最新刊期
卷 45 ， 期 1 ， 2024
- 摘要：In the steel industry is facing the new normal situation of transformation and upgrading， with the help of intelligent equipment to drive the steel industry to green and high-end development is expected to achieve the optimization of the steel production organization. Continuous casting tundish with constant temperature and low superheat can effectively improve the quality of steel， so it is necessary to develop the heating technology of tundish. Therefore， tundish heating temperature control technology has been paid more and more attention.Regarding to the hot issues of tundish plasma heating technology， which has attracted increasing attention in recent years， systematically describes the heating principle and equipment characteristics， introduces the research and development of equipment and metallurgical functions of plasma heating technology at home and abroad， and mainly analyzes the influence of plasma heating technology on the flow field， temperature field， inclusion removal and chemical composition of steel liquefication in tundish， and the metallurgical effect of practical application. Based on the deep understanding of the research and application of plasma heating technology， the new problems found in the heating process of a new type of hollow graphite electrode plasma equipment independently developed in China are discussed， and the ways to further improve its metallurgical effect are discussed. Analysis indicates that the domestically developed hollow graphite electrode plasma heating equipment is better suited to meet the transformation needs of China's steel industry. This equipment provides an effective solution to issues such as the instability of superheat in casting steel， lower cleanliness levels in molten steel， and uneven composition of molten steel. It addresses the shortcomings in the intelligent positioning of the "one-key heating" intermediate package， thus enhancing its precision.关键词：Continuous Casting;Tundish;Plasma Heating;Flow Field;Temperature Field;Inclusion Removal3|1|0更新时间：2025-05-09
Overview
- 摘要：The increasing service temperature of aero-engine turbine discs makes more stringent requirements for oxidation resistance of the materials. U720Li alloy is a high-strength nickel-based superalloy for turbine discs with a long-term service temperature up to 750 ℃. Clarifying the oxidation behavior at service temperatures of this alloy is of great significance for improving the service life of high-performance turbine discs. In this paper， the oxidation kinetics curve of forged U720Li alloy at 750 ℃ has been determined by the static weight gain method， and the oxide film morphology， structure and element distribution in different oxidation stages were analyzed by XRD and SEM-EDS. The results show that the U720Li alloy has excellent oxidation resistance at its service temperature， and its isothermal oxidation kinetic curve at 750 ℃ basically follows the cubic law， reaching the full anti-oxidant level. It has been analyzed that the loose γ-Cr2O3 is generated at the early oxidation stage of U720Li alloy. The γ-Cr2O3 layer spalls continuously as the oxidation proceeds， and the oxide film becomes more continuous and dense and forms a complex multilayer structure. Meanwhile， a γ´ depleted layer is gradually formed within the matrix nearby the oxide film. In the stable oxidation stage， the oxide film becomes more continuous and dense， forming a regular double-layer structure which includes the dense α-Cr2O3 outer layer and α-Al2O3 inner layer. The formation of continuous dense α-Cr2O3 and α-Al2O3 layers can effectively prevent the internal diffusion of oxygen and external diffusion of alloying elements， which guarantees the excellent oxidation resistance of U720Li alloy.关键词：U720Li Alloy;Oxidation Behavior;Oxide Film;γ´ Depleted Layer;Service Temperature4|1|0更新时间：2025-05-09
- 摘要：With the improvement of the quality and performance requirements of duplex stainless steel （DSS） in the industry， secondary austenite （γ2） has become one of the key factors affecting the application of S32750 DSS. Secondary austenite is considered as the joint product of temperature and cooling rates， which performed near K-S or N-W orientation relationship with the ferrite phase and an enrichment for N elements .Secondary austenite can be divided into needle-shaped austenite （NA） and isolated austenite （IA） by morphology. In this paper， the effect of N mass fraction on the precipitation behavior of secondary austenite was studied by preparing test steels with N content of 0.02%， 0.09% and 0.17%. Thermal-Calc simulation and EBSD detection proved that with the increase of N， γ2 evolved from curved feather-shape to needled-shape with the total proportion of austenite phase increased. The precipitation mode of austenite related to the Gibbs free energy， which was namely affected by elements composition and temperature.关键词：Duplex Stainless Steel;Secondary Austenite;Nitrogen Mass Fraction;Precipitation Behavior;Nuclear Driving Forces3|0|0更新时间：2025-05-09
