• 한국축산시설환경학회지
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• 제7권2호
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• pp.127-136
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• 2001

This experiment was carried out to investigate the effect of supplementing phosphorus to Korean cow manure on the growth and cast production of earthworm(Eisenia Foetida), and to estimate the optimal phosphorus level for the growth and cast production of earthworm and ratios of available phosphorus and calcium content of cast in optimal phosphorus levels. Phosphorus supplementing ratios to Korean native cow were 0, 1%, 2%, 4% and 8A%, respectively. The volume of raising box was 3375cm$^3$(15$\times$15$\times$15cm), and 500g of cow manure filled up to 10cm layer. Raising density was 90㎤ per worm during the experimental period(60 days). The maximum fresh weight and cast production of earthworm were obtained at 2~4% and 1% levels of phosphorus supplementation to Korea native cow manure. The total phosphorus and available phosphorus contents of earthworm tissues were not significant among in all treatments. There was a positive significantly differences between total phosphorus and available phosphorus of cast and residual matters. Available phosphorus content of cast were ranged from 9.3mg/g to 17.3mg/g at 1~4% levels of phosphorus supplementation. Ratios of available phosphorus and calcium contents of cast were 1.94~3.15:1 and 0.87~1.33:1 at 2~4% and 0~1% levels of phosphorus supplementation.

• The Korean Journal of Ecology
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• 제16권2호
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• pp.229-238
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• 1993

Ecological role of earthworms in red pine forest was investigated with emphasis on the population size, cast production and changes of physicoKDICical properties of soil by earthworm's activities. The density of earthworms was 62.8/m2 in August, 1992. Average biomass of earthworms was 16.3 g/m2. N and P concentrations in the tissue of earthworms were 28.5 mgN/g and 0.5 mgP/g, respectively. Cast production continued from April to November, with a peak in August. Annual production of earthworm casts was 5,379 g/m2. Bulk density of surface soil decreased due to the earthworm's cast-forming activity. Clay fraction in surface soil increased by addition of casts. Soil KDICical properties were significantly different between the surface soil and the earthworm casts. The amounts of organic matter, N, P, K, Ca and Mg added to the soil via earthworm casts during one year were 9.3t/ha, 11.29 kg/ha, 0.78 kg/ha, 12.36 kg/ha, 140.29 kg/ha and 20.96 kg/ha, respectively. Earthworms can feed on waxy and resinous litter when it became palatable by decomposing processes.

• 한국주조공학회지
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• 제15권6호
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• pp.546-557
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• 1995

This study was undertaken to obtain an improved understanding of the effects of alloying elements on the residual amounts of Mg in the melt and on the resultant microstructure of compacted vermicular graphite cast irons, and the influence of alloying elements and cooling rates during solidification on the formation of phosphide eutectics, and on the mechanical properties of compacted vermicular graphite cast irons containing copper, tin, molybdenum for producing pearlitic matrix, and also containing phosphorus and boron for increasing wear resistance were evaluated.

• 한국주조공학회지
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• 제38권1호
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• pp.16-26
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• 2018

In this study, the effects of the pouring temperature, preheating temperature, surface condition and fraction of the wear resistant part on the production of duo-castings were investigated using a high Cr white cast iron with excellent abrasion resistance and a low Cr alloy steel with good toughness. The constituent materials of the duo-castings were designed to have high hardness, fracture toughness and abrasive wear resistance for the replacement of high Mn alloy steels with low abrasive wear resistance. In particular, the amount of abrasive wear of 17% Cr white cast iron was about 1/20 of that of high Mn alloy steel. There was an intermediate area of about 3mm due to local melting at the bonding interface of the duo-castings. These intermediate regions were different from those of the constituent materials in chemical composition and microstructure. This region led to fracture within the wear resistant part rather than at the bonding interface in the bending strength test. The bending fracture strengths were 516-824 MPa, which were equivalent to the bending proof strength of high Mn steel. The effects of various casting conditions on the duo-cast behavior were studied by simple pouring of low Cr alloy steel melt, but the results proved practically impossible to manufacture duo-castings with a sound bonding interface. However, the external heating method was suitable for the production of duo-castings with a sound bonding interface.

• 한국주조공학회지
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• 제29권2호
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• pp.70-77
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• 2009

The aim of this study was to develop a Mo and V free low alloy cast steel materials, enabling the significant cost- and time-savings in manufacturing and maintaining the insert of cold pressing die without impairment of the important properties. For this purpose, the effects of Si content on combinations of important properties such as hardness, hardenability, and weldability, and strength were systematically investigated. In order to evaluate the applicability as the insert of cold pressing die, the mechanical properties were measured after spheroidization annealing, quenching and tempering, and flame hardening heat treatments, respectively. After the Q/T and F.H. treatments, the developed 0.8${\sim}$1.6%Si containing Mo and V free low alloy cast steels showed excellent matrix strengthening effect, hardenability, and weldability, fulfilling the industrial criterion of the mechanical properties for automobile cold pressing die insert.

