Geochemical characteristics of trace and minor elements in some strata of geosynclinal tectonic layer, platform tectonic layer, in granite of Diwa stage, altered rocks and wolframite in the Xiangdong Tungsten Mine are...Geochemical characteristics of trace and minor elements in some strata of geosynclinal tectonic layer, platform tectonic layer, in granite of Diwa stage, altered rocks and wolframite in the Xiangdong Tungsten Mine are systematically studied. Enrichment of W, Sn and Cu in geosynclinal tectonic layer could be one part of mineralization. Different types of alteration might result in variance of distribution of the same trace or minor element. mNb/mTa and mMn/mFe ratios, contents of Nb and Ta in wolframite vary with vein groups′ location.展开更多
The microstructures of doped tungsten deformed by multi-pass hot continuous rolling were investigated, and the stress and strain fields were simulated by finite element(FE) method. After the continuous rolling, the gr...The microstructures of doped tungsten deformed by multi-pass hot continuous rolling were investigated, and the stress and strain fields were simulated by finite element(FE) method. After the continuous rolling, the grains of the tungsten rod were refined, and the microhardness was improved; however, a ring region of abnormal grain growth was present at a distance of about 3/5 R(R is the radius of the rod) from the center of the cross section. FE modeling results showed that the equivalent residual strains were minimum around the region of abnormal grain growth; this was due to the release of strain energy by severe plastic deformation, leading a situation where the migration force of grain boundaries was higher than the pinning force of potassium bubbles. By decreasing the initial rolling temperature and rolling speeds, the inhomogeneity of the equivalent residual stain decreased, improving the microstructure uniformity of the doped tungsten.展开更多
90W-7Ni-3Fe and (90-x)W-xTa-7Ni-3Fe (x=1,3,5,7,10) specimens were attained by liquid phase sintering. A model describing the process of liquid forming and spreading was proposed to point out the differences between al...90W-7Ni-3Fe and (90-x)W-xTa-7Ni-3Fe (x=1,3,5,7,10) specimens were attained by liquid phase sintering. A model describing the process of liquid forming and spreading was proposed to point out the differences between alloys doped with tantalum and traditional tungsten heavy alloys. Tantalum priority of entering matrix and a relative high solubility in liquid matrix depress tungsten solubility in liquid matrix, which decreases kinetic rate constant K and consequently results in the reduction of W grain size. The grain refinement is influenced by Ta content and becomes more obvious when Ta content is over 5%. The sample with less than 3%Ta has dominant W and matrix phases. While besides W and matrix phases, intermetallic phases emerge in 85W-5Tai-7Ni-3Fe sample. Ta is superfluous and forms a new tantalum phase when more than 7% Ta is added into alloys.展开更多
The mechanical and corrosion performance of low alloy steel tubular goods depends on the microstructure obtained as a result of the combination of alloying elements and manufacturing process parameters. The basic desi...The mechanical and corrosion performance of low alloy steel tubular goods depends on the microstructure obtained as a result of the combination of alloying elements and manufacturing process parameters. The basic design philosophy for the selection of the alloying elements is ruled by the balance between the steel cost and the material performance.Following this approach the alloying sequence for the manufacturing of tubular components in oil country tubular goods(OCTG) application is generally Mn,C,r and Mo,used as substitutional elements in a total added weight concentration around 1%up to 3%.Other elements such as B,Ti,Nb and V are applied as strengthening microalloying elements forming fine precipitates. A lack of experience is found related to the use of Tungsten(W) on OCTG applications,although W is also a substitutional element that belongs to group 6 of the periodic table together with Cr and Mo.On the other hand W is widely added for steel pipes working in high temperature services such as power plant boilers,where creep resistance is needed.It is also applied for tool steels enhancing the hardness,wear resistance and cutting performance. Taken into consideration the similarity between Cr,Mo and W and the applications where W has been proven it was decided to analyze the feasibility of using W as an alternative alloying element for some OCTG applications. Another factor that drives this study is the fact that W could be a cost effective substitute of Mo,depending on the alloy market price. This paper is based on literature review and experimental activity done on laboratory steels in which 0.1%Mo was replaced by 0.2%and 0.4%W.The different findings in regards with manufacturing process considerations, material performance and the possible use of W alloyed steel for OCTG applications are summarized. (1 ) Opposed to the susceptibility shown by low carbon with high Cr-W content,hot cracks are not expected in medium C steels(0.2%-0.3%) with W addition up to 1%. (2) Microporosity-related defects could form if W <<0.4%. (3) An improvement in the oxidation resistance for typical rolling furnace atmospheres in the temperature range 1 200 - 1 340℃was detected if Mo is substituted by W. (4) Theoretically W is one half less efficient in regards with hardenability. (5) No differences were found in the grain size after austenitizing in the temperature range 920 - 1 050℃, independently on Mo and W contents. (6) Tempering resistance was similar to Mo steels and there was no effect on the cementite shape factor,which affects the performance in sour environments. (7) Both pitting and general corrosion resistance are improved by W addition.But W effectiveness in improving pitting resistance is about one half. (8) The use of W as a substitute of Mo has been proven to be feasible and it could be applied for the manufacturing of N80 or L80 OCTG steel grades as per ISO 11960/API 5CT.展开更多
