Gas Purging Explained

Transcript

- Hi and welcome to today's gold webinar, this revolves around purging. So what is purging you ask? Well purging is the process of filling the inside of a vessel with a, I guess a non reactive gas. In this case it's argon so when we're welding materials, we put a lot of effort into shielding the tungsten and the resulting weld pool but what we need to do is also put that effort into controlling what's happening on the back side of our weld, and that is the process of purging. So in short, I guess purging removes oxygen and nitrogen from the back side of the weld which reacts with molten metal. This fends off any carbide precipitation that would result from this reaction.

This carbide precipitation is sometimes called sugaring and presents itself as lumpy grey looking weld that opens up our weld to premature failure. So today we're going to look at how we can eliminate that precipitation and present a really nice weld on the inside of our tubing. So usually we wouldn't see in here but it is an important aspect of motorsports for both flow and longevity of our welds. We don't want any cracks coming from the inside out on any of our components so purging is a very important subject. Now if you guys are watching live then jump in and ask any questions in our chat and I'll get to those at the end.

So if you have any questions on purging or if you feel that I've missed anything or if there's any information that you'd like to know then jump in, ask your questions and we'll get into that. So today we're going to look at purging, we're going to look at the ways that which we can eliminate this precipitation from happening inside our tubing, we're going to show you some tips and tricks on how to do that and then we'll finish up with a display and a demonstration on a piece of 304 stainless steel and show you how it all comes together in practice. So material, when we talk about materials in motorsport, we talk about mild steel, chromoly, titanium, stainless steel, all of these are welded with a DC TIG or can be MIG welded but for the case of purging we are focusing on TIG welding today. So these materials, not all of them require purging and this is something that I guess you have to look at case by case. All of mild steel, mild steel is not a reactive material and it doesn't react with the atmosphere all that much so it doesn't require purging.

So this means the roll cages, suspension arms and a whole bunch of different things that are made out of mild steel do not require purging, they just require the molten weld pool to be covered by the tungsten, or sorry by the cup that surrounds the tungsten and shields that weld pool. Moving on we have chromoly, chromoly does not need to be purged. This again is a higher carbon mild steel with a few different elements such as manganese but these do not present severe reactions that cause this precipitation so there's really no need for any of that, that purging in chromoly. So chromoly roll cages, suspension arms, all of those items again in chassis fabrication do not need argon on the inside of the tubing which again saves a bunch of cash because the argon isn't cheap, but we'll get to that later. Moving onto stainless, so remember mild steel chromoly does not need the purging process but stainless in some applications will.

This is particularly important in exhausts and high stress components. Stainless steel is a fairly reactive metal, it's not one of our most reactive metals but it does have a bunch of elements that do not like to be heated and left out to atmosphere. This does cause this sugaring and that's what we're trying to get rid of. So in the case of an exhaust, what we want to do is we want to both have a good looking outside weld that's nice and smooth but we want the same on the inside. Now if we didn't put argon on the inside it would be like welding without using argon on our TIG and we all know if you've left the bottle off and you've attempted to do a weld, then it just turns into a real mess and that's what's happening inside your tube.

So for exhausts I would recommend, and we'll get to basically a list of things that we recommend and we don't recommend later but if you can afford it and if you're working on some special projects or you're building a header that will be put through a lot of performance, I guess tests on the racetrack then it's a really good idea to purge the inside because it will result in a stronger weld. It will result in better flow and it will result in that part lasting the test of time. Usually if you don't purge something then it might be fine but what we're actually doing is introducing cracks into the material if it's not purged from the inside out and then as our vehicles go through the rigorous tests on the racetrack, then carbon and all the other things inside the exhaust basically build up around this sugaring and can eat their way inside out and end up cracking the weld and this is also frequently seen in stress fractures and stuff like that as well. Where an exhaust has to go through a lot of movement. This is also something that happens during the heating and cooling cycle where the material expands quickly and then cools which means it expands and contracts.

So it's quite important in stainless but not completely necessary. Another material is titanium and this is where the purging process really shines. Titanium is a very strong, very thin, very reactive metal and it requires complete argon coverage. Now this means that we can never weld titanium without the use of purging with argon gas. So we need complete coverage on this weld and what this means is that we need to always purge with our titanium, especially on exhausts and other components where you would usually find titanium in our racecars.

