Coke behavior with H_(2)O in a hydrogen-enriched blast furnace:A review

Hydrogen-enriched blast furnace ironmaking has become an essential route to reduce CO_(2)emissions in the ironmaking process.However,hydrogen-enriched reduction produces large amounts of H_(2)O,which places new demands on coke quality in a blast furnace.In a hydrogen-rich blast furnace,the presence of H_(2)O promotes the solution loss reaction.This result improves the reactivity of coke,which is 20%-30%higher in a pure H_(2)O atmosphere than in a pure CO_(2)atmosphere.The activation energy range is 110-300 kJ/mol between coke and CO_(2)and 80-170 kJ/mol between coke and H_(2)O.CO_(2)and H_(2)O are shown to have different effects on coke degradation mechanisms.This review provides a comprehensive overview of the effect of H_(2)O on the structure and properties of coke.By exploring the interactions between H_(2)O and coke,several unresolved issues in the field requiring further research were identified.This review aims to provide valuable insights into coke behavior in hydrogen-rich environments and promote the further development of hydrogen-rich blast furnace ironmaking processes.

Comparison of the corrosion behavior of AM60 Mg alloy with and without self-healing coating in atmospheric environment

Coatings on the surface of Mg alloys are inevitably damaged during their practical applications,and corrosion can easily initiate from the damaged areas to accelerate the failure of Mg parts.A dual self-healing coating has already been developed to solve this problem in our previous work.Considering the practical application of this coating,it is necessary to investigate its service behavior in atmospheric environment.Thus,the corrosion behavior of AM60 Mg substrate with and without the self-healing coating was compared in Shenyang industrial atmospheric environment.The results show that the enrichment of sediments and rainwater on the scratch areas can accelerate the corrosion of the exposed Mg substrate.The inhibitors can be released from the damaged coating to inhibit corrosion.The dual self-healing coating shows better inhibition ability to narrow scratches due to the higher inhibitor concentration and less resumption.Also,the coating with wide scratches displays enough inhibition ability as well.The dual self-healing coating is a good alternative for Mg alloy parts in the practical applications.

Fatigue Cracking Characterization of High Grade Non-oriented Electrical Steels

The fatigue behavior of 30 WGP1600 non-oriented electrical steel, which is generally used in the motors for electrical vehicles, was investigated. The detailed microstructure and dislocation configurations of the fatigue specimens were examined by OM, SEM, and TEM. The test results showed that fatigue cracks were commonly initiated from the surface grain boundaries, crystals plane, and inclusions. The rapid fatigue crack propagation was characterized by transgranular cleavage fracture, while most transient fracture exhibited ductile tearing characteristics. After cyclic deformation of the non-oriented electrical steels, various dislocation structures, such as short and thick lines, veins, persistent slip bands, cells, and labyrinth, were observed.

Fatigue characteristics of sand-cast AZ91D magnesium alloy

The fatigue characteristics of the AZ91D-T6 alloy samples taken from engine blocks have been investigated at 20℃ and elevated temperature(150℃).The fatigue strength and cyclic stress amplitude of the alloy significantly decrease with the increase of the test temperature,although cyclic hardening occurs continuously until failure for both temperatures.With the increase of the temperature,the decreased fatigue life of the alloy tested at the same stress amplitude is mainly attributed to the decreased matrix strength and the increased hysteresis energies.Fatigue failure of the engine blocks made of AZ91D-T6 alloy is mainly controlled by casting defects.For the defect-free specimens,the crack initiation behavior is determined by the single-slip(20℃)and by environment-assisted cyclic slip(150℃)during fatigue,respectively.The low-cycle fatigue lives of the alloy can be predicted using the Coffin-Manson relation and Basquin laws,the three-parameter equation and the energy-based concepts,while the high-cycle fatigue lives of the alloy fitted well with the developed long crack life model and MSF life models.

Characterization and Modelling of High Temperature Flow Behaviour of V Modified 2.25Cr-1Mo Heat Resistant Steel Plate

In order to study the high temperature flow behaviour of the V modified 2.25Cr-1Mo steel plate to guide the industrial rolling practice, the hot compression tests were carried out at the temperatures from 900 ℃ to 1150 ℃ and the strain rates from 0.01s^-1 to 1 s^-1 on Thermecmastor-Z equipment. Based on the experimental data of the hot compression tests, a kind of Arrhenius-type constitutive equation was developed.The equation can accurately show the relationship between the flow stress and the deformation temperature, the strain and the strain rate. The measured true stress-true strain curves exhibit two kinds of flow stress curves. Moreover, the forming mechanisms of these two types curves were explained by softening, wok hardening theory as well as metallographic and hardness experimental results. The accuracy of the developed Arrheniustype constitutive equation was identified by three kinds of statistic parameters and also by comparison of the measured and predicted data. The reasonable value of the three types of statistic parameters and the good agreement between the experimental and predicted data can confirm the validity of the developed Arrheniustype constitutive equation for V modified 2.25 Cr-1 Mo heat resistant steel plate.

