• 한국기계가공학회지
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• 제1권1호
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• pp.71-78
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• 2002

Since the early 1980's the use of zinc-aluminum alloy-coated steel sheet(Galvalume) for vehicular corrosion protection has increased drastically. It is consisting of 55%Al-43.4% Zn-1.6%Si. Galvalume has a good corrosion resistance, heat reflectivity and shiny appearance, which has a dendritic structure of alloy layer. It has a good corrosion resistance due to dendritic structure. But, this also has a weak point against moisture during long period of transportation as sheeted and or coiled without any relation of chromating on the surface of steel sheet or not because of high humidity and temperature. Here, We studied the corrosion mechanism by the moisture.

• Journal of Welding and Joining
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• 제16권1호
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• pp.52-62
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• 1998

Laser beam welding of zinc-coated steel, especially lap joints, has a problem of zinc vapor produced during welding which has a low vaporization temperature of 906.deg. C. It is lower than the melting temperature of steel (1500.deg. C). The high pressure formed by vaporization of zinc during laser welding splatters the molten pool and creates porosities in weld. During laser lap welds of zinc-coated steel sheets with CW CO$_{2}$ laser the gap size has been analyzed and simulated using a FEM. The simulation has been carried out in the range of gap aetween 0 and 0.16 mm. The vaporized zinc gas has effected to prevent heat from conducting toward the bottom of sheets. In vaporized zinc gas has effected to prevent heat from conducting toward the bottom of sheets. In the case of too small gap size, zinc gas has not ejected and existed between two sheets. Therefore heat was difficult to conduct from the upper sheet to lower sheet and the upper sheet could over-melted. In the case of large gap size the zinc gas has been prefectly ejected but only a part of lower sheet has melted. The optimum range of gap size in the lap welds of zinc-coated steel sheets has been calculated to be between 0.08 and 0.12 mm. According to the comparison of experiment, the simulation is proved to be acceptable and applicable to laser lap welds.

• 열처리공학회지
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• 제6권2호
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• pp.89-97
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• 1993

An improvement in corrosion resistance of various types of Zn-coated steel sheets is thought to be possible with the addition of fine oxide powder to the coating. In this study the corrosion resistance of the $Al_2O_3$ dispersed Zn-Co-Cr electroplated steel sheet has been investigated and the results were as follows : The corrosion resistance of $Al_2O_3$ dispersed Zn-Co-Cr electroplated steel sheets was improved by increasing the contents of Co and Cr ions, and also $Al_2O_3$ powders in the bath because of the increased amount of Co, Cr and $Al_2O_3$ in deposits. In the $Al_2O_3$ dispersed Zn-Co-Cr electroplated steels sheet, the structure of deposits was changed from fine microstructure as observed in high Co containing deposits to coarse microstructure as in high Cr and $Al_2O_3$ containing deposits. By cold rolling of the $Al_2O_3$ dispersed Zn-Co-Cr electroplated steel sheets to about 2 percent, thr corrosion resistance was improved further.

• Corrosion Science and Technology
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• 제20권1호
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• pp.7-14
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• 2021

PosMAC^® is a brand of Zn-Mg-Al hot-dip coated steel sheet developed by POSCO. PosMAC^® can form dense surface oxides in corrosive environments, providing advanced corrosion resistance compared to traditional Zn coatings such as GI and GA. PosMAC^® 3.0 is available for construction and solar energy systems in severe outdoor environments. PosMAC^®1.5 has better surface quality. It is suitable for automotive and home appliances. Compared to GI and GA, PosMAC^® shows significantly less weight reduction due to corrosion, even with a lower coating thickness. Thin coating of PosMAC^® provides advanced quality and productivity in arc welding applications due to its less generation of Zn fume and spatters. In repeated friction tests, PosMAC^® showed lower surface friction coefficient than conventional coatings such as GA, GI, and lubricant film coated GA. Industrial demand for PosMAC^® steel is expected to increase in the near future due to benefits of anti-corrosion and robust application performance of PosMAC^® steel.

• 대한금속재료학회지
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• 제48권6호
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• pp.533-542
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• 2010

The specific motivation for joining an Al alloy and Zn-coated steel arises from the need to save fuel consumption by weight reduction and to enhance the durability of vehicle structures in the automobile industry. In this study, the lap joining A6K31 Al alloy (top) and SGARC340 Zn-coated steel (bottom) sheets with a thickness of 1.0 mm and 0.8 mm, respectively, was carried out using the friction stir weld (FSW) technique. The probe of a tool did not contact the surface of the lower Zn-coated steel sheet. The friction stir welding was carried out at rotation speeds of 1500 rpm and travel speeds of 80~200 mm/min. The effects of tool geometry and welding speed on the mechanical properties and the structure of a joint were investigated. The tensile properties for the joints welded with a larger tool were better than those for the joints done with a smaller tool. A good correlation between the tensile load and area of the welded region were observed. The bond strength using a larger tool (M4 and M3) decreased with an increase in welding speed. Most fractures occurred along the interface between the Zn-coated steel and the Al alloy. However, in certain conditions with a lower welding speed, fractures occurred at the A6K31 Al alloy.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 1998년도 특별강연 및 추계학술발표 개요집
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• pp.303-304
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• 1998

