Making anything of stainless steel is a great thing to do for every DIY lover. It is a popular building material that is used everywhere. By making anything or attach any joint, welding is essential which is very challenging.
It is a complicated job for every beginner so before weld the steel, everyone needs to be practice to make themselves comfortable.
But there is nothing afraid of welding stainless steel if you have proper tools and knowledge. It is a risky job so maintain proper safety is the first priority.
How to Weld Stainless Steel
There are five types of stainless steel and you can weld them in four ways. To know about this, keep following the article.
About Stainless Steel
Stainless steel is made from iron with chromium 11%-30%. There are three categories of stainless steel such as Austenitic stainless steel, Martensitic stainless steel, and ferritic stainless steel. Welding those types of steel is complicated but if you have enough practice and control power, this complicated job will go long.
Preparation for Welding
You have to maintain different techniques for different stainless steel. Although the four ways will remain the same, just some small details will be added.
Selection Of Stainless Steel
Selecting the right stainless steel is a very important job for welding. Check for corrosion, tarnish, and oxidation resistance. Also check for strength, toughness, ductility, etc.
Austenitic Stainless Steel
It is a mostly used stainless steel that does not require preheating. You can weld it until the temperature reaches 350 degrees. You can also use a low-heat-input process and the base materials won’t be cracked easily.
Selecting the right austenitic stainless steel is important otherwise your steel will be cracked during welding. Choose fully austenitic such as 310, 320, and 330 steals with 304 grade.
Ferritic Stainless Steel
It is thick stainless steel and is mostly used in the automobile sector. You can do single-pass welding because of its thickness. Low heat input can also be used here. Using high heat is not good here as the steel will begin to expand and the possibility of the crack is high. To welding this steel, the filler metal, and Cr level should be matched to the base alloy. The preheating temperature should be 300_450 F.
It is not hardenable when it gets heat by welding. Ferritic stainless has low carbon content so it is nonhardenable.
Martensitic Stainless Steel
It is a medium type steel and requires an accurate preheat temperature otherwise the steel will be cracked. It is mostly used in casting mills with 400 to 600 degrees Fahrenheit preheating. The steel takes more time to cool and needs to match the filler metal. It is similar to ferritic but it has higher carbon than ferritic.
Methods For Stainless Steel Welding
You can use 4 types of welding on stainless steel. But before that, clean the steel and prepare it to prevent rust. If you weld carbon steel at the same place before, clean the area properly because the carbon particle will harm the stainless steel. Also, do not forget to match the filler material.
Which welding method you should apply on stainless steel depends on the thickness, time, and product condition.
Clean The Joint
Before welding, it is mandatory to clean the joint area. Remove all the moisture, oil, paints, and check for leakage. Gather an arc plasma cutter for welding as you can not apply flame cut on stainless steel. Use new brushes and tools for cleaning. Old brushes could react with stainless steel. Stainless steel wire brushes are best for cleaning. Do not use those brushes in other works.
Selection Of Welding Process
Shielded Metal Arc Welding
It is the lowest cost of welding used to weld joints in thicknesses. You should maintain the electrode coating and stored in low hydrogen electrodes. Also, the size should be solid and cored wire. The thickness could be 0.05 inches.
Submerged Arc Welding
It is also used to join thick sections and most of the steels are austenitic with metal type 310 or 330. This welding requires direct current, but it is also can be used in alternative current for good arc stability. Select the flux and welding condition properly. Also, use the proper voltage otherwise the flux could be melted. Use special procedure and flux so that the metal could respond when you apply heat.
Gas Metal Arc Welding
This welding is used for long joints in thick material. It is best when you are working with a large number of parts. The solid or metal-cored wire will help to remove a little slag and prevent short circuiting. It also has a wide range of deposition rates and a joint section of fewer than 0.25 inches.
Flux Cored Arc Welding
It is also used with solid wire, metalcore, and flux core wire. The welding has overcoated electrodes so you do not have to stop welding to change the electrodes.
Gas Tungsten Arc Welding
You can use it in manual and automatic mode and weld it up to 0.25 thickness.
