最新刊期
卷 45 ， 期 3 ， 2024
- 摘要：Based on the current quality situation of ESR bearing steel for passenger railway and wagons in China， the grade 8620 steel bars with diameters between 60 mm and 120 mm are produced with the process as follows： 70 t EAF（Hot Metal+Scrap）→LF→RH→3 t steel ingot→soaking pit →1350+750/650 rolling mill， whose chemical composition are（%）： 0.18-0.22 C，0.15-0.30 Si，0.75-0.95 Mn，0.45-0.65 Cr，0.45-0.70 Ni，0.15-0.25 Mo，≤0.020 P，≤0.015 S，0.020-0.050 Al. By taking technological measures such as steel and slag retention operation，slag formation and alloy addition during tapping， vacuum holding time ≥25 min and soft argon blowing， superheat control， full process Argon protection casting and automatic pouring as well as controlling cooling after rolling etc， to keep 8620 steel bars conform to all technical specification requirements， especially， macro-inclusions of finished bars less than 10 mm/dm³， grain size class 8-8.5， and the density being 7.854 g/cm³.关键词：3 t Steel Ingot;Grade 8620 Steel;Automatic Ingot Casting， Macro-inclusion;Density3|1|0更新时间：2025-05-09
- 摘要：Austenitic stainless steel for nuclear power plant reactor internals is extremely strict in terms of purity， grain size， corrosion resistance and mechanical properties， and stable quality materials are crucial to the safe operation of nuclear power plants. By setting a reasonable chemical composition（mass fraction） target value for 316 stainless steel， namely w［C］ 0.045%， w［N］ 0.06%， w［Cr］ 17.00%， w［Mo］ 2.50%， w［Ni］ 12.50， w［Mn］ 1.80%； Three dimensional pre-melting and remelting smelting is used to improve the purity of molten steel， and low melting speed is set to reduce smelting segregation. Combine forging and rolling； control the consolidation insulation time according to material specifications and accurately control the cold drawing deformation at 2 mm.The austenitic stainless steel SA-479 316 （N-60-6） cold-drawn bar for reactor internals has been successfully developed. Its non-metallic inclusions A， B， C and D are all ≤1.0 grade， grain size reaches grade 5， intergranular corrosion qualified， room temperature yield strength 479-545 MPa， high temperature tensile strength 515-575 MPa at 350 ℃， meeting the requirements for the use of cold drawn bars for in-stack components.关键词：Reactor Internals;Austenitic Stainless Steel;Cold Drawn Bars;Mechanical Property3|1|0更新时间：2025-05-09
- 摘要：The strength and plasticity of 10B38 boron containing cold heading steel under different high temperature conditions were studied using high-temperature tensile testing method. The results showed that the tensile strength decreased significantly from 124.8 MPa to 22.9 MPa at temperatures ranging from 700 to 950 ℃； At 950 to 1 150 ℃， the tensile strength was 12.7 to 25.5 MPa. In terms of thermoplastic properties， the cross-sectional shrinkage rate at 700-750 ℃ was 56%-72%； When the temperature was between 800 and 1 050 ℃， the cross-sectional shrinkage rate was ≥ 75%； When the temperature was between 1 050 and 1 150 ℃， the cross-sectional shrinkage rate was greater than 65%. Based on the above experimental data， the strength of the secondary cooling water in continuous casting was optimized from a specific water content of 1.35 L/kg to a specific water content of 1.25 L/kg. After optimization， the crack index of the continuous casting slab was significantly reduced. The dynamic CCT curves of 10B38 boron containing cold heading steel were measured， The experimental results showed that when the cooling rate was 0.2-1 ℃/s， the test steel was mainly composed of softer ferrite structure； When the cooling rate was 3-10 ℃/s， the experimental steel was mainly composed of pearlite structure； When the cooling rate was 20 ℃/s and 30 ℃/s， the structure of the test steel was flat noodles martensite+pearlite； When the cooling rate was 50 ℃/s， a complete martensitic structure was formed at room temperature. The experimental results showed that by reducing the cooling rate to 0.5-2 ℃/s， ideal ferrite and pearlite hot-rolled structures can be obtained.关键词：10B38 Cold Heading Steel;High-temperature Tensile;CCT Curves5|0|0更新时间：2025-05-09
Product Research and Development
