Welding defects: how to make a good weld in DIY projects

N.B. All tips and errors mentioned in this article refer to welding with solid wire and gas.

Maybe you haven’t thought about it yet, but remember that it’s important to know welding defects. Just as important as the WOW effect. Oh yes, because even do-it-yourself projects and home repairs require ad-hoc welding: the stability of what you are making depends on it.
This article is for beginners who want to learn to weld as well as for those who can already weld but want to improve. In short, we don’t expect you to become as good as a pro, but we wish to give you the right tips to do a good weld.

Wire welding defects: we have the pictures!

First of all, to help you understand the various defects, we took some pictures and did some tests. They were all done on a corner joint. If you don’t know what it is, look up the article on weld joints.
Then we did some very thorough investigation work: a bit like a detective. To get a good look at welding defects, you need a destructive test: basically, you need to break the welded workpiece. If you want to show off, you can tell your friends you saw a weld macrograph but we’ll call it just “macro” for convenience.
Of course, don’t do it at home. First, because it’s not just about being a junior chemist. Second, because we know that it is very difficult to destroy your workpiece that you have welded with so much effort!
And now let’s get down to business: let’s weld!

First test: ‘Shoot! Everything went wrong’

Here we show you all the mistakes you can make and the welding defects that come from that.
Mistake 1: use laminated plates, that is metal blades covered in crusts (called scale) and with rounded corners.
Mistake 2: oscillate during welding (while making the joint). See the red arrows in the picture below?
Mistake 3: ‘pull’ the wire welding torch, that is, keep the feed direction you see in the picture.

This is the result.

It looks good but there are various welding defects! Can’t you see them? We’ll help you.

Here, the weld bead (the deposit of filler material we created) has uneven edges and bulges a lot. This happens because we have set the incorrect electrical parameters. We did it on purpose of course! Especially because a helviLITE wire welding machine won’t let you make a mistake like this because this welder helps you set the correct value. Here, however, we have set the electrical parameters very low compared to the thickness to be welded. We did this precisely so that you can see what the result should NOT be like. And it is not just an aesthetic flaw.
In doing so, we created sticking points, the first of the welding defects we come across. Basically, we squashed some filler material there, without allowing it to fuse with the workpiece to be welded. Yes, the workpieces do stay together, but only to keep each other company.
But there is another flaw here.

The red circle highlights an end crater. Of all welding defects, it is one of the most insidious, because it is dangerous: cracks could form and the joint could break.

Now let us look at our macro. We break the workpiece and analyse the cross-section of the weld.

Leaving aside the fact that we did not join the workpieces at 90°, we also find the asymmetry of the weld bead. In practice, the two sides of the bead (those attached to the sheet metal) are not the same.
Moreover, you can now see the famous bulge we were talking about.

With the bulge, the weld is not joined at the sides. It means that the workpiece will break because of the sharp edges we have made.
And that’s not all! There are two more welding defects: failure to penetrate the root and sticking (which we have already mentioned).

That hole between the workpieces that you see in the red circle is the failure to penetrate the root. It is caused by the fact that we used a laminated plate with rounded edges. This defect is also dangerous because if a force comes from the opposite side of the weld, that hole becomes the arm of a lever and the workpiece will break.
In this section we can then go search for sticking. Do you see that dark line that starts from where penetration failed and goes towards the bead? That’s sticking: it means that we have not really welded and that our work has not served its purpose.

Second test: ‘let’s fix two of the mistakes’

Here we did the test again, eliminating two of the three mistakes from the first test: the torch mistake and that of the rounded edges. Basically, we have now welded with the torch pushing, from right to left. In addition, we used the grinding wheel to get the sharp edges. In this picture you see the right position of the torch.

Here is the result.

Once again, we made a mistake on purpose. We set the electrical parameters too high. The weld bead is more spread out, but… it’s too much! The welding defect that forms is an undercut that we highlighted with a red line. It is a reduction in the cross-section of the plate, therefore a reduction in the load-bearing thickness.

In the next picture, however, you see what a lack of manual skill creates. The bead is uneven and its cross-section narrows, as in the red circles.

And now we do a macro.

Here you can see that we used the grinding wheel! You can also see that we did better because the sides are well joined and the root is fused. But there is still some asymmetry.

Third test: ‘let’s change workpieces’
Now let’s eliminate mistake 1 completely by using a drawn plate. Sure, it is more expensive than the laminated one, but it’s already clean and has sharp edges.
Obviously, we’ll avoid the other mistakes and perform the joint by pushing the torch. We are careful to spot-weld the wire on the root, where the two workpieces meet. Heads up: this is a great tip!

Let’s look at the result.

As you can see from the red box, the weld is better, by far! The weld bead is nicely spread out even if the cross-section is not so regular (always watch out for undercuts). At the end, however, we find the end crater. You can recognise it by now, right? We’ll highlight it for you.

Do you want to avoid this welding defect? Here’s our second tip: towards the end, accelerate and go back for at least a centimetre with the electric arc on, and then shut it off.

Now let’s have a look at the macro.

See? With sharp edges, penetration improves. We also started from a clean workpiece, so the edges of the weld join perfectly with the workpiece. Finally, this time we set the parameters correctly and you can see it from the well-spread bead.
Yes, you’re right: there is still some asymmetry. You can see that in some points we increased the forward speed but we can be satisfied. Know why? Because we eliminated all the mistakes. From now on it’s just a matter of practice.

So, how can we avoid the most common welding defects?

Here are the last three tips:

  • always weld on a clean surface. If you are using laminated material, remove the scale (black crust) and the rounded edges with a grinding wheel before starting to weld;
  • in wire welding, push the torch. In stick welding, instead, pull the coated electrode;
  • never oscillate on a corner joint. Welding must be done straight and at a constant speed.

Finally, don’t forget that welding is easier with helviLITE welding machines, because they help you adjust the settings based on the thickness of the workpiece you need to weld.

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