A C–Mn dual-phase steel was soaked at 800°C for 90 s and then either rapidly cooled to 450°C and held for 30 s(process A) or rapidly cooled to 350°C and then reheated to 450°C(process B) to simula...A C–Mn dual-phase steel was soaked at 800°C for 90 s and then either rapidly cooled to 450°C and held for 30 s(process A) or rapidly cooled to 350°C and then reheated to 450°C(process B) to simulate the hot-dip galvanizing process. The influence of the hot-dip galvanizing process on the microstructure and mechanical properties of 600-MPa hot-dip galvanized dual-phase steel(DP600) was investigated using optical microscopy, scanning electron microscopy(SEM), transmission electron microscopy(TEM), and tensile tests. The results showed that, in the case of process A, the microstructure of DP600 was composed of ferrite, martensite, and a small amount of bainite. The granular bainite was formed in the hot-dip galvanizing stage, and martensite islands were formed in the final cooling stage after hot-dip galvanizing. By contrast, in the case of process B, the microstructure of the DP600 was composed of ferrite, martensite, bainite, and cementite. In addition, compared with the yield strength(YS) of the DP600 annealed by process A, that for the DP600 annealed by process B increased by approximately 50 MPa because of the tempering of the martensite formed during rapid cooling. The work-hardening coefficient(n value) of the DP600 steel annealed by process B clearly decreased because the increase of the YS affected the computation result for the n value. However, the ultimate tensile strength(UTS) and elongation(A80) of the DP600 annealed by process B exhibited less variation compared with those of the DP600 annealed by process A. Therefore, DP600 with excellent comprehensive mechanical properties(YS = 362 MPa, UTS = 638 MPa, A_(80) = 24.3%, n = 0.17) was obtained via process A.展开更多
Baosteel has excelled in automotive steel sheets in the past three decades.It has made a significant contribution to the development of China’s automotive industry by producing a wide range of high-quality steel prod...Baosteel has excelled in automotive steel sheets in the past three decades.It has made a significant contribution to the development of China’s automotive industry by producing a wide range of high-quality steel products.Some milestones achieved by Baosteel automotive steel sheet were briefly reviewed.The current challenges in producing ultra-high strength steel(UHSS),especially hot-dip galvanized UHSS,were summarized.The most current advancements in UHSS and the corresponding hot-dip galvanizing processes were discussed.The galvanizability of Si-Mn-added QP steel and DP steel, Mn-added TWIP steel, and Al-added low-density steel has been improved by different techniques in Baosteel.展开更多
In hot-dip galvanizing process, air jet wiping control is so crucial to decide the coating thickness and uni- formity of the zinc layer on the steel strip. The mathematical models developed predict the zinc coating th...In hot-dip galvanizing process, air jet wiping control is so crucial to decide the coating thickness and uni- formity of the zinc layer on the steel strip. The mathematical models developed predict the zinc coating thickness as a function of pressure and shear stress. The required pressure and shear stress profile on the strip surface were calcu- lated using regression analysis, and carried out using numerical simulation as FLUENT, a finite element analysis software. The influences of the outlet pressure, the nozzle to strip distance, the slot opening, the edge baffle plate, as well as the tilting angle of air knife were discussed. Combining with these results and regression analysis on the practical data, four first-order polynomial multi-parameter models were established for different targeted coating thicknesses with better regression coefficients. The validated model was used to carry out sensitivity analysis to de- termine the favorable controlling regime for the air jet wiping process.展开更多
The causes of tiny spot defects on the surface of hot-dip galvanized automotive steel sheets were studied using scanning electron microscopy(SEM)and energy dispersive spectrometer(EDS),and effective control measures w...The causes of tiny spot defects on the surface of hot-dip galvanized automotive steel sheets were studied using scanning electron microscopy(SEM)and energy dispersive spectrometer(EDS),and effective control measures were introduced.The results show that rubbing against the top roller after galvanizing is easy due to the local thickness of tiny spot defect location coating;therefore,the surface morphology is different from the normal part.Three kinds of defects,namely zinc slag,small slivers,and pitting,are likely to cause local thickening of the coating after galvanizing,leading to the formation of tiny spots.Therefore,resolving the three types of defects can effectively control the generation of tiny spot defects.Among them,due to the hereditary nature of the small sliver defect,focusing on its control and supervision is necessary.展开更多