A study of interparticulate strain in a hot-extruded SiC_p/2014 Al composite

We report a correlative study of strain distribution and grain structure in the Al matrix of a hot-extruded SiC particulate-reinforced Al composite(SiC_p/2014 Al). Finite element method(FEM) simulation and microstructure characterization indicate that the grain structure of the Al matrix is affected by the interparticulate strain distribution in the matrix during the process. Both electron-backscattered diffraction(EBSD) and selected-area electron diffraction(SAED) indicated localized misorientation in the Al matrix after hot extrusion. Scanning transmission electron microscopy(STEM) revealed fine and recrystallized grains adjacent to the Si C particulate and elongated grains between the particulates. This result is explained in terms of recrystallization under an interparticulate strain distribution during the hot extrusion process.

Microstructure and texture in an extruded Mg-Al-Ca-Mn flat-oval tube

In the present study,mechanical property,microstructure and texture of an extruded Mg–1.0Al–1.5Ca–1.0Mn(wt.%)flat-oval tube in both the flat and the oval regions were systematically studied.Our results show that there exists a great difference in microstructure and texture between the flat and the oval regions.Both the flat and the oval regions have fine DRXed grains of 3–4μm,while more row stacked grains are observed in the flat region.A large number of fine particles with a size of about 0.5μm are dispersed in both the grain boundary and grain interior.The particles exhibit a uniform distribution in the oval region,while they tend to aggregate into bands along the extrusion direction(ED)in the flat region.The texture in the oval region is similar to that in extruded Mg rods with a preferred distribution of prismatic planes and random distribution of(0002)poles around the ED,while that in the flat region is close to that in extruded sheets containing two texture components,<0002>//normal direction(ND)and<0002>//transverse direction(TD).A high fraction of<0002>//TD component,about 52–62%,is observed in the flat region.The flat region has a tensile yield strength of 254 MPa,an ultimate tensile strength of 290 MPa and an elongation to failure of 4.3%.

A stencil-like volume of fluid (VOF)method for tracking free interface

A stencil-like volume of fluid （VOF） method is proposed for tracking free interface. A stencil on a grid cell is worked out according to the normal direction of the interface, in which only three interface positions are possible in 2D cases, and the interface can be reconstructed by only requiring the known local volume fraction information. On the other hand, the fluid-occupying-length is defined on each side of the stencil, through which a unified fluid-occupying volume model and a unified algorithm can be obtained to solve the interface advection equation. The method is suitable for the arbitrary geometry of the grid cell, and is extendible to 3D cases. Typical numerical examples show that the current method can give ＂sharp＂ results for tracking free interface.

Damage Mechanism and Structure Analysis of Used Clay Checker Bricks for Regenerators of Coke Ovens

During long-term use,the clay checker bricks for regenerators of coke ovens on gas side react with the impurities containing Fe and K20,causing foaming,softening and deformation,which is not only related with the impurity content and properties of the clay checker bricks,but also related with the type and the composition of the dust in the gas.After long term use,the clay checker bricks of coke ovens on air side have relative lower impurities containing Fe and K20.The inferior clay checker bricks,with high impurity content and high porosity,are easy to pulverize and deteriorate due to the oxidationreduction reaction with the iron oxide and the gas.The gas quality shall be concerned for long service life of the coke oven regenerators.

Optimisation of alloy composition for highly-formable magnesium sheet

The effectiveness of Ca or Gd addition on ductility and formability of Mg-Zn-Zr based dilute alloys in deep drawing has not been systematically compared previously.In this study,formable Mg-Zn-Gd-Zr and Mg-Zn-Ca-Zr sheet alloys are produced by hot rolling.These sheets have similarly weakened basal texture,but the sheet of the Mg-Zn-Gd-Zr alloys has higher ductility and formability than that of Mg-Zn-Ca-Zr alloys.The combined addition of 0.2wt%Ca and 0.4wt%Gd to the Mg-1Zn-0.5Zr(wt%)alloy leads to a Mg-1Zn-0.4Gd-0.2Ca-0.5Zr alloy that has even better ductility,and its formability during deep drawing is comparable to the benchmark Al6016 sheet.An increase in Ca content from 0.2wt%to 0.5wt%leads to decreased sheet ductility and formability,predominantly due to grain boundary embrittlement.

Preface

25 years ago, Baosteel＇ s 1 st cold rolling mill was put into production. Since then, Baosteel has been exploring its own way to promote technology progress. In the beginning, the company imported the core technology from abroad, and after years of assimilation and absorption, it gradually achieved independent innovation. So far, Baosteel has always been leading the developing trend of the cold rolling technology, and its products represent the highest level in China, and are also one of the best in the world.

Preface

Over the past five years, stainless steel products in Baosteel have got a very rapid development in R＆D and application. In Baosteel Stainless, ultra-pure ferritic stainless steel with medium chromium, nitrogen alloyed austenitic stainless steel and duplex stainless steel with high properties have been developed with the technical properties reaching, or even better than those of the similar products in China and abroad. Some products have been widely used in automobile, household appliances, building, railway, nuclear power and chemical industries as the Chinese economy develops. The significant progress has been made for processing technologies, such as C ＋ N control, non metallic inclusion control during steelmaking, equiaxed crystal control during continuous casting, sticking and edge crack control during hot rolling as well as cold tandem rolling for ultra-pure ferritic stainless steels through continuous effort of innovative research and development. Baosteel Stainless is now the leading stainless steel producer in China and one of the best in the world regarding products and processing technologies for ferritic stainless steels.

Competitive role of film-like austenite and transition carbides on hydrogen embrittlement resistance and impact toughness in bainite-containing quenched and partitioned steel

A microstructure composed of martensite matrix,lower bainite,and stable film-like austenite was designed by a quenching and isothermal bainitic holding process in a 0.30C–2.69Mn–1.71Si(wt.%)steel.The yield strength,tensile strength,and ductile-to-brittle transition temperature(DBTT)of the high-strength steel thus obtained were 1263 MPa,1521 MPa,and-33℃,respectively,and at-20℃,it showed superior low-temperature toughness,which reached 77.5 J/cm^(2).Meanwhile,it showed excellent hydrogen embrittlement(HE)resistance,and the total elongation loss is only 3.1%after 15 min of hydrogen charging.The excellent comprehensive performance is attributed to the fact that fine stable austenite with film-like morphology hindered the crack nucleation and propagation,and hindered hydrogen diffusion as a hydrogen trap.However,with a decrease in the isothermal temperature,transition carbide precipitation was accompanied by a further decrease in austenite grain size.For this condition,although transition carbides can act as effective hydrogen traps,excessive precipitation decreased the carbon content of retained austenite and increased the deformation heterogeneity between austenite and martensite matrix,leading to weakened austenite stability and HE resistance,a total elongation loss of approximately 39%(15 min hydrogen charging),a sharp decrease in impact toughness,and an increase in DBTT.The competitive role of film-like austenite and transition carbides on the comprehensive mechanical performance of steel is revealed,especially the suppression of crack nucleation and propagation that will provide a guide for the design of high strength steels with excellent impact toughness and HE resistance.

Strain-controlled fatigue characteristics of a cast Mg-Nd-Zn under peak-aged and over-aged conditions

Strain-controlled fatigue characteristics of peakaged and over-aged Mg_(96.47)Nd_(2.9)Zn_(0.21)magnesium alloys containing 0.42Zr,including stress response,strain resistance,hysteresis loops,strain-life and corresponding lowcycle fatigue life prediction model,were studied.In the peak-aged state(T61:540℃×8 h+200℃×14 h),the alloy shows higher cyclic stress response,but lower ductility than the alloy in the over-aged state(T6_(2):540℃×8 h+200℃×400 h).The yield strength and ultimate tensile strength of the alloy under T6_(1)-and T6_(2)-treated conditions are close.Compared with T6_(1)-treated alloy,the steady stress amplitude occurred in T6_(2)-treated alloy is due to higher ductility and more homogenous deformation.In T6_(1)state,the fatigue cracks in the alloy first initiate along the cracked persistent slip bands and then propagate in the trans-granular mode,while in the T6_(2)state,the fatigue cracks initiate along grain boundaries and then propagate in the inter-granular mode.

Effect of heat treatment on strain–controlled fatigue behavior of cast Mg–Nd–Zn–Zr alloy

The influence of heat treatment on the strain-controlled fatigue behavior of cast NZ30 K alloy was investigated. Compared with the as-cast and solutionized（T4） alloys, the peak-aged（T6） and over-aged（T7）counterparts have a higher cyclic stress and a lower plastic strain value due to the precipitation strengthening. The as-cast and T4-treated alloys have a higher fatigue strength/yield strength ratio than the aged alloys, which is mainly attributed to their higher cyclic hardening. Under stress-controlled loading,the aged alloys show lower hysteresis energies than the as-cast and T4-treated counterparts, leading to longer fatigue lifetimes. For the T4-treated alloy, the cyclic hardening and fatigue failure are controlled by the dislocations-slip and twinning, while for both the as-cast and T6-treated counterparts, they are controlled by the dislocation-slip. For the T7-treated alloy, cyclic deformation and failure behavior are mainly dependent on dislocations-slip and grain boundary sliding.

Granular Carbides-Assisted Ultrafine-Ferrite Fabrication in the Pearlitic Steel Without Severe Plastic Deformation and Annealing

The evolution of ferrite grain and cementite lamella during cold rolling in a granular carbide–pearlite steel has been investigated.Particular attention has been given to a quantitative characterization of changes in the ferrite grains.Electron backscattered diff raction and transmission electron microscopy observations show that the ultrafi ne ferrite(~388 nm)can be produced through low equivalent strain cold rolling without severe plastic deformation(SPD)and annealing.The average grain size of ferrite depends on the volume fraction,shape and distribution of granular carbides as well as interlamellar spacing of pearlite.A general explanation of granular carbides-assisted grain refi nement is that the embedded carbides between natural barrier will signifi cantly facilitate dislocation nucleation during cold rolling.Dislocation reaction occurs more drastically and quickly near these granular carbides.Such reactions promote the formation of high-angle grain boundaries.The formation of ultrafi ne ferrite grains and subgrains in steel after cold rolling toε=1.4 strain makes the strength and ductility increased simultaneously compared withε=0.6 cold-rolled steel.The results suggest a new material design strategy to obtain ultrafi ne-grained structure via the granular carbides assistance.

Coupling effect and characterization modeling of iron ore fines mixing and granulating at 0-1 mm

Characteristic of iron ore is the essential factor of granulating.Three ores,namely specularite,magnetite concentrate and limonite,were selected as adhesion powder to investigate granulating behavior and evolution process of agglomeration.Experiments and modeling were performed to represent granulating behavior on the basis of selectivity,ballability and adhesion rate.The mass fraction of water and particles size of adhesion and nucleation were set at(11±1)%,0-1 mm and 3-5 mm,respectively.Experimental results show that selectivity and ballability promote the evolution of granulation.The water absorption rate of specularite and the ballability of limonite are better.The coupling effects exist in two ores mixing and present positive effect when the proportion of magnetite concentrate is greater than that of specularite or specularite and limonite blend.During three ores mixing,the coupling effect presents a complex superposition state.A characterization model of adhesion rate of mixing granulation was established by random forest algorithms.Its output is adhesion rate,and its inputs include water absorption rate,balling index and mixing proportion.The model parameters are 957 trees and four branches,and the training and prediction errors of the model are 2.3%and 3.7%,respectively.Modeling indicates that the random forest model can be used to represent coupling effects of mixing granulation.

Influence of inclusions on hydrogen-induced delayed cracking in hot stamping steels

The hydrogen-induced delayed cracking(HIDC)behaviors of two types of 1500 MPa grade hot stamping steels(HSSs)have been investigated by the method of slow strain rate tensile test and hydrogen permeation,where one is manufactured by compact strip production(CSP)process which is a revolution to the traditional HSS and the other by the traditional cold rolling process.The results show that the performance of HSS produced by CSP is superior to that of the traditional HSS,due to lower hydrogen embrittlement index,lower hydrogen diffusion coefficient and lower hydrogen content.It has been found that HIDC behavior is closely associated with inclusions.The inclusions of HSS produced by CSP are mainly spherical Al-Ca-O and CaS,while the inclusions in the traditional HSS are TiN+AI2O3+MnS with sharp edges and corners.Based on these results,the influence of composition,shape and distribution of inclusions in HSS on HIDC and the mechanism of HIDC from the perspective of inclusions were analyzed and discussed.

Correction to:Influence of inclusions on hydrogen-induced delayed cracking in hot stamping steels

Correction to:J.Iron Steel Res.Int.(2019)26:1199-1208 https://d0i.0rg/l 0.1007/S42243-019-00312-z The original version of this article unfortunately contained a mistake.Table 6 was incorrect.The corrected table is given below.The line 11 of page 1205 is revised as“The diffusion coefficient of hydrogen in CSPS is 2.76×10^(-7)cm^(2)/s,which is lower than that of CRS”.