Abstract: The construction overviews of nuclear power plants in recent years in China and the results of localization of seamless tubes for nuclear power were introduced. Aiming at the strategy of using the third generation nuclear power technology, which is represented by AP1000, to construct nuclear power plants, the technical requirements of seamless steel tubes for the third generation nuclear power plants were brought forward, and some issues related with quality control, product development and standard production were put forward to be concerned in the process of seamless tube localization for nuclear power.
Abstract: For improving the impact toughness of A333Gr. 3 cryogenic seamless tubes, the chemical composition, hazardous element, gas content, rolling state mechanical properties, metallographic structure and mechanical properties of three kinds of cryogenic seamless steel tubes after heat treatment were analyzed and compared. Carbon content has obvious influence on the low-temperature impact toughness of the steel tubes. The lower the carbon content is, the higher the impact toughness is. The brittle transition temperature can be obviously improved by the phosphorus content of the steel, so the phosphorus content of the steel should be reduced. At the same time, the rolling temperature of the steel tubes should be controlled, the finishing rolling temperature of the steel tubes should be reduced, the cooling velocity should be enhanced, and the grain size should be refined. These measures are beneficial to enhance the low-temperature impact toughness of the steel tubes.
Abstract: The characteristics and unsolved problems of API threaded OCTG were introduced. On the base of the usage and development experience of domestic oil field and manufactures, the premium threaded connections developed by Wuxi Seamless Pipe Co. Ltd (WSP) were described in detail. At the same time, the design principle, selection method and structure feature of WSP premium connections were discussed and analyzed according to the different service conditions. Furthermore, the deficiencies of WSP premium connections were also given, and the development direction was discussed too. Some references can be provided for selection and usage of premium connections.
Abstract: HR3C seamless steel tubes were produced by hot-extrusion and cold rolling processes. The process of metal cold-forming and the performance of finished-products indicate that hot-extrusion and cold rolling processes have obvious advantage in manufacturing finished-products of high alloy steel with hard deformation. Metal withstands three-dimensional compressive stress during deformation in the hot-extrusion process, which can improve the comprehensive performance of metal pipes. The improvement of surface quality and dimension precision through cold rolling processing can ensure the higher safety of materials used in special environment.
Abstract: The influence of nitrogen and oxygen contents on the microstructure and performance of HCM2S steel was studied by the room temperature tensile test of 4-furnace HCM2S steel tubes after being normalized and tempered, microstructure observation, and energy dispersive spectrum analysis. The results show that when the mass fraction of nitrogen is larger than 71 × 10-6, the depletion of useful boron and the reduction of harden ability will take place, which would affect the microstructure and performance of the steel. The fluctuation of the mass fraction of oxygen in the range of 16 × 10-6 to 49 × 10-6 has no influence on the microstructure and performance of HCM2S steel, when the nitrogen content is no more than 71 × 10-6. Addition of a little titanium will cause the reaction with nitrogen, save the content of useful boron, and obtain the bainite structure and excellent mechanical properties even with higher nitrogen content.
Abstract: This paper discussed the development trend of ultra-supercritical units for power plant boilers in China and their requirements for materials. In response to this trend, researches on the key materials used in ultra-supercritical boilers were performed in Baosteel Iron & Steel Co. Ltd. Experiment data and materials production indicate that Baosteel is able to supply materials used in complete units for the key components of 600℃ ultra-supercritical boiler heating surfaces, such as water-cooled walls, superheaters and reheaters, which can displace the imported materials and narrow the gap between boiler materials in China and oversea. According to development requirements for 700℃ ultra-supercritical units in China, the selection, development and evaluation of materials used in high-temperature parts were carried out in order to support the development of domestic ultra-supercritical units.
Abstract: Excellent mechanical properties of 27SiMn hydraulic support can be achieved by heat treatment. In this paper heat treatment orthogonal experiments with four factors and three levels were performed to investigate the effects of quenching temperature and holding time as well as tempering temperature and holding time on the mechanical properties of the hydraulic support. The heat treatment process was optimized as quenching after holding at 930℃ for 40 min and then tempering at 480℃ for 50 min. At these optimized heat treatment parameters, the hydraulic support has excellent comprehensive mechanical properties:the yielding strength of 895 MPa, the tensile strength of 1 030 MPa, the elongation of 15%, the area reduction of 54%, and the impact energy of 53. 3 J, which meet the requirements of 27SiMn steel according to the standard GB/T 17396-1998.