A new processing method for producing hot dip galvanized steel is designed and tested, in which pickling is skipped. Hot-rolled low carbon steel sheets are roiled with oxide scale in an experimental mill at room tempe...A new processing method for producing hot dip galvanized steel is designed and tested, in which pickling is skipped. Hot-rolled low carbon steel sheets are roiled with oxide scale in an experimental mill at room temperature, prior to annealing under a 20% hydrogen reducing atmosphere and galvanizing on a hot-dip galvanizing simulator. Micro-cracks formed in the oxide scale during cold rolling roughen the steel surface and enlarge the specific surface. Through-thickness cracks provide transport channels for hydrogen, and hence the reduction of oxide scale is en- hanced. When the sheet is dipped in the zinc bath, cracks are submerged by liquated zinc and the defects are not dis- tinct after hot-dip galvanizing. The overlay coating occludes with rough surface of the sheet, whereby a superior coat- ing adherence is realized.展开更多
With the rapid development of the automobile industry, the use of galvannealed and galvanized steel sheets in automobiles is on the rise. These sheets must meet very high surface quality requirements. The surface trea...With the rapid development of the automobile industry, the use of galvannealed and galvanized steel sheets in automobiles is on the rise. These sheets must meet very high surface quality requirements. The surface treatment of line rolls is known to have a great impact on strip quality. To prevent dusts such as zinc ash from pressing into the strip surface, we used a composite thermal spray surface treatment technique to treat rolls. The successfully developed tungsten carbide （WC） ＋ Ni-P composite plating technology improved the quality of the tungsten carbide thermally sprayed WC roll surface. This technique is also helpful to control defects such as adhered foreign materials in hot-dip galvanized automobile outer panel surfaces.展开更多
In recent years, the waterborne free intermediate coating process has been widely used in the automotive industry. Because the baking times and coating thickness are decreased, the surface covering capability of the p...In recent years, the waterborne free intermediate coating process has been widely used in the automotive industry. Because the baking times and coating thickness are decreased, the surface covering capability of the painting process is reduced, which directly affects the appearance quality（ long-and short-wave values） of the body paint. Thus, there are correspondingly higher requirements for the white body surface profile prior to painting. The surface profile of the white body is mainly affected by the plate material, the surface profile, and the deformation process. So,the change rule for the surface profile during deformation of the steel plate is a key factor in coating appearance optimization. In this paper, we first analyze the typical deformation of the outer cover of a car body. Then ,we examine the change tendency of the surface profile of steel plates with respect to different deformation rates, specifically for a steel plate comprising a hot-dip galvanized bake-hardened steel sheet. Based on our analysis of the influence of the deformation on the coating appearance,we selected 3% ,5% ,and 8% deformation rates in this research. We found the roughness （Ra） value in the typical deformation range （3% -8% ） of the car body to exhibit a decreasing trend at first and then an increasing trend. The Ra value of the 8% deformation is not more than the original plate test value. When the Pc value of the original plate is in the lower range （ about 60）, it exhibits a slight increasing trend in the deformation process （3 % -8 % ）. And when the Pc value of the original plate is in the higher range （ about 120 ）, it exhibits no increasing trend in the deformation process （ 3% -8% ）. In contrast,the waviness （WCA） value in the car body＇s typical deformation range （3%-8%） shows a significant growth trend.展开更多
An iron and steel company＇ s hot galvanizing technology was chosen as the object. An orthogonal experimental scheme with 5 factors of mixed level was designed, according to the various factors affecting the distribut...An iron and steel company＇ s hot galvanizing technology was chosen as the object. An orthogonal experimental scheme with 5 factors of mixed level was designed, according to the various factors affecting the distribution of slag. For each scheme, the amount of slag and slag height in different orthogonal schemes by simulation were obtained with FLUENT software. Then, range and variance analyses were selected to compare the trend of slag height in the different process parameters of the hot dip galvanizing process. Finally, the optimal combination of the process parameters was obtained.展开更多
The microstructure of hot-dip galvanized Zn-ll%A1-3%Mg-0.270Si alloy coating was studied in this article. X-ray diffraction analysis revealed the coating is composed by Zn, A1 and MgZn2 phase. Optical microscope （OM...The microstructure of hot-dip galvanized Zn-ll%A1-3%Mg-0.270Si alloy coating was studied in this article. X-ray diffraction analysis revealed the coating is composed by Zn, A1 and MgZn2 phase. Optical microscope （OM） and scanning electron microscope （SEM） observations showed the coating is occupied by snowflake-like dendrite, double hexagonal organization and eutectic. The coating backbone was the dendrite considered to be a phase of hexagonal close-packed （HCP） structure judging form its morphology according to the crystal growth way in the coating. Transmission electron microscopy （TEM） and energy dispersive spectroscopy （EDS） researches on the dendrite suggested that an intermediate Zn-A1 phase was formed at high temperature, then decomposed into a type of Zn-A1 granular eutectoid after cooling down to room temperature, while the eutectoid Zn and A1 had a certain crystallographic relationship. The coating solidification process and the grain crystal structure were discussed.展开更多