- 摘要：Grade 8.8 non-quenched and tempered fastener hot rolled wire rod based on 10B21 steel was test produced by means of converter → refining furnace → vacuum degassing → square billet continuous casting → heating → rough rolling → medium rolling → finishing rolling → diameter reduction → spinning → XDWP （Xingcheng Direct Water Patenting） cooling → Stelmor air cooling . By controlling the reducing diameter temperature to 813 ℃， the spinning temperature to 828 ℃， and the Stelmor roller table rate to 0.75 m/s， the tensile strength of the hot rolled wire rod reached 680 MPa， the total elongation to 23.6%， section shrinkage to 75%， after continuous XDWP cooling and Stelmor air cooling. Mechanical properties fully met the requirements of GB/T29087―2012. After 1/4 cold top forging and 25% drawing test of large reduction rate， the results met the requirements of fastener users.关键词：8.8 Grade Non-quenched and Tempered Fastener;10B21 Steel;XDWP;Bainite194|5|0更新时间：2025-05-09
- 摘要：This article presents the smelting practice of 9Ni steel for ultra-low-temperature pressure vessel in a certain steel plant by the "BOF → LF → scraping slag/fetching slag → LF → VD → CC" process. The decarburization and desulfurization in the BOF + LF process require that the steel produced by the converter has a low phosphorus （w［P］） ≤ 0.009%） and carbon content （w［C］） ≤ 0.05%）， with an average desulfurization rate of 74.3% and an average decarburization rate of 51.2%. The control of phosphorus content is more difficult than carbon content in the production process. In the scraping slag process， the average phosphorus reversion rate in the molten steel is 16.89%， while in the fetching slag process， it is 22.61%. Although the scraping slag process results in a lower phosphorus reversion rate in the molten steel， the processing time is increased by 15 to 20 minutes， and the average molten steel loss is increased by 3.1 t per heat. After adjusting the addition of nickel plates from the converter to the ladle furnace， the average nickel recovery rate increases by 3.74%. Through optimizing the production process， the molten steel in the tundish meets internal control requirements for phosphorus（ P）， sulfur （S）， nitrogen N， total oxygen （T.O）， and carbon （C）， ensuring high purity of the molten steel， the macrostructure center segregation of the cast slab reaches 1.0～1.5 grade in class C， the internal and surface quality of the cast slab are good. The rolled steel plate exhibits excellent performance at -196 ℃.关键词：9Ni Steel， Dephosphorization;Decarbonization;Scraping slag;Fetching Slag3|1|0更新时间：2025-05-09
Product Research and Development
- 摘要：Low nitrogen content can control the formation of TiN inclusions， thereby improving the metallurgical quality and comprehensive performance of nickel based high-temperature alloys. This article first compared the differences between the standard Gibbs free energy and the interaction coefficient of alloy elements with N， Ti activity in nickel based and iron based metal liquids， it pointed out that two different sets of thermodynamic data from nickel based and iron based metal liquids cannot be mixed.The thermodynamic model for nitrogen removal of IN718 alloy was established based on the existing thermodynamic parameters of nickel based alloys. It was found that reducing temperature and increasing vacuum degree to reduce nitrogen partial pressure while meeting other smelting conditions are the direct means to reduce nitrogen content in the alloy liquid. The addition of different alloying elements has different effects on nitrogen removal. At the same time， the thermodynamic model and segregation model for TiN precipitation were established， and the calculation results showed that under the production temperature of IN718 at 1 450 ℃， the ［N］ content in the alloy liquid was controlled below 43.69×10-6， the solute elements N and Ti are enriched and precipitated in the liquid phase during solidification. The calculated precipitation temperature is 1 468 K， and the solid fraction
