Galvanizing Line Research Articles

Application Research of Slag-removing Robot for Zinc pot on Hot-dip Galvanizing Line

Metallurgical industry mostly works in high temperature, high pressure, dusty and other harsh environment, where applied research Metallurgy robots started late. In recent years, the application research of metallurgical robots has gradually gained the attention of everyone. The hot dip galvanizing pot slag is usually operated manually, the working environment of the workers is bad, there is with a large safety hazard, and the process of controlling the slag is difficult. The use of slag-removing robot instead of labor is applied to the hot-dip galvanizing line, which is the trend of intelligent and automated development of the coating industry.

Accurate Online Measurement of Iron Concentration in Galvannealed Coating Layers by Shift of X-ray Diffraction Peak

The authors have developed a new online measurement system for the Fe concentration in galvannealed (GA) coatings based on the proportionality between the peak angle of X-rays diffracted by the δ1 phase and the Fe concentration. The online system was realized by high-speed measurement of the peak angle of diffracted X-rays using a one-dimensional detector in conjunction with correction algorithm for the angular error caused by the displacement of the GA steel strip surface from the measurement position. The performance of the developed online system was demonstrated in a continuous galvanizing line with GA strips of Si-added and Si-free base steels. The developed system showed higher accuracy even with the Si-added base steel, with which enough accuracy could not be obtained with conventional online systems based on the diffraction intensity of the Γ phase. Since the δ1 phase is the major phase of GA coatings, the main advantage of the developed system is that its accuracy is less sensitive to the composition of the base steel.

Effect of Mn and Cr on the selective oxidation, surface segregation and hot-dip Zn coatability

The effect of Mn and Cr on the surface selective oxidation, segregation and hot-dip galvanizing was studied in three Fe-Mn alloys with ∼0.2 wt% Al and two Fe − Mn alloys with ∼0.5 wt% Cr in an HDPS (Hot-dip Process Simulator) following industrial CGL (Continuous Galvanizing Line) conditions. The Mn content was varied from 1.5 to 3.6 wt% in the alloys. The alloys were subjected to the same thermal cycle following continuous annealing (CA) at 800 °C in N2 − 5%H2 gas atmosphere with −40 °C dew point and then hot-dipping in Zn - 0.20 wt% Al bath at 460 °C. The oxidation tendency of Mn, Al and Cr during annealing was calculated using FactSage software. GDOES (Glow Discharge Optical Emission Spectroscopy) measurements showed a higher extent and depth of segregation for Mn with increasing bulk concentration during the CA. It was observed that Cr segregates comparatively less near the annealed surface in the presence of more Mn. XPS (X-ray Photoelectron Spectroscopy) measurements revealed the formation of simple MnO in Fe-Mn-Al alloys and complex MnCr2O4 in Fe-Mn-Cr alloys. Contrary to the thermodynamic calculations, no Al-oxides were detected at the annealed surfaces of Fe-Mn-Al alloys during the XPS study. The hot-dip Zn coatability was determined by measuring the number density of uncoated spots using 3D CLSM (Confocal Laser Scanning Microscopy) and by visual inspection. The Fe-Mn-Cr alloys displayed a better hot-dip Zn-coating compared to Fe-Mn-Al alloys. The conclusions of the present study are also critically discussed considering the literature findings.

Optimization of the Continuous Galvanizing Heat Treatment Process in Ultra-High Strength Dual Phase Steels Using a Multivariate Model

The main process variables to produce galvanized dual phase (DP) steel sheets in continuous galvanizing lines are time and temperature of intercritical austenitizing (tIA and TIA), cooling rate (CR1) after intercritical austenitizing, holding time at the galvanizing temperature (tG) and finally the cooling rate (CR2) to room temperature. In this research work, the effects of CR1, tG and CR2 on the ultimate tensile strength (UTS), yield strength (YS), and elongation (EL) of cold rolled low carbon steel were investigated by applying an experimental central composite design and a multivariate regression model. A multi-objective optimization and the Pareto Front were used for the optimization of the continuous galvanizing heat treatments. Typical thermal cycles applied for the production of continuous galvanized AHSS-DP strips were simulated in a quenching dilatometer using miniature tensile specimens. The experimental results of UTS, YS and EL were used to fit the multivariate regression model for the prediction of these mechanical properties from the processing parameters (CR1, tG and CR2). In general, the results show that the proposed multivariate model correctly predicts the mechanical properties of UTS, YS and %EL for DP steels processed under continuous galvanizing conditions. Furthermore, it is demonstrated that the phase transformations that take place during the optimized tG (galvanizing time) play a dominant role in determining the values of the mechanical properties of the DP steel. The production of hot-dip galvanized DP steels with a minimum tensile strength of 1100 MPa is possible by applying the proposed methodology. The results provide important scientific and technological knowledge about the annealing/galvanizing thermal cycle effects on the microstructure and mechanical properties of DP steels.

