Seamless Steel Tube Research Articles

Heat Transfer Characteristics of a Hot‐Rolled Seamless Steel Tube During a Controlled Cooling Process

Owing to special annular section shapes, the controlled cooling technology widely used in the field of steel plates is difficult to develop successfully and apply stably in the field of steel tubes. In this research, a finite element simulation method is used to study the difference in flow field distribution between a steel plate and a steel tube with jet cooling. Combined with the heat transfer characteristics of the jet cooling process at different positions, the anisotropy of the cooling heat transfer on the outer surface of a steel tube is revealed. The heat transfer characteristics of the inner and outer walls of a high‐temperature steel tube with the condition of simultaneous cooling are further analyzed. The results show that with the increase of the steel tube rotation speed, the temperature gradient between the wall of steel tube and the center position shows a decreasing trend. With the increase of the axial water velocity, the heat transfer intensity of the inner wall shows an increasing trend. The theoretical research results are successfully applied to the research and development of online controlled cooling technology and the equipment of hot‐rolled seamless steel tubes, and this achieves good application performance.

Quenching Stress of Hot-Rolled Seamless Steel Tubes under Different Cooling Intensities Based on Simulation

Large residual stress occurs during the quenching process of hot-rolled seamless steel tubes, which results in bending, cracking, and ellipticity exceeding standards and seriously affects the quality of hot-rolled seamless steel tubes. In addition, the stress generation mechanism of hot-rolled seamless steel tubes is different from that of steel plates due to the characteristics of annular section. In this research, the finite element simulation method was used to study the quenching residual stress of seamless steel tubes with different cooling intensities. The variation law of temperature and stress on the steel tube under different cooling intensities were analyzed. The results show that the radial stress was close to 0, and the circumferential and axial stresses were the main factors affecting the quality of the steel tube. With the increase in the cooling time, the magnitude and direction of each stress component of the steel tube changed simultaneously. Finally, a typical stress distribution state of “external compressive stress, internal tensile stress” was presented in the thickness direction of the steel tube. Furthermore, with the increase in the cooling intensity, the residual stress of the steel tube gradually increased and was mainly concentrated on the near wall of the steel tube.

Microstructure evolution of transformation induced plasticity seamless steel tube in hydraulic free bulge test

AbstractIn this study the hydraulic free bulge test with an internal pressure boosting velocities of 0.5 MPa/s and punch feeding speed of 0.2 mm/s was carried out to study the microstructure evolution of the transformation induced plasticity seamless steel tube in the hydroforming process. The microstructure of the selected parts of the tube after the hydraulic free bulge test were investigated with the optical microscope and transmission electron microscope. The transformation rate of the retained austenite to martensite of the selected parts were determined by the x‐ray diffraction. To study the deformation behavior and obtain the stress‐strain state of the tube, the finite element simulation of the hydraulic free bulge test was also carried out. The results show that the retained austenite in the microstructure of all the selected parts transformed to martensite after the hydraulic free bulge test. In the center part of the tube, the highest transformation rate of 82.84 % was obtained. The retained austenites distribute inside of the ferrite grains transform to martensite firstly under the compressive stress and strain state. The retained austenites distribute at the ferrite grain boundaries start to transforme into martensite when the tube is subjected to the tensile stress and strain.

Numerical investigation of jet layout for annular jet cooling on a steel tube

Jet array layout is a crucial process parameter affecting cooling efficiency and uniformity. In this study, annular jet cooling on the surface of a seamless steel tube is numerically investigated. The main aim of this study is to examine the effect of annular jet layouts on the heat transfer and flow characteristics of jet cooling. Numerical computations were performed with two cooling media (air and water) and four jet layouts (side-by-side annular vertical jet, staggered annular vertical jet, side-by-side inclined jet, and staggered annular incline jet). The Realizable k-ε model and volume of fluid (VOF) model were used in this study. The axial Nu, circumferential Nu distribution, cooling uniformity, and cooling efficiency were comprehensively investigated. The comparison results of water-cooling show that Nu at different positions shows good consistency under air cooling but has poor cooling efficiency. Moreover, compared with the side-by-side annular vertical jet for water cooling, the staggered annular inclined jet (Nus = 190.602) exhibited poor cooling efficiency performance, with Nus reducing by 7.65%.

