The oriented silicon steel 0.04%-0.05% C, 3.03% -3.10% Si with yttrium contents of 0.026% , 0.058% and 0.14% are prepared in the laboratory by the 50 kg vacuum-induction furnace through conventional process. The composition, morphology, quantity, size and distribution of inclusions in steel are studied by SEM. The microstructure and texture of oriented silicon steel 2.4 mm hot rolled plate, 0.3 mm cold rolled sheet and a nnealed at 830 °C and 1050 °C are analyzed by OM and EBSD. The experimental results show that, with increasing Y content in steel, the size of inclusions be comes larger and the long-bar inclusions change to a spherical shape, their inhabitation becomes weaker. Therefore, the grain size after primary recrystallization gradually increases with increasing Y content. With Y content of 0. 026% silicon steel, the grain size after primary recrystallization is the smallest. The high storage energy of small grains provides a sufficient driving force for the high temperature annealing grain growth. Therefore, the average grain size after high temperature annealing is 115.7 μm, which is the largest. In the silicon steel with Y content of 0.026% , some Goss grains grow abnormally and Goss ( {110} ＜001＞) texture with strength of 5 appears, while a large amount of y texture still existed in silicon steel with Y content of 0.058% and 0.14%. Since the inclusion size in 0.026% Y steel is the smallest, it has a certain pinning effect, which makes the primary recrystallized grain finer. With the increase of Y content, the size of inclusions in 0.058% Y and 0.14% Y steel increase obviously, which weakens its inhibition on grain growth in the primary re crystallization process.

The effects of adding Ce(0-0. 32% ) -Mg(0-0. 04% ) alloy on the as-cast inclusions and solidification organization of GCr15 bearing steel are investigated. The results show that the addition of Ce-Mg alloy can lead to the modification of inclusions and the generation of a large number of Ce-and Mg inclusions with regular shape, fine size and disperssed distribution ；and the inclusions are more fine and diffuse as 0.016% [ Ce] and 0.002% [ Mg]. With the increase of the mass fraction of Ce-Mg alloy, the distribution of carbides in the as-cast structure of steel becomes more uniform and the reticular carbide network structure becomes thinner, and as 0.016% [ Ce] and 0. 002% [ Mg], the pearlite lamellae is the thinner and the lamellae spacing is the minimized. The addition of Ce-Mg alloy can significantly reduce the segregation of C and Cr elements between dendrites and dendrite stem, and reduce the dendrite spacing to hinder the coarsening of dendrites.

The 3% Si oriented silicon steel containing yttrium is prepared by 50 kg vacuum induction furnace with conventional production process and thin strip casting rolling process, respectively. The casting temperature of thin strip is 1 530 °C with rolling rate 0.3 m/s to 2.5 mm cast strip thickness. The conventional process silicon steel 80 mm cast billet heating temperature is 1 150 °C,hot rolled thickness to 2.4 mm with end rolling temperature 935 ℃.The composition, morphology, quantity, size and distribution of inclusions in steel are studied by scanning-type electron microscope (SEM) and electro-probe microanalyser (EPMA). The microstructure and texture of silicon steel strip, hot rolled plate, 0. 3 mm cold rolled sheet and 870 °C 7 min and 1 100 °C 10 min recrystallzing annealed sheet are analyzed by optical microscope (OM) and electron back-scattering diffraction (EBSD). The experimental results show that, compared with the conventional process, the grains of the thin strip cast rolled silicon steel after the first recrystallization are finer and the strength of 7 texture is 17 ； but the grain size is nonuniform after secondary recrystallization heal treatment, the average grain size is 61 μm, and the partial grain size of Goss orientation bigger than 1 mm. The reason is that the amount of fine yttrium inclusions is too large and the distribution is uneven, and the grain growth in the area where the inclusions gather is obviously inhibited. After secondary recrystallization heat treatment process, the grain size of the silicon steel of yttrium bearing produced by conventional process is uniformly and the average grain size is 102 μm, but the Goss texture is not formed.

