The φ10~25 mm reinforced bars of Nb microalloying 400 MPa Ⅲ Grade steel - 0.17~0.25C,1.20~1.45Mn,0.02～0.04Nb have been developed by 40 t EBT are furnace- 40 t LF- 150 mm×150 mm billet concasting process. The mechanical properties of reinforced bars were σ _s 420~490 MPa,σ _b 590~680 MPa,δ ₅ 24%～30%,and the yield strength decreasing was minor after nature aging for 8 weeks. The produced Nb microalloying 400 MPa Ⅲ grade steel reinforced bars were up to the requirement of CB 1499- 1998 standard and the production cost was obviously decreasing by 0.02%～0.04%& Nb to replace 0.05%～0.10% V.

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 precipitate behavior of second phase and  structure of 0.08C- 1.0Mn-Nb+Ti<0.10 microalloy high strength steel 1.5 mm sheet deformed by 53% annealed at 650 ℃ and 680 ℃ has been tested and studied by transmission electron microscope. the results showed that the second phase in test steel was(Ti,Nb)(C,N)compound precipitate phase, generally the size of second phase particles was 20~30 nm,and with increasing annealing temperature the amount of second phase increased. The higher strength(yield strength ≥480MPa at 650 ℃)is due to second phase precipitate strength and inhabiting gain growth to form fine grain.

The annual output of steel melted by converter was nearly up to 190 million tons in China in 2003, which was 85.2% of annual output of steel in China and was 25% of world converter steel output in that year. The number of 50 ~ 300 t converters increased to 134 sets in 2003 from 75 sets in 2001, and the process and technology of converter steelmaking further optimized. the new grade steel and quality steel melted by converter increased very fast including lo w alloy steel, atmospheric corrosion resistant steel, TRIP(transformation induced plasticity steel, and special steel such as alloy structure steel, gear steel, bearing steel and steel for boiler. In the future the converter steel production mainly depended on potential- tapping and revamping of excellent iron and steel producers to further improve technology and equipment, expend ·steel grade range, increase quality of steel, reduce consumption and improve environment.

The melting method of nickel-based superalloy is the decisive factor related to the alloy quality. Vacuum induction melting can effectively control the content of O， N， H and other gases and harmful impurities in alloy ingots， and accurately control the alloy composition. On this basis， the remelting of alloy （electroslag remelting and vacuum arc remelting） can further reduce the content of S， P and other harmful impurities， eliminate the defects such as component segregation and shrinkage cavity， and optimize the control of the solidification structure， so as to achieve the melting of large size and high-quality alloy ingots. This paper reviews the progress of the melting process of nickel-based superalloy， and focuses on the principles and characteristics of common melting technologies including vacuum induction melting， electroslag remelting， and vacuum arc remelting. The research progress of "vacuum induction melting + protective atmosphere electroslag remelting"， "vacuum induction melting + vacuum arc remelting" duplex melting process and "vacuum induction melting + protective atmosphere electroslag remelting + vacuum arc remelting" triple melting process in nickel-based superalloy melting are discussed. Finally， some suggestions on the selection and development direction of nickel-based superalloy smelting process are propounded.

Based on published patented manufactured technologies for high strength pipeline steel including heavy plate, hot rolled coil and seamless tube at home and abroad in 2011. the key manufacturing technologies, structure and properties of pipeline steel with excellent anti-large-strain-deformation, low temperature toughness and corrosion resistance are summarized. The main R&D characteristics and trend on high strength pipeline steel are excellent anti-large-strain-deformation steel- through dispersed M/A to increase strength of steel: low temperature toughness steel- using Mn-Nb-Mo alloying and control rolling to get main ferrite and/or bainite structure ； and anti-HIC ( hydrogen-induced cracking) pipeline steel- with prerequisite to control C, P, Mn segregation induced HIC, lowing Nb and Ti content in steel to prevent Nb, Ti carbo-nitride inducing hydrogen-induced cracking.

The  wire  for  steel  cord  of  tyre  is  a  high  carbon   steel(0.70~0.75C-0.15～0.30Si-0.40～0.60Mn), which is widely applied to auto tyre and conveyer belt industries because the rubber products stengthened with 40.15~ 0.38 mm steel cord has excellent strength and springiness which is available to increase the safety of car and decrease fuel expenses. Due to requirement of high quality on wire for steel cord of tyre, in general the process flow sheet :converter or  arc furnace- LF- VD or RH-Ca treatment- concasting is adopted to produce the steel.The control of chemical compositions,  gas content and inclusion is presented and the general conditions of production,quality requirement and development trend of  wire for steel cord of tyre at home and abroad are summarized in this paper.

