Advanced Materials and Processing

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Authors: Jong Seog Lee, Chang Young Son, Chang Kyu Kim, Dae Jin Ha, Sung Hak Lee, Kwang Tae Kim, Yong Deuk Lee
Abstract: Sticking phenomenon occurring during hot rolling of ferritic stainless steels, STS 430J1L and STS 436L, was investigated in this study. The simulation test results at 900 oC and 1000 oC revealed that STS 430J1L had a smaller number of sticking nucleation sites than the STS 436L. When the test temperature was 1070 oC, the sticking hardly occurred in both stainless steels as Fe- Cr oxide layers were formed on the surface of the rolled materials. These findings suggested that the improvement of high-temperature properties of stainless steels and the appropriate rolling conditions for readily forming oxide layers on the rolled material surface were required in order to prevent or minimize the sticking.
Authors: Usik Lee, In Joon Jang, Han Suk Go, Tae Jin Kim
Abstract: This paper investigates the sound power radiated from a cracked plate. The sound power is obtained by using a lumped parameters model-based acoustics theory and vibration responses obtained by using the finite element method. It is shown that the vibration mode shapes and crack angle are closely related to the sound radiation characteristics, which can be applied to detect damages such as the cracks generated within a structure.
Authors: Yong Feng, Hao Sun
Abstract: The grade 590MPa high strength steel for construction machine and mine machine can be produced in mass and at lower cost with optimization of chemical composition and production process. The thickness of steel plates is from 6 mm to 60 mm. The microalloy system can be designed as Nb-V,Nb-Ti or Nb-Ti-V. Due to application of controlled rolling and controlled cooling (thermal mechanical control process TMCP) the properties of steel plates are perfect. Test and process simulation be conducted in lab rolling mill. The results and process were transplanted to middle plate mill and heavy plate mill, the process parameter can be matched well and appropriately, the production process is smooth and properties of steel plates are excellent and stable. The new manufacture technology for production of 590MPa high strength steels is opened up. The output of 590MPa high strength steels has been reached more than 81000 tons every year in Jinan Iron and Steel Co. Ltd. and it meet the needs of market preferably. The application of this type high strength steel can create a great of economy and social profits.
Authors: Yoshikazu Kuroda, Midori Komada, Ryo Murakami, Shingo Fukumoto, Noriyuki Tsuchida, Yasunori Harada, Kenzo Fukaura
Abstract: Ni-free austenitic steels containing high nitrogen have been developed to protect against earth resource. High nitrogen steels (HNS) have a lot of advantages, e.g., HNS have high strength, corrosion resistance, toughness, work hardening rate and large rocking parameter in the Hall-Petch equation. On the other hand, it is difficult to fabricate HNS by IM method under 0.1 MPa and to work at room temperature. We have tried to make HNS by combined use of metal injection molding method (MIM) and nitrogen absorption method. Powder compositions used was Fe-17Cr-12Mn-3Mo.The benefit of this method is to make metal parts in near net shape. In order to use this method, we should know the sintering heat schedule, timing for introducing nitrogen gas, gas pressure and setter material etc. Therefore, the shrinkage rate, density and the solution-treated microstructure of MIM compacts were examined to find out the optimum conditions.
Authors: Midori Komada, Yoshikazu Kuroda, Ryo Murakami, Noriyuki Tsuchida, Yasunori Harada, Kenzo Fukaura, Shingo Fukumoto
Abstract: Microstructure and mechanical properties of high nitrogen steels whose chemical composition were Fe-17Cr-12Mn-3Mo and that was produced by using metal injection molding method and nitrogen absorption methods were examined. A compact which is furnace cooled from 1573 K has a brittle surface layer with high chromium and nitrogen contents but the surface layer disappears when the compact is held at 1473 K. The compact which is furnace cooled at 1473 K is observed precipitates in the grains and the grain boundary, while the compact which is quenched at 1473 K shows homogeneous microstructure. In the heat treatments at 1473 K for 2, 5, and 10 h, the nitrogen content becomes higher with increasing of holding time. In the holding times of 5 and 10 h, the microstructure is austenite. In the tensile tests, tensile strength becomes larger with increasing of nitrogen content. In the specimen which is conducted the heat treatment at 1473 K for 10 h, tensile strength is about 1,000 MPa and elongation is 80 %, which shows better balance of strength and elongation than SUS304 and SUS316 steels.
