The high-end equipment industries in the fields of aerospace， energy， petrochemical， shipbuilding， rail transportation， new energy vehicles， energy conservation and environmental protection， and electronic information have developed strongly， putting forward higher requirements for the quality and performance of special steel and special alloy materials， and the demand has surged. Therefore， in recent ten years， China's special metallurgy industry has been rapidly development. This paper first analyzes and summarizes the new requirements of ultra-high strength steel， supper alloy， corrosion resistant alloy， heat resistant steel， special stainless steel， high performance bearing steel， tool and die steel and precision alloy for the above-mentioned high-end equipment manufacturing. Secondly， the development status and trend of traditional special metallurgical processes and several new special metallurgical processes are analyzed. It is emphasized that the combination with basic oxygen furnace/electric arc furnace steelmaking process can provide high clean consumable electrode for electroslag remelting and vacuum arc remelting， and can also provide pure raw material for vacuum induction furnace. The short process of the electroslag remelting with continuous casting billet as the consumable electrode can significantly improve the production efficiency and reduce the production cost. At the same time， the duplex process of high nitrogen stainless steel smelting and the process flow of powder metallurgy and spray forming of tool and die steel are also briefly introduced. Third， China's special metallurgical industry development status， as well as the progress of new technology and new equipment have been summarized. Finally， suggestions and prospects for the technical development of special metallurgy in China in the next ten years are put forward.

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 Ac ₁ phase transition temperature of 18CrNiMo7-6 wind power steel is 765 ℃， and the Ac ₃ phase transition tempera ture 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 de creases 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.

As one of the indispensable core components of advanced aero-engine， nickel-based single crystal turbine blades （hereinafter referred to as single-crystal blades） have extremely demanding requirements in terms of dimensional accuracy of the hollow structure， uniformity of alloying element distribution， and metallurgical quality of the surface and inner cavity. It is found that the control of temperature gradient during directional solidification directly affects the performance and quality of single crystal blades， and whether the continuous acquisition of stable heat flow becomes the key of directional solidification .With the continuous progress of computer technology， numerical simulation has become one of the important methods of single crystal blade directional solidification research. Firstly， introduce the single crystal blade technology is introduced and the heat transfer method in the directional solidification process is then analyzed.Secondly， the optimization methods of boundary conditions of interfacial heat transfer coefficient for numerical simulation are summarized， focusing on the application of Beck's inverse method and finite difference method in the solution of interfacial heat transfer coefficient. The results proves that the two methods can be used to solve the interfacial heat transfer coefficient between castings/shells， where the accuracy of the simulation of the temperature field can be effectively improved.Finally， the research progress of numerical simulation of the temperature field during directional solidification is also traced， and the influence of process parameters on the temperature field is summarized. Based on the analysis of the research progress of numerical simulation of temperature field during directional solidification of nickel-based single crystal turbine blades， the optimization direction of the directional solidification process and the subsequent development trend of the related technology are proposed to promote the research and development process of single crystal turbine blades.

With the continuous improvement of material requirements for high-performance aviation engines， the degree of alloying and the mass fraction of the γ' phase in new nickel-based superalloys for high-temperature applications continue to increase. This leads to progressively more challenging melting processes for these alloys. High-alloyed wrought nickel-based deformation superalloys are generally produced through a triple combination process of Vacuum Induction Melting （VIM） + Protective Atmosphere Electro-Slag Remelting （PESR） + Vacuum Arc Remelting （VAR）. Due to the influence of alloying degree， alloys are prone to solute segregation and elemental partitioning between liquid and solid phases during the melting process， making electrodes and ingots susceptible to cracking under the combined effects of thermal stress and phase transformation stress. This not only causes arc fluctuations during the subsequent remelting process but also adversely affects the quality of the ingots. Electrode crack formation is a complex metallurgical defect that occurs in the solidification process of superalloys and has been a common technical challenge that has long plagued the expansion of ingot sizes for high-alloy， difficult-to-deform superalloys in China. Therefore， this paper reviews the recent research progress of the author’s team and research groups at home and abroad in the crack formation mechanism， influencing factors of crack and crack control of wrought nickel-based superalloys， and looks forward to the future development direction of wrought superalloy precipitation strengthened nickel-based superalloys.