After deciding the design and welding process, it is time to start the welding. Clean the edges, filler material, and any rough surface. Check for the distortion and sensitization on the area where you are going to weld.
Welding with the Shielded Metal Arc Process
Coat the puddle and use a short arc. Weld horizontally so the electrode could be dragged in the base metal. Use a flat surface and fill the crater quickly so it won’t be cracked. When the first weld is done, clean the slag before start welding again. Penetrate a little for the groove butt joint. Use the electrodeless than 5/32″. A-DC electrode is better for the thick plate, weld vertical up. In a thin plate, use vertical down.
Always weld in low current with sufficient penetration so that you could apply heat input and use stringer beads at a slower speed. Cool the stainless steel rapidly and use chill and baking bar with the steel.
Joining Another Steel With Stainless Steel
When you are joining stainless and other mild steel, the other steel will be buttered. The mild steel will be coated with stainless steel to complete the joint.
Use the EXXX-16 electrode power source as it is high enough for a larger diameter. The parameter should be 18 gauge to 1/2 inch so that you can weld the tee, butt, and lap joints easily.
Welding with the Submerged Arc Processes
This welding technique uses higher heat input so it will submerge the arc welding. Select the proper flux otherwise the silicon content will be getting higher. For the square groove butt joint, single-pass welds are better. You can also apply two-pass welds if the steel is 5/8 inch thick. Prepare the edge and make a good penetration before making the joint.
If you weld a single V groove joint, a single pass butt weld is enough to 5/16 inch thickness. But if the thickness is 5/8 inch, two pass welds are needed. Apply for the first pass on the V joint then apply for the finishing pass on the flat side of the joint. For double V groove joint, weld 3/4 inch and 304 plates.
Always weld in a flat position, it will make the result in the best bead contour easy. Some methods of starting the weld are,
In this method, the wire is used in the work. It has a carriage so when the wire will touch the work, it will not fuse.
Here, the wire will be toward the work and it has a flux cover. When you start the weld, the wire will automatically retract and start doing the reverse. Although this process is not good for light gauge stainless steel.
Cladding with Submerge Arc
In this process, you will get limiter wire speed so it is not desirable.
Welding with The Gas Metal Arc Process
You can weld the stainless steel with a gas metal arc process, but you will need copper backup strips when you are welded 1/16 inch thick steel. Stop the air supply when welding at the puddle. Shield the underside with an inert gas. If the thickness is less than 1/16 inch, use high current when the spray arc is transferred. Use backup strips so the weld metal drop will not be wasted.
When using a semi-automatic gun ¼ inch thick plate, use the gun in the direction of the joint and do back and forth. You can also use a short digging spray arc. Keep the wire as short as possible. Use backhand weld because it is easy and neat rather than fillet welds. But in butt welds, use forehand welds.
Welding with The Gas Tungsten Arc Process
You can use this welding process in all types of stainless steel. It is a more stable arc and used in higher currents. Argon is used here for shielding gas because you can change the flow rates as the voltage is less. So you can weld thin sheet. The filler materials are used here with solid wire. Do not use high frequency, it will only be needed when starting the arc.
The shielding gas is argon, hydrogen, nitrogen, and helium so it is very strong welding. tungsten and base metal creates an arc between them with the current. Use the right size of the tungsten rod otherwise big diameter of rods can create problems while welding. Decide the rod size with a thickness of stainless steel.
Which Welding is Best For Stainless Steel?
It is not simply that you think. First of all, you have to decide what type of result you want to get. Different welding processes will give a different result. To know which welding process is best for stainless, consider some things such as welders skill, aesthetics condition, the thickness of the metal, etc. if you want to do artistry, TIG welding is best. But if you need the speed and efficiency, MIG is best.
How to Choose The Right Grade?
In austenitic, the best chromium-nickel grades are 302, 303, 303Se, 304, 308-310, 316, 317, 321, 347. In martensitic, the best chromium grades are 410, 414, 416, 416Se, 42D, 431, 440 A B C. In ferritic the best chromium grades are 430, 430F, 430FSe, 446.