Scanning electron microscopy,X-ray diffraction,a neutral salt spray test,and electrochemical methods were applied to observe the microstructure and test the corrosion resistance of hot-dip galvanized steel before and ...Scanning electron microscopy,X-ray diffraction,a neutral salt spray test,and electrochemical methods were applied to observe the microstructure and test the corrosion resistance of hot-dip galvanized steel before and after the addition of La and Ce.La/Ce mixture existed in the form of(La,Ce)Zn13 on the coated surface,decreased the coating thickness and accelerated the zinc dendritic growth.The corrosion current density of Zn-0.1La-0.1Ce coating was 63%less than that of pure Zn coating.This phenomenon can be explained that La/Ce mixture inhibited the transformation of Zn5(OH)8Cl2·H2O into Zn5(CO3)2(OH)6 or ZnO,reduced the time for appearance of red rust,and thus enhanced the stability of corrosion products and delayed the oxidation and corrosion processes of galvanized coating.La/Ce mixture improved the corrosion resistance compared to a single La or a single Ce addition.A competitive relationship between La and Ce was observed in the corrosion resistance improvement of hot-dip galvanized steel.展开更多
Wettability of Zn-Al alloy melt on the pure iron substrate at 450℃was studied.The effect of Al content(Zn,Zn-1Al,Zn-2Al,Zn-3Al,Zn-4Al,and Zn-5Al)on the wetting behavior and interfacial reaction was investigated by hi...Wettability of Zn-Al alloy melt on the pure iron substrate at 450℃was studied.The effect of Al content(Zn,Zn-1Al,Zn-2Al,Zn-3Al,Zn-4Al,and Zn-5Al)on the wetting behavior and interfacial reaction was investigated by high-temperature contact angle measuring device and scanning electron microscope(SEM).The results show that,with the increase of Al content,the initial contact angle of the molten alloy on the substrate decreases gradually and the wettability increases gradually.Compared with the initial contact angle,the final contact angle is slightly reduced,because the Fe-Al inhibition layer is preferentially formed at the interface when adding Al to the alloy.The presence of Al will promote the occurrence of the reactive wetting,leading to an insignificant wetting spreading process,and the final contact angle negligibly differs from the initial contact angle.The adhesion work and charge density distributions of interface systems were calculated based on the first-principles.The results show that the adhesion work of the Fe/Zn and Fe/(Zn-Al)interface model is 2.0171 J/m^(2)and 13.7944 J/m^(2),respectively.The addition of Al greatly increases the adhesion work between alloy melt and iron substrate.Compared with the Zn-Fe and Al-Fe interface models,it can be seen that a significant charge migration phenomenon occurs between the interfaces.The amount of charge migration in the Al-Fe interface model is much larger than that in the Zn-Fe interface model,indicating that the bonding between Al-Fe atoms can occur more easily and the interaction between Al-Fe interfaces is stronger.This is also the reason why the addition of Al increases the adhesion work between interfaces.展开更多
Hot-dip galvanized sheet is wildly used in construction,household appliances,ship,vehicle and vessel building and machinery,etc.In last ten years,with the development of automobile industry,the anti-eorrosion requirem...Hot-dip galvanized sheet is wildly used in construction,household appliances,ship,vehicle and vessel building and machinery,etc.In last ten years,with the development of automobile industry,the anti-eorrosion requirements for car body are increasingly strict,by which the rapid development in technology has been promoted.The application of hot-dip galvanized sheet,technological progress in production and some Chinese large units were introduced.展开更多
In this study,the factors affecting the formation of small black spot defects on the surface of a hot-dip galvanized pure zinc strip are analyzed. These defects are primarily formed w hen the iron-aluminum inhibition ...In this study,the factors affecting the formation of small black spot defects on the surface of a hot-dip galvanized pure zinc strip are analyzed. These defects are primarily formed w hen the iron-aluminum inhibition layer is incompletely formed or fails to form or when foreign matter adheres to the surface or embeds in the zinc layer.The defects can be reduced by controlling the cleanliness and activity of the strip base before coating,regulating the zinc pot process parameters,and ensuring the cleanliness of the passline and workshop.展开更多
Bottom dross obtained from zinc bath and the typical bottom dross defects on galvanized and galvannealed coating were metallographically investigated.Galvannealing simulations with different holding time were conducte...Bottom dross obtained from zinc bath and the typical bottom dross defects on galvanized and galvannealed coating were metallographically investigated.Galvannealing simulations with different holding time were conducted,and the bottom dross transformation behavior during the galvannealing process was revealed.The fast diffusion between bottom dross particles and the surrounding zinc occurs during the galvannealing process,resulting in the formation of an Al-containing Zn-Fe intermetallic outburst structure at the defect position.The thicker and harder coating will cause a shiny spot on the coating surface and a deep dent on the substrate after being temper rolled.展开更多
