The high temperature properties of AISI 304 stainless steel were studied. Basic data about the employed experimental equipment, testing procedures, and specimen geometry were given. The experimental setup was used to ...The high temperature properties of AISI 304 stainless steel were studied. Basic data about the employed experimental equipment, testing procedures, and specimen geometry were given. The experimental setup was used to obtain stress-strain diagrams from tensile tests at room temperature as well as several elevated temperatures. Furthermore, the specimens were subjected to short-time creep tests at various temperatures. Stress levels for creep testing were established as a percentage of yield stress. The results indicate that at lowered temperatures and lower stress levels, AISI 304 stainless steel can be used as a sufficiently creep resistant material.展开更多
以AISI304材料为例,实验研究了在高覆盖率下超声冲击处理后GNG/CG(Gradient nano-grained on the coarse-grained substrate)材料的力学性能,分析了覆盖率、应力状态、应变率对力学性能的影响。结果表明,随着覆盖率的增加,GNG/CG304不...以AISI304材料为例,实验研究了在高覆盖率下超声冲击处理后GNG/CG(Gradient nano-grained on the coarse-grained substrate)材料的力学性能,分析了覆盖率、应力状态、应变率对力学性能的影响。结果表明,随着覆盖率的增加,GNG/CG304不锈钢的屈服强度逐步提高,塑性降低,应变率敏感系数提高,双轴应力状态下变形能力提高。高覆盖率冲击处理得到的GNG/CG结构能够有效抑制NG层的局部塑性应变,从而在提高材料强度的同时,保持良好的塑性。展开更多
The effects of cryogenic cooling on cutting forces in the milling process of AISI 304 stainless steel were investigated experimentally.Cryogenic cooling was achieved by spraying liquid nitrogen to tool,chips and mater...The effects of cryogenic cooling on cutting forces in the milling process of AISI 304 stainless steel were investigated experimentally.Cryogenic cooling was achieved by spraying liquid nitrogen to tool,chips and material interfaces using a pipe with an internal diameter of 1 mm;the flow rate of liquid nitrogen was 5.2 L/min;two cutting directions（climbing and conventional milling）,two machining conditions（dry and cryogenic cooling） and four cutting speeds（80,120,160 and 200 m/min） were used in the milling process.Cryogenic cooling and cutting speed are found to be effective on cutting forces.Cutting forces and torque in cryogenic milling are higher than those in dry milling.Cutting force is increased as the cutting speed is increased.Tool fritter around insert nose radius is the main problem of climb milling method in cryogenic cooling at low cutting speeds.展开更多
The deformation behavior and formability of gradient nano-grained（GNG） AISI 304 stainless steel in uniaxial and biaxial states were investigated by means of tensile test and small punch test（SPT）. The GNG top laye...The deformation behavior and formability of gradient nano-grained（GNG） AISI 304 stainless steel in uniaxial and biaxial states were investigated by means of tensile test and small punch test（SPT）. The GNG top layer was fabricated on coarse grains（CG） AISI 304 by ultrasonic impact treatment. The results showed that the CG substrate could effectively suppress the strain localization of NC in GNG layer, and an approximate linear relationship existed between the thickness of substrate（h） and uniform true strain before necking（ε_（unif））. Grain growth of NC was observed at the stress state with high Stress triaxiality T, which led to better ductility of GNG/CG 304 in SPT, as well as similar true strain after the onset of necking（ε_（neck）） compared with coarse 304 in tensile test. Ei-values of GNG/CG 304 with different structures were nearly the same at different punch speeds, and good formability of GNG/CG 304 was demonstrated. However, punch speed and microstructure needed to be optimized to avoid much lost of membrane strain region in biaxial stress state.展开更多
The novelty of this paper is the analysis in a medium containing sulfide ion due to the generation of this ion in petroleum industries, in the refining stage (the sulfide ion is also present on the produced water). Th...The novelty of this paper is the analysis in a medium containing sulfide ion due to the generation of this ion in petroleum industries, in the refining stage (the sulfide ion is also present on the produced water). The performance of 1-hydroxyethylidene-1,1-diphosphonic acid inhibitor (HEDP) was investigated by potentiodynamic polarization, electrochemical impedance spectroscopy, and weight loss measurements in a dissolution of AISI 304 stainless steel immersed in a solution containing chloride and sulfide ions. The protection of the stainless was increased with the addition of divalent cations (Ca<sup>2+</sup>, Zn<sup>2+</sup>, and Mg<sup>2+</sup>). Potentiodynamic polarization studies have shown that the inhibitor alone has anodic protection, but the addition of Ca<sup>2+</sup> (10 mg<span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;">·</span>L<sup>-1</sup>) favors the cathodic protection, and the addition of Zn<sup>2+</sup> (20 mg<span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;">·</span>L<sup>-1</sup>) and Mg<sup>2+</sup> (10 mg<span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;">·</span>L<sup>-1</sup>) mixed-type is observed. Electrochemical impedance spectroscopy was performed at three distinct potentials: -0.3 [V <i>vs.</i> SCE], <i>E</i><sub>corr</sub> [V <i>vs.</i> SCE], and 0.1 [V <i>vs.</i> SCE]. This revealed that calcium is responsible for favoring the formation of the film and the other elements (zinc and magnesium) favor the stabilization of the protective film. Scanning electron microscopy analysis revealed that the addition of cations provided the adsorption of HEDP on the metal surface. Weight loss results showed that the presence of zinc in a solution containing HEDP favored greater inhibitor efficiency (Zn<sup>2+</sup> <i>η</i><sub>m</sub> = 85.2% and for Mg<sup>2+</sup> <i>η</i><sub>m</sub> = 70.4%).展开更多
