Full penetration welding is one of the types of welded joints that can be obtained during processing. Compared to other results, it differs markedly in its construction, behaviour and the controls to be carried out to verify its quality. Let’s find out more about what it is and how best to achieve it.
How to form a weld seam
When making a weld seam, when there is a continuous connection between two materials, there are several welding techniques that can be used. Nevertheless, the results can be three:
- Full penetration welding
- Welding not fully penetrating
- Corner cord welding
In the first two cases they are head to head welds (called in technical jargon “T-welds”) where, before the process itself, the materials to be joined are worked to obtain the same thickness and a perfect adhesion to each other.
Preparation of the flaps to be welded: kerfing
In order to prepare the edges of the materials in the best possible way, the first step is the kerf-framing: carried out by thermal break or mechanical processing, it allows to obtain the so-called kerf-framing, the angled cutting of an edge, on which to carry out the welding process.
The kerf can be:
- V-shaped: suitable for thicknesses between 5 and 20 millimetres, has a bevel of 60°. The distance between the flaps is maximum 3.5 mm.
- 1/2 V-shaped: carried out on thicknesses up to 15 mm, it must be carried out with great care to avoid damaging the edge of the material.
- K-shaped: indicated over 12 mm, when the material to be welded is accessible from both sides
- X-shaped: used for thicknesses greater than 15 millimetres, especially when it is possible to weld on both sides of the material. Depending on the position and welding process, the distance between the two edges varies, usually 3 or 4 millimetres.
- U-shaped: used for thicknesses greater than 20 millimetres, it is the most expensive as it cannot be made by cutting with a blowtorch.
- J-shaped: used for thicknesses over 20 millimetres, in this case the flaps are between 3 and 4 millimetres apart.
The preparation phase of the flaps is crucial for a successful welding, for this reason a lot of attention and a continuous verification is required.
Perform a correct complete penetration welding
To perform a complete penetration welding correctly, the thickness of the metal must first be taken into account: when it is low, usually less than 4 millimetres, it is sufficient to clean the edges thoroughly and place the materials side by side. In this case, even a single pass can be sufficient, especially when using the MIG/MAG continuous wire technique.
Over 4 millimetres, the flaps must be prepared carefully in order to ensure correct penetration and facilitate welding.
The preparation depends on several factors such as the position, the thickness of the sheets, the type of joint we want to obtain, the base metal and what degree of penetration is required.