Laser powder bed fusion 공정으로 제조된 오스테나이트계 316L 스테인레스 강의 고온 산화 거동

황유진,위동열,김규식,이기안,Hwang, Yu-Jin,Wi, Dong-Yeol,Kim, Kyu-Sik,Lee, Kee-Ahn 한국분말재료학회 (*구 분말야금학회) 2021 한국분말재료학회지 (KPMI) Vol.28 No.2

In this study, the high-temperature oxidation properties of austenitic 316L stainless steel manufactured by laser powder bed fusion (LPBF) is investigated and compared with conventional 316L manufactured by hot rolling (HR). The initial microstructure of LPBF-SS316L exhibits a molten pool ~100 ㎛ in size and grains grown along the building direction. Isotropic grains (~35 ㎛) are detected in the HR-SS316L. In high-temperature oxidation tests performed at 700℃ and 900℃, LPBF-SS316L demonstrates slightly superior high-temperature oxidation resistance compared to HR-SS316L. After the initial oxidation at 700℃, shown as an increase in weight, almost no further oxidation is observed for both materials. At 900℃, the oxidation weight displays a parabolic trend and both materials exhibit similar behavior. However, at 1100℃, LPBF-SS316L oxidizes in a parabolic manner, but HR-SS316L shows a breakaway oxidation behavior. The oxide layers of LPBF-SS316L and HR-SS316L are mainly composed of Cr₂O₃, Fe-based oxides, and spinel phases. In LPBF-SS316L, a uniform Cr depletion region is observed, whereas a Cr depletion region appears at the grain boundary in HR-SS316L. It is evident from the results that the microstructure and the high-temperature oxidation characteristics and behavior are related.

Type 316L SS의 700°C 설계 적용을 위한 고온 피로 물성의 제시

하도현,이형연,김선진,어재혁 대한기계학회 2022 大韓機械學會論文集A Vol.46 No.12

Currently, Type 316L stainless steel (316L SS) is being used as the structural material for the hot storage tank, heat exchanger, and hot leg of the 700°C large-scale thermal energy storage verification test loop currently under construction at KAERI. In this study, various high-temperature design rules and standards applicable to pressure vessels were studied via the piping of 316L SS in a large-capacity thermal energy storage system under a design temperature of 700°C to determine the high-temperature material properties and design coefficients. The results revealed the absence of many material properties required for the application of 316L SS in high-temperature design. Therefore, to cater for the missing material properties, low-cycle fatigue tests were performed at 700°C on 316L SS with two heats, and the relevant design coefficients and fatigue strengths were proposed to allow the application of 316L SS in high-temperature designs. 현재 한국원자력연구원에서는 700°C 대용량 열에너지저장(TES) 검증 시험장치를 구축중에 있으며 고온 축열조, 열교환기 및 배관계통의 구조재료로 Type 316L 스테인리스강을 선정하였다. 본 연구에서는 설계온도 700°C의 대용량 열에너지저장 검증 시험장치 내 Type 316L강 재질의 압력기기 및 배관계통에 적용할 수 있는 고온 설계기술기준인 RCC-MRx의 고온 부재 물성과 설계계수의 결정을 위한 연구개발을 수행하였다. Type 316L 스테인리스강은 700°C 고온 구조 설계에 적용하는 데 있어 다수의 재료물성치가 부재 상태에 있다. 부재 물성을 확보하기 위해 두 가지 heat의 Type 316L 스테인리스강에 대해 700°C에서 일련의 저주기 피로시험을 통해 피로강도 물성을 결정하고, 700°C에서의 피로설계가 가능하게 하도록 관련 설계계수를 제시하였다.

