It’s no secret that everyone likes a little DIY if you believe it will cut costs, but welding stainless steel can get complicated if you’ve never done it before. And depending on what the finished product will be used for, welding the steel is also reliant on the thickness and finish of the material.
Another issue you may run into when welding stainless steel is that there are a lot of different alloys available, and using the right filler material, settings and shielding gas, among other things, for each alloy is paramount.
The Skill Behind Welding Stainless Steel
Contamination
Even trace amounts of contamination will create an issue with stainless steel. The metal must be meticulously cleaned before welding and be free of all contaminants such as paint, oil and rust.
Heat Monitoring
Stainless steel tends to show up every imperfection in the weld and is an unforgiving task. One of the biggest challenges for inexperienced welders is that stainless steel retains heat very efficiently, and applying excess heat will warp the steel, and it may even further distort as it cools. Maintaining the correct amperage is an important step in heat correction too.
Avoiding a Large Filler Diameter
More heat is required for thicker filler rods or wire, but with stainless steel, because you need to keep the amps down, one must avoid using big filler rods.
Proper Fit-Up
To further counteract the need to add excess heat to the metal, it’s important to take the time to fine-tune the fit-up of the workpieces and use the proper amount of filler material.
Using the Correct Electrode
Using a stainless steel filler alloy that matches the base metal will prevent corrosion and rust problems. You also want to avoid contaminating the stainless steel with carbon in the HAZ, which can also cause rust.
Using the Right Torch Angle
To avoid issues with slag inclusions in the weld, it’s necessary to drag the electrode to allow the flux to rise to the top of the weld pool to properly cover the bead. The angle of the drag plays an important role in achieving this.
The Right Wire Stick Out
With MIG and flux-core welding, the right stick out will create a smooth arc when you begin. The distance between the nozzle and metal as you weld also has an impact. Trimming the wire tip every time you lay a bead with flux-core welding helps you get a better start, and doing the same with MIG welding will ensure a proper stick out and clean tip.
TIG Weld Puddle
If the weld puddle diameter gets bigger than the base metal thickness, you will need to use your fingertip or foot pedal to reduce the heat. Also, make sure to eliminate craters by tapering the current down and using filler metal until the puddle gets hard.
Rate of Deposition
Various welding processes have varying deposition rates. When it comes to welding stainless steel, there is, unfortunately, no substitute for experience in this as well as knowing how it varies with the different welders.
Travel Speed
Travel speeds are important. Moving too slowly creates excess heat in stainless steel. Not getting the travel speeds correct will create issues like the slag not covering the weld enough and the metal turning grey. There may also be porosity issues which means the weld will be prone to rust.
Rust Prevention
Beyond using excessive heat, which causes the metal to lose its corrosion resistance, stainless steel welds can rust due to reactive gasses in the air. It’s thus imperative to provide a good blanket for shielding gas.
Cleaning the finished weld completely, including any discolouration, greatly assists in rust prevention. Knowing and using the correct method of cleaning will prevent contaminating the weld.
Ventilation
Welding stainless steel produces hexavalent chromium gas, which is highly toxic, so optimum ventilation is required to protect the welder from breathing in harmful fumes.
As you might have realised by now, welding stainless steel takes experience and practice, and at the end of the day, you need to weigh up if there would be any cost savings in attempting it yourself or instead enlisting the help of the experts who offer stainless steel welding services and who have the tools and knowledge readily on hand to get the job done right from the get-go.
Steelmor is the leading supplier and manufacturer of stainless steel in South Africa. Give us a call today on 011 747 5700 for everything stainless steel.
