• Corrosion Science and Technology
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• v.19 no.3
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• pp.146-155
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• 2020

To elucidate the effect of heat inputs on phase transformation and resistance to intergranular corrosion of F316 austenitic stainless steel (ASS), thermodynamic calculations of each phase and time-temperature-transformation diagram were conducted using JMaPro simulation software, oxalic acid etch test, double-loop electrochemical potentiokinetic reactivation test (DL-EPR), field emission scanning electron microscopy with energy dispersive spectroscopy, and transmission electron microscopy analyses of Cr carbide (Cr₂₃C₆), austenite phase and ferrite phase. F316 ASS containing a relatively low C content of 0.043 wt% showed a slightly sensitized microstructure (acceptably dual structure) due to a small amount of Cr carbide precipitated at heat affected zone irrespective of heat inputs. Based on results of DL-EPR test, although heat input was increased, the ratio of I_r to I_a was only increased very slightly due to a slight sensitization. Therefore, heat inputs have little influences on resistance to intergranular corrosion of F316 austenitic stainless steel containing 0.043 wt% C.

• KEPCO Journal on Electric Power and Energy
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• v.1 no.1
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• pp.109-113
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• 2015

초임계 이산화탄소 발전 시스템 구축을 위해서는 고온, 고압의 열악한 환경에 노출되는 터빈, 열 교환기, 압축기와 같은 핵심 부품들의 내식성 평가는 반드시 수행되어야 한다. 이를 위해 후보소재 3종 Ferritic-Martensitic Steel (T92), Austenitic Steel (SS316L), Ni-based Alloy (IN738LC)를 선정하여 고온의 유사 초임계 $CO_2$ 발전 환경에서의 내식성 평가를 진행하였다. $600^{\circ}C$, $700^{\circ}C$의 2개의 온도 구간에서 $CO_2$ 분위기를 조성하여 800 시간 동안 노출시킨 뒤, Weight Change, Surface Morphology, Cross Section, Composition을 분석하였다. Cr-rich Protective Layer를 형성하는 Ni-based Alloy와 Fe/Cr-rich oxide를 형성하는 Austenitic Steel은 우수한 부식 저항성을 보인 반면에 Ferritic-Martensitic Steel은 높은 Weight Change와 Fe-rich Non-Protective Oxide가 관찰되어 상대적으로 낮은 부식 저항성을 보였다.

• International journal of steel structures
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• v.18 no.4
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• pp.1139-1152
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• 2018

Many studies on the application of stainless steels as structural materials in buildings and infra-structures have been performed thanks to superior characteristics of corrosion resistance, fire resistance and aesthetic appeal. Experimental investigation to estimate the ultimate strength and fracture mode of the fillet-welded connections of cold-formed austenitic stainless steel (STS304L) with better intergranular corrosion resistance than that of austenitic stainless steel, STS304 commonly used has carried out by authors. Specimens were fabricated to fail by base metal fracture not weld metal fracture with main variables of weld lengths according to loading direction. All specimens showed a block shear fracture mode. In this paper, finite element analysis model was developed to predict the ultimate behaviors of welded connection and its validity was verified through the comparison with test results. Since the block shear behavior of welded connection due to stress triaxiality and shear-lag effects is different from that of bolted connection, stress and strain distributions in the critical path of tensile and shear fracture section were investigated. Test and analysis strengths were compared with those by current design specifications such as AISC, EC3 and existing researcher's proposed equations. In addition, through parametric analysis with extended variables, the conditions of end distance and longitudinal weld length for block shear fracture and tensile fracture were suggested.

• Journal of Welding and Joining
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• v.17 no.3
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• pp.50-54
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• 1999

Feasibility study of the application of a developed annealed austenitic stainless steel at cryogenic temperature has been performed for membrane tank of LNG ship. Chemical properties of developed stainless steel are compared with a domestic commercial stainless steel and a foreign stainless steel which are used for LNG ships. Tensile properties at cryogenic temperature and fatigue strength at room temperature are measured for but and lap joints which are TIG welded specimens. Developed stainless steel having a small amount of titanium component shows the finest grain size in the HAZ, compared with the other stainless steel studied. Tensile strength, elongation and fatigue strength of the developed stainless steel are equal to those of the foreign stainless steel studied and are higher than the domestic commercial stainless steel studied.

