In industry, in the manufacture of various parts, welding of thin metal with an electrode is often needed. This question remains today one of the most problematic for both beginners to perform welding work, and for experienced welders. We have to weld a variety of products. For example, the body of a passenger car for the most part consists of thin steel sheets. The main use of thin sheet metal, concerns the profitability of production.
Welding is used to connect different metals.
Naturally, this type of welding requires a special approach; several special technological requirements are applied to it.
When such a metal is boiled, the use of an appropriate electrode is very important. The size of the electrode, its size is in direct proportion to the thickness of the sheet metal. For steel sheet having a thickness of 3 mm, welding work must be carried out with a 3 mm electrode. For thinner sheet metal, very thin electrodes are specially selected. For example, when a sheet has a thickness of 2.5 mm, an electrode of the same diameter is required.
Electrode position during welding.
When welding thin metal is carried out, it is necessary to have a supply of welding current of a certain size. This parameter depends on two values:
- the size of the electrode.
When a 3 mm steel sheet is welded, the welding current is usually made over 140 A. When a particularly thin electrode is used, the welding current must be lowered. Usually installed 50 A.
Another important parameter when working with thin metal is the type of electrodes used. The small thickness of the metal requires a small current, it needs electrodes that have a coating that makes it easy to get a spark and its uniform burning. Melting of such electrodes should be very slow. During the welding process, the metal should become fluid.Back to table of contents
Semiautomatic welding: nuances
Most often today you can find welding semi-automatic. This device has been specifically designed for welding thin sheet metal. The most recognized is the inverter.
For welding different metals using different electrodes.
The semiautomatic device copes with such task very easily. Since he has a special adjustment, he is able to supply very little current. Such an operation depends on:
- feed rate of filler material;
- current strength.
However, as elsewhere, practice and experience come first. Semiautomatic allows continuous welding, when the seam is smoothly conducted over the entire surface of the part. He has the ability to perform spot welding. When using a semiautomatic device, it is not necessary to tap the electrode on the metal, simply press the toggle switch at the right moment.Back to table of contents
Basic about the electrodes used
Varieties, sizes and coatings of electrodes today can be seen very much. To conduct welding on a small current, apply electrodes with a special coating. It helps the rapid appearance of a spark, supports steady burning. Such an electrode has a slow melting and forms a flowable metal. As a result, the seam has a beautiful appearance.
The welding scheme is covered with a metal electrode.
These requirements are fully met by the OMA-2 electrode. Its coating consists of:
- titanium concentrate;
- ferromanganese ore;
In addition to the above substances, the coating has other additives that ensure stable arc burning. That is what is needed when welding thin metal.
Electrodes of the MT-2 brand also have similar properties. They are also easy to cook very thin metal. But, unlike OMA-2, welding should be carried out only with direct current, and having a reverse polarity. When the thickness of the welded metal sheets exceeds 1 mm, it is allowed to conduct welding with alternating current.
Thin steel sheets are well cooked by gas welding.
It turns out very high-quality seam, which is much higher than the seam obtained by electric welding. But, it should be noted, in the presence of an inverter, it is not at all necessary to specifically purchase gas welding equipment to make one seam. Uneconomic and inefficient. With a certain experience and skill you get a good seam when using electric welding.Back to table of contents
A few tips from the masters of welding
To perform welding work will require:
- welding unit;
- sheet steel.
Overlap welding is done by overlaying sheets of metal. The size of the overlap depends on the state of the edges. The smoother they are, the smaller the overlap is. It is desirable that the size of overlaying sheets exceeds 5 mm.
Sheets between themselves should have a tight contact. To do this, use clamps, clamping brackets or heavy pressure loads. Sheets should not have any lumen between them, as it can cause burning of the top sheet.
For the welding operation you need to set a certain value of the welding current. This value depends on:
- electrode size;
- sheet thickness.
When the steel sheet has a thickness of less than 1 mm, the welding current parameter must reach 40 A. A much smaller current is used for electrodes with a diameter of 2 mm. When the diameter is 3 mm, the current increases.
Before you start serious work, you need to practice a little on a sheet of metal of similar thickness. Thanks to this, it will be possible to determine the optimum value of the welding current. It is in direct relation with the mains voltage and the values set on the device. During trial welding it will be possible to work out a certain manner so that there is no burning of the metal. The fact is that you will often have to extinguish and re-ignite the arc. If you delay a little with the removal of the electrode, a hole in the metal is sure to appear.
The end of the welding electrode.
Weld sheets first need to grab among themselves. For this, small suture jumpers are made. Usually their value does not exceed 10 mm. Jumper pitch is 50 mm and is made along the entire butt length. The welding process must be interrupted periodically. The electrode is withdrawn to extinguish the arc, then quickly re-ignites, for such moments there will be no cooling of the metal. The magnitude of the current and the size of the thickness of the metal affect the time at which a continuous arc is observed. The arc burns for about 3 seconds when the metal thickness is less than 1 mm.
After working certain skills, you can begin to perform the main technological welding process. Sheets need to be welded completely. For this welding is done intermittent seam. To obtain such a seam, the electrode is periodically moved to the cold part of the joint. As a result, the metal will not start to warp, especially when the joint has a length greater than 200 mm. When a continuous seam has a short length, warping is minimized. Welding must begin at the butt end, gradually moving to the other side, then to the middle, and so on.
It is possible to weld very thin metal sheets using the butt-joint method. For such an operation, it is necessary that the edges of the sheet have a minimum gap relative to the total length of the joint. The best is the absence of any gap. In order to butt-weld thin sheet metal, a special auxiliary backing is installed at the bottom. This is imperative, since it is very difficult to carry out welding work with a very thin sheet metal without a lining. However, if there is a welding inverter, excellent electrodes, imported, such welding is quite acceptable.Back to table of contents
- Current adjustment.
- Welding step.
All of the above corresponds to the overlapping welding operation.
When there is an opportunity, it is possible to carry out welding work using a metal non-retractable lining. In this case, under the bottom of the joint is placed a steel strip having a thickness that corresponds to the thickness of the sheet. The lining should be at least 15 mm wide. For good weldability sheet metal must necessarily fit snugly to the lining. Thanks to this additional plate, it is possible to weld parts when the joint gap is equal to several mm. The lining itself at this time is completely welded.
When, according to the process, the presence of a non-falling lining is prohibited, welding is performed using a copper lining. A thick copper strip is enclosed under the joint below. Thanks to non-ferrous metal there will be a powerful heat removal, the appearance of burning sheets will stop. After completion of the welding, the copper lining is removed.
If the copper plate is absent and it is not allowed to leave the steel lining, it is envisaged to remove the metal with a conventional grinding machine after welding is completed.