Authors: Yun Ha Yoo, Jung Gu Kim
Abstract: Aqueous corrosion behaviors of Fe3Al-based iron aluminides were investigated. From the result of cyclic anodic polarization tests conducted in 3.5 wt.% NaCl solution at 25, 48, 72 and 95°C, as the temperature increased, the resistance to pitting corrosion decreased significantly, especially over the range of 25~48°C. From the result of crevice corrosion tests, no crevice corrosion occurred on FAL-Mo in the lower chloride-containing solution (200 ppm Cl-), however, FAL-Mo did not perform as well as the 304L SS in the higher chloride-containing solution (3.5 wt.% NaCl). From the result of anodic polarization tests performed in sulfur-compound solutions, additions of Cr and Mo to the Fe3Al-based iron aluminides tend to improve the aqueous corrosion resistance. Aqueous corrosion behaviors with different Al content evaluated by cyclic anodic polarization test in the chloride-containing solution exhibited the more stable passive behavior and the higher pitting resistance as Al contents increased.
Authors: Hao Liu, Ding Zhong Zhong, Long Qi Zhao, Tao Peng, Li Xin Wu, Jing Zeng
Abstract: The dilatometry curves and the critical phase transformation temperatures of high strength low-alloyed (HSLA) cold rolled sheet steel were determined by thermal simulation test machine. The samples were austenitized at 900°C,deformed at 40% of deformation and cooled at different rates of 0.1°C/s~ 60°C/s. The continuous cooling transformation (CCT) diagram under deformation condition can be drawn. The results showed that the critical phase transformation temperatures are as follows: Ac3=900°C, Ac1=735°C, Ar3=825°C, Ar1=695°C. A few amount of martensite in high strength low-alloyed cold rolled steel can be obtained at the cooling rate of 60°C/s. The experimental data provide the technical references for rolling control, cooling control and heat treatment in real production.
Authors: Wen Zhen Li, Nan Qu
Abstract: The wear properties of TFHS-1 hot work steel developed by Tsinghua University for magnesium die casting application was studied at elevated temperature with the help of GWY-2000 high temperature wear tester. The result showed that the oxidation wear is the main wear mechanism at high temperature with dry abrasion, which was also accompanied by some extent of adhesive wear and abrasive wear. Heat treatment conditions of TFHS-1 steel have an important effect on its anti-abrasion properties. In this paper, the higher temperature of tempering may result in the better wear resistance.
Authors: Yong Suk Kim, Seung Duk Kim, Sung Joon Kim
Abstract: Sliding wear mechanisms of the solution treated 18Cr-18Mn-2Mo-0.9N high nitrogen steel (HNS) were studied. Room-temperature dry sliding wear tests of the steel were carried out at various applied loads to explore the mechanism as a function of the load. The wear rate of the steel increased with the increase of the load; however, the increase rate was not constant. The rate increased slowly at low loads, rapidly at intermediate loads, and finally, the increase-rate became low again at high loads. Worn surfaces, their cross sections, and wear debris were examined, and phases of the heat-treated HNS as well as the wear debris were identified to find out the mechanism. The wear of the steel was found to be controlled by the tribo-oxidation, strain-induced phase transformation, and reverse transformation due to temperature rise on a wearing surface. The influence of each mechanism on the rate varied depending on the magnitude of the applied load.
Authors: Tai Hong Cheng, Il Kwon Oh
Abstract: The composite rotor blades have been widely used as an important part of the wind power generation systems because the strength, stiffness, durability and vibration of composite materials are all excellent. In composite laminated blades, the static and dynamic aeroelasticity tailoring can be performed by controlling laminate angle or stacking sequence. In this paper, the fluid-structure coupled analyses of 10kW wind turbine blades has been performed by means of the full coupling between CFD and CSD based finite element methods. Fiber enforced composites fabricated with three types of stacking sequences were also studied. First the centrifugal force was considered for the nonlinear static analyses of the wind turbine so as to predict the deformation of tip point in the length direction and maximum stress in the root of a wind turbine. And then, the aeroelastic static deformation was taken into account with fluid-structure interaction analysis of the wind turbine. The Arbitrary Lagrangian Eulerian Coordinate was used to compute fluid structure interaction analysis of the wind turbine by using ADINA program. The displacement and stress increased apparently with the increment of aerodynamic force, but under the condition of maximum rotation speed 140RPM of the wind turbine, the displacement and stress were in the range of safety.

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