Abstract
The wall thickness eccentricity is one of the most important weaknesses that appears in seamless tubes production, since this imperfection is subsequently transferred downstream through the manufacturing stages until the final product. For this reason, in this article a finite element model of the rotary tube piercing (RTP) process is developed aimed at analysing the wall thickness eccentricity imperfection. Experimental data extracted from the industrial process is used for the validation of the model, including operational process variables like power consumption and process velocity, and deformation variables as elongation and longitudinal torsion, originated by axial and shear strain respectively. The cause of longitudinal torsion is also analysed. The two most important conclusions derived from this study are: (I) the longitudinal torsion of the tube is a crucial parameter for the correct model validation, and (II) the combined effect between the uneven temperature distribution of the billet and the plug bending deformation is identified as the major cause of the wall thickness eccentricity flaw.
Highlights
Seamless tubes are produced for applications with a wide range of wall thickness and diameters up to 650 mm [1]
This perforation stage is performed in rotary tube piercing (RTP) mills, but there are different configurations depending on the number and shapes of the director rolls and guiding devices
The wall thickness eccentricity developed in seamless tubes manufactured by means of rotary piercing mills has been addressed
Summary
Seamless tubes are produced for applications with a wide range of wall thickness and diameters up to 650 mm [1]. Seamless tube production technologies start with the perforation of a billet previously heated in a rotary furnace. This perforation stage is performed in rotary tube piercing (RTP) mills, but there are different configurations depending on the number and shapes of the director rolls and guiding devices. The best quality for tubes with thick wall is obtained from two rolling mills with two guiding discs of Diescher type [4]. They are considered the rolling mean with the highest forming stability but present some drawbacks, namely, the wall thickness eccentricity. The reduction of the eccentricity in the RTP process would result in a relevant improvement of both process performance and product quality
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