• Journal of Welding and Joining
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• 제18권2호
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• pp.196-196
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• 2000

Formation of the weld defect, such as a blowhole and a pit in lap-jointed fillet arc welds has been a serious problem in arc welding of Zn-coated steel sheet. In this study, the relationship among welding conditions, welding materials and defect formation was investigated in order to minimize these defects in the CO₂ welds. In addition, the arc stability of the commercial welding wires was evaluated for revealing their effects on defect formation. Main conclusions obtained are as follows:1) There was no difference between shear tensile strength of the sound welds and that of the welds with blowholes whose diameters are less than 0.5mm. However, the welds with blowholes whose diameters are equal or larger than 0.5mm and pits exhibited tensile strength 10~20% and 30~40% lower than that of the sound welds respectively.2) The optimum welding condition to effectively prevent or reduce the weld defects formation are as follows:- The welding variables of 220A-23V-100cm/min and 120A-190V-30cm/min were recommended for minimizing the weld defects.- The gap between the two sheets at the lap-joint should be controlled to more than 0.2mm- Solid wire was less susceptible to the formation of the weld defects than the flux-cored wire.- The low welding current condition produced less weld defects than the hihg welding current condition.3) One of the reason why the amount of the defect was reduced at the low welding current was the gas discharging by the active agitation of the molten pool, due to an increasing in the number of the short circuit. (Received September 27, 1999)

• Journal of Welding and Joining
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• 제18권2호
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• pp.69-76
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• 2000

Formation of the weld defect, such as a blowhole and a pit in lap-jointed fillet arc welds has been a serious problem in arc welding Zn-coated steel sheet. In this study, the relationship among welding conditions, welding materials and defect formation was investigated in order to minimize these defects in the CO₂welds. In addition, the arc stability of the commercial welding wires was evaluated for revealing their effects on defect formation. Main conclusions obtained are as follows: 1) There was no difference between shear tensile strength of the sound welds and that of the welds with blowholes whose diameters are less than 0.5mm. However, the welds with blowholes whose diameters are equal or large than 0.5mm and pits exhibited tensile strength 10∼ 20% and 30∼40% lower than that of the sound welds respectively. 2) The optimum welding condition to effectively prevent or reduce the weld defects formation are as follows: -The welding variables of 220A-23V-100cm/min and 120A-19V-30cm/min were recommended for minimizing the weld defects. -The gap between the two sheets at the lap-joint should be controlled to more than 0.2mm. -Solid wire was less susceptible to the formation of the weld defects than the flux-cored wire. -The low welding current condition produced less weld defects than the high welding current condition. 3) One of the reason why the amount of the defect was reduced at the low welding current was the gas discharging by the active agitation of the molten pool, due to an increasing in the number of the short circuit.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2006년도 전기학술대회논문집
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• pp.271-272
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• 2006

Zinc confers high corrosion resistance by acting as a sacrificial anode, and a zinc coating improves the appearance of steel. Chromate conversion coating (CCC) films are still one of the most efficient surface treatments for steel. Although such films can self-repair via the dissolution of Cr(VI), dissolved Cr(VI) have adverse effects on humans, and the environment. Therefore, we examined the corrosion protection property and morphology of colloidal silica conversion films as an alternative to CCC films. The corrosion behavior was investigated in 3% NaCl solution using electrochemical techniques, including electrochemical impedance spectroscopy, open circuit potential, and the salt spray test(SST). Corrosion was implied by the appearance of red rust on the specimen surface. In corrosion resistance at 3% NaCl solution, red rust appeared at 15-20, 55-70, and 83-98 days on Zn-electroplated steel, colloidal silica conversion-coated specimens, and CCC-coated specimens, respectively. In the salt spray test, the colloidal silica film provided better corrosion protection than CCC films, i.e., red rust appeared at 96 hours on the Zn-electroplated steel sheet, at 432 hours with the CCC films, and at 888 hours with silica conversion coating.

• 한국표면공학회지
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• 제34권4호
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• pp.313-320
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• 2001

It is well known that the amount of hot-dip Zn coated sheet steels used for automotive is rapidly increasing. As hot-dip steel sheets show good corrosion resistance and excellent formability, the demand for outer panel of automotive has been increased in order to satisfy with the requirement of high surface qualify. There are many kinds of factors influencing on the surface quality and the dross control in the galvanising bath is regarded as one of the most important thing. In this study the characteristic and growing behavior of dross in the galvanizing bath were investigated and the effect of dross on the surface defect of GA was surveyed. The dross defects on the GA sheet steels result from bottom dross whose diameter are larger 50$\mu\textrm{m}$ in the Zn pot. Dross-free state exist for about 30 hours from starting time of GA production.