• Journal of Welding and Joining
• /
• v.16 no.1
• /
• pp.114-124
• /
• 1998

The effect of matrix phase (austenite, pearlite, martensite) on the low stress abrasion resistance in the chromium-carbide-type high Cr white iorn hardfacing weld deposites has been investigated. In order to examine matrix phase, a series of alloys with different matrix phase by changing the ratio of Cr/C system by heat treatment were employed. The alloys were deposited twice on a mild steel plate using self-shielding flux cored arc welding process. The low stress abrasion resistance of the alloys against sands was measured by the Dry Sand/Rubber Wheel Abrasion Test(RWAT). Even though formation of pearlite phase in the matrix showed higher hardness than that of austenite, there was no observable difference in wear resistance between the pearlite and austenite phase for the same amount of chromium-carbide in the matrix. On the other hand, the formation of martensitic phase,, from heat treated austenitic alloys (high content of Cr), enhanced wear resistance due to its fine secondary precipitates.

• Journal of Welding and Joining
• /
• v.16 no.1
• /
• pp.125-133
• /
• 1998

The effect of volume fraction of Cr carbide phase (Cr CVF) on the low stress abrasion resistance in the chromium-carbide-type high Cr white iron hardfacing weld deposits has been investigated. In order to examine Cr CVF, a series of alloys with varying Cr CVF by changing chromium and carbon contents and the ratio of Cr/C were employed. The alloys were deposited once or twice on a mild steel plate using the self-shielding flux cored arc welding process. The low stress abrasion resistance of the alloys against sands was measured by the Dry Sand/Rubber Wheel Abrasion Test (RWAT). It was shown that hardness and abrasion resistance increased with increasing Cr CVF within the whole test range (Cr CVF : 0.23-0.64). Both primary Cr carbide and eutectic Cr carbide were particularly effective in resisting wear due to their high hardness.

• Journal of Welding and Joining
• /
• v.10 no.3
• /
• pp.1-12
• /
• 1992

A literature review was conducted to survey informations available on the welding metallurgy of aluminum alloys and its effect on fusion weldability, especially on solidification cracking and pore formation. Solidification cracking behavior of Al weld is a complicate matter as compared to other high alloys, where a relatively simple Fe-X(most detrimental elements S, P, B, Si, etc) binary diagram can be successfully applicable. Both additive and synergistic effects of elements should be considered together. A same element play a different role from system to system. Porosity, caused by hydrogen contamination of the weld is one of the most troublesome welding problems. The primary sources of hydrogen are believed to be an absorbed moisture on the filler metal or base metal and in the shielding gas. It is extremely important that reliable quality-control procedures be employed to eliminate all possible sources of hydrogen contamination. Selection of proper process and parameters is sometimes more important than controlling of alloying elements in order to make a defect-free weld.

• Journal of Magnetics
• /
• v.12 no.1
• /
• pp.49-52
• /
• 2007

We investigated annealing effect of microforged powders on magnetic properties and electromagnetic absorption behaviors for ferromagnetic Fe-Cr metal alloy powder-polymer composites. The coercive properties greatly decreased with annealing temperature and the magnetic permeability had significantly increased after microforging and subsequent annealing treatment, due to a reduction in lattice strain of the microforged powders. The power loss in the far field regime also had greatly increased after microforging and subsequent annealing treatment in frequency range from 50 MHz to 6 GHz. As a result, the electromagnetic absorption of ferromagnetic Fe-Cr alloy metal powder-polymer composites was highly improved because of the relaxation of the internal strain during annealing process.

• Laser Solutions
• /
• v.17 no.2
• /
• pp.11-18
• /
• 2014

This research was conducted as a fundamental study to apply tailored blank welding technique into automotive production process. Specially we tried to apply the TWB technique to exhaust system. The materials used in this work were ferritic 439 stainless steel sheet with a thickness of 1.2mm and 0.8mm. Welding tests were conducted for BOP test and dissimilar thickness (0.8 to 1.2t) cases. Major process parameters were position of focus, travel speed, shielding gas and joint (gap) condition. As a result, there are nothing significant welding characteristic compare with TWB of carbon steel. Stainless steel shows the good weldability and mechanical properties (tensile, hardness and forming strength) also shows high level. Just problem is gap condition. However, also in this case, it shows not only good forming strength but also base metal fracture after tensile test. And to conclude, it is good opportunity to make lightweight design muffler using TB welding technique.

