• Corrosion Science and Technology
• /
• v.9 no.4
• /
• pp.159-163
• /
• 2010

Precise coating weight control is very important issue on quality and minimizing operating costs on continuous galvanizing line. These days, many steel making companies are having a new understanding of cost importance by rise raw material prices and customer's requirement for cost reduction. Dongbu steel also meets these situations and decided to develop the technologies. Dongbu Steel developed Integrated coating weight control system jointly with Objective Control Ltd. and installed 2CGL and 4CGL. Several technological functions were developed and realized to achieve true hands-off operation and maximum cost benefit by combining model-based preset and dynamic prediction models. We also installed it on 1 CGL on April, 2008. This paper will present the interface, functions and application result of the integrated coating weight control system including Zn saving and coating weight uniformity.

• Corrosion Science and Technology
• /
• v.23 no.3
• /
• pp.228-234
• /
• 2024

Zinc wiping is a phenomenon used to control zinc-coating thickness on steel substrate during hot dip galvanizing by equipment called air knife. Uniformity of zinc coating weight in length and width profile along with surface quality are most critical quality parameters of galvanized steel. Deviation from tolerance level of coating thickness causes issues like overcoating (excess consumption of costly zinc) or undercoating leading to rejections due to non-compliance of customer requirement. Main contributor of deviation from target coating weight is dynamic change in air knives equipment setup when thickness, width, and type of substrate changes. Additionally, cold coating measurement gauge measure coating weight after solidification but are installed down the line from air knife resulting in delayed feedback. This study presents a coating weight control model (Galvantage) predicting critical air knife parameters air pressure, knife distance from strip and line speed for coating control. A reverse engineering approach is adopted to design a predictive, prescriptive, and descriptive model recommending air knife setups that estimate air knife distance and expected coating weight in real time. Implementation of this model eliminates feedback lag experienced due to location of coating gauge and achieving setup without trial-error by operator.

• 제어로봇시스템학회:학술대회논문집
• /
• 2001.10a
• /
• pp.121.5-121
• /
• 2001

For the last decade, remarkable progress in the coating weight uniformity of hot dip galvanized product has been made to overcome the tightening quality constraints and produce cost-effective galvanized products. This progress results from research and development works for more efficient air knife, more accurate model of coating process, more precise measurement of coating weight and more efficient control logics. The activities for an efficient mathematical model to predict coating weight and several control logics which has been implemented on the No.1 CGL, No. 2 CGL, and PGL at KwangYang Steel Works are reviewed in this article.

• Corrosion Science and Technology
• /
• v.9 no.3
• /
• pp.105-108
• /
• 2010

The product specification of the Continuous Hot Dip Galvanizing Line (CGL) changes and varies constantly with different customers' requirements, especially in the zinc coating weight which is from 30 to 150 g/$m^2$ on each side. Since the coating weight of zinc changes often, it is very important to reduce time spent in the transfer of target values changed for low production cost and yield loss. The No.2 CGL in China Steel Corporation (CSC) has improved the control of the air knife which is designed by Siemens VAI. CSC proposed an experiment design which is an $L_9(3^4)$ orthogonal array to find the relations between zinc coating weight and the process parameters, such as the line speed, air pressure, gap of air knife and air knife position. A non-linear regression formula was derived from the experimental results and applied in the mathematical model. A new air knife feedforward control system, which is coupled with the regression formula, the air knife control system and the process computer, is implemented into the line. The practical plant operation results have been presented to show the transfer time is obviously shortened while zinc coating weight target changing and the product rejected ratio caused by zinc coating weight out of specification is significantly reduced from 0.5% to 0.15 %.

• Journal of Advanced Marine Engineering and Technology
• /
• v.24 no.3
• /
• pp.20-28
• /
• 2000

Air wiping technique is widely used because of easy and efficient coating control in present CGL The coating weight is controlled by nozzle header pressure. strip line speed, and the distance between strip and nozzle. Coating defects are resulted from the unbalance of these control factors and the inaccuracy of coating equipments. We investigates the main cause of coating defects, such as edge overcoating and coating deviation through various experiments. It is found that the edge overcoating is mainly come from nozzle lip type, and the coating deviation is caused by the unbalance of dynamic pressure.