- 摘要：One of the important requirements for converter steelmaking is to accurately calculate the amount of lime added based on the conditions of hot metal and the requirements of molten steel， in order to avoid waste of flux. However， due to the fast pace of converter production and multiple influencing factors， it is difficult to accurately determine the amount of lime added. In order to accurately calculate the amount of converter lime， avoid lime waste and reduce unnecessary steelmaking cost， mechanism model， classification model and multiple linear regression model are established to calculate the amount of converter lime. Compared with the three models， the pure mechanism model has low calculation accuracy and is difficult to be directly applied to field production. According to the classification model optimized by mechanism model， only 60% of the furnace times difference is less than 500 kg/ furnace. A multiple linear regression model is established using SPSS， and the relationship between lime addition amount and other parameters is obtained WLime=4 147.24×wTSi+529.67×wTC+60.20×Wqf+0.405×VO-1 833.95. The verification results show that， 93% of the calculated difference of the furnace is less than 400 kg/ furnace， 77% of the calculated difference of the furnace is less than 300 kg/ furnace， which can basically meet the requirements of field use. After the model is applied in the field， the amount of lime added is effectively reduced.关键词：Converter;Lime;Mechanism Model;Multiple Linear Regression Model;Accuracy3|0|0更新时间：2025-05-09
- 摘要：The element content， phase composition and interface reaction of nozzle clogging for titanium-bearing welding wire steel SJ-60 during continuous casting were analyzed by means of XRF， XRD and SEM. It is found that the interface of the nozzle is rough and porous due to decarburization reaction， which causes nozzle to be easily invaded by high melting point phases. In addition， the calcium treatment and erosion of refractory during the refining process will produce a large amount of CaTiO3 and MgAl2O4 in the molten steel， and the deposition of both at the interface of the nozzle is the main cause of nozzle clogging. The practice has shown that replacing ordinary ferrosilicon with low titanium and low aluminum ferrosilicon can reduce the aluminum content in steel from 0.008 0%~0.009 5% to 0.005 0%~0.006 5%， which is beneficial for reducing the content of Al2O3 inclusions in steel. Cancelling the refining calcium treatment can reduce the calcium content in steel from more than 0.001 4% to less than 0.000 5%， which is beneficial for reducing the content of CaTiO3 inclusions in steel. Reducing the amount of fluorite from 0.8~1.0 kg/t to 0.3~0.5 kg/t can reduce the erosion of refractory， and the magnesium oxide content in slag is decreased from more than 10% to less than 5%， which is beneficial for reducing the content of MgAl2O4 inclusions in steel. Through the above measures， the problem of nozzle clogging caused by CaTiO3 and MgAl2O4 has been effectively solved，and the number of continuous casting heats is increased from 4-5 heats to more than 12 heats.关键词：Titanium-Bearing Welding Wire Steel;Nozzle Clogging;Calcium Titanate;Spinel;Titanium Nitride3|0|0更新时间：2025-05-09
- 摘要：In this paper， one 180 t double-hole bottom argon blowing ladle is taken as the research object. Based on the specific production conditions， six modes of argon bottom blowing in ladle are numerically simulated， and combined with the field test， it is compared with the argon blowing mode currently adopted. The results show that： （1） The mixing time of molten steel decreases with the increase of argon blowing amount. When argon blowing amount is constant， the argon blowing mode with differential flow rate is stronger than that with constant flow rate. （2） Different modes of argon blowing at the bottom of ladle have different locations and areas of slag holes. When the total flow rate is constant， the maximum velocity of molten steel surface in the differential flow argon blowing mode is greater than that in the constant flow argon blowing mode， which is easy to cause slag entrapment. （3） The fluctuation of slag layer thickness at the slag line in differential flow argon blowing mode is greater than that in constant flow argon blowing mode， and the greater the flow difference， the more severe the fluctuation. （4） The differential flow argon blowing mode further strengthens the refining effect of molten steel by argon blowing at the bottom of ladle through the cooperation of "strong-weak" streams. And the industrial test shows that the number of larger inclusions in steel is obviously more than that in argon blowing mode （400 L/min—600 L/min） with constant flow rate （500 L/min—-500 L/min）.关键词：Ladle Argon Blowing;Numerical Simulation;Mixing Time;Slag Eye3|0|0更新时间：2025-05-09
