and automotive.
For a strong weld, clean the metal with a degreaser and grind a slight bevel along the edges. This ensures the weld penetrates as deeply as possible and helps achieve a flush look during the grinding process. Next, tack weld the pieces together at a couple of places along each joint. Tack welding guarantees the materials are in place and won’t shift.
After the tack welds are secure, the final bead welding takes place. It’s important, however, to resist the temptation to overweld. The more metal deposited during the welding process, the more that needs to be grinded off.
For so many welders, especially those that are new to the job, some confusion can arise in terms of the best position to use when wire welding. Those two positions are pushing and pulling. Typically, a pushing position is best when using shielding gas, and a pulling position is best when using flux-cored. While each welder has a preference, the position can also be influenced by what is being welded, including materials and angles.
One of the benefits of the pushing position is that the welder has a clear view of the weld joint. When performing this position, which produces a wider bead and less penetration, the electrode must be pointed forward at the leading edge of the weld. A benefit of the pulling or dragging position is that the weld results in a narrower bead and more penetration.
There is a range of different welding joints that can be produced. The four most common joints, which are the fundamentals for all welders, are butt joint, lap joint, T joint and corner joint. There is a preferred gun angle for each type of joint to ensure optimum penetration.
Butt joint: A butt joint is the most common and simplest types of joints. It consists of two pieces of metal that lay parallel to each other. To weld the metal edges together at the seam, it is best to hold the gun at a 90-degree angle to create a stringer bead, or straight line. Stringer beads are usually thinner welds than weave beads, but are often used for butt joints.
Lap joint: A lap joint is formed when two pieces of metal overlap. A single lap joint occurs when one side is welded while a double lap joint involves both sides. A double lap joint weld should be used on a structural piece for durability. For the highest quality weld, move the gun in a loop or cursive ‘e’ motion at a 60- to 70-degree angle.
T joint: A T joint consists of two pieces of metal that intersect at a right angle to form a T shape. For this type of joint, it is best to use a half moon or cursive “e” motion for better penetration when moving across the joint. To achieve a higher quality weld, hold the gun at a 45-degree angle and move up and down quickly.
Corner joint: A corner joint is formed when two pieces of metal meet at a right angle to form the letter “L.” Typically, the outside corner joint is welded, but a double welded corner joint can be used for extra stability. Hold the gun at a 45-degree angle to achieve a higher quality weld.
A welding plan
Wire welding allows for different kinds of metals to be welded together. Regardless of the materials being welded, including dissimilar metals, if the proper procedures are followed, there should be few issues with making a quality weld. The best way to achieve good welds is to develop a thorough welding plan for the specific project.
The first step is to study the plans and drawings to identify the types of welds that are required, the material grades being joined and the required joint preparation. Second, produce sample weld coupons that mimic the welds required. These coupons are sent to a testing lab to have a bend/break test done through a third-party certified welding inspector (CWI) or an in-house CWI.
The last step is to create the procedure qualification report (PQR) and welding procedure specification (WPS) for each of the types of weld required. The PQR and WPS determine the parameters of the welding that need to be performed, such as amps, volts, travel speed, electrode, thickness of metal, type of metals being joined and the weld joint configuration.
It only takes one wrong move to put the quality of a weld in jeopardy. Examples of what can cause a bad weld include:
- using the wrong filler metal for the materials being joined
- not performing a required pre-heat or post-heat process
- 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
- having a fan directed toward the weld station that can blow away the shielding gas
The bad welds themselves consist of too much weld deposited, undercuts, pin holes, porosity, improper penetration, cracking, lack of fusion, excessive weld spatter and even weld failure later in the product’s life.
Properly calibrating welding machines is required to control welding quality. In time, welding machines lose their calibration and performance. Therefore, it is important to 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.
Lastly, to ensure a quality weld, it’s critical to use wire that is in good condition. Quality procedures need to be followed when purchasing and storing new and used spools of welding wire. Moisture and cool weather can damage the wire, whereas rust and other contaminates can damage the quality and integrity of the filler metal. Because of this, it is necessary to store welding wire in a temperature-controlled storage cabinet when not in use.
Overall, welders should be confident that the quality of their welds will increase over time as experience builds. And taking advice from long-time welding outfits, such as Ci Metal, can only speed up the time it takes to gain experience, increase quality and perfect the craft in general.