- 摘要：Four as-cast high carbon chromium bearing steels with different Si contents （0.29%、0.42%、0.71% and 1.50%）were prepared using a vacuum induction furnace， the carbides in the steel were extracted by nonaqueous solution electrolysis method. The two-dimensional and three-dimensional morphology of carbides in steel was observed through scanning electron microscopy. the types of carbides at different Si contents were investigated by X-ray diffractometer， the essential mechanism of influence of Si content on cementite type was determined by thermodynamics and first principles calculation. The research results indicate that there are two types of carbides in as-cast high carbon chromium bearing steel with different Si contents， namely layer cementite （Fe1-XMnX）3C and grain boundary carbides M23C6. With the increase of Si content （0.29%-1.50%）， the M23C6 grain boundary carbides change from a continuous coarse rod-shaped structure to a discontinuous fine point like structure， which indicate that the increase of Si content has an inhibitory effect on the precipitation of grain boundary carbides. In addition， the increase in Si content reduces the proportion of Mn in （Fe1-XMnX）3C cementite， and the transformation trend of cementite type is from Fe1.8Mn1.2C to Fe3Mn0C. The possible reason is that during the precipitation process of cementite formation， Si atoms are discharged into area around cementite to form a Si rich micro zone， which hinders the diffusion of Mn atoms from the matrix to the cementite， reduces the activity and diffusion migration ability of Mn in the matrix. Thus， the relative content of Mn in the cementite is reduced.关键词：High Carbon Chromium Bearing Steel;Cementite;Si Content;Thermodynamic Calculations;First Principles2|0|0更新时间：2025-05-09
- 摘要：The effects of slit width and flow rate on the size， quantity， velocity and force of bubbles are analyzed by establishing an experimental platform of bottom blown metal molten pool water model and using high-speed photography and image processing methods. The mixing condition of the solution was reflected by measuring the change of the electrical conductivity in the solution， so as to determine the stirring intensity of the solution by the structure and parameters of the bottom blowing. The results show that the bubble movement is mainly affected by the buoyancy and drag force， and the Sauter diameter of the bubble increases with the increase of the slit width and the bottom blowing flow rate. The larger the bubble， the more favorable the stirring of the solution and the shortening of the mixing time， while the change trend of the bubble number is opposite. The rising speed of the bubble is proportional to the bottom blowing flow rate and inversely proportional to the slit width. The experiment results show that when the slit width is 0.30 mm and the bottom blowing flow rate is 1.00 L/min， the mixing uniform time is the shortest.关键词：Water Model Experiment;Slit Width;Bottom Blow Flow Rate;Bubble Motion;Mixing Uniform Time2|0|0更新时间：2025-05-09
- 摘要：The converter smelting process contains complex multi-phase and high-temperature physical and chemical reactions， and it is of great significance to establish a reliable converter endpoint prediction model to effectively reduce the fluctuation of molten steel composition and improve the quality of steel. Based on the actual production data of a 200 t converter in a steel mill， the particle swarm optimization algorithm is used to select the optimal penalty parameter C and kernel parameter g of the support vector machine model to establish a prediction model， and the carbon mass fraction and temperature at the end point of the converter are predicted. After data processing 425 sets of data were obtained and divided into training set data and test set data， and normalized them， of which 50 groups were randomly selected as test set data.The results show that the accuracy of carbon mass fraction （error ±0.015%） and temperature （error ±15 ℃） is 81.8% and 80% respectively. Compared with BP neural network model and RBF model， support vector machine model optimized by particle swarm optimization has higher accuracy and better generalization ability.关键词：Converter Steelmaking;PSO-SVM Model;Endpoint Temperature;End-point Carbon Content;Predictive Models2|0|0更新时间：2025-05-09
- 摘要：The effects of La-Ce rare earth treatment on inclusions， continuous casting castability and steel properties of Q345D structural steel were analyzed by field test. The results showed that the alloy yield of RE in Q345D structural steel was 21.5%. Compared with the heats without RE addition， the desulfurization rate increased by 37.5%， and the unit inclusion density decreased from 80.16/mm2 to 60.78/mm2. The inclusions in molten steel before La-Ce rare earth treatment were mainly MgO-Al2O3-CaO composite inclusions. The modification effect of La-Ce rare earth treatment on small size （ D≤5 μm ） inclusions was more obvious. Small size inclusions were modified into （La-Ce-S） and （La-Ce-Al-S-O） rare earth inclusions. La-Ce rare earth treatment can significantly reduce the aspect ratio of MnS inclusions in steel， so that the morphology of MnS inclusions after rolling was closer to ellipse without long linear， which was the main reason for the increase of transverse impact energy of Q345D structural steel by 20%.关键词：La-Ce Rare Earth Treatment;Q345D Structural Steel;Transverse Impact Energy;Inclusion Modification;Refine;Cleanliness223|17|0更新时间：2025-05-09
Smelting and Solidification
- 摘要：Aiming at the problem of poor low-temperature impact toughness of titanium microalloyed high-strength steel CGLC700， by thermodynamic calculations and high-temperature in-situ observations， as well as the use of electron backscattering diffraction， transmission electron microscopy， scanning electron microscopy， and optical microscopy have been used to investigate inclusions， second-phase particles， fracture morphology， and low-temperature impact toughness of the Ti-bearing high-strength steel. The results show that the reasons for the poor low-temperature impact toughness of Ti-bearing high-strength steel are related to the large-size brittle inclusions and the precipitation phase of Ti（C，N） and TiN in the steel. When the nitrogen content in steel is reduced from 0.004 9% to ≤0.003 5%， the number and size of brittle inclusions in steel can be effectively reduced， and the impact toughness of steel can be improved. Reducing the final rolling temperature from 885-895 ℃ to 875-885 °C can promote the precipitation of nanoscale TiC second phase particles and the formation of large-angle grain boundaries， and reduce the effective grain size， thereby significantly improving the low-temperature impact toughness of steel. Compared with experimental steel 1#， when the nitrogen content was reduced to ≤0.003 5% and the final rolling temperature was 875-885 °C， the average grain size in titanium microalloyed high-strength steel decreased from 3.1 μm to 2.7 μm， the proportion of small-size effective grains was higher， the large-size inclusions and number density decreased， the proportion in the large-angle grain boundary increased by 16.6%， and the low-temperature impact energy of steel could be increased from 14.75 J to 37.35 J.关键词：Titanium Microalloyed High Strength Steel CGLC700;Inclusions;Second Phase Particles;Low-temperature Impact Toughness;Nitrogen Content;Final Rolling Temperature2|0|0更新时间：2025-05-09
- 摘要：This study focuses on the investigation of the mechanical properties and corrosion resistance of 430 ferritic stainless steel with an addition of 0.30% Sn， by incorporating varying amounts of Cu into the experimental steel. The results of room temperature and high temperature tensile tests reveal that Cu atoms act as solid solution strengtheners in the matrix， enhancing the tensile strength of the stainless steel. However， the formation of a significant amount of Cu-rich phase at grain boundaries leads to a decrease in the steel's plasticity. The uniform corrosion resistance of the steel initially increases and then decreases with increasing Cu content， reaching the highest effectiveness at 0.45% Cu. Similarly， Cu exhibits a comparable pattern in its resistance to intergranular corrosion in the experimental steel， achieving the best outcomes at a content of 0.98% Cu.关键词：Tin;Copper;Ferritic Stainless Steel;Mechanical Properties;Corrosion Resistance4|0|0更新时间：2025-05-09
- 摘要：Thermal compression test of C630R rotor steel was carried out by Gleeble-3800 thermal simulation testing machine at temperature range of 1 000-1 200 ℃ and strain rate of 0.01-1 s-1， the thermal deformation behavior and the influence of different process parameters on the microstructure were studied， the constitutive equation and hot processing map of the C630R rotor steel at true strain of 0.8 was constructed. The experimental results indicate that the true stress of the C630R rotor steel decreases with the enhancement of deformation temperatures to 1 200 ℃ and the reduction of true strain rate to 0.01 s-1. When the deformation temperature is higher and the compression strain rate is lower， C630R rotor steel is preferred to produce dynamic recrystallization. Thermal deformation activation energy Q of the C630R rotor steel is calculated to be 530.155 kJ/mol by using the corrected flow stress curves， and the constitutive equation is