Der berufliche Werdegang der Mannesmann-Vorstandsvorsitzenden und ihre Arbeit im Team

Abstract The article examines the careers of the ten chairmen of the Board of Directors (CEOs) of the pioneer enterprise Mannesmann from its founding in 1890 to its takeover and dismantling by Vodafone in 2000. The company, which was originally founded to use a revolutionary invention for the production of seamless steel tubes from a solid block of steel alone by rolling, developed into an integrated vertical organized mining group of Ruhr-typical character due to reasons of market organization. As the first mining enterprise it diversified to a technology group after World War II and created a new basis as the first private provider of telecommunications services in the 1990s. Among other things, the chairmen of the Board of Directors (CEOs) were enquired about their regional and family origins, their educational background, their professional training and career, and about their specific reasons for joining Mannesmann. Finally, the article analyses the age at which this occurred, and how the rise to the top of the company took place. Particular attention is paid to their work as executives in a team as the essential basis for success and failure.<fnote>Mit Anmerkungen versehene und ergänzte Fassung eines Vortrags, gehalten anlässlich des 44. Wissenschaftlichen Symposiums der GUG «Karriere von Führungskräften innerhalb und außerhalb von Organisationen», Stuttgart 21./22. Oktober 2021.</fnote>

Numerical Simulation of Single‐Jet Impingement Cooling of a Seamless Steel Tube

Herein, numerical simulations for single‐jet impingement cooling of a heated seamless steel tube are carried out. The effect of water flow, jet height, and jet position are analyzed during numerical simulations. Water flow varies from 2 to 10 L min−1, jet height varies from 10 to 50 cm, and jet position gradually rotates from right above steel tube (α = 90°) to bottom (α = −90°). The distribution of pressure, turbulence kinetic energy, Nusselt number, and surface temperature of steel tube are obtained. This analysis reveals that water flow is an important factor affecting heat transfer efficiency. With the increase in water flow, the improvement of heat transfer efficiency gradually decreases. The cooling capacity of the steel tube in the circumferential direction is greater than that in the axial direction of the steel tube. In contrast, as the jet height gradually increases at α = 90°, the Nusselt number increases first and then decreases. In addition, the jet position also seriously affects the cooling capacity of the jet. When the jet is stationed at the top and bottom, the cooling capacity deviation between the two reaches the maximum.

Estimation of Local Plastic Deformation in a Bulk of Polycrystalline Materials

The article deals with the local plastic deformation analysis after cold forming. The technology of drawing seamless steel tubes was used to obtain cold-formed samples. The tubes were manufactured by a Tinius Olsen 300ST tensile tester with a 6 ° and 12 ° die drawn without and with an inner mandrel. Based on orientation size recalculated by stereology and applying Monte Carlo method a mathematical conversion model was developed. Implemented model together with surface measurements and structure characteristics were used to get the orientation to the size of the deformation. Thus, the actual (logarithmic) deformations and local stresses were determined. Comparison of experimentally measured values of the actual local plastic deformation with the deformation calculated found on the model simulation in the Deform program defined the significance of the differences assessed by means of a statistical T-test. All differences in the values of the local plastic deformation with respect to the position were evaluated as statistically insignificant and therefore the difference between the experimental calculation and the simulation is random.

Analysis and Control of Cracking and Wrinkling at the End of Seamless Steel Tube with Multi-Pass Large Deformation Diameter-Reducing

Axial cracking and circumferential wrinkling are found at the end of seamless steel tubes during multi-pass large deformations pushing diameter-reducing (PDR), which seriously affects product quality. However, the cracking and wrinkling mechanism of PDR has not been elucidated yet. In this paper, the Equation of circumferential residual stress at the end was deduced from the warping deformation and shear stress. It is revealed that the circumferential residual stress in the end warping area from the inner to outer surface is tensile, and the generation mechanism of circumferential wrinkling on the inner wall at the end was revealed through the deformation analysis of PDR. The geometric model of the tube with periodic alternating variation of wall thickness was established to reveal the generation and development of circumferential wrinkling. In addition, the four-pass PDR experiments and simulations were developed to reveal the influence of reducing pass and wall thickness deviation on the end warpage, unevenness and circumferential residual tensile stress. The pushing-pulling diameter-reducing (PPDR) method was proposed to control the wrinkling and cracking. The simulation and experimental results showed that the end warpage, unevenness and circumferential residual tensile stress are all greatly decreased, and the risk of axial cracking and circumferential wrinkling is eliminated.