Aluminium, not so, aluminium is not a reactive metal and as we heat it, it does not have these side effects so we don't need to purge aluminium. And then other metals like inconel and the more I guess high end motorsport metals you would always need to purge so in a perfect world we could all have our hands inside an argon tank and be able to put our parts in there and weld them up to make sure that there's no contaminants that are sitting around or flying around in the atmosphere to get into our weld. So this is oxygen and nitrogen and a bunch of other things that are actually in the atmosphere that cause this reaction to our metals. So how do we fend this off? This is basically let's start at the bottle. So argon gas is used, you should not be using anything other than argon gas to purge your metals.

So usually we'll have an argon bottle that is feeding our TIG and this is 100% argon and what I've got set up here is this is a dual flow meter so basically we're using one side to feed our TIG and then we're using the other side to basically feed a hose and have some adaptability to be able to flow gas into our part at a set litres per minute rate. We'll get to that rate in a minute but this is a pretty important part of the factor. We can have another bottle, it can be set up with a separate flow gauge and we can pump argon from that into our part. We just have to make sure that it's flowing at the right rate and we've got both bottles turned on prior to going. The process of purging the tube is none other than basically covering up both ends.

Now this can be done via the use of tape, and I've got some here in fact. So basically if we were to purge a piece of tube, the idea is to cover both ends and inlet the gas into one and let it out the other. So as we're inputting argon, we want this argon to be filling up the tube and then the purging process will be exiting the gases that we don't want inside the pipe and these will be anything that's in the atmosphere. So if we cover up both ends of the tube, keeping in mind that we'll need to put some holes in one end to release the pressure. Remembering that pressure and welding do not mix because as we create a molten weld pool, that will be the softest point of our part.

And the gases can start blowing out in that area. So then we can input our hose in here which will input the argon. So if I was welding in the centre here, we could take this in and cover up the tube and this will give us a nice inlet of gas into the tube. And I'm not going to get too technical here 'cause I'm not going to use this process, it's really just an explanation. So really the basis is we just want to again seal both ends.

This is probably the lowest cost option of purging that we have. So you don't need any special tools to do this, you basically have your argon tube into the part and if we were welding somewhere in the middle here and then we need a relief in the tape at the end. I usually just grab a bit of filler wire, punch a series of holes so that our argon can be released and the gases inside the pipe can be released and eventually what we'll see is the whole inside of the tube being filled with argon and that's really what we're trying to do, we're trying to release all of the gases. So argon is heavier than atmosphere so we always try and use the pipe so that our inlet is at the lower end and then our outlet is up the top. So all of our argon can sit down in the bottom here and then slowly release all of the atmosphere which causes this reaction and precipitation inside the pipe to leave.

So that is the taping method and this again is quite simple, it only works if you're welding a fair way away from the tape. Obviously it's not going to react well to heat so this can be ideal for a larger exhaust or a set of headers or something that you have muliple holes in, you can use the tape to cover them all up, just make sure it's a tape that doesn't leave too much residue on your part as you may get pretty sick and tired of having to clean it all the time if it is leaving the residue on there. So this is a part that we'll weld up soon so I'll make sure that there is no residue on because I don't want to have that included into my part. So another thing to note is that whenever we're TIG welding we want to prepare the tube. So before we cover everything up we want it nice and clean on the inside and we need to make sure that all of the contaminants that might be in there such as cutting fluids or swarf are cleaned out.

This is pretty normal for most TIG welding but if we're purging then we basically want to remove all of these because we're going to the extra effort of purging, we want to remove all contaminants inside that tube. Alright so a little bit of a better way to do this and something that's more professional but does cost a little more is using these purge plugs. So what these are made of is silicon and this is actually heat resistant so what these are, are nice and soft purge plugs and these allow us to cap the ends of tune quite simply, jammed in there and then it has a little hole that we can then easily plug in our argon line from our gas bottle, straight in and seal up the tube. One thing to make sure is that these are a really nice fit because if they're not then they can pop out mid way and if you've got your mask down then this can lead to some pretty awful welds on the inside and obviously that's what we're trying to get away from. So quite important that they're a nice fit.

