• Journal of the Korean Society for Heat Treatment
• /
• v.12 no.1
• /
• pp.40-46
• /
• 1999

Rotary bending fatigue tests were carried out to investigate the improvement of fatigue limit in annealed and austempered spheroidal graphite cast iron. Main results obtained are as follows. (1) The tensile strength(hardness) of Series C is higher than that of Series B, and fatigue limits are 245MPa in Series C, 230MPa in Series B and 195MPa in Series A, respectively. (2) The fatigue limits of Series B and Series A are mainly governed by the resistance to fatigue crack initiation. Whereas, the fatigue limit of Series C is governed by the resistance to fatigue crack initiation and growth. The defect size and the resistance to crack initiation and growth should be considered to clarify the fatigue properties in spheroidal graphite cast iron. (3) Improvement of fatigue limit by half-austempering is more reasonable than that of full-austempering treatment in multi defective materials as spheroidal graphite cast iron.

• Journal of Korea Foundry Society
• /
• v.32 no.2
• /
• pp.81-85
• /
• 2012

The effects of section size and melt holding time on the mechanical properties and microstructure of high silicon ductile cast iron were investigated. The strength, elongation and hardness of the test specimen with smaller cross-section were higher than those with larger one. The nodule count and volume fraction of pearlite of the former were higher than those of the latter. The mechanical properties decreased with increased melt holding time before pouring. Nodularity and nodule count decreased and the volume fraction of pearlite rather slightly increased with it.

• Journal of Korea Foundry Society
• /
• v.8 no.4
• /
• pp.429-436
• /
• 1988

The influences of some casting conditions on bonding ratio and state at bonding zone of stainless steel-cast iron dual tube produced by centrifugal casting process were investigated to estimate fabrication technics. 1) Bonding ratio is increasing such as increasing of inner surface temperature of outer metal(stainless steel STS 304), if pouring temperature of inner metal (cast iron) is constant. 2) The more pouring temperature of inner metal (cast iron) increase, the more bonding ratio increase when inner surface temperature of outer metal (cast iron) is constant. 3) As the mold rotary speed is increase, the hatching area of bonding map (perfect bonding area) goes down to the low pouring temperature of inner metal. 4) In order to predict bonding state of two different metal, we are able to make and use the bonding map about casting conditions such as inner surface temperature of outer metal, pouring temperature of inner metal and mold rotary speed.

• Journal of Korea Foundry Society
• /
• v.29 no.2
• /
• pp.86-94
• /
• 2009

The effect of austenitizing temperature and time on the processing window of 3.60wt%C - 2.50wt%Si - 0.80wt%Cu ductile cast iron and that of the amount of copper added were investigated. The second stage reaction at 400oC was retarded with increased austenitizing temperature. The widest processing window was obtained at the lower austempering temperature with the increased time at the same austenitizing temperature. The width of the widest processing window was decreased with the increase of time at the same austenitizing temperature. The width of processing window was increased with the increased amount of copper added.

• Journal of Korea Foundry Society
• /
• v.6 no.4
• /
• pp.277-283
• /
• 1986

The effects of copper as an alloying element on the microstructure of Compacted Vermicular graphite cast iron which was treated with Mg-REM spheroidizer have been studied. With the increase of copper content up to 2.0wt.%, the following results were obtained; First, the ratio of residual magnesium content in the as-cast iron has been found to be increased, possibly due to the decrease of sulfur content in the melt. Thus, the morphology of graphite in the as-cast iron has been found to be more nodular type. Second, the proportion of pearlite in the matrix has been found to he increased, however the matrix being with free carbide precipitates in the copper range of 1.2wt.% to 2.0wt.%. Third, the tensile strength of the as-cast iron in the temperature up to $400^{\circ}C$ was increased.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
• /
• 1999.11a
• /
• pp.57-61
• /
• 1999

The effect of the microstructure of gray cast iron on friction properties was investigated by using a pad-on-disk type friction tester. Cast iron samples used in this investigation were obtained from "step block" castings, which were designed to produce microstructure with different graphite flake morphologies from different cooling rate and solidification rate. Results of this work showed that the gray cast iron disks with long graphite flakes showed less fading. The rotors containing smaller amounts of ferrite showed higher friction coefficient and better fade resistance than others.an others.