MA 316L ODS 및 Wet 316L ODS 스테인리스강에서 충격에너지에 미치는 소결 공정의 영향

김성수,한창희,장진성,Kim, Sung-Soo,Han, Chang-Hee,Jang, Jin-Sung 한국분말야금학회 2010 한국분말재료학회지 (KPMI) Vol.17 No.2

Two kinds of oxide-dispersion-strengthened (ODS) 316L stainless steel were manufactured using a wet mixing process(wet) and a mechanical alloying method (MA). An MA 316L ODS was prepared by a mixing of metal powder and a mechanical alloying process. A wet 316L ODS was manufactured by a wet mixing with 316L stainless steel powder. A solution of yttrium nitrate was dried after being in the wet 316L ODS alloy. The results showed that carbon and oxygen were effectively reduced during the degassing process before the hydroisostatic process (HIP) in both alloys. It appeared that the effect of HIP treatment on increase in impact energy was pronounced in the MA 316L ODS alloy. The MA 316L ODS alloy showed a higher yield strength and a smaller elongation, when compared to the wet 316L ODS alloy. This seemed to be attributed to the enhancement of bonding between oxide and matrix particles from HIP and to the presence of a finer oxide of about 20 nm from the MA process in the MA 316L ODS alloy.

극저온 사용 소재 스테인레스강 316L의 수소취화 저항성 평가

황재식,Nguyen Le Thanh Hung,김명성,이제명 한국마린엔지니어링학회 2019 한국마린엔지니어링학회지 Vol.43 No.4

Hydrogen is currently attracting attention as a next-generation energy source. However, the phenomenon of hydrogen embrittlement is the biggest problem related to hydrogen energy. In this study, the mechanical strength of stainless steel 316L with hydrogen embrittlement (HE) conditions was analyzed. To establish an HE environment, a cathodic electrolytic method was performed with hydrogen charging time (0, 24, and 48 h) as a parameter, and a tensile test was conducted at 25, -110, and -195°C. Zinc plating was applied to prevent hydrogen from being released during the tensile test for mechanical strength analysis. To analyze hydrogen charging of hydrogen-charged stainless steel 316L, a sample taken from the specimen was melted to release hydrogen gas. The experiment confirmed that different amounts of hydrogen were charged into the stainless steel 316L particles according to the hydrogen charging time, but the decrease in the mechanical strength based on the hydrogen loading amount was very small. The study thus showed that stainless steel 316L exhibits resistance to hydrogen embrittlement in a cryogenic environment. 차세대 에너지원으로 수소가 각광받고 있는 현재, 수소에너지로 인한 가장 큰 문제점인 수소취화 현상이 주목받고 있다. 이에 따라 본 연구에서는 수소취화(Hydrogen Embrittlement, HE)조건을 적용한 스테인레스강 316L의 기계적 성능을 분석하였다. 수소취화 환경을 조성하기 위하여 수소장입시간(0h, 24h, 48h)을 변수로 음극전기분해법(Cathodic Electrolytic Method)을 수행하였으며, 온도(25℃, -110℃, -195℃)에 따른 인장시험을 진행하였다. 기계적 강도 분석을 위한 인장시험 중 수소가 방출되는 것을 방지하기 위하여 전기아연도금을 시행하였다. 수소 장입된 스테인레스강 316L의 수소 장입량을 분석하기 위하여, 시편에서 채취한 시료를 용융시켜 수소가스를 방출시켰다. 실험 결과, 수소장입시간에 따라 서로 다른 양의 수소가 스테인레스강 316L의 입자 속에 장입되었지만, 수소장입량에 따른 기계적 성능의 감소가 매우 미미함을 확인할 수 있었다. 이에 따라 스테인레스강 316L이 극저온 환경에서 수소취화에 대한 뛰어난 저항성을 확인할 수 있었다.

Type 316L 강의 고온 크리프 및 크리프 균열성장 거동

김우곤(Woo-Gon Kim),I.N.C. Kusuma,박재영(Jae-Young Park),이형연(Hyeong-Yeon Lee),김선진(Seon-Jin Kim) 대한기계학회 2018 대한기계학회 춘추학술대회 Vol.2018 No.12

The high-temperature material behaviors of type 316L stainless steel (SS), which is used for a main structural material of a sodium-cooled fast reactor (SFR), were investigated by the tension, creep, and creep crack growth tests. The tension tests were performed at R.T. to 650℃, the creep tests were performed under different applied loads at 600℃ and 550℃, and the creep crack growth (CCG) tests were conducted using 1/2-inch compact tension specimens at 600℃. The creep test data were analyzed using various creep plots and fracture microstructures, and compared with RCC-MRx. The CCG rate (CCGR) for type 316L was constructed using a C* fracture parameter, and the CCGR of type 316L was compared with those of type 316 SS and 316LN. The creep strength decreased with an increase in rupture time, and the creep rate increased with an increase in stress. The rupture ductility decreased slightly with an increase in rupture time. The present tested data showed higher creep strength than that of RCC-MRx, and marginal differences to RCC-MRx in the creep rate. In the CCGR test results, type 316L was lower in the CCGR than type 316SS, and type 316L and 316LN were almost similar in the CCGR.