- 摘要：In order to resolve the cracking problem of 436L ferritic stainless steel heat exchanger plates during stamping forming， the forming characteristics of two typical corrugated structure heat exchange plate were studied through Dynaform numerical simulation analysis and stamping forming experiments， the evolution of forming limit and thinning rate during the forming process was analyzed， and the influence of plate thickness and corrugation parameters （corrugation pitch） on crack location and degree of cracking was studied. Additionally， the impact of corrugation pitch on thinning rate was also discussed. The results indicate that the cracking and thinning of 436L ferritic stainless steel heat exchanger plates are both affected by plate thickness and corrugation parameters. For shallow corrugated heat exchanger plates （corrugation depth of 2 mm）， the vulnerable area for cracking is the top of the corrugation’s rounded corner. Increasing the plate thickness significantly affects the tendency for cracking and thinning rate， with a decrease of approximately 2.6% in the maximum thinning rate at the rounded corner for every 0.1 mm increase in plate thickness. At this point， the maximum safe thinning rate for forming is 18.9%， and the minimum forming plate thickness is 0.6 mm. For deep corrugated heat exchanger plates （corrugation depth of 2.6 mm）， the vulnerable areas for cracking are the sides of the corrugation’s rounded corner and the top of the rounded corner. Increasing the plate thickness has a smaller impact on the tendency for cracking and thinning rate， with only a decrease of approximately 1.4% in the maximum thinning rate at the rounded corner for every 0.1 mm increase in plate thickness. To ensure that the quality requirements for forming are met， it is necessary to increase the normal pitch of the corrugation.关键词：Plate Heat Exchanger;Heat Exchanger Plate;436L Ferritic Stainless Steel;Numerical Simulation;Thinning Rate2|0|0更新时间：2025-05-09
- 摘要：To meet the use needs of LNG fuel tanks and storage tanks， the key process control of steel-making and rolling of 9Ni steel were carried， and the influence of two-phase area heat-treatment processes and Nb microalloying on microstructure and properties of 9Ni steel was studied. The results show that with the increase of intercritical quenching （IQ） temperature， the Yield stress（YS）， tensile strength （TS） and the ratio between YS and TS （Y/T） decreases firstly， then increases. Subsequently as the tempering temperature increases， the YS and TS gradually decrease， while the elongation increases； When the tempering temperature is 600 ℃， the YS and TS reach their lowest values， and the elongation （EL） reaches its peak. The microstructure after intercritical quenching presents distribution of large and small grains， which contributes to the reduction of Y/T ratio of steel plate. The microstructure of Nb micro-alloyed 9Ni steel plate is mainly composed of tempered sorbite structure and 3% -8% reverse austenite. The addition of 0.015% Nb increases the average YS and TS of 9Ni steel by about 50 MPa and 40 MPa， respectively. The impact absorption energy increases by about 40 J tested at -196 ℃.关键词：LNG;Nb Micro-alloyed;9Ni Steel;Tempering Sorbite3|0|0更新时间：2025-05-09
- 摘要：In order to investigate the microstructure uniformity and plasticity of hot-rolled 0Cr21A16 alloy sheet and improve its high temperature and cold working characteristics， heat treatment tests and microstructure properties analysis were carried out at different temperatures. The microstructure and mechanical properties of 0Cr21Al6 alloy sheet before and after heat treatment were studied by optical microscopy， X-ray diffraction （XRD）， Gleeble high temperature thermal tensile test， scanning electron microscopy （SEM） and nanoindentation. The results show that the microstructure uniformity of 0Cr21Al6 alloy sheet can be improved by heat treatment， and the average grain size is about 42 μm after holding at 960 ℃ for 6 min 40 s， and the overall grain size is relatively uniform and fine compared with at 940、980、1 000、1 020 ℃ heat treatment， the hardness and plasticity are the best combination， and the fracture toughness KIC is the best after 960 ℃ heat treatment. With the best comprehensive performance， it can effectively avoid the brittle fracture of materials in the production process. In addition， Gleeble test shows that the heat treatment temperature over 1 000 ℃ is no longer suitable for hot processing.关键词：FeCrAl Alloy;0Cr21Al6 Steel;Hot Rolled Sheet;Heat Treatment;Microstructure;Mechanical Properties2|0|0更新时间：2025-05-09