• 한국주조공학회지
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• 제17권4호
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• pp.393-401
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• 1997

Commercial flake graphite cast iron substrate was coated with titanium powder by low pressure plasma spraying and was irradiated with a $CO_2$ laser to produce the wear resistant composite layer. From the experimental results of this study, it was possible to composite TiC particles on the surface layer by direct reaction between carbon existed in the cast iron matrix and titanium with thermal sprayed coating by remelting and alloying them using laser irradiation. The cooling rate of laser remelted cast iron substrate without titanium coating was about $1{\times}10^4$ K/s to $1{\times}10^5$ K/s in the order under the condition used in this study. The microstructure of alloyed layer consisted of three zones, that is, TiC particule crystallized zone (MHV $400{\sim}500$), the mixed zone of TiC particule+ledebulite (MHV $650{\sim}900$) and the ledebulite zone (MHV $500{\sim}700$). TiC particules were crystallized as a typical dendritic morphology. The secondary TiC dendrite arms were grown to the polygonized shape and were necking. And then the separated arms became cubic crystal of TiC at the slowly solidified zone. But in the rapidly solidified zone of fusion boundry, the fine granular TiC particules were grouped like grape.

• 한국주조공학회지
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• 제17권4호
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• pp.371-378
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• 1997

The study for direct synthesis of TaC carbide which was a reaction product of tantalum and carbon in the cast iron was performed. Cast iron which has hypo-eutectic composition was cast bonded in the metal mold with tantalum thin sheet of thickness of $100{\mu}m$. The contents of carbon and silicon of cast iron matrix was controlled to have constant carbon equivalent of 3.6. The chracteristics of microstructure and the formation mechanism of TaC carbide in the interfacial reaction layer in the cast iron/tantalum thin sheet heat treated isothermally at $950^{\circ}C$ for various time were examined. TaC carbide reaction layer was grown to the dendritic morphology in the cast iron/tantalum thin sheet interface by the isothermal heat treatment. The composition of TaC carbide was 48.5 at.% $Ti{\sim}48.6$ at.% C-2.8 at.% Fe. The hardness of reaction layer was MHV $1100{\sim}1200$. The thickness of reaction layer linearly increased with increasing the total content of carbon in the cast iron matrix and isothermal heat treating time. The growth constant for TaC reaction layer was proportional to the log[C] of the matrix. The formation mechanism of TaC reaction layer at the interface of cast iron/tantalum thin sheet was proved to be the interfacial reaction.

• 한국주조공학회지
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• 제3권4호
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• pp.239-247
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• 1983

CV graphite cast iron has been studied and generally known to have properties close to the average values of those between flake and spheroidal graphite cast iron. However, the thermal diffusivity of CV graphite cast iron is much larger than that of the average value of those between flake and spheroidal graphite cast iron. In this study, an easy production method of CV graphite cast iron with small additions of a Al-Cu which is known as the element of the graphitization was investigated. The effects of hold time and of Al-Cu additions after the treatments with spheroidizer (Fe-Si-Mg alloy) were also investigated. Increasing the additions of a Al-Cu alloy, the holding time to form a CV graphite cast iron was decreasing. Tensile strength and thermal diffusivity (flash method) were measured in order to find the changes of the mechanical properties and the physical properties. Spheroidal, CV, and flake graphite cast iron have tensile strengths 46.44, 38.29, and $27.29\;kg/mm^2$ and thermal diffusivities $3.95{\times}10^{-6,}$ $8.41{\times}10^{-6}$, $8.81{\times}10^{-6}m^2/sec$, respectively at room temperature.

• 한국주조공학회지
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• 제13권4호
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• pp.333-341
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• 1993

The effects of alloying elements on the structure and mechanical properties of compacted/vermicular graphite cast irons containing copper, tin and molubdenum for producing pearlite matrix, and also containing phosphorus and boron for increasing wear resistance, were investigated. The Brinell hardness and ultimate tensile strength of the specimens with the range of compositions, [1.5% Cu-0.05% Sn-(0.2-0.4)% Mo-(0.2-0.6)% P-(0.035-0.070)% B], was found to fall within in the following range, depending on their composition; Brinell hardness of BHN 250-315, ultimate tensile strength of $28.1-40.3kg/mm^2$. It was also found within this experiment that CV graphite cast irons possessing higher amount of phosphide eutectic exhibit better wear resistance, but the wear resistance became deteriorate when the area fraction of phosphide eutectics exceed more than 10%. From these experimental results, it could be concluded that the CV graphite cast iron containing 1.5% Cu, 0.05% Sn, 0.4% Mo, 0.2% P and 0.035% B showed good mechanical and wear resistance properties.

• 한국기계가공학회지
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• 제10권5호
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• pp.72-78
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• 2011

Currently, for the damper case, the material produced by cast/forge welding is mechanically processed and then the final product is mass-produced. By cutting the cast/forge welded material, the issues of excessive cutting time, multiple process production, and a large amount of chips (40% loss from the original material) arise, causing increased production cost and reduced profitability. Thus, in this study, the incremental forming technology which generates no chips was applied in production. Analysis was excuted for 1st and 2nd works by change of tool diameter and working tool. For this, 3D molding and analysis were executed, which was applied to the processing the result, successful processing could be achieved through a few trials of molding processing according to tool forming and rotation counts.