Three Maples
01-05-2010, 11:48 AM
Lap Joint TIG Welding Stainless Steel Sheet Metal
First off I am not a welder just another back yard project bum that has struggled to weld stainless with TIG, Tungsten Inert Gas, or properly called Gas Tungsten-arc Welding GTAW,TIG seems easier to say.
Let’s say you are welding 20 gage stainless 304 mill grade, if you read McMaster Carr it says, “Type 304 is commonly used in chemical and food processing equipment, gutters, and flashing. It has good weldability, formablilty and temperature resistance.” I guess they have never tried to build a 20 gage stainless syrup pan.
The basics are preparation, heat, heat sink, and practice practice practice. Did I mention practice? TIG welding is a lot of little things that are accumulative, so each small thing must be addressed. This must be your mind set no hurry be meticulous.
First preparation, let’s start with the lowly ground clamp; most people forget the ground clamp as they work to get the torch tuned up. We are working in very low current or amperage settings and any loss in the ground will cause erratic torch behavior. Take the clamp apart and wire brush all connections. You may be surprised to find corrosion especially where the copper meets the stainless of the clamp. Brush up the clamp itself and brush where it will attach to the work. Clamp the ground to the work not the bench. We want a perfect as possible ground connection. Now move to the torch you will need to use .040 tungsten I would suggest 2%thorium. (There are some warnings that the thorium is radioactive or causes radiation. So that is my disclaimer there may be radiation involved in this process.) Where were we oh ya. The electrode needs to be sharpened to a pencil point and it is recommended that the sharpening be so that the abrasive lines are in the direction of the electrode. In other words do not hold the electrode sideways to the wheel and spin it, hold it straight to the wheel so that it spins down on it. I use a vertical sanding belt, some suggest a diamond wheel is best, I tried it but diamonds are too expensive. You must match the cup, collet, and nozzle to the electrode. Your welding supply can help you there. Set the electrode out where you can see it. Most books tell you to set the electrode 2 ½ times the diameter, well, make it as close as possible but you need to see it. Around ¼ inch is ok experiment see what works for you. Prepare your helmet; remove and clean the lenses you must see the puddle clearly. For thin stainless I use a # 8 lens. NOTE: DO NOT EXCEDE 50 AMPS ON A #8 LENS. IF THE ARKS SEEMS BRIGHT IT IS AND YOU MUST GO TO A HEAVIER LENS TAKE NO CHANCES NO WELD IS WORTH TAKING A CHANCE ON YOUR SIGHT. Prepare your work; all joints must be tight fit with no slag, brush clean the stainless. Preparing your welder; it is my belief if you want professional results buy the tools the pros use. A cheap TIG may well work but it will be part of the struggle. Set up the welder for 50 amps if you have a foot petal something less if you do not. Set aprox. 15 CFH strait Argon gas. Your heat should be just enough to melt a pool and blend in the metal; we will not be using a filler rod today that is a whole nother thing.
Now for heat, Stainless hates heat, it warps, burns thru and is generally a wimp when it comes to heat. So we want to heat quickly and get out. Some use higher heat and move quickly which is great if you are good at starting and moving, but if you are reading this with interest I would bet you are not ready for that. Unless you have mastered this I say less heat with good sinks.
Heat sinks; being creative with heat sinks will get you good results while you are mastering TIG. Copper is the best heat sink because is not only a great conductor of heat it will not easily weld into stainless. Other metals like steel and aluminum also have their place. Let’s talk about the lap joint on 20 gage stainless. The problem is in order to get the base hot enough to form a pool ( The pool will appear very bright like a polished chrome when it is at the proper point to blend in the overlap.) the lap will seem to run away from the torch. The way to control differential heat is to use heat sink. Now if we put a copper heat sink under the base metal and a copper heat on the lap metal we are right back to our problem. But, what if we put steel which is an ok conductor of heat under the base and laid a copper sync on the lap? Now we have a very good conductor on the lap and an ok under. With a little practice you will see that the lap will try to run away and the copper will stop the pool dead and it will blend. This type of creative heat sink has lots of other applications just try to think like a couple hot pieces of stainless.
Last thing is hold your torch like an aristocrat holding a teacup. You cannot hold the torch like a golf club. Practice holding it with the hose draped over your arm, the thumb and forefinger on the body and little finger extended. The little finger is the base and must always be touching the work. TIG is about finesse and control unless you are steady as a surgeon while in the dark you must develop an anchor for your hand, for me it is the pinky. Whenever possible you should use both hands.
Always clam your work. Clamp in the heat sink. By the way for clamping on the lap sink, 1/8 in copper will do clamped about 1/16 in back from the edge.
Lastly you must stay very close with the tip of the torch I mean very close developing forward back circular and whatever works for you. Books will show you the proper angles to use. When you touch the tip of the electrode to the work stop and reshape it yes every time. This is an incentive to learn to stay close and not touch.
Really lastly; practice until you are comfortable before you touch the arc to you project. TIG is the most difficult welding you will ever do so do not get discouraged and hurry thru the most import part and that is practice, like a concert pianist you must feel it when it is right. It is best to start sitting down at your bench as comfortable as you can be.