• Journal of Welding and Joining
• /
• v.15 no.4
• /
• pp.109-115
• /
• 1997

Laser cladding is a technique for modification of metal surface. In this laser cladding experiment a metal powder feeding system was developed for more efficient laser cladding. This system can reduce processing time and be used simpler than the conventional method. The feeding of metal powder has given a rise to the process for sequential buildup of bulk rapidly solidified materials in the form of fine powder stream to the laser cladding process. The parameters of laser cladding have been investigated using this experimental equipment. Bronze on aluminum alloy and copper on aluminum alloy were experimented by using defocused beam, powder feeding system, and gas shielding. Good cladding was achieved in the range of beam travel speed of 2.25m/min. In the case of copper/aluminum and bronze/aluminum substrate, the absorption of laser beam was too high to produce low diluted clad. In the case of copper/1050 aluminum, the optimal laser cladding condition was of laser power of 2.8kW, powder feed rate of 0.31g/s and beam travel speed of 2.25m/min. In the case of bronze/aluminum the optimal condition is of laser power of 2.5kW, powder feed rate of 0.31g/s, and beam travel speed of 2.36m/min.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2005.06a
• /
• pp.1560-1565
• /
• 2005

Laser beam welding is increasingly being used in welding of structural steels. The laser welding process is one of the most advanced manufacturing technologies owing to its high speed and deep penetration. The thermal cycles associated with laser welding are generally much faster than those involved in conventional arc welding processes, leading to a rather small weld zone. Experiments are performed for 304 stainless steel plates changing several process parameters such as laser power, welding speed, shielding gas flow rate, presence of surface pollution, with fixed or variable gap and misalignment between the similar and dissimilar plates, etc. The following conclusions can be drawn that laser power and welding speed have a pronounced effect on size and shape of the fusion zone. Increase in welding speed resulted in an increase in weld depth/ aspect ratio and hence a decrease in the fusion zone size. The penetration depth increased with the increase in laser power.

• Journal of the Korean Society of Safety
• /
• v.25 no.1
• /
• pp.27-31
• /
• 2010

It is a well known fact that the LCD and Semiconductor Devices are a central part of IT industry which is important in the present and the future. But the biggest problem of Semiconductor and LCD manufacturing is maintaining a cleaning room environment. For this reason, the soft X-ray type Ionizer was used as the electrostatic reducer device, which protects damage of the product against electrostatic discharge in the manufacturing process. Therefore it is a essential important factor during Semiconductor and LCD production process. But the soft X-ray has a intrinsic problem with harmful to human being in case of soft X-ray exposure. That's reason we have the research to solve above problem and made an apparatus that it was covered with shielding structure to protect X-ray radiation to outside. And besides, it has a possibility to eliminate the charged electrostatic in the narrow space through the slot for Ion emissions with dual soft X-ray sources on the both side. It is also not make the particles from itself when it has been operated.

• Journal of the Korean Society for Precision Engineering
• /
• v.19 no.4
• /
• pp.132-139
• /
• 2002

In GMAW(Gas Metal Arc Welding) processes, bead geometry (penetration, bead width and height) is a criterion to estimate welding quality. Bead geometry is affected by welding current, arc voltage and travel speed, shielding gas, CTWD (contact-tip to workpiece distance) and so on. In this paper, welding process variables were selected as welding current, arc voltage and travel speed. And bead geometry was reasoned from the chosen welding process variables using neuro-fuzzy algorithm. Neural networks was applied to design FL(fuzzy logic). The parameters of input membership functions and those of consequence functions in FL were tuned through the method of learning by backpropagation algorithm. Bead geometry could be reasoned from welding current, arc voltage, travel speed on FL using the results learned by neural networks. On the developed inference system of bead geometry using neuro-furzy algorithm, the inference error percent of bead width was within $\pm$4%, that of bead height was within $\pm$3%, and that of penetration was within $\pm$8%. Neural networks came into effect to find the parameters of input membership functions and those of consequence in FL. Therefore the inference system of welding quality expects to be developed through proposed algorithm.

• Composites Research
• /
• v.17 no.3
• /
• pp.38-44
• /
• 2004

The electromagnetic interference (EMI) shielding is very essential for commercial and military purposes. We fabricated multi-walled carbon nanotube (MWNT)/epoxy composites and studied the electromagnetic characteristics of the composites before we study the characteristics of MWNT-added glass fiber-reinforced composites. After setting up the fabrication process, we measured the permittivity of MWNT/epoxy composites with process variables and MWNT concentrations in X-band (8.2GHz~12.4GHz). We also observed re-aggregation phenomenon of MWNTs and investigated its effect on the permittivity. The permittivity of the composites was influenced by the degree of dispersion of MWNTs and increased almost linearly as MWNT concentration increases.