Galvanized Steel Sheets Research Articles

The effect of zirconia ions on corrosion performance of sol–gel coated galvanized steel

Currently, galvanized steel is treated with hexavalent chrome passivation. Sol–gel coating has been found to be a potential replacement for the hazardous hexavalent chrome passivation treatment. The aim of this work is to study the effect of zirconyl nitrate on corrosion behavior of sol–gel coating. Aminopropyl-trimethoxysilane and 3-glycidoxypropyltrimethoxysilane were employed as precursors to prepare the sol–gel-based silane coating. The sol–gel film was deposited on galvanized steel sheet by dip coating method. The chemical properties of sol–gel solution and coated films were analyzed by infrared spectroscopy. Morphology of the film was characterized by scanning electron microscope. The corrosion resistance of the coated samples was evaluated by electrochemical impedance spectroscopy, potentiodynamic polarization curve, and salt spray test. The results indicated that zirconia-doped coatings have better corrosion resistance in comparison with their undoped counterparts. The coating doped with 0.5% zirconyl nitrate provides better corrosion protection due to the inhibitive action of zirconia ion.

Surface lubrication influence on electrode degradation during resistance spot welding of hot dip galvanized steel sheets

The material uptake mechanism of a resistance spot welding electrode is presented for two selected surface conditions of hot-dip galvanized steel sheets, i.e., lubricated and non-lubricated. The evolution of material deposition varies according to the different surface states. Spot welding of lubricated sheet results in a more uniform and reduced alloyed material uptake that deposits on the welding electrode cap. Accordingly, the low deposition of material on the electrode surface enhances the weldability of hot-dip galvanized steel sheets. A reproducible current flow and a stable energy input is thus ensured along the electrode cap surface during resistance spot welding. Furthermore, lubrication leads to a considerably reduced sticking of welding electrodes.

Investigation of shinning Spot Defect on Hot-Dip Galvanized Steel Sheets

Shinning spot defects on galvanized steel sheets were studied by optical microscope, scanning electron microscope(SEM), Energy Dispersive Spectrometer (EDS) and Laser-Induced Breakdown Spectroscopy Original Position Statistic Distribution Analysis (LIBSOPA) in this study. The research shows that the coating thickness of shinning spot defects which caused by the substrate defect is much lower than normal area, and when skin passed, the shinning spot defect area can not touch with skin pass roll which result in the surface of shinning spot is flat while normal area is rough. The different coating morphologies have different effects on the reflection of light, which cause the shinning spot defects more brighter than normal area.

Effect of Coating Layer on Advanced Stud Welding of 2024 Aluminum Alloy to Galvanized and Galvannealed Steel Sheet

High strength 2024 aluminum alloy studs were joined to galvanized, galvannealed and non-coated steel sheets by using an advanced stud welding method. Effect of the coating layer on the interfacial microstructure and the tensile fracture load of the joints were evaluated. A specially-designed stud having a circular projection at its bottom was pressed against a sheet surface. A discharge current was introduced from the upper part of the stud. Local heating could be achieved by a high current density at a contact point between the projection and sheet. The observation of joint area revealed the projection was severely deformed and spread along the sheet surface. The coating layer of the galvanized steel sheet was removed at the joint interface under the charging voltage of 200 V, while that of the galvannealed one locally remained on the steel surface even at 400 V. This would be strongly related to the melting or liquidus and solidus temperatures of each coating layer. Joining was not achieved at a low charging voltage in the non-coated and galvannealed steel sheets, while high tensile fracture load was obtained even at 200 V in the galvanized ones.

Ultrasonic Spot Welding of Galvanized Steel Sheet

Ultrasonic spot welding of galvanized steel sheets has been conducted to investigate formation process of the weld microstructure, and effect of zinc coat on joint property. The joint strength showed a rapidly increase at the weld time of 0.8s, and it has the maximum value over 1.0 s. In the weld time range from 0.1s to 0.8s, fracture occurred in zinc coat/ steel interface. In contrast, the fracture partially occurred in the base steel in the weld time over 1.0s, and concaves in which the steel substrate of one specimen partially remains on the other specimen were observed. The formation process of weld microstructure of ultrasonic welding was proposed to be a two-steps process. First, zinc coat in the interface was mechanically removed by the vibration and clamping force, and some zinc particles dispersed in the weld interface. Second, the zinc particles melted due to the friction, and partially bonded regions were simultaneously formed around the zinc particles. The partially bonded regions were stirred with the steel substrate as the weld time increased. The joint strength increased by development of the stirred zone. At the weld time over 1.2s, the joint strength decreased due to growth of crack around the stirred zone.

