The welding of stainless steel is fundamentally different from that of other materials. The difference starts with the unique chemical composition of stainless steel.
Some time ago, the engineering team of EASIAHOME was asked by a customer whether stainless steel nuts could be welded to carbon steel wire. The short answer is “Yes you can, but you probably don’t want to.” In most cases, if you need a corrosion-resistant form of wire, it is best to use entirely stainless steel wire instead of mixing and matching metal.
What is stainless Steel?
The welding of stainless steel is fundamentally different from that of other materials. The difference starts with the unique chemical composition of stainless steel. Like other steels, stainless steel is an alloy of iron and carbon. Stainless steel, however, differs in that it contains at least 10.5 percent chromium, an element that makes the resulting alloy resistant to corrosion. Various forms of stainless steel, including stainless steel sheet, stainless steel plate, stainless steel tube and stainless steel bar.
There are five types of stainless steel, but only three of them are usually found in the manufacturing shop – austenitic, martensitic and ferritic. The most common is austenite. Martensitic stainless steel is used for hard surface applications. Ferritic steel is the cheapest option and is used the most in consumer products. Each of these types of steel is classified according to its microstructure, which affects its ductility and strength.
The microstructure of steel depends on its chemical composition. For example, austenitic steel contains 16-26% chromium (Cr) and 8-22% nickel (Ni). The Cr content of martensitic steel is in the range of 11-28%. Ferritic steel contains 12-18% Cr. Therefore, the material welded to each steel must match the composition of that steel.
Stainless steel welding VS.Carbon steel welding
Stainless steel welding is more complex than carbon steel welding. First, stainless steel effectively holds heat, causing it to warp when exposed to the high temperatures generated by welding. Stainless steel can also warp or crack during cooling after being heated by a welder. Even if a piece of stainless steel does not crack or deform after a poor weld, it will almost always show scratches and blemishes. Each stainless steel presents unique challenges to the welder. Austenitic steel may crack if high heat is applied or if concave or flat welding is performed. Martensitic steel will crack if not preheated properly. With temperatures as low as 300 between the top layers, ferritic steel will lose strength unless heated with a low heat input.
The key to successful welding of stainless steel is to obtain the correct filling material. The grade of the filling material needs to match the grade of the base material in order to obtain good welding results. So when welding stainless steel to other metals, other types of welding other than resistance welding should be considered. For example, MIG and TIG welds are the preferred types for welding stainless steel together with carbon steel. When combining different metals together, such as welding stainless steel to carbon steel, filler materials are needed to combine the two metals. In MIG welding, a continuous feed of electrode wires is fused into the weld, allowing two different metals to join without being heated to the melting point. When welding stainless steel using the MIG process, filler must be used because the melting points of two different metals can be very different.
For example, if one metal overheats to the melting point of the other, it can cause stress cracking and microcracks. It is possible to weld two different metals, but it is a very difficult process and has many complications.
Materials and equipment for welding stainless steel
Stainless steel can be rod welded, shielded metal arc welding (MIG) or tungsten gas shielded welding (TIG). The best choice depends on what you are trying to achieve, as each process produces different results. You can weld stainless steel with a stick, but you probably shouldn’t.
There are other, better options. MIG welders form the strongest, most reliable welds with stainless steel. This is an especially good option if you are welding something thicker. TIG welders may be the right choice for thinner materials and welds that require aesthetics and precision. Despite this, TIG welding is still a tough weld unless you have the experience and time to do it properly. Inexperienced TIG welders may leave unfortunate marks or blemishes on stainless steel.
Although the resulting welds are not very fine, MIG machines are usually the best choice for welding stainless steel. Choose a machine with a torch and sample wire. Most machines come with a gun, but if you’re looking for something that produces more accurate welds, you can upgrade your gun.
You will also need to pick up some of the torch heads so that they can be replaced as they wear out. To protect the torch, you can purchase a liner, which allows you to quickly and efficiently switch between different types of wire.
For the wire itself, you must use a suitable stainless steel wire, which is usually 0.030 “in diameter, but 0.035” to 0.045 “wires may work for thicker workpieces. Since you need to check the temperature when welding stainless steel to avoid performance problems, you need to have a temperature tracking device on hand.
You can use a traditional stick, but keep in mind that it has a limited range. Other options include electronic infrared thermometers and electronic surface temperature probes. You’ll also need protective gas, which may require a mixture of 7.5 percent argon, 90 percent helium, and 2.5 percent carbon dioxide.
Then, you’ll need to add a brush for metal scraping and cleaning, a tool that can help you prepare your workspace and ultimately help you achieve more durable welds.