- 摘要：The evolution of inclusions in molten steel in tundish before and after vacuum treatment during the production of GCr15 bearing steel in a steel plant is analyzed， the results showed that total oxygen content in molten steel increased greatly in tundish. Magnesium aluminum Spinel inclusions increased in RH soft blowing and tundish to varying degrees， and the number increased significantly in tundish. The MgO aggregate particles in the working layer of the tundish coating are greatly reduced， and some MgO particles are dissolved in the molten steel， resulting in the increase of oxygen content in the molten steel.The effect of different SiO2 content on the phase of tundish coating was discussed by thermodynamic simulation analysis. It was proposed that the control of SiO2 content at range 4%~6% and the strengthening of tundish masonry management can reduce the formation of high temperature low melting phase in tundish coating and effectively improve the flaw detection eligibility rate of bearing steel GCr15 head slab.关键词：GCr15 Bearing Steel;Inclusions;Tundish Coating;Erosion4|1|0更新时间：2025-05-09
- 摘要：This article analyzes the causes of flocculent flow in the continuous casting process of low-carbon， low sulfur， and low oxygen aluminum killed steel X65， and finds that the cause of flocculent flow in the stopper rod is the adhesion of high Ca calcium aluminate to the head of the stopper rod.In the early stage of pouring， the head of the stopper absorbs heat， causing a sharp decrease in the temperature of the surrounding steel liquid， and the precipitation of high melting point calcium aluminate is adhered to the head of the stopper， causing the stopper curve to rise.In addition， by thermodynamic calculations， the Ca content required to form 12CaO·7Al2O3 in low-carbon， low sulfur， and low oxygen aluminum killed steel X65 at 1 540 ℃ is 16×10-6， excess Ca further reacts to form high melting point calcium aluminate.Under the condition that magnesium refractory materials are used in all areas in contact with the molten steel， such as the working layer of the intermediate ladle， stopper rods， nozzles， and bowl mouths， and in the production of low-carbon， low sulfur， and low oxygen aluminum killed steel， the more Ca content is fed into the molten steel， the more severe the upward movement of the stopper rods.Using high alkalinity slag system and Al to reduce O and S in steel， and then controlling the Ca feeding amount between 0.065 0～0.071 5 kg/t， and controlling the calcium content in the tundish between （10～15）×10-6 can effectively control flocculent flow.关键词：Flocculent Flow;Calcium Treatment;Aluminum Content;Calcium Aluminate;Pipeline Steel3|0|0更新时间：2025-05-09
- 摘要：The slag-making material addition system of Q355 steel was optimized， from the traditional "three-batch feeding" mode to the "eight-batch feeding" mode， and 100 kg steel slag modifier was added in the first and third batches respectively. At the same time， the oxygen blowing system of Q355 was changed from the traditional "constant flow， high-low-low lance position" control to "variable pressure， high-low-high-low lance position" control. Base above， a converter economical smelting process suitable for the actual production of Q355 steel was developed. The practice results show that compared with the original smelting process， the total oxygen supply time of the improved process is shortened by 1 min， the hit rate of phosphorus at the end point of smelting is 100%， the average value of phosphorus removal rate at the end point is increased by 4.24%， and the average value of lgLp is increased by 0.35. Compared with the consumption of slagging materials in the original process， the average consumption of steel lime per ton in the improved process is 34.01 kg， a decrease of 8.73 kg， and the average consumption of total slag material per ton of steel is 43.95 kg， a decrease of 9.13 kg. In addition， the average iron and steel material consumption of the improved process is 1078.02 kg/ton steel， which is 0.60 kg/ton steel less than that of the original process. The economic smelting of Q355 steel converter is realized， the consumption of slagging material and steel material is reduced， and the production cost of Q355 steel smelting is effectively reduced.关键词：Converter Steelmaking;Economic Smelting;Dephosphorization;Q355 Steel2|0|0更新时间：2025-05-09