• Journal of Korea Foundry Society
• /
• v.19 no.1
• /
• pp.84-90
• /
• 1999

In this study, CV cast iron was reverse transformed to produce harder second phase surrounding graphite nodules, and then the microstructure and related mechanical properties of the reverse transformed CV cast iron were investigated by using optical microscopy and by carrying out hardness, tension and impact test. The formation of hard second phase surrounding graphite nodules increased the hardness in CV cast iron. The marked increase in hardness was resulted from the formation of martensite surrounding graphite nodule. It is expected from these results that the formation of martensite surrounding graphite nodule would improve the wear resistance of CV cast iron. The formation of both martensite and pearlite surrounding graphite nodule improved the tensile properties. Impact properties were decreased with increasing the volume fraction of hard second phase. However, the reduced impact properties could be recovered through phase transformation of martensite into pearlite and sorbite by tempering.

• Corrosion Science and Technology
• /
• v.20 no.3
• /
• pp.143-151
• /
• 2021

In this study, optimal shot peening process conditions were investigated for improving the cavitation erosion resistance of gray cast iron under a marine environment. Shot peening was performed with variables of injection pressure and injection time. The durability was then evaluated through cavitation erosion test which was conducted according to the modified ASTM G-32 standard. The tendency of cavitation erosion damage according to shot peening process condition was investigated through weight loss rate, surface and cross-sectional analysis of the specimen before and after the test. As a result, the shot peening process condition that could minimize cavitation erosion was when the injection pressure was the lowest and when the injection time was the shortest. This was because the flake graphite exposed on the gray cast iron surface could be easily removed under such condition. Therefore, the notch effect can be prevented by surface modification. In addition, the cavitation erosion damage mechanism of gray cast iron was discussed in detail.

• Journal of Korea Foundry Society
• /
• v.43 no.6
• /
• pp.279-285
• /
• 2023

In order to predict the mechanical properties of ductile cast iron heat treated in an intercritical temperature range, samples machined from cast iron with a tensile strength of 450 MPa were heat-treated at various intercritical temperatures and air-cooled, after which a microstructural analysis and Brinell hardness test were conducted. As the heat treatment temperature was increased in the intercritical temperature range, the ferrite fraction in the ductile cast iron decreased and the pearlite fraction increased, whereas the nodularity and nodule count did not change considerably from the corresponding values in the as-cast condition. The Brinell hardness values of the heat-treated ductile cast iron increased gradually as the heat treatment temperature was increased. Based on the measured alloy composition, the fraction of each stable phase and the hardness model from the literature, the hardness of the ductile cast iron heat treated in the intercritical temperature range was calculated, showing values very similar to the measured hardness data. In order to check whether it is possible to predict the hardness of heat-treated ductile cast iron by using the phase fraction obtained from thermodynamic calculations, the volumes of graphite, ferrite, and austenite in the alloy were calculated for each temperature condition. Those volume fractions were then converted into areas of each phase for hardness prediction of the heat-treated ductile cast iron. The hardness values of the cast iron samples based on thermodynamic calculations and on the hardness prediction model were similar within an error range up to 27 compared to the measured hardness data.

• 보존과학연구
• /
• s.21
• /
• pp.101-118
• /
• 2000

Stone cultural properties(pagoda, Buddhist statue etc.) is moved in original place for many reasons and restored after taking to pieces for structural safety. With the movement and restoration after taking to pieces, the cast iron is used for the sake of a fixation and horizontality. The stone cultural properties are spoiled the beauty and accelerated the weathering because of the corrosion product of cast iron. So we need to substitute for the improved property in all aspects. We are executed the corrosion test and inquired the property of material on the usable material for the shim of stone cultural properties. That is the Cast iron, Stainless steel, Titanium and Fiber Reinforced Plastics. In the result of the physical property and strength, the Stainless steel and Titanium was superior to the Cast iron. And the Stainless steel and Titanium was slower than the Cast iron in the corrosion velocity for the acid, salt and rain. If the shim is substitute the Stainless steel or Titanium for the Cast iron, the stone cultural properties are able to reduce the pollution of stone cultural properties by corrosion product and should not happen in the matter of stone pagoda.