Failure analysis of weld joint of high strength quality steel sheets in cold rolling mill

Zinc coating (galvanizing) provides maintenance free, long lasting corrosion protection at a reasonable cost for years. Continuous galvanizing line facilitates the application of such coating onto the steel sheet. For continuous operation, it becomes necessary to join two sheets across their width. Resistance seam welding is one of the widely accepted joining method for cold rolled sheet due to final weld joint quality and efficiency. Quality of the weld is of paramount importance because failure of weld joint can cause breakdown for 1–3 days resulting in huge production loss. One such failure of weld joint of two sheets caused breakdown in CGL line for few hours. Failed samples were investigated to find out the cause of failure. Visual and stereo observations revealed presence of red coloured deposits at one corner of the sheets. Optical microscopy of sheet cross section confirmed the presence of red coloured deposits on the surface. It also revealed presence of scale at weld joint interface and grain coarsening at welding edge of the sheets without any fusion zone. Absence of fusion zone indicates poor welding. Fractography was done by using SEM to identify the mode of failure. Overall analysis suggests improper welding due to presence of scale (insulating material) which caused local temperature to rise and this possibly led to the improper welding and final failure.

The consequences of eliminating the soaking section of a commercial hot-dip galvanising line for HSLA production and a control strategy for improving product consistency

ABSTRACT This paper describes the results of the investigations done to adapt the thermal cycles applied to High Strength Low Alloy (HSLA) steels to the new furnace configuration of a galvanizing line. During the revamping of a hot dip galvanizing line, new radiant tubes were installed in the soaking furnace with the purpose of increasing the line capacity. This modification eliminated the soaking stage and forced to redesign the thermal cycles of the furnace. As the classical cycles proposed for the HSLAs worrisomely increased the percentage of rejections, it was defined a new control parameter based on the strip thickness, time in the furnace and strip temperature to guarantee the mechanical characteristics of these steels.

Plating Thickness Evaluation based on Eddy Current Testing for CGL

This paper explains a new technique based on the eddy current testing to evaluate plating thickness in the continuous galvanizing line. Previous techniques cannot apply to the line due to need low and/or fix liftoff. Because test samples are vibrated in the line by gas wipers. The new technique which we propose can evaluate the thickness with high and variable liftoff. Thus, the sensors based on the technique can install to near gas wipers which control the thickness and vibrate the samples in the line. First, the detection principle of the technique and the method of applying are explained on simulations by using the finite element method. Application results on measurement experiments are secondly explained. These results demonstrate the possibility of making thickness measurements using an eddy current with high and variable liftoff.

Effects of pre-annealing conditions on the microstructure and properties of vanadium-bearing dual-phase steels produced using continuous galvanizing line simulations

It is well known that the fracture behavior and weldability of steel often vary inversely with the carbon content. In the case of thin sheet intended for automotive applications, this means spot weldability and tensile ductility. However, the question arises, what is the reasonable maximum strength attainable in a low-carbon dual-phase (DP) steel under the constraints of: (1) with carbon levels at 0.1 wt%, (2) with the product (UTS × % TE) > 18,000 MPa, and (3) with processing on a simulated continuous hot-dipped galvanizing line. This study has focused on experimental compositions intended to meet DP steel grade properties in excess of 780 MPa UTS. This kind of advanced high-strength steel (AHSS) is an integral part of mass reduction programs for the body-in-white for the automotive industry. The family of steels investigated here is based on a low-carbon, aluminum-killed base steel containing Cr and Mo. In this study, the effects of the presence of V were studied. In addition, there were three processing variables investigated in terms of their respective effects on microstructure and mechanical properties: first, hot band coiling temperature; second, % cold reduction; and third, the thermal path through the CGL process. The thermal paths explored included both a standard galvanizing process and a new supercooling process; these were studied using a CGL simulation. This research revealed that all three variables can have a significant effect on the final microstructure and properties.

