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ERW tube mills dedicated to processing carbon steel are engineered to handle the specific characteristics of this widely used material. Shijiazhuang Faith Machinery Co., Ltd manufactures mills that transform low and mild carbon steel strips into a vast array of tubular products. The design considerations for these mills are influenced by the strength, ductility, and welding behavior of carbon steel, making them distinct from mills intended for stainless steel or non-ferrous materials.
The forming section is configured with a sufficient number of roll stands, often between 8 to 14, to gradually and smoothly shape the strip without over-straining the material. This careful formation is crucial to prevent edge wave, buckle, or other forming defects. The roll tools are typically manufactured from high-chromium alloy steel or carbon tool steel, heat-treated to achieve a high surface hardness that resists wear from the abrasive nature of carbon steel. For the welding process, high-frequency induction welding is commonly employed due to its efficiency and the clean weld it produces on carbon steel.
A key feature for many carbon steel applications is the integration of post-weld heat treatment. An inline normalizing system, consisting of an induction coil that heats the weld seam to a temperature above its recrystallization point followed by controlled air cooling, is often included. This process refines the grain structure of the weld zone and heat-affected area, bringing their mechanical properties, such as toughness and ductility, closer to that of the base material. This is particularly important for pipes destined for structural applications or subsequent cold-forming operations like bending or flaring. The mills are capable of producing pipes that conform to international standards such as ASTM A500 for structural tubing and API 5L for line pipe, covering a common size range from 1/2 inch to 24 inches in diameter.
