-
Welding Pressure
-
Importance and Principle
Welding pressure is one of the primary parameters in the welding process. When the two sides of the pipe blank are heated to the welding temperature, under the action of extrusion pressure, common metal grains are formed, that is, mutual crystallization occurs to achieve welding. Welding pressure has a direct impact on the strength and toughness of the weld seam.
-
Impact of Improper Pressure
When the applied welding pressure is too small, the welding edges of the metal cannot be fully compressed. As a result, residual non - metallic inclusions and metal oxides in the weld seam are not easily expelled due to the insufficient pressure. This leads to a decrease in the strength of the weld seam, making it prone to cracking. For example, in the production of large - diameter straight seam steel pipes used in natural gas transportation pipelines, if the welding pressure is insufficient, the weld seam may not be able to withstand the high - pressure gas flow, resulting in leakage or even pipeline rupture, which can cause serious safety hazards and economic losses.
On the other hand, when the pressure is too high, most of the metal that has reached the welding temperature will be extruded. This not only reduces the strength of the weld seam but also generates defects such as excessive internal and external burrs or bead buildup. In the manufacturing of steel pipes for construction scaffolding, excessive welding pressure can lead to uneven surface quality of the pipes, affecting their connection strength and overall stability during use.
-
Control Methods
In practical applications, it is essential to obtain the optimal welding pressure according to different specifications. Due to possible tolerances in the width and thickness of the pipe blank, as well as fluctuations in welding temperature and welding speed, the welding extrusion pressure may need to be adjusted. The welding extrusion amount is generally controlled by adjusting the distance between the extrusion rolls. Additionally, it can also be controlled by the pipe diameters before and after the extrusion rolls. For instance, in a steel pipe manufacturing plant, real - time monitoring of the pipe diameters at different positions during the production process allows operators to make timely adjustments to the extrusion rolls, ensuring that the welding pressure remains within the optimal range.
-
Welding Speed
-
Role in the Welding Process
The welding speed is also a key parameter in the welding process, which is related to the heating system, the deformation speed of the weld seam, and the mutual crystallization rate. In high - frequency welding, the welding quality generally improves as the welding speed increases. This is because shortening the heating time narrows the width of the edge heating zone and reduces the time for the formation of metal oxides.
-
Consequences of Incorrect Speed
When the welding speed decreases, not only does the heating zone widen, but the width of the molten zone also changes with the variation of the input heat, resulting in larger internal burrs. In low - speed welding, with less input heat, welding becomes more difficult. If the welding is not carried out according to the specified values, defects are likely to occur. For example, in the production of thin - walled straight seam steel pipes for precision instruments, a slow welding speed may cause uneven heating of the pipe wall, resulting in dimensional deviations and affecting the normal operation of the instruments.
-
Optimization and Control
Therefore, in high - frequency welded pipe production, an appropriate welding speed should be selected according to different specifications, and it should be limited by the maximum welding speed allowed by the mechanical equipment and welding equipment of the device. Modern steel pipe manufacturing enterprises often use advanced control systems that can automatically adjust the welding speed based on real - time monitoring of parameters such as temperature and current, ensuring high - quality and efficient production.
-
Opening Angle
-
Definition and Significance
The opening angle refers to the angle between the two sides of the pipe blank in front of the extrusion rolls. The opening angle is related to the stability of the burning process and has a significant impact on the welding quality. When the opening angle decreases, the distance between the edges also decreases, which enhances the proximity effect. Under the same other conditions, it can increase the heating temperature of the edges, thereby increasing the welding speed.
-
Effects of Extreme Angles
However, when the opening angle is too small, the distance between the convergence point of the extrusion rolls and the center line will be extended. This causes the edges not to be extruded at the highest temperature, reducing the welding quality and increasing power consumption.
-
Adjustment Approaches
Practical production experience shows that the opening angle can be adjusted by changing the longitudinal position of the guide rolls, usually within a range of 2° - 6°. In cases where the guide rolls cannot be adjusted longitudinally, the opening angle can be adjusted by using the thickness of the guide ring or the closed pass. For example, in a steel pipe factory, through continuous experimentation and adjustment of the opening angle, the production efficiency has been increased by 15% while ensuring the quality of the weld seam, demonstrating the importance of proper control of the opening angle in the manufacturing process of straight seam steel pipes.
In conclusion, in the manufacturing process of straight seam steel pipes, welding pressure, welding speed, and opening angle are three interrelated and crucial factors. Understanding their principles, impacts, and methods of control is essential for ensuring the quality and performance of straight seam steel pipes. Steel pipe manufacturing enterprises should continuously optimize these parameters based on actual production conditions and technological requirements to improve production efficiency, reduce costs, and meet the diverse needs of different industries for straight seam steel pipes.