They are available from 4 inches all the way down to I think 1.5 or even smaller actually but this is a really good kit for motorsports, I have 4 inches all the way down to 1.5 inches in half inch increments so obviously if you've got an odd size then one of these is going to fit it. One thing to really focus on inside these is they use this metal gauze. Now you might see that that is quite familiar so a TIG cup has this similar metal gauze that basically clouds and creates a nice laminar flow of argon gas. So if we used our previous method of putting the hose in and taping it into our tube we're creating quite a dense flow of gas but it may not be clouding and sitting around the areas where we need it. One great thing about these is as the gas is entering the tube it's getting broken up into a cloud and this has a greater effect and covers more area and uses less gas and creates a better effect on the inside of our tube for our welds.

We can use aluminium foil or other items to be able to facilitate this but these plugs are really really good and one thing that I will note is when we're working on parts that are quite close to the actual plug, it can be quite important to have these set up and because this is only say 10 mm away from the weld, having them heat proof means that we can really just get in there, plug it up and weld quite close to our plugs and they won't burn away or we won't have to worry about melting the tape or anything that we've used to cover these up. If you do use aluminium foil, be careful, aluminum has a very low melting point and can actually start melting onto our parts. I've actually done this before and I didn't realise how little heat actually takes to melt aluminium foil so even if you're looking to cover up some bungs or something then make sure that you've got something that creates enough coverage of the part and also fends off any heat that may be near it. One thing that is quite common in the industry is for people to machine up their own bungs. Prior to getting this kit, I machined up this little aluminium bung which has a hose attached to it.

This can be swapped to either side, this is for 1.5 inch tube and this is for 1.75 inch tube. So that's with a 1.6 mm radius and, sorry 1.6 mm wall thickness and this is something that I used quite often, really the inlet is the important part and the exit is not so important, we can just use tape with a bunch of holes in it to exit the gas. So those are the methods that are most used in motorsport for the purging process. I guess what we need to talk about now is how much gas and how long we input this into our parts for. So I've got here my low meter set up and usually I would set a gas lens like this at around 15 to 17 litres per minute to get enough flow and this is probably too much for purging.

What I usually like to do is use 5-10 litres per minute on my purge and because I'm using these plugs and it creates quite a nice cloud inside the part, we can leave it for 2-3 minutes prior to welding depending on the size of it. And this is very difficult to gauge. We can work out how many litres we're actually pumping into the part by time and it is really a bit of an unknown because we can't see inside there, we don't know how well that argon is actually flowing in and filling the cavity, we don't know how much oxygen has been pumped out of there so usually depending on the size of a part, if I was to put a weld on the middle of this, I'd plug it up, run about 5-10 litres per minute for at least 30-40 seconds to a minute and then turn my flow down to about 5 litres per minute and pretty much just let that rest until I was ready to weld. 1.5 - 2 minutes would probably be ample for a part this size. If you were going to do a header, then you probably want to wait around almost 10 to 15 minutes just to make sure that that part is flooded with argon on the inside and remember argon is heavier than oxygen and atmosphere so if we keep our inlet at the lowest point and our outlets at the top point then this will give the oxygen a nice path for evacuation.

Basically that's our flow meter setup, we've got some examples here which I just knocked up 10 minutes ago, they're probably still warm but we spoke before about stainless steel and using purging on headers and this is a quick example that I set up on the bench here, I basically had this small section of stainless purging for around 30 seconds, I ran this at 10 litres per minute and then quickly turned it down to 5 for the welding process. But you can see the differences, pretty much I welded up the first half without any argon. So I had the tube just open to atmosphere and then capped it and then welded the second half under the flow of argon or purged. So as you can see here, this is the sugaring we're talking about, you can see the dark nature of the weld. This is quite porous and really rough to touch and what this does is it can soak up contaminants that are running inside it.

This is really important that we keep those away from the inside of the weld 'cause like I said, it's really just creating a crack on the inside of the weld which can then, if it's over stressed, can then move to the outside and cause your part to fail. So once we purge and run the argon in there you can see the cleanliness of this weld and that creates a very nice little weld seam on the inside and seals up the material and it's very important for anything that has importance on flow that this is a very nice smooth surface, it's not rough to touch, it's great to look at and that was all because of just a minute's worth of argon running through this tube with a couple of capped off ends. From the outside you would never know. This is I guess the issue with a lot of parts and people saving some money on purging, of course you don't need to always purge parts but if you're spending big dollars on something, you want to make sure that the inside flows quite well. This is especially true if you're using a set of headers for racing, you want to makes sure that they're strong and they flow well.

