• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.19 no.3
• /
• pp.370-375
• /
• 2010

Tungsten carbide microshaft is used as micro punch, electrode of micro electro discharge machining, and micro tool because of its high hardness and rigidity. In this research, tungsten carbide microshaft was fabricated using electrochemical machining. $H_2SO_4$ solution was used as the electrolyte because it can dissolve tungsten carbide and cobalt simultaneously. Experimentally studied were the effects of electrolyte concentration, machining time, and machining voltage on material removal rate and the shape of the microshaft. To eliminate the effects of bubbles and metal corrosion layer on microshaft shape, the machining was performed below the electrolysis voltage. Three step electrochemical process was suggested to fabricate the straight tungsten carbide microshaft. As a result, a straight tungsten carbide microshaft of $30{\mu}m$ in diameter and $500{\mu}m$ in length was obtained through the proposed three step electrochemical process.

• Design & Manufacturing
• /
• v.13 no.2
• /
• pp.44-48
• /
• 2019

Motor core products are used as materials for electrical steel sheets and cold-rolled steel sheets according to the performance of motors. The cemented carbide material of the mold punch applied to the motor core material causes many troubles due to abrasion and burr problem. The selection of these materials has a great effect on the production life, mass production, product quality as well as mold life. The cemented carbide applied to the products of the motor core is recognized as a very important part. In this study, cold rolled steel sheet was applied to motor core SCP-1 steel 1.0mm, and The effects of abrasion and punching oil on the shear process were investigated for the selection of cemented carbide. Experiments were conducted to select and apply cemented carbide only for the motor core punch optimized for cold rolled steel. The results showed that the cemented carbide material of $CDK3^{***}$ produced the least wear and burrs.

• Proceedings of the Korean Powder Metallurgy Institute Conference
• /
• 2006.09a
• /
• pp.156-157
• /
• 2006

The preparation of composite powders for plasma spraying by an in-house designed mechanofusion process is investigated. Results show that dry particle coating depends on the chemical and mechanical properties of powders. In metal/oxide and metal/oxide/carbide powder mixtures, fine ceramic particles coat the surface of the metallic coarser particles. A nearly rounded shape of the final composite particles is induced by the mechanical energy input with no formation of new phases. However with the carbide/metal powdered system, only an intimate mixture of components is achieved. It is suggested that the coating mechanism is governed by agglomeration and rolling phenomena.

• Journal of Advanced Marine Engineering and Technology
• /
• v.26 no.6
• /
• pp.661-669
• /
• 2002

Rapid tooling technique enables us to make dies and molds that produce prototype parts with the correct material at a substantially reduced cost and time. In this study, experiments on selective laser sintering of tungsten carbide-cobalt mixture were carried out to find optimal sintering conditions that will be applied to rapid metal tooling. The experiments were carried out within an air, an argon and a nitrogen atmosphere. Coupons of single layer were sintered at various laser powers, scanning speeds and scan spacings. Very severe oxidation took place within an air atmosphere. The oxidation is reduced significantly within an argon and a nitrogen atmosphere. The thickness of the sintered coupons is increased as the energy density, the laser energy Per unit scanned area, is increased. Several multi-layer sintering experiments were also carried out.

• Korean Journal of Materials Research
• /
• v.13 no.12
• /
• pp.839-845
• /
• 2003

The abrasion and impact wear resistance were investigated on the hardfacing weld dispersed with the recycled hard metal(HM). The HM was composed of the tungsten carbide(WC) reinforced metal matrix composite. The cored wire filled with the 25-35wt.% HM and 2-8wt.% of the alloying element, Fe-75Mn- 7C(FeMnC), was used for the gas metal arc(GMA) welding. By using the cored wire of the 25wt.% HM and FeMnC addition, the weld showed mostly constant wear loss for the abrasion as a function of the FeMnC content. This was due to the insufficient amount of the tungsten carbide formed during the GMA welding. The FeMnC addition to the 35wt.% HM did not improve the abrasion wear property since the amount of the tungsten carbide formed was decreased with respect to the FeMnC amount. The 6wt.% FeMnC addition to the 35wt.% HM exhibited the better impact wear resistance than the hardfacing weld by 40wt.% HM.

• Korean Journal of Metals and Materials
• /
• v.48 no.7
• /
• pp.589-597
• /
• 2010

In the present study, the effect of variation in alloying elements on the carbide formation behavior during casting and homogenization treatment of M2 high speed steels was investigated. M2 high speed steels of various compositions were produced by vacuum induction melting. Contents of C, Cr, W, Mo, and V were varied from the basic composition of 0.8C, 0.3Si, 0.2Mn, 4.0Cr, 6.0W, 5.0Mo, and 2.0V in weight percent. Homogenization treatment at $1150^{\circ}C$ for 1.5 hr followed by furnace cooling was performed on the ingots. Area fraction and chemical compositions of eutectic carbide in as-cast and homogenized ingots were analyzed. Area fraction of eutectic carbide appeared to be higher in the ingots with higher contents of alloying elements the area fraction of eutectic carbide also appeared to be higher on the surface regions than in the center regions of ingots. As a result of the homogenization treatment, $M_2C$ carbide, which was the primary eutectic carbide in the as-cast ingots, decomposed into thermodynamically stable carbides, MC and $M_6C$. The latter carbide was found to be the main one after homogenization. Fine carbides uniformly distributed in the matrix was found to be MC type carbide and coarsened by homogenization.

• Journal of Powder Materials
• /
• v.10 no.6
• /
• pp.390-394
• /
• 2003

Ultra fine titanium carbide particles were synthesized by novel metallic thermo-reduction process. The vaporized TiC1$_4$+$CCl_4$ gases were reacted with liquid magnesium and the fine titanium carbide particles were then produced by combining the released titanium and carbon atoms. The vacuum treatment was followed to remove the residual phases of MgC1$_2$ and excess Mg. The stoichiometry, microstructure, fixed and carbon contents and lattice parameter were investigated in titanium carbide powders produced in various reaction parameters.

• Journal of the Korean Society for Precision Engineering
• /
• v.19 no.3
• /
• pp.80-87
• /
• 2002

Tungsten carbide microshaft is used as micro-punch, electrode of MEDM (micro-electro-discharge machining), and micro-tool because it has high hardness and high rigidity. In this study, the tungsten carbide microshaft was fabricated using electrochemical machining. Concentration of material removal at the sharp edge and metal corrosion layer affect the shape of the microshaft. Control of microshaft shape was possib1e through conditioning the machining voltage and electrolyte concentration. By applying periodic voltage, material removal rate increased and surface roughness improved. The fabricated microshaft in $H_2 SO_4$ electrolyte maintained sharper end edge and better surface finish than those fabricated by other electrolytes.

• Bulletin of the Korean Chemical Society
• /
• v.35 no.6
• /
• pp.1897-1900
• /
• 2014

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