Smelting and Solidification
- 摘要：The precipitation behavior of precipitates in S32750 super duplex stainless steel was studied by aging treatment at 850 ℃. Thermo-Calc software was used to predict the precipitates and phase composition in tested steel. OM， SEM and EDS were used to analysis the microstructure and precipitates of S32750 super duplex stainless steel after different aging treatment. K-J-M-A model was used to analysis the kinetic of precipitation of σ phase. The results showed that the σ phase was preferred to precipitate at ferrite/austenite boundaries during the aging process at 850 °C. There were two main steps to control the precipitation of σ phase： nucleation control and element diffusion control. In addition， χ phase and Cr2N phase also precipitated during aging treatment. χ was the sub-stable phase， precipitated in the early aging period， and finally transformed into σ phase with the prolongation of aging time.关键词：Duplex Stainless Steel;Precipitates;Kinetic;Aging Treatment2|1|0更新时间：2025-05-09
- 摘要：The thermal expansion curves of 20CrMnTiH test steel with three compositions at different cooling rates were measured by DIL805 type quench deformation expansion instrument ， and the microstructures at room temperature were observed， the continuous cooling transition （CCT） curves were drawn. The test results show that the composition fluctuation mainly affects the cooling range of bainite and martensite phase transformation during the cooling transformation of 20CrMnTiH， and has little effect on the critical phase transformation temperature. The kinetic parameters of martensitic transformation of the three test steels were fitted by using K-M equation. Combined with the optimized Li empirical model and the regression equation of critical transition temperature， a prediction model of phase transformation prediction model of ferrite，pearlite and bainite during continuous cooling of 20CrMnTiH was established ，the influence of composition fluctuation on CCT curve of the test steels were predicted successfully. Furthermore， the end-quenching simulation model of 20CrMnTiH steel was established by finite element analysis method， which can better predict the influence of composition fluctuation on the hardenability of the test steel. This method can provide reference for the composition optimization design and material selection of gear steel.关键词：20CrMnTiH Steel;CCT Curves;Phase Transition Dynamics;Composition Fluctuation;Phase Transition Model3|0|0更新时间：2025-05-09
- 摘要：GH4710 nickel base alloy ingots， melted by VIM plus VAR， were subjected to trails of two-stage high-temperature homogenizing heat treatments， the microstructure and grain size of the ingots before and after heat treatment were analyzed by metallographic microscop. the distribution and content of alloy element in the ingot before and after heat treatment were evaluated by scanning electron microscope and electron probe， as well as to calculate the segregation index for alloying elements in different positions of ingots. Test result verified that， the two-stage homogenizing heat treatment at （1 150±50）℃×30 h-（1 200±10）℃×50 h， it could significantly eliminate the eutectic phase in the structure of GH 4710 ingot and reduce the element segregation in the ingot，and the mechanical properties of the forged bar are improved significantly. Under the test conditions of 980 ℃， 120 N/mm2， the persistence performance reached 126 h and 134 h， which was about double improvement compared with 53 h and 74 h of un-homogenizing heat treatment production. The persistent elongation rate has also increased by more than 50%.关键词：GH4710 Nickel Base Superalloy;Eutectic Phase;Homogenizing Heat Treatment;Dendritic Segregation5|3|0更新时间：2025-05-09
- 摘要：In order to develop non-spheroidizing annealing 12Cr1MoV hot rolled wire rod ， based on deformation induced phase transition mechanism， the finishing rolling temperature of 830 ℃ and laying temperature of 800 ℃ were adopted. By inhibiting deformation austenite grain recovery and recrystallization process，increasing deformation energy storage， thereby promoting austenite decomposed into ferrite and pearlite. Meanwhile in stage controlled cooling was realized with adjusting the air-cooled roller speed， the quenching microstructures were completely eliminated because prolonging the holding time between 630 ℃ and 750 ℃. The test results are that the tensile strength of 12Cr1MoV hot-rolled wire rod was reduced from 576 MPa to 520 MPa， while reduction of area increasing from 66% to 74%.The elimination of quenched microstructure significantly optimizes the deformation ability of wire rod ，and also avoided holes in the cross-section center or draw break which caused by a small or minimal martensite microstructure are unable to cooperate with deformation . Plastic cracking has not occurred after batch use of multiple specifications by users.关键词：Boiler Flat Steel;12Cr1MoV Steel;Deformation Energy;Deformation Induced Phase Transition;Martensite119|5|0更新时间：2025-05-09
