Tubes DOM

The uniform wall thickness of the DOM tubes with tighter outer and inner diameter tolerances results in maximum concentricity.

The heat treatment prior to cold drawing crystallizes the grain structure of the material and the weld seam, resulting in a homogeneous, controlled microstructure and hardness.

Cold drawing results in higher yield strength and tensile strength as well as better shaping of DOM pipes. A higher ductility is achieved by further heat treatment after cold drawing (delivery condition BK+S / stress-relieved annealed).

The surfaces of the outer and inner diameters are smoother, cleaner and denser than with other tube products. The heat treatment and the reduction of the tube cross-section during cold drawing level the weld seam and in most cases it can only be determined on the basis of the microsection.

DOM tubes can be produced within the dimensional program in an unlimited range of diameters and wall thicknesses given by changes in the mass of drawing rings and mandrels. This individual dimensional range provides the operator with material savings and lower costs by selecting a dimension that can match the mass of the finished product.

The narrow tolerances, controlled mechanical properties and smooth surface of DOM tubes lead to very good machining results and also allow further machining, such as hard chrome plating after appropriate pre-treatment.

Tempering and quenching

Mills offer tempering and quenching and tempering (Q+T) for special requirements on mechanical values and impact strength. These tubes are used in the hydraulic industry, oil drilling and production, in the automotive industry, for industrial equipment and for agricultural, construction and other equipment. This version must be specifically requested.

Surface texture

Due to the excellent surface quality of the drawn DOM tube, costs for the surface treatment of many parts can be considerably reduced. Since the tubes also have a very precise concentricity, in some cases there is no need for post-processing at all. Before cold drawing, the welded tube is carefully cleaned to obtain clean, bare inner and outer surfaces. During cold drawing, the cross-section reduction is closely monitored to achieve an even better surface quality.

Machining quality

The widespread use of DOM tubes in machined parts is due in particular to their excellent concentricity. This means that certain mechanical processes can be dispensed with, which saves costs. The machining quality corresponds approximately to that of a seamless tube of the same size and composition. A drawn DOM tube has clean bare surfaces, high strength and optimum machining capabilities. Many users have realized that their specified finishing compound is available as a DOM blank and these tubes no longer need to be machined. Even if the diameter of the finished workpiece must maintain a concentricity within narrow tolerances, only a nominal allowance for finishing any surface irregularities must be taken into account. Additional allowance for eccentricity is not necessary.

Uniform wall thickness and concentricity

Uniform wall thickness is the most important property of DOM steel tubes. Seamless tubes that are rolled by rolling a rotating heated ingot over a conical mandrel always have a spiral eccentricity because it is impossible to keep the mandrel exactly in the center of the ingot. For various technological reasons, the DOM tube does not have this eccentricity and has a very uniform wall thickness. The tube is made of high-quality, flat-rolled strip steel with small dimensional deviations. Any slight deviations of the starting material are therefore visible in the same plane over the entire tube length, so that the bore remains straight and even. DOM tubes are preferred in a variety of applications where uniform wall thickness (a prerequisite for concentricity) and straightness of the bore are important.