107 results about "Chromite" patented technology

The present invention provides a method for hydrogen-based reduction roasting pretreatment of chromite pellets, belonging to the field of metallurgical technology. The method comprises the following steps: mixing chromite powder, a binder and water to form pellets, obtaining green chromite pellets; mixing H2 and CO to obtain a reducing gas; and carrying out reduction roasting on the green chromite pellets in the reducing gas. The reduction roasting of the present invention is carried out in an H2-CO atmosphere, completely without involving the use of primary energy solid carbon, and enables the chromite pellets to obtain sufficient strength and metal pre-reduction degree before entering the ore thermal furnace, which can greatly reduce the comprehensive energy consumption and emissions in the production of ferrochrome alloy.

The invention discloses a method for melting and smelting ferrochrome in an all-oxygen hydrogen-rich low-carbon furnace, which comprises the following steps: (1) proportioning and uniformly mixing chromite pellets, coke and lime according to the mass ratio of 1: (0.15-0.2): (0.08-0.15), and filling the mixture into the all-oxygen hydrogen-rich low-carbon furnace; (2) high-temperature hydrogen-rich gas at the temperature of 900-1100 DEG C is introduced into the middle of the furnace body, and selective reduction of ferrochrome oxide is achieved; blowing industrial pure oxygen at the lower part of the furnace body, combusting with coke to generate CO, and driving a secondary reduction reaction; (3) maintaining a high-temperature environment in the furnace through oxygen-fuel combustion to completely melt the materials into molten iron, and carrying out central stirring on the molten iron to form a vortex with the height-diameter ratio of 0.5-1.5; and (4) discharging the molten iron after the reaction is completed. According to the method, the reduction rate of chromium in the chromite exceeds 92%, the carbon emission is reduced by 40% or above compared with a traditional blast furnace and submerged arc furnace process, meanwhile, the method has the advantages of being high in smelting efficiency, low in energy consumption, stable in product quality and the like, and a low-carbon and efficient innovative path is provided for ferrochrome smelting.

The present invention relates to ship machinery technology and discloses a casting method for a servo valve body, comprising the following steps: step S100: formulating casting equipment for a casting process through three-dimensional mapping design, casting simulation, optimization design, and simulation verification in sequence, placing patches, risers, and chills on both sides of a valve core of a mold and on an upper surface of the mold, respectively, wherein the patches, risers, and chills synergistically form a temperature gradient to control and optimize the solidification process of the casting; step S200: placing a series core frame for connecting a resin chromite sand layer and an ester-hardened water glass sand layer in series in the mold, then filling the working surfaces of the mold and the core with resin chromite sand, and filling the non-working surfaces with ester-hardened water glass sand; and step S300: smelting molten steel, wherein the smelting controlled components (percentage) are: C: 0.34-0.35, Si: 0.45-0.46, Mn: 0.70-0.71, Cr: 0.93-0.95, Mo: 0.20-0.30, and S and P ≤ 0.025. The present invention can solve the technical problems of poor performance and poor quality of valve bodies in the prior art.

The invention relates to a method for cooperatively treating chromium-containing sludge by using a waste dust collecting bag and blast furnace dust. The method comprises the following steps: roasting the waste dust collecting bag to obtain roasted ash of the waste dust collecting bag; mixing the roasting ash and blast furnace fly ash; adding the mixed material 1 into the chromium-containing waste liquid, and carrying out plate-frame pressure filtration to obtain a mixed material 2; the method comprises the following steps: cutting iron ore into blocks, drying, roasting after drying, quickly water-cooling a roasted product, grinding after water-cooling, and magnetically separating a ground product to obtain spinel iron ore concentrate containing ferrochrome and low-chromium tailings. According to the method, the waste dedusting cloth bag and the blast furnace dedusting ash are used as curing agents, curing of heavy metal chromium in the chromium-containing sludge is achieved, the leaching rate of hexavalent chromium and total chromium in the obtained product is far lower than the standard limit value, harmless treatment of the chromium-containing sludge is achieved, the purpose of treating waste with waste is achieved, the obtained ferrochrome spinel can be recycled through magnetic separation, and the method is environmentally friendly. The produced low-chromium tailings can be directly buried or used as building materials.

