What is a dom steel tube?

DOM steel tube, commonly known as Drawn Over Mandrel (DOM) tubing, is a high-precision, mechanically finished steel tube formed from welded “mother” tubes and cold-drawn over a mandrel to achieve superior dimensional accuracy, surface finish, and mechanical properties.

Manufacturing Process

1. Mother Tube Formation: A steel strip (commonly 1020 or 1026 carbon steel) is formed and electric-resistance-welded into a “mother tube.”

2. Flash Removal: All weld flash is mechanically removed to prepare the tube for drawing.

3. Cold Drawing Over Mandrel: The pre-finished tube is drawn through a die and over a tapered mandrel simultaneously, refining outer-diameter and inner-diameter tolerances and improving surface quality.

4. Optional Heat Treatment: Post-drawing thermal treatment (annealing or normalizing) can be applied to tailor mechanical properties such as hardness and toughness.

Key Properties and Advantages

• Dimensional Precision: Tight outer-diameter tolerances (as close as ±0.005") and high concentricity minimize downstream machining.

• Enhanced Strength: Cold drawing work-hardens the steel, delivering higher yield and tensile strengths compared to standard ERW tubing.

• Superior Surface Finish: Internal and external surfaces are smooth and scale-free, with no visible weld seam.

• Cost-Effectiveness: Balances performance and affordability relative to seamless tubing for many mechanical and hydraulic applications.

Common Applications

• Hydraulic and Pneumatic Cylinders: Tight tolerances and smooth bores ensure reliable sealing and reduced wear.

• Automotive Components: Suspension parts, chassis tubes, and steering systems benefit from DOM’s strength and consistency.

• Industrial Machinery: Roll cages, frames, and structural supports where precision and strength are critical.

Standards and Specifications

• ASTM A513 Type 5: The most common specification for cold-drawn ERW steel tubes.

• Size Range: Outer diameters from 3⁄16″ up to 14″ with wall thicknesses from 0.028″ to 0.625″; standard lengths 17–24 ft (custom lengths available).

• Material Grades: Primarily 1020 and 1026 carbon steels; alloy and stainless variants available for specialized uses.

DOM steel tubes combine the economic advantages of welded tube with performance characteristics close to seamless tubing. Their tight tolerances, excellent surface finish, and improved mechanical properties make them a preferred choice in hydraulic systems, automotive structures, and precision industrial applications.