Online Cooling System and Improved Similar Self-adaptive Strategy for Hot-rolled Seamless Steel Tube

In conventional hot-rolled seamless steel tube production, the tube was air cooled to room temperature, and the enhancing of mechanical properties mainly depends on adding alloys elements and additional offline heat treatment. Control cooling was an effective method that can obviously enhance mechanical properties and widely used in hot-rolled strip and plate production lines. To realize control cooling process, an online control cooling equipment was introduced, which can implement the efficient and uniform cooling process for annular seamless tube. Meanwhile, the controller system was built to ensure online continuous cooling process quickly and stably. In order to guarantee precise temperature control, a temperature model based on energy balance and finite difference method was proposed. In addition, a self-adaptive strategy based on improved similar tube was obtained for temperature control, which builds the self-adaptive model combining constrained one pass clustering algorithm and kNN algorithm. Finally, the proposed online control cooling system and temperature model were applied in a PQF460 hot-rolled seamless steel tube production line, which greatly improved qualification rate whilst retaining a good control precision and stability.

Evaluation of the effective temperature change in Gd-based composite wires assessed by static and pulsed-field magnetic measurements

Gd cladded in a seamless 316L austenitic steel tube has been swaged into wires by the powder-in-tube (PIT) technology, resulting in an outer diameter of 1 mm, a wall thickness of approx. 100 µm and a filling factor of around 62 vol%. Such wires provide an advantageous geometry for heat exchangers and have the benefit to protect the Gadolinium, i.e. from corrosion when being in contact with a heat transfer fluid. The magnetocaloric composite has been studied by static and pulsed magnetic-field measurements in order to evaluate the performance of Gd as a core material. By the analysis of magnetization and heat capacity data, the influences of deformation-induced defects on Gadolinium are presented. The subsequent heat treatment at 773 K for 1 h in Ar atmosphere allowed restoring the magnetic properties of the wire after deformation.Data of the pulsed magnetic-field measurements on the Gd-filled PIT-wires and a Gd–core separated from the jacket are presented, with an achievable temperature change of 1.2 K for the wire and 5.2 K for the Gd in 2 T, respectively. A comparison to previously studied La(Fe,Co,Si)13-filled composite wires is included. It indicates that performance losses due to the passive matrix material cannot be overcome only by an increased adiabatic temperature change of the core material, but instead the wire components need to be chosen regarding an optimized heat capacity ratio, as well.

Study on lifting operation of external heat extractor based on tubular balance beam

As a kind of petrochemical catalytic cracking unit, the external heat extractor is one of the key factors restricting the production schedule and time limit. In order to realize the load balance of external heat extractor in the lifting process and avoid the adverse effect of impact force on catalytic cracking performance of large equipment, a method of lifting external heat extractor with tubular balance beam was proposed. At the same time, a kind of seamless steel tube balance beam is designed according to the characteristics of the balance beam and the working conditions of hoisting. Through the stress analysis of the external heat extractor and the strength calculation of the balance beam of seamless steel tube, the rope installation point of the balance beam and the section position of the balance beam are determined, which can provide the theoretical basis and reference value for the failure analysis of large-scale lifting operations and the lifting operations of similar external heat extractor.

Numerical assessment of large hexagonal seamless steel tube extrusion feasibility

The study assesses feasibility of hot extrusion of a large seamless hexagonal 9%Cr-1%Mo steel tube. The manufacturing chain starts from a pierced cylindrical billet, hot extruded and to be further cold drawn in several passes. Preliminary industrial tests have shown thickness reduction in extrusion limited by a huge initial force peak (+25 %) reaching the press capacity. To understand this force peak, thermomechanical numerical simulation (ForgeNxt®) of the furnace-press transfer and extrusion stages is carried out. Constitutive model at high temperature, high strain and strain rate has been selected from literature. Surface properties, namely Heat Transfer Coefficient (HTC) and friction coefficient, have been made space- and time-dependent to represent glass lubrication. Numerical results are qualitatively compared to industrial experimental values to evaluate the prediction of the model. It suggests that the difficult start of the glass melting and flow along a cooled die affects the force peak. Practical improvements are suggested on this basis, together with possible refinements of the simulation for more precision and insight into extruded tube quality.