Now strike your torch heat the base to puddle swing over and watch the top run to the copper and blend in.
First off I am not a welder just another back yard project bum that has struggled to weld stainless with TIG, Tungsten Inert Gas, or properly called Gas Tungsten-arc Welding GTAW,TIG seems easier to say.
Let’s say you are welding 20 gage stainless 304 mill grade, if you read McMaster Carr it says, “Type 304 is commonly used in chemical and food processing equipment, gutters, and flashing. It has good weldability, formablilty and temperature resistance.” I guess they have never tried to build a 20 gage stainless syrup pan.
The basics are preparation, heat, heat sink, and practice practice practice. Did I mention practice? TIG welding is a lot of little things that are accumulative, so each small thing must be addressed. This must be your mind set no hurry be meticulous.
First preparation, let’s start with the lowly ground clamp; most people forget the ground clamp as they work to get the torch tuned up. We are working in very low current or amperage settings and any loss in the ground will cause erratic torch behavior. Take the clamp apart and wire brush all connections. You may be surprised to find corrosion especially where the copper meets the stainless of the clamp. Brush up the clamp itself and brush where it will attach to the work. Clamp the ground to the work not the bench. We want a perfect as possible ground connection. Now move to the torch you will need to use .040 tungsten I would suggest 2%thorium. (There are some warnings that the thorium is radioactive or causes radiation. So that is my disclaimer there may be radiation involved in this process.) Where were we oh ya. The electrode needs to be sharpened to a pencil point and it is recommended that the sharpening be so that the abrasive lines are in the direction of the electrode. In other words do not hold the electrode sideways to the wheel and spin it, hold it straight to the wheel so that it spins down on it. I use a vertical sanding belt, some suggest a diamond wheel is best, I tried it but diamonds are too expensive. You must match the cup, collet, and nozzle to the electrode. Your welding supply can help you there. Set the electrode out where you can see it. Most books tell you to set the electrode 2 ½ times the diameter, well, make it as close as possible but you need to see it. Around ¼ inch is ok experiment see what works for you. Prepare your helmet; remove and clean the lenses you must see the puddle clearly. For thin stainless I use a # 8 lens. NOTE: DO NOT EXCEDE 50 AMPS ON A #8 LENS. IF THE ARKS SEEMS BRIGHT IT IS AND YOU MUST GO TO A HEAVIER LENS TAKE NO CHANCES NO WELD IS WORTH TAKING A CHANCE ON YOUR SIGHT. Prepare your work; all joints must be tight fit with no slag, brush clean the stainless. Preparing your welder; it is my belief if you want professional results buy the tools the pros use. A cheap TIG may well work but it will be part of the struggle. Set up the welder for 50 amps if you have a foot petal something less if you do not. Set aprox. 15 CFH strait Argon gas. Your heat should be just enough to melt a pool and blend in the metal; we will not be using a filler rod today that is a whole nother thing.
Now for heat, Stainless hates heat, it warps, burns thru and is generally a wimp when it comes to heat. So we want to heat quickly and get out. Some use higher heat and move quickly which is great if you are good at starting and moving, but if you are reading this with interest I would bet you are not ready for that. Unless you have mastered this I say less heat with good sinks.
Heat sinks; being creative with heat sinks will get you good results while you are mastering TIG. Copper is the best heat sink because is not only a great conductor of heat it will not easily weld into stainless. Other metals like steel and aluminum also have their place. Let’s talk about the lap joint on 20 gage stainless. The problem is in order to get the base hot enough to form a pool ( The pool will appear very bright like a polished chrome when it is at the proper point to blend in the overlap.) the lap will seem to run away from the torch. The way to control differential heat is to use heat sink. Now if we put a copper heat sink under the base metal and a copper heat on the lap metal we are right back to our problem. But, what if we put steel which is an ok conductor of heat under the base and laid a copper sync on the lap? Now we have a very good conductor on the lap and an ok under. With a little practice you will see that the lap will try to run away and the copper will stop the pool dead and it will blend. This type of creative heat sink has lots of other applications just try to think like a couple hot pieces of stainless.
Last thing is hold your torch like an aristocrat holding a teacup. You cannot hold the torch like a golf club. Practice holding it with the hose draped over your arm, the thumb and forefinger on the body and little finger extended. The little finger is the base and must always be touching the work. TIG is about finesse and control unless you are steady as a surgeon while in the dark you must develop an anchor for your hand, for me it is the pinky. Whenever possible you should use both hands.
Always clam your work. Clamp in the heat sink. By the way for clamping on the lap sink, 1/8 in copper will do clamped about 1/16 in back from the edge.
Lastly you must stay very close with the tip of the torch I mean very close developing forward back circular and whatever works for you. Books will show you the proper angles to use. When you touch the tip of the electrode to the work stop and reshape it yes every time. This is an incentive to learn to stay close and not touch.
Really lastly; practice until you are comfortable before you touch the arc to you project. TIG is the most difficult welding you will ever do so do not get discouraged and hurry thru the most import part and that is practice, like a concert pianist you must feel it when it is right. It is best to start sitting down at your bench as comfortable as you can be.
Now strike your torch heat the base to puddle swing over and watch the top run to the copper and blend in.