Gas pressure welding

Gas pressure welding This refers to a type of pressure welding in which the surfaces to be joined are heated with an oxy-fuel flame and then welded together using force, without the use of filler metal. This method is widely used for joining rods, rails, and pipes.

There are two methods of such welding:

• Pre-heat and compression joint;
• The connection of an already plastic state with simultaneous compression and melting.

Process gas pressure welding The process proceeds as follows: before welding, the ends of the workpiece must be cleaned of dirt, followed by a clean surface. The workpiece is heated strongly with an acetylene nozzle torch. Once the required temperature is reached, the workpieces are pressed together and welded. The fuel gas consumption for heating the joint of solid sections is 1.5 - 2.5 l/h (mm).^» for heating pipes 1.8 - 2.2 l/h. mm^»Torches uniformly heat the welded part and are divided into end-type and horseshoe-type, which use the fusion method. The heating temperature is 1150–1250°C.⁰WITH.

When gas pressure welding If welding is performed by preheating the joint, a gap is first established between the parts and the torch is ignited. The workpiece is heated until the ends melt, and axial pressure is applied, causing it to weld. To ensure precision in welding pipes and round bars, they are assembled for welding.

Even the slightest misalignment of the axes will affect the quality of the weld. When welding in a plastic state, a certain pressure is applied to the parts ready for welding and the torch is ignited, after which the workpieces are heated and simultaneously compressed. The signal to stop applying pressure is the formation of a thickening at the joint due to upsetting. High-quality clamping of the workpieces and upsetting require specialized devices of varying complexity, often hydraulically controlled.

For the process gas pressure welding necessary:

• A special multi-flame burner with tens or even hundreds of flames emanating from 0.5–0.8 mm channels. The burner's size and configuration are tailored to the shape and size of the product;
• a flammable mixture of acetylene and oxygen, which produces high temperatures in the metal, it is excellent for this purpose
• hydraulic workpiece clamping device, necessary devices

This welding method is used for joining steel pipes for gas and oil pipelines with diameters of 50–600 mm. The torch consists of two independently operating half-rings. Heating time depends only on the wall thickness of the metal, not its diameter. For example, heating time for a 6 mm wall takes approximately 1 minute, regardless of its diameter. When the process is well-organized, the part is well-prepared, and accurately calibrated, welding time can range from 3 to 5 minutes. This method allows for very high-quality and precise work, resulting in durable welds. The main disadvantage of this welding method is the approximate nature of the characteristics—namely, the upsetting time and heating temperature are determined by the eye of an experienced welder—and the uneven heating of the workpiece. Additional heat treatment is also necessary to impart the desired properties to the metal at the joint.

Advantages gas pressure welding:

• absence in the filler material;
• no need for a powerful power source;
• the quality of the seams is very high;
• inexpensive equipment.