The Long History of Welded Steel Pipe

Over the last decade, welded steel pipe has been developed and improved so that welded steel pipe has a long history and welds can be made with consistent high quality and high productivity. And such advanced welding systems are available from several major pipeline equipment suppliers. As a matter of fact, the development of welded steel pipe can be summarized in different periods. In the 1930s, the first mechanized arc welded steel pipe was developed with a 35 degree arc with the help of angle weld preparation, stringer beads, and a narrow groove weld preparation in order to achieve side wall penetration. To be more specific, the welding head of the welded steel pipe was made with two bugs clamped on either side of the pipe and turned downwards from the 12 o'clock position to the 6 o'clock position. In the 1960s, internal welding machine was invented and used in the making of the welded steel pipe. Internal welding machine allow more than three welding torches to operate at the same time.

And external root welding techniques were developed during the same period with the advent of internal copper ring. In the 1970s, root welding techniques were used to produce the  carbon steel pipe. Previously small diameter pipes and closing welds in larger diameter lines could not be internally welded without some sort of backing. The introduction of modern power supplies with control of metal transfer has made possible the internal welding without any backing. For example, a type of surface tension transfer process can be used with a root gap to achieve high-quality root runs, which is operated by detecting both the short circuit and the incipient rupture of the metal ridge. Better quality welded steel pipe can be manufactured thanks to the adjustable welding currents. And a stable transfer can be achieved at low-heat input and with little or no spatter.

According to the long history of welded steel pipe, the original welding systems of welded steel pipe make use of torches and wire feeds. In the 1980s, a dual torch welding system on one welding bug was introduced, which has been extensively used in a number of structural steel pipe manufacturers. To be more specific, the efficiency of the welding processes determines the properties and specifications of the welded steel pipe required by the customers, which takes on increasing significance as the wall thickness and diameter of welded steel pipe increase over the years. The introduction of the gas metal arc welding process offers further possibilities to increase the productivity of welded steel pipe. This special process typically uses a single torch with two contact tips to feed two wires into a single weld pool. Thus high welding speeds as well as excellent welding results can be assured. In some case more than two tandem torches can be used on one welding bug so as to further reduce the welding times while manufacturing DSAW steel pipe.

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