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A welded tube mill is a specialized production line dedicated to manufacturing longitudinally welded steel tubes. Shijiazhuang Faith Machinery Co., Ltd. specializes in the design and construction of these mills, with a particular focus on high-frequency electric resistance welding (HF ERW) technology, known for its efficiency and weld quality.
The journey in a welded tube mill starts with the pay-off and entry equipment. The steel coil is mounted on an uncoiler, and an entry guide ensures the strip feeds correctly into the leveling machine. The leveler, with its interlocking rolls, is crucial for flattening the strip and removing any residual curvature, providing a perfect blank for the forming process.
The forming section is a defining part of the mill. It consists of a tandem set of stands, each equipped with contoured rolls. These rolls are arranged in a specific sequence to gradually form the flat strip into a round tube. The design of the roll passes is engineered to guide the material smoothly, controlling the flow of the strip edges to ensure they meet perfectly at the welding point without misalignment.
The welding station is the core of the ERW process. In HF welding, an electrical current is directed to the strip edges just before they contact. This can be achieved via contact tips that touch the strip or an induction coil that induces the current without physical contact. The resistance to the current flow generates intense heat, bringing the steel edges to a plastic state. The immediate application of pressure by the squeeze rolls then forges these edges together, creating a continuous, homogenous weld seam.
Post-weld treatment is integral to the final product quality. The mill includes scarfing units to remove the internal and external weld flash. Following this, the weld area is often heat-treated through an inline normalization process to refine its grain structure and enhance mechanical properties. The tube then enters the sizing section, where a series of stands cold-work the tube to achieve its final dimensional tolerances and improve its geometric consistency.
Shijiazhuang Faith Machinery's welded tube mills are built for producing tubes that serve industries such as construction, fencing, and fluid transportation. The integration of a Programmable Logic Controller (PLC) allows for centralized monitoring and control of line speed, welding parameters, and cutting length, contributing to a stable and repeatable manufacturing process.