Finally ready to weld, use a metal brush to remove all dust, dirt, oil, grease or water from the station. You can also help prevent warping and cracking by clamping a piece of brass or copper behind the weld. This trick helps absorb heat and keep the stainless steel warm enough. Keep a separate set of stainless steel welding tools.
Once your tools come into contact with carbon steel, they can pick up carbon residue. This residue will be transferred to the stainless steel during the welding process, which will eventually cause the product to rust.
In order to ensure the best results when welding, we summarized the following tips:
1. You are required to have all necessary safety equipment to avoid possible injuries due to heat during welding.
2. Make sure the metal is clean before casting. Using a dirty metal base will weaken your joint.
3. You should put the metal pieces on a strong table. This is necessary because if the table is thin and a lot of pressure is applied when placing and welding the coarse metal, the table will move.
4 Avoid holding torches and metal with empty hands until the casting is over. Also, hang your flashlight in a warm place before placing it on a flat surface.
5. When welding, please keep low temperature, because stainless steel will be deformed by too much heat. Therefore, be sure to set the amperage or heat output low to avoid this problem.
6. Avoid using coarse-filled wires or rods, as they require a lot of heat, which is not needed when welding stainless steel.
7. Assemble correctly so that you can use the right amount of filling material and avoid filling gaps. Take the time to fine-tune your workplace Settings to prevent bad looks and warping.
8. Don’t move too slowly, as this creates too much heat in the metal. Therefore, when welding to have a fast speed of travel.
9. Keep your work area clean, safe, and well ventilated.
10. Although welding stainless steel is a little more complicated than other welds, it can be done. You can even weld stainless steel to mild steel. Using the right equipment, controlling the temperature, and obtaining the right filler material can result in a strong and durable weld.
Steps for MIG/TIG
MIG 4 steps for welding stainless steel to mild steel
1. Run your MIG machine reel through the wire and remove the wire using the tip of the torch. Extend the wire about a quarter inch outside the torch. Once the wires are set up, start the gas and then start welding.
2. When welding, start at any joint end. You should hold the flashlight at a 30 degree Angle above the edge of the joint. Keep the torch sharp so that it hits the metal at the tip of the flame. When the heat gets high, pause and wait for the beads to become manageable again.
3. Move the torch slowly to fill the joint, ensuring that the torch is at a fixed Angle. When you remove the torch, the flame moves the bead toward the joint, melting the surrounding metal.
4. Let the casting cool. Let the heat from the metal and the torch cool down. Avoid shaking the metal before cooling. Otherwise, your joint will open.
TIG Welding stainless steel and mild steel in 6 steps
If you have thin metal, TIG welding is the best choice. This approach also works for small projects. TIG welders come in a variety of Settings, so you must use the appropriate Settings for your project. Another thing to note is that TIG welding tends to be a slower welding process. In any case, follow these steps:
1. Insert a sharp tungsten stick into the flashlight. The wire should be about 1/16 inch in diameter, and you should place it in the middle of the metal cylinder. Move the electrode about ¼ inch out of the nozzle of the torch.
2. After inserting the tungsten rod, turn on the direct current of the welder. TIG welders have two Settings, namely negative and positive electrode. For negative Settings, your machine should be labeled “DCEN”. Make sure you have the correct Settings to weld properly.
3. Your TIG welder is ready to start the torch with the correct setting. Turn on the flashlight and hold its tip about an inch above the metal joint. Start at either end of the joint and be sure to hold the torch at a 75 degree Angle while welding.
4.TIG welder is equipped with foot pedal, you must press hard to heat the torch. Hold the torch and fill the joint until the metal melts. You should input the amperage on the panel and avoid using too much energy when melting the metal.
5. When filling seams, tap the filling rod into the liquid metal. Hold the rod against the flashlight and move the liquid steel ball along the metal joint. Ensure that the cutting torch is fixed to ensure that the packing does not melt due to heat.
6. Allow to cool before removing the cutting torch and welding the metal. Avoid moving metal until the joint is secure.
Stainless steel can be welded to mild steel using MIG or TIG welding methods. MIG welding can be used if you are welding thick metals or have large projects. On the other hand, if you have thin metal pieces or small projects, you can use TIG welding. Welding stainless steel to mild steel is not difficult because they have similar properties that make welding easy.
For TIG welding, you need to know how to use the correct Settings to get a high quality weld. When welding, make sure you have all necessary equipment and safety devices to prevent injury. For good welding results, use E309L-16 wiring strips to avoid cracking. Also, be sure to use filler metal 309 to prevent corrosion and avoid cracking during welding.