Stainless steel is a popular building material long heralded for its durability and substantial resistance to corrosion. Welding with this attractive metal does pose some unique challenges that need to be considered before launching into a project with stainless steel.
Let’s take a closer look at the pros and cons of working with this substance and examine the best ways of welding stainless steel.
Stainless Steel Welding
Stainless steel can be welded with shielded metal arc welding (MIG), gas tungsten arc welding (TIG), and stick welding, and each of these processes will yield a slightly different result.
Stainless steel retains heat very efficiently, which makes welding it a bit more difficult especially for the novice welder. When faced with excessive welding heat, stainless steel can warp from high temperatures and even distort during the cooling process.
It can also be very unforgiving aesthetically as it displays every blemish and scratch mark that’s left behind. Similarly, if you’ve ever welded on a metal table, you know to take precautions before starting because it scratches so easily. All of that is to say that stainless is not very forgiving when it comes to hiding mistakes and tends to favor the more experienced welder.
To find the best welding process for your project, consider the following factors: the welder’s skill level, the aesthetics of the final piece including bead appearance, the thickness of the metal plus the costs and timing factors of the project. If artistry is paramount, then the finesse of TIG welding could be a good fit, but if speed and efficiency are a priority, then MIG welding may be a better process.
Methods for welding stainless steel
While there are a variety of methods for welding stainless steel, there are three that are used most commonly by welders in the United States. These stainless-steel welding methods are TIG welding, resistance welding, and MIG welding. Let’s discuss them one by one.
1. Tig Welding or Gas Tungsten Arc Welding
Offering high quality, versatility, and longevity, TIG is the most commonly used stainless steel welding process. This welding process creates a low heat input, which makes it perfect for thin material.
The argon gas is often mixed with other gases, depending on the needs of the specific project, including helium, hydrogen, and nitrogen. To prevent oxidation and increase resistance to corrosion, a single-sided welding process can be used to create inert backing gas protection between the interior and exterior welds.
2. Resistance or Spot Welding
Resistance or “spot” welding, as it is often called, is one of the most economical types of welding. The resistance welding (RW) equipment is incredibly versatile, which means it can be used on both small and large projects.
RW uses an electrical current to heat frayed metal edges and seal them together. This type of welding is exceptionally productive on metal with a low melting point because it can be tailored to prevent distortion of the metal.
3. MIG Welding or Gas Metal Ac Welding
MIG welding is a semi-automatic process that when done correctly offers a strong joining of two pieces of stainless steel. This process uses an argon-rich shielding gas and a solid wire electrode.
MIG welding is popular because it allows the welder to utilize a pulsed current supply, which can make it easier to weld those tough-to-reach spots on complex stainless-steel projects. Other gases mixtures, including those with helium, oxygen, and carbon dioxide, are often used to stabilize the arc and improve the quality of the weld.
Choosing the right method for welding stainless steel really depends on what qualities you’re looking for. If you’re looking for a more affordable weld, spot welding might be the best option for the job. But if the material we’re working with is thin, then TIG or gas tungsten arc welding might be the better choice.
Does welded stainless steel rust?
Under normal conditions, stainless steel withstands corrosion of all kinds. However, in extreme circumstances, stainless steel can rust. This occurs when the chromium oxide layer – the very element that protects stainless from rusting – is destroyed or removed. Sometimes this can happen during welding, either during the heating or cooling process.
Even with TIG welding, rust can be one of the biggest challenges of welding with stainless steel. That’s why cleaning and prepping your stainless before you start is so important. With a properly cleaned and prepped piece of stainless steel, the chromium oxide inside acts as a protective seal against rust during the welding process. It can help the stainless heal itself from discoloration and permanent marks.
How to MIG Weld Stainless Steel
Whether you are the welder working on auto parts in the garage or the one repairing damaged kitchen sinks, knowing how to weld stainless using MIG welding is beneficial. Stainless steel is best known for its long-lasting and rugged properties. Learning the process of MIG welding may seem complicated, but the basics are relatively simple.
Most welders prefer MIG to weld stainless steel and other metal forms due to the welding’s straightforwardness and simplicity. Over the years, technological advancement in the welding industry has enabled the use of MIG welding robots, especially in industries, to boost production.
