Metallurgy of continuous hot dip aluminizing

Richards, R. W.; Jones, R. D.; Clements, P.D.; Clarke, Hyde

doi:10.1179/imr.1994.39.5.191

Cited by 208 publications

(148 citation statements)

References 54 publications

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“…1) has been reported as the t5 phase in previous publications. 9,13) The purpose of Si addition in type 1 aluminized coating is to form a Fe 2 SiAl 7 inhibition layer at the interface between coating and substrate steel. The presence of this inhibition layer can suppress the formation and growth of intermetallic compounds FeAl 3 and Fe 2 Al 5 which impair coating adherence and formability.…”

Section: Discussionmentioning

confidence: 99%

Coating Degradation in Hot Press Forming

Fan

Kim

et al. 2010

ISIJ Int.

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The thermo-mechanically induced microstructure changes occurring in a type 1 aluminized coating on hot press forming (HPF) steel were studied in detail. The formation of intermetallic phases at the soaking temperature prior to die quenching revealed that the coating matrix consists mainly of FeAl 2 intermetallic phase by the time the press forming carried out. Kirkendall void formation was observed to take place. The thermal oxidation of aluminized coating during HPF was found to be limited, with the coating acting as an effective barrier for the oxygen during heating. The deterioration caused by the high temperature plastic deformation was shown to lead to coating cracking without loss of adhesion. The steel surface was oxidized where it was exposed between the coating segments.KEY WORDS: hot press forming; aluminized; intermetallic; diffusion; Kirkendall voids. 561© 2010 ISIJ steels are coated with a 25 mm thick Al-10wt%Si type 1 coating. Type 2 coating consists of pure aluminum, and is used mainly for high reflectivity surface appearance, such as building cladding panels and ventilation systems. The typical thickness of type 2 coating is 38-60 mm. 9) ExperimentalThe material used in the present study was cold rolled and continuous hot dipped Al-10wt%Si aluminized steel sheet of 1.6 mm thickness supplied by the POSCO Technical Research Laboratories. The steel chemical composition is given in Table 1. The steel is a CMn steel with additions mainly of Cr and B. Carbon, an austenite stabilizer, is the most effective strengthening elements for martensite via the mechanism of interstitial solute strengthening. Weldability requirements limit the carbon equivalent to a maximum of about 0.5. A carbon content of 0.2 wt% C ensures the decomposition of austenite into a high strength lath martensite microstructure when relatively low cooling rates are used, providing B-additions are made. Mn is an effective hardening addition as it retards most austenite decomposition reactions. Cr is another strong hardenability agent, which effectively suppresses the bainite transformation. B is added to HPF steels to increase the hardenability by etarding the heterogeneous nucleation of ferrite at the austenite grain boundaries. Additions of Al and Ti are often used to avoid the formation of BN. AlN or TiN precipitates are formed as instead. TiN also suppresses grain growth. 10,11) Rectangular specimens with dimension of 40ϫ150 mm were cut. Their weight was approximately 100 g. The specimens had large enough surfaces to minimize the effect of the increased weight caused by the oxidation of the cut edges during high temperature tests. The specimens were transferred to a box furnace with a stationary air atmosphere and kept at 930°C for 2-120 min. The specimens were then removed from the furnace and cooled in air to room temperature. The specimens were weighted before and after the heat treatment. The specimens were grinded and polished with a 1 mm diamond suspension. The cross sectional specimens were not etched in order to avoid the me...

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Section: Discussionmentioning

confidence: 99%

Coating Degradation in Hot Press Forming

Fan

Kim

et al. 2010

ISIJ Int.

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“…6) It is assumed that an Al-Fe-Si intermetallic compound is formed in the interface between the coating and steel substrate and that this subdues the rapid growth of the Al-Fe intermetallic compound. 7) Nevertheless, studies on the growth control of AlFe intermetallic compounds using Si addition are conducted principally regarding hot-dip Al coating baths 7) or hot-dip Al-Zn coating baths 8) with a high Al content, and there have been few studies on baths with a low Al content.…”

Section: Introductionmentioning

confidence: 99%

Influence of Si Addition to the Coating Bath on the Growth of the Al–Fe Alloy Layer in Hot-dip Zn–Al–Mg Alloy-coated Steel Sheets

2011

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The influence of Si addition to the coating bath on the growth of the Al-Fe alloy layer formed in the interface between the coating and steel substrate was studied utilizing a Zn-Al-Mg coating bath with 10-11 mass% Al content. While the Al-Fe intermetallic compound rapidly grew in the interface between the coating and steel substrate when dipped into a coating bath of Zn-10mass%Al-3mass%Mg at 550°C, the growth was remarkably suppressed by the addition of 0.2mass%Si to the coating bath. TEM observation revealed that, in the interface between the coating and the substrate, Si addition resulted in the uniform formation of very fine grains of 20-30 nm in diameter in the Fe2Al5 phase with dissolved Si and Zn in a solid solution. The mechanism of Si addition was postulated to be as follows: the large amount of Fe in the substrate could be dissolved easily into the liquid phase in the case of a ternary Fe-Al-Zn system, whereas in the case of a quaternary Fe-Al-Zn-Si system, the dissolution of Fe into the liquid phase was significantly suppressed by the presence of very fine, thin Fe2Al5 containing Si in the interface between the coating and the steel substrate. Thus, the growth rate of Fe2Al5 was greatly reduced.

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“…6 which can be generated by means of the Kirkendal effect. [24][25][26] Next, the microstructures of both the coating and the inter-diffusion layer have been changed through continuous diffusional interaction with the substrate. In addition, a new microstructural morphology is observed at the bottom of the Al-Fe coating layer.…”

Section: Influence Of Inward Diffusion Of Al On the Lifetime Of Al-fementioning

confidence: 99%

Influence of Aluminum Depletion on the Lifetime of an Al-Fe Coating in Eutectic (Li,K)<SUB>2</SUB>CO<SUB>3</SUB> at 650°C

Jun

Kim

2003

Mater. Trans.

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Metallurgy of continuous hot dip aluminizing

Cited by 208 publications

References 54 publications

Coating Degradation in Hot Press Forming

Coating Degradation in Hot Press Forming

Influence of Si Addition to the Coating Bath on the Growth of the Al–Fe Alloy Layer in Hot-dip Zn–Al–Mg Alloy-coated Steel Sheets

Influence of Aluminum Depletion on the Lifetime of an Al-Fe Coating in Eutectic (Li,K)<SUB>2</SUB>CO<SUB>3</SUB> at 650°C

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Metallurgy of continuous hot dip aluminizing

Cited by 208 publications

References 54 publications

Coating Degradation in Hot Press Forming

Coating Degradation in Hot Press Forming

Influence of Si Addition to the Coating Bath on the Growth of the Al–Fe Alloy Layer in Hot-dip Zn–Al–Mg Alloy-coated Steel Sheets

Influence of Aluminum Depletion on the Lifetime of an Al-Fe Coating in Eutectic (Li,K)<SUB>2</SUB>CO<SUB>3</SUB> at 650&deg;C

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Influence of Aluminum Depletion on the Lifetime of an Al-Fe Coating in Eutectic (Li,K)<SUB>2</SUB>CO<SUB>3</SUB> at 650°C