At first, a series of finite element method （FEM） simulation tests were used to find the critical forming conditions of hot-galvanized sheet steel during the rectangular box drawing processing when constant blank ho...At first, a series of finite element method （FEM） simulation tests were used to find the critical forming conditions of hot-galvanized sheet steel during the rectangular box drawing processing when constant blank holder forces were applied. According the test results, the reasonable alteration scope of initial variable blank holder force （VBHF） was as 1.9-2.3 T. Then, based on the test productions of blank holder force, 12 typical VBHF curves were applied to perform the simulation tests by the simulation software of DYNAFORM. The simulation test results showed that VBHF had great effects on drawing formability of hot-galvanized sheet steel during the rectangular box drawing. However, the different VBHF curves were applied to control the whole drawing and it would get great different effects. At the same tine, the VBHF had great effects on the maximum thick thinning ratio, but had little effect on the maximum thick incrassation ratio. So, reasonable application of the VBHF would greatly decrease the fractures. When the VBHF profile is taken as curve L, the best effect of drawing formability could be obtained. When curve I is used, contrary effect could be gotten. The other types of curves would cause effects between above two types of VBHF curves. Finally, the actual tests were applied to check the validity of the FEM simulation tests. The results show that the FEM simulation tests are good ways for predicting and optimizing the VBHF.展开更多
China has become the maximum household appliances manufacturing base worldwide.It is a new challenge facing the steel industry to develop the low-cost and environment-friendly sheet for household appliance industry,so...China has become the maximum household appliances manufacturing base worldwide.It is a new challenge facing the steel industry to develop the low-cost and environment-friendly sheet for household appliance industry,so Cr-free anti-fingerprint hot-dip galvanized sheet for household appliances is the upgraded product which satisfies the requirement of China household appliance industry' s nuisanceless treatment.The paper discusses the technical key points of development on Cr-free anti-fingerprint galvanized sheet for household appliances,including the development of the Cr-free anti-fingerprint chemical and the production technology of Cr-free anti-fingerprint galvanized sheet for household appliances.The paper elaborates the main compositions,physical features and properties of the Cr-free anti-fingerprint chemical, surface quality control technology,anti-fingerprint coating quality control technology,influence of anti-fingerprint film weight on corrosion resistance,conductibility,high-temperature discolouration resistance,acid resistance,alkaline resistance and solvent resistance of Cr-free anti-fingerprint hot-dip galvanized sheet, influence of anti-fingerprint coating uniformity on paintability of the sheet,influence of strip surface roughness on corrosion resistance and conductivity of the sheet and influence of strip surface quality on corrosion resistance of the sheet.Adopting the suitable Cr-free anti-fingerprint chemical and the reasonable production process parameters,the properties of the Cr-free anti-fingerprint hot-dip galvanized sheet conform to the delivery technical norms and the Cr-free anti-fingerprint hot-dip galvanized sheet becomes the new material for household appliances such as computer case.展开更多
The main objective of this work was to evaluate the presence of lead and cadmium in galvanized steel tubes by hot-dip used exclusively for drinking water supply.In this research,samples of galvanized tubes were remove...The main objective of this work was to evaluate the presence of lead and cadmium in galvanized steel tubes by hot-dip used exclusively for drinking water supply.In this research,samples of galvanized tubes were removed from walls of residential buildings with 30 years of use.In the process of hot galvanizing,the manufacturing standards allow or for low cost conveniences,and the use of primary zinc ingot with 1.6%metallic impurities,such as lead and cadmium,is allowed,enabling the incorporation of these metals into the zinc coating deposited on the carbon steel.The associated corrosion of these tubes can release these toxic metals,contaminating the drinking water used by residents.The samples taken from the tubes were evaluated by a square-wave anodic stripping voltammetry technique,and the results for lead and cadmium suggested randomly distributed levels,indicating that the contents of these contaminants depend mainly on the quality of the added primary zinc and the operational conditions of the immersion bath.The metallographic evaluations performed on the samples of the galvanized tubes showed irregularities in thickness and even a lack of the zinc layer deposited on the carbon steel surface.These facts suggest that galvanized tubes should not be used for drinking water.展开更多