The influence of different bottom blowing processes on the flow field and dead zone distribution of molten steel was simulated using Fluent software， taking the 130 ton ladle as the research object.The results showed that when the center distance decreased from 0.65R to 0.50R， the average flow velocity of the molten steel decreased from 0.24 m/s to 0.05 m/s， and the proportion of low flow velocity areas significantly increased. The steel flow at the two wall ends was slow， and the average flow velocity at the interface of slag and molten steel decreased from 0.18 m/s to 0.009 m/s. The proportion of dead zones increased from 7% to 25%， and the overall stirring effect decreased； When the center angle of the permeable brick increased from 85° to 180°， the average flow velocity of the molten steel decreases to 0.09 m/s， the average flow velocity at the interface of slag and molten steel was 0.05 m/s， and the dead zone volume ratio increased to 28%； With the amount of argon blowing increased， the flow rate of the molten steel significantly accelerated， the dead zone volume further decreased， and the mixing time of the molten steel gradually shortened. At 200 L/min， the average flow rate increased to 0.43 m/s， and the average flow rate at the horizontal interface of slag and molten steel was 0.32 m/s. There was no slag entrapment phenomenon， and the mixing time of the molten steel was 300 seconds. In summary， it is determined that the optimal solution is an argon flow rate of 200 L/min for breathable brick 1 and 210 L/min for breathable brick 2.under the following conditions： the diameter of the two breathable bricks is 165 mm， the angle of breathable brick is 85°， the center distance of breathable is 0.65 R， the thickness of slag layer thickness is 100 mm， the thickness of air layer is 400 mm ， and bottom blowing time is 600 s.

Based on the laboratory small-scale low-frequency electroslag remelting device， taking 70%CaF ₂+30%Al ₂O ₃ electroslag remelting 304L austenitic stainless steel as the research object， we analyze in detail the influence of different remelting current intensity on the number， size dimension and type of inclusions in the electroslag ingot under low-frequency conditions. The results show that compared with the power frequency electroslag remelting （50 Hz， 1 800 A）， the oxygen （O） content in electroslag ingot increased by 172.2% and 75.5% respectively under the condition of low frequency （2 Hz） and different current intensities （1 800 and 1 400 A）. Nitrogen （N） content decreased by 4% and 3.4%， respectively.At low frequency， the type of inclusions in the electroslag ingot did not change when remelted with different current intensities， but the number of inclusions and the proportion of each type of inclusions changed. The number of inclusions decreases with the decrease of current intensity at low frequency， However， compared with the power frequency condition， the amount of debris still increased by 173% （1 800 A） and 63.7% （1 400 A）， and the increase part was basically small inclusions below 10 μm， and the amount of large-size inclusions （>10 μm） increased less.

Based on domestic and abroad market demands，this article introduces the development process of pre-hardened and ultra-thick 1.2311 steel plate used for plastic mold steel.Experimental study on continuous phase transformation behavior of 1.2311 steel was conducted，and a static continuous cooling transformation curve was drawn.By KR pretreatment→120 t converter （smelting using slag retention method can control carbon content within 0.20%-0.30%）→LF（refining argon blowing time ≥60 minutes）→VD （vacuum degree ≤67 Pa，vacuum holding time≥20 minutes）→450 mm slab continuous casting（low superheat of 8-15 ℃，low pulling speed of 0.45 m/min）→Slab heating→5 000 mm mill rolling （the sum of the last three pass reductions is ≥140 mm for rough mill）→870-890 ℃ normalizing process→ACC controlled cooling （combination of water cooling and air cooling）→550-610 ℃ tempering process，the pre-hardened and ultra-thick steel plate for plastic mold 1.2311 with a specification of ≥150 mm was successfully developed.The results show that a Brinell hardness deviation of ≤15HBW across the entire thickness，resulting in good uniformity of hardness，the ultrasonic testing of the plates meets the requirements of Level I in GB/T2970―2016.All comprehensive performance indicators meet the development requirements.

There is an urgent need to develop low-cost， high-strength， and toughness grades of steel for domestic wind power fasteners in order to enhance the competitiveness of the industrial chain and fully participate in market competition. Through the control of smelting process to assure residual w ［P］≤0.015% and w［S］≤ 0.010% and the total oxygen content w［T.O］ stably controlled to be less than 10 × 10 ^-6 during low oxygen operation practice. Two stage low-temperature rolling is adopted and the single pass reduction rate is controlled between 8% to 12%. A 10.9-grade 32CrB4 bolt steel with good impact toughness at -40 ℃ low-temperature for 38.8 mm specification has been successfully developed. The results of mechanical property inspection and metallographic observation indicate that the developed steel has good tensile properties and excellent low-temperature impact properties. The optimal heat treatment process has been studied， which is 820 ℃ soaking water quenching and 510 ℃ soaking tempering. The room temperature tensile strength can reach 1 075 MPa， and the average low-temperature impact value of -40 ℃ KV2 can be 53 J. The microstructure is mainly tempered martensite， with excellent and comprehensive mechanical properties and good uniformity.