Abstract: Scanning electron microscopy (SEM), X-ray diffraction (XRD) and compressive tests at room temperature and elevated temperatures were used to investigate the effect of solution and aging treatments on the microstructure and mechanical properties of a Ni50Ti44Al6 alloy. The microstructure of the alloy includes NiTi matrix phase and a reticular structure which precipitates on grain boundaries. With the rising of solution treatment temperature, parts of the reticular structure vanish, and the second phase dissolves into the matrix and distributes more homogeneously. With the prolonging of aging time, the strength of the alloy firstly increases and then decreases. Heat treatment can obviously improve the mechanical properties of the alloy. The optimal heat treatment regime was obtained as follows:solution treatment at 1 150℃ for 6 h, water-cooling and then aging at 700℃ for 6 h.
Abstract: To solve the problems of rolling along the line of long thick-walled drill collar tubes (the ratio of outer diameter and wall thickness (D/S) ≤ 3. 7) in Assel mill and promote the uniform of wall thickness, a series of technical measures were carried out, such as optimizing the billet properly, distributing the deformation reasonably, adjusting the parameters of piercer and Assel mill, and optimizing the pass parameters and the speed setting of the reducing mill. The length of finished drill collar tubes completely meets the standard, and the uniform of wall thickness in transversal and longitudinal directions reaches the higher standard. The user experience shows that, the use of tubes as raw materials is better than that of bars in saving materials, promoting the pass rate, improving the efficiency, and reducing the tool consumption.
Abstract: The final carbon control of a 45-t electric arc furnace was studied, the melting process and oxygen system were optimized, and the foaming slag process was improved. Therefore, the pass rate of carbon content in the molten steel is obviously improved in the end of oxidation in EAF, the addition of deoxidizing material is reduced, and the oxygen content decreases to some extent in LF. By improving the foaming slag process, there is almost no cold steel on EAF roof, the leakage of water-cooling parts decreases greatly, and the hot stopping time is reduced.
Abstract: The interface of carbon steel and high chromium cast iron clad pipes achieved metallurgical bonding by centrifugal casting. Finite element simulation was used to study the temperature fields of the outer layer and inner/outer layer. The results showed that the minimum temperature of outer layer casting (20 steel) reached 1430℃ after centrifugal casting for 9 s, which is lower than the solidus temperature (1490℃). A steady-regular transition layer can be formed when the interval of casting was 9 s. When the temperature of 20 steel reduced to 1 350℃, the high chromium cast iron was cast. After 30 s, the inner temperature reduced to 1 257℃ which is below the solidus temperature of high chromium cast iron, then the solidification finished completely.
Abstract: Based on the deformation characteristics of steel tubes in the process of skew rolling, finite element software ANSYS/LS-DYNA was applied to simulate the rolling process of hot-rolled austenitic seamless steel tubes by Accu-Roll pipe mill. The deformation characteristics of tube section and the variation law of rolling force and strain-stress were obtained by finite element analysis. The simulation results were compared with the measured data, and the model was proved to be reliable. The results of simulation show that the unfitted shape of pass can bring out the overlap; during the rolling process, the maximum rolling stress is 403. 4 MPa, and the maximum equivalent stress is 231. 8 MPa.
Abstract: A finite element model of retained mandrel service process in 340MPM (Multi-Stand Pipe Mill) was built to research the temperature field change of the mandrel. The thermal stress of the mandrel was also studied to analyze the initiation mechanism and propagation law of fatigue cracks in the mandrel. A comparison between the measured data and the simulation results indicates that the model can reflect the temperature change of the mandrel. After the mandrel was detached from the tube, the highest temperature of the mandrel surface went up to 630℃. Then the mandrel went through three times of temperature-falling in water-cooling stages and three times of temperature-rising in air-cooling stages. At the end of the whole cooling process, the highest temperature of the mandrel surface was 98℃. Both the axial compressive stress and circumferential compressive stress reached to 900 MPa after the mandrel was detached from the tube. At the end of the 3rd water-cooling stage, the axial stress reached to 186 MPa, while the circumferential stress reached to 221 MPa. Cyclic thermal stress could lead to crack initiation and propagation in the mandrel, yet circumferential cracks would be significantly blocked at the place of 17. 5 mm away from the surface, while axial cracks would be significantly blocked at the place of 20 mm away from the surface. The impetus for axial cracks which came from thermal stress was stronger than that for circumferential cracks.