Taking the intelligent improvement of hot-dip galvanizing production line as the object, the whole production line is upgraded through the accumulation and comparison of empirical data, so as to improve the intelligen...Taking the intelligent improvement of hot-dip galvanizing production line as the object, the whole production line is upgraded through the accumulation and comparison of empirical data, so as to improve the intelligent, standardized and functional design of hot-dip galvanizing production line, improve the ability of hot-dip galvanizing enterprises in production cost, product quality and delivery date, and enhance the competitiveness of their products in the market, so as to obtain the ability of sustainable development.展开更多
The chemical composition of the zinc bath can strongly influence on the hot-dip galvanized coatings. In this work, the effects of tin addition on the surface morphology, and the corrosion resistance of hot-dip galvani...The chemical composition of the zinc bath can strongly influence on the hot-dip galvanized coatings. In this work, the effects of tin addition on the surface morphology, and the corrosion resistance of hot-dip galvanized steel were investigated. The corrosion behavior of steel samples galvanized with zinc and Zn-Sn alloys containing different wt% Sn was analyzed by various corrosion tests such as potentiodynamic polarization Tafel lines and electrochemical impedance spectroscopy (EIS) techniques. Salt spray test was employed in order to study the corrosion products of the specimens. Surface morphology, the composition of coating layers and nature of the corrosion products were also investigated using field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray analysis (EDX) and X-Ray diffraction (XRD) techniques, respectively. The results indicated that the addition of small amounts of Sn (0.1 wt%) to the molten zinc galvanizing bath can improve the corrosion resistance of hot-dip galvanized steel.展开更多
基金financially supported by the National Natural Science Foundation of China (Nos.U1360202,51472030,and 51502014)
文摘A C–Mn dual-phase steel was soaked at 800°C for 90 s and then either rapidly cooled to 450°C and held for 30 s(process A) or rapidly cooled to 350°C and then reheated to 450°C(process B) to simulate the hot-dip galvanizing process. The influence of the hot-dip galvanizing process on the microstructure and mechanical properties of 600-MPa hot-dip galvanized dual-phase steel(DP600) was investigated using optical microscopy, scanning electron microscopy(SEM), transmission electron microscopy(TEM), and tensile tests. The results showed that, in the case of process A, the microstructure of DP600 was composed of ferrite, martensite, and a small amount of bainite. The granular bainite was formed in the hot-dip galvanizing stage, and martensite islands were formed in the final cooling stage after hot-dip galvanizing. By contrast, in the case of process B, the microstructure of the DP600 was composed of ferrite, martensite, bainite, and cementite. In addition, compared with the yield strength(YS) of the DP600 annealed by process A, that for the DP600 annealed by process B increased by approximately 50 MPa because of the tempering of the martensite formed during rapid cooling. The work-hardening coefficient(n value) of the DP600 steel annealed by process B clearly decreased because the increase of the YS affected the computation result for the n value. However, the ultimate tensile strength(UTS) and elongation(A80) of the DP600 annealed by process B exhibited less variation compared with those of the DP600 annealed by process A. Therefore, DP600 with excellent comprehensive mechanical properties(YS = 362 MPa, UTS = 638 MPa, A_(80) = 24.3%, n = 0.17) was obtained via process A.
文摘Baosteel has excelled in automotive steel sheets in the past three decades.It has made a significant contribution to the development of China’s automotive industry by producing a wide range of high-quality steel products.Some milestones achieved by Baosteel automotive steel sheet were briefly reviewed.The current challenges in producing ultra-high strength steel(UHSS),especially hot-dip galvanized UHSS,were summarized.The most current advancements in UHSS and the corresponding hot-dip galvanizing processes were discussed.The galvanizability of Si-Mn-added QP steel and DP steel, Mn-added TWIP steel, and Al-added low-density steel has been improved by different techniques in Baosteel.
基金Sponsored by National Natural Science Foundation of China (50604006)National Development and Reform Commission of China (2009-354)
文摘In hot-dip galvanizing process, air jet wiping control is so crucial to decide the coating thickness and uni- formity of the zinc layer on the steel strip. The mathematical models developed predict the zinc coating thickness as a function of pressure and shear stress. The required pressure and shear stress profile on the strip surface were calcu- lated using regression analysis, and carried out using numerical simulation as FLUENT, a finite element analysis software. The influences of the outlet pressure, the nozzle to strip distance, the slot opening, the edge baffle plate, as well as the tilting angle of air knife were discussed. Combining with these results and regression analysis on the practical data, four first-order polynomial multi-parameter models were established for different targeted coating thicknesses with better regression coefficients. The validated model was used to carry out sensitivity analysis to de- termine the favorable controlling regime for the air jet wiping process.