조직생검용 Needle의 세라믹 코팅에 관한 연구

조성만(Sung Man Cho),정협재(Hyup Jae Chung),김만태(Man Tae Kim),이경엽(Kyong Yop Rhee) Korean Society for Precision Engineering 2009 한국정밀공학회지 Vol.26 No.9

Stainless steel 316L (STS 316L) is widely used as a material of biopsy needle. However it has a side effect that tissue can be damaged by electrochemical operation between tissue and STS 316L. Many studies have been made on the ceramic coating of biopsy needle to reduce the side effect. In this study, STS 316L was coated with three bioceramics, Al₂O₃, SiO₂ and ZrO₂ using a RF magnetron sputtering method. The effects of ceramic coating on the electrical conductivity and coating strength of ceramic-coated STS 316L were investigated. The results showed that the electrical conductivity of ceramic-coated STS 316L was much lower than that of uncoated STS 316L. The coating strength of ZrO₂-coated STS 316L was 30% and 70% higher, respectively than those of Al₂O₃-coated STS 316L and SiO₂-coated STS 316L.

Intergranular Corrosion Mechanism of Slightly-sensitized and UNSM-treated 316L Stainless Steel

( J. H. Lee ),( K. T. Kim ),( Y. S. Pyoun ),( Y. S. Kim ) 한국부식방식학회(구 한국부식학회) 2016 Corrosion Science and Technology Vol.15 No.5

316L stainless steels have been widely used in many engineering fields, because of their high corrosion resistance and good mechanical properties. However, welding or aging treatment may induce intergranular corrosion and stress corrosion cracking etc. Since these types of corrosion are closely related to the formation of chromium carbide in grain boundaries, the alloys are controlled by methods such as the lowering of carbon content, solution heat treatment. This work focused on the intergranular corrosion mechanism of slightly-sensitized and Ultrasonic Nano-crystal Surface Modification (UNSM)-treated 316L stainless steel. Samples were sensitized for 1, 5, and 48 hours at 650 ℃ in N2 gas atmosphere. Subsequently UNSM treatments were carried out on the surface of the samples. The results were discussed on the basis of the sensitization by chromium carbide and carbon segregation, the residual stress and grain refinement. Even though chromium carbide was not precipitated, the intergranular corrosion rate of 316L stainless steel was drastically increased with aging time, and it was confirmed that the increased intergranular corrosion rate of slightly-sensitized (not carbide formed) 316L stainless steel was due to the carbon segregation along the grain boundaries. However, UNSM treatment improved the intergranular corrosion resistance of aged stainless steels, and its improvement was due to the reduction of carbon segregation and the grain refinement of the outer surface, including the introduction of compressive residual stress.

316L 스테인리스강 용접부의 피로균열진전 거동 및 초음파 시험에 의한 열화특성 평가

박소순(So-Soon Park),남기우(Ki-Woo Nam),안석환(Seok-Hwan Ahn),박인덕(In-Duck Park) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.8

316L stainless steel had been used as the structural material for energy environmental facilities, because austenite stainless steels like 316L have superior mechanical properties of which toughness, ductility, corrosion resistant and etc. However, those welded structures are receiving severe damage due to increasing of the aged degradation. Most studies until now have been carried out against fatigue behaviors of weldments, and were not well studied on nondestructive evaluation methods. In this study, the fatigue crack propagation behavior of 316L stainless steel weldment usually used for vessels of the nuclear power plant was investigated. Also, the degradation characteristics of 316L stainless steel weldments were evaluated by the ultrasonic parameter such as ultrasonic velocity, attenuation factor and time-frequency analysis. The results of this study can be used as a basic data for the prediction of the fatigue crack life of weldments structures without disjointing or stopping service of structures in service.

