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Practical TIG Welding: Aluminium

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00:00 - TIG welding aluminium can be very satisfying once we master the process and manage to achieve that uniform stacked dime appearance on our welds, however this relies heavily on using the correct settings on your machine.
00:13 Aluminium places less importance on the shielding gas coverage than that of ferrous metals due to the lower reactivity of the material but your AC balance and frequency settings are critical.
00:24 Aluminium has a very high rate of thermal conductivity which means it's hard to get heat into the part when we start the weld but once the part heats up, it'll spread very quickly requiring either a reduction in amperage as the weld progresses or an increase in the speed we move the torch and add filler rod in order to control the heat in the material.
00:44 As we've already discussed, this is where a foot pedal can be a big help in assisting us in keeping that consistency and keeping your weld bead looking uniform.
00:54 Common motorsport components like radiators, plenums and pipework will often have long welds on them where inconsistencies will be more obvious than on smaller parts.
01:04 As we've learned in the practical skills section, material preparation is key to a quality weld and nowhere is this more important than with aluminium.
01:13 Care must be taken to make sure that every part of the weld area and the surrounding material is clean and free from contamination and oils.
01:22 This also includes the back surface of the weld area if it can be accessed.
01:26 This is often overlooked but you'll sometimes find impurities can be dragged through the weld pool in this way.
01:33 Cutting and linishing abrasives should also be dedicated for aluminium use only to avoid any cross contamination with ferrous particles.
01:41 It's good practice to use scotch brite to thoroughly clean the weld area and then wipe your work piece as well as your filler rods down with acetone prior to welding.
01:50 It's incredible just how much dirt is on brand new filler rods straight from the factory and if not clean, this is going to be put into your weld pool.
01:58 People sometimes get confused with the AC balance setting as this is referred to as the cleaning action, thinking that it's there to clean the part.
02:07 As we've already learned, this simply isn't the case and the AC balance is there to break down the oxide layer only.
02:13 This oxide layer is always on aluminium as long as it's in contact with oxygen.
02:19 The oxide layer on the aluminium melts at more than double the melting temperature of the parent metal beneath it which is why this setting is so crucial.
02:28 An AC balance that's too low will not allow enough time for the oxide layer to be broken down sufficiently thus pulling contaminants into the weld.
02:36 The cleaning action is what leaves a visible white etching at either side of our weld pool and this is totally normal.
02:43 If the white etching looks very wide and deep, that can suggest the AC balance is too high and too much cleaning action is happening.
02:52 This isn't as detrimental compared to the other side of the scale where we have insufficient cleaning though.
02:57 If there's little to none of this white etching, then this indicates we need to increase the AC balance to ensure a clean, pure weld pool.
03:04 Balance and frequency settings and the physics of what's actually happening have been covered earlier in the course so we won't repeat too much here.
03:13 While a lot of welders just want to learn what setting to apply to their machine so they can get stuck in, we believe that understanding what's going on behind these settings will help you to identify problem areas and understand how to solve them.
03:27 There's a lot of different grades of aluminium filler rods available but for the majority of alloy we use in motorsport, we'll be either using a 4043 or 5356 filler rod.
03:38 Starting with a 4043, this filler rod has a nominal 5% silicon alloy.
03:43 This makes the weld pool wet out easier which makes welding easier for beginners.
03:48 Due to this, it can be a better choice for aesthetic applications.
03:52 Another benefit of 4043 is that it's more suited to applications where the part is subjected to sustained temperatures of approximately 70°C which will often be the case in a motorsport environment.
04:05 5356 filler rod has a nominal 5% magnesium alloy and requires a little more skill during the welding process as it can sometimes result in a weld that doesn't look quite as clean.
04:17 The small percentage of magnesium makes for a stronger weld that offers greater shear strength.
04:23 The 5356 filler rod is suitable for welding a wide range of 3000, 5000 and 6000 series alloys.
04:30 The greatest strength characteristics of this filler rod will be compromised though if it's subjected to high temperatures.
04:38 This heat tempers the weld pool, making it act more like a 4043 rod.
04:43 5356 is also the choice of rod if your part is to be anodised as it offers greater colour matching characteristics.
04:51 When welding cast alloy, the filler rod choice can be tricky and there's often debate over the correct rod.
04:57 Before tackling a cast aluminium welding job we do need to understand the composition of the part.
05:02 Common aluminium alloy is used in cast parts are 3000 series which contains silicon magnesium alloy.
05:09 4043 would be the rod of choice for this application due to them sharing the silicon alloy.
05:15 Another common cast aluminium is 5000 series alloy.
05:19 These contain more magnesium in them so a 5356 rod would be better suited for this job with its higher magnesium percentage.
05:27 The tricky part however is that you're not always going to know exactly what that alloy used in your casting is.
05:34 It's important to understand that not all alloys are able to be welded too.
05:38 Aerospace alloys such as 7075 for example aren't designed to be welded and will almost certainly crack if you try.
05:46 When it comes to analysing your welds, a good weld should be shiny in appearance.
05:51 A dull grey weld indicates something isn't right and this could be a series of issues or just one key aspect.
05:58 Potential problems could include poor torch positioning, poor shielding gas coverage or excessive shielding gas flow which is causing arc instability.
06:07 Another possibility is excessive heat.
06:09 Pin holes or craters in the weld pool would suggest your AC balance setting may be too low which isn't allowing enough cleaning action and pulling impurities from the oxide into the weld pool or possibly inadequate shielding gas coverage.
06:24 This should not be ignored and in most circumstances the best option is to go back and grind out the section with pin holes and reweld this area.
06:32 A unique aspect when TIG welding aluminium is that it's totally normal for the tip of your tungsten to ball up during the welding process.
06:41 Exactly how much the tip balls up is going to depend on your AC balance settings.
06:46 Too much cleaning action will cause the tungsten to ball more compared to a lower cleaning setting.
06:52 There is no need to resharpen your tungsten here, provided that the ball remains shiny.
06:57 In the resources section of the course, you'll find a printable PDF that'll give you all of the recommended baseline settings for welding aluminium.

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