The invention belongs to the field of comprehensive utilization of chromite, and particularly relates to a method for producing high-carbon ferrochrome through chromite pellet prereduction-electric furnace smelting. According to the method, a reduction method that a reducing agent and chromite pellets are fed into a kiln separately is adopted, chromite oxidized pellets are prepared firstly and then reduced through a rotary kiln solid carbon reducing agent, and the obtained pre-reduced pellets are subjected to electric furnace smelting with a calcium flux and a magnesium flux as slagging fluxes to prepare the high-carbon ferro-chrome. The problem that according to an existing method, the metallization rate of the pre-reduced pellets and the adverse effect on electric furnace smelting caused by unstable carbon residues are solved, the production stability of the electric furnace can be improved, and meanwhile the electric furnace smelting temperature can be increased. The method is simple, controllable, low in energy consumption, high in efficiency, high in stability, low in production cost and convenient for industrial application.

The invention relates to a method for curing harmful components in hazardous wastes, which comprises the following steps: uniformly mixing high-silicon iron tailings and blast furnace fly ash, adding the mixed material into chromium-containing waste liquid, stirring, carrying out plate-frame pressure filtration, carrying out pressure filtration again to obtain a mixed material, cutting the mixed material into blocks, drying the cut mixed material, and roasting after treatment to obtain a roasted product; carrying out rapid water cooling on the roasted product, and grinding after water cooling; and performing magnetic separation on the grinding product to obtain iron ore concentrate containing ferrochrome spinel and low-chromium tailings. According to the method, solid waste high-silicon iron tailings and blast furnace fly ash generated by iron and steel enterprises are used as curing agents, curing of heavy metal chromium in the chromium-containing sludge is achieved, the leaching rate of hexavalent chromium and total chromium in the obtained product is far lower than the standard limit value, harmless treatment of the chromium-containing sludge can be achieved, and the method is suitable for industrial production. The obtained ferrochrome spinel can be recovered through magnetic separation, and the generated low-chromium tailings can be directly subjected to landfill treatment or used as building materials.

The application discloses a preparation method of vanadium-doped and high-hydrated mangan-chromian spinel monocrystal under high temperature and high pressure. The cylindrical mangan-chromian spinel sample is prepared by taking solid rose triangular rhombic manganese carbonate crystal, solid chromium (III) acetate hydroxide crystalline powder, solid vanadium (IV) acetylacetonate oxide powder, solid oxalic acid powder, solid bixbyite powder, solid chromium hydroxide powder and liquid dilute nitric acid as starting raw materials; two pieces of water source sheets are made from the bixbyite powder and the chromium hydroxide powder with a weight ratio of 4:1; the two pieces of water source sheets are placed at two ends of the cylindrical mangan-chromian spinel sample and then are placed into a double-capsule structure experimental sample bin with an inner layer sleeve being a graphite tube and an outer layer sleeve being a gold-palladium alloy tube; the high temperature and high pressure reaction is carried out to obtain the mangan-chromian spinel monocrystal; and the preparation technology blank of the vanadium-doped and high-hydrated mangan-chromian spinel large-particle monocrystal under the current high temperature and high pressure conditions is solved.

The application discloses a preparation method of a nickel-doped and high-hydrated cobalt-chromium-iron ore monocrystal under high temperature and high pressure, and the method comprises the following steps: preparing a cylindrical cobalt-chromium-iron ore sample by taking solid basic cobalt carbonate powder, solid chromium (III) acetate hydroxide crystal powder, solid nickel stearate, solid oxalic acid powder, solid chromium hydroxide powder, solid nickel hydroxide powder and liquid dilute nitric acid as starting raw materials; preparing water source sheets by taking chromium hydroxide powder and nickel hydroxide powder in a weight ratio of 4:1; placing two water source sheets at two ends of the cylindrical cobalt-chromium-iron ore sample respectively and then putting them into a double-capsule structure sample bin; and obtaining a cobalt-chromium-iron ore monocrystal after high-temperature and high-pressure reaction, so that the blank of the preparation technology of the nickel-doped and high-hydrated cobalt-chromium-iron ore large-grain monocrystal under the current high-temperature and high-pressure condition is solved, and the experimental sample of the nickel-doped and high-hydrated cobalt-chromium-iron ore large-grain monocrystal is obtained.