The austenitic stainless steels usually present an excellent combination of corrosion resistance and mechanical properties such as ductility in the annealed condition and high yield strength after cold deformation. So...The austenitic stainless steels usually present an excellent combination of corrosion resistance and mechanical properties such as ductility in the annealed condition and high yield strength after cold deformation. Solution annealing in the AISI 304H is recommended before deformation process in order to improve ductility. However, long annealing during solution annealing can cause GG （grain growth） or AGG （abnormal grain growth） in the AISI 304H. In these cases, ductility is strongly decreased. Therefore, GG or AGG must be avoided during solution annealing. In this article, grain growth during solution annealing of the AISI 304H samples was determined. Samples of the AISI 304H were annealed at 1,100 ℃ for solution-annealing times varying from 15 min to 180 min. The results show that AGG took place for samples annealed at 1,100 ℃ for 30 min. In this condition, grain size reached 70 ± 10 μm. After annealing solution at 1,100 ℃ for 180 min, grain size reached 120 ~ 20 μm. In summary, the results shown that solution annealing at 1,100 ℃ even for relatively short annealing promotes the prompt increase of the grain size.展开更多
This present study applied gas tungsten arc welding in order to join AISI 304 and AISI 201 stainless steels.The objective was to find the optimum welding condition that gave a weld bead in accordance with DIN EN ISO 2...This present study applied gas tungsten arc welding in order to join AISI 304 and AISI 201 stainless steels.The objective was to find the optimum welding condition that gave a weld bead in accordance with DIN EN ISO 25817 quality level B, pitting corrosion potential of the weld metal of not less than that of the AISI304 base metal and a ratio of delta-ferrite in austenite matrix of the weld metal of not lower than 3%.Such a ratio is a criterion widely accepted to protect the weld metal from solidification cracking. At the welding current of 75 A and by using pure argon as a shielding gas 0 to 8 vol.% and applying a welding speed in the range of 2-3.5 mm·s^(-1) was found to give a complete weld bead with an increased depthper-width ratio(promote weldability). For welding speed in the range of 3 and 3.5 mm·s^(-1)(promote corrosion resistance). Increasing the welding speed in such a range decreased the amount of delta-ferrite in the austenite matrix, and increased the pitting corrosion potential of the weld metal to be 302 mV_(SCE).This value was still lower than the pitting corrosion potential of the AISI 304 base metal. Mixing nitrogen in argon shielding gas increased the nitrogen content in the weld. The optimum condition was found when using a welding speed of 3 mm· s^(-1) and mixing 1 vol.% of nitrogen in the argon shielding gas(promote weldability and corrosion resistance). Pitted areas after potentiodynamic test were observed in the austenite in which its Cr content was relatively low.展开更多
Blanking is a major process and has a wide range of usage in manufacturing industry. The general concept of blanking seems a simple one but governing parameters are many and have a complex relationship which directly ...Blanking is a major process and has a wide range of usage in manufacturing industry. The general concept of blanking seems a simple one but governing parameters are many and have a complex relationship which directly affect the quality of the produced parts （blanks） and also the energy efficiency of the process. The main problem is the lack of prediction capabilities of the effect of these parameters that lead to time, money and labor consuming trial and error procedures in experimental studies. Usage of FEM based programs to simulate blanking to obtain numerical results and observe the shearing mechanism is a cheap and a detailed way for industrial applications. In this study five different clearances （1%, 3%, 5%, 10% and 20%） and three different thicknesses （t = 2 mm, t = 3 mm and t = 4 mm） were used for simulation and experimental studies of the blanking process. Simulations were executed by using the FEM program, Deform 2-D. Investigations were made on the parameters related to crack progression like crack initiation and crack propagation angles, indentation angle, rollover angle and depth and also the related blanking energy values. The results of the present paper are in agreement with the results of experimental studies.展开更多
基金supported by the Ministry of Science and Technology of the Republic of Croatia,titled "Numerical analysis of structural response for specific service conditions" (No.069-0691736-1737)
文摘The high temperature properties of AISI 304 stainless steel were studied. Basic data about the employed experimental equipment, testing procedures, and specimen geometry were given. The experimental setup was used to obtain stress-strain diagrams from tensile tests at room temperature as well as several elevated temperatures. Furthermore, the specimens were subjected to short-time creep tests at various temperatures. Stress levels for creep testing were established as a percentage of yield stress. The results indicate that at lowered temperatures and lower stress levels, AISI 304 stainless steel can be used as a sufficiently creep resistant material.
