New approach to steel pipe manufacture

Asia-Pacific accounts for a lion's share of the global demand for steel pipes and tubes, as stated by Global Industry Analysts Inc.'s market research report on Steel Pipes and Tubes. With the robust growth in Asia, developments in large-diameter steel pipe production are of great importance to pipe manufacturers.

Various possibilities can be done to improve the strength and toughness of the pipes. Seam welding is a continuous process using electrode wheels on generally overlapping workpieces. This type of welding process is suitable for producing leak tight and continuous joints in sheet metals.

Dynamics of the steel pipes and tubes industry are closely intertwined with the trends in the construction and oil and gas industries and also influenced by the pace of infrastructure development projects. Asia-Pacific is among the fastest growing markets for steel pipes and tubes due to high economic growth and increased activity in various end user sectors including oil, power, and refineries. Pipe manufacturers must take advantage of the market and in return, they need processing equipment with a future.

Seam welding
In seam welding of large-diameter steel pipe, multi-electrode SAW (submerged arc welding), or SAW using multiple welding wires, is applied. Ordinarily, the seam weld metal is used as welded. Therefore, the mechanical properties of seam weld metal are determined largely by the chemical composition of the weld metal.

On the other hand, the weld metal chemical composition is strongly influenced by the base metal since the base metal dilution rate in SAW is high. Consequently, in designing the chemical composition of weld metal, consideration is given not only to the chemical composition of the welding material but also to that of the base metal, and an alloy wire which offers optimum weld metal chemical composition is adopted.

Ordinarily, the oxygen content of SAW weld metal is kept low so as to ensure sufficient toughness of the weld metal. In the seam welding of high-strength UO pipe too, the oxygen content of the weld metal is kept low for the same purpose. In SAW, the oxygen content of the weld metal is adjusted by the flux. For high-strength UO pipe, a low-oxygen-based flux is used.

Welding seam processing machine
Due to a number of inquiries from large-pipe manufacturers, Maschinenfabrik Liezen und Gie?erei GmbH (MFL) decided to develop the unique welding seam processing machine, called RFA 24/56.

The machine removes the welding seam of large-diameter pipes by a fully automatic milling operation and improves the quality result considerably. It mills the inner and outer welding seam of large-diameter pipes over a length of 400mm. This process offers a number of advantages compared to the common, manual grinding process.

The biggest advantage is certainly that the milling process provides a much better quality of the welding seam. The quality of the welding seam is an important criterion for the delivery of large diameter tubes to important customers. In addition the complete process happens fully automatically.

Grinding pencils are needless that prevents the operator from injury. The milling process does not generate swarf and sparks. The chips are totally removed by an effective suction device. The welding seam is measured by a scanning device. By a second scanning process, the removed welding seam is recorded.

According to the different capacity requirements of the customers, MFL has developed two machine concepts. The single head solution is designed for a capacity requirement of maximum 13 tubes per hour. Both ends of the tube are processed by a 180° rotation of the machine. The double head solution is designed for a high capacity requirement of up to 24Air Jordan XX9 29 Shoes