Connection mechanism research on friction stir spot welding without keyhole between magnesium and steel dissimilar alloys

A 3 mm thick AZ31B magnesium sheet is lapped by friction stir spot welding (FSSW) to a 1 mm thick DP600 galvanised steel sheet. This is carried out without any keyhole under an optimal welding condition. A good joint of 8·7 kN strength is measured. The microstructure of welding joint is analysed by optical microscope and scanning electron microscopy, showing that steel is stirred into magnesium. The phenomenon is similar to a ‘nail’ embedded in the magnesium, with steel and magnesium completely mixed. Beside the metal compound formed between Fe and Al element, X-ray diffraction identifies intermetallic compounds formed between Mg and Al, Mg and Zn elements. Therefore, it is concluded that magnesium steel by FSSW without keyhole is governed by a mechanical connection, followed by metallurgical combine.

Influence of Surface Roughness of Galvanized Steel Sheet on Self-lubricated Coating

Three different thicknesses of self-lubricated coatings were prepared on galvanized steel sheets with different surface roughness (Ra). Performances of the coatings were evaluated by various laboratory tests. Scanning electron microscopy (SEM), atomic force microscope (AFM), neutral salt spraying test (NSST), reciprocating friction and wear test were taken in order to characterize the coatings. Results show that the self-lubricated coating has good corrosion resistance and lubricating property. In 0.857—1.629 μm of Ra value, the relationship between friction coefficients of the self-lubricated steel sheets and the surface roughness of the galvanized steel sheets likes a parabolic curve, and has a peak value of friction coefficient in certain range of Ra. Affected by the hereditary surface topography of the galvanized steel sheet, dents on the surface of self-lubricated steel become deeper and larger with the increase of the surface roughness of the galvanized steel sheets. The influence of the surface roughness of the galvanized steel sheet on the corrosion resistance of the self-lubricated coating steel is similar to that on friction coefficient of self-lubricated coatings, like a parabolic curve.

Physical properties of Brachystegia eurycoma seeds as affected by moisture content.

Some physical, frictional and thermal properties of Brachystegia eurycoma seed were studied at different moisture contents in order to explore the possibility of mechanizing the handling and processing techniques. Results showed that the seed could be considered an oval disc in shape. In the moisture range of 2.79% to 27.13% (d.b.), the major, intermediate and minor axial dimensions increased with increase in moisture content from 2.29 mm to 2.45 mm, 1.65 mm to 1.91 mm and 0.34 mm to 0.52 mm, respectively. In the above moisture range, one thousand seed weight, particle density, porosity, roundness, sphericity, surface area and angle of repose increased linearly from 0.901 kg to 1.252 kg, 2270 kg/m3 to 2520 kg/m3, 11.23% to 15.46%, 35% to 47%, 67% to 82%, 7.67 cm2 to 8.48 cm2 and 16.8° to 29.2° respectively, while bulk density decreased from 745.4 kg/m3 to 613.6 kg/m3. Static coefficient of friction on different structural surfaces increased linearly with moisture content and had the highest values on galvanized steel sheet (0.445-0.639), and the lowest values on fiber glass (0.287-0.404). Kinetic coefficient of friction increased linearly with moisture content on different structural surfaces except on galvanized steel sheet where it decreased linearly with increase in moisture content in the above moisture range. It had the highest values on hessian bag material (0.266-0.389), and the lowest values on plywood with wood grains perpendicular to the direction of movement (0.204-0.271). Specific heat ranged from 1474 to 5992.7 J/kgK, and increased with increase in moisture content and temperature. Regression equations were used to express the relationships existing between the seed properties and moisture content.

