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Based on the need of high wear resistance， a new kind of high-vanadium high-speed steel named W3Mo4Cr5V6 was designed. The transformation behavior of metastable M2C carbides in the high temperature heating process of the steel was analyzed by means of SEM and EMPA. The results show that the cophortic M2C carbide will undergo M2C+γ-Fe→M6C+MC+M7C3 transition at high temperature heating process.A large number of W， Mo-rich M6C and a small amount of V-rich MC and Cr-rich M7C3 are formed around the Mo and W-rich M2C phase. With the increase of temperature from 950 ℃ to 1 150 ℃， the high temperature transformation of M2C carbides gradually tends to be complete and the fibrous M2C is easier to decompose and transform than lamellar M2C， and the lamellar or fibrous morphology distributed in the austenite grain boundary with discontinuous network is transformed into the granular morphology distributed at the grain boundary， which can effectively reduce the harm of network carbides to the grain boundary. The research can provide an effective reference for the composition and morphology control of carbides distributed at the grain boundaries of high-speed steel and the optimal selection of parameters such as temperature and time of hot processing and heat treatment process.

The effects of Ti microalloying on the microstructure and mechanical property of Mn18 steel were studied， and the reasons for the failure of Mn18 hammer heads were analyzed. The results show that Ti microalloying has the effects of refining grain， increasing impact toughness， elongation， strength and hardness in Mn18 steel. When 0.10% and 0.30% w［Ti］ are added to Mn18 steel， as the Ti content increases， the hardness and strength of high manganese steel increase，and the impact toughness and elongation also show an optimization trend. When it continues to increase Ti to 0. 51%， in addition to the continuous increase of Brinell hardness， the KU2 value and stability， strength stability， the elongation and other indicators all have a downward trend. High manganese steel belongs to high nitrogen austenitic steel， and after adding Ti， a large amount of TiN is rapidly precipitated as a heterogeneous core， playing a series of beneficial roles. If the addition amount is too large， the size of TiN type inclusions is too large and local aggregation occurs， which has a negative impact on the performance stability of Mn18 and is easily prone to fracture and failure of Mn18 steel hammer heads. To ensure its beneficial effect， the content of Ti microalloying used in Mn18 steel should not exceed 0.30%.

In the present study, the comprehensive analyses based on the numerical simulation, in situ observation, and metallographic detection were carried out for the roll core of GCr15/45 carbon steel composite roll manufactured by the new electroslag remelting cladding (ESRC) method. During the ESRC process, the temperature distributions at the different radial and longitudinal positions of the roll core have great changes due to the different degrees of heat conduction from the slag bath, as a result, various microstructure and properties were obtained at the different positions of the roll core. The results illustrated that the ESRC process tended to be stable as the composite height reached a certain value and the high-temperature austenitization process mainly occurred in the radial regions where R > 60 mm, whereas no significant changes occurred at the areas where R ≦ 60 mm. The coarse grains and few Widmanstatten structures with proeutectoid ferrite were generated in the roll core areas near the bimetallic interface, while the fine grains with more proeutectoid ferrite were obtained in the roll core area away from the interface. Therefore, a higher tensile strength and a better plasticity were obtained for the specimens away from the interface.

Niobium has the potential as an inhibitor forming element in grain oriented silicon steel. The grain oriented silicon steels with different Nb contents (0.028 wt% and 0.052 wt%) were prepared, and the effect of Nb content on the evolution of precipitates, microstructure and texture were investigated by the various analysis methods and thermodynamic calculations. The results show that the smaller size and larger number density of precipitates were obtained in the sample with low Nb steel after hot rolling. In the process of normalization, Nb(C, N) are more inclined to precipitate along the dislocations caused by hot rolling, contributing to finer and more dispersed precipitates in normalized bands. The finer and more dispersed precipitates in 0.028% Nb containing silicon steel perform a stronger pinning force during whole heat treatment processes, resulting in the smaller grain size and higher intensity of Goss texture in the specimen containing 0.028%Nb. After normalization, the intensities of Goss texture in both steels decrease.

Three dual alloy ingots were processed by electroslag remelting with 1500 A, 1800 A and 2100 A. The compositions and inclusions of ingots were analyzed by means of various analytical techniques. The results show that the segregation becomes severer with the increase of current. With the current increasing, the proportion of inclusions with large size, the T.[O] and sulfur content in the ingot increase, showing a worse cleanliness due to the severer electrode surface oxidation and shorter interaction time between slag pool and film of molten steel at the electrode tip. The single (Mn,Cr)S inclusion can precipitate in transition zone of each ingot and NiCrMoV zone of ingot with 1800 A and 2100 A due to higher sulfur content and the solute segregation during solidification. The ingot processed by ESR with 1500 A performed a balanced quality.

