Making sure of the quality of a weld is extremely important. A weld that does not reach the proper standards poses a serious risk, maybe even a life-threatening one. This is why it is essential that the quality of the weld is checked.
What is interesting is that the quality is often examined even before testing procedures are performed. It would seem logical that checking for such things as porosity or distribution would be part of the testing procedure, but this is not the case. Instead, a quality examination of the weld begins by looking for blemishes or weak spots that pose a serious risk to the integrity of the weld.
Performing a Weld Testing Inspection
To inspect for problems, this is done visually. This particular article addresses inspecting for a GMAW weld, but can be applied to many different types of welds that have been performed. The purpose of this examination is defined weak or defective sections that need to be corrected.
The reason that this inspection is done prior to testing is to save time and reduce costs. If you think about it, performing this inspection makes a lot of sense. Consider that if there is already a weak spot that can be seen before a test is performed, money can be saved on cutting a section or testing a particular welded area because a defect has already been found.
This is why it makes sense for the welder to do a thorough examination and inspection of the welding area. No equipment is necessary for this, although it may make sense to have a magnifying glass or similar type of lands to help find porous sections. When performing an inspection, these are the kinds of things that you should be looking for:
Distribution focuses on two main areas. The first of these is that there is an equal distribution of welding material across the entire joint. The second is that the two materials have been joined properly. This is especially important if one material is being melded into the other. If there are some areas where the weld is not distributed evenly, it can present a weakened area which is a danger.
You want to inspect to ensure that the weld area is free of any waste materials, such as flag. As the slide cools, it should be easy to peel away. This is true in most types of welds. If you see that there is a large amount of slagged that needs to be cleaned, it is often due to the fact that the material was not properly cleaned prior to the weld being performed.
One of the most important defects to check for is if there are any porous holes, commonly referred to as porosity. These holes present weak spots in the welded area. This usually occurs because the base metal was dirty or had an oxide coating on it. If you are performing a MIG or TIG weld and find porosity, it is often the case that there was more shielding gas that was needed when the weld was being performed. In the case of aluminum welds if porosity forms, it is a major indicator that there was an insufficient amount of gas that was used.
One factor you want to pay close attention to is the tightness of the weld. One area where this frequently occurs is with oxyacetylene welds. What happens with autogenous welds where there is no filler material used is that a gap develops. This can be very dangerous, as it provides defects in the weld that weaken it.
If you are performing a weld where a liquid is being held in a container or is being held back by the material, then this is one of the easiest types of welds to look for defects. If there is any kind of leak that appears that this is a clear indicator that there is a defect in the weld itself. you can also perform this type of check through the use of soap bubbles which can be squirted across the welding area.
One of the primary tests that need to be performed on welds is to ensure that they meet strength requirements. There are several destructive methods that can be used to test. Check for methods that can assist you in this process.
Common Weld Faults
There are several different types of weld faults that are common. Here are some of the examples.
In this type of weld there is a failure of the filler and base metals to properly fused together at the root of the joint. This type of bridging occurs in groove welds when the metal that is deposited and the base metal do not fuse at the joint. This commonly occurs because of an incomplete penetration at the joint, usually because only one side of the welding area has been properly welded.
If this occurs, there are several factors that may be at the root of the problem. The root face can be too big, the root opening to small, the included angle to small, the electrode too large, or the rate of travel to high. There can also be an issue with the welding current being too low.
Lack of Fusion
This occurs when there is a failure of the welding process to fuse the layers together. Instead, the weld metal just rolls over the plate services, a defect that is frequently referred to as “overlap.”
This can be caused by several factors, with a failure to raise the melting point of the base metal as the most common. Other issues can include such things as dirty plate services, the wrong current adjustment, or if proper electrode size or type. An improper fluxing can also be a major cause.
This term refers to the burning away of the base metal at the toe of the weld. This is caused by such issues as the current adjustment being too high, the arc gap being too long, or their being a failure to fill up the crater thoroughly with the welding metal.
Slag inclusions occur when there is an elongation or globular pockets of the metallic oxides or other solid compounds. This leads to a production of porosity in the welding metal. In arc welding, slagged inclusions frequently occur because of electric coating materials or fluxes when conducting multiple layer welding operations, a failure to remove the slagged between the layers causes the slagged inclusions.
While a common thing to occur, it can be prevented. This starts by preparing the groove and weld properly before the deed is deposited. You also want to remove all the slagged and make sure that as flag arises to the surface, that it is properly treated.
This occurs when there is the presence of pockets that do not have any solid material in. This is where they differ from slagged inclusions, as they contain pockets of gas instead of a solid. This occurs for one of two reasons. The first is that gases released by cooling the weld or that gases form by chemical reactions within the weld.
