• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2000.10a
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• pp.236-239
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• 2000

It is important to evaluate austenitic heat resistant stainless steel because of low weldability of austenitic heat resistant stainless steel containing high Si. This study took varestraint test for evaluation of solidification cracking sensitivity and Erichsen test for evaluation of weld metal ductility. As a result of tests, solidification crack sensitivity increased with adding $N_2$ to shielding gas, and W had detrimental effect on crack resistance, but Ce had beneficial effect on crack resistance. Under same heat input, ductility of weld metal increased with welding speed.

• Steel and Composite Structures
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• v.17 no.1
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• pp.105-121
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• 2014

A fundamental limitation of steel structures is the decrease in their load-bearing capacity at high temperatures in fire situations such that structural members may require some additional treatment for fire resistance. In this regard, this paper evaluates the structural stability of fire-resistant steel, introduced in the late 1999s, through tensile coupon tests and proposes some experimental equations for the yield stress, the elastic modulus, and specific heat. The surface temperature, deflection, and maximum stress of fire-resistant steel H-section columns were calculated using their own mechanical and thermal properties. According to a comparison of mechanical properties between fire-resistant steel and Eurocode 3, the former outperformed the latter, and based on a comparison of structural performance between fire-resistant steel and ordinary structural steel of equivalent mechanical properties at room temperature, the former had greater structural stability than the latter through $900^{\circ}C$.

• Transactions of Materials Processing
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• v.22 no.3
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• pp.165-170
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• 2013

High temperature deformation behavior of a heat-resistant duplex stainless steel, used as a retort in the Pidgeon process for Mg production, was investigated in this study. 25Cr-8Ni based duplex stainless steels were cast into rectangular ingots, with dimensions of $350mm{\times}350mm{\times}100mm$. Nitrogen and yttrium were added at 0.3wt.% each to enhance the heat-resistance of the steel. Phase equilibrium was calculated using the thermodynamic software FactSage$^{(R)}$ and the database of FSStel. For comparison, cast 310S steel, a widely used heat-resistant austenitic stainless steel, was also examined in this study. Dilatometry was conducted on the as-cast ingots for the temperature range from RT to $1200^{\circ}C$ and the thermal expansion coefficients were evaluated. The nitrogen addition was found to have an effect on the thermal expansion behavior for temperatures between 800 and $1000^{\circ}C$. High temperature tensile and compression tests were conducted on the ingots for temperatures ranging from 900 to $1230^{\circ}C$, which is the operation temperature employed in Mg production by the Silico-thermic reduction process. The steel containing both N and Y showed much higher strength as compared to 310S.

• Journal of the Korean Society for Heat Treatment
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• v.27 no.2
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• pp.72-78
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• 2014

Isothermal transformation behavior of a 10% Cr heat resistant steel fabricated by centrifugal casting process was investigated. Normalized specimen at $1100^{\circ}C$ for 1 hour was isothermally annealed at temperature range between $600^{\circ}C$ and $700^{\circ}C$ with various time. The annealed specimen had eutectoid structure which was generated along austenitic grain boundary during isothermal annealing. Areal fraction of eutectoid structure increased up to 25% after holding at $700^{\circ}C$ for 20 hours. It was observed that austenitic matrix was transformed to ferrite structure and fine $M_{23}C_6$ carbides with increase of annealing time. Time-temperature-transformation diagram of the centrifugally cast 10% Cr steel with 0.18 wt% C was plotted based on the results of isothermal transformation behavior.

• Journal of Power System Engineering
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• v.15 no.2
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• pp.49-54
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• 2011

Effect of tempering treatment on the mechanical properties of 12Cr heat resistant steel with ferrite phase was investigate in this study. As time and temperature of tempering treatment were increase, C and Cr contents in matrix structure were decreased. Due to increase of the amount of Cr26C6 type carbides. It was confirmed in mechanical properties experimental that tensile strength and hardness were decreased, while elongation and impact value were, increased with increasing the time and temperature.

