Study on the high-temperature properties of heat-resistant steel 309S

The properties of heat-resistant steel 309S at elevated properties were investigated.The results revealed a rapid decrease in the short-time tensile strength at elevated temperatures.At 1 000 ℃,the yield strength and tensile strength are 14% and 7% of their respective values at room temperature,respectively.The creep rupture strength was inferred in terms of the relationship between stress and duration time at high temperatures.After 1 000 h,the creep rupture strength is 37.98 MPa at 800 ℃,12.63 MPa at 900 ℃,and 7.27 MPa at 1 000 ℃.The fractures occurring at these high temperatures were intergranular in nature.Under the experimental condition,the fatigue limit stress is 25 MPa.The number of fatigue cycles and crack growth time decrease with increasing stress.Fracture morphology analysis shows that the fatigue cracks initiate on the surface of the sample and propagate through transgranular expansion.

Preface

Automotive steel is one of the strategic products of Baosteel. During the past three decades,Baosteel has developed various high-performance products to meet the needs of automakers and has achieved great success along with the rapid development of China’s automotive industry. Baosteel has become one of the top automotive steel producers in the w orld and a global material solution supplier for car makers.

Effects of Al and Ni on copper-rich phases in the scale/steel interface after high-temperature oxidation of copper-containing steel

A study was conducted on the formation of a Cu-rich phase at the scale/steel interface of Cu-containing steel by high-temperature oxidation with varying amounts of A1 and Ni. Both A1 and Ni were found to help decrease the amount of the Cu-rich phase at the interface. Analysis of the effects by these elements was conducted in terms of the melting point of the Cu-rich phase, the solid solubility of Cu in austenite, the rate of oxidation, and the amount of Cu-rich phase occlusions in scales. Because of selective oxidation,in which A1 and Ni are oxidized more and less preferentially than Fe, respectively, A1 was weakly concentrated at the interface whereas Ni was more heavily concentrated in it. Thus, A1 exerted no effect on the melting point of the Cu-rich phase, whereas Ni raised its melting point. A1, which was applied at contents of less than 2.0%, decreased the solubility of Cu in austenite but this effect weakened at the interface during oxidation. By contrast,Ni increased the solubility of Cu, and this effect was strengthened with oxidation. Both A1 and Ni promoted internal oxidation and the formation of occlusions.

Determining organic compounds in coking wastewater by SPME-GC /MS

The solid-phase microextraction （SPME） combined with gas chromatography/mass spectrometry （GC/MS） was used to determine and analyze organic pollutants in coking wastewater. Based on the fact that the main compounds in the wastewater were organics, some key parameters of the SPME were optimized. The method has good linearity （ its correlation coefficients 〉 0.99） in the range determined,its relative standard deviations （RSD） are less than 15%, and its recovery is from 87.9% to 128.1% with the lowest quantification limit of 5 ~g/L. This method has been used to measure 15 organic pollutants in wastewater from a certain coking plant. The results show that compared with the conventional method,it can save an hour in pretreatment time. It is a fast, low-cost, accurate, simple and efficient analytical method indeed.

Improvement in prolonging AOD refractory lining life in Baosteel

A series of improvements in prolonging the AOD refractory lining life in Baosteel are introduced and analyzed in this paper,including modification of the AOD shell shape, adjustment of the top slag components and selection of the side-blowing tuyeres. Firstly,the layout of side-blow tuyeres was altered with the angle between each two tuyeres being 22.5° instead of the original 18° ,and the connection of the outside steel shell in the side-blow area was modified from the former platform shape with great stress concentration into a new smooth circle shape. Secondly,the slag components were changed from the former CaO-FeO-SiO： system to the CaO-MgO-SiO2 system. Besides, the basicity of the top slag was kept higher than 1.8 ,and the MgO content in the slag was kept within the range of 8% - 12%. Finally,tuyeres with an inner diameter 13% smaller than that of the original tuyeres were used. Based on these research and optimization work,the thermodynamics and kinetics in the AOD refining bath has been improved markedly, and the campaign of the AOD has been prolonged from 45 heats at the beginning of its start-up to the current 185 heats. Meanwhile,the yield of chromium alloy and the decarburization efficiency have also been improved.