The requirements for the design and construction of a gas cylinders aimed for transportation of a compressed and liquefied gases

In this paper a typical requirements for the design and construction, workmanship and tests of a gas cylinders of water capacity between 150 l and 3000 l are described. This type of gas cylinder presents a refillable seamless steel tube aimed for transportation of compressed and liquefied gases exposed to extreme world-wide ambient temperatures. These tubes can be used alone or in batteries to equip trailers or multiple element gas containers (ISO modules or skids). When it comes about design requirements, the main focus is on the cylindrical shell thickness, which is calculated using the Lamé-von Mises formula. For some applications such as tubes assembled in batteries to equip trailers or skids (ISO modules) or MEGCs for the transportation and distribution of gases, it is important to calculate stresses associated with mounting the tube (bending stresses, torsional stresses, dynamic loadings etc.). Special attention must be paid to design of tube ends, which should be approximately hemispherical. To permit internal visual inspection of the tube, an adequate opening must be provided at the neck ends. The tubes are manufactured from seamless steel tubing, typically hot rolled, extended/extruded or forged. The ends of tube are hot formed using either forging or spinning methods. After manufacturing process, each tube must be inspected in terms of surface imperfections. Next, each tube must be ultrasonically examined for internal and external defects and laminar imperfections and to determine wall thickness. Batch tests for checking the quality of tubes includes mechanical testing, such as tensile and impact testing. Beside the batch tests, all tubes must be subjected to the following tests: a hydraulic proof pressure test or a volumetric expansion test, a hardness test, a visual inspection, a visual check of the stamp markings, a dimensional inspection and an ultrasonic non-destructive testing (NDT). At the end of this paper, the most commonly found manufacturing imperfections are pointed out.

On the collapse of thick-walled pipes with corrosion defects under external pressure

Corrosion defect is considered to be one of the major critical damages of subsea pipelines, which can result in a considerable loss in the collapse capacity of thick-walled pipes in deep waters. In this paper, collapse experiments on 13 small-scale seamless steel tubes with varying sizes of elliptical and rectangular corrosion defects were carried out in a sealed hyperbaric chamber. The collapse pressure and deformed configurations were obtained, with four types of collapse trajectories identified. A numerical framework was established to simulate the collapse event using ABAQUS, and decent consistency of the collapse pressure and collapsed configurations was observed between numerical and experimental results. Then, the collapse pressure of thick-walled pipes with a single elliptical corrosion defect was studied parametrically, covering different defect sizes, geometric characteristics, and material properties. Based on the extensive numerical analysis, a reasonable empirical formula was developed to estimate the collapse pressure of thick-walled steel pipes with various elliptical corrosion defects and material properties.

Prediction of Mechanical Properties of Seamless Steel Tubes Using Artificial Neural Networks

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.

Effect of the Friction and Reduction Angle on the Accuracy of Cold Drawing Steel Tubes STL Model Based on FEM Analysis

Abstract The object of the study was to create a computer model that resembles the process of cold drawing seamless steel tubes, and evaluate the influence of selected process parameters on selected final dimensions and tolerances of STL models of the tubes obtained from DEFORM simulation software. The STL models of tubes generated from the simulations were evaluated, and the effects of the reduction angle and the friction coefficient on the inner/outer diameter, inner/outer roundness and concentricity were subsequently found. It was proven that the inner and outer diameters are not influenced by different values of the friction coefficient at the same reduction angle. On the other hand, increasing value of the reduction angle affects decrease of the outer and inner diamaters after drawing. Furthermore, this experimental investigation vindicates that friction coefficient and reduction angle have the minimal impact on the inner/outer roundness and outer concentricity.

Axial compressive performance of steel tube columns filled with steel fiber-reinforced high strength concrete containing tire aggregate after exposure to high temperatures

