How to weld a profile pipe

Profile pipes are often used in the construction of metal structures, in creating frameworks for greenhouses, making supports or masts subjected to vibration when installing fences. Pipes are made of square and rectangular section, sometimes oval. Learn how to weld the profile pipe to make the product durable and the seam beautiful.

What is a profile tube

The profile pipe is a type of metal-roll, it is made by means of a circular pipe molding. After thermal deformation, metal stress is removed. The material for the product is carbon steel or stainless steel. The cross section of pipes ranges from 10 × 10 mm to 500 × 400 mm. The thickness of their walls is from 1 to 22 mm. Such pipes have significant advantages:

• Large selection of sizes allows you to choose the material for any metalwork.
• Standard sizes facilitate the joints of parts.
• Uniform pipe thickness allows for a reliable seam.
• Smooth surface.
• The weight of the pipe is less than that of all-metal rolled products; the construction of it is made easier.

Before welding the profile pipe, you should consider the advice of professionals on the technology of the work. For welding steel pipes used well-known types of welding: electric, gas, contact and semi-automatic. Let us consider in detail how to cook a profile pipe in each of the listed ways.

Electric arc welding

The ease of use and high-quality seam, as well as the ability to use arc welding to work in hard-to-reach places, made this method very popular. Use for products with a wall thickness of more than 4 mm requires edge preparation. To work you will need a welding machine, which can be rented if you do not have one.

The profile pipe is welded in various ways: overlapped, butt-joint, T-joint or at any angle. Qualified welders advise the lower position of the seam, but you must be guided by your own conditions, you can use a horizontal or vertical seam.

For work you will need:

• welding machine;
• electrodes;
• face shield and gloves;
• fixture for fixing pipes;
• sandpaper and metal brush.

Electrode selection

The quality of the connection depends on the type of electrodes used to weld the profile tube. The electrode of small diameter will not provide the strength of the seam, and excessive thickness will lead to the burning of the pipe. A suitable electrode should maintain a steady arc and prevent oxidative processes.

Profile pipes of the same diameter are welded with non-consumable electrodes using argon as a protective gas.

The choice of the diameter of the electrode depends on the size of the pipe walls. For thin metal up to 2 mm, an O 1.5 mm electrode will work, for a thicker metal of 2–3 mm, an O 2 mm electrode will be required. For metal more impressive thickness? 4–6 mm electrode O 4 mm is required.

Details for welding are fixed on a special table or made for this device. It is necessary to remove dirt and lubricants from them. A point-sticking of metal is performed to secure the structure. After alignment, the main process is performed. Welding arc lead with a speed that allows the edges to melt, but the metal does not have time to flow inside.

There is no general recommendation on how to properly perform welding, the optimal speed is chosen in a practical way.

For thin-walled pipes, welding is done at one time; to join a thick metal it will take several passes to weld all layers. Edging allows you to perform several seams and reduce metal stress. The mode of arc welding is affected by: current strength, polarity, electrode diameter, voltage, type of current. The current can vary from 20 to 90 amperes, it is calculated based on the thickness of the electrode. When working with thin metal, a direct current with reverse polarity is recommended.

In the process of welding slag is formed, which reduces the strength of the seam, and it must be periodically knocked down. After the seam has cooled, it is peeled off. Places heated to high temperatures rust faster, so they require thorough corrosion protection.

Gas welding

For work it is necessary:

• oxygen balloon;
• gearbox;
• acetylene cylinder;
• spigot bars;
• torch and tips;
• hoses providing gas supply to the burner.

The welded construction requires fixing and cleaning the surface; with a metal wall thickness of 5 mm, a bevel is performed. Pre-coating the surfaces to be welded with flux will create a film that protects against oxidation and makes the seam stronger. Combustion maintains a mixture of oxygen and acetylene, with the result that the molten metal fills the gap. This method is less common due to the fact that it is more expensive, and work with gas equipment is more dangerous, and requires professional training of a gas welder.

To improve its quality allows the additive, which is selected specifically for these purposes. For pipes with thin walls, the “right-to-left” welding method is used. The filler bar is fed in front of the burner. The uniform melting of the additive and the edges makes it possible to form a reliable and neat seam. The coating of the weld with flux creates a film that protects against oxidation. Thick-walled pipes are stitched together from left to right, the additive is located behind the burner. After cooling, the seam will require improvement. Each stage requires verification of the geometry, in identifying distortions it is necessary to align the structure.

Gas burners should not be used for joining thin-walled profile butt-butt pipes due to the high temperature, since the edges of the products melt and deform.

Gas welding более затратный метод, так как покупка ацетилена значительно дороже используемого для дуговой сварки электричества. Но в отсутствие источника электропитания она становится незаменимой.

contact welding

Такой метод не имеет широкого распространения в быту и используется только профессиональными сварщиками. Он применяется в местах, где установлено специальное оборудование. Этот сложный вид сварки выполняется за счет давления электродов на детали и при одновременном пропускании электрического тока. Процесс происходит без использования присадок. contact welding обеспечивает надежное соединение кромок. Пластическая деформация от сжатия и кратковременное увеличение температуры от пропускания тока, формируют неразъемное соединение металла.

Useful tips

Welding profile pipes with their own hands has a few secrets:

1. Deformation from high temperature is more pronounced than on round pipes.
2. Melting of the metal can lead to overlap of the internal space. In the case when the hollowness of the pipes is important, you need to make sure that there are no drops of metal inside the product.
3. The end connection provokes the appearance of high voltage at the corners due to uneven heating and improper formation of metal rollers.

Having a little experience with a welding machine, you can easily weld the necessary construction of shaped tubes. Videos with explanations from professional welders will help to understand the details.

Video

This video shows how semi-automatic welding of shaped pipes is performed with welding wire:

This video is not educational. The method shown allows, without skill, to weld a rather thin butt-seam profile without burning it: