Recent development of UHSS and its hot-dip galvanizing processes in Baosteel

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.

Electrochemistry and DFT study of galvanic interaction on the surface of monoclinic pyrrhotite(001)and galena(100)

The electrochemical interaction between galena and monoclinic pyrrhotite was investigated to examine its impact on the physical and chemical properties of the mineral micro-surface.This investigation employed techniques such as electrochemistry,metal ion stripping,X-ray photoelectron spectroscopy,and quantum chemistry.The electrochemical test results demonstrate that the galena surface in the electro-couple system exhibits a lower electrostatic potential and higher electrochemical activity compared to the monoclinic pyrrhotite surface,rendering it more susceptible to oxidation dissolution.Monoclinic pyrrhotite significantly amplifies the corrosion rate of the galena surface.Mulliken charge population calculations indicate that electrons are consistently transferred from galena to monoclinic pyrrhotite,with the number of electron transfers on the mineral surface increasing as the interaction distance decreases.The analysis of state density revealed a shift in the surface state density of galena towards lower energy levels,resulting in decreased reactivity and increased difficulty for the reagent to adsorb onto the mineral surface.Conversely,monoclinic pyrrhotite exhibited an opposite trend.The X-ray photoelectron spectroscopy(XPS)test results indicate that galvanic interaction leads to the formation of hydrophilic substances,PbS_(x)O_(y) and Pb(OH)_(2),on the surface of galena.Additionally,the surface of monoclinic pyrrhotite not only adsorbs Pb^(2+)but also undergoes S^(0) formation,thereby augmenting its hydrophobic nature.

ToF-SIMS characterization of a bare-spot defect in a hot-dip galvanized boron-added steel sheet

To determine the root cause of a bare-spot defect in a hot-dip galvanized boron-added steel sheet,we performed metallurgical characterizations using time-of-flight secondary ion mass spectrometry(ToF-SIMS)in addition to glow discharge optical emission spectrometry,field-emission scanning electron microscopy(FE-SEM),and energy dispersive spectroscopy.Mn and B enrichments on the steel surface in the bare-spot area were detected through various methods.FE-SEM revealed external oxide nodules and zinc droplets,which indicated poor wettability.ToF-SIMS further revealed considerably more detailed lateral and depth distributions of Mn,B,and Al.The formation of external Mn-B compound oxides on the steel surface prior to hot dipping,which substantially deteriorated the wettability and prevented the formation of a Fe_(2)Al_(5)inhibition layer,resulted in the formation of a bare-spot defect.ToF-SIMS mapping of Al ion proved that a slight reaction still occurred between the dissolved Al in the molten zinc bath and steel substrate,although no evident Fe_(2)Al_(5)inhibition layer formed in the bare-spot area.

Investigation and improvement of tiny spot defects on hot-dip galvanized automotive steel sheets

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.

Galvanic Skin Response—Extinction Biofeedback Training for Psychogenic Abdominal Pain: A Validation Protocol

Abdominal and pelvic pain of psychogenic origin is a widespread, disabling, difficult to identify, and often inadequately treated medical condition. This condition is often associated with poor quality of life due to high pain interference with daily activities. Cognitive behavioral psychological therapy and neuromodulation with biofeedback are validated therapies for the treatment of this condition. Aim of the present research work is the validation of a therapeutic protocol that involves the use of both techniques in combination. 20 patients diagnosed with psychogenic abdominal pain, of both sexes, aged between 18 and 60 years who had not benefited from pharmacological therapies were enrolled. 10 patients were randomly assigned to the control group (psychological treatment only), another 10 patients were assigned to the study group (neuromodulation with biofeedback-Galvanic skin response-extinction in combination with psychological therapy). For both groups, the pain score, interference of pain with daily living activities, pain relief, and the share of anxiety associated with the pain condition were evaluated (pre- and post-treatment). The patients who underwent the combined treatment achieved statistically significant better scores than patients in the control group, respectively −4.9 ± 0.9 vs −1.0 ± 0.4 for Pain;−5.1 ± 1.1 vs −0.9 ± 0.3 for Interference with life;−7.2 ± 3.7 vs −2.2 ± 2.1 for HAMA;4.6 ± 1.2 vs 1.1 ± 0.6 for Relief.

Design of TRIP Steel With High Welding and Galvanizing Performance in Light of Thermodynamics and Kinetics

A new type of transformation induced plasticity （TRIP） steel with not only high strength and high ductility but also superior welding and galvanizing properties was designed and developed recently. Low carbon and low silicon content were preliminarily selected with the aim of meeting the requirements of superior quality in both welding and galvanizing. Phosphorus was chosen as one of the alloying elements, because it could reduce carbon activity in cementite and increase the stability of austenite. In addition, the possibility of phosphorus segregating at grain boundary was also discussed by thermodynamics as well as kinetics. Phase diagram was estimated at high temperature and the composition of the steel was then selected in the hyperperitectic range to avoid problems, which might occur in sheet steel continuous casting. Phase diagram in the inter.critical temperature was estimated for the steel to obtain the starting temperature of fast cooling. For understanding the minimum rate of fast cooling, pearlite growth kinetics was calculated with self-developed diffusion coefficients of elements in grain boundary. Overaging temperature was determined through the calculation of To temperature by both equilibrium and para-equilibrium assumptions, which was different from the current determination, which is only based on an equilibrium estimation.

Effect of hot-dip galvanizing processes on the microstructure and mechanical properties of 600-MPa hot-dip galvanized dual-phase steel

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.

Roll Shape Setting Technology of Hot Galvanizing and Planishing Mill

A roll shape setting model was built for the hot galvanizing and planishing mill. The uniform transversal distributions of the front tension in the exit and the unit pressure were considered as the objective function. At the same time, the quality of the products, the stability of zinc layer, and the homogeneity of spangles were of considerable significance in the planishing process. The model was applied to the roll shape setting of the 1800 cold rolling 3# CGL hot galvanizing and planishing mill of Baosteel Co Ltd. After being planished, the flatness of a strip that was less than 6 I was more than 97%, and the flatness of others were less than 10 I; the pass percentage of the zinc lay- ers reached 100%.

Preparation and hot-dip galvanizing application of CeO_2/Zn nanocomposite

CeO2/Zn nanocomposite was fabricated by high-energy ball milling and subsequent hot-press sintering under vacuum. The produced nanocomposite powders and bulks were characterized using X-ray diffraction （XRD）, transmission electron microscopy （TEM） and scanning electron microscopy （SEM） with an energy dispersive X-ray spectrum （EDS）. The as-fabricated nanocomposite bulks were added successfully into the hot-dip galvanizing bath to improve the corrosion resistance of coatings. The results show that after milling for 120min, nano-sized CeO2 particles are distributed homogeneously on the surface of fine Zn particles to form spherical-like nanocomposite powder with narrow grain size distribution. The subsequent sintering does not lead to a dramatic grain growth, and the distribution of CeO2 nanoparticles in the composite bulk is also homogeneous. With the addition of as-prepared bulks, the corrosion resistance of the galvanized coatings is improved obviously. It provides a feasible route for adding CeO2 nanoparticles into the hot-dip galvanized coating.

Cracking of S235JR Cold-Deformed Steel during Galvanizing—Developing a Test to Evaluate and Predict the Effect of the Zinc Alloy Composition

This paper presents a study on the cracking of steel pieces during their galvanization in alloyed liquid zinc. An experimental design was developed to show the effect of the amount of the various alloying elements (Sn, Bi, Pb) on this phenomenon. The characterization of the effect was obtained by 1) deformation by three-point bending of a piece of steel with different levels of deflection;2) galvanizing and 3) observation and measurement of the cracks. A model of the critical deflection (deflection for crack starting) with the amounts of Sn, Pb, and Bi is presented and the predictions are described.

Innovative integrating of hot-dipped(aluminizing) galvanizing lines and engineering of related equipment

Based on the continuous hot(aluminizing) galvanizing lines and related non-standard equipment of Meishan Steel,this paper presents the main contents of such integrated engineering and designing of equipment for the two hot-dipped galvanizing lines,as well as innovative techniques and their features.Led by Cold Rolling Project Department of Meishan Steel,Baosteel Engineering and Technology Group Co.,Ltd. ,working as the responsible unit of this project,develops key technologies and integrates the system by combining the equipment design and development capacity of Baosteel Engineering,research and development capacity of Research Institute of Baosteel,process production and equipment maintenance experience of Cold Rolling Plant,Equipment Department and Manufacture Department of Baosteel Corporation.Core technologies of the two lines are developed and designed through original and integrated innovation and innovation after digestion,focusing on eight core techniques in process equipment,annealing furnace,fluid installation and EIC system.As a result of integration in key process equipment,industrial furnace and EIC control,the cold rolling hot dipped(aluminizing) galvanizing lines take on a new look and reach an annual capacity of 200 000 t galvanized products and 250 000 t galvanized aluminium base strips respectively.These two world advanced lines are able to produce hot-dipped galvanizing products with high quality surface and fine shape,such as household appliance board and senior construction board.As a result, the process and equipment technology of the lines have formed domestic intellectual property.Thus,the technology has reference value for self-integration and equipment technology innovation of similar lines.

The new technical progress of hot dip galvanizing process without sink roll

In this paper,the recent state and problems of the sink roll in CGL are described.Several methods of increasing its operational life span are introduced,such as surface coating technology and sleeve material technology.Fundamentally they cannot solve the problems of surface quality caused by the contact between strip and roll.On this basis,the newly developed principle and solutions for hot dip galvanizing technology without sink roll are highly emphasized,they are Float Technology,Electromagnetic pump technology,Electromagnetic enclosed slot by high-frequency AC,Electromagnetic enclosed slot by high-frequency DC.A comparison among their functions and characteristics is made and the possibility of its application is also discussed.Finally it comes to a conclusion that electromagnetic enclosed slot represents the direction of a continuous hot-dip galvanizing steel strip in the the 21st century.It has a very broad application prospects.Baosteel Technology Center is focused on the research and development of this technology.As technology advances,industrial applications is possible.

Application of WC cermet sprayed composite coating in hot-dip galvanizing lines

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.

Simulation analysis of hot dip galvanizing process parameters based on orthogonal experimental design

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.

Preparation of Antimicrobial Iron Oxide Nanostructures from Galvanizing Effluent

Galvanization is the process of applying a protective zinc coating to iron or steel to prevent rusting. In the batch hot-dip galvanizing process, large amounts of wastes originate in liquid, solid and gaseous forms. Acidic waste containing iron and zinc ions is produced due to the cleaning of steel prior to zinc coating, which is considered the galvanizing acid waste. The galvanizing effluent used was collected from LTL Galvanizers Pvt. Ltd., Sapugaskanda, Sri Lanka, and converted into antimicrobial hematite (α-Fe2O3) nanoparticles. These nanoparticles were synthesized using a chemical precipitation method. X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) were used to characterize the nanomaterials produced. Two pathogenic bacteria and one pathogenic fungus were used to analyze the antimicrobial activity of the nanomaterials. All the samples showed excellent antibacterial and antifungal properties. And the material can inhibit the growth of both Gram-positive and Gram-negative bacteria. According to the SEM images, some of the hematite particles were around 100 nm in size or less, which confirms that the describing method is viable in synthesizing hematite nanostructures. As shown in the XRD, the major diffraction peak, located at 2θ of 35.617° (110) in addition to minor peaks at 24.87° (012), 33.07° (104), 42.08° (113), 51.18° (024), 53.52° (116) and, 57.46° (018) confirm the spinel structure of iron oxide (α-Fe2O3). The estimated average crystallite size of the nanomaterial is calculated to be 36.74 nm. The durability of the manufactured nanomaterial is excellent. This method is a time-efficient, environmentally friendly, cost-effective and industrially viable way to manufacture antimicrobial hematite (α-Fe2O3) nanomaterials from a galvanizing effluent.

Initial micro-galvanic corrosion behavior between Mg_(2)Ca and α-Mg via quasi-in situ SEM approach and first-principles calculation

The initial micro-galvanic corrosion behavior of Mg-30wt%Ca alloy only containing Mg_(2)Ca andα-Mg was studied by immersion testing in a 0.9%Na Cl solution at 37°C.The quasi-in situ SEM and TEM results show that Mg_(2)Ca corroded easier thanα-Mg,indicating that Mg_(2)Ca acted as an anode.The work function(Φ)for Mg_(2)Ca calculated by first-principles is significantly lower compared to that forα-Mg.The Volta potential measured by a scanning Kelvin probe force microscope reveals that the Mg_(2)Ca had a relatively low Volta potential(ψ)value.The lowerΦandψvalues for Mg_(2)Ca indicate a lower electrochemical nobility,which is consistent with the experimental phenomenon.

Galvanic corrosion of AZ31B joined to dual-phase steel with and without Zn layer by ultrasonic and friction stir welding

Galvanic corrosion of AZ31B joined with bare or Zn-coated DP590 steel by ultrasonic spot welding or linear friction stir welding was quantitatively studied by pre-defining anode and cathode in the lap joint samples. Corrosion volume and depth from Mg anode surfaces exposed to 0.1 M sodium chloride solution was analyzed as functions of cathode surface type and welding method. Characterization of as-welded joints was performed to identify any microstructural feature of the bonding zone that could impact galvanic corrosion behavior.COMSOL modeling with modified user subroutine was conducted to simulate the progression of Mg corrosion in the same joint and electrode configurations used for the corrosion experiments. The experimental results indicated that Zn-coated cathode surface can reduce Mg galvanic corrosion significantly as galvanic polarization and cathodic current on Zn-coated surface remained relatively low for Mg in the weld joints.COMSOL modeling described the growth of Mg galvanic corrosion in a reasonable manner but showed limitation by underestimating the corrosion volume as it did not capture self-corrosion.

Accuracy analysis of iron content of galvanized coating using an X-ray fluorescence spectrometer with an L-spectrum

The accuracy(repeatability and reproducibility) of the iron content analysis of galvanized coating using an X-ray fluorescence spectrometer with an L-spectrum is not better than that of flame atomic absorption spectrometry, sometimes it exceeds the quality control limit.Influences, such as current, voltage, equipment(internal circulating water, 10%CH4+90%Ar, and vacuum) checking, instrument monitoring, sample cleaning, and oper-ators, were investigated by means of 6-sigma and lean operations to improve accuracy.

钢铁海水电偶腐蚀的研究进展

对海洋工程装备中常用钢铁材料的电偶腐蚀研究进行了综述,分析了海水中钢铁电偶腐蚀的影响因素,着重探讨了海水中钢与异种金属和非金属材料连接时电偶腐蚀的研究现状,并对该领域的研究前景进行了展望。

核电厂海水泵用镀锌高强度螺栓的开裂原因

某核电厂海水泵用双头镀锌高强度螺栓发生开裂失效。通过材料性能(化学成分、显微组织和力学性能等)检测及断口和裂纹形貌观察,分析了螺栓的失效原因。结果表明:镀锌螺栓开裂的原因为氢致开裂。锌镀层破损的高强度螺栓与海水接触时,表面锌镀层和螺栓基体形成电偶对,基体作为阴极析出氢,部分原子氢扩散进入螺栓基体导致氢致损伤,螺栓在预紧力的持续作用下发生氢致开裂。