In order to reduce the harm of B-type and D-type inclusions in Al deoxidized GCr15 bearing steel， a comparative industrial experimental study was conducted on refining VD low alkalinity slag and normal alkalinity slag. The results showed that when refining slag alkalinity was reduced from 9.34 to 1.96， the proportion of plastic inclusions in the steel increased from 14.81 % to 40.65 %. As the same time， the content of total oxygen （T. O） decreased from 7.7 × 10 ^-6 to 4.9 × 10 ^-6； the content of total aluminum （T. Al） and acid-soluble aluminum （Al _S） decreased from 279 × 10 ^-6 and 210 × 10 ^-6 respectively to 80 × 10 ^-6 and 75 × 10 ^-6. Thermodynamic calculation shows that the increase of ［Si］ activity in the liquid steel causes the decrease of Al ₂O ₃（inc） content in the composite inclusion， and the acid soluble aluminum （Al _S） content in the steel falls within the range of equal aluminum concetration lines corresponding to plastic inclusions， the theoretical calculations are consistent with experimental results. The VD refining with low basicity slag is beneficial for achieving control over the plasticization of inclusions in bearing steel.

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.

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 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.

Focusing on the characteristics of rolling bearings, the types of bearing steels, and the gap between bearing steels at home and abroad, this paper summarizes the art of the status of the requirement of the bearing steel of the high-end equipment, the types of the bearing steels, the processing equipment and metallurgical quality of the bearing steels, the heat treatment technologies, and the evaluation technologies for both metallurgical quality and performance. It is put forward that the important role to improve the rolling contact life of the bearing steel by ultra-purification technologies among different melting routes, the new heat treatment technologies and the new bearing steel developments. This paper pointed out that it needs to be done in the future through the refinement, the homogenization and the stabilization of the inclusions, carbides and the matrix of the bearing steel to improve the quality and performance of existing bearing steels, to develop the high performance heat treatment technologies, to innovate the high performance bearing steel and to strengthen the basic research on the mechanism of the fatigue-resistance of the bearing steels, which would finally enhances the rolling contact fatigue life of the bearing steel significantly.

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.

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.

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 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  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 microstructure and micro-hardness of typical non-quenched and tempered steel 38MnSiVS5 ( /% : 0. 37C,0. 78Si,0. 012P,0. 045S,0. 03Mo,0. 120V,0. 004Nb,0. 003Ti) are analyzed by using thermal dilatometer, optical microscope and Vickers hardness tester. The continuous cooling transformation ( CCT ) curves of supercooled austenite are tested. The results show that the CCT curve of steel 38MnSiVS5 could be divided into high temperature transition region, middle temperature transition region and low temperature transition region. With cooling rate ≤0.89 ℃/s, the high temperature transition region is formed with microstructure ferrite and pearlite; With the cooling rate 1.78 ～4.45 ℃/s, the high temperature transition region and middle temperature compound transition region is formed with microstructure ferrite, pearlite and bainite; as the cooling rate up to 8. 9 ℃/s, the high temperature transition region, middle temperature transition region and low temperature transition region are formed with microstructure ferrite, pearlite, bainite and martensite; as the cooling rate up to 17. 8 ℃/s, the F + P structure disappears,the middle temperature transition region and low temperature transition region are formed, the microstructure is bainite and martensite; as the cooling rate ≥44.5 ℃/s, the microstructure is martensite. With the increase of cooling rate from 0. 06 to 44. 5 ℃/s, the HV5 micro-hardness number of 38MnSiVS5 steel increased from 213 to 568.

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.

Cr12MoV flat steel mainly adopts the long process of die casting ingot， multi-fire forging and rolling， which has low production efficiency， low yield， high cost and high energy consumption. In order to solve the problems of poor thermal conductivity and ductility of cold working die steel， a short process of 90 t EBT-LF-VD-150 mm×630 mm continuous casting rectangular billet and one-fire heating +15-pass rolling was designed. The rectangular continuous casting billet and rolled 19 mm thick flat steel products of Cr12MoV steel were successfully developed， continuous casting center porosity 1.5 grade， center segregation ≤1.0， the finished flat steel eutectic carbide unevenness level ≤3， the defects inspection quality grade reaches grade A， and the performance indexes meet the standard requirements. Cr12MoV cold working die steel products have achieved mass production and achieved good economic benefits.

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.

Serious white spots defect occurs on the surface of (4.4～4.6) mm×2050 mm wide-thick cold rolled strip of 316L stainless steel (/%:0.02C,17. 12Cr,10. 15Ni,2.06Mo) for tank container in production process. The causes of the white spots are researched by means of feature analysis, steels grades comparison and on-site defect tracking, the results show that there is much emulsion on the surface of cold rolled strip, on which the formed oxide scale is unevenly distributed in case of incompletely degreasing and annealing at 980 ℃,the color of the oxide scale on the surface with much emulsion is white, these white oxide scales are changed into white spots after pickling. Besides, the influencing factors of the residu al emulsion on the surface of rolled strip and the removal effect of residual emulsion are systematically studied. By applying oil scraping system for nonwoven-fabric roller, adding air knife purging system, controlling emulsion concentration 1.5%~ 3% and temperature(55±3)℃,repairing two sets of magnetic filtration system in rolling process, through controlling de- greasing electrical conductivity7.5 μs/cm and loop filling speed 50 m/min,adjusting9～12 area Furnace temperature to 1030 ℃,the unqualified rate of white spots is reduced from 10% to 0.5% or less.

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.

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.

Abstract In order to meet the user requirement to derease the hardness of 18Cr2Vi4WA steel Φ 60 mm product i. e. HBW hardness value ≤269 ,the tempering test at 630 〜750 °C for 5 h, furnace cooling to 500 °C ,air cooling have been tested by bottom roller annealing furnace and by the help of metalloscope to analyze annealing shape of 18Cr2Ni4WA steel with different temperature. The result show that 18Cr2Ni4WA tempering hardness is connected with temperature, with the increase of annealing temperature, the hardness dacreases first and then increases. When tempering temperature is 670°C ，the HBW average hardness of steel products is the lowest( adout HBW238 ) and the structure is uniform spheroidized pearlite.