Quality stainless steel 1. 4104 ( /% ：0. 16C,1. 23Mn,16. 40Cr,0. 41Ni,0. 43Mo,0. 023Ca ) for electro-hydraulic controller has been first melted at Daye Special Steel Co Ltd by 20 t electronic arc furnace and refined in ladle furnace and vacuum degassing unit, cast 1. 2 t ingot and forged into products. The transverse mechanical properties and machinability have been enhanced significantly by feeding bismuth cored wire（Bi：0. 036% ) and adding rare earth nodulizer (Ce： 0.054% ). Comparing with that of the free Bi-Ce steel, the total number of inclusion of the containing Bi-Ce steel decreases by 84. 4% and the number of MnS inclusion decreases by 85. 5% , average size of inclusion increases from 4. 5 μm to 13. 7 μm and cut force lower by 70～80 N with thicker and more easily broken chips, the transverse reduction of area increases from 3% to 17% .

he morphology of carbides and the thermoplasticity of high speed steel can be improved by inoculating with   rare   earth.   Test   and   batch   production   results   show   that   by   20t   MIF+25tLF+25tVD+4tESR   process,as   Al 0. 12%  in  steel  in  VD  process  adding  0. 1%  lanthannm-cerium  mixed  RE  alloy  and  using  6%  REO ₂  slag  series  in  ESR process,the  RE  content  in  M42  steel  is  0.027%～0.038%  stably  to  obviously  improve  inclusions  morphology  and  hot plastisity  of steel.

The recovery rate and distribution of rare earth elements with the condition of feeding rare earth wire in liquid in stainless steel continuous casting mould are studied by industrial test and numerical simulation. The results show that feeding rare earth wire into the mould has 85% rare earth recovery rate, but the content of rare earth near the solidified shell is relatively high and the distribution of rare earth is inhomogeneous (RE 0. 059% 〜0. 073% ) , which is due to the high concentration and inhomogeneous distribution of rare earth in mould liquid at early solidification period. Therefore, the influence of solidification transformation on the distribution of rare earth should be considered in the simulation or industrial production. In order to avoid the segregation of rare earth elements, the matching of rare earth wire diameter, wire feeding speed and continuous casting parameters should be paid attention to.

The ingredient and phases of solid phase slag without remelting liquid slag air cooling and with liquid-slag reaction remelting slag, air cooling of slag 70% CaF ₂-25% Al ₂O ₃-5% CaO for ESR of electrothermal alloy steel 0Cr21A16NbRE with normal remelting process (A =2800 A,V =30 V) are studied,and the burning loss of RE elements in liquid is analyzed. The results show that without remelting air cooling slag has not RE elements it locates in CaF ₂ -CaO • 2Al ₂O ₃-CaO • 6A1 ₂O ₃ sub-triangle. The solid phase slag with liquid-slag reaction can be divided into five layers with different colors, difierent phase, the content of CaF ₂ on the top is highest and decreases layer by layer, A1 ₂O ₃ increase simultaneously ,RE oxide is found in layers and at the middle and bottom its content is higher, (Ce,La)x( A10 ₂ )  y is major RE oxide phase in slag, which density is high. It is obtained by calculation that slag oxidability is stronger in the middle and bot¬tom of slag,RE element in steel is oxided here. Increasing the Y ₂O ₃ amount in slag is favourable to increase the RE element Y content in ESR ingot.

0.017% RE is fed in steel 30CrMnMo (/% : 0.31C, 0. 48Si, 1.44Mn, 0.011P, 0.001S, 1.20Cr, 0.71Mo, 0.040Als) at both side distance 500 mm from broad face center of 300 mm X 1950 mm slab mold. Analysis results show that the yield of RE is more than 95% , the distribution of RE in steel is uniform, the inclusions in steel is modified and most inclusions are spheroidal; as compared with quenched-tempered non-adding RE steel 30CrMnMo, the impact energy ( KV2) at -40℃ of quenched-tempered 60mm plate steel 30CrMnMo containing 0.017% RE increases from 50.9~56.6 J to 77.6~81.6 J.

The tested stainless steel 409L (/% : 0.01C, 0. 82 ~0. 86Si, 0. 26Mn, 0.002 ~0.006S, 0. 034 ~0.041P, 11.44 ~ 11. 51Cr, 0. 24 ~0. 27Ti, 0 ~0. 09Ce) is melted by a 10 kg vacuum induction furnace, forged to 30 mm x 30 mm square billet, cold rolled to 2 mm plate and annealed at 1100 ℃ for 5 min. The effect of Ce on structure annealed at 900℃ for 30 min and on thermal fatigue performance between 900 °C and ambient temperature in steel 409L has been studied. Results show that as the steel contains 0. 03%Ce, the annealed grain of steel 409L is fined and the thermal fatigue performance is best, as the Ce content in steel further increases, the annealed grains coarsen and the thermal fatigue performance of steel gradually decreases. With adding RE element Ce the TiN and TiN-Al ₂O ₃ compound inclusions basically eliminate and the fined spherical titanium-nitrogen compound inclusions bearing Ce and Al-O-Ti compound inclusions bearing Ce form, and adding excessive Ce, the amount of inclusions at grain boundary increases led to decrease the thermal fatigue performance of steel.