• Korean Journal of Organic Agriculture
• /
• v.6 no.1
• /
• pp.51-61
• /
• 1997

This experiment was carried out to investigate the growth response of 3 grasses to seed coating with chitosan solution and the attempt was made to estimate adequate seed coating concentrations of chitosan solution in each grass for the growth to be stimulated. Three species used in this experiment were orchardgrass, tall fescue and reed canarygrass. Six different seed coating concentrations of chitosan solution were applied as 0%(control), 0.01%, 0.05%, 0.1% and 1.0%, respectively. the results were obtained as follows; 1. Dry weight of tiller(WT), leaf area(LA), dry weight of leaf(LW), dry weight of stem(SW), dry weight of shoot(SHW), biological yield(BY) and C/F ratio were significantly different between species. 2. Number of tillers per plant(NT), dry weight of tiller(WT), dry weight of leaf(LW), dry weight of root(RW), dry weight of shoot(SHW), biological yield(BY) and T/R ration were significantly different between seed coating concentrations of chitosan solution. 3. The adequate seed coating concentrations of chitosan solution for the growth stimulating effect were different between species. The highest values of yield components and dry weight of plant parts were obtained at 1% in orchardgrass and tall fescue, and 0.05% in reed canarygrass, respectively. 4. Growth stimulating effect of seed coating in each species were different. The highest values were obtained in leaf area(LA), dry weight of leaf(LW), dry weight of root(RW), dry weight of shoot(SHW) and dry weight of biological yield(BY) in orchardgrass. The values of dry weight of stem(SW) and C/F ration were highest in reed canarygrass. 5. An increase in number of tillers per plant(NT), dry weight of leaf(LW), dry weight of stem(SW) and dry weight of root(RW) according to seed coating was attributed to the increase in dry weight of shoot(SHW). Among the aboved increasing factors, the dry weight of leaf(LW) was a main factor for the increase in dry weight of shoot(SHW). 6. An increase in dry weight of leaf(LW), dry weight of stem(SW) and dry weight of root(RW) according to seed coating was attributed to the increase in biological yield(BY). Both the dry weight of leaf(LW) and dry weight of root(RW) were main factors for the increase in biological yield(BY).

• 제어로봇시스템학회:학술대회논문집
• /
• 1995.10a
• /
• pp.323-327
• /
• 1995

A new air knife system for coating thickness control in hot dip galvanizing process had been developed and installed on the CGL in Pohang Steel Works, POSCO. This new system consists of air knives with remotely adjustable nozzle slot and an automatic control system which can control both longitudinal and traverse coating deviations. Based on the optimal control algorithm, a traverse coating deviation control was designed. The controller controls the lip profile of the air knives with flexible structure according to the deviation of coating weight. From the measured values which are dependent on the strip width, the lip gaps are calculated with optimal algorithm and the model of the coating deviation. Time delay between knives and a coating thickness gauge is solved by the Smith Predictor.

• Journal of Fisheries and Marine Sciences Education
• /
• v.11 no.2
• /
• pp.139-149
• /
• 1999

Thermal sprayed Ni-Cr alloy coating on the carbon steel was carried out erosion-corrosion test and electrochemical corrosion test in the marine environment. The erosion-corrosion behavior and electrochemical corrosion characteristics of substrate(SS400) and thermal sprayed Ni-Cr coating was investigated. The erosion-corrosion control efficiency of Ni-Cr coating to substrate was also estimated quantitatively. The main results obtained are as follows : 1) The weight loss rate of Ni-Cr coating layer by the erosion-corrosion compared with substrate was smaller. With the lapse of time, the weight loss rate of substrate was linearly increased in $25{\Omega}{\cdot}cm$ solution, but that of Ni-Cr coating became stable. 2) The corrosion potential of substrate became less noble than that of Ni-Cr coating layer, and the corrosion current density of Ni-Cr coating became lower than that of substrate. 3) The control efficiency of erosion-corrosion of Ni-Cr coating compared to substrate became more dull than that of corrosion in $25{\Omega}{\cdot}cm$ and $5000{\Omega}{\cdot}cm$ solution.

• Proceedings of the KIEE Conference
• /
• 1995.07b
• /
• pp.892-894
• /
• 1995

This paper deals with developmeant and application of coating thickness control system in hot dip galvanizing process. According to the line conditions, such as line speed, strip size and target coating weight, a predictive preset model sets the initial oprating conditions. Referring the zine coating informations from the gauge, mean coating value controller adjusts the chamber pressure and horizontal distance between strip and air knife, while coating deviation controller adjusts the lip gap profile of the air knife. All adaptive gains are interactively calculated by numeric models based on the theoretical analysis. The operating result with this system effectively reduces the coating deviation in transverse direction as well as in longitudinal direction.

• Journal of Advanced Marine Engineering and Technology
• /
• v.26 no.2
• /
• pp.192-199
• /
• 2002

In continuous galvanizing process, the mass of zinc deposited and its distribution are controlled by the air pressure, effective distance from the air knife nozzle to the steel strip surface and line speed. Coating defects are resulted from the unbalance of these control factors and the inaccuracy of coating equipments. This paper investigates the main cause of coating deviation and a new air knife system for control of coating thickness was developed. We investigate dynamic pressure variation by air knife types. It is found that the coating deviation is caused by the unbalance of dynamic pressure, the irregularity of strip position, and the strip vibration. Formulating a useful coating model by using present working condition, an optimal working condition is suggested. The productivity and coating quality are improved by applying the result of this research at the shop floor.