Some physical properties of ginkgo nuts and kernels

Abstract Some data of the physical properties of ginkgo nuts at a moisture content of 45.53% (±2.07) (wet basis) and of their kernels at 60.13% (± 2.00) (wet basis) are presented in this paper. It consists of the estimation of the mean length, width, thickness, the geometric mean diameter, sphericity, aspect ratio, unit mass, surface area, volume, true density, bulk density, and porosity measures. The coefficient of static friction for nuts and kernels was determined by using plywood, glass, rubber, and galvanized steel sheet. The data are essential in the field of food engineering especially dealing with design and development of machines, and equipment for processing and handling agriculture products.

Metallurgical characterisation of wrinkle bands and their influence on properties of galvanised steel sheet

In addition to several well known defects in hot dip galvanised products, there are other defects that, although less frequent, damage the quality of the coated steel sheet. One of these, wrinkle bands, were microstructurally characterised, and their influence on corrosion behaviour of coated sheet was evaluated. Surface characteristics and microstructural features were examined by scanning electron microscopy, microanalysis and glow discharge optical spectroscopy. The results indicated that the major cause of wrinkle bands is related to craters that originated from cold rolling that act as a pool for molten zinc during galvanising. Corrosion resistance was examined via a salt spray test, and the time to red rust formation was up to 72 h shorter on wrinkle bands as compared to other regions.

The Effect of Composition and Microstructure on Corrosion Behavior in SST of Zn-Al-Mg Galvanized Steel Sheet

Z11A3M, Z6A3M, Z1.6A1.6M, Z1A1M and Z1M coating samples were prepared in HDPS by traditional continuous hot dipping method. The microstructure, element distribution and phase was analyzed by SEM, EPMA and XRD. The corrosion resistance was checked in SST. The result was, MgZn2 and eutectic could be found in all ZAM coating. The ZAM coatings showed excellent corrosion resistance in SST than GI. The corrosion resistance was 4.1 to 11 times of GI. There was no strong relativity between alloy composition and corrosion resistance due to Mg enrichment on the surface of coating. Edge-unsealed ZAM samples showed good corrosion resistance than edge-sealed sample.

The Structure and Corrosion Process Characterization of Galvannealed and Galvanized Steel Sheets

The dissolution process of galvannealed (GA) and galvanized (GI) coating was examined by correlating a chemical stripping test in 1MNaCl+0.01MH2SO4solution. The key time of dissolution process of coating was found via measuring the variation of free corrosion potential. Through coating metallographic observations at the key point, the dissolution process of coating can be clear. There are four Fe-Zn intermetallic phases in GA coating, namely gamma-1,gamma,delta and zeta phases, from the substrate. The compressed part of GA and GI coatings was the initial of corrosion process. The net crack will be emerging on the delta phase, which width graduallyincreasing until stripping. Pitting corrosion occurred on the GI coating in the solution containing Cl-ion, the area and depth of pit gradually increasing until stripping. The corrosion potential of Fe2Al5Znxinhibition layer is about-0.8VSCE.

Cause and Remedies of Bulge Particle Defect on Surface of Hot-Dip Galvanized Steel Sheets

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.

Eco Deck Plate의 구조적 거동 평가를 위한 실험적 연구

에코 데크 플레이트 시스템은 철선일체형 거더와 아연도금 강판을 볼트에 의해 일체화시키기 때문에 기존에 용접에 의해 제작된 철선일체형 데크 플레이트에 비해 친환경 및 우수한 공법으로 인정받고 있다. 본 연구에서는 에코 데크 플레이트의 구조적 거동을 평가하기 위해 12가지 형태의 시험체를 동일한 조건으로 2개씩 총 24개의 시험체를 실물크기로 제작하여 실험적 연구를 수행한다. 실험결과 시공하중 작용에 대한 허용 처짐은 설계값 이내의 값을 나타내 만족하는 것으로 나타났으며, 래티스 철선의 가공은 아래로 향하게 절단해 제작하는 것이 구조적으로 유리한 것으로 나타났다. 또한, 하부철선으로 D13을 사용한 시험체의 경우에는 하부철선과 래티스 철선의 용접부위에서 파괴가 발생해 공장 제작 시 용접에 대한 개선안의 마련이 필요하다. Eco deck plate system is a construction method that deconstruction of galvanized steel sheets is possible by integrating steel-wire-integrated girders and the galvanized steel sheets with bolts. Therefore, compared with previous steel-wire-integrated deck plates which were joined by welding, the system is acknowledged as the construction method possible management and repair. This study conducted an experimental research by manufacturing total 24 full size specimens in a same condition for 12-shape specimens by two parts to evaluate structural behaviors of the eco deck plates. In the results after the test, permissible deflection for the construction load action was shown to be values under design values and satisfactory. The processing of lattice steel wires was presented to be structurally advantageous in being manufactured by cutting downward. Also, in case of a specimen that D13 as a steel wire was used, destruction occurred at the welding part of the bottom steel wire and the lattice steel wire, so improvement measures for the welding in factory manufacture are necessary.