Tested 30Fe-70La alloy is melted by a high frequency suspending melting furnace and cut to 8 mm x 8 mm x6 mm specimen and butted on same size pure iron specimen, then the diffusion test is carried out at 10 ^-3 Pa vacuum and 1 MPa pressure at 760℃ and 770℃ 30 min by Gleeble-1500D hot simulation experiment machine； the diffusion of rare earth element lanthanum in Fe matrix is observed by Axiovert 25 optical microscope and QUANTA 400 environmental scanning electron microscope, and the diffusion coefficient of lanthanum in pure iron is calculated by relative diffusion coefficient formulas. Results show that the diffusion of rare earth element lanthanum in pure iron is carried out along a-Fe grain boundaries, and the diffusion coefficient Db of lanthanum in grain boundaries of pure iron ferrite is 1. 59 x 10 ^-17m ²/s.

The test new type steel 616 containing Ce (/% : 0. 23 ~0. 25C, 0.73 - 0. 78Si, 1. 64 ~ 1. 70Mn, 0.003 ~0.005S, 0.016-0.020P, 0.051 ~0.061Ti, 0. 026 ~0.028Nb, 0.002 0 -0.0030B, 0~0.302Ce) is melted by a 10 kg vacuum induction furnace, rolled to 5mm thickness plate, water-quenched at 900 ℃. and tempered at 600 °C. The effect of Ce content in steel on structure and mechanical properties of plate of steel 616 has been studied by universal tensile testing machine, optical microscope, scanning electron microscope etc experimental instrument. Results show that as the Ce content in steel is 0. 096% , the refinement of grain in plate of steel 616 is obvious and the sulphide in steel is modified from long strip to spheroid, it is available to increases the tensile strength and toughness of steel plate, the tensile strength of 0. 096% Ce plate increases to 779 MPa from 681 MPa of non-adding Ce plate ； as the Ce content further increases the more refinement of grain in plate is not obvious and the amount of inclusions in steel increases, with Ce content 0. 302% the tensile strength of plate decreases to 712 MPa.

Test pipeline steel (/%： 0.04-0.05C, 0.20-0.24Si, 1.80-1.88Mn, 0.010-0.012P, 0.004-0.005S, 0.27-0.30Cr, 0.42-0.46Ni, 0.24-0.28Mo, 0.20Cu, 0.005V, 0-0.017Y, 0.0031 -0.0053O) is melt by a 10 kg induction furnace and rolled to test bar. The effect of rare earth yttrium on corrosion resistance of pipeline steel in simulated seawater (3.5% NaCl) is studied by using scanning electron microscope and energy spectrum analysis, electrochemical techniques and thermodynamics calculated method. Results show that the rare earth has modification effect on inclusions in steel to modify the large scale and spinel structure Al ₂O ₃ inclusions to small spheroidal rare earth compound inclusions； therefore it is favorable to form the continuous and compact inner rust layer, decrease the pitting corrosion source and increase the corrosion resistance of steel.

The austenite stainless steel 204Cu (/% : 0.125-0.131C, 0.32-0.34Si, 8.51-8.73Mn, 0.002-0.006S, 0.035-0.047P, 16.40-16.64Cr, 2.53-2.72Ni, 2.33-2.38Cu, 0.257-0.271N, 0-0.064Ce) is melted by a 10 kg vacuum induction furnace, forged to 25 mm x 25 mm square billet, and solid-solution-treated at 1150 ℃ for 2 h, water cooling. The effect of 0-0.064% Ce on corrosion-resisting properties of stainless steel 204Cu in 3.5% NaCl solution at 25 ℃ has been studied by using weight method, electrochemical polarization curves and AC impedance techniques. Results show that adding definite earth element Ce in stainless steel 204Cu, the anod polarization voltage value shifts positively ,the corrosion current density decreases and the polarization resistance increases , that can obviously increase its corrosion-resisting properties, as adding 0.029% Ce the stainless steel 204Cu has optimizing corrosion-resisting properties.

