Papers by Keyword: Steel Tube

Abstract: We evaluate the properties of friction welded steel tubes in terms of the relationship between microstructures and mechanical properties. For this work, steel tubes with a diameter of 60.5 mm, which has a thickness of 3.3 and 2.2 mm, was prepared by length of 170 and 70 mm, and friction welding was conducted at a rotation speed of 2,000 rpm and upset time of 5 s, respectively. Applying the friction welding led to the notable grain refinement so that average grain size was refined from 15.1 μm in base material to 4.5 μm in welded zone. These refined grains achieved the significantly enhanced microhardness (20% higher) and a slightly higher tensile strength relative to the base material, respectively. In particular, the tensile tested specimens showed the fracture aspect at the base material zone not at welded zone, which means the soundly welded state.

Abstract: Coating of steel with aluminium alloy is needed for the execution of a functional layer for corrosion protection. Some experiments have been performed on square-section tubes (50 mm x 50 mm) of S235 steel, according to EN 10 025, to be coated with 1 mm thick sheets of EN AW 5754 aluminium alloy that have been previously bended as U shaped profiles. A new experimental model of specialized equipment has been used for certain experiments to make these functional layers of aluminium alloy on steel. Firstly, friction drilling and threading by form tapping, followed by screws-mounting without nuts have been used to make such joints. Several holes have been executed by a Ø4.3 friction drilling tool, then an M5 form tap was used for threading. For friction drilling, tools with 90% tungsten carbide content and 1 micron grain size were applied. By threading, TiN coated form taps have been used. Secondly, overlap friction stir welding (FSW) has been applied, to make a functional layer of aluminium alloy on a 50 mm x 50 mm S235 steel tube. The wings of the U profiles were overlapped. A quenched FSW tool, own-made of C 45 grade steel, EN 10083, has been used for these joining tests. The joining parameters are mentioned for each process. The run of each joining process is described and the joint test samples are presented. The appearance of the screw-mounted functional layers is appropriate. The metallographic analysis has revealed adequate form of the burr formed below the hole. The burr height is 2.5 – 3.2 mm. The pattern of the M5 thread is appropriate. No defects have been detected on the holes and threads. The appearance of the FSW functional layers is adequate. Metallographic analysis shows that FSW joints of the overlapped aluminium alloy sheets are adequate, because there is no gap between these sheets. There is only a narrow gap between the aluminium alloy bottom sheet and the wall of the steel tube, which proves an appropriate positioning of the two metals. No defects were detected, except for a weld flaw, as a small and isolated cavity, with a section less than 0.1 mm², considered within the acceptance limit, according to EN 25239-5. The U shaped sheets of aluminium alloy are firmly fixed on the square steel tube, for both coating types. The mentioned processes are proposed to increase productivity in industrial technologies for series production. The processes addressed in this paper are more rapid than conventional processes. Adequate preparation of the parts to be welded, mechanization and automation allow repeatability and quality. The target applications are coated structure elements for devices, appliances, tools, welded structures or automobiles. The involved industrial areas of the applications are: manufacturing, electro-technique, construction and automotive industries. The presented processes are ecological, because they do not need lubricants or other toxic substances and do not produce chips or harmfull substances.

Abstract: Based on the data of X-ray texture and structure analysis of the material of main gas pipelines it was shown that the layerwise inhomogeneity of tubes is formed during their manufacturing. The layerwise texture inhomogeneity of steel tubes, obtained by hot rolling at the air, differs depending on variation of technological parameters of their processing in inner and outer layers, i.e. the temperature and deformation gradients, penetration of interstitial impurities into the surface layer from surrounding atmosphere etc. The thickness of the surface layer with modified texture parameters depends on the temperature of rolling and its regime. Under exploitation when stress-corrosion cracks grows and reach the layer with a modified texture, their opening is slowing down or stops because of the high mutual misorientation of grains of different layers and the necessity of changing the plane of moving cracks, what requires additional tensile stresses. Layered textures of different gas tubes were compared. It was shown that character and degree of arising inhomogeneity correlates with the tubes resistance to stress-corrosion cracking.

