When it comes to welding, there are various techniques that can be used to achieve different results. One of the key decisions welders need to make is whether to use a single-layer or multi-layer approach. Each technique has its own advantages and challenges, so it's important to understand the differences between them.
What is Single-Layer Welding?
Single-layer welding, as the name suggests, involves creating a weld using just one layer of filler material. This technique is often used for simpler projects where strength and durability are not the primary concerns. It can be quicker and more cost-effective than multi-layer welding, making it a popular choice for beginners or for projects with time constraints.
The weld with the size of the welding foot less than 8mm is usually completed by single welding (a layer of a weld), and the diameter of the welding rod is selected within the range of 3~5mm according to the thickness of the steel plate.
The weld with the size of the welding foot less than 5mm can be welded by the linear strip method and short arc, the welding speed should be uniform, the Angle of the electrode is 45° with the horizontal plate, and the welding direction is 65°~80°. Too small electrode Angle will cause insufficient root penetration; If the Angle is too large, the slag will easily run to the front and cause slag inclusion.
When using the linear conveyor method to weld the weld with a small foot size, the sleeve edge of the electrode end is leaned against the weld and gently pressed against it, and when the electrode melts, it will gradually move along the welding direction. This is not only easy to operate, but also the depth of penetration is larger, and the appearance of the weld is beautiful.
When the size of the welding foot is 5~8mm, the oblique circle or anti-sawtooth strip method can be used for welding, but the speed of the strip is different, otherwise it is easy to produce edge biting, slag inclusion, and poor edge fusion.
What is Multi-Layer Welding?
On the other hand, multi-layer welding involves building up the weld using multiple layers of filler material. This technique is often used for projects that require a high level of strength and durability. While multi-layer welding can be more time-consuming and costly than single-layer welding, it can provide a stronger and more reliable weld in the long run.
When the size of the welding foot is 8~10mm, the welding method of two layers and two passes can be used.
When welding the first layer, a electrode with a diameter of 3~4mm can be used, and the welding current is slightly larger to obtain a larger penetration depth. Using the linear strip method, the arc pit should be filled or slightly higher at the end of the welding, so that the arc pit will not be too low due to the increase in the temperature of the weld at the second end of the welding.
Before welding the second layer, the slag of the first layer must be removed. If slag inclusion is found, the second layer can be welded after repairing with a small diameter electrode, so as to ensure a tight fusion between the layers. When welding the second layer, a 4mm diameter electrode can be used, and the welding current should not be too large, because too much current will cause edge biting.
Which Technique Should You Choose?
Choosing between single-layer and multi-layer welding depends on the specific requirements of your project. If you need a quick and cost-effective solution for a simple project, single-layer welding may be the way to go. However, if strength and durability are your top priorities, multi-layer welding may be the better choice.
Ultimately, mastering welding techniques involves understanding the pros and cons of each approach and selecting the one that best suits your project. Whether you choose single-layer or multi-layer welding, practice and experience will help you improve your skills and achieve better results.