- 摘要：The effects of aging rolling temperature （150， 200， 250， 300 ℃） on microstructure ， texture and magnetic properties of low-temperature grain-oriented silicon steel were studied by aging rolling experiment at different temperatures for 5 min. The results show that the aging rolling temperatures has no obvious effect on the microstructure morphology of cold rolling and primary recrystallization of low-temperature grain-oriented silicon steel. However， the contents of ｛111｝<112> and Goss in the primary recrystallization microstructure increased and then decreased with the increase of aging rolling temperature， and with the highest contents at 200 ℃ for ｛111｝<112> texture， while at 250 ℃ for Goss texture. And the proportion of primary recrystallization texture of ｛411｝<148> and ｛100｝<012> is relatively low. The increase of Goss and ｛111｝<112> texture and the decrease of ｛100｝<012> texture in the primary recrystallization microstructure resulted in perfect secondary recrystallization of the sample during high temperature annealing. After high temperature annealing， there were fewer fine grains and island grains， and the final sheets had excellent magnetic properties.关键词：Aging Rolling;Grain-oriented Silicon Steel;Microstructure;Texture;Magnetic Properties3|0|0更新时间：2025-05-09
- 摘要：The continuous cooling transformation of 12Cr1MoV perlitic heat-resistant steel was studied by means of thermal expansion tester， laser confocal microscope， microhardness tester and scanning electron microscope， the continuous cooling transformation （CCT） curve of experimental steel was drawn， and the effect of cooling rate on the microstructure evolution of phase transformation during cooling process was analyzed. The results show that four transition regions of ferrite， pearlite， bainite and martensite will appear in the CCT curves of 12Cr1MoV steel at the cooling rates between 0.5 ℃/s and 30 ℃/s. At the cooling rates between 0.5 ℃/s and 1 ℃/s， and the transformation products are composed of ferrite and pearlite. At the cooling rates between 1.5 ℃/s and 10 ℃/s， and the transition products are mainly composed of upper bainite and ferrite. At the cooling rates between 10 ℃/s and 20 ℃/s， and the transition products are mainly the mixed structure of upper bainite， lower bainite and martensite. At the cooling rate of 30 ℃/s， the transition product is mainly martensite. The transition structure of undercooled austenite appears upper bainite at the cooling rates between 1.5 ℃/s and 20 ℃/s. The appearance of upper bainite in the structure leads to a decrease in the mechanical properties of the steel， which is prone to crack formation and propagation. Based on the above research results， measures to reduce the cooling rate of 12Cr1MoV steel continuous casting billets and hot rolling lines are proposed to reduce the upper bainite structure The surface cracks of the bars are effectively controlled after adjustment.关键词：12Cr1MoV Steel;Cooling Rate;CCT curve;Microstructure3|0|0更新时间：2025-05-09
- 摘要：The continuous cooling expansion curve of 18CrNiMo7-6 wind power steel was tested by using a Gleeble-3800 thermal simulator at a cooling rate of 0.1-30 ℃/s. The static continuous cooling transformation curve （CCT curve） of 18CrNiMo7-6 wind power steel was plotted by using metallographic hardness method. The microstructure transformation law of 18CrNiMo7-6 wind power steel under different cooling rate conditions was analyzed. The experimental results show that the Ac1 phase transition temperature of 18CrNiMo7-6 wind power steel is 765 ℃， and the Ac3 phase transition temperature is 843 ℃. When the cooling rate is less than 0.5 ℃/s， the microstructure of the experimental steel is ferrite and pearlite， and high-temperature phase transformation occurs； At a cooling rate of 0.5-1 ℃/s， ferrite disappears and plate-like martensite is initially formed； Starting from 2 ℃/s， the microstructure is mainly bainite and martensite， with both medium temperature and low temperature phase transformations occurring simultaneously； After 10 ℃/s， the bainite content decreases and the martensite content increases with the increase of cooling rate； When the cooling rate is greater than 20 ℃/s， the microstructure is entirely martensitic with only low-temperature phase transformation occurring； During the process of increasing the cooling rate from 0.1 ℃/s to 30 ℃/s， the hardness of the wind power steel shows an upward trend.关键词：18CrNiMo7-6;Continuous Cooling Transformation Curve;Microstructure;Hardness6|0|0更新时间：2025-05-09
Forming and Phase Transition
