Welding thin metal:

Welding thin metal is a challenge even for some experienced welders. Beginners in welding generally have a hard time. The rules that work here are not at all the same as when welding thick products: there are many features and difficulties, which makes it harder to select modes and electrodes. It is easier to do this with semi-automatic welding machines, but they are quite rare in everyday life, inverters are much more common. Here we will talk about welding thin metal with an inverter. 

And the first difficulty in welding metal of small thickness is that it cannot be heated strongly: it burns out, holes form. Therefore, they work on the principle “the faster the better” and we are not talking about any trajectories of the movement of the electrodes at all. Sheet metal is welded by conducting the electrode in one direction – along the seam without any deviations.

The second difficulty is that you need to work at low currents, and this leads to the fact that the arc has to be made short. With a slight separation, it simply goes out. There may also be problems with arc ignition, so use devices with a good current-voltage characteristic (open circuit voltage above 70 V) and smooth adjustment of the welding current, which starts from 10 A.

Another nuisance: with strong heating, the geometry of thin sheets changes: they bend in waves. It is very difficult to get rid of this shortcoming. The only option is to try not to overheat or remove heat (read below about the method with heat-removing pads).

When butt-welding thin sheets of metal, their edges are carefully processed and cleaned. The presence of dirt and rust will make welding even more problematic. Therefore, carefully align and clean everything. The sheets are placed very close to each other – without a gap. Details are fixed with clamps, clamps and other devices. Then the parts are tacked every 7-10 cm with short seams – tacks. They will not allow parts to move and are less likely to bend.

How to cook thin metal with an inverter

Welding machines that produce direct current are good because we can cook on reverse polarity. To do this, connect the cable with the electrode holder to the “+”, and connect the “-” to the part. With this connection, the electrode heats up more, and the metal warms up minimally.

Read about how to choose a welding inverter for your home or garden here. 

It is necessary to cook using the thinnest electrodes: from 1,5 mm to 2 mm. In this case, you need to choose with a high melting coefficient: then, even at low currents, the seam will be of high quality. The current is set to small. For electrodes with a size of 1,5 mm, it should be about 30-45 amperes, for the “two” – 40-60 amperes. In reality, sometimes they put even lower: it is important that you can work.

In order for the metal to heat up less, the parts are placed in a vertical or at least inclined direction. Then they cook from top to bottom, moving the tip of the electrode strictly in this direction (without deflecting or returning). The angle of inclination is an angle forward, while its value is 30-40 °. So the heating of the metal will be minimal, and this is one of the most important tasks for welding thin metals.

General recommendation for choosing electrodes for welding thin metals: buy high-quality imported electrodes for such work. Problems will be much less.

Read about making a barn on a metal frame here. 

Techniques and methods for welding thin sheets of metal

Sometimes thin sheets need to be welded at an angle. In this case, it is more convenient to use the flanging method: the edges of the sheet are bent to the required angle, fastened with short transverse seams every 5-10 cm. After that, they are welded as mentioned above: with a continuous seam from top to bottom.

The video shows how to weld thin sheet metal with an electrode using a welding inverter. The flanging method is used: the edges of the parts are folded over, then tacked in several places with short seams. This is followed by welding with a thin electrode 2 mm thick.

It is not always possible to avoid burn-through when welding without separation. Then you can try to tear off the arc for a few moments, and then lower the electrode again in the same place and advance it a few more millimeters. So, tearing off and returning the arc, and cook. With this method, it turns out that the metal has time to cool down during the arc break. In the video you will see how the color of the welding spot changes after the electrode is removed. The main thing is not to let the metal cool too much.

Welding of thin metal with arc break-off is demonstrated in the first part of the video. The docking method is overlapped (one part overlaps the second by 1-3 cm), an electrode with a rutile coating is used (for structural and low-alloy steels). Then the welding of stainless steel with a stainless electrode with the main coating is shown, and in the end, the ferrous metal joint is welded with the same stainless steel electrode. The seam, by the way, turned out to be of better quality than when using the recommended electrodes.

Read about the choice of electrodes for welding with an inverter machine.

If the welding of thin metal does not require the creation of a continuous seam, a spot weld is used. With this method of welding a small size, the tacks are located at a short distance one next to the other. This method is called intermittent suture.

In general, butt-welding thin iron by welding is difficult. Overlapping is easier: parts do not overheat so much and there is less chance that everything will “lead”.

Read about the types of welds and joints here. 

When welding thin metal butt, it is possible to lay a thin wire with a diameter of 2,5-3,5 mm between the sheets (you can beat the coating on damaged electrodes and use them). It is positioned so that on the front side it is flush with the surface of the metal, and on the wrong side it protrudes by almost half the diameter. When welding, the arc is led along this wire. It takes the main thermal load, and the welded metal sheets are heated by peripheral currents. At the same time, they do not overheat, they do not warp, the seam is smooth, without signs of overheating. After removing the wire, it is difficult to see traces of the fact that it was present.

Another way is to put copper plates under the junction. Copper has a very high thermal conductivity – 7-8 times higher than that of steel. Laid under the place of welding, it takes away a significant part of the heat, preventing overheating of the metal. This method of welding thin metals is called “with heat sinks”.

How to weld a metal gazebo, read here. You may be interested in reading how to make a brazier from a gas cylinder or metal? The thing is necessary and suitable for mastering welding.

Galvanized welding

Galvanized steel is the same thin sheet, only coated with a layer of zinc. If you need to weld it, on the edges to be welded, you will have to remove this coating completely, to bare steel. There are several ways. The first is to remove it mechanically: with an abrasive wheel on a grinder or grinder, sandpaper and a metal brush. There is another way – to burn out by welding. In this case, the electrode pass twice along the seam. In this case, zinc evaporates (it evaporates at 900 ° C), and its vapors are very toxic. So these works can be carried out either on the street, or if there is an exhaust hood at the workplace. After each pass, you need to shoot down the flux.

After the complete removal of zinc, the actual welding begins. When welding galvanized pipes, two passes with different electrodes will be needed to obtain a good seam. The first seam is welded with rutile-coated electrodes, for example, MP-3, ANO-4, OZS-4. In this case, the oscillations have a very small amplitude. Upper seam – facing make wider. It is approximately equal to three electrode diameters. It is important not to rush and boil well. This passage is used with electrodes with a basic coating (for example, UONI-13/55, UONI-13/45, DSK-50).

Read more about choosing electrodes for inverter welding here.