Abstract: Based on the traditional collapse mechanism, technical characteristics of Baosteel anti-collapse casing series were introduced, highlighting on alloying design, texture distribution, high strength-toughness mechanisms and casing string design. The collapse resistance mechanisms were researched from the points of grain refining, precipitation strengthening, and texture optimizing. Three-stage corrosion behavior of the casing series in H2S saturated aqueous brine solutions was proposed. A prediction model of collapse strength was finally constructed for the casing series.
Abstract: Based on piercing with a φ158 mm plug in a φ180 mm continuous rolling unit, 15Cr2Ni3MoW steel was selected as the plug material, and the smelting and casting processes were improved to decrease the casting flaws and increase the density of the plugs. After optimizing the heat treatment process, well-structured and organized oxide film overlays were found in the plugs. The metallurgical structures, flaws and inclusions in every production stage were observed and analyzed by metallographic microscopy and scanning electron microscopy. The service life testing of products in the φ180 mm continuous rolling unit shows a satisfied result.
Abstract: X65 line pipe continuous casting billet surfaces were analyzed by optical microscopy, scanning electron microscopy and energy dispersive spectrometry to deal with their defects of longitudinal depression and cracks. It is found that causes for these surface defects are mainly due to carbonitride segregation of micro alloying elements Nb, Ti and V at grain boundaries. These surface defects can be efficiently improved through optimizing the mold flux composition and the second cooling curve, controlling the tundish superheat, regulating the continuous casting operation process and checking the continuous casting equipment timely.
Abstract: Based on the full knowledge of the casing service conditions of steam injection wells for dense oil, we designed a kind of heat-resistant & lower dilatation steel. The technical route is adding some kinds of alloy elements and rare earths into Cr-Mo steel to strengthen the grain boundary. The experimental results in laboratory show that it is more advantageous in aspects of high temperature tensile properties and dilatation than C-Mn steel. This steel fits to the service conditions of steam injection wells for dense oil and may be used to the special casing production.
Abstract: During the rolling process, there is cracking in the some parts of 27SiMn seamless steel tubes for hydraulic supports. The chemical composition of the steel tube was checked, and the microcosmic analysis was conducted by metallurgical microscope and electric scanning microscopy. It is concluded that nonmetal inclusions in the continuous casting billet destroyed the structural succession of the material, and microcracks formed in this zone because of uneven stress during the rolling process. The high-speed of elevated temperature during the reheating process, increases the temperature gradient in the radial direction, tangential pulling stress forms at the outer surface because of the volume contract produced by the microstructure transform, and microcrack propagation leads to the local cracking of the tube. The paper qualitatively analyzed the inclusions, traced back to the source and provided appropriate measures for improvement.
Abstract: Macroscopic and microscopic analyses were conducted for 9 typical bursting incidents in hydraulic tests of seamless pipe production. The analysis results show that bursting in the hydraulic tests is always related to some defects existing in some parts of pipes. Defects in continuous casting billets include surface cracks, surface slag and surface carburetion, surface copper infiltration, central segregation and internal inclusion segregation, etc. Defects existing in hot rolled pipes include surface scratches, ununiformity or reduction of wall thickness, and so on. Defects caused by tube processing include surface quench cracks, abnormal microstructure, low yield strength and low precision of thread machining of pipe ends. Suggestions for improvements are also provided according to the analysis results
Monthly, started in 1955 Supervising institution：Ministry of Education Sponsoring Institution：University of Science and Technology Beijing Editorial office：Editorial Department of Chinese Journal of Engineering Publisher：Science Press Chairperson：Ren-shu Yang Editor-in-Chief：Ai-xiang Wu ISSN 2095-9389CN 2095-9389