Marinov et al. have detected spontaneous fission events in sources separated from tungsten targets irradiated with 24 GeV protons. These fission events could not be attributed to actinides or to any other known isotop...Marinov et al. have detected spontaneous fission events in sources separated from tungsten targets irradiated with 24 GeV protons. These fission events could not be attributed to actinides or to any other known isotope. Marinov et al. propose that fission events are due to production of element 112 (Eka-Hg) in the tungsten target. We have addressed Marinov’s claim with a new analysis of their data and modern theoretical model calculations of possible interactions. Using data available in the literature the spontaneous fission half-life of the Eka-Hg was estimated to be ~74 days. This is dramatically longer than the half-life obtained for 283112Cn, produced in the fusion of energetic 48Ca ions with 238U. Monte Carlo calculations show that enough Sr isotopes are produced in the tungsten target to make the production of element 112 via fusion of Sr and W feasible;however, if such fusion was possible it had to be deep sub-barrier fusion.展开更多
The flow behavior of feedstock for the tungsten alloy powder in the mold cavity was approximately described using Hele-Shaw flow model. The math model consisting of momentum equation, consecutive equation and thermo-c...The flow behavior of feedstock for the tungsten alloy powder in the mold cavity was approximately described using Hele-Shaw flow model. The math model consisting of momentum equation, consecutive equation and thermo-conduction equation for describing the injection process was established. The equations are solved by the finite element/finite difference hybrid method that means dispersing the feedstock model with finite element method, resolving the model along the depth with finite difference method, and tracking the movable boundary with control volume method, then the pressure equation and energy equation can be resolved in turn. The numerical simulation of the injection process and the identification of the process parameters were realized by the Moldflow software. The results indicate that there is low temperature gradient in the cavity while the pressure and shear rate gradient are high at high flow rate. The selection of the flow rate is affected by the structure of the gate. The shear rate and the pressure near the gate can be decreased by properly widening the dimension of the gate. There is a good agreement between the process parameters obtained by the numerical simulation and the actual ones.展开更多
文摘Geochemical characteristics of trace and minor elements in some strata of geosynclinal tectonic layer, platform tectonic layer, in granite of Diwa stage, altered rocks and wolframite in the Xiangdong Tungsten Mine are systematically studied. Enrichment of W, Sn and Cu in geosynclinal tectonic layer could be one part of mineralization. Different types of alteration might result in variance of distribution of the same trace or minor element. mNb/mTa and mMn/mFe ratios, contents of Nb and Ta in wolframite vary with vein groups′ location.
基金financially supported by Shandong Provincial Key Research and Development Program, China (No. 2017GGX20140)Shandong Provincial Natural Science Foundation, China (Nos. ZR2014JL031 and ZR2018MEE016)
文摘The microstructures of doped tungsten deformed by multi-pass hot continuous rolling were investigated, and the stress and strain fields were simulated by finite element(FE) method. After the continuous rolling, the grains of the tungsten rod were refined, and the microhardness was improved; however, a ring region of abnormal grain growth was present at a distance of about 3/5 R(R is the radius of the rod) from the center of the cross section. FE modeling results showed that the equivalent residual strains were minimum around the region of abnormal grain growth; this was due to the release of strain energy by severe plastic deformation, leading a situation where the migration force of grain boundaries was higher than the pinning force of potassium bubbles. By decreasing the initial rolling temperature and rolling speeds, the inhomogeneity of the equivalent residual stain decreased, improving the microstructure uniformity of the doped tungsten.
文摘90W-7Ni-3Fe and (90-x)W-xTa-7Ni-3Fe (x=1,3,5,7,10) specimens were attained by liquid phase sintering. A model describing the process of liquid forming and spreading was proposed to point out the differences between alloys doped with tantalum and traditional tungsten heavy alloys. Tantalum priority of entering matrix and a relative high solubility in liquid matrix depress tungsten solubility in liquid matrix, which decreases kinetic rate constant K and consequently results in the reduction of W grain size. The grain refinement is influenced by Ta content and becomes more obvious when Ta content is over 5%. The sample with less than 3%Ta has dominant W and matrix phases. While besides W and matrix phases, intermetallic phases emerge in 85W-5Tai-7Ni-3Fe sample. Ta is superfluous and forms a new tantalum phase when more than 7% Ta is added into alloys.
