• Journal of the Korean Society for Heat Treatment
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• v.34 no.4
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• pp.171-178
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• 2021

In the present study, we comparatively investigated the microstructures of two hot-rolled stainless steel clad plates; STS 304L - low carbon steel A516-70N and STS 316L - A516-70N. The STS 304L/A516-70N clad plate (Clad_304L_Ni) had a Ni-interlayer between stainless steel and carbon steel and a 90 ㎛ thick deformation band of unrecrystallized austenite grains on the stainless steel. The STS 316L/A516-70N clad plate (Clad_316L) had no interlayer and almost fully recrystallized austenite grains. Clad_304L_Ni exhibited the thinner a decarburized layer in carbon steel and a total carburized layer in stainless steel than Clad_316L. However, a severely carburized layer in stainless steel was thicker for Clad_304L_Ni than Clad_316L. Hardness profiles near the interface of clad plates matched well with microstructures at locations where the hardness values were measured.

• Proceedings of the KWS Conference
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• 1999.05a
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• pp.288-291
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• 1999

Fatigue crack propagaion rates and characteristics of the SA516-70 steel which is used for the low temperature pressure vessels, were studied in the room temperature of 1$0^{\circ}C$ and low temperature ranges of -1$0^{\circ}C$, -3$0^{\circ}C$, -5$0^{\circ}C$, -7$0^{\circ}C$ with stress ratio of R＝0.05.

• Journal of Ocean Engineering and Technology
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• v.15 no.2
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• pp.99-104
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• 2001

Elastic-plastic fracture toughness $J_{lc}$ can be used as an effective design criterion in elastic plastic fracture mechanics. Most of these systems are$J_{lc}$ $J_{lc}$ value at high temperature must be determined for use of integrity evaluation and designing of such systems. Elastic-plastic fracture toughness $J_{lc}$ tests were performed on SA516/70 carbon steel plate and test results were analyzed according to ASTM E 813-87, ASTM E 813-89 and ASTM E 1152-87.safety and integrity are required for reactor pressure vessels because, they are operated in high temperature. There are single specimen method, which used as evaluation of safety and integrity for reactor pressure vessels. In this study, elastic-plastic fracture toughness($J_{lc}$) and J-$\Delta$a of SA 516/70 steel used as reactor pressure vessel steel are measured and evaluated at room temperature, 150$^{\circ}C $, 250$^{\circ}C $ and 370$^{\circ}C $ according to unloading compliance method.

• Corrosion Science and Technology
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• v.19 no.6
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• pp.281-287
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• 2020

Chloride ion is one of the most important corrosive agents in atmospheric corrosion, especially in marine environments. It has high adsorption rate and increases the conductivity of electrolytes. Since chloride ions affect the protective properties and the surface composition of the corrosion product, they increase the corrosion rate. A low level of chloride ions leads to uniform corrosion, whereas a high level of chloride ions may induce localized corrosion. However, higher solution temperatures tend to increase the corrosion rate by enhancing the migration of oxygen in the solution. This work focused on the effect of NaCl concentration and temperature on galvanic corrosion between A516Gr.55 carbon steel and AA7075T6 aluminum alloys. When AA7075T6 aluminum alloy was galvanically coupled to A516Gr.55 carbon steel, AA7075T6 was severely corroded regardless of NaCl concentration and solution temperature, unlike the corrosion properties of single specimen. The combined effect of surface treatment involving carbon steel and aluminum alloy on corrosion behavior was also discussed.

• Korean Journal of Materials Research
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• v.29 no.8
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• pp.511-518
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• 2019

In this study, the effect of carbon equivalent and cooling rate on microstructure and hardness of A516 steels for pressure vessel is investigated. Six kinds of specimens are fabricated by varying carbon equivalent and cooling rate, and their microstructures and hardness levels are analyzed. Specimens with low carbon equivalent consist of ferrite and pearlite. As the cooling rate increases, the size of pearlite decreases slightly. The specimens with high carbon equivalent and rapid cooling rates of 10 and $20^{\circ}C/s$ consist of not only ferrite and pearlite but also bainite structure, such as granular bainite, acicular ferrite, and bainite ferrite. As the cooling rate increases, the volume fractions of bainite structure increase and the effective grain size decreases. The effective grain sizes of granular bainite, acicular ferrite, and bainitic ferrite are ~20, ~5, and ${\sim}10{{\mu}m$, respectively. In the specimens with bainite structure, the volume fractions of acicular ferrite and bainitic ferrite, with small effective grains, increase as cooling rate increases, and so the hardness increases significantly.

• Proceedings of the KWS Conference
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• 2001.05a
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• pp.228-231
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• 2001

Elastic-plastic fracture toughness $J_{1c}$ can be used as an effective design criterion in elastic plastic fracture mechanics. Most of these systems are operated at high temperature and $J_{1c}$ values are affected by temperature. therefore, the $J_{1c}$ valuse at high temperature must be determined for use of integrity evaluation and designing of such systems. Elastic-plastic fracture toughness $J_{1c}$ tests were performed on SA516 carbon steel plate and test results were analyzed according to ASTM E 813-8, ASTM 1813-89. Safety and integrity are required for reactor pressure vessels vecause pthey are operated in high temperature. there are single specimen method, which used as evaluation of safety and integrity for reactor pressure vessels. In this study, elastic-plastic fracture toughness$(J_{1c})$ and $J-\Delta{a}$ of SA 516/70 steel used as reactor pressure vessel steel are measured and evaluated at room Temperature, $150^{\circ}C$, $250^{\circ}C$ and $370^{\circ}C$ according to unloading compliance method.