The preparation of FePO4 as a precursor by co-precipitation method is widely used, Due to the lack of the guidance of thermodynamic theory, The prepared FePO4 often contains impurity phase, which leads to unsatisfactory performance of LiFeO4. The E-pH diagram of Fe-P-H2O system at the temperature of 25℃ were drawn through the basic E-pH principle with a number of thermodynamic data. According to the E-pH Diagram, the pH value is approximately 2.5, and the FePO4 with less impurity can be prepared by adding proper oxidant. Base on the above mentioned condition, a simple verification experiment was carried out. The results showed that the prepared iron FePO4 had fewer impurities, which provided a theoretical basis for preparing high-performance LiFeO4.

To clarify the interaction mechanism between distinct tundish gunning materials (GM) and liquid steel, two kinds of gunning materials, namely MgO, Al2O3 GM, were tested. SEM, EDS, XRD and chemical analysis were carried out for steel and GM to investigate the change of chemical composition of steel in contact with GM and the interface microstructure between steel and GM after high temperature holding experiments. The steel cleanliness in terms of inclusion number density, size and size distribution was evaluated. It was found that the reducible component, low-melting-point phases and the pores in GM were passageway for steel penetration. The Al2O3 GM was less prone to steel penetration due to its poor wetting and the dense transition layer. MgO GM provided more oxygen and showed a stronger oxidizing capacity due to its higher content of reducible oxides (10.5 wt.% SiO2+2 wt.% Fe2O3). The use of Al2O3 GM resulted in an improved steel cleanliness and consequently could be a promising refractory in the tundish lining.

A series of ZrO₂-MgAl₂O₄ ceramics with additions of 0, 2.5wt%, 5.0wt% and 7.5wt% nano-ZrO₂ were successfully fabricated at 1580 °C for 4 h from powders of commercial Al₂O₃ and calcined MgO by single-stage solid state reaction sintering (SRS) method. Effects of nano-ZrO₂ additive on the phase compositions, microstructures and bulk density of the ceramics were investigated. Nano-ZrO₂ additive was found to remarkably promote the sintering densification and improve the microstructure of the ceramics. Uniform, dense and fine microstructures are obtained, and the mean grain size of MgAl₂O₄ particles is about 2 μm. The as-prepared ceramics mainly consist of MgAl₂O₄ and c-ZrO₂ (cubic-Ca0.15Zr0.85O1.85), due to the reaction between Al₂O₃ and MgO as well as the nano-ZrO₂ additive and CaO stabilizer. The formation process of the ceramics mainly includes the synthesis of MgAl₂O₄ and the conversion process of m-ZrO₂ to c-ZrO₂ under the stabilizing action of CaO.

MgAl2O4 (MA)-Y3Al5O12 (YAG) and MA-MgNb2O6 (MN) ceramics with high density were successfully fabricated via a single-stage solid-state reaction sintering (SRS) process at 1580°C for 4 h. The effect of Y2O3 or Nb2O5 additions from 2.5 wt% to 7.5 wt% on the phase compositions, microstructures, shrinkage ratio, apparent porosity, bulk density and cold compressive strength of MA-YAG and MA-MN ceramics has been investigated. It was found that MgO and Y2O3 reacted with Al2O3 to form MA and YAG during sintering while Nb2O5 reacted with MgO to form MN. YAG and MA grains in the MA-YAG ceramics exist as granular shape, and their average grain size is about 1 μm and 5 μm, respectively. YAG grains distribute on the intergranular space of MA particles. Polygonal MA particles can be observed in the MA-MN ceramics, and MN grains distribute on the intergranular space of MA particles as well as on MA particles. Rod-like MN grains can be formed in the MA-MN ceramics by addition of 7.5 wt% Nb2O5. The diameter shrinkage ratio, volume shrinkage ratio, bulk density and cold compressive strength of MA-YAG and MA-MN ceramics are greatly improved by doping Y2O3 and Nb2O5, respectively.

Stoichiometric magnesium aluminate spinel (MgAl2O4, MA)-samarium aluminate (SmAlO3, SA) ceramics have been prepared at 1580oC for 4 h from calcined magnesia (MgO), commercial alumina (Al2O3) and samarium oxide (Sm2O3) by a single-stage in-situ reaction sintering (SIRS) method. The phase compositions, microstructures, shrinkage ratio, bulk density and cold compressive strength of the MA-SA ceramics have been investigated. The ceramics with 2.5 - 7.5 wt. % Sm2O3 are composed of MA and SA phases. The microstructures of the ceramics are dense. MA particles exist as angular shape, and their grain size varies between 2 and 10 μm but the average grain size is about 5 μm. SmAlO3 particles form due to the reaction of Sm2O3 and Al2O3, and they distribute in the intergranular space of MA grains. The diameter shrinkage ratio, volume shrinkage ratio, bulk density and cold compressive strength of MA-SA ceramics are greatly improved due to the addition of Sm2O3