文摘以AISI304材料为例,实验研究了在高覆盖率下超声冲击处理后GNG/CG(Gradient nano-grained on the coarse-grained substrate)材料的力学性能,分析了覆盖率、应力状态、应变率对力学性能的影响。结果表明,随着覆盖率的增加,GNG/CG304不锈钢的屈服强度逐步提高,塑性降低,应变率敏感系数提高,双轴应力状态下变形能力提高。高覆盖率冲击处理得到的GNG/CG结构能够有效抑制NG层的局部塑性应变,从而在提高材料强度的同时,保持良好的塑性。
基金the Scientific and Technological Research Council of Turkey(TUBITAK)for providing the financial support of the cryogenic machining project(Project No.106M473)
文摘The effects of cryogenic cooling on cutting forces in the milling process of AISI 304 stainless steel were investigated experimentally.Cryogenic cooling was achieved by spraying liquid nitrogen to tool,chips and material interfaces using a pipe with an internal diameter of 1 mm;the flow rate of liquid nitrogen was 5.2 L/min;two cutting directions（climbing and conventional milling）,two machining conditions（dry and cryogenic cooling） and four cutting speeds（80,120,160 and 200 m/min） were used in the milling process.Cryogenic cooling and cutting speed are found to be effective on cutting forces.Cutting forces and torque in cryogenic milling are higher than those in dry milling.Cutting force is increased as the cutting speed is increased.Tool fritter around insert nose radius is the main problem of climb milling method in cryogenic cooling at low cutting speeds.
基金Funded by the National National Natural Science Foundation of China(No.51505189)Open Project of Jiangsu Key Laboratory of Advanced Food Manufacturing Equipment&Technology(No.FM-2015-5)
文摘The deformation behavior and formability of gradient nano-grained（GNG） AISI 304 stainless steel in uniaxial and biaxial states were investigated by means of tensile test and small punch test（SPT）. The GNG top layer was fabricated on coarse grains（CG） AISI 304 by ultrasonic impact treatment. The results showed that the CG substrate could effectively suppress the strain localization of NC in GNG layer, and an approximate linear relationship existed between the thickness of substrate（h） and uniform true strain before necking（ε_（unif））. Grain growth of NC was observed at the stress state with high Stress triaxiality T, which led to better ductility of GNG/CG 304 in SPT, as well as similar true strain after the onset of necking（ε_（neck）） compared with coarse 304 in tensile test. Ei-values of GNG/CG 304 with different structures were nearly the same at different punch speeds, and good formability of GNG/CG 304 was demonstrated. However, punch speed and microstructure needed to be optimized to avoid much lost of membrane strain region in biaxial stress state.