文摘The causes of tiny spot defects on the surface of hot-dip galvanized automotive steel sheets were studied using scanning electron microscopy(SEM)and energy dispersive spectrometer(EDS),and effective control measures were introduced.The results show that rubbing against the top roller after galvanizing is easy due to the local thickness of tiny spot defect location coating;therefore,the surface morphology is different from the normal part.Three kinds of defects,namely zinc slag,small slivers,and pitting,are likely to cause local thickening of the coating after galvanizing,leading to the formation of tiny spots.Therefore,resolving the three types of defects can effectively control the generation of tiny spot defects.Among them,due to the hereditary nature of the small sliver defect,focusing on its control and supervision is necessary.
基金Item Sponsored by National Science and Technology Pillar Program of China(2011BAE13B04)
文摘A new processing method for producing hot dip galvanized steel is designed and tested, in which pickling is skipped. Hot-rolled low carbon steel sheets are roiled with oxide scale in an experimental mill at room temperature, prior to annealing under a 20% hydrogen reducing atmosphere and galvanizing on a hot-dip galvanizing simulator. Micro-cracks formed in the oxide scale during cold rolling roughen the steel surface and enlarge the specific surface. Through-thickness cracks provide transport channels for hydrogen, and hence the reduction of oxide scale is en- hanced. When the sheet is dipped in the zinc bath, cracks are submerged by liquated zinc and the defects are not dis- tinct after hot-dip galvanizing. The overlay coating occludes with rough surface of the sheet, whereby a superior coat- ing adherence is realized.
文摘With the rapid development of the automobile industry, the use of galvannealed and galvanized steel sheets in automobiles is on the rise. These sheets must meet very high surface quality requirements. The surface treatment of line rolls is known to have a great impact on strip quality. To prevent dusts such as zinc ash from pressing into the strip surface, we used a composite thermal spray surface treatment technique to treat rolls. The successfully developed tungsten carbide （WC） ＋ Ni-P composite plating technology improved the quality of the tungsten carbide thermally sprayed WC roll surface. This technique is also helpful to control defects such as adhered foreign materials in hot-dip galvanized automobile outer panel surfaces.
文摘In recent years, the waterborne free intermediate coating process has been widely used in the automotive industry. Because the baking times and coating thickness are decreased, the surface covering capability of the painting process is reduced, which directly affects the appearance quality（ long-and short-wave values） of the body paint. Thus, there are correspondingly higher requirements for the white body surface profile prior to painting. The surface profile of the white body is mainly affected by the plate material, the surface profile, and the deformation process. So,the change rule for the surface profile during deformation of the steel plate is a key factor in coating appearance optimization. In this paper, we first analyze the typical deformation of the outer cover of a car body. Then ,we examine the change tendency of the surface profile of steel plates with respect to different deformation rates, specifically for a steel plate comprising a hot-dip galvanized bake-hardened steel sheet. Based on our analysis of the influence of the deformation on the coating appearance,we selected 3% ,5% ,and 8% deformation rates in this research. We found the roughness （Ra） value in the typical deformation range （3% -8% ） of the car body to exhibit a decreasing trend at first and then an increasing trend. The Ra value of the 8% deformation is not more than the original plate test value. When the Pc value of the original plate is in the lower range （ about 60）, it exhibits a slight increasing trend in the deformation process （3 % -8 % ）. And when the Pc value of the original plate is in the higher range （ about 120 ）, it exhibits no increasing trend in the deformation process （ 3% -8% ）. In contrast,the waviness （WCA） value in the car body＇s typical deformation range （3%-8%） shows a significant growth trend.
文摘An iron and steel company＇ s hot galvanizing technology was chosen as the object. An orthogonal experimental scheme with 5 factors of mixed level was designed, according to the various factors affecting the distribution of slag. For each scheme, the amount of slag and slag height in different orthogonal schemes by simulation were obtained with FLUENT software. Then, range and variance analyses were selected to compare the trend of slag height in the different process parameters of the hot dip galvanizing process. Finally, the optimal combination of the process parameters was obtained.
文摘The microstructure of hot-dip galvanized Zn-ll%A1-3%Mg-0.270Si alloy coating was studied in this article. X-ray diffraction analysis revealed the coating is composed by Zn, A1 and MgZn2 phase. Optical microscope （OM） and scanning electron microscope （SEM） observations showed the coating is occupied by snowflake-like dendrite, double hexagonal organization and eutectic. The coating backbone was the dendrite considered to be a phase of hexagonal close-packed （HCP） structure judging form its morphology according to the crystal growth way in the coating. Transmission electron microscopy （TEM） and energy dispersive spectroscopy （EDS） researches on the dendrite suggested that an intermediate Zn-A1 phase was formed at high temperature, then decomposed into a type of Zn-A1 granular eutectoid after cooling down to room temperature, while the eutectoid Zn and A1 had a certain crystallographic relationship. The coating solidification process and the grain crystal structure were discussed.