 The  effect  of cooling rate,reduction,original  austenite  grain  size  and  strain rate  of0.05C-0. 13Nb  steel  af- ter  single  pass-reduction  40%  with  2  s ^-1   at   1000  ℃  or  two  pass-reduction  40%  with 2 s ^-1  at   1000℃+  reduction  40%  with 5 s ^-1  at 980 ℃ on structure and microhardness HV has been studied by Thermecmastor-Z thermal simulation test ma- chine.Results indicated that with increasing cooling rate the granular bainite gradually increased,of which the content was up  to93%  as  cooling  rate  was  to 5  ℃/s,and  the  HV  value  obviously  increased,while  cooling  rate  was  more  than  5  ℃/s the morphology of bainite island structure was changed and the HV value increased little; with decreasing original austenite grain size and increasing reduction the HV value decreased; but the effiect of strain rate on HV value was not appreciable.

The technical characteristics of electric arc furnace steelmaking with direct reduced iron as a substitute for scrap steel are analyzed， and the main factors affecting the smelting power consumption are expounded . The results indicate that a large amount of steel left in melting pool （≥ 40%） and intensive mixing such as enhanced oxygen supply， bottom blowing， and electromagnetic stirring are important ways to promote melting and shorten the tap-to-tap cycle （which can be shortened by 8%-10%）. The proportion of direct reducing iron exceeds 30%， continuous feeding should be used. The feeding speed in the early and middle stages of smelting is generally equal to the melting speed of 28-33 kg/min （power supply power is 1 MW）. It is necessary to match lime and dolomite to prevent the erosion of slag line， and the whole smelting process should be sprayed with carbon foam slag to ensure the power supply efficiency. To reduce power consumption of smelting， direct reduction iron with high C content， high metallization rate， low SiO ₂ content， low P content， low S content， and higher temperature should be used as much as possible within a certain suitable range （that is， w［C］ 1%-4.5%， metallization rate ≥ 90%， w［SiO ₂］ ≤ 6%， w［P］ ≤ 0.1%， w［S］ ≤ 0.04%）. The compact short process combining direct reduction iron vertical furnace and electric arc furnace is an important direction for low-carbon， energy-saving， and clean production.

The manual welding on 7 mm plate of ultra-fine-grained steel SS400 (/% : 0.18C, 0.04Si, 0.43Mn, 0.022Al, 0.002Ca) has been carried out by using J442 (/% : ≤0.12C, 0.3-0.6Mn) , J506 (/% :≤0.12C, 1.6Mn) and J507 (/% : ≤0.12C, ≤1.25Mn) welding rod with heat input 6-14 kJ/cm, and the structure and microhardness of welded joint are observed and measured by optical microscope and microhardness tester. Results show that with increasing alloy element content in welding rod, the amount of acicular ferrite in welded zone increases； as heat input ≤10 kJ/cm, the change of size of coarse grain in heat affected zone is minor, and as heat input is larger than 10 kJ/cm, the size of coarse grain in heat affected zone increases obviously ； the microhardness of welded joint with different welding process is all higher than the microhardness of base metal, there is no soften zone in welded joint.

The yield strength 750 MPa high strength low alloy (HSLA) steel for container (/% : 0.06 ~0.09C, 0.25 ~0.35Si, 1.60 ~1.80Mn, ≤0.015P, ≤0.003S, 0.10 ~0.20Mo, 0.05 ~0.06Nb, 0.09 ~0.llTi, ≥ 0.0015Ca, ≥0.015Alt) has been designed and developed. The process flowsheet for tested steel is 260 t BOF-LF-RH-230 mm slab casting-hot-rolling to 2 ~ 6 mm plate. With the process measures including Nb-Ti compound microalloying and Ca treatment, controlling finishing rolling temperature 840 -880 ℃, lamina flow cooling rate ≥ 60℃ /S, coiling at 520 -580℃ , and hot-rolled coil cooling rate ≤ 10 °C/h， the hot-rolled strip coil has better surface quality, its structure is fine grain ferrite + Nb-Ti carbonitride, and the mechanical properties of strip are upper yield strength 760 〜790 MPa, tensile strength 860 -910 MPa, and elongation 21% ~25% to meet the requirement of user.

Center segregation of continuous casting slab is the main cause to form banding structure in fine blanked steel. Dynamic soft reduction technique is an effective measure to improve the center segregation of continuous casting slab. In this paper,final solidifying end of 230 mm continuous casting slab can be accurately determined by rivet pin shooting experiment improvement of soft reduction process. The center segregation of representative fine blanked steel was beyond M2.4 of Manesman standard before improvement of soft reduction process ( at zone 9 and 10, total reduction 7. 5 mm). The result of rivet pin shooting experiment is the reference of parameter of dynamic soft reduction. With the parameter optimizing of soft reduction (at zone 8 and 9, total reduction 10 mm) , center segregation of continuous casting slab can be controled within M2. 0 of Manesman standard. Banding structure in fine blanked steel can also be controled effectively.

Based on published patented manufactured technologies of corrosion-resistant steels for oil country tubular goods ( OCTG) in the world from 1994, the characteristics of research and development of corrosion-resistant steels for OCTG at manufacturing enterprises and the chemical composition, key manufacturing technologies and properties of corrosion-resistant steels for OCTG including martensite, austenite, dual phase and complex phase stainless steels, low alloy steels and Cr alloy steels are summarized. The key points of research and development at OCTG manufacturing enterprises are development of the OCTG with low cost and corrosion resistance in various conditions.