Abstract: This paper presents an experimental investigation about the inner set bolted joint of steel tube subject to axial pressure. In total six tests which the thickness and the length of the cross plate were considered, were conducted. The tests results showed that, the inner set bolted joint can effectively transfer axial force, but can be easy to cause stress concentration and uneven distribution of the stress at the section break. So the inner set bolted joint should be considered the shear lag effect in design. In addition, increasing the length and the thickness could increase the test efficiency.

Abstract: Band structures with pearlite and ferrite aligned as stripes can be created during the heat treatment of carbon steel. Since band structures undermine the mechanical quality of end products, it is highly important to select a process condition that will not create band structures as a result of heat treatment. This study verified the effect of temperature and cooling rate on the creation of band structures during heat treatment of 35MnB and 25Mn steel tubes for drive shafts and also considered the optimal process conditions to remove band structures or prevent their creation. The experimental results suggest that, during heat treatment of 35MnB and 25Mn steel tubes, it is most effective to ensure a cooling rate faster than furnace cooling in order to prevent band structures.

Abstract: The axial load behavior of cellular lightweight concrete-filled tube (CLCFT) columns subjected to concentric axial compression is experimentally investigated. In the study, the maximum compressive loads obtained from the experiment were compared with the values calculated using Eurocode 4 design equation. The dimension of the square column specimens 150 mm in width and 750 mm in height. The effects of the ultimate compressive strengths and wall thicknesses of the steel tubes were observed. A total of 24 specimens, including 18 CLCFT columns and 6 reference cellular lightweight concrete (CLC) columns, were tested under monotonic axial compression. From the tests, it was found that the response curves of the CLCFT columns have a linear elastic behavior up to approximately 80-90% of their maximum compressive load. The nonlinear behavior of the columns has a ductile-like with strain-softening type. Tests also showed that the maximum compressive load and ductility of the CLCFT columns are increased significantly compared to the reference columns, depending mainly on the ultimate compressive strength of the concrete and the wall thickness of the steel tube. In addition, good agreement was observed between the predicted values using the Eurocode 4 design equations for the composite column and the experimental results.

Abstract: A review on the properties of recycled aggregate concrete filled steel tubes (RACSFT) was presented, followed by the short overview on the related researches. The uniaxial mechanical behavior, flexural performance, creep performance as well as eccentric loaded behavior of RACSFT specimens were discussed. It was found that the differences between the element made of recycled aggregate concrete (RAC) and that of natural aggregate concrete (NAC) could not be ignored. The performance of the RACFST is inferior to that of natural concrete filled steel tube (CFST). But, the RACSFT can be applied into structural elements safely. Based on the test results, it was also concluded that the RACSFT is an effective method to improve the application of RAC.

Abstract: This paper is about a new steel tubular columns filled with concrete.

Abstract: From the previous researches, the author of this paper finds that the steel tube with the hexagonal section under the lateral compression has a good energy absorption property. In order to further enhance the energy absorption of the steel tube with the hexagonal section, this paper develops the polyurethane foam filled hexagonal steel tube, and through experiment, studies its characteristics of lateral compression energy absorption, and makes the comparative analysis against the hollow hexagonal steel tube. The results show that the hexagonal section steel tube filled with polyurethane foam has substantially growth in both the loads of the yield platform and the energy absorption capability.

Abstract: The X-ray method of Generalized Pole Figures was used by study of residual deformation effects in steel shell tubes for high-temperature atomic reactor. Ferritic-martensitic steel contained disperse strengthening oxide particles and their behavior under technological treatment was of essential practical interest. The used procedure estimates residual deformation effects in grains with different orientations and depicts distributions of elastic lattice distortion and interplanar spacings. Invisible oxide particles redistribute within the tube wall and strain hardening at its outer side is higher.