700℃ 고온 배관에 Type 316L 스테인리스강의 적용성 분석

이형연,남기언,윤정,김현일,어재혁 대한기계학회 2024 大韓機械學會論文集A Vol.48 No.1

한국원자력연구원(KAERI)에 구축된 700℃ 대용량 열에너지저장 시스템(TESET) 내 Type 316L 스테인리스강 배관에 대해 고온 설계 및 평가를 수행하였다. 700℃ 의 소듐 냉각재가 유동하는 고온관은 루프히터, 고온 축열조, 공기-소듐 열교환기 등의 고온 기기를 연결하는 배관이다. 배관설계 기술기준인 ASME B31.1과 RCC-MRx는 크리프 영역에서 가동되는 Type 316L 스테인리스강 고온관의 설계절차를 제시하고 있다. 그러나 550℃ 에서 700℃ 사이의 온도에 대해서는 고온 배관 설계평가에 필요한 많은 재료물성이 부재인 상태로 있다. 이에 따라 본 연구에서는 설계평가를 위해 일련의 재료강도 시험을 수행하였고, 피로 및 크리프 재료 물성에 대해서는 사전 연구에서 얻은 재료 물성치 기반으로 700℃ 배관의 고온 설계와 관련하여 부족한 재료 물성 및 설계 계수를 결정하였다. 연구수행 결과 Type 316L 스테인리스강은 700℃ 냉각재가 유동하는 고온 배관계통에 제한된 시간 동안 사용이 가능한 것으로 나타났다. Elevated temperature design and evaluations on Type 316L stainless steel piping in a 700℃ large-capacity thermal energy storage verification test loop (TESET) constructed at KAERI have been conducted. The hot leg piping with sodium coolant of 700℃ connect the main components of loop heater, hot tank and air-to-sodium heat exchanger. The design rules of ASME B31.1 and RCC-MRx provide design procedures for high-temperature piping in the creep range for Type 316L stainless steel. However, many material properties needed for design evaluations are not available over the temperature of 550℃ to 700℃. A series of high-temperature material strength tests were conducted in this study, and other essential material properties from previous test works on low cycle fatigue tests and creep tests were used for the design evaluations. The lack of material properties and design coefficients were determined based on the material tests associated with high-temperature design on the 700℃ piping. It was shown that Type 316L stainless steel can be used for a limited time duration in a high-temperature piping system subjected to 700℃ coolant.

Type 316L 스테인리스강의 700°C에서의 저사이클 피로 거동 및 수명 평가

하도현,김선진,이형연,이제환 대한기계학회 2022 大韓機械學會論文集A Vol.46 No.7

This study aims to investigate the low cycle fatigue behavior of Type 316L stainless steel at a high temperature of 700°C. Type 316L stainless steel is considered as a candidate materials for a thermal energy storage (TES) system. Fully reversed strain controlled low cycle fatigue tests were conducted with to total strain ranges of 0.4%, 0.6%, 0.8%, 1.0% and 1.2% under a constant strain rate of 10-3/s at 700°C. All the total strain ranges showed an initial cyclic hardening behavior, followed by a saturation area for a certain period of time, and then fractured after cyclic softening. The low cycle fatigue life decreased as the total strain range increased. The fatigue life was evaluated by the Coffin-Manson-Basquin method, and the predicted low cycle fatigue life was found to coincide well with the experimental data. 본 연구에서는 Type 316L 스테인리스강에 대해 700°C에서의 저사이클 피로 거동 및 수명 예측을 수행하였다. Type 316L 스테인리스강은 현재 한국원자력연구원이 개발 중에 있는 대용량 고온 열에너지 저장(TES) 성능시험장치의 후보 재료 중 하나이다. 저사이클 피로시험은 700°C에서 완전 양진 변형률 제어로 수행하였으며 0.4%, 0.6%, 0.8% 1.0% 그리고 1.2%의 서로 다른 전변형률 범위에서 10-3/s의 일정한 변형률 속도로 수행하였다. 저사이클 피로수명은 전변형률 범위가 증가할수록 감소하였다. 모든 전변형률 범위에서 초기 반복 경화 거동을 나타내었으며, 이후 유지영역이 일정 기간 뒤따르며 반복 연화 후 파괴되는 현상을 보였다. 수명평가는 Coffin-Manson-Basquin 모델 기반으로 수행하였으며 예측된 저사이클 피로수명은 시험 데이터와 잘 일치하는 것으로 나타났다.