The effect of adding La alloying methods on yield of La in stainless steel Fe-20Cr-5Al (/%: 0. 004 ~ 0. 006C, 0. 18Si, 0. 08Mn, 20.25 ~ 20. 28Cr, 5. 06 ~5. 17Al) melting by 50 kg vacuum induction furnace + electroslag remelting process has been studied. Results show that with vacuum induction furnace (VIF) melting Fe-20Cr-5Al electrode (parent alloy) + rare earth (RE) oxide La ₂O ₃ (/%: 50CaF ₂-20CaO-30La ₂O ₃) electroslag remelting (ESR) for La alloying, the average La content in steel is 0. 003%, indicated it is not obvious to La alloying by adding RE oxide during ESR； with VIF La alloying melting ESR electrode (0. 38% La in steel) + 70% CaF ₂-30% Al ₂O ₃ electroslag remelting, the average La content in ESR steel is 0. 066%, and with VIF La alloying melting ESR electrode (0. 34% La in steel) + 50% CaF ₂- 20%CaO-30La ₂O ₃ electroslag remelting, the average La content in ESR steel is 0. 032%, It is indicated that during ESR process of containing La parent alloy the oxidizing loss of La is larger, but as compared 30% La ₂O ₃ remelting slag the 30% Al ₂O ₃ remelting slag is more favorable to decrease the oxidizing loss of La in-parent alloy during ESR process.

The test interstitial-free steel IF(/% : 0.0036-0.0049C, 0.005-0.007Si, 0.11-0.12Mn, 0.007P, 0.005S, 0.007-0.011Alt, 0.047-0.051Ti, 0.0030N, 0-0.0037Ce) is melted by a 10 kg vacuum induction furnace, and forged to 30 mm x 25 mm billet, finishing forging at 950 ℃ , air cooling. With using Gleeble-1500D thermal simulation testing machine the tensile test on the testing steel with strain rate 0. 1 s ^-1 at 750-1150 ℃ has been carried out to study the effect of micro rare earth (RE) element Ce on high temperature tensile properties of the IF steel. As compared with IF steel non-containing Ce, the hot plasticity ( reduction of area-Z value) and hot tensile strength ( Rm value) of IF-Ce steel containing 0. 0037%Ce increase obviously, but with increasing temperature the increment decreases ； the reduction of area and tensile strength at elevated temperature of IF steel and IF-Ce steel respectively are 77.62% -110 MPa for IF and 88.65%-160 MPa for IF-Ce at 750 °C ； 87.35% -85 MPa for IF and 92.88% -100 MPa for IF-Ce at 950 ℃: and 85.68% - 55 MPa for IF and 90.62% -58 MPa for IF-Ce at 1150 °C. The main reasons to increase hot plasticity and hot tensile strength of IF steel by adding RE element are that the element Ce improves structure of steel, fines grain size, and segregates and clusters at grain boundary to increase the strength of grain boundary.

Test normal A36 steel and containing Ce A36Ce steel for shipbuilding (/% : 0.12-0.13C, 0.21 Si, 0.77-0.79Mn, 0.013-0.015P, 0.003-0.004S, 0.32-0.33Cr, 0.023-0.025Al, 0-0.009Ce) are melted by vacuum induction furnace, cast to 7 kg ingot, forged to 25 mm x 25 mm billet and normalized at 865 °C for 0. 5 h. The corrosion rate, corrosion surface morphology and features of rust layer of both normal non-containing Ce A36 steel plate for ship building and containing 0.009% Ce A36Ce plate for shipbuilding are analyzed by full immersion examination in simulated seawater (3. 5% NaCI) environment with using weight loss, electrochemical method, scanning electron microscope and X- ray diffractometry. Results show that in seawater for 30 day, the corrosion rate of A36 steel plate for shipbuilding is 1.8 g/ (mm ² • day) , while that of A36Ce steel plate for shipbuilding is 1.2 g/( mm ² • day) ； the A36Ce steel plate is easily to form denser black inner rust layer which is not easily to peel off ； the pitting corrosion tendency of nonnal A36 steel plate is more severe, but the uniform corrosion of A36Ce steel plate is primary ； the corrosion products of both steels are iron oxide and carbonyl.