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Improvement of Weldability of Hot-Dip Galvanized Steel by Anti-Galvanizing Coating with Si-Fe-Al Oxide-Based Micropowder

So Seong-Min, Kim Ki-Yeon, Park Il-Song, Lee Seok-Jae, Yoo Dong-Jin, Kim Yeon-Won, Oh Min-Suk

Archives of Metallurgy and Materials

2023

Vol. 68, iss. 1

155--159

A Si-Fe-Al ternary oxide-based micropowder coating was used to prevent the formation of a Zn coating on steel during the hot-dip Zn galvanizing process to reduce the welding fume and defects generated during the welding of Zn-galvanized steel. The composition ratio of the oxide powder was optimized and its microstructure and weldability were evaluated. The optimized oxide coating was stable in the hot-dip galvanizing bath at 470°C and effectively inhibited the formation of Zn coating. The Zn residue could be easily removed with simple mechanical impact. The proposed coating reduced Zn fume and prevented the residual Zn from melting in the weld bead during high-temperature welding, thus reducing the number of welding defects. The results indicated that this pretreatment can simplify the manufacturing process and shorten the process time cost-effectively.

Effect of Atmospheric-Pressure Gas-Plasma Treatment on Surface Properties of Hot-Dip Zn-Mg-Al Alloy-Coated Steel

Jeong Chang-U, Kim Jae-Hyeon, Park Je-Shin, Kim Min-Su, Kim Sung-Jin, Oh Min-Suk

Archives of Metallurgy and Materials

2023

Vol. 68, iss. 1

187--190

The effect of plasma-radical change on the surface properties of Zn-Mg-Al ternary-alloy-coated steel sheets during atmospheric-pressure (AP) plasma treatment using different process gases: O2, N2, and compressed air was investigated. The plasma-induced radicals promoted the formation of chemical particles on the surface of the Zn-Mg-Al coating, thereby increasing the surface roughness. The surface energy was calculated using the Owen-Wendt geometric equation. Contact angle measurements indicated that the surface free energy of the alloy sheets increased upon AP plasma treatment. The surface properties of the Zn-Mg-Al coating changed more significantly in the order air > O2 > N2 gas, indicating that the plasma radicals facilitated the carbonization and hydroxylation of the Mg and Al components during the AP plasma treatment.

Effect of Sintering Holding Time and Cooling Rate on the Austenite Stability and Mechanical Properties of Nanocrystalline FeCrC Alloy

Kim Gwanghun, Jeon Junhyub, Seo Namhyuk, Choi Seunggyu, Oh Min-Suk, Son Seung Bae, Lee Seok-Jae

Archives of Metallurgy and Materials

2021

Vol. 66, iss. 3

759--763

The effects of the sintering holding time and cooling rate on the microstructure and mechanical properties of nanocrystalline Fe-Cr-C alloy were investigated. Nanocrystalline Fe-1.5Cr-1C (wt.%) alloy was fabricated by mechanical alloying and spark plasma sintering. Different process conditions were applied to fabricate the sintered samples. The phase fraction and grain size were measured using X-ray powder diffraction and confirmed by electron backscatter diffraction. The stability and volume fraction of the austenite phase, which could affect the mechanical properties of the Fe-based alloy, were calculated using an empirical equation. The sample names consist of a number and a letter, which correspond to the holding time and cooling method, respectively. For the 0A, 0W, 10A, and 10W samples, the volume fraction was measured at 5.56, 44.95, 6.15, and 61.44 vol.%. To evaluate the mechanical properties, the hardness of 0A, 0W, 10A, and 10W samples were measured as 44.6, 63.1, 42.5, and 53.8 HRC. These results show that there is a difference in carbon diffusion and solubility depending on the sintering holding time and cooling rate.