Industry experiment & effect of oxidation resistance coating for steel slab

Spraying test were conducted twice before steel slabs were put into the furnace and the effects of the oxidation resistance coating were investigated and verified. By comparing the change of slab weight, rolling force of the roughing mill ＆ finishing mill, thickness of oxide film on the surface slabs by an XL-30 SEM and acid pickling speed of slabs with and without coating,it was found that the oxidization waste in the furnace decreased by 40 percent with the use of the coating and the corresponding yield capacity could increase by 0.2 percent at least. Besides, the thickness of oxide scale film on hot roiled products was reduced by 1.44 micrometers and the acid pickling time was shortened by 6s with the coating technology, while the total rolling force of RM ＆ FM did not changed. Furthermore, the application prospect of this technology was also discussed in this paper.

Recent development of electrical steel sheets in China Steel Corporation

The major applications of electrical steel(ES) sheets are motors,transformers,etc.In recent years, the raise of crude oil price and increasing environmental consciousness trigger the demands for saving energy and reducing CO_2 emissions,which greatly accelerate the development of high quality ES sheets.To meet the quality requirements of high efficiency motors and transformers,high grade ES sheets with high flux density are continuously developed and introduced to the market.Meanwhile,the price competition and quality improvement of general grades are important for the lower end application.The iron loss of 50CS1300(50A1300) is significantly reduced by controlling some key parameters.Other than the normal grade,the highest grades of nonoriented (NO) ES are successfully developed recently.And all specifications of 0.50 and 0.35 mm among JIS C 2552 specification could be provided by CSC.As to the insulation coating development,the Cr-free insulation coating has been introduced to the market due to the environmental concern,and has been enormously adopted in Taiwan market.Furthermore,the thicker insulation coating technology has been successfully developed for specific wind power generator application.The newly developed products and quality improvements of electrical steel sheets in China Steel are introduced in this paper.

Research and development of hot-corrosion resistant superalloys

The hot-corrosion resistant superalloys have been widely applied in the gas turbines for power generation industry,the marine gas turbines in the aircraft carrier and missile destroyer as well as the aeroengines in shipboard aircraft and offshore fighter plane.Based on the ten kinds of hot-corrosion superalloys that were developed by the authors in the recent 10 years,the paper has reviewed the status and development of hot-corrosion resistant superalloys in domestic and overseas.The characteristics of chemical composition, microstructure,mechanical properties and manufacturing process are analyzed emphatically.Simultaneously the applications of hot-corrosion resistant superalloys are introduced as well.

Environmental compliance and profitable steelmaking-always a challenge!

Badische Stahlwerke in Kehl,Germany is located on the river Rhine close to the Black Forrest,which is a recreational area.As a consequence the environmental regulations for Badische Stahlwerke are even more stringent than the already stringent German regulations.Badische Stahlwerke elaborated over the years many concepts for the reduction of environmental impact by a steel plant.These concepts deal with the reduction of emissions to air water and soil,but also with the recycling of all by products from steel making like slag,dust,scale and some others.The success of these concepts can be seen by the very low emission values of Badische Stahlwerke and also the profit derived from the recycling of by-products. Other ideas have been worked out to minimize noise emissions and to detect radioactive sources which are coming together with the scrap into the steel making process.This problem is getting more and more serious. With the experience of more than 25 years in environmental protection in the steel industry,BSE can offer these concepts and solutions to other mini mills to shorten implementation time of environmental protection and to avoid expensive mistakes. This paper shows which level of emissions could be reached without having any disadvantage on productivity and gives an overview of various standards and practices in Europe and worldwide.