There's no point wasting a whole bunch of money on something that doesn't work properly. So purging on stainless is not necessary but it does create a really nice finish on the backside and is very important for anything that's structural or needs a flow characteristic such as a header. So when we move to titanium I also used the same method just before on a set of titanium tubes, so basically this is one of the half that I left open to atmosphere, prior to plugging up with the silicon purge plugs. You'll see the colouring here and we don't have a whole lot of actual penetration through this but you'll see a lot of the discolouring, this is sort of yellowing and a cloudy finish that has a crack right through the centre. This is because titanium is very reactive to atmosphere and the back side of this weld would have been over the reactive temperature of the material and therefore open to atmosphere, created this reaction which again is no good for flow, no good for strength and no good to look at.

So the back side of the weld looked pretty fine but again, sorry the front side of the weld looked fine but again that doesn't really tell us anything until we look on the inside of the part. So this is the part that we did purge and you'll see here it's got a very nice little weld seam that is running around it. I probably should have spent more time cleaning this up but this gives you a really good example of the way and the differences of purge vs non purge tube. So if you're putting your heart and soul into building a header or an exhaust and you're spending a lot on the actual raw components of this, adding some argon to the inside of it and spending some time purging it is well worth the time and effort and it's not something that we're going to regret in years to come when our non purged header actually starts breaking and we have to reweld it and this is always difficult when it's coated with a whole bunch of mess on the inside of it from the of the combustion cycle. So today we're also going to weld up a motorcycle exhaust so that you can get an idea for the purging process and we'll run through this and give you an idea on what this takes to purge.

The thing is we can't really see inside of it after we purge it so you'll just have to take my word for it that it's going to look like this but at least we can get a pretty good idea for the amount of time that we will need to purge this part for. And create some really good finished welds. So like I said before, we've got a larger cup on this, this is a BVW furick cup, pretty much as large as it gets. This is a really good coverage cup for the outside of our weld area. Again this needs quite a lot of gas, more than our purging process would need.

So now what we'll do is we'll set up this exhaust pipe for the purging process and we can get in and give it a weld. So because we have 3 outlets here, we need, well 3 outlets with only 2 purge plugs, we need to put out inlet purge plug on, I guess we will, it's probably worth putting it closer to the actual part to reduce the amount of gas. And then what I'm going to do is block up the, actually what I'll do is I'll tape this end so that we've got a spare purge plug for the other end and that will allow us to get a really good coverage on this part. So because gas, actually let me rephrase this, because the gas is heavier, what I'm probably going to do is, I wish I had something to stuff down this because we obviously don't need to do any welding. This is a 2 into 1 design so what I will do is I'll cap this and I will tape this off.

We might have to put a couple of small holes in there so that the oxygen can purge out of that. And then spend some extra time letting the gas flow through it so that we end up with the least amount of oxygen possible inside the pipe. So these particles in the atmosphere that react with stainless steel, obviously there's a whole bunch of elements and metal obviously does not like this once it's over a certain temperature. Titanium has a lower temperature where this reaction occurs so it all depends on our weld. We'll grab this tube, that's my weld seam, we'll put the other side into here.

So htis is left free flowing, we'll pop some holes in this part that we've just taped up. Doesn't need too many, it just needs enough to relieve the gases coming out of there. And then we'll grab our purge line, we'll input this into the header flange here without it going too far in. So we want to make sure that that's a nice tight fit so that it doesn't fall out. And then we've got the release here.

So what we need to do is first tack our part so that it's dimensionally accurate and ready to weld. So we don't any purging for this process, we just need to get in, tack it and make sure that that fit up is as tight as possible. When working with any tubing, you want to make sure that the weld seam does not have any gaps, especially stainless steel. As stainless steel expands and contracts, it starts to move around quite a lot so we need to make sure that we add, grab my gloves, we need to make sure that we add a series of tacks around this to ensure that it doesn't move in the final welding stage. And also when we're purging we've obviously got a large gap there which means that the gas will just be exiting that gap instead of actually filling the cavity.