文摘The mechanical and corrosion performance of low alloy steel tubular goods depends on the microstructure obtained as a result of the combination of alloying elements and manufacturing process parameters. The basic design philosophy for the selection of the alloying elements is ruled by the balance between the steel cost and the material performance.Following this approach the alloying sequence for the manufacturing of tubular components in oil country tubular goods(OCTG) application is generally Mn,C,r and Mo,used as substitutional elements in a total added weight concentration around 1%up to 3%.Other elements such as B,Ti,Nb and V are applied as strengthening microalloying elements forming fine precipitates. A lack of experience is found related to the use of Tungsten(W) on OCTG applications,although W is also a substitutional element that belongs to group 6 of the periodic table together with Cr and Mo.On the other hand W is widely added for steel pipes working in high temperature services such as power plant boilers,where creep resistance is needed.It is also applied for tool steels enhancing the hardness,wear resistance and cutting performance. Taken into consideration the similarity between Cr,Mo and W and the applications where W has been proven it was decided to analyze the feasibility of using W as an alternative alloying element for some OCTG applications. Another factor that drives this study is the fact that W could be a cost effective substitute of Mo,depending on the alloy market price. This paper is based on literature review and experimental activity done on laboratory steels in which 0.1%Mo was replaced by 0.2%and 0.4%W.The different findings in regards with manufacturing process considerations, material performance and the possible use of W alloyed steel for OCTG applications are summarized. (1 ) Opposed to the susceptibility shown by low carbon with high Cr-W content,hot cracks are not expected in medium C steels(0.2%-0.3%) with W addition up to 1%. (2) Microporosity-related defects could form if W <<0.4%. (3) An improvement in the oxidation resistance for typical rolling furnace atmospheres in the temperature range 1 200 - 1 340℃was detected if Mo is substituted by W. (4) Theoretically W is one half less efficient in regards with hardenability. (5) No differences were found in the grain size after austenitizing in the temperature range 920 - 1 050℃, independently on Mo and W contents. (6) Tempering resistance was similar to Mo steels and there was no effect on the cementite shape factor,which affects the performance in sour environments. (7) Both pitting and general corrosion resistance are improved by W addition.But W effectiveness in improving pitting resistance is about one half. (8) The use of W as a substitute of Mo has been proven to be feasible and it could be applied for the manufacturing of N80 or L80 OCTG steel grades as per ISO 11960/API 5CT.
文摘Marinov et al. have detected spontaneous fission events in sources separated from tungsten targets irradiated with 24 GeV protons. These fission events could not be attributed to actinides or to any other known isotope. Marinov et al. propose that fission events are due to production of element 112 (Eka-Hg) in the tungsten target. We have addressed Marinov’s claim with a new analysis of their data and modern theoretical model calculations of possible interactions. Using data available in the literature the spontaneous fission half-life of the Eka-Hg was estimated to be ~74 days. This is dramatically longer than the half-life obtained for 283112Cn, produced in the fusion of energetic 48Ca ions with 238U. Monte Carlo calculations show that enough Sr isotopes are produced in the tungsten target to make the production of element 112 via fusion of Sr and W feasible;however, if such fusion was possible it had to be deep sub-barrier fusion.
基金Project([2006]112) supported by the Transformation of the Scientific and Technological Achievement of the Colleges in Guangdong Province, China
文摘The flow behavior of feedstock for the tungsten alloy powder in the mold cavity was approximately described using Hele-Shaw flow model. The math model consisting of momentum equation, consecutive equation and thermo-conduction equation for describing the injection process was established. The equations are solved by the finite element/finite difference hybrid method that means dispersing the feedstock model with finite element method, resolving the model along the depth with finite difference method, and tracking the movable boundary with control volume method, then the pressure equation and energy equation can be resolved in turn. The numerical simulation of the injection process and the identification of the process parameters were realized by the Moldflow software. The results indicate that there is low temperature gradient in the cavity while the pressure and shear rate gradient are high at high flow rate. The selection of the flow rate is affected by the structure of the gate. The shear rate and the pressure near the gate can be decreased by properly widening the dimension of the gate. There is a good agreement between the process parameters obtained by the numerical simulation and the actual ones.