High-nitrogen austenitic stainless steels exhibit high strength and toughness， strong wear and corrosion resistance， and also possess non-magnetic property along with excellent biocompatibility. These attributes have garnered them extensive attention across a variety of fields， including ocean engineering， energy and chemical industries， national defense and aviation， and biomedical applications. However， in the preparation process， it still faces a series of problems and technical challenges such as inaccurate control of nitrogen enrichment levels， easy precipitation of nitrogen during solidification of high-nitrogen steels to form pores， and precipitation of coarse nitrides during hot working， which limits its large-scale development and application to a certain extent. The development status， preparation process， and strengthening mechanisms of high-nitrogen austenitic stainless steel have been systematically elaborated. Firstly， a review of the domestic and international development history and current research status of high-nitrogen austenitic stainless steel are reviewed. Secondly， the production and preparation processes for high-nitrogen austenitic stainless steel have been summarized， encapsulating various techniques for the melting-casting method. This includes a comparison and analysis of their advantages and disadvantages， such as the Larger Pool Method， Pressurized Induction Melting， Pressurized Ladle Blowing， Pressurized Electroslag Remelting， and Pressurized Plasma Arc Melting. Additionally， an overview of the powder metallurgy process for fabricating high nitrogen steel is presented， which includes methods such as Mechanical Alloying， Gas Atomization， Plasma Rotating Electrode Process， and Solid-state Powder Nitriding. Furthermore， a summary is provided around various forming processes including Hot Isostatic Pressing， Spark Plasma Sintering， Metal Injection Molding， Hot Pressing Sintering， Cold Pressing Forming， and Additive Manufacturing. Ultimately， the discourse delves into the mechanisms underlying nitrogen's fortification role in austenitic stainless steel， encompassing Solution Strengthening， Grain Refinement Strengthening， Strain Hardening， and Precipitation Hardening. Moreover， the dialogue addresses the predominant challenges encountered in the evolution of high nitrogen austenitic stainless steel， proffering a prospective outlook on the field's advancement.

In order to study the differences in microstructure and high temperature properties of different positions of turbine disc forging in GH4706 alloy， comparative analysis of mechanical properties at high temperature were carried out. Detailed experiments included high-temperature tensile property （conducted at the temperature of 400 ℃， 500 ℃， 600 ℃ and 650 ℃）， high-temperature low-cycle fatigue （conducted at the temperature of 400 ℃， 500 ℃ and 600 ℃） and high-temperature stress rupture life （conducted at the condition of 650 ℃/690 MPa and 600 ℃/700 MPa） based on typical service performance requirements. The test results showed that the grain sizes of the hub， spoke and rim varied significantly， with the hub grain size level 4 （average grain size 84 μm）， spoke grain size level 3 （average grain size 120 μm） and rim grain size level 2 （average grain size 183 μm）.The γ′-γ″ composite of the samples in different positions were dispersed in spherical shape. The η phase of hub and plate is in needle shape， with larger size， and distributed parallel to grain boundaries. The η phase of rim precipitates in the shape of short rods with smaller size and dispersed arrangement at grain boundaries. There was no significant difference in high-temperature tensile strength at different locations. However， the samples from hub had excellent low-cycle fatigue performance （4 363 cycle number）， while the tensile plasticity and stress rupture life of rim was the longest （1 259 h）. The study indicated that the variation of microstructure from different positions of turbine disc forging in GH4706 alloy had significant effects on mechanical properties.

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（HotMetal+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 ad⁃ dition during tapping， vacuum holding time ≥25 min and soft argon blowing， superheat control， full process Argon protec⁃ tion 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.

The flexible bearing steel with long fatigue life using for robot harmonic speed reducer has been successfully de⁃ veloped 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 roll⁃ ing 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 inclu⁃ sions 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 increas⁃ ing 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.

During the process of electric arc remelting， the content of gas components （such as H， O， N， etc.） in the steel is significantly influenced by the gas permeability of the slag system used. In order to explore a slag system with low hydrogen permeability suitable for nuclear-grade 316H stainless steel in electric arc remelting， the hydrogen permeability of five slag systems used in electric arc remelting was determined. The results showed that the newly developed 63%CaF ₂-30%Al ₂O ₃-7%MgO slag system had the lowest hydrogen permeability.meanwhile the hydrogen permeability of slag system， 65%CaF ₂-30%Al ₂O ₃-5%MgO， was similar to that of the 63%CaF ₂-30%Al ₂O ₃-7%MgO slag system， and hydrogen permeability of both slag systems exhibited a significant reduction compared to the original slag system used in the steel plant's electric arc production，declined from 6.58×10 ^-6 mol/（cm·min） to 1.89×10 ^-6 mol/（cm·min） and 2.18×10 ^-6 mol/（cm·min） respectively.The higher the optical basicity of the slag was， the higher the hydrogen permeability was. CaO in the slag had a high affinity for water and can easily increase the hydrogen content in the steel ingot during electric arc remelting， while the addition of MgO in the slag system can significantly reduce hydrogen permeability. Under the research conditions， the influence of the slag system's constituents on its hydrogen permeability was more significant than the optical basicity.