Challenges in the use of stainless steel slag

Stainless steel melting shops of Outokumpu Group are located in Finland,Sweden and England(UK). In all of the countries the European Union legislation is the same,but in practice the plants face different technical,economical and administrative challenges in developing sustainable treatments and use of by-products. Due to availability of good natural construction materials,the use of slag and other industrial by-products has been quite small in Northern Europe.Blast furnace slag has been completely utilized,while slag from stainless steel processes has earlier been regarded as waste.Steering of the metallurgical melt phase,slag cooling,treatment and metal recovery processes are the main technical challenges for increasing the sustainable use of stainless steel slag. Moreover,product properties have to fulfill standards and customer requirements.Dry or water-cooled EAF slag aggregates are typically used in road construction.Outokumpu has developed light mineral slag aggregates which are cooled in rapid water process.During this process,a specific structure and mineralogy is formed in the slag and leaching from the material decreases.In many regulatory discussions,it seems that there is not enough relevant scientific data from harmful compounds.Limit values are based only on laboratory tests and model estimations,not on the material use itself or real nature.A risk-based approach is needed when environmental acceptance is not clear.Limit values based on content are not applicable because environmental or health risks depend on the release or leaching of substances from the material.This is the case especially with metals.

Hot rolling pre-heating furnace model optimization technology

Furnace area is regarded as looper between casting and hot rolling,which is very important for material flow balance and production organization as well as temperature regulation etc.In particular,when dealing with energy saving and emission reduction and heating quality improving,pre;eating furnace is paid more attention.The radical target for preheating furnace is to transfer heating energy at the least cost. As we know,the preheating furnace is a dissipation system to obey conservation of energy law,that is to say that input energy always equals to output energy,in the meantime,the whole energy consuming is not reversible.Therefore increasing the efficiency of using energy is uppermost.In this paper,heating transfer efficiency is analysed and mathematical expression is given based on conservation of energy law.Typical optimal methods to improve preheating furnace transfer efficiency coming from foreign factories are presented.According to these methods,every furnace zone temperatures as control variable,target discharging temperature and temperature difference in slab thickness and the temperature between neighbouring zones as well as zone temporary temperature as restrictions,minimal energy consuming as optimizing target.Baosteel preheating furnace model structure and the complicated mapping relation of control parameter set and state set and aim set are presented.Important basic models in the preheating furnace model system are analysed including temperature tracking model and temperature forecasting model and discharging pacing model and slab heating curve.First slab temperature model structure and its peripheric parameter are introduced;second two pacing models are given including timing pacing mode using fixed discharging interval and mill pacing control mode using mill rolling pacing while Baosteel pacing forecasting model using long term and short term forecasting mode) is given;third a heating curve mathematical model considering heating quality and rolling pace and energy consuming is presented;in the end summary is done and the future way is lighted.Baosteel heating model including slab and billet and steel ingot have been developed,the actual applications show a good effect.The future woks include working procedure saving energy and system saving energy considering " Oder and rule" to achieve system harmony and rhythmization.Baosteel Blooming furnaces scheduling system is very useful for smooth production and saving energy.

Contributions to Baosteel Technical Research wanted

Baosteel Technical Research, a quarterly journal, which is issued domestically and abroad, is run and sponsored by Baosteel Group Corporation. Baosteel Technical Research mainly reports the achievements in technological innovation, academic research, new product development and industrial equipment improvement by Baosteel. It will continue to follow up on hot topics and serve the company * s technological development and progress. Its readers include experts in steel metallurgy and related fields,technicians,management staff, professors and students in universities and colleges. It mainly publishes academic and applicable papers on iron and steel metallurgy and related technical fields such as chemicals, metal forming, materials, mechanical and electrical technology, refractory, energy, automation instruments, comprehensive utilization and environmental protection.

Light weight analysis of a skeleton vehicle frame using BS960 super-high-strength steel

Static strength finite element analysis was conducted to decrease the weight of a skeleton vehicle＇s frame. Results indicated that the maximum stress occurs on the front beam ＇s variable section area. Dynamic sensitivity analysis elucidated the relationship between the maximum stress and the thickness of a particular beam,e. g.,top,middle,and bottom beam. Displacement was analyzed by the key part that influenced the maximum stress. Finally,the new plan using BS960 super-high-strength beam steel and the preferred beam thickness was compared with the original plan. New combinations of beam thickness were introduced on the basis of different purposes; the maximum responding light w eight ratio was 21%.

