The metal fabrication industry continues to develop new alloys for new applications and products at a quick pace. This rapid development of different base metals sometimes requires new filler metals, unique shielding gases and equipment. In an attempt to keep up with the changes in CAFE requirements, the automotive industry is one of the most active market segments in this regard. These new steel alloys are designed for very high strengths; they are thinner and therefore, reduce automobile weight and improve safety. However, these new characteristics make bending, forming and trimming more difficult and make welding more challenging.
For business owners in this segment, the current material evolution is affecting power sources and procedures as well as filler metals and gases. Welding power sources must input less heat into these new thinner higher-strength alloys through wave form control and not just through the amperes and volts that were once the only power management we had.
By managing heat input, these businesses can reduce weld cracking and weld size as well as stress and distortion. As the automotive industry continues to use these alloys to meet the CAFE standards set by the EPA and the government, they will be able to leverage their greater strength and hopefully save lives.
With these changes, it is clear to see that robots will be more important than ever before to follow the stricter weld procedures those standards and materials require. These more stringent procedures will help to manage weld width, depth and speed in order to manage the heat input and maintain the material’s composition.
Nevertheless, we have yet to see all of the changes that will occur with filler metals. Base metals will braze welded, GMAW welded, laser welded, spot welded and maybe some new processes that we have yet to apply to these new requirements. Filler metals, therefore, become part of the solution.
Chemistry is an obvious requirement; however, mechanical characteristics will also come into play. Filler metal precision will be a mandatory requirement for effectiveness and success, which means the welding wires of the past will need to improve in terms of consistency of diameter, cast, helix and surface condition.
If you take several feet of weld wire from the box, drum or spool and lay it on the floor, you will see the built-in weld wire defects that are making your manufacturing world more complicated. But when a business is more cognizant of those defects – the cast, helix and twist – the equation might not remain so complicated.
Typically, welders prefer wire surface conditions with the smallest chemistry range. The simple acceptance of an AWS spec might be suitable for welding A 36 steel, however, these new higher-strength base metal alloys require tighter filler metal specs to be successful.
When was the last time that your filler wire supplier provided you with electron beam surface condition photos of the filler metal you are using? Regardless, your supplier was most likely still pleased with the fact that the wire cost was 5 cents less per pound than any other brand. The new cheap supplier gets the sale, but you’re left wondering why your rework rates climbed.
The cast of welding wire is essentially the diameter of the wire when you take it off the spool. Average weld wire packaged on a spool has a cast of 26 inches, whereas a true robotic weld wire does not have cast and instead forms a sine wave when laid on the floor. This permits a faster welding speed and less spatter because the weld wire is precisely melted into the joint.
The helix of welding wire is the distance the unspooled wire rises from the floor. The average wire might have a helix of 1 inch, which is acceptable for AWS but contributes to overwelding, more labor and more filler metal. The helix contributes to an oscillation of wire, and therefore, makes the weld bead wider. This increases heat, distortion, time and weld cracking.
Twist is more difficult to test than the helix and the cast, but it can be done in the field. To do so, pull 4 inches of wire out of the drum or from the spool. Bend the wire 90 degrees and hold the bent portion at the 12 o’clock position. Then, pull it out 30 feet and slowly release the wire so it can rotate. One rotation in 30 feet is too much and implies issues with wire binding in the torch and may lead to knots in the drum. Spooled wire generally has the biggest issue with cast and helix while twist is less common.
Engineering requests one-eighth of an inch weld, but the cast and helix make that impossible. If the weld widens to three-sixteenths of an inch, some would think nothing of it. If one selects the overwelding expense or OWE of 0.072 for three-sixteenths of an inch through .032 for one-eighth of an inch, the difference is 0.042. That seems like a small number, right? So why worry about it?
The most important reason for worrying is because 0.072/0.042 is a 225 percent increase in labor, wire, time or expense to make your product. After working hard to trim every expense you have to make a profit, this one small detail can make it even more difficult while also reducing your bottom line.
The solution? Test your wire frequently. Measure your weld sizes and train your operators to look for wire issues. Simply making the weld bigger due to weld wire defects is an expense you can ill afford.
This excess consumption adds to every part of your fabrication expense, including labor and the time it takes to make the weld. It also can increase spatter, distortion and cracking. So, don’t let your weld wire supplier be the only one benefiting from this expensive situation.
It does. Today, in American fabrication, 75 percent argon and 25 percent CO2 is still the most common shielding gas. This gas mixture was developed to bridge gaps and was also developed for use on very thin sheet metal. The common use of this gas mixture, when there are 8 to 10 mixtures that may more kindly impact your bottom line, can come as a surprise.
The good news is that if you investigate this with a knowledgeable gas technician, you may see a very quick – and inexpensive – improvement in your bottom line. A mixture of 75 percent argon and 25 percent CO2 is a very fast freeze shielding gas, which can produce a high crown similar to CO2 but not quite as tall. This crown can easily cost you 7 to 15 percent in speed and grinding.
Measure your weld size against the engineering drawings, as oversized welds are very costly. It would also be helpful to look at the new gas mixtures from your gas supplier. In one case study, a recent change in shielding gas reduced reject rates from 20 percent to less than 1 percent.