• Journal of Power System Engineering
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• v.4 no.1
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• pp.74-80
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• 2000

This present study was investigated effect of Ni contents on the high temperature strength characteristic in 9Cr ferritic heat-resistant steel added 1.7%W in place of Mo in order to restraint laves phase formation. Precipitation amount of carbide, number of particle per unit area and particle size of carbide were decreased with increase of Ni content. In the steels, carbides of $M_{23}C_6$ type was mainly precipitated, but laves phases could not precipitated. Tensile and yield strength, creep strength and creep rupture time was decreased, but elongation were increased due to decreasing of particle number per unite area and carbide amount precipitated with increase of Ni content.

• Journal of the Korean Society for Heat Treatment
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• v.24 no.1
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• pp.23-30
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• 2011

This study was carried out to investigate the effect of aging treatment on the mechanical properties and damping capacity of 12Cr heat resistant steel with ferrite phase. While hardness values in ferrite phase was not changed, that in martensite phase was dramatically dropped in early stage of aging treatment and then gradually decreased with increase of aging time. As aging treatment was carried out, the precipitation was not detected in ferrite phase, while carbides were precipitated in martensite phase. With increasing the aging time, tensile strength eventually decreased while impact toughness increased rapidly in the early stage of aging and then gradually increased. Besides, it was confirmed that damping capacity was not changed in the early stage of aging and then gradually increased with increase of aging time.

• Fire Science and Engineering
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• v.31 no.6
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• pp.60-66
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• 2017

Steel framed building can be destroyed due to deteriation of structural stabilities in a fire. This leads a TMC Fire Resistant Steels and this study analyzed the structural stabilities such as a deflection and a reduction of maximum load capacity for the structural beams built with a TMC Fire Resistant Steel. In this study the structural stabilities were evaluated using a mechanical properties in high temperatures not only a heat transfer theory but a heat stress anlaysis with a statistically determinated beam and a statistially indeternated one. The results showed that a TMC Fire Resistant Steels demonstrated a little lower those of Fire Resistant Steels.

• Journal of the Korean Society for Heat Treatment
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• v.24 no.2
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• pp.92-98
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• 2011

The influence of the cooling condition after solution treatment on the high temperature fatigue resistance of 23Cr-26Ni heat resistant steel was investigated. Two different cooling conditions were applied to the steel after solution treatment at $1200^{\circ}C$ for 3 hours. One specimen was water quenched immediately after the solution treatment. The other one was furnace cooled at a rate of $0.5^{\circ}C/min$ down to $750^{\circ}C$ after the solution treatment. Then, both specimens were aged at $750^{\circ}C$ for 5 hours. Under two different heat treatment conditions, the low cycle fatigue (LCF) test was performed at $600^{\circ}C$ and room temperature (RT). Only cyclic hardening continued from the beginning until fracture at all strain amplitudes during LCF at $600^{\circ}C$. This phenomenon was attributed to the increase in the dislocation density due to cyclic deformation, which resulted in the interaction between the newly created dislocations and precipitates. Cyclic hardening followed by saturation and cyclic softening was observed at RT. Cyclic softening was attributed to the dislocation annihilation rate exceeding the dislocation generation rate. Other probable factor for cyclic softening was some cavities formed around grain boundaries after 20 cycles. WQ and FC have a similar LCF behavior at RT and $600^{\circ}C$ as shown in the cyclic stress response curves.

• Journal of the Korean Society for Heat Treatment
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• v.13 no.1
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• pp.27-34
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• 2000

This present study were investigated effect of Ni contents on the microstructure and strength characteristic in 9Cr ferritic heat-resistant steel added 1.7%W in place of Mo in order to restrain laves phase formation. The result obtained from this study are as follow. Volume fraction, number of particles per unite area and particle size of carbide decreased with increase of Ni contents. Other side, carbides of $M_{23}C_6$ type was mainly precipitated in this steel, but laves phases could not precipitated in spite of increasing of aging time. With increase of tempering temperature, hardness was increased, and maximum value was showed around 873k by secondary hardening due to precipitation of $W_2C$ type carbide and then, was decreased. Tensile and yield strength due to decrease precipitation amount of carbide and number of particles per unite area was decreased, but elongation and impact value was increased. In case of aged specimen after tempering than tempered specimen, strength was higher and elongation was lower due to increasing of precipitated amount of carbide and number of particles per unite area.