基金This work was supported by the National Key Research and Development Program of China(Grant No.2017YFB0702100)the State Key Laboratory of Baiyunobo Rare Earth Resource Researches and Comprehensive Utilization(2018Z2001).The authors gratefully acknowledge support for materials analysis and research from Instrumental Analysis and Research Center of Shanghai University.
文摘Scanning electron microscopy,X-ray diffraction,a neutral salt spray test,and electrochemical methods were applied to observe the microstructure and test the corrosion resistance of hot-dip galvanized steel before and after the addition of La and Ce.La/Ce mixture existed in the form of(La,Ce)Zn13 on the coated surface,decreased the coating thickness and accelerated the zinc dendritic growth.The corrosion current density of Zn-0.1La-0.1Ce coating was 63%less than that of pure Zn coating.This phenomenon can be explained that La/Ce mixture inhibited the transformation of Zn5(OH)8Cl2·H2O into Zn5(CO3)2(OH)6 or ZnO,reduced the time for appearance of red rust,and thus enhanced the stability of corrosion products and delayed the oxidation and corrosion processes of galvanized coating.La/Ce mixture improved the corrosion resistance compared to a single La or a single Ce addition.A competitive relationship between La and Ce was observed in the corrosion resistance improvement of hot-dip galvanized steel.
基金Funded by the National Natural Science Foundation of China(Nos.51971039,51671037)the Natural Science Research Project of Higher Education of Jiangsu,China(No.19KJA530001)Postgraduate Research&Practice Inovation Program of Jiangsu Province(No.KYCX20-2574)
文摘Wettability of Zn-Al alloy melt on the pure iron substrate at 450℃was studied.The effect of Al content(Zn,Zn-1Al,Zn-2Al,Zn-3Al,Zn-4Al,and Zn-5Al)on the wetting behavior and interfacial reaction was investigated by high-temperature contact angle measuring device and scanning electron microscope(SEM).The results show that,with the increase of Al content,the initial contact angle of the molten alloy on the substrate decreases gradually and the wettability increases gradually.Compared with the initial contact angle,the final contact angle is slightly reduced,because the Fe-Al inhibition layer is preferentially formed at the interface when adding Al to the alloy.The presence of Al will promote the occurrence of the reactive wetting,leading to an insignificant wetting spreading process,and the final contact angle negligibly differs from the initial contact angle.The adhesion work and charge density distributions of interface systems were calculated based on the first-principles.The results show that the adhesion work of the Fe/Zn and Fe/(Zn-Al)interface model is 2.0171 J/m^(2)and 13.7944 J/m^(2),respectively.The addition of Al greatly increases the adhesion work between alloy melt and iron substrate.Compared with the Zn-Fe and Al-Fe interface models,it can be seen that a significant charge migration phenomenon occurs between the interfaces.The amount of charge migration in the Al-Fe interface model is much larger than that in the Zn-Fe interface model,indicating that the bonding between Al-Fe atoms can occur more easily and the interaction between Al-Fe interfaces is stronger.This is also the reason why the addition of Al increases the adhesion work between interfaces.
基金Item Sponsored by National Natural Science Foundation of China(59995440)
文摘Hot-dip galvanized sheet is wildly used in construction,household appliances,ship,vehicle and vessel building and machinery,etc.In last ten years,with the development of automobile industry,the anti-eorrosion requirements for car body are increasingly strict,by which the rapid development in technology has been promoted.The application of hot-dip galvanized sheet,technological progress in production and some Chinese large units were introduced.
文摘In this study,the factors affecting the formation of small black spot defects on the surface of a hot-dip galvanized pure zinc strip are analyzed. These defects are primarily formed w hen the iron-aluminum inhibition layer is incompletely formed or fails to form or when foreign matter adheres to the surface or embeds in the zinc layer.The defects can be reduced by controlling the cleanliness and activity of the strip base before coating,regulating the zinc pot process parameters,and ensuring the cleanliness of the passline and workshop.
文摘Bottom dross obtained from zinc bath and the typical bottom dross defects on galvanized and galvannealed coating were metallographically investigated.Galvannealing simulations with different holding time were conducted,and the bottom dross transformation behavior during the galvannealing process was revealed.The fast diffusion between bottom dross particles and the surrounding zinc occurs during the galvannealing process,resulting in the formation of an Al-containing Zn-Fe intermetallic outburst structure at the defect position.The thicker and harder coating will cause a shiny spot on the coating surface and a deep dent on the substrate after being temper rolled.
