Alloy steel pipes and furnace tubes for petrochemical industry

The equipments and pipes serving at high temperature and pressure and the presence of hydrogen in the petrochemical industry are usually made of Cr-Mo steels.Cr9Mo pipes replacing Cr5Mo are widely used in many parts of/with high-sulfur crude oil refining equipment to meet the more demanding high temperature anticorrosion and oxidation resistance requirements.The mechanical property,creep rupture property and high temperature oxidation-resistant property of domestic Cr9Mo steel are at the same level as the similar foreign products.Three years applications indicate that domestic Cr9Mo steel can fully meet the service requirements of petrochemical industries.Finally,this paper presents the material selection guidelines for the key oil refining devices processing of low sulfur/high acid crude oil.

Effect of weld faying part groove shape on reduction of inner flash in steel pipe joints fabricated by friction welding

The groove shape of the weld faying part was investigated to obtain an ideal pipe frictiowelded joint that had a fracture in the base metal and no inner flash of it.The steel pipe had inner and outer diameters of 8.0 mm and 13.5 mm,respectively,and the weld faying surface was of a basic flat shape(butt)type.Moreover,stepped and tapered groove shapes were prepared.Pipe groove shapes were welded with a friction speed of 27.5 s_1 and a friction load of 2.79 kN.Joining phenomena during the welding process were observed,and the tensile strength of joints was evaluated.The joints,that fabricated with flat or step groove shapes,made with a friction time at which the friction torque reached the initial peak did not have the tensile strength of the base metal nor a fracture in the base metal.However,the joints fabricated with a friction time that reached past the initial peak had a large flash,and they contained a fracture in the base metal.In contrast,when joints were made with a gently tapered groove shape with a friction time reaching the time of the initial peak,they achieved a fracture in the base metal,despite having an extremely small inner flash.Therefore,the shape at the weld faying part was capable of reducing the flash exhausted from the weld interface.

Effect of Lüders Bands by Strain Ageing on Strain Distribution,Microstructure and Texture Evolution of High-Strength Pipe Steel

In this study,the high-strength pipe steel,i.e.X80,was heated at 260℃for half an hour followed by air cooling for thermal simulation of pipe coating process.During the uniaxial loading of the specified tension samples,the migration behaviour of Lüders bands and the re-distribution of stress after strain ageing heat treatment were investigated using digital image correlation.Digital image correlation was adopted to characterise the local axial and shear strain fields of samples that were extracted from different locations across the wall thickness of the high-strength pipe steel,and electron backscatter diffraction was used to compare the evolution of crystallographic texture among these locations.Other characterisation methods regarding microstructure and mechanical properties were conducted meanwhile,including optical microscopy,scanning electron microscopy and X-ray diffraction to accurately define the detailed performances that strain ageing,i.e.being heated to 260℃for half an hour,has led to.The obtained results show that the Lüders band-related microstructure,dislocation density,lattice constant and texture vary at the different locations across the wall thickness and influence the fi nal mechanical properties of the selected high-strength pipe steel.

Novel pipe-roof method for a super shallow buried and large-span metro underground station

To address the inadequacies of traditional pipe-roof methods,the steel support cutting pipe method(SSCP)—a novel pipe-roof method that improves construction security and underground space usage—is proposed.To further explore the applications of SSCP,its design scheme ought to be optimized.The failure mode and mechanical behaviors of the SSCP were investigated through laboratory experiments.Subsequently,a series of finite element models(FEMs)was established to study the deformation characteristics.Further,the parameters of the steel support of the proposed structure were optimized using fuzzy mathematics.The results indicated the ultimate bearing capacity to be 366.8 kN,and the specimen began to yield when the external load reached 70%of the ultimate value.The lon-gitudinal spacing of the steel supports,transverse steel support size,and vertical steel support size had significant effect on the vertical deformation of the steel support and the ground settlement.Finally,the optimal combination of steel supports for the SSCP structure was obtained.

Effect of core bar inserted into weld faying part to obtain an ideal pipe joint with non-generating inner flash via friction welding

In this study,the effect of core bar inserted into weld faying part to obtain an ideal pipe joint with non-generating inner flash via friction welding is described.A steel pipe with inner and outer diameters corresponding to 8.0 mm and 13.5 mm was used,and the weld faying surface was machined to a groove shape of a flat(butt)type.The core bar of various materials was inserted in the weld faying part of the pipes,and those pipes were welded with a friction speed of 27.5 s−1 and friction pressure of 30 MPa.The core bars did not decrease inner flash when joints were fabricated with a core bar of some metallic materials with melting points below that of steel;thus,they were melted during the welding process.The joint with an alumina core bar did not decrease inner flash and was crushed by generating an inner flash.However,a commercially pure tungsten(CP-W)core bar was successfully achieved for decreasing the inner flash.Additionally,all joints with a CP-W core bar did not exhibit the tensile strength of the base metal and a fracture in the base metal,when they were fabricated during the same time,the friction torque reached the initial peak.The joint exhibited a fracture in the base metal when it was fabricated with a CP-W core bar and a taper groove shape that was proposed in the previous study.Furthermore,the core bars were easily removed from the joints;thus the joint with almost no inner flash was successfully obtained.To reduce the inner flash of pipe joints,they should be fabricated with a CP-W core bar inserted into the weld faying part with a taper groove shape.