This invention relates to the field of casting technology for sand cores and sand shells, and particularly to a method for preparing high-precision casting sand cores and sand shell components based on a coated sand process. The method includes the following steps: rinsing quartz sand and reacting it with a sodium silicate solution to obtain coated quartz sand; adding 3-aminopropyltriethoxysilane and water to the coated quartz sand in a high-speed mixer; sequentially adding modified benzoxazine resin, calcium citrate, magnesium chloride, hyperbranched polyamide, and polycaprolactone-grafted starch to obtain finished coated sand; plasma-treated chromium-12 molybdenum-vanadium mold steel to obtain an amino-modified mold; sand-jetting the finished coated sand into left / right half-shells; shaping and pre-embedding chromite sand cores with chills to obtain left / right half-shell green blanks; milling the surfaces of the left / right half-shell green blanks, coating them with resin, butt-jointing, curing, and deburring to obtain the casting sand core and sand shell. This method solves the problems of poor mechanical strength, poor high-temperature stability, low production efficiency, and poor environmental performance in high-precision casting sand cores and sand shells.

The present invention provides a heat exchanger capable of stably and continuously recovering heat over a long period of time, even when the target gas for heat recovery is an extremely corrosive gas, and an exhaust gas treatment device using such a heat exchanger. [Solution] The heat exchanger of the present invention is characterized by comprising a partition plate (14) made of refractory castable material that divides the inside of the casing (12) so that the low-temperature side fluid (LF) and the high-temperature side fluid (HF) flow in countercurrents, and a plurality of solid heat transfer rods (16) made of at least one ceramic selected from the group consisting of alumina, zirconia, silicon carbide, silicon nitride, molybdenum silicide, and lanthanum chromite, which are arranged to airtightly penetrate the front and back surfaces of the partition plate (14) and cross the flow paths of the low-temperature side fluid (LF) and the high-temperature side fluid (HF).

This invention provides a method for low-temperature reduction roasting pretreatment of chromite pellets under a CH4-containing reducing atmosphere, belonging to the field of metallurgical technology. The method includes the following steps: mixing chromite powder, binder, and water to form pellets, obtaining green chromite pellets; mixing CH4 and a reducing gas to obtain a CH4-containing reducing atmosphere, wherein the reducing gas includes H2 and / or CO; and reducing roasting the green chromite pellets in the CH4-containing reducing atmosphere. This invention introduces CH4 gas into the reducing atmosphere, without using solid carbon. CH4 can decompose and release carbon at relatively low temperatures, which is beneficial for the smooth operation of common industrial equipment. The released carbon has high activity and can effectively dissociate the spinel phase in chromite, and rapidly achieve effective reduction of Fe and Cr oxides therein, obtaining chromite pellets with a certain degree of pre-reduction of metallic iron and chromium and a certain strength.

The invention discloses an alloy material resistant to chloride molten salt corrosion and a preparation method and application thereof. The alloy material resistant to chloride molten salt corrosion comprises a chromium-containing alloy material matrix and a magnesium chromite-containing protective layer covering the surface of the chromium-containing alloy material matrix. The preparation method comprises the following steps: 1) mixing lithium carbonate-sodium carbonate-potassium carbonate molten salt and a magnesium source to prepare a mixture; and 2) covering the surface of a chromium-containing alloy material matrix with the mixture to carry out oxidation reaction, and then washing and drying. The surface of the alloy material is covered with the protection layer containing magnesium chromite, the preparation process of the protection layer is simple, the stability of the protection layer in a high-temperature chloride molten salt environment is good, and corrosive impurities in chloride molten salt can be effectively prevented from making contact with an alloy matrix; the corrosion of the chloride molten salt on key components such as a storage tank and a heat exchanger in the CSP system under a high-temperature condition is avoided, and the efficient, stable and safe operation of the CSP system is ensured.