So I'll turn my bottle on, my TIG welder is turned on. And now we can get into the tack welding process. So I've got a 2.4 mm multi mix tungsten here, it's sharpened to around 30°. I'm running a foot pedal which is set up so that on full depression it will run 200 amps. And then we'll get in, I'll position this part which might be a little tricky and we'll get it tacked up and ready to go.

So I've got 2 little scribe lines on here which indicate the centreline. Put the visor down, got a bit of preflow of gas there. One small tack weld on that. And then I'll take this line out for now. Move this part over, we'll get a few more tack welds on this so that it stays dimensionally correct.

Now it's starting to get some strength. So the least amount of gap that we have here, the better. And as a tack weld starts to contract, it can pull the tube around and we need to remedy this by giving it a little pull. Alright so we've got 3 tack welds on that, I'll put another one on here. 4 tack welds and we'll go 5 just for good luck.

The reason why we don't use purging for tack welding is we're not creating enough heat in the part to actually create the reaction with the atmosphere. So by doing short sharp tacks, as you can see there, very small little tacks with a very small amount of heat, doesn't actually break through the back side and then as we're complete welding it, these will melt out and create that nice seam on the back side under the shield of the argon. So we'll put our argon tube in here. We've got a hole in our tape here and we've got a plug in the end here with a hole in that. I'll open up my flow meter.

So I'll run around 10 litres per minute there. I can hear the gas coming out, it is important to be in a pretty open air environment when doing this. Argon is part of the air that we breathe but it can lead to some nausea if you're over ingesting it. Obviously this isn't going to make a big difference but it is something to think about. So I might just grab some V blocks or something to sit that up on.

Cause it is important that we create a low point. So that our tube can fill with argon and then at the moment what is happening is the oxygen in the atmosphere is all leaving the tube from this highest point. The argon is filling up around this area and because this is a nice clean tacked part with a very small amount of gap, once this part gets to, I guess we'll give it a minute or 2 to fill with argon, then we should be right to start our welding process. So again, gas in the lower end, gas or oxygen and atmosphere out the top end. Give it some time, I'm running 10 litres per minute, this is around 20 cubic feet per hour I believe.

But this is different to our torch but this is all running off the same bottle so by using one of these dual flow meters, it can mean that you run one bottle and be able to have an even amount, or sorry a dissimilar amount of gas running from your TIG torch into the machine and your argon into the part for welding purposes. So we're at 10 litres per minute and I'll let that go for a little longer. Tape, I guess if you're using this blue tape, it's a surface painter's tape, it doesn't leave a whole lot of sticky residue once you peel it off but just make sure again that's a long way from the actual heated zone, otherwise this stuff will burn and you'll be actually ingesting a lot of contaminants that are in the atmosphere into the job which is what we're trying to get rid of. Alright so it's always good to feel the amount of gas coming out of this. I've got slightly more probably coming out of the right hand side than the left.

Which is good, we want more flow through this section here which we're welding. And this side we don't really worry about. So what I could have done is if I had something soft or if I had some rag or something I could have stuffed it down inside here to save the amount of gas and save the volume that we have in this tube but it's pretty easy just to wait and let that gas flow in and then once we wait a couple of minutes then we're good to go. So I'm going to leave that at 10 litres per minute. I assume that we would have argon filled in this whole area, most of the contaminants in the atmosphere would have gone out by now so we can now get into the welding process.

I'm going to be fusion welding this which is the process of not needing filler rod, just a small weld and we'll see how we go. Obviously we can't see the back of it so you're going to have to take my word for it but this is a really good example of a typical purging job and if you're building a motorcycle exhaust, or any exhaust for that matter then it is quite important. Alright so now we'll get into the welding process. I do actually find that the weld has a different I guess a different aesthetic to it as you're welding when you're purging from the back side out. Sometimes I think it has a different glow to it and I think this is because of the back side not having that reaction and this is quite important when producing a good looking weld.

So we can move it around now, just making sure that this line doesn't fall out. Again it's difficult to do something like this in one hit. Now what I did there was just give the throttle or sorry the foot pedal a couple of stabs just to continue that post flow of gas over my molten steel, molten stainless steel. When it's glowing like that, that is the point where it's starting to react with atmosphere, so to keep the colour out of it or to keep the contaminants out of it you can just give the pedal a couple of stabs and what that will do is it'll reignite that post flow of gas and you can do it as many times as you need and this is really handy for completing those good looking welds. As we come around to finish our weld, our part gets a little hotter and I need to back out of the pedal a little more.

