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Practical TIG Welding: Achieving Correct Gas Flow

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Achieving Correct Gas Flow


00:00 - One of the most important aspects of TIG welding is the shielding gas that protects our weld and since this gas stream is invisible, we need to understand its characteristics so that we can manipulate its flow to ensure that we're properly shielding our weld and the heat affected zone.
00:16 As we've learned already in the body of the course we use 100% argon for all TIG welded metals that we come across in motorsport.
00:23 It's stored at high pressure in bottles which is then distributed to our welder by a gas regulator.
00:30 Earlier in the course, we looked at the two types of flow regulators available for welding use and to reiterate, the ball bearing style flow meter is best suited to TIG welding because we can visualise our flow rate very easily.
00:43 Increasing and decreasing the amount of flow is easily achieved by only enclosing the valve on the regulator and the ball bearing's height corresponds with an indent that will then tell us the gas flow in either cubic feet per hour or litres per minute.
00:57 Setting this flow rate will depend on your application.
01:00 Our material specific section has some good baseline settings for you to follow to get you started but this is only one aspect of setting and achieving correct gas flow.
01:11 First it's always advisable to double check if our gas flow rate at the regulator is the same as what we're seeing at the torch.
01:18 We do this by using the same ball bearing style flow meter as our regulator only this one sits over our TIG torch and if everything is correct, it should read the exact same flow rate as our bottle's regulator.
01:31 This is a great way to ensure there are no argon leaks inside your TIG machine or in the torch lead.
01:36 If our flow rate's set and our welds are perfect, then you wouldn't need to be doing this every time you fire up the TIG but it can take the guess work out of diagnosing an argon supply or contamination problem that may cause some very weak and ugly welds.
01:52 Any leaks in the argon plumbing system can introduce contaminants into your gas stream so if you have a difference in gas flow between your regulator and torch, then consider this and double check all of your fittings and hoses.
02:04 Contamination is pretty easy to spot and presents many symptoms.
02:09 Fizzing and sparking while welding is a clear sign that you're having major contamination issues, while milder symptoms might present as discolouration of the weld area with small holes in the weld itself signalling porosity.
02:22 It's important to note that contamination can present differently in different metals.
02:28 Generally though if the weld is shiny and has a uniform shape without and craters or holes, this is a good sign that it's contamination free.
02:37 On the other hand, if the weld is dull and has visible craters or even small holes then the weld is likely to be contaminated which would be a potential sign of a lack of shielding gas.
02:47 Achieving the correct gas flow is a balancing act between having just enough and not too much but in most situations you'll find that between 8-10 litres per minute will cover the majority of positions and cups you're likely to be welding with.
03:02 For the larger and more specialised cups on the market, we may need to significantly increase our argon flow and a good rule of thumb here is to increase the flow by around 50% or in other words, we should be looking at around 12 to 15 litres per minute and this is if you've been given no information relevant to your specific gas lens.
03:21 The majority of the manufacturers of these lenses however will give you recommendations on the correct gas flow settings needed to acheive the correct shielding so you should simply follow their recommendation.
03:34 Regardless, it's a great idea to produce some test welds to ensure your settings are right before moving onto welding the real thing.
03:41 When running test welds in DC mode, it's important to follow our preparation procedures and ensure the material is clean and shiny.
03:49 This will give you the best opportunity to see the head affected zone and the discolouring that comes from the effective shielding gas perimeter.
03:57 This can be seen as blue, purple or straw colouring of the material which indicates a reaction is occurring with atmospheric air.
04:05 Although argon is invisible, a little knowledge on the characteristics of the gas can go a long way to achieving the best results and solving these problems.
04:14 Argon is heavier than air and tends to flood into corners which means we require less argon flow when welding into enclosed areas and more when welding on outside corner joints.
04:25 It might seem like just increasing the gas flow would be a solution to potention shielding problems but too much gas flow causes its own set of issues such as turbulence which can then pull the atmospheric air into the gas stream, contaminating the weld.
04:40 By following the flow rate guidelines detailed in our material specific section and ensuring there are no leaks from the gas bottle to the torch, we shouldn't have any issues in the setup of our welder.
04:51 What can still present problems is the environment we work in though.
04:55 Try to block any potential breeze and be careful when you're lifting your helmet that you're not moving the argon away from where we need it.
05:02 Achieving the correct gas flow is a fundamental requirement of a strong quality weld.
05:07 We can have the best technique, the best products and work with the best materials but without sufficient gas coverage we won't be able to produce a good weld so pay attention to your gas flow as your weld requires it.

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