Thermo-chemical Fluid Flow Simulation in Hot-Dip Galvanizing: The Evaluation of Dross Build-Up Formation

This paper presents a new computational framework to investigate the driving force for the formation of intermetallic dross particles in the zinc bath and dross build-up on the bath hardware. This is a major problem in continuous hot-dip galvanizing lines. The Computational Fluid Dynamics (CFD) model calculates the turbulent thermo-chemical flow conditions within the liquid melt. A detailed modeling of the steel strip–liquid interface enhances this approach, by means of a conjugated heat transfer calculation and a spatially resolved, temperature- and concentration-dependent iron dissolution and aluminum uptake. The heart of the computational framework is a thermodynamic model, which assesses the driving force for the formation or dissolution of dross particles in the bath and dross build-up on stationary and rotating equipment. The simulation results are validated with temperature and species depth profile measurements. The applicability of the CFD model is shown by investigating the locally resolved aluminum uptake and iron dissolution at the steel-strip surface, and the multi-physics conditions in the region near the roll. The novel approach of evaluating the thermodynamic driving force enables the assessment of the formation of dross build-up at the roll surface.

Non-Collocated Position Control of Steel Strip With Electromagnetic Rejection of Unknown Multi-Harmonic Disturbances

Many industrial processes are affected by periodic disturbances. For instance, vibration of steel strips in hot-dip galvanizing lines entail an inhomogeneous zinc coating of the final product. Excitation by periodic disturbances is also frequently encountered in other control systems. Thus, a number of customized methods for rejection control of unwanted oscillations have been developed in the literature. In this paper, a method for eliminating a multi-harmonic periodic disturbance at an arbitrary user-defined position of a steel strip is proposed. The control task is particularly complicated because the disturbance input, a (single) displacement sensor, a (single) electromagnetic actuator, and the system output to be controlled are located at different positions along the strip. In addition, the electromagnetic actuator used as control input features neither a force sensor nor a distance sensor for measuring the air gap between the strip and the magnetic core. Hence, the actuator operates in a pure feedforward mode. The developed control method is validated by means of an experimental test rig that mimics a scenario from an industrial hot-dip galvanizing line.

Reduction of zinc and nickel ion loss by rinsing waters of galvanic lines with their utilization in the form of additional coating layers

Reduction of zinc and nickel ion loss by rinsing waters of galvanic lines with their utilization in the form of additional coating layers

Design and Development of Galvannealed Dual-Phase Steel: Microstructure, Mechanical Properties and Weldability

It was attempted to produce galvannealed dual-phase (DP) steel through a commercial continuous galvanizing line (CGL). The main challenge was to form the DP microstructure even with the slow cooling rate after annealing in the CGL. A two-pronged approach was adopted for this, viz. design of the steel chemistry with calculations and optimization of the CGL parameters with simulation using Gleeble-3800 thermomechanical simulator. The steel thus produced in CGL revealed ferrite and 18 ± 2% martensite microstructure, with tensile strength exceeding 600 MPa and 24% total elongation along with good formability. Weldability study using resistance spot welding indicated the possibility of achieving sound joint with a 4-kA width in weld time–current lobe despite the high carbon equivalence.

Flexible manufacturing technology of controlling exact bake hardening value in continuous galvanizing line

Flexible manufacturing technology for ultra-low-carbon bake hardening (BH) steels with different solute carbon contents in the range of (6–16) × 10−4 wt.% was systematically studied. The effects of soaking temperature, cooling rate and aging time on solute carbon content were explored. The bake hardening value in a continuous galvanizing line with an over-aging section was investigated. Optimal manufacturing parameters were calculated using the design of experiment to obtain the best and most flexible process parameters. Results indicate a relationship among carbon content, soaking temperature and cooling rate. When solute carbon is 9 × 10−6, cooling rate is 50 °C/s, the soaking temperature is 745 °C, and BH value is 45 MPa, the requirements of an automobile factory can be met.

Active rejection control for unknown harmonic disturbances of the transverse deflection of steel strips with control input, system output, sensor output, and disturbance input at different positions

In hot-dip galvanizing lines for steel strips, it is important to ensure a homogeneous zinc layer thickness. For this, vibrations of the strip at the gas wiping dies, where excess liquid zinc is blown off, must be suppressed. These vibrations typically exhibit a dominant sinusoidal shape and the excitation process, the frequency, the amplitude, and the phase are generally unknown.In modern plants, electromagnetic actuators are employed to enable a contactless vibration and shape control of the steel strip. Vibration control of flexible structures is well established in literature. However, in the considered application the disturbance (source of periodic excitation), the control input (force of electromagnetic actuators), the sensor output (strip displacement) and the desired system output (strip displacement at the gas wiping dies) are all located at different positions along the strip, which makes the overall control task quite challenging. In this paper, a control concept consisting of a linear quadratic regulator combined with a disturbance feedforward concept based on the theory of invariant manifolds and an Extended Kalman Filter is developed. The proposed control strategy is successfully tested on an experimental test rig for different scenarios.