This is one of the great things about using a foot pedal, you have the option to modulate the amount of amperage as you're going through the weld. And because stainless steel has a very low thermal, very low amount of thermal conductivity, the heat stays in the weld and as you're coming up to the last weld, then you can really notice that the metal starts to fall away more and more so having the foot pedal allows me to back out of the weld as I'm coming up to the hot spots. This will be the final section that will finish it off. Because that was a little hotter, I gave it a few stabs just to make sure that we get complete coverage. I didn't quite finish that.

I can still feel the gas coming out, it's still at 10 litres per minute, the plug's still in so I know that I'm right to continue doing any welding that I need. So that weld is now complete. And again you'll have to take my word for it but the inside should look like this. Because if I hadn't have purged it, it would have looked like this which is a bit of a sugary mess and with the, especially with this exhaust because it's solid mounted to the engine, it would actually have a pretty hard time in years to come staying there as the mount to the chassis would sit here. And if this was actually cracked on the inside which is part of that sugaring then that will be a weak point and a certain failure in years to come.

Alright so I'll hang the welder up now. And remember if there's any questions that you have then jump on in, put them into the comments and I'll get to them at the end. So that's our part welded, we're still at, I should have done this a long time ago, turn the gas off once the weld's complete. This particular gas bottle is quite small, it does last me quite a long time, I was able to weld the roll cage up in my S15 with two of these bottles, they're $99 locally to refill. So doing this purging process, obviously does come at a cost.

But I think the results are well worth it. We can take our purge plug out now, always make sure that this is your second flow meter is off as 99% of the time when doing a lot of different fabrication processes, we're not purging so you don't want any gases leaking out of this second flow meter. I'll take the tape off this end. And now this part is complete. I'll see if I can see in there.

I can see a few little shiny bits which is looking good. Yeah it looks really nice so it's going to be impossible to show you that but agian you're going to have to take my word for it, this is the outside of the weld. So really nice and shiny. And that is a dead giveaway that you're purging your parts and by having the gas coming from the back side and the top side, especially using a larger cup like this on stainless or titanium, it will give your materials coverage, it'll fend off any of those atmospheric nasties that will end up sugaring your material and leave you with a really nice bright shiny weld that'll be strong and if it's in the case of this header, will flow and create a lot of power. Alright so I'm going to open this up for questions.

I hope you've enjoyed this webinar today, again purging is an important part of the process and in motorsports we're always looking to optimise our parts and we often spend a lot of money on the components that go into them so by spending a little more on purging our parts, we can really lift them and also lift performance at the same time. So overall I think it's an inexpensive way to really finish off your parts properly, improve your welding and it's something that I would recommend everybody have a go at. Alright let's get to the questions. Chris asks, could you use something like a bore scope to check the inside of the welds? Or more importantly someone else's inside welds? I'll just switch my welder off. And get to Chris's question.

Yes you could, using a bore scope will allow you to see the inside of the welds. This is probably particularly important if I guess you were spending a lot of money on some parts that if you asked the fabricator if they were purged or not and obviously you spend the money to get them purged and they weren't then this would be probably a huge drama. You really want to be able to check this work and again Chris you're exactly right, you could use a bore scope to be able to check this out and make sure that your parts are purged. Keep in mind that if you're not creating enough heat in your weld, you won't actually get a really nice smooth weld on the back side but you won't get any of that sugaring either. So as you're not really creating that full seam, that full really smooth seam but you're not creating a crack in your part, so it is important to set the right amperage to understand what's happening with your weld, it is quite a fluid weld when you're I guess penetrating right through the material like this.

