• Journal of Advanced Marine Engineering and Technology
• /
• v.35 no.8
• /
• pp.1041-1047
• /
• 2011

In this study, two types of die material cast iron was treated for surface hardening by using high power diode laser to improve mechanical properties of die which is using as essential production technology in the parts manufacturing in virtually all the infrastructure industries now. First of all, the heat treatment characteristics of FCD550 material which is spheroidal graphite cast iron, and through the heat treatment of HCI350 material which is flake graphite cast iron, the heat treatment characteristics of the two materials were compared. The hardness of hardened zone increased over 3 times over base material for both specimens, but as for required heat input, HCI350 was higher than FCD550 material depending on the heat conductivity of the materials by the content amount and shape of graphite contained in the material.

• Journal of the Microelectronics and Packaging Society
• /
• v.21 no.2
• /
• pp.65-70
• /
• 2014

Warpage of top packages to form thin package-on-packages was measured with progress of their process steps such as PCB substrate itself, chip bonding, and epoxy molding. The $100{\mu}m$-thick PCB substrate exhibited a warpage of $136{\sim}214{\mu}m$. The specimen formed by mounting a $40{\mu}m$-thick Si chip to such a PCB using a die attach film exhibited the warpage of $89{\sim}194{\mu}m$, which was similar to that of the PCB itself. On the other hand, the specimen fabricated by flip chip bonding of a $40{\mu}m$-thick chip to such a PCB possessed the warpage of $-199{\sim}691{\mu}m$, which was significantly different from the warpage of the PCB. After epoxy molding, the specimens processed by die attach bonding and flip chip bonding exhibited warpages of $-79{\sim}202{\mu}m$ and $-117{\sim}159{\mu}m$, respectively.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.35 no.12
• /
• pp.1663-1668
• /
• 2011

Surface hardening treatment is required to improve the wear-resistance of press die because severe abrasion of die occurs during the drawing process in which the forming of the automotive body is completed and during the trimming process in which the unnecessary parts are cut. In this study, experiments on the laser surface treatment of press die are performed. Specimens are heat-treated separately at certain plate and edge position by using a diode laser to carry out suitable surface hardening treatment to reduce the wear during the drawing and the trimming processes, and the proper conditions for heat treatment are found. Spheroidal and flake graphite cast iron specimens are used, and the heat treatment characteristics of the two materials are compared. From the results of the study, it is confirmed that the heat treatment characteristics differed depending on the materials.

• Transactions of Materials Processing
• /
• v.21 no.1
• /
• pp.13-18
• /
• 2012

During warm forging, materials are formed in the temperature range of $300^{\circ}C\sim900^{\circ}C$. In this temperature range, the friction between the forging die and the material is very high and has a negative effect on the forming process causing severe die wear and possible defects in the component because of stick-slip. Thus, lubrication characteristics are a very important factor for productivity during warm forging. In this paper, ring compression experiments were conducted to estimate the friction factor between the die and the materials as the main factor in characterizing the lubricant. Also, ring tests using normal graphite power as a lubricant coating system were compared with tests using nano graphite powder. The results confirm that the nano graphite is superior to the normal graphite in view of its lubricating effect. In addition, the friction factor (m) was estimated with respect to the amount of the nano graphite content in the lubricant. With 10 % nano graphite the friction factor had the lowest value as compared to other amounts. It can be concluded that the amount of the nano graphite in the coating system can be optimized to obtain the best lubrication condition between the die and the material using ring test experiments.

• Korean Journal of Metals and Materials
• /
• v.50 no.2
• /
• pp.107-115
• /
• 2012

Direct laser melting (DLM) is a powder-based additive manufacturing process to produce parts by layer-by-layer laser melting. As the properties of the manufactured parts depend strongly on the deposited laser-melted bead, deposited layers obtained by the DLM process were characterized in this study. This investigation used a 200 W fiber laser to produce single-line beads under a variety of different energy distributions. In order to obtain a feasible range for the two main process parameters (i.e. laser power and scan rate), bead shapes of single track deposition were intensively investigated. The effects of the processing parameters, such as powder layer thickness and scan spacing, on geometries of the deposited layers have also been analyzed. As a result, minimum energy criteria that can achieve a complete melting have been suggested at the given powder layer thickness. The surface roughnesses of the deposited beads were strongly dependent on the overlap ratio of adjacent beads and on the energy distributions of laser power. Through microstructural analysis and hardness measurement, the morphological and mechanical properties of the deposited layers at various overlapped beads have also been characterized.

