• Corrosion Science and Technology
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• 제14권6호
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• pp.280-287
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• 2015

The German Guidelines for stainless steel in buildings (Z.30.3-6) issued by the German Institute for Building Technology (DIBt) categorizevarious stainless steel grades into five corrosion resistance classes (CRCs). Only 21 frequently used grades are approved and assigned to these CRCs. To assign new or less commonly used materials, a large program of outdoor exposure tests and laboratory tests is required. The present paper shows theresults of stress corrosion cracking (SCC) tests that can distinguish between different CRCs. Slow strain rate tests (SSRT) were performedin various media and at different temperatures. CRC IV could be distinguished from CRC II and CRC III with a 31.3 % $Cl^-$ as $MgCl_2$ solutionat $140^{\circ}C$. CRC II and CRC III could be differentiated by testing in a 30% $Cl^-$ as $MgCl_2$ solutionat $100^{\circ}C$.

• Corrosion Science and Technology
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• 제3권4호
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• pp.154-160
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• 2004

The Sulfide Stress Corrosion Cracking (SSCC) resistance of structural steels is one of the critical concerns for the operators, material designers, and fabricators of oil-field equipment, especially treating sour gas (H2S) containing fluids. As far as its fabricators concerned, the systematic care of welding parameters should be taken to obtain comparable SSCC resistance of their weldment to that of its base material. In this respect, every different type of welding joint design for this use should be verified to be SSCC-proof with relevant test procedures. In this study, the welding parameters to secure a proper SSCC resistance of steel pipe's weldments were reviewed on the Welding Procedure Qualification Records (WPQR), which had been employed for actual fabrication of an offshore structure for oil and gas production. Based on this review, a guideline of welding parameters, such as, heat input, welding consumable for Y.S. 65 ksi class steel pipe material is proposed in terms of the NACE criteria for SSCC resistance.

• 한국재료학회지
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• 제24권1호
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• pp.53-59
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• 2014

The corrosion resistance of submerged entry nozzle (SEN) materials were investigated for high-class steel manufacturing. Composite samples were fabricated by mixing $ZrO_2$, $Al_2O_3$, MgO, mullite, spinel, and carbon. The raw materials were mixed with attrition milling, compacted in a uniaxial pressure of 200MPa and calcined at $1000^{\circ}C$ for 3 h in $N_2$ atmosphere. The bulk density and apparent porosity of the calcined samples were measured by the liquid displacement method in water using Archimedes's principle. The corrosion resistance of the samples were measured by cup test with mold powder at $1550^{\circ}C$ for 2 h. The microstructure and elemental analysis of samples were observed by scanning electron microscopy (SEM), energy dispersive spectrum (EDS), and X-ray diffraction pattern (XRD). The XRD result shows that the starting raw materials were crystalline phase. The microstructure of fabricated specimen was investigated before and after corrosion tests at $1000^{\circ}C$ and $1550^{\circ}C$ for 2h. $ZrO_2$-C composite showed good resistance in the slag corrosion test. Among the composite oxide materials, $ZrO_2-Al_2O_3$-C and $ZrO_2$-MgO-C showed better resistance than $ZrO_2$-C in the slag corrosion test. The diameter variation index of $ZrO_2$-C refractory was 16.1 at $1000^{\circ}C$ for 2 h. The diameter variation index of the $ZrO_2-Al_2O_3$-C refractory was larger than that of the $ZrO_2$-C refractory at $1550^{\circ}C$ for 2 h.

• 선박안전
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• 통권22호
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• pp.34-53
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• 2007

In the case of hull material. large sized merchant ships are made of steel, on the other hand FRP or wood are used for small sized fishing boats. At present in Korea approximately 88,500 fishing boats are in operation of which 70% are made of FRP In the meantime, stainless steel is frequently used as shaft materials of the small-size FRP fishing boat. Namely, the kinds of shaft materials are STS 304(18Cr-8Ni), STS 316(18Cr-12Ni-2.5Mo steel) and STS 630(17Cr-Ni-Nb steel)etc. Among these things, STS 304 which is the cheapest and having ordinary corrosion resistance is most widely used as 2nd class shaft material. But, using STS 304 for shaft system material of the small-size FRP fishing boat on seawater environments entails a severe corrosion which causes shaft system troubles. Particularly, the corrosions tend to be concentrated of the stern and bow side, propeller shaft surface of inside of stern tube and the boat having no stern cooling pipe line system. As a solution for those problems, research on the ways to mitigate corrosion on the part of 2nd class stainless steel shaft have been undertaken. In the result, not only clarification for the reason of corrosion of the part of stainless steel shaft used mainly for the small-size FRP fishing boat was done, but also most optimal corrosion protection system was developed by experimenting shaft's protection simulation based of the electrochemical cathodic protection principle. In addition, verification through the field test on the optimal cathodic corrosion protection method by means of aluminum sacrificial anode was carried out. In this study, effective and economical shaft's protection system is suggested to the small-size FRP fishing boat operator by substantiating the results obtained from the research on the optimal cathodic protection.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2003년도 추계학술발표대회 개요집
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• pp.103-105
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• 2003

Currently, duplex and superduplex stainless steels are widely used for piping system in offshore unit because of its excellent combination of strength and corrosion resistance properties. Also, the usage of duplex and superduplex stainless steel is steadily increasing with getting into step with development of offshore industries. In spite of excellent merits in mechanical and chemical properties of base materials, sometimes stringent requirements in welding procedure qualification and fabrication of duplex class material have regulated not only the application of various high-efficiency welding processes but also applicable welding parameters. This study is focused on hardness requirement which is known as one of the most stringent factor in duplex class material welding and this study aims to evaluate the effects of cutting and welding methodology on hardness values of duplex and superduplex stainless steel weldments.