Forming and Phase Transition
- 摘要：The reasons of the fatigue failure of flexspline are analyzed by observation analysis， observation and hardness determination of fracture morphology of microstructure. The results show that the micro-structure of the flexspline of the failed harmonic reducer are tempered troostite， and there is more severe grade 3 banded structure on the flexspline . Although the 4.42 μm micropores caused by MnS and Al2O3 inclusions exist， they are not the main cause of breakage due to its small size and number . Meanwhile the overall grain size of the sample， especially the grain size at fracture crack， is coarse， and the grain at the fracture crack is thicker and more uneven. the grain size at the fracture crack is 1.4 times that away from the fracture grain. The coarse grain assembly leads to smaller grain boundary area， which not only leads to more uneven plastic deformation， but also more prone to stress concentration， which causes primary cracks， and is difficult to hinder crack expansion， resulting in fracture failure of the sample.Therefore， the primary austenite grain is the main cause for fatigue fracture of flexspline. The grain refinement can be achieved by circulating heat treatment or adding normalizing pretreatment.关键词：Harmonic Reducer;Flexspline;Fracture Failure4|2|0更新时间：2025-05-09
- 摘要：In order to investigate the stress corrosion cracking behavior of ultra-high strength stainless steel， the influence of Nb microalloying on the corrosion fatigue properties of Cr-Co-Ni-Mo series ultra-high strength stainless steel was studied by OM， XRD， TEM and other testing methods in combination with corrosion fatigue test. The results show that the steel has stress corrosion sensitivity in 3.5% NaCl solution， and the stress corrosion cracking mechanism of the steel was a mixed mechanism involving hydrogen embrittlement and anodic dissolution. Niobium alloying improved the corrosion fatigue performance of the steel， that is， the corrosion fatigue strength of steel increases from 440 MPa to 495 MPa after adding 0.11% Nb. The main reason is that niobium alloying refined the grain size of steel， promoted the precipitation of irreversible hydrogen trap of NbC in steel， and increased the amount of prior austenite grain boundaries， the proportion of low-angle grain boundaries， the number of Σ3 grain boundaries， and the volume fraction of austenite in steel.关键词：Ultra-high Strength Stainless Steels;Erosion Fatigue;Mechanism of Stress Corrosion Cracking;NbC;Austenite3|1|0更新时间：2025-05-09
- 摘要：In this paper， two kinds of 18CrNiMo7-6 gear steels with sulfur content of 0.002% （low sulfur content） and 0.022% （high sulfur content） were studied. Pseudo-carburizing samples were obtained by reference to gear heat treatment process， and the effects of sulfur content on mechanical properties， microstructure， fatigue properties and inclusion distribution of the steels were investigated. The results show that the strength of the two steels is basically similar， while the steel with high sulfur content has better plasticity and low temperature impact toughness. Meanwhile， its fatigue limit and fatigue life are better than those of the low sulfur content steel， the fatigue ratio increases from 0.445 to 0.479. Sulfur content significantly affects the distribution of inclusions in steel， the inclusions in low sulfur content steel are mainly composed of MnS and oxides with less quantity but larger size， while the inclusions in the high sulfur content steel are mainly complex inclusions composed of Cas， MnS and oxides with more than doubled quantity but smaller size. By employing Ca treatment technique， the inclusion size of high sulfur content steel is obviously refined， which favors better mechanical properties and fatigue performance of steel.关键词：18CrNiMo7-6 Gear Steel;Mechanical Properties;Fatigue Properties;Non-metallic Inclusion;Sulfur Content3|0|0更新时间：2025-05-09
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