A decision support flexible scheduling system for continuous galvanization lines using genetic algorithm

An important, complex problem for logistic optimization in the steel manufacturing plants is obtaining a flexible and adaptive scheduling system for a continuous galvanization line (CGL). The problem tackled in this work involves several constraints and characteristics inspired by real-life manufacturing goals. Given the complexity of the problem, which belongs to the class of NP-hard problems, a genetic algorithm (GA) methodology was developed, combining a penalty procedure defined for constraints with assigned weights for different characteristics of coils. By enlisting the ability and flexibility of GAs, a set of parameters are analyzed to achieve the best results for practical applications. This scheduling solution predicts a CGL sequences with a minimum number of coil transitions, to improve productivity and reduce costs.

A Modelling and a New Hybrid MILP/CP Decomposition Method for Parallel Continuous Galvanizing Line Scheduling Problem

A Modelling and a New Hybrid MILP/CP Decomposition Method for Parallel Continuous Galvanizing Line Scheduling Problem

Influence of Steel Strip Temperature in Formation Zinc Dross During Process Production Using Continuous Galvanizing Line (CGL) Machine

To control the occurrence of zinc dross during galvanizing process using production Continuous Galvanizing Line (CGL) machine, it is necessary to control steel strip temperature before entry into zinc bath. The Steel strip temperature controls were variable at 320°C and 400°C and zinc bath temperature was fix at temperature 460°C. At temperature steel strips of 320°C, zinc bath was checked using spectrometry, the results of Fe content 0.1293% and Al 0.0759%, because the solubility of Al is lower than Fe, the dross occurs become bottom dross. If the zinc dross change become bottom dross, the bottom dross could decrease quality of product and life time of zinc pot, because bottom dross settled at the floor. Bottom dross properties very hard and absorb heating, then at that position bottom dross make hot spot in the floor, finally zinc pot leakage. At temperature steel strip 400°C, the results content of Al 0.1667% and Fe 0.1217%, due to high temperature steel strip make solubility of Al become higher than Fe, therefore float at the zinc bath become top dross.

Analysis About the Failure Mechanism of the Sleeves in Sink Roll System

Sleeves and bushings were important expendables applied of sink roll system in hot-dip galvanizing lines, but the quick wear failure of the sleeves and bushings could significantly influence the stability the sink roll system and decreased the on-line life cycle substantially. To uncover the quick failure mechanism of the sleeves and bushings, the contact stress and friction coefficient between the sleeves and bushings were analyzed; the results indicated that under the action of high tensile stress in the steel strip, the contact stress between the sleeves and bushings could exceed 100 MPa; at the meantime, high contact stress induced high friction coefficient; in addition, the alloying between zinc and steel could decrease the surface hardness and hard zincilate particles could participated in the abrasion, the sleeves and bushings would come to quick wear failure under the combinations of the factors above.

Accurate Online Measurement of Iron Concentration in Galvannealed Coating Layers by Shift of X-ray Diffraction Peak

The authors have developed a new online measurement system for the Fe concentration in galvannealed (GA) coating layers based on the proportionality between the X-ray diffraction (XRD) peak angle of the δ1 phase and the Fe concentration. The online system was realized by high speed measurement of the XRD peak angle by a one-dimensional detector and use of a correction algorithm for the angular error caused by the displacement of the GA strip surface from the measurement position. The XRD profile and displacement were simultaneously measured by the one-dimensional detector and a laser displacement meter, respectively. The high accuracy of this new online system was demonstrated in a continuous galvanizing line with GA steel strips of Si-added and Si-free base steels. The developed system showed sufficiently high accuracy even with the Si-added base steel, with which adequate accuracy could not be obtained with conventional online systems, based on the diffracted intensity of the Γ phase, due to the suppression of Γ phase formation. Since the δ1 phase is the major phase of the GA layers, the main advantage of the developed system is that its accuracy is less sensitive to the composition of the base steel. The developed system can be applied to other online measurement applications in the steel industry for various purposes such as measurement of phase transition, orientation, crystallinity, strain and other features.

Numerical analysis of wiping jet flow in Continuous Galvanizing Line

Numerical analysis of wiping jet flow in Continuous Galvanizing Line