Factors to Consider During Stainless Steel Welding Using MIG:
1. Selection of an Inert Gas Blend
The most significant task in MIG welding is selecting the ideal inert gas. You do not want to find yourself using completely inert shielding gases such as argon or helium for the stainless steel MIG process. Remember, the arc in the MIG process involves using a filler material, which is different from other methods like TIG. Ignoring this vital factor could have negative impacts on the efficacy of the welding process.
2. Bracing the Joint During Welding
During welding, you can brace the joints to prevent the workpiece from slipping and ruining the joint’s angle. Alternatively, you can use woodblocks cut with a wood routing machine in place of the braces. Bracing using wood can be done by creating a scaffold-like system of supports that control the distortion. Remove these wood cuttings once you finish welding.
Bracing the weld section can also be done by constructing a jig. Before using jigs to brace, you should determine the amount of weld needed. The more the requirement of welds, the more the bracing.
3. Cleaning the Weld Joint
Welding steel requires you to work on a clean surface. No matter how clean your welding surface is, spatter formation is inevitable since one has to use filler materials during welding.
These weld spatters may still form even with the use of a fast and efficient welding machine. As you continue welding, the spatter becomes sharper or forms burrs, which can cause injuries to the welder.
Most welders prefer subjecting the welded stainless-steel wire through secondary processes. These processes include electropolishing or sanding. Note that selecting these secondary processes solely depends on the application of the custom metal form.
4. Distributing Heat from the Weld
Even distribution of heat involves the transmission of heat in equal measures throughout the welding process. Spreading the heat equally can be done by backstepping, staggering, or allowing the joint to cool down before welding it further. If heat is distributed unevenly, you are likely to end up with cracks and burns. You can use MIG welding robots to distribute heat evenly.
How to Weld Stainless Steel Using MIG
MIG welding of stainless steel requires the welder to continuously feed a solid electrode wire into the weld pool. You also need to provide a shielding gas to protect the weld from getting contaminated by impurities. Here are the steps to follow during MIG welding.
1. Torch Set-up
Begin with setting up the torch. This procedure involves setting up the filler wire from the MIG welder’s reel to the welding torch’s tip. Ensure only ¼ inch of your welding wire remains visible at the end of your torch. Then, activate the shielding gas to start the welding process.
2. Determination of the Correct Angle
Ensure the flame hits directly on the required area. You can achieve this precision by placing the torch at an angle of 30 degrees from the joint end.
Depending on the work you are doing, ensure you position yourself in a proper travel angle. A travel angle ranging between 5°-15° gives the best results when you hold your gun at 90°. Greater angles of 45° to 70° are desirable when dealing with T-joints and lap joints.
3. Pull up the Beads
Turn on the power and gently draw the weld bead towards the end area. Ensure you use moderate power and speed to avoid forming spatters.
Gas and Electrodes to Use for MIG Stainless Steel Welding
When MIG welding stainless steel, the correct choice of gas matters a lot, you can use pure Argon or a blend of Argon and other minor gases. You can also use a stainless gas mix such as the BOC’s Stain shield range of Helium, Carbon Dioxide, and Argon. These stainless gas mixes are essential to MIG weld stainless steel, which is more exotic. These exotic steel types include Hastelloy, Monel alloys, and Inconel.
MIG welding of stainless steel also requires the use of a gas with a slightly higher flow rate. The recommended flow rate should be around 14-16 liters per minute. Remember to engage your gas suppliers on the gas requirements before embarking on a particular project.
The most common electrode used to weld stainless steel is the ER308 L. When using this type of electrode, the gas type to use is C2. C2 consists of 2.5% Carbon Dioxide, 7.5% Argon, and 90% Helium. Note that the setting for stainless steel and several nickel-based alloys are very similar.
Be sure to ask your electrode supplier about the types of electrodes in stock before procuring. You can also procure an electrode wire and gas selection chart to guide you on the most plausible selection for your welding.
Welding stainless steel comes with its benefits and challenges, but as long as you factor those limitations into your process, the end result will be worth it. Perfecting your welding skills with this valuable and trendy material will save you time and money on the job. More importantly, it can produce a beautiful, professional result that will make your welding skills more marketable.