• Journal of Welding and Joining
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• v.32 no.4
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• pp.26-33
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• 2014

The metallurgical and mechanical characteristics, toughness and corrosion resistance of dissimilar welds between super duplex stainless steel UNS S32750 and carbon steel ASTM A516Gr.70 have been evaluated. Three heat inputs of 21.12, 24.00, 26.88kJ/cm were employed to make joints of dissimilar metals with flux cored arc welding(FCAW). Based on microstructural examination, vermicular ferrite was formed in the first layer of weld at low heat input(21.12kJ/cm) and $Cr_{eq}/Ni_{eq}$ of 1.61 while acicular ferrite was formed in last layer of weld at high heat input(26.88kJ/cm) and $Cr_{eq}/Ni_{eq}$ of 1.72. Ferrite percentage in dissimilar welds was lowest in the first layer of weld regardless of heat inputs and it gradually increased in the second and third layers of weld. Heat affected zone showed higher hardness than the weld metal although reheated zone showed lower hardness than weld metal due to the formation of secondary austenite. Tensile strengths of dissimilar welds increased with heat input and there was 100MPa difference. The corrosion test by ferric chloride solution showed that carbon steel had poor corrosion resistance and pitting corrosion occurred in the first layer(root pass) of weld due to the presence of reheated zone where secondary austenite was formed. The salt spray test of carbon steel showed that the surface only corroded but the amount of weight loss was extremely low.

• Journal of Welding and Joining
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• v.35 no.3
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• pp.68-74
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• 2017

Characteristics of dissimilar metal welds between alloy steel ASTM A387 Gr. 91 and carbon steel ASTM A516 Gr.70 made with Flux cored arc welding(FCAW) have been evaluated in terms of microstructure, mechanical strength, chemical analysis by EDS as well as corrosion test. Three heat inputs of 15.0, 22.5, 30.0kJ/cm were employed to make joints of dissimilar metals with E71T-1C wire. Post-weld heat treatment was carried out at $750^{\circ}C$ for 2.5 h. Based on microstructural examination, Intragranular polygonal ferrite and grainboundary ferrite were formed only in first layer of weld metal. Another layers consisted of acicular ferrite and $Widmannst{\ddot{a}}tten$ ferrite. The amount of acicular ferrite was increased with decreasing heat input and layer. Heat affected zone of alloy steel showed the highest hardness due to the formation of tempered martensite and lower bainite. Lower and upper bainite were formed in heat affected zone of carbon steel. Tensile strengths of dissimilar metal welds decreased with increasing heat inputs. Dissimilar metal welds showed a good hot cracking resistance due to the low HCS index below 4. The salt spray test of dissimilar metals welds showed that the weight loss rate by corrosion below 170 hours was decreased with increasing heat inputs due to the increase of the amount of acicular ferrite.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.3
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• pp.372-379
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• 2013

In this study, we investigated the traits of the clad metals used in hot-rolled clad steel plates. We examined the sensitization and mechanical properties of STS 316 steel plate and carbon steel (A516) under the specific circumstances of post heat treatment and whether a weld was multilayered and thick or repeated because of repairs. The test conditions were as follows. The clad steel plates were butt-welded using FCAW/SAW, and the heat treatment was conducted at $625^{\circ}C$, for 80, 160, 320, 640, or 1280 min. The change in the corrosion resistance was evaluated in these specimens. In the case of the carbon steel (A516), as the heat treatment time increased, the annealing effect caused the tensile strength to decrease. The micro- hardness gradually increased and then decreased after 640 min. The elongation and contraction of the area increased gradually. An oxalic acid etch test and EPR test on STS316, a clad metal, showed a STEP structure and no sensitization. From the test results for the multi-layered and repair welds, it could be concluded that there is no effect on the corrosion resistance of clad metals. In summary, the purpose of this study was to suggest some considerations when developing on-site techniques and evaluate the sensitization of stainless steels.

• Journal of Welding and Joining
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• v.34 no.3
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• pp.61-68
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• 2016

Characteristics of dissimilar metal welds between alloy steel ASTM A387 Gr. 91 and carbon steel ASTM A516 Gr.70 made with Flux cored arc welding(FCAW) have been evaluated in terms of microstructure, mechanical strength, chemical analysis by EDS as well as corrosion test. Three heat inputs of 15.0, 22.5, 30.0kJ/cm were employed to make joints of dissimilar metals with E91T1-B9C wire. Post-weld heat treatment was carried out at $750^{\circ}C$ for 2.5 h. Based on microstructural examination, tempered martensite and lower bainite were formed in first layer of weld metal. The amount of tempered martensite was decreased and the amount of lower bainite was increased with increasing heat input and layer. Heat affected zone of alloy steel showed the highest hardness due to the formation of tempered Martensite and lower Bainite. Tensile strengths of dissimilar welds decreased with increasing heat inputs. Dissimilar welds seemed to have a good hot cracking resistance due to the low HCS index below 4. The salt spray test of dissimilar metals showed that the corrosion rate increased with increasing heat inputs due to the increase of the amount of lower Bainite.