In the classic sense, a tube mill is a kind of welded roll form system; however, not every welded roll form system is a tube mill. Tube mills are welded roll form systems that have been fine-tuned to run a specific diameter range, typically at fast speeds.
Diameter range is mentioned because a tube mill machine welds a round product. Progressive male and female roller dies (or rolls) shape the incoming strip for welding a specific diameter.
On all welded roll form systems, including tube mills, welding can occur with processes like high-frequency (HF) induction, HF contact, electric resistance, and laser beam welding. For the sake of this discussion, it is assumed that the correct welding process has been determined based on the specific material requirements.
In a tube mill, the forming machine forms the strip into a round, weldable product. The forming machine has two main parts: breakdown and fin-pass sections. Once welded, the tube can be left round, though it undergoes further forming to size it to a more accurate outside diameter.
Defining a welded roll forming system is a little more difficult. Again, in the classical sense, a tube mill is one kind of a welded roll forming system. But if someone refers to a “welded roll forming system,” that person is probably not talking about a tube mill, but other roll forming machines able to form various, often highly complex shapes to within tight tolerances.
Much like forming on the tube mill, with breakdown and fin-pass sections, welded roll forming systems have a similar forming setup, with the fin-pass section occurring in the last few stands before welding .
When working with nonround shapes, such as a step beam , the roll forming system tends to form the shape as is before welding. Some in the industry call this near-net-shape forming. Others call this the form square-weld square process. Once the shape is formed and welded, most recommend at least two additional passes to work the welded shape once more to finalize the dimensions.
In the process of manufacturing square pipes, rectangle pipes with direct shaping and molding technology, combined type rollers are used with pieces structure.
Roller sleeves are filled between roller pieces. The pieces structure is used for rollers. In the deformation region, rollers contact strip steel partially not fully, reducing the contact area and reducing the friction between strip steel and rollers accordingly.
As a result, roller consumption is little and the energy consumption of units molding is also reduced remarkably accordingly.
According to users’ needs, the machines can be designed into the multifunctional combination equipments for producing section steel, square pipes and round pipes, realizing one machine with multiple functions.
Shijiazhuang Zhonghui Cold-Forming& Pipe-Welding Equipment Co., Ltd., founded in 1997, is a new high-tech enterprise specialized in the development of welded pipe molding technology and manufacturing for the complete set of equipments of welded pipes. Its products involve liquefied natural gas tanks, production line of high-frequency longitudinal welded pipes, slitting production line, high-precision stainless steel, titanium pipes production line, production lines of cold forming sectional steel and their relevant supporting equipments.