The process flow sheet, key equipment and technology characteristics for maximum coil weight 35 t, 2 ~ 16 mm hot rolled stainless steel strip annealing and pickling line are presented. The steel grades produced in the line are austenite ,ferrite and martensite stainless steel； the strip is heated in annealing furnace by natural gas, the furnace temperature is up to 1 180 °C and the total furnace length is 96 m； the effective descaling is carried out before pickling, the pickling solutions are sulphuric acid and nitric acid + hydrofluoric acid, the maximum speed of pickling is 60 m/min, the waste water and waste acid are recovered and regenerated, and the acid mist are also recovered and treated.

With using the process measures including controlling mold inlet water temperature 40℃ , outlet water temperature 68 ℃ ； controlling model of computer auto back feeding for shrinkage ； at end auto back feeding, changing consumable electrode to graphite electrode withing 90 s and power supply with 53 V, 3 000 A melting for 3 ~5 min, then again changing to consumable electrode and power supply with 50 V, 4 000 A for 6 min, the depth of top shrinkage cavity defect of electroslag remelting ( ESR) ingot decreases to 30 ram from original 100 mm. Production practice shows that the process operation of back feeding for shrinkage is simple and easier to do. The forged billets of remelting 210 piece tool steel 9Cr2Mo Φ 280 mm x 1 000 mm, 480 kg ESR ingot and 60 piece hot die working steel H13 420 mm x 1 400 mm , 1 500 kg ESR ingot by optimized process have not been rejected due to ingot top shrinkage cavity defect, the ingot yield increases obviously.

Cu precipitated in feirite of 0.06C-0.40Cu bainite steel is kept with matrix in semi-coherent Kurdjumov-sachs relation, according to the theory of mismatch dislocation, with increasing temperature the calculated specific interfacial energy between ε-Cu and ferrite matrix increases, the coefficient of diffusion of Cu at 823 K is 1 000 times more than that at 723 K, and the ripening rate of ε-Cu increases approximately by 10 times. As ε-Cu precipitated size is 4.5 nm, ripening rate at 520 °C is 0.3127 nm-1/3, the ε-Cu particle size is 9.92 nm, yield strength of steel increases by 142.8 MPa.

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.

The test free-cutting stainless steel TBPS (/% : 0.02C, 0.75Si, 1.50Mn, 0.008P, 0.21S, 19.70Cr, 1.10Mo, 0.llPb, 0.008Te) is melted by vacuum induction furnace + electro-slag remelting (ESR)(Φ350 mm, 500 kg ingot) , and the relative hot plasticity of MnS inclusion in ESR ingot with deformation 10%-70% at 900-1200 °C has been tested and studied by Thermomechanical Simulator Gleeble 3800. The results show that at 900-1100 ℃ with increasing deformation the relative plasticity index γ of MnS inclusion decreases ； at 1200 °C the effect of deformation on the relative plasticity index γ of MnS inclusion is minor ； and with increasing the deformation temperature, the relative plasticity index γ of MnS trends towards decreasing, especially at 1200℃; the relative plasticity index γ decreases obviously. In order to decrease the elongation deformation of MnS to get better free-cutting performance, it available for steel TBPS to hot deform by larger pass deformation at higher temperature.

Based on prototype of steelworks 40t LF, by using the generalized similarity principle, experimental study on the 1:3 water simulation has been carried out. According to Buckingham's π theorem, a characteristic number equation model to describe the effect of mixing molten steel in bottom argon ladle is obtained. Through regression analysis of experimental data, a fitting equation to express mixing effect of stirred liquid in geometric similarity ladle is got. At the same time, the ANSYS CFX software is used to verify the optimal blowing position of the original blowhole and double blowholes. The result of experiment shows that with the argon bubbling at 2/3R distance from the center of bottom and using a single purging plug, the active zone of the ladle is largest and the stirring mixing time is the shortest.

Developmental 110SS steel Φ325 mm × 55 mm thick-wall seamless pipe ( /% ：0. 28 ~0.33C,0. 20 ~ 0.30Si, 0.60~1.00Mn, ≤0.015P, ≤0. 005S, 1. 20 ~ 1.45Cr,0. 65 ~0.85Mo,0.01 ~ 0.05Al, 0.01 ~0.05Ti, 0. 01 ~ 0. 05Nb,0. 01 ~0. 10V ) is produced by process of BOF-LF-RH-CC-ASSE1 rolling. By controlling BOF end point [C] ≥ 0. 03% , LF refining slag basicity 3. 0 ~4. 0, HR vacuum treating for ≥30 min, CC steel overheating ≤15 ℃ , continuous casting speed 0, 30 ~ 0. 50 m/min, steel pipe quenching temperature at 880 ℃ and tempering at 650 ℃ , the product inclusion size is less than 20 μm，yield strength is 760 ~820 MPa, at that time, the thick wall seamless steel pipe meets the requirements of hydrogen sulfide-proof.