So sometimes if you're doing a fusion weld like I was there, if it's smaller or you're running less amperage then sometimes you won't really get that visual back side penetrating weld like you would if you were using more amperage or a thinner material. We've got a question, is 200 amps good for tacking with purge plugs? Yep 200 amps will be fine, one thing that I really like to do with tacking is use a lot more amperage than is recommended. So usually we kind of work on that rule of 40 amps per millimetre, this being 1.6 mm wall means that we probably should be running about 100 amps, I've actually got my machine set at 200 amps for those tacks that I was doing, I was pretty much flooring that. So that will give me close to 200 amps instantaneously and what this does is it creates a really energised arc and it brings both of those metals together instantly, whereas if we sit there with 100 amps, it may not join straight away and our parts may start to move away from each other and we would have to input filler rod which can sometimes be a little unsightly and of course if they're starting to move away from each other, it means that our weld is going to be penetrating through to the back side, and of course when we're purging, that's the last thing that we want to do when we're tacking. Unless you've already got that purge set up.

Dave's got a question, if I'm on a budget and making up a custom stainless exhaust for my motorcycle, do I need to purge my welds? It's a lot of extra expense that I don't want to endure. Dave, for my own motorcycles, a lot of the time I really just welded them up without purging them. What I was doing was some really small focused welds that I knew wouldn't actually create that sugaring on the back side. Again these are not strong but for my application and for the jobs that I was doing, a lot of the time on race bikes, modifying headers and trying to work out how to make the most power, again it wasn't on my radar to really purge these parts but if I was ever doing them for other people, then I would focus on making sure that I purged everything and create a full weld so that this creates a nice weld seam. So I guess you're starting to get a feel for yes you need to purge things but no you don't have to sometimes.

And this is a difficult one to juggle. I think it really comes down to the parts, whether they're I guess what use they're going to be put to, what strength they need, I would say that if you were working on a car and building a header, obviously you're using a bunch of different parts, you really should be purging these but again if you don't then it's probably not going to matter, if it's your own vehicle but the last thing you want is for some of your work that someone paid a lot of money for, to fail on them and then for them to see that it isn't purged when your probably should have. Michael's got a question, I purged an inlet pipe the other day and fusion welded it, I didn't see any weld seal on the inside. This is the point that I was getting to before, a very small weld will not, if it's not penetrated through to the back side then you will not see that weld seam on the back side and your purging may really have not equated to much visually but again you wont be creating a crack, you won't be doing any sugaring on the back side of the weld which again will make this stronger than a weld that isn't shielded from the back side with argon. We've got a question from Tom, I was told that chromoly needs to be purged, is this true? In some cases some people will purge chromoly.

I do know a few race teams that build suspension arms and specifically do purge them. This is more for the duration of the parts, a lot of the time if something's getting sealed up, they'll want argon inside the tube rather than atmosphere. Because atmosphere has moisture and a bunch of other elements in it, a lot of the time people that are building racing components, if they're to be sealed, then they will actually purge them, this can be mild steel, chromoly and other things but for most of us at home, we don't need to purge chromoly. It's a fairly non reactive metal and it usually won't add to the strength of the component but it will stop anything rusting from the inside out. Matt had a question on the bungs, where does he buy them and how much are they? How much is a really good question, I bought these a while ago.

Again I bought the full kit, I think they were around $200 USD, don't quote me on that but they are from TIG Aesthetics and I bought them from Ticon. So Ticon have a whole bunch of different bends and junctions and titanium parts and that's who I bought these TIG cups from. This was to do a job for a Formula SAE racecar that used a KTM 690 motor and the guys from the local university wanted a titanium exhaust to lower weight. To reduce weight sorry and improve some power so the money that I got from that job, I put into buying these plugs and they've been a real asset in the workshop. Again the importance of them, I think really comes down to the amount of I guess this stainless gauze and just how it really does spread the argon through the tube meaning that what we do put in there is going to be way more effective than if we just jam a tube in there and crank up the flow.

I think that's about, oh Brandon's got a question, I have a spare bottle of MIG gas in the shop and can I purge with that? It's not recommended, it's probably better than nothing but really at the end of the day, argon 100% argon is the industry standard and if you're going to purge then you're probably going to be TIG welding anyway so it's a really good idea just to grab one of these dual flow meters, whack it on your single bottle and purge the part out, again you don't need to be sitting there pumping heaps of gas through it. So again it's not really going to be a huge expense and I think it's worth it but no, definitely don't use your MIG bottle but it's probably going to be better than nothing. Alright that's bought us to the end of the webinar, remember if you've got any further questions then please feel free to ask on the forums and I'll be happy to answer them there. Again thanks for joining us for today's webinar on purging and happy welding and thanks for watching ETS Fab.