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Can You Weld Stainless to Mild Steel? All the Facts!

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TIG welding

Stainless and mild steel are the most used types of steel because of their high strength and corrosion resistance. The major difference is that stainless steel contains chromium, while mild steel has carbon as its alloy element. One question that arises is whether you can weld stainless to mild steel. Yes, welding the two and getting strong welds with MIG and TIG welding is possible.

Welding stainless to mild steel is not hard since the two metals have almost the same properties. You can get solid welds if you use the correct filler metal and follow the proper low heat procedure to ensure you don’t over-weld both parts.

Overwelding the stainless steel part makes the corrosion resistance drop. Besides, applying excess heat to the mild steel allows carbon migration into the weld metal. This results in a crack-sensitive and brittle final bead with reduced corrosion resistance.

This article looks at MIG and TIG welding, the best methods to weld stainless to mild steel, and the best welding rod and filler metal to use. You also learn some tips to apply when welding stainless to mild steel.


How to Weld Stainless to Mild Steel

Before You Begin: Get All the Necessary Equipment

Start by assembling everything you need for MIG and TIG welding. Some of the things you need are for the stainless to mild steel welding, while others are for your safety as you weld. Here are some of the things you require.

To weld stainless to mild steel, you will need:
  • Defensive gas
  • Clamps
  • MIG welder and rods
  • Angle grinder
  • Copper brush
Some of the safety gears required include:
  • A helmet
  • Knees wads and chaps
  • Hand gloves and safety eyeglasses
  • Safety Jacket and pant
  • Boots
  • Mask or ventilator

Set the Metals in Place

Before starting to MIG or TIG weld stainless to mild steel, you must be ready for the task. Set up the metals and the necessary welding tools. Set up the pieces correctly to have a seamless welding process.

  1. Wear protective gear, including welding boots, a full-sleeved shirt, insulated gloves, helmet, protective gloves, and respirator masks.
  2. Use protective gas to ensure that you use less energy and make the welds stronger. Combine about 98% argon and 2% carbon dioxide gas.
  3. Use the suitable filler metal recommended for welding stainless steel to mild steel.
  4. Before you begin welding, clean the base metal using the copper brush to get rid of impurities from the metals. Use acetone to remove any debris. You can also use an angle grinder or sandpaper for cleaning.
  5. Arrange the pieces of stainless and mild steel on a jigsaw casting bench and fixture before you begin to weld. Pin the metal firmly on the welding surface to ensure it doesn’t fall back as you weld.

The 4 Steps to MIG Weld Stainless to Mild Steel

This is the most common welding method to join stainless to mild steel. The method works perfectly if you have a large project and want to join large thicker steel. Here are the steps to follow.

  1. Thread your welding wire with your MIG machine reel, and then take the wire out using the torch tip. Extend the welding wire to about a quarter-inch outside the torch. When the wire is set, activate the gas, and begin to weld.
  2. As you weld, start from any joint end. You should hold the torch at a 30 degrees angle overhead the edge of the joint. Keep the torch sharp to make it hit your metals on the flame tip. When the heat gets high, pause and wait until the beads become controllable again.
  3. Move the torch slowly to fill the joint, ensuring that the torch is at a fixed angle. As you remove the torch, the flame moves the beads towards the joint, melting the surrounding metal.
  4. Allow the casting to cool. Allow the heat from the metal and torch to cool down. Avoid shaking the metal before cooling; otherwise, your joint will open.

The 6 Steps to TIG Weld Stainless to Mild Steel

If you have thin metals, TIG welding is the best option. The method also works perfectly for small projects. TIG welding machines have several settings, so you must use the suitable setting for your project. Another thing to note is that TIG welding tends to be a slower welding process. Regardless, follow the steps below:

  1. Insert a sharp tungsten rod into the torch. The wire features a diameter of around 1/16 inch, and you should place it in the mid of the metal cylinder. Allow the welding rod to move out a ¼ inch from the torch tip.
  2. After inserting the tungsten rod, turn DC on your welder. The TIG welding machine has two settings, i.e., the negative and positive. For negative settings, your machine should be labeled “DCEN.” Ensure you have the right setting to weld correctly.
  3. Your TIG welder is ready to start your torch with the right setting. Turn on the torch and hold its tip about an inch above your metal joint. Begin from any end of your joint and ensure you hold the torch at a 75-degree angle as you weld.
  4. TIG welder features a foot pedal, which you must press hard to heat the torch. Hold the torch and fill the joint until the metal melts. You should turn in the amperage on the panel and avoid using excess energy when melting the metal.
  5. The filler rod should be dabbed into the liquid metal when filling the joint. Hold the rod against your torch and move the liquid steel beads along the metal joint. Ensure the torch is fixed to ensure the filler does melt because of the heat.
  6. Allow cooling before you remove the torch and welded metal. Avoid moving the metal until the joint is strong.

Tips for Welding Stainless to Mild Steel

Here are a few things to remember as you weld stainless to mild steel:
  • You need to have all the required safety equipment to avoid injuries that may occur because of the heat involved in the welding process.
  • Ensure that the metal is clean before casting. With a dirty metal base, you will get weak joints.
  • You should put the metal pieces on a firm table. This is necessary because if the table is weak, it moves if a lot of pressure is applied as you place and weld the coarse metal.
  • Avoid holding the torch and metal empty-handed until the casting is ended. Besides, keep your torch hanging in a warm place before you place it on a flat surface.
  • While welding, keep the heat down because stainless steel warps with too much heat. So, ensure you set your amperage or heat output low to avert this problem.
  • Avoid thick filler wire or rods since they require a lot of heat that is not needed when welding stainless steel.
  • Have the right fit-up so that you can use the right amount of filler material and avoid filling gaps. Take your time to fine-tune your workplace setup to prevent poor appearance and warping.
  • Don’t move too slowly because this creates excess heat in your metal. So, have a quick travel speed as you weld.

Best Filler for Welding Stainless to Mild Steel

To get high-quality welds, you need to use filler metal 309. It has high chromium and nickel content that helps overcome the mild steel dilution issue. By using this filler, the weld metal deposited has great corrosion resistance. Besides, the 309 synthesis offers robust hot cracking resistance.

When welding different metals, the final beads contain 60% filler metal and a small amount of the two base metals. Since mild steel doesn’t contain nickel or chromium, a filler metal with a higher content than stainless steel is required.

Using filler metal like 310 with high nickel content will lead to beads with a high amount of nickel that can cause cracking.

On the other hand, using filler metal like 308, which has 10% nickel and 20% chromium, you get beads that can crack easily and with low corrosion resistance.

How to Choose the Best Stainless to Mild Steel Welding Rod

When choosing a stainless to mild steel welding rod, you need a high-quality rod that prevents hot cracking. The E309L-16 wiring rod is the best since it contains high chromium content and nickel to prevent cracking during welding.

The rod is corrosion-resistant and robust. Besides, it is also temperature-resistant and results in gorgeous beads. The “L” usually refers to alloy composition with a high amount of carbon. The carbon increases intergranular corrosion resistance.

You can also use E308 or E310 electrodes, which are cheaper, but the problem is that they produce low-quality joints.


Conclusion

It’s possible to weld stainless to mild steel using MIG or TIG welding methods. You can use MIG welding if you have thick metals to weld or if you have a large project. On the other hand, you can use TIG welding if you have thin metal pieces or a small project.

It’s not hard to weld stainless to mild steel because they share similar properties, making welding easy. For TIG welding, you need to know how to use the correct settings to get high-quality welds. As you weld, ensure you have all the necessary equipment and safety gear to prevent injuries.

To get great welds, use E309L-16 wiring rod to avoid cracking. Besides, ensure you use filler metal 309 to prevent corrosion and avoid cracking as you weld.

You may also be interested in: Can You Weld Black Pipe? All You Need to Know!


Featured Image Credit: senlektomyum, Shutterstock

Cameron Dekker
 

Cameron grew up in Allentown, Pennsylvania, a once-proud steel town on the Lehigh River, where he got a taste of TIG welding in his high school shop class. He holds certificates for Certified WeldingEducator (CWE) and Certified Resistance Welding Technician (CRWT) from the American Welding Institute. His interests include scuba diving, sculpture, and kayaking.