Papers by Keyword: Hot-Dip Galvanizing

Abstract: In view of the problem of bulge particle defect on the surface of hot-dip galvanized sheets, the causes were analyzed by investigating defect characteristics and surface cleanliness of cold-rolled steel sheets. The results show that the cause of bugle particle defect lies mainly in the residual iron on the surface of cold rolled steel sheets, which has not been cleaning off during degreasing and interfere the normal formation of coating. The bugle particle defect can be effectively prevented when the laser-textured work rollers of No.1 stand of HC tandem cold mills are replaced by smooth rollers, because the residual iron on the surface of cold rolled steel sheets can be reduced obviously.

Abstract: Simulation techniques play a crucial role in determining a successful engineering design. A multifunctional galvanizing simulator is the basic equipment for enterprise to acquire the process information for producing annealed sheets, galvanized sheets and galvannealed sheets under laboratory conditions. This paper extended Geros function-behavior-structure framework and used this framework for the conceptual design of a multifunctional hot-dip galvanizing simulator.

Abstract: The study describes the mechanism of structure formation in protective coating, growing on iron surface during hot-dip galvanizing. As a first stage of the galvanizing process, immediately after the iron sample has been dipped in galvanizing bath, a layer of frozen zinc is crystallizing on the sample surface. Next, as a result of isothermal solidification, an alloyed layer of the coating; composed of the sub-layers of intermetallic Fe-Zn phases, is formed. At the initial stage of the existence of the alloyed layer, another layer, that of undercooled liquid, is formed on the surface of iron dipped in liquid zinc. As a result of peritectic reactions under metastable conditions, the individual phases are born, forming sub-layers in the expected sequence of Γ1, δ and ζ.

Abstract: This article takes the natural gas hot-dip galvanizing kiln as the research object, designing a set of networked control system based on PROFIBUS, introducing the combustion system design of the natural gas kiln and the general structure of control system, and developing PLC control program and human-computer interface of the upper computer, and realizing network monitoring. It has been found that the stably running system provides powerful tools for product quality control and optimal operation management.

Abstract: Nowadays the most commonly used baths for hot-dip galvanizing are the ones which contain about 0.1 ... 0.2% of aluminium. Besides aluminium, the effects of the addition of small quantities of titanium (up to 0.0005%) to the bath have recently been studied in detail by Culcasi et al. [2]. They proved the strong impact of adding a small amount of titanium on the development of the iron-zinc layer, which influences primarily the building up of the intermetallic compound film Fe₂Al₅ on the surface of the steel piece in contact with the molten zinc. This aluminium-alloyed hot-dip bath with titanium usually does not form a nicely coloured surface [. Therefore, our experiments were limited to test only the effect of adding titanium to the molten zinc which contains only traces of aluminium in order to study the impact of titanium on surface colouring using GD-OES spectrometry.

Abstract: Bolt connection is a usual connection in power transmission and power transformation steel structures, and preservative treatments such as rust removal and galvanization are adopted to protect the bolts. In order to investigate the influence of hot-dip galvanizing on the tensile strength of bolt, common strength bolts and high strength bolt produced in four factories were tested to gain tensile strength. The results indicate that hot-dip galvanizing may reduce the tensile strength of bolts, and galvanizing technics of different factory have difference influence on the tensile strength of bolts.

Abstract: The influence of manganese in Zn-Mn and Zn-0.2wt.%Al-Mn bath on the morphology and growth kinetics of the galvanizing coatings has been studied using scanning electron microscopy equipped with energy dispersive spectroscopy. When galvanized in zinc bath, the coating consists mainly h and ζphase. When manganese is added in zinc bath, the morphology of ζ phase changes from fragmental to compact. Manganese favors the formation of the δ phase and inhibits the growth of the ζ phase.When galvanized in Zn-0.2wt.%Al bath, the coating consists only δ and h phase. With the addition of manganese in Zn-0.2wt.%Al bath, the morphology of δ phase changes from fragmental to compact The thickness of the Fe-Zn intermetallic phase layer in coatings decreases obviously when manganese is added into zinc and Zn-0.2wt.%Al bath, and the thickness increases slowly with the increase of immersion time.

Abstract: To understand the role of annealing conditions on the segregation and selective oxidation phenomena, Fe 2Mn 2Si 0.8Cr (all in wt.%) model alloy was investigated. The samples were annealed at 820°C in N2-5%H2 forming gas atmospheres over a wide range of dew pints (-80 to 0°C) with dwelling time of 1 to 5 minutes. At all dew points, the strong chemical interaction between Mn and Si causes the formation of manganese silicates. External oxidation of Mn, Si and Cr were decreased at the higher dew points. Increasing the dwelling time shows an extended oxidation front i.e. pronounced external/internal oxidation of Mn, Si and Cr. Basically, the present work addresses the two stages of oxidation front.

Abstract: High strength steels for automotive industry undergo recrystallization annealing in N2-H2 gas atmosphere prior to hot dip galvanizing. Segregation and selective surface oxidation of the alloying elements (Al, Mn, Si, Cr etc.) depending on their extend, can be a serious problem for subsequent galvanizing as the wettability of these oxides with zinc is poor. Moreover, the H2 uptake from the annealing atmosphere majorly depends on the surface evolution during recrystallization annealing. In order to understand the surface phenomena during annealing of multicomponent alloy (i.e. steel), a systematic approach on model alloys is needed. In this work, selective surface oxidation of Mn, Al and the reduction of native Fe oxides in Fe 2 wt. % Mn and Fe 3 wt. % Al binary model alloys have been investigated by interrupting the recrystallization annealing cycle at the desired temperature. The specimens were annealed to various temperatures (200-800 °C) in N2-5%H2 gas atmospheres with a dew point of 30 °C. It has been found that the segregation and selective oxidation of the alloying elements starts at 300 °C whereas the significant reduction of native Fe oxides takes place at 400 °C. Further increase of temperature, increases the surface coverage by forming the oxide islands.

Abstract: Investigating the changing quality of galvanized parts when pure zinc plated with other alloying additions. In the procedure of hot dip galvanizing, when pure zinc plated without other alloying additions, the corrosion resistance of zinc coating is poor, meanwhile the bath surface will produce a number of zinc dross, zinc ash, and this phenomenon will cause a waste of zinc, resulting in an increase in product costs, and the surface of product is relatively dark, the brightness is not enough, whilst sometimes even form a phenomenon of the formation of the Pan-color on the surface of the galvanized parts. However, when a proportion of aluminum or rare earth elements is added into melting zinc, the corrosion resistance of coating will be improved and much better than pure zinc galvanized parts;as the decrease of zinc ash, the cost will be reduced;synchronously the limititation of superficial quality above-mentioned will be improved. Via evaluating the superficial quality of galvanized parts and the corrosion resistance, the whole performance will be significantly improved when 0.5% aluminum and 1.5% rare earth elements is added into melting zinc.