文摘At first, a series of finite element method （FEM） simulation tests were used to find the critical forming conditions of hot-galvanized sheet steel during the rectangular box drawing processing when constant blank holder forces were applied. According the test results, the reasonable alteration scope of initial variable blank holder force （VBHF） was as 1.9-2.3 T. Then, based on the test productions of blank holder force, 12 typical VBHF curves were applied to perform the simulation tests by the simulation software of DYNAFORM. The simulation test results showed that VBHF had great effects on drawing formability of hot-galvanized sheet steel during the rectangular box drawing. However, the different VBHF curves were applied to control the whole drawing and it would get great different effects. At the same tine, the VBHF had great effects on the maximum thick thinning ratio, but had little effect on the maximum thick incrassation ratio. So, reasonable application of the VBHF would greatly decrease the fractures. When the VBHF profile is taken as curve L, the best effect of drawing formability could be obtained. When curve I is used, contrary effect could be gotten. The other types of curves would cause effects between above two types of VBHF curves. Finally, the actual tests were applied to check the validity of the FEM simulation tests. The results show that the FEM simulation tests are good ways for predicting and optimizing the VBHF.
文摘China has become the maximum household appliances manufacturing base worldwide.It is a new challenge facing the steel industry to develop the low-cost and environment-friendly sheet for household appliance industry,so Cr-free anti-fingerprint hot-dip galvanized sheet for household appliances is the upgraded product which satisfies the requirement of China household appliance industry' s nuisanceless treatment.The paper discusses the technical key points of development on Cr-free anti-fingerprint galvanized sheet for household appliances,including the development of the Cr-free anti-fingerprint chemical and the production technology of Cr-free anti-fingerprint galvanized sheet for household appliances.The paper elaborates the main compositions,physical features and properties of the Cr-free anti-fingerprint chemical, surface quality control technology,anti-fingerprint coating quality control technology,influence of anti-fingerprint film weight on corrosion resistance,conductibility,high-temperature discolouration resistance,acid resistance,alkaline resistance and solvent resistance of Cr-free anti-fingerprint hot-dip galvanized sheet, influence of anti-fingerprint coating uniformity on paintability of the sheet,influence of strip surface roughness on corrosion resistance and conductivity of the sheet and influence of strip surface quality on corrosion resistance of the sheet.Adopting the suitable Cr-free anti-fingerprint chemical and the reasonable production process parameters,the properties of the Cr-free anti-fingerprint hot-dip galvanized sheet conform to the delivery technical norms and the Cr-free anti-fingerprint hot-dip galvanized sheet becomes the new material for household appliances such as computer case.
文摘The main objective of this work was to evaluate the presence of lead and cadmium in galvanized steel tubes by hot-dip used exclusively for drinking water supply.In this research,samples of galvanized tubes were removed from walls of residential buildings with 30 years of use.In the process of hot galvanizing,the manufacturing standards allow or for low cost conveniences,and the use of primary zinc ingot with 1.6%metallic impurities,such as lead and cadmium,is allowed,enabling the incorporation of these metals into the zinc coating deposited on the carbon steel.The associated corrosion of these tubes can release these toxic metals,contaminating the drinking water used by residents.The samples taken from the tubes were evaluated by a square-wave anodic stripping voltammetry technique,and the results for lead and cadmium suggested randomly distributed levels,indicating that the contents of these contaminants depend mainly on the quality of the added primary zinc and the operational conditions of the immersion bath.The metallographic evaluations performed on the samples of the galvanized tubes showed irregularities in thickness and even a lack of the zinc layer deposited on the carbon steel surface.These facts suggest that galvanized tubes should not be used for drinking water.
文摘Taking the intelligent improvement of hot-dip galvanizing production line as the object, the whole production line is upgraded through the accumulation and comparison of empirical data, so as to improve the intelligent, standardized and functional design of hot-dip galvanizing production line, improve the ability of hot-dip galvanizing enterprises in production cost, product quality and delivery date, and enhance the competitiveness of their products in the market, so as to obtain the ability of sustainable development.
文摘The chemical composition of the zinc bath can strongly influence on the hot-dip galvanized coatings. In this work, the effects of tin addition on the surface morphology, and the corrosion resistance of hot-dip galvanized steel were investigated. The corrosion behavior of steel samples galvanized with zinc and Zn-Sn alloys containing different wt% Sn was analyzed by various corrosion tests such as potentiodynamic polarization Tafel lines and electrochemical impedance spectroscopy (EIS) techniques. Salt spray test was employed in order to study the corrosion products of the specimens. Surface morphology, the composition of coating layers and nature of the corrosion products were also investigated using field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray analysis (EDX) and X-Ray diffraction (XRD) techniques, respectively. The results indicated that the addition of small amounts of Sn (0.1 wt%) to the molten zinc galvanizing bath can improve the corrosion resistance of hot-dip galvanized steel.