- 摘要：The service performance of welded parts is directly impacted by the microstructure of the Inconel718 welded joint； however， there is a lack of comprehensive research on the impact of the Mn element on the microstructure and performance of the welded junction. In this study， the solid-solution Inconel718 hot-rolled plates with varied Mn concentrations of <0.01%， 0.24%， and 0.34% were joined by using DC pulse arc welding before two stages of thermal aging. The tensile test of these plates was performed at room temperature to determine the impact of Mn content on the microstructure and aging mechanical properties of welded joints. The results demonstrate that there are only the Laves phase and no δ phase in the welded joints with three different Mn concentrations. The volume proportion of Laves phase precipitates in the welded joints significantly increases as the Mn content rises from ＜0.01% to 0.34%. However， the content of Laves phases decreases slightly， and γ΄΄ begins to precipitate after a two-stage thermal aging treatment. In addition， the tensile strength and elongation of the welded joint are inferior to those of the aged base metal. The tensile properties of the aged welded joints are worsened by the increase in Mn content， causing a decrease in tensile strength from 1 250 MPa to 1 178 MPa and 1 213 MPa， respectively. The three welded joints are broken at the welded areas in the tensile test， all of which are ductile fractures.关键词：Inconel718 Alloy;Mn Content;Laves Phase;Welding Performance;Plate2|0|0更新时间：2025-05-09
- 摘要：The flexible bearing steel with long fatigue life using for robot harmonic speed reducer has been successfully developed by applying EAF process technology. The ratio of scrap to hot metal was controlled more than 80%. This paper compared the metallurgical quality of flexible bearings and traditional rolling bearings in terms of non-metallic inclusions， austenite grain size and carbide banding structure， the fatigue strength of steel used for flexible bearing and traditional rolling bearing under 107 cycles was tested by the method of rotary bending fatigue test. The O content of steel used for flexible bearings of robot harmonic reducer was less than 0.000 4%， the Ti content was much less than 0.001%， non-metal inclusions of class A sulfide≤1.0 grade， non-metal inclusions of class B and D oxide ≤0.5 grade. The size of the maximum spherical inclusion was less than 30 μm. The test results show that the flexible bearings have ultra-high purity. By increasing Al and N chemical composition in the smelting process， the austenite grain size was 10 grade in the flexible bearing steel， much higher than 8.5 grade in the traditional rolling bearing steel. The proportion of carbide banding structure of 7.1 and 7.2 grade was higher than that of traditional bearing steel in the means of extending the high temperature diffusion time. The ultra-high austenite grain size and the decrease of the width of carbide banding structure showed that the flexible bearing steel had an ultra-high structure uniformity. In addition， the rotary bending fatigue strength of the flexible bearing steels was 1 016 MPa， its fatigue life was slightly higher than that of the traditional rolling bearing steels.关键词：Harmonic Speed Reducer;Flexible Bearing Steel;Grain Size;Non-metallic Inclusions;Rotary Bending Fatigue;Ultra-high Cycle Fatigue2|1|0更新时间：2025-05-09
- 摘要：According to the abnormal fracture phenomenon of 87MnSi steel wire rod for bridge cable， the evolution of microstructure and mechanical properties during production processing were systematically analyzed. The results show that the microstructure of the rod is composed of pearlite and a small amount of proeutectoid ferrite， and the cementite lamellae are randomly distributed. After cold drawing， the cementite lamellae are rotated or fibrotic， and some cementite are broken and dissolved， the dissolution amount is 1.40wt.%（9.69%）. After ho-dip galvanizing， the dissolved cementite is spheroidized. In the process of cold drawing， hot-dip galvanizing and stabilization treatment， the microhardness of wire rod （329.8HV） increases （450.2HV） firstly， then decreases （447.9HV） and increases （474.8HV） finally. The cementite dissolved in the cold drawing process increases the hardness of the steel wire to 468.3HV， while the spheroidized cementite in the hot galvanizing process decreases the hardness to 439.8HV， and deteriorates tensile property. When the degree of spheroidization of cementite on the edge is obvious， the microstructure and mechanical properties of the steel wire inside and outside are greatly different， and the fracture is eventually caused by uneven force during stabilizing treatment.关键词：Bridge Cable;87MnSi Steel;Hot-dip Galvanizing;Stabilizing Treatment;Fracture;Cementite Spheroidization125|3|0更新时间：2025-05-09
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