• Proceedings of the KWS Conference
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• 1993.05a
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• pp.68-69
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• 1993

• Corrosion Science and Technology
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• v.14 no.4
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• pp.172-176
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• 2015

Austenitic stainless steel was investigated under cyclic loading in electrolytes with different chloride contents and pH and at different temperatures. The testing solutions were 13.2 % NaCl (80,000 ppm $Cl^-$) at $80^{\circ}C$and 43 % $CaCl_2$ (275,000 ppm $Cl^-$) at $120^{\circ}C$. In addition to S-N curves in inert and corrosive media, the fracture surfaces were investigated with a scanning electron microscope (SEM) to analyse the type of attack. The experimental results showed that a sharp decrease in corrosion fatigue properties can be correlated with the occurrence of stress corrosion cracking. The correlation of occurring types of damage in different corrosion systems is described.

• Journal of Advanced Marine Engineering and Technology
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• v.19 no.4
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• pp.42-50
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• 1995

To study the effect of welding methods on the Stress Corrosion Cracking (SCC) behavior of welded AISI type 316L and 304 austenitic stainless steel, the Slow Strain Rate Technique(SSRT) has been adopted in the boiling 45 wt% $MgCl_2$ solution. The results are as follows. 1) Welded sections are more susceptible than base metal in SCC, and the rank of SCC, and the rasistance in welding method is TIG, MIG, $CO_2$ and ARC. 2) The Ultimate tensile strength(UTS) and the strain of both base metal and welded joint are reduced as decreasing extension rate. 3) The SCC resistance of 316L base metal and welded sections are superior than that of 304. 4) The tendency of pitting and the SCC suseptibility are agreed well, and the SCC site is welded deposit section in 316L whereas HAZ in 304.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1174-1179
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• 2003

Cast austenitic stainless steel is used for several components, such as primary coolant piping, elbow, pump casing and valve bodies in light water reactors. These components are subject to thermal aging at the reactor operating temperature. Thermal aging results in spinodal decomposition of the delta-ferrite leading to increased strength and decreased toughness. This study shows that ferrite content can be predicted by use of the artificial neural network. The neural network has trained learning data of chemical components and ferrite contents using backpropagation learning process. The predicted results of the ferrite content using trained neural network are in good agreement with experimental ones.

• Proceedings of the KWS Conference
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• 2003.05a
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• pp.87-89
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• 2003

The yield strengths of austenitic stainless steel have been approximately doubled by increasing the nitrogen content. But, the increasing the nitrogen cause of increase the pressure of metal vapor inside the keyhole in electron beam welding. During welding, eruptions of keyhole often occur that cause excessive spatter, concavity, and porocity in the weld zone. Additionally the fast evaporation of nitrogen content cause of decrease the strength of weld zone. Therefore in this paper, we investigated of the weldability of electron beam welding and the change of chemical content after welding for strengthened austenitic stainless steel, measured the deformation scale of both of electron beam and narrow gap TIG and the spike fluctuation in the root.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2012.11a
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• pp.175-177
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• 2012

A corrosion resistance and hard nitrocarburized layer was distinctly formed on 310 austenitic stainless steel substrate by DC plasma nitrocarburizing. Basically, 310L austenitic stainless steel has high chromium and nickel content which is applicable for high temperature applications. In this experiment, plasma nitrocarburizing was performed in a D.C. pulsed plasma ion nitriding system at different temperatures in $H_2-N_2-CH_4$ gas mixtures. After the experiment structural phases, micro-hardness and corrosion resistance were investigated by the optical microscopy, X-ray diffraction, scanning electron microscopy, micro-hardness testing and Potentiodynamic polarization tests. The hardness of the samples was measured by using a Vickers micro hardness tester with the load of 100 g. XRD indicated a single expanded austenite phase was formed at all treatment temperatures. Such a nitrogen and carbon supersaturated layer is precipitation free and possesses a high hardness and good corrosion resistance.