Optimization of the Resistance Spot Welding Process of Galvanized Steel Sheet Using the Taguchi Method

Resistance spot welding is a process used in the industry for joining of sheets, especially in the automobile and aerospace industries. The complicated behavior of this process must be analyzed to set the optimum parameters to get good quality weld. This paper presents a systematic approach to determine the effects of six welding process parameters i.e. preheating current, squeeze time, welding current, weld time, hold time and electrode pressure on the nugget diameter and tensile shear (T-S) strength of the weld joint of galvanized steel. Taguchi quality design concepts of L18 orthogonal array has been used to determine signal-to-noise (S/N) ratio (dB), analysis of variance and F test value for indicating the most significant parameters affecting the spot welding performance. The plots of S/N ratio are used to find out the levels of factors affecting the process. The results obtained prove that improvement in the quality (8.61 % in the S/N ratio for nugget diameter and 19.50 % in S/N ratio for T-S strength) take place if parameters are set at the optimum level predicted by the Taguchi technique.

Effect of Spot Welding Current and Cycles on the Mechanical Properties of Welded Galvanized Steel Sheets

Studies on the effects of welding current and cycles were carried on the galvanized steel sheets using spot welding. The welding currents used were 3 kA, 5 kA 6 kA and the welding cycles were 4, 6 and 8. Tensile shear and tensile peel load were determined on the joint of welded specimens. The results showed that the value of tensile shear load was lower than tensile peel load. The strength of the joint increased with the increasing of welding current and welding cycle used in the welding process.

Possibilities of joining galvanized sheet steel using the CMT method (cold metal transfer)

A new method of joining galvanized sheet steel is the cold metal transfer (CMT) process developed by Fronius1-4. This method involves the use of a short-circuit arc, and its characteristics, which ...

Einfluss des pH Wertes auf die Korrosion von Zn-Al-Mg feuerverzinkten Stahlbändern in Chlorid enthaltenden Umgebungen

Previous studies of our group showed that Zn-Al-Mg hot-dip galvanized steel sheets have a superior corrosion resistance compared to conventional hot-dip galvanized steel sheets.

Optimization of parameters for depth resolution of galvanized steel by LIBS technique

In this study laser induced breakdown spectroscopy (LIBS) is applied for depth profile analysis of galvanized steel sheet widely used in automobile industry. The effects of laser processing parameters, such as laser energy, laser spot size, and coating thickness were investigated to find out depth resolution by applying Taguchi optimization method. According to confirmation experiments of using optimum parameters, it is found out that experimental results are compatible with Taguchi Method with a 83% rate. Numerical simulation of the heat transfer equation is also performed for single laser pulse irradiation since the physical phenomena involved in the laser induced process can be more accurately studied by investigating the effect of single pulse irradiation on the target surface.

Effectiveness of Stamping Lubricants in Erichsen Test

In the present work, formability of ultra low carbon steel sheets (uncoated interstitial free and galvanized steel sheet) has been characterized and the effectiveness of dry and liquid lubricants on formability of these steel sheets was evaluated by using the standard Erichsen test. Primarily, some important mechanical properties of materials like strain hardening coefficient (n), normal anisotropy (r) were determined using the tensile test and formability of these steel sheets has been correlated with these mechanical properties. Then these steel sheets were subjected to the Erichsen test using four different lubricants. Teflon, PVC, Polyethylene films and mineral oil were used in the experiments. Finite element simulations were done using various friction coefficients. Erichsen tests were conducted at 1 kN blank holder force and 2.4 mm/min punch velocity. Values of the Erichsen index and punch force-displacement curves were determined for each lubricant. PVC film proved to be the most effective lubricant for both materials.