Welding food grade stainless steel is delicate work that requires a deft touch. It can be all too easy to make some severe welding mistakes if the designer or welder aren’t aware of the specific requirements of the specific food application the steel wire basket or tray is going to be used for.
So, what are some of the worst food grade welding mistakes and how can they be avoided?
1: Failing to Eliminate Burrs/Sharps
In many food preparation applications, the wire baskets will be manually handled by workers in a factory, restaurant, supply storehouse, etc.
Burrs and sharps that are left on the basket by some welding processes can cause injuries to workers and impede productivity. So, eliminating these sharps and burrs is a must.
This can be done either by using welding processes that minimize their appearance or finishing the surface of the basket thoroughly through sanding, electropolishing, or similar processes.
2: Compromising Resistance to Corrosives by Over-Stressing Materials
Some welding processes can inadvertently reduce the integrity of the protective oxide layer that keeps stainless steel stainless. In severe cases, a mishandled weld can strip the oxide layer and contaminate the surface of the steel, creating a welded joint that is susceptible to corrosion.
Or, a welding process might introduce stress cracks and microfractures that compromise the integrity of the weld and its corrosion resistance.
Some welding processes, such as resistance welding, are good for minimizing the impact of the welding process on the chemical resistance properties of stainless steel—when performed correctly. If the steel is subjected to too much force during the weld, or is heated too much for too long, then stress corrosion cracking and other issues may occur.
One way to ensure solid, error-free welds is to use a MFDC welding system that can automate the timing of a stainless steel weld with incredible precision. Marlin’s own MFDC welding system can complete a weld in 2/1,000 of a second—roughly 30 times faster than a traditional AC welding system.
This prevents spatter, blistering, and other deformities in the weld as well.
3: Alloying Welds with the Incorrect Filler Material
For welding methods that require the use of a filler material to bond two metals, using the right filler material is crucial. While rare for any experienced manufacturer, sometimes, a filler might be used that doesn’t react well with the metals being welded.
In some cases, a “galvanic couple” could be created where the electrochemical potential difference between the filler material and the metal being welded are severe enough to create an anode and a cathode. This leads to corrosion (faster in the less noble anode metal, slower in the more noble cathode metal).
Eventually, the welded joint corrodes and becomes weaker, compromising basket strength and integrity.
The best solution is to either use a welding procedure that doesn’t require filler, or to ensure that the filler material is one that won’t create a galvanic couple with the metal being welded. This can be tricky since different alloys have different electrical potentials.
4: Welding Dissimilar Metals
In most cases, it’s best to weld two wires made of the same material whenever possible. Not only is welding two dissimilar metals more complicated than welding two of the same alloy, it introduces opportunities for new failure modes and other risks for food handling applications.
These risks include corrosion from galvanic coupling, heat stress cracking from differing thermal capacities, and food contamination from corroded surfaces retaining and transferring liquid runoff or bacteria from one load of food to the next (or, worse yet, depositing rust onto/into food products).
Welding dissimilar metals is a common mistake that can be easily overlooked in the design phase by an inexperienced engineer. The best fix is to avoid welding two different metals together unless absolutely necessary. Another potential fix is to use a protective coating to keep the basket’s welded surfaces from being exposed to the open air or direct contact with the food products being held.
These are just a few of the potential mistakes that could be made when welding food grade metals together for any application in the food industry. To avoid these issues, it’s important to use a food tray/basket vendor that has the knowledge and experience to understand the potential complications of different welding practices and the tools to avoid most major pitfalls.
Learn how Marlin Steel leverages top-class training, welding automation, and physics modeling software to prevent food grade welding mistakes today!