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Typical seamless tube production processes are an extrusion and a rotary tube piercing. The rotary piercing process is more competitive than the extrusion process from the viewpoint of flexibility. Main components of this equipment are twin rolling mills and a plug. Twin rolling mills are installed on a skew with proper angles in two directions. These angles are called the cross angle and the feed angle. The internal crack initiation and the growth at central area of the billet are gradually progressed due to the Mannesmann effects. The feed angle affects on the position of the crack initiation in the rotary tube piercing process. Adjustable design parameters in the equipment are the feed angle and the plug insertion depth.

In this research, the rotary tube piercing equipment was developed. Finite element analyses with the plug and without the plug were carried out in order to predict the internal crack initiation position under good calculation efficiency. Ductile fracture models with the one variable equation were utilized to crack initiation criteria. The forward distance of the plug was determined to be 5 mm through the analysis. It was testified by experiments of a carbon steel billet.

A bottleneck of laboratory analysis in process industries including steelmaking plants is the low sampling rate. Inference models using only variables measured online have then been used to made such information available in advance. This study develops predictive models for key mechanical properties of seamless steel tubes, by strength, ultimate tensile strength and hardness. A plant in Brazil was used as the case study. The sample sizes of some steel tube families given namely, yield a particular property are discrepant and sometimes very small. To overcome this sample imbalance and lack of representativeness, committees of predictive neural network models based on bagging predictors, a type of ensemble method, were adopted. As a result, all steel families for all properties have been satisfactorily described showing the correlations between targets and model estimates close to 99%. These results were compared to multiple linear regression, support vector machine and a simpler neural network. Such information available in advance favors corrective actions before complete tube production mitigating rework costs in general.

Typical seamless tube production processes are an extrusion and a rotary tube piercing. The rotary piercing process is more competitive than the extrusion process from the viewpoint of flexibility. Main components of this equipment are twin rolling mills and a plug. Twin rolling mills are installed on a skew with proper angles in two directions. These angles are called the cross angle and the feed angle. The internal crack initiation and the growth at central area of the billet are gradually progressed due to the Mannesmann effects. The feed angle affects on the position of the crack initiation in the rotary tube piercing process. Adjustable design parameters in the equipment are the feed angle and the plug insertion depth.

In this research, the rotary tube piercing equipment was developed. Finite element analyses with the plug and without the plug were carried out in order to predict the internal crack initiation position under good calculation efficiency. Ductile fracture models with the one variable equation were utilized to crack initiation criteria. The forward distance of the plug was determined to be 5 mm through the analysis. It was testified by experiments of a carbon steel billet.