• Journal of the Korean Wood Science and Technology
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• 제48권1호
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• pp.50-60
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• 2020

Fungi are wood-decaying organisms, and this is an important trait that should be considered in wood utilization. When fungi attack wood, it decreases the quality of the wood. The use of metal screws has become an important part of woodworking. The ability of fungi to decay wood and damage metal screws that are embedded into wood is varied. In this study, eight fungal species were evaluated with respect to their ability to decay Parashorea smythiesii and P. tomentella wood. In addition, the effect of fungi on corroding metal screws was determined using the Kolle flask method. The evaluation showed that the fungal species Schizophyllum commune, Pycnoporus sanguineus, and Polyporus arcularius were highly capable of decaying Parashorea spp. woods. The greatest wood weight loss occurred with the heartwood of P. tomentella exposed to S. commune. Based on the classification of wood resistance against fungal attack, the two Parashorea spp. were classified as moderately resistant woods (class III). Schizophyllum commune was classified as highly capable of decaying wood that was embedded with metal screws and was highly capable of corroding metal screws placed in fungi-culture media. The greatest weight of rust powder formed because of screw corrosion was obtained from screw-embedded wood exposed to S. commune. Additionally, the most severe corrosion of metal screws that were embedded into woods was caused by the activities of P. arcularius. Moreover, the average weight loss of screw-embedded wood was greater than that of unscrewed wood.

• 대한기계학회논문집A
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• 제28권4호
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• pp.453-459
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• 2004

25Cr-20Ni series strainless steels have an excellent high temperature strength high oxidation and high corrosion resistance. However, further improvement can be expected of creep strength by work hardening prior creep. In the present study, the effect of prestraining at room temperature on the creep behavior of a Class M(STS310S) and a Class A(STS310J1TB) alloy containing precipitates have been examined. Prestaining was carried out at room temperature and range of prestrain was 0.5-2.5 % at STS310J1TB and 2.0-7.0% at STS310S. Creep behavior and creep rate of pre-strained specimens were compared with that of virgin specimens. Room temperature prestraining produced the creep life that is longer than that of a virgin specimen both for STS310J1TB and STS310S when creep test was carried out at the temperature lower than recrystallization temperature. The reason for this improvement of creep life was ascribable to the interaction between dislocations and precipitates in addition to the dislocation-dislocation interaction in STS310J1TB and the dislocation-dislocation interaction in STS310S. The beneficial effect of prestraining in STS310J1TB was larger than that of STS310S.

• Journal of Welding and Joining
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• 제31권1호
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• pp.21-25
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• 2013

Aluminum alloy, Al5083-O, is one of candidate materials for the LNG storage tank, because of its excellent weldability, cryogenic characteristics, and corrosion resistance. The good weldability of Al5083-O is very important in LNG storage tank manufacturing. In this study, high current metal inert gas(MIG) welding process was used to get one pass welding of thick plate aluminum alloy. Bead on plate(BOP) welding was performed to evaluate the effect of welding conditions on the height of bead and depth of penetration. The optimum welding conditions were derived to get one pass welding of the thickness of 14.5mm. The mechanical properties of the welded joint were evaluated. The cross-sectional macro test, tensile test, and bending test satisfied the class rule.

• 한국산학기술학회논문지
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• 제11권9호
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• pp.3155-3160
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• 2010

최근 자동차 산업은 고효율 자동차의 개발에 박차를 가하고 있으며 이에 따라 차체 경량화 및 내식성 방지를 위한 고강도강 및 도금강의 사용이 증가하고 있다. 이에 따라 본 연구에서는 자동차 차체에 쓰이는 3종의 다른 강판에 대하여, 겹침 순서에 따른 용접 특성을 시뮬레이션 기법을 이용하여 분석하였다. 자동차 차체에 많이 사용되는 EDDQ 급의 도금강판 0.7t와 인장강도 440 MPa급의 440R 1.2t, 그리고 AHSS (Advanced High Strength Steel)인 DP 590 0.2t 판재에 대하여 겹치기 순서에 따른 용접 특성을 시뮬레이션 하였고, 너겟 성장 곡선 및 전류에 따른 너겟의 크기로 그 용접성을 분석하였다. 또한 용접 시 발생되는 각 접촉부의 접촉저항을 이용하여 겹침순서에 따른 너겟의 크기를 분석하였으며, 이를 통해 최적의 겹치기 순서를 제안할 수 있었다.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2003년도 추계학술대회 논문집
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• pp.100-105
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• 2003

25Cr-20Ni series strainless steel have an excellent high temperature strength, high oxidation and high corrosion resistance. However, further improvement can be creep strength by work hardening prior creep. In the present study, the effect of prestraining at room temperature on the creep behavior of a Class M(STS310S) and a Class A(STS310J1TB) alloy containing precipitates have been examined. Prestraining was carried out at room temperature and range of prestrain was $0.5{\sim}2.5$ % at STS310J1TB and $2.0{\sim}7.0$ % at STS310S. Creep behavior and creep rate of pre-strained specimens were compared with that of virgin specimens. Room temperature prestraining produced the creep life that is longer than that of a virgin specimen both for STS310J1TB and STS310S when creep test carried out at the temperature lower than recrystallization temperature. The reason for this improvement of creep life was ascribable to the interaction between dislocations and precipitates in addition to the dislocation-dislocation interaction in STS310J1TB and the dislocation-dislocation interaction in STS310S. The beneficial effect of prestraining in STS310J1TB was larger than that of STS310S.