• Duane Miller, manager of engineering services at the Lincoln Electric Company

• David Mills, quality control manager at Canam Steel Corporation

• Steve Hobbs, design engineer at Vulcraft

• Josh Roberts, quality control supervisor at New Millennium Building Systems

Importance of Welding in Joist Manufacturing

Welding is an integral part of the joist manufacturing process. Since all joist connections are welded, welding is inherent to both the welding and joist production industries. 

Because welding is an important part of joist manufacturing, different checking systems are in place to ensure quality, safety and efficiency throughout the manufacturing process. “Welding is integral throughout each individual process. And it’s essential that the welders have the necessary skills to accomplish the welds that are needed,” says Mills. He stresses the importance of making sure welds are completed properly, placed where they belong, and meet requirements like size and amount.

Roberts echoes that sentiment and states, “The welders in our facility are essential to the product we put out. They are the ones who make joists work the way they’re supposed to and perform as engineered.”

Certification vs. Qualification

Outside of the welding industry, it’s common for lay people to use certification and qualification interchangeably. However, the difference between these two words holds weight. Certification refers to the actual paperwork behind welding qualifications –– it makes the qualification official. 

Qualification, on the other hand, refers to the test proving welders can perform the job. Qualifications prove a welder knows how to perform quality welds effectively and safely in a given position or process.

Staying qualified and sticking to qualification standards is important because it maintains consistent quality. Further, deviating from code could potentially be dangerous depending on which standards are neglected.

Welding Tests

There are tests available for a variety of joints. Some tests qualify a welder for different positions whereas others qualify for a single position. Welders are tested within the code they’re currently using and must retest when working on different codes.

According to codes D1.1 and D1.3, welder qualifications are valid indefinitely, given the welder has used the welding process every 6 months. Qualifications expire after six months if a contractor is unable to verify that a welder has used the welding process they were qualified with. Welders must keep up to date with their certifications, which typically isn’t a problem if they are working in the field where they are continuously required to retest. Welders should be tested by each new employer. Also, an inspector may require a welder to be requalified if there is a reason to question his or her ability. 

“If a welder changes jobs but returns to their original position in less than 6 months, their certification is still valid. If they come back and it’s been more than 6 months, all we have to do is retest them with the original test,” Mills says.

Most tests performed are 1G plate certifications. In this test, two plates are cut at an angle with a back bar, then welded in the flat position with the joint filled. Inspectors take two cross sections out of the test and bend the root side or face sideways to inspect for cracks, voids or openings.

All tests are prescribed in the appropriate D1.1 or D1.3 codes; however, if a welder is welding in different positions the test could change or the orientation of the test could alter.

Nondestructive measures test welds using nonintrusive measures like X-ray or ultrasonic inspection. There’s also mechanical testing, which includes measures like bend and tensile tests. This type of testing mechanically destroys the weld to check quality. Ultimately, the contractor and joist manufacturer decide which testing route to take –– mechanical or nondestructive.

Testing and requalification processes haven’t changed much over time. However, nuances within the testing processes change as new codes emerge. “Inevitably, when new codes come out, there are some refinements and tweaks. We must look through all the details and determine whether they require us to requalify our welders or not,” Miller says. He expresses the importance of staying informed and up to date on new developments in codes so companies can correctly qualify their welders within the new adjustments. Additionally, Technical Digest No. 8 states “welding personnel shall be tested on a manufacturer determined schedule such that each welder is re-qualified, at a minimum, at least once every 2 years on each process and position for which he or she will be required to weld in the production environment.”

D1.1 and D1.3 Codes

In D1.3 testing, Mills explains that a plate is bent at a 90-degree angle to imitate a flare bevel groove weld. Then, there’s a lap joint fillet weld. “When we do the break test on these for D1.3 to a structural member, that qualifies welders for anything less than an eighth of an inch thick,” he says. It’s generally easier to perform welds on thinner materials than thicker materials.

The main difference between D1.1 and D1.3 is the thickness range they cover. D1.1 covers 1/8 of an inch and thicker whereas D1.3 covers 3/16 of an inch and thinner. Miller explains there is a deliberate overlap of about 1/16 of an inch to try and keep people in one code.

These two codes have been adopted because of nuances when welding on thicker material versus thinner material. How a welder designs welds on a thicker material looks different than the design for a thinner one.

The Steel Joist Institute has adopted D1.1 and D1.3 with a few special exceptions. One example of a special exception focuses on tack welding. “D1.1 requires a tack weld to either meet all the criteria as a regular weld or be incorporated into the final weld,” Hobbs says. He continues to explain that since tack welds are temporary and can’t hold much strength, this D1.1 requirement doesn’t apply.

Inspection Techniques

Visual inspection is a process control approach to quality used throughout the welding process and once the product is completed. Process control approaches build quality in whereas the after-the-fact inspection waits until there is a finished product. If a welder starts with good material, follows welding procedures and fits up the joint, the outcome will be high quality. Visual inspection affirms the process control approach to quality.

At New Millennium Building Systems, Roberts explains that they perform an extra weekly test for each of their physical lines. An inspector will randomly pick a joist and reinspect it on top of what other inspectors have done. “We do monthly destructive testing where we’ll perform an acid etch test, which verifies for penetration. Also, twice a year, we do a load test where we’ll load a joist to full failure. This tests both the design and welds.”

Hobbs says that a typical visual inspection at Vulcraft happens after a joist leaves the weld pit. Two inspectors are stationed on each line and look at every welded joint. “There’s also periodic full-scale destructive tests. “We pull a joist randomly, usually once or twice a month, and fully load test that to make sure it’s adequate,” he says. Visual inspection is the most commonly used technique because on some assemblies, it’s impossible to perform nondestructive techniques like X-ray or ultrasound.

It’s vital that proper welding processes are followed through every stage. Inspection techniques, whether they be visual, mechanical or nondestructive, are in place to ensure quality control among joists and welds alike.

To learn more about welding qualifications, codes, tests and inspection techniques, read Technical Digest No. 8 or check out our free recorded webinar “Welding In, On and Around Steel Joists.”