The performance of concrete-filled steel tube (CFST) columns including scrap-tire rubber under compression and in particular changes in their behavior after thermal treatment has remained mostly understudied. This has led to the lack of the use of rubberized concrete in these columns. This study attempted to examine the post-heating performance of CFST columns subject to several temperatures (20, 250, 500, and 750 °C) with regard to the amount of scrap-tire rubber aggregate used as a volume fraction of sand (0, 5, and 10%), quantity of steel fibers in volume (0, 1, and 1.5%), and the ratio of the outer diameter to thickness of the steel tube (43 and 25.4). The specimens had high-strength concrete cores and seamless steel tubes. The total number of manufactured confined and unconfined cylindrical specimens was 114, which were then exposed to heat and axial compressive testing. Through these tests, the loading capacity, ductility, toughness, and compressive load-strain curves of different specimens were explored. Based on the results, although including the scrap-tire aggregate (by 10%) in the concrete mixture lowered the strength of the confined specimens (by 12%), thermal treatment had no particular increasing effect on this decline. Furthermore, as the quantity of steel fibers and the thickness of the steel tube in the heated and non-heated CFST specimens increased, toughness increased in all the specimens, and the ductility had an ascending trend in most specimens. In addition, the optimum quantity of steel fibers used here was 1%. In this regard, although the fibers affected the compressive strength of the CFST specimens negligibly, they demonstrated a considerable improving effect on the ductility and absorbed energy in all specimens particularly the heated ones. Up to 250 °C, the decline in strength was negligible, while above this temperature, this decline in strength was much more considerable, and also, the post-peak slope of all the curves decreased. Finally, due to the importance of predicting the strength of CFST columns after exposure to heat, a relationship for predicting the loading capacity of these columns under heat was proposed and the associated results were compared with the experimental results of this work as well as the experimental results reported by others. Good consistency was seen between the predicted and experimental results.

Numerical Simulation of Material Plastic Deformation Using the Drawing Forming Process of Contoured Internal Surface Tubes

Production of multi-rifled seamless steel tubes employing cold draw process using multi-rifled mandrel is quite a modern technology. The important characteristic of the tube drawing process, unlike the tube with internal rifling, is the corner filling which influences the dimension accuracy of the internal shape of the tube. In this study, the influence of drawing tool dimensions and mandrel shape on to final rifling filling was investigated. Draw process has been simulated by using the three-dimensional rigid-plastic finite element method (FEM) by using DEFORM 3D software. The results of numerical simulation show that the shape of drawing tools and process conditions have a significant influence on the forming process and final shape and properties of the workpiece.

Using 2D/3D FEM Simulation to Determine Drawing Force in Cold Drawing of Steel Tubes with Straight Internal Rifling

The most comprehensive steel tube portfolio is used to produce all kinds of modern energy production and the corresponding auxiliary unit such as boilers and heat exchangers. Multi-rifled seamless steel tubes are distinguished by maximum pressure, heat resistance, strength and durability. Production of multi-rifled seamless steel tubes by cold draw process using multi-rifled mandrel is quite a new technology. Shape and dimension of the drawing tool depend on drawing tube reduction degree, i. e. on the original diameter of the initial tube and final diameter of the tube. The technology of drawing tubes is influenced by process parameters, dimensions of tools and cold forming process conditions. Optimization of the whole forming process naturally involve the FEM analyses and simulation. One of the most important information of the cold drawing process is the load stroke of the tools. The contribution is concerned at the usability of FEM simulation on an evaluation of cold draw forming process condition and prediction of load stroke of the forming tools. DEFORM 2D/3D FEM software is used to compare the result of the drawing force and to determine the appropriate methodology to set FEM simulation of cold forming.

Model-based Residual Stress Design in Multiphase Seamless Steel Tubes.

Residual stresses in quenched seamless steel tubes highly depend on the cooling conditions to which the tubes have been subjected. The design aspect of how to use controlled cooling strategies in multiphase steel tubes to achieve certain residual stress and phase configurations is discussed. In an experimentally validated finite element (FE) model considering a coupled evolution of martensite and bainite, three cooling strategies are tested for a low-alloyed 0.25 wt.% C steel tube. The strategies are (i) external cooling only, (ii) internal and external cooling for low residual stresses in a mainly martensitic tube, and (iii) internal and external cooling with low cooling rate for a mainly bainitic tube. The strategies represent design cases, where low residual stresses with different phase compositions are provoked, in order to show the potential of numerical analysis for residual stress and property design. It can be concluded that, for the investigated steel class, intense external cooling leads to a characteristic residual stress profile regardless of the dimension. A combination of external and internal cooling allows a more flexible design of residual stress and phase distribution by choosing different cooling parameters (i.e., water amount and cooling times). In general, lower cooling rates lead to lower thermal misfit strains, and thus less plasticity and lower residual stresses.