The photo above shows that the first centimeters of the seam did not work out at all. Metal stuck on the sides, and slag in the middle. This is the main problem for beginners. To understand why this is happening and how to deal with it, read a simple explanation from the welder.
Let's make a T-joint of two pieces of 40 by 20 shaped pipes with a thickness of 1.5 mm. We will weld the seams in the lower position, using these examples we will analyze the errors with slagging and lack of penetration.
Why did this problem happen? There was a discrepancy between the thickness of the metal and the diameter of the electrode. What this means, see next.
As they say, you need to dress for the season. So it is with welding, for a correct and comfortable process you need to match the diameter and thickness.
Metal 1.5-2 mm must be welded with an electrode with a diameter of 2 mm.
Metal 2-3 mm, take a diameter of 2.5 mm.
Metal 3-5 mm, electrode 3 mm.
Why is it not advisable to weld 1.5 mm metal, for example, with a 3 mm electrode, as in the example of a seam defect in the photo earlier?
All electrode packs have numbers that indicate the range of welding current for this diameter. In this range, the electrode normally burns and welds. But it works optimally around the middle of this range. The last photo shows Chinese electrodes with a diameter of 3.2 mm. We see the range of 90-130 amperes, 110 amperes for them is the very thing! So we almost come to the main reason for lack of penetration and slagging, look at the photo below.
If we take a 3mm electrode and try to cook a metal with a half-shoe, then we should set a small current, often even less than the minimum value of the recommended range. Such a current will allow the metal to be melted, but the arc pressure at this current is too low to normally blow out the slag from the weld pool. Therefore, the slag fills the welding place, and the metal begins to stick to the part anywhere, this is slag and lack of fusion.
If you add the welding current, then on a thin metal you get this picture. The metal just quickly burns out and you get a burn-through hole. Now it needs to be brewed, and this is not a pleasant occupation on thin metal.
Another thing is when we take a 2 mm electrode, set the welding current in the middle range of 60 amperes and just slowly lead the electrode. Everything will cook as it should, it will not pour slag, because the arc pressure simply will not allow it to be done. There will be no metal burn-through. This is called matching the diameter of the electrode and the thickness of the metal.
But the more your experience, the easier it will be to weld, and despite the correspondence of thicknesses and diameters, take a look
For example, I welded this seam without tearing with a 3.2 mm electrode. There were also no burn-throughs and slagging. But this requires experience and certain movements and speed of the electrode. I will acquaint you with such tricks in the following articles.
So if you are a beginner self-taught, then for comfortable welding in the garage at home in the country, be sure to purchase several diameters of electrodes. For a complete set, have 1.5 mm electrodes. 2 mm, and 3 mm. Use them as appropriate, in terms of thickness, and then lack of penetration and slagging will not bother you!