There are three primary steps that you need to follow to ensure that you prevent porosity from occurring. The first is to ensure that you are not overheating or undercutting the welding metal. You also do not want to have too high of a current setting or to have too long of an arc.
Virtual Inspection (VT)
This is another form of non-destructive testing. In this particular type of test, the weld is examined by examining with your eyes to determine if there are any surface discontinuities. This is the most commonly used method for testing the quality of a weld. There are several advantages that come from performing this type of test. They include:
- decreased cost.
- No costly equipment needed.
- No power source is required.
- Makes for a quick evaluation of the weld area.
However, there are disadvantages to this type of test. They include:
- an experienced professional can only conduct such a test.
- Exceptional eyesight is required.
- Internal defects can be easily missed.
- Human error is a major factor.
To perform this type of test, the following steps should be used:
- Testing and inspection methods should be created to ensure that the entire weld area is inspected properly.
- Prior to performing the weld, all the materials need to be properly inspected.
- As the weld is occurring, quality tests should be made.
- When the weld is completed, an additional inspection is conducted.
- All problem areas are properly marked and repaired. Documentation on repairs should be included.
Visual Weld Equipment
To perform a proper visual inspection, the following equipment is needed.
Fillet Weld Gauge
This device is used to properly measure the flatness of the weld. What may occur is that a convexity (weld is welded outward) or can cavity (weld is rounded inward) may occur. A special type of lens is used to observe and check for this. This may even include a magnifying glass.
Inspection Before Welding
When conducting a visual inspection before the welding process begins, you want to review drawings and look at the welding position and see how it properly corresponds to the drawing and specifications. Check all fillet welding symbols and use the proper procedure and local codes to meet specifications.
Weld Material Inspection
There are a few things you want to check regarding the materials themselves. First, begin by ensuring that the materials used meet the proper specification. Electrode size, grade, and gas selection should also be checked. Search for any defects, things like mill, rust, or lamination. Also make sure that all materials are prepared at the correct angle is.
When conducting an assembly inspection, begin by checking for the fit. This should ensure that the alignment of fixtures and jigs meet the proper specifications. You also want to look for any spatter from previous jobs or any other issue that may affect the cleanliness of the welding area. If tack welds are to be used, you will need to check the quality of them as well. Keep in mind that the tack weld must be made with the same electrode as the main weld.
You want to check for any kind of damage or defects in the equipment you are using. Common types of problems may be damaged to the cables, ground clamps, or electrode holder. This can create an issue with the arc voltage. You also want to ensure that the amperage meter meets the proper range for specification of the weld.
Visual Inspection During Welding
When inspecting the welding area during the weld itself, make sure that electrodes meet the proper size, storage, and type necessary. For example, low hydrogen electrodes are kept stabilizing oven during the welding process. Make sure that is you are performing the rib pass that you are monitoring for cracking. You want to inspect the joint with each weld pass and look for such issues as undercutting. If a contour is required, you will need to monitor and make sure that you are meeting the specifications. Also, look for craters that will need to be filled.
Inspection after Welding Is Concluded
At this point, you will want to make sure that the weld properly met all of the specifications and standards provided in the documentation. You want to check the size with gauges and prints. Examine the finish and contour and check for cracks, overlaps, or undercuts. Look for any spatter or other debris that could become an issue.
Gas Weld Testing
When conducting gas welds, the inspection procedure is slightly different. To conduct this type of inspection, include the following elements to search:
- Perform a proper inspection to ensure that the weld is consistent throughout. The two edges should form parallel lines across the entire weld.
- The weld space should be slightly convex. The reinforcement should be no more than 1/16 of an inch above the plate service. The convexity should be even across the entire length of the weld. Make sure that there are no places where it is high in one location and low in another.
- As you examine the weld, you should see that the ripples in the face are fine and evenly spaced. There should be no excessive spatter, pitting, or scale.
- The weld’s edges should be free of any undercut or overlap.
- All starts and stops should blend together evenly and it should be very difficult to determine where they have taken place.
- Lastly, ensure that there are no holes or cracks, and film them if there are any.
If a butt joint is performed, you want to make sure that there is complete penetration on the back side throughout the root of the joint. You should see a small bead forming on the back side if it has been performed properly.
Fusion of Lap and T-Joint
One last tests for lap and T-Joints. To check this type of weld, you want to put pressure on the upper plate until you are able to bend it in two. If you have not properly penetrated throughout the welding area, then the plate will crack at the joint. If it breaks, then take a close look at the penetration and fusion. You will likely find that you have not reached the proper penetration level so that fusion occurred.