Effect of quenching temperature on the microstructure of Si-containing steel during quenching and partitioning

This study aims to investigate the effect of the 1-step quenching and partitioning （Q＆P） process on the microstructure and the resulting Vicker＇ s hardness of 0.3C-1.5Si-1.5Mn steel by using in-situ dilatometry ,optical microscopy （ OM ）, scanning electron microscopy （ SEM ）, X-ray diffractometry （ XRD ）, and Vicker ＇ s hardness measurement. Systematic analyses indicate that the microstructure of the specimens quenched and partitioned at 150℃ ,200 ℃ ,250℃ ,and 300℃ mainly comprises lath martensite and retained austenite. The dilatometry curve of the specimen partitioned at 150℃ is presumably ascribed to the formation of isothermal martensite. In the early stages of partitioning at 200℃,the nearly unchanged dilatation curve is closely related to the synergistic effect of isothermal martensite formation and transitional epsilon carbide precipitation. In the later stages of partitioning at 200 ℃ ,the slight increase in the dilatation curve is due to the continuous isothermal martensite formation. With further increase in partitioning temperature to 250℃, the dilatation increases gradually up to 3600 s, which is related to carbon partitioning and lower bainite formation. Partitioning at a higher temperature of 300 ℃ causes a rapid increase in the dilatation curve during the initial stages, which subsequently levels off upon prolonging the partitioning time. This is mainly attributed to the rapid diffusion of carbon from athermal martensite to retained austenite and continuous formation of lower bainite.

Research on welding technology of hot-rolled extra-high-strength steel developed by Baosteel

In this study, the welding technology of the hot-rolled extra-high-strength steel, BS960QC, has been comprehensively investigated. Analysis has been made on the weldability ,the different welding procedures ,the mechanical properties, and the fatigue properties, and a set of recommendation guidelines have been proposed for evaluating the welded joints of the extra-high-strength steel. The research and results indicate that the hot-rolled extra-high-strength steel, BS960QC,has good weldability and an excellent adaptability to welding procedures. Further,the excellent mechanical properties and fatigue properties of the welded joints ,which can be achieved by using optimized welding procedures, can completely meet the technical requirements of the construction machinery industry.

Transverse thickness difference control technology for non-oriented silicon steel

Transverse thickness difference is an important quality index of non-oriented silicon steel strips. In order to fulfill users＇ accuracy requirements on the transverse thickness of silicon steel and improve the production yield, the factors influencing transverse thickness difference were analyzed. Then the work roll shape, control strategy and incoming hot-rolled strips were optimized. Since the optimization measures were implemented in the actual production, the thickness difference of non-oriented silicon steel has been reduced greatly and fulfilled the requirements placed by users. These measures have achieved remarkable effects.

Effect of the solidification structure on the ridging and drawability of ultra low carbon ferritic stainless steel

In order to understand the effect of the solidification structure on the formability of ultra low carbon ferritic stainless steel （FSS） ,this work studies the ridging phenomenon and the deep-drawing property in detail and the research method was X-ray diffraction （XRD） and scanning electron microscope （SEM） technique. The result shows that the columnar grain specimen had a higher ridging height than the equiaxed grain specimen, which was mainly attributed to the formation of grain colonies in the columnar grain specimen. After final recrystallization annealing, the equiaxed grain specimen obtained a high-intensity T-fiber texture and an excellent deep-drawing property.

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.

Inclusion control of automotive spring steel in the basic oxygen furnace and ingot casting process

The process of automotive spring steel in the basic oxygen furnace and ingot casting （BOF-IC） of Baosteel is described in this paper. High quality spring steel can be obtained through designing reasonable deoxidization and alloying processes ,enhancing steel purity and reducing inclusions in steel.