文摘The novelty of this paper is the analysis in a medium containing sulfide ion due to the generation of this ion in petroleum industries, in the refining stage (the sulfide ion is also present on the produced water). The performance of 1-hydroxyethylidene-1,1-diphosphonic acid inhibitor (HEDP) was investigated by potentiodynamic polarization, electrochemical impedance spectroscopy, and weight loss measurements in a dissolution of AISI 304 stainless steel immersed in a solution containing chloride and sulfide ions. The protection of the stainless was increased with the addition of divalent cations (Ca<sup>2+</sup>, Zn<sup>2+</sup>, and Mg<sup>2+</sup>). Potentiodynamic polarization studies have shown that the inhibitor alone has anodic protection, but the addition of Ca<sup>2+</sup> (10 mg<span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;">·</span>L<sup>-1</sup>) favors the cathodic protection, and the addition of Zn<sup>2+</sup> (20 mg<span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;">·</span>L<sup>-1</sup>) and Mg<sup>2+</sup> (10 mg<span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;">·</span>L<sup>-1</sup>) mixed-type is observed. Electrochemical impedance spectroscopy was performed at three distinct potentials: -0.3 [V <i>vs.</i> SCE], <i>E</i><sub>corr</sub> [V <i>vs.</i> SCE], and 0.1 [V <i>vs.</i> SCE]. This revealed that calcium is responsible for favoring the formation of the film and the other elements (zinc and magnesium) favor the stabilization of the protective film. Scanning electron microscopy analysis revealed that the addition of cations provided the adsorption of HEDP on the metal surface. Weight loss results showed that the presence of zinc in a solution containing HEDP favored greater inhibitor efficiency (Zn<sup>2+</sup> <i>η</i><sub>m</sub> = 85.2% and for Mg<sup>2+</sup> <i>η</i><sub>m</sub> = 70.4%).
文摘The austenitic stainless steels usually present an excellent combination of corrosion resistance and mechanical properties such as ductility in the annealed condition and high yield strength after cold deformation. Solution annealing in the AISI 304H is recommended before deformation process in order to improve ductility. However, long annealing during solution annealing can cause GG （grain growth） or AGG （abnormal grain growth） in the AISI 304H. In these cases, ductility is strongly decreased. Therefore, GG or AGG must be avoided during solution annealing. In this article, grain growth during solution annealing of the AISI 304H samples was determined. Samples of the AISI 304H were annealed at 1,100 ℃ for solution-annealing times varying from 15 min to 180 min. The results show that AGG took place for samples annealed at 1,100 ℃ for 30 min. In this condition, grain size reached 70 ± 10 μm. After annealing solution at 1,100 ℃ for 180 min, grain size reached 120 ~ 20 μm. In summary, the results shown that solution annealing at 1,100 ℃ even for relatively short annealing promotes the prompt increase of the grain size.
基金the Thai Government scholarship given via Rajamangala University of Technology Krungthep (UTK), Bangkok, Thailand, for their financial support through this funded research project
文摘This present study applied gas tungsten arc welding in order to join AISI 304 and AISI 201 stainless steels.The objective was to find the optimum welding condition that gave a weld bead in accordance with DIN EN ISO 25817 quality level B, pitting corrosion potential of the weld metal of not less than that of the AISI304 base metal and a ratio of delta-ferrite in austenite matrix of the weld metal of not lower than 3%.Such a ratio is a criterion widely accepted to protect the weld metal from solidification cracking. At the welding current of 75 A and by using pure argon as a shielding gas 0 to 8 vol.% and applying a welding speed in the range of 2-3.5 mm·s^(-1) was found to give a complete weld bead with an increased depthper-width ratio(promote weldability). For welding speed in the range of 3 and 3.5 mm·s^(-1)(promote corrosion resistance). Increasing the welding speed in such a range decreased the amount of delta-ferrite in the austenite matrix, and increased the pitting corrosion potential of the weld metal to be 302 mV_(SCE).This value was still lower than the pitting corrosion potential of the AISI 304 base metal. Mixing nitrogen in argon shielding gas increased the nitrogen content in the weld. The optimum condition was found when using a welding speed of 3 mm· s^(-1) and mixing 1 vol.% of nitrogen in the argon shielding gas(promote weldability and corrosion resistance). Pitted areas after potentiodynamic test were observed in the austenite in which its Cr content was relatively low.
文摘Blanking is a major process and has a wide range of usage in manufacturing industry. The general concept of blanking seems a simple one but governing parameters are many and have a complex relationship which directly affect the quality of the produced parts （blanks） and also the energy efficiency of the process. The main problem is the lack of prediction capabilities of the effect of these parameters that lead to time, money and labor consuming trial and error procedures in experimental studies. Usage of FEM based programs to simulate blanking to obtain numerical results and observe the shearing mechanism is a cheap and a detailed way for industrial applications. In this study five different clearances （1%, 3%, 5%, 10% and 20%） and three different thicknesses （t = 2 mm, t = 3 mm and t = 4 mm） were used for simulation and experimental studies of the blanking process. Simulations were executed by using the FEM program, Deform 2-D. Investigations were made on the parameters related to crack progression like crack initiation and crack propagation angles, indentation angle, rollover angle and depth and also the related blanking energy values. The results of the present paper are in agreement with the results of experimental studies.