• Journal of Magnetics
• /
• v.16 no.3
• /
• pp.220-224
• /
• 2011

Die-upset magnets from a mechanically-milled Pr(Co,In)$_5$-type alloy are known to have a peculiar texture; the easy magnetization axis (c-axis) is perpendicular to the pressing direction. This peculiar texture is thought to be linked closely to the anisotropic mechanical properties of Pr(Co,In)$_5$-type hexagonal compounds. The hardness of the Pr(Co,In)$_5$-type crystal was measured using selectively grown grains in an annealed $Pr_{17}Co_{82}In_1$ alloy button, and the crystallographic orientation was determined by observing the magnetic domain image. The hardness (549 VHN) on the plane with a 'cogwheel'-type domain image was significantly higher than that (510 VHN) on the plane with a 'cigar'-type domain image, indicating that the inter-layer bonding force between the (000l) basal planes is stronger than that between the (hki0) planes. This suggests that the most probable slip plane is the (hki0) plane parallel to the c-axis. During die-upsetting of the Pr(Co,In)$_5$-type alloys the deformation proceeds by (hki0) plane slip, and the c-axis rotates to ultimately become oriented perpendicular to the pressing direction. It is proposed that the peculiar texture in the die-upset Pr(Co,In)$_5$-type magnets is probably developed by slip deformation of the (hki0) plane of the Pr(Co,In)$_5$-type grains.

• Journal of Korean Society of Environmental Engineers
• /
• v.30 no.3
• /
• pp.331-338
• /
• 2008

Coal-tar enamel, blown asphalt and polyethylene have been used as wrapping materials of steel pipe in Korea. Currently, every manufacturer produces wrapped steel pipes with different materials and methods, and little research has been performed to get on wrapping methods and materials. In this research, properties of wrapping material of steel pipe used for water supply have been evaluated. All of the materials tested in this work were found to meet the standard. Among the wrapping materials of steel pipe tested, blown asphalt and coal-tar enamel were reasonable in price, and their mechanical properties were excellent. The quality of the wrapped steel pipes was being melted easily in organic solvent. When coated thick, the load of the steel pipes was higher than necessary. Tensile strength of cathode exfoliation and PE 3-layer wrapping method was excellent. The pulling intensity of T-Die PE 3-layer was stronger than PE fluidized in PE wrapping method. Cathode exfoliation area was smaller than PE fluidized. Mechanical property and thermo-property of T-Die PE 3-layer were excellent and its anti-chemical property was great. Liquid epoxy can change the property of coating materials depending on the hardening condition and resin selection. Polyurethane used in this test showed a less adhesive strength with steel pipes than epoxy. Moisture absorbance rate was higher than Epoxy's, however. To utilize polyurethane as wrapping materials, basic property of the matter should be improved followed by finding the best suited coating condition. The method of PE 3-layer by extrude method appeared to be the best in this study. However, identification of other wrapping materials requires further additional tests.

• Archives of Metallurgy and Materials
• /
• v.66 no.4
• /
• pp.1033-1036
• /
• 2021

Laser cladding is a method that can be applied to repair the crack and break on the mold and die surfaces, as well as generate new attributes on the surface to improve toughness, hardness, and corrosion resistance. It is used to extend the life of the mold. It also has the advantages of superior bonding strength and precision coating on a local area compared with the conventional thermal spraying technology. In this study, we investigated the effect of cladding on low carbon alloy steel using 18%Cr-2.5%Ni-Fe powder (Rockit404), which showed high hardness on the die surface. The process conditions were performed in an argon atmosphere using a diode laser source specialized for 900-1070 nm, and the output conditions were 5, 6, and 10 kW, respectively. After the cladding was completed, the surface coating layer's shape, the hardness according to the cross-section's thickness, and the microstructure were analyzed.

• Proceedings of the Korean Fiber Society Conference
• /
• 2001.04a
• /
• pp.225-228
• /
• 2001

• Proceedings of the Korean Society of Rheology Conference
• /
• 2001.06a
• /
• pp.57-60
• /
• 2001