Pressurized electroslag remelting （PESR） is currently the most effective production route for industrial preparation of high nitrogen steel and high nitrogen alloys， and is currently a research focus and the most advanced technology in the field of electroslag metallurgy. This article introduces the development of the integrated line equipments， process technology， and main product characteristics of PESR. A review is conducted on the core components of the nitrogen alloy feeding system and water-gas dynamic balance system in the current PESR furnace equipment. In response to the current technological difficulties in PESR process， this paper elaborates on the development of new technologies such as the mechanism and method of nitrogen addition and gas-phase nitrogen addition technology for nitriding alloys， development of a new high-efficiency heating refining remelting slag system， and precise element control. In recent years， with the application of series newly built domestically produced pilot scale PESR furnaces and the successful development of series of high nitrogen steel products， China has made a significant breakthroughs in the integrated line equipment independent research and technological development， and gradually stepped forward to the international advanced level.At the same time， deepening the independent research and development of industrial grade PESR equipment and process technology research and development， ensuring the preparation of key materials urgently needed for high-quality special steels and special alloys in China's aviation， aerospace， and military industries fields and so on， is an important direction for the development of modern electroslag metallurgy technology in China.

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 back scattering 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 in clusions 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.

The disc cutter is the key component of the shield machine， and it is also the most easily worn and failed component in the tunneling construction process. The wear of the disc cutter ring is mainly composed of three types of abrasive wear， adhesive wear and fatigue wear， among which abrasive wear and adhesive wear are the main wear mechanisms. In the process of rock breaking， strong extrusion and high impact make the cutter ring often wear， eccentric wear， blade， fracture， blade collapse， shedding and other failures. The cost of cutter ring loss accounts for 5%-10% of the total project， and the maintenance and replacement of cutters caused by the cutter ring failure greatly reduce the engineering construction efficiency. At present， the commonly available materials for cutter rings are DC53 and H13 steels， and their wear resistance and impact toughness depend on the type， morphology， size， quantity， distribution and matrix structure characteristics of carbides in those steels. In order to inprove the performance of the disc cutter ring， domestic and foreign scholars have carried out a series of studies on the optimization of alloy design for the cutter ring， the one-time forming preparation of the cutter ring， the induction heat treatment preparation of the gradient performance cutter ring， and the development of the bimetallic composite cutter ring， which provides a strong support for the performance enhancement of the cutter ring.

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 micro⁃ structure 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 low-temperature steel plate is mainly composed of tempered sorbite structure and 3% -8% reverse austenite. The addition of 0. 015% Nb in⁃ creases the average YS and TS of 9Ni low-temperature steel by about 50 MPa and 40 MPa， respectively. The impact ab⁃ sorption energy increases by about 40 J tested at -196 ℃.

 In order to improve bias flow， jump bar and water plugging phenomenon during ultra-low carbon steel continuous casting process in a factory， through the tunish breathable on the nozzle， plug rod and immersion nozzle such as continuous casting function resistant material improvement， switch the air top nozzle to switch to special diffusion breathable material， blowing into the argon bubbles along the nozzle form uniform air curtain. The surface stomatal rate is 5.2% higher than that before the improvement， which prevents the accumulation of inclusions in the inner wall of the nozzle and alleviates the clogging of the nozzle. One argon hole located in center is changed to six holes of stopper rod， which can realize 360° even argon blowing around its head and decrease inclusion collection on the head. The SEN adopts merterials of carbon free， low aluminum， high silicon content. These refractory can react with the inclusion on the wall of SEN， which prevents its clogging. After the application of improved resistant materials in ultra-low carbon steel， the number of jumping rods per casting is reduced by 0.83 times and 31.8%， the frequency of online replacement of SEN caused by nozzle plugging is reduced by 0.38 pieces and 41.3%， and the control accuracy of crystallization level is stabilized， the qualified rate of cold rolled coil inclusion is improved by 0.238%， and the number of single tunish casting heats is increased by 0.53 heats and increasing by 8%， thus optimizing the flow field of 1 000-2 200 mm. It is proved to put forward to optimize 1 000 mm-2 200 mm caster’s mould flow field.

The strength and plasticity of 10B38 boron containing cold heading steel under different high temperature condi⁃ tions 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 mea⁃ sured， 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 struc⁃ ture； 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 re⁃ sults showed that by reducing the cooling rate to 0. 5-2 ℃/s， ideal ferrite and pearlite hot-rolled structures can be obtained.

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 dimen⁃ sional pre-melting and remelting smelting is used to improve the purity of molten steel， and low melting speed is set to re⁃ duce 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.