The present invention provides a combined beneficiation method for laterite nickel ore. The method comprises the following steps: a first cyclone separation, a spiral chute, a multi-stage shaking table classification, a plurality of weak magnetic separations and a plurality of spiral classifications, so as to separate chromite from the laterite nickel ore, thereby obtaining a first chromium concentrate, a chromium middling, a weak magnetic separation middling and a mixed light ore; and a subsequent combined process of multiple ball millings, a second cyclone, a weak magnetic separation and a strong magnetic separation is used to further enrich and separate chromium from the mixed light ore, the weak magnetic separation middling and the limonite and chromite that have been missed in the strong magnetic separation magnetic material, thereby screening out more second chromium concentrate, facilitating a reduction in the chromium content in a subsequent high-pressure leaching stock solution, thereby achieving comprehensive utilization of the chromium element.

The application discloses a preparation method of titanium-doped and high-hydrated magnesio-chromian spinel monocrystal under high temperature and high pressure, and the method comprises the following steps: preparing a cylindrical magnesio-chromian spinel sample by taking solid basic magnesium carbonate powder, solid basic chromium acetate crystal powder, liquid tetraisopropyl titanate, solid oxalic acid powder, solid brucite powder, solid chromium hydroxide powder and liquid dilute nitric acid as starting raw materials; preparing water source sheets by taking brucite powder and chromium hydroxide powder with a weight ratio of 4:1 as water sources; placing two water source sheets at two ends of the cylindrical magnesio-chromian spinel sample and putting them into a double-capsule structure sample bin together to carry out high temperature and high pressure reaction, so as to obtain titanium-doped and high-hydrated magnesio-chromian spinel monocrystal; and the method solves the blank of the preparation technology of the titanium-doped and high-hydrated magnesio-chromian spinel large-grain monocrystal under the current high temperature and high pressure conditions, and obtains experimental samples of the titanium-doped and high-hydrated magnesio-chromian spinel large-grain monocrystal.

The present invention discloses a gravity separation system and method for low-grade chromite. The separation system comprises a spiral chute for roughing, a spiral chute for first-stage cleaning, a spiral chute for second-stage cleaning, a spiral chute for first-stage scavenging, and a spiral chute for second-stage scavenging. The roughing spiral chute has an aspect ratio A of 0.50 and a lateral inclination angle B of 8.7° or 9.3°. The first-stage cleaning spiral chute and the second-stage cleaning spiral chute have an aspect ratio A of 0.58 or 0.62 and a lateral inclination angle B of 9.5° or 10.5°. The first-stage scavenging spiral chute and the second-stage scavenging spiral chute have an aspect ratio A of 0.43 or 0.47 and a lateral inclination angle B of 8.2° or 8.6°. The use of the above-mentioned sorting system for roughing, concentrating and scavenging can greatly improve the mineral processing capacity and the grade and recovery rate of chromite concentrate. The present invention has the advantages of simple production operation, low consumption, greenness and stable indicators. It can adapt to the large-scale chromite mineral processing production requirements and has excellent production indicators.

The utility model discloses a chromite oxidizing roasting device, which belongs to the technical field of metallurgical chemical equipment and comprises a first-section heating kiln, a second-section deep oxidation kiln, a chute and a support frame, the first-section heating kiln, the second-section deep oxidation kiln, the chute and the support frame are distributed in an up-and-down stepped manner, and the kiln heads of the first-section heating kiln and the second-section deep oxidation kiln are lower than the kiln tails and are inclined. According to the utility model, the sectional deep oxidizing roasting device is used for sectional oxidizing roasting, and the first-section heating kiln is mainly used for preheating raw materials and carrying out preliminary oxidizing roasting in the heating process; the second-section deep oxidation kiln is connected into an oxygen introducing pipeline, high-concentration oxygen gas is introduced into the kiln body, and deep oxidation roasting is carried out; meanwhile, when the oxygen hole is controlled to rotate to the bottom of the material, the controller opens the oxygen control valve of the corresponding access point, the material is exploded by means of the gas pressure of the oxygen, the contact area of the material and the oxygen is further increased along with rotation of the kiln body, and the mass and heat transfer effect is enhanced. The deep oxidation roasting device improves the chromium conversion rate, reduces the production cost and reduces the environmental pollution.

The invention relates to a sample pretreatment method for chromite microelement analysis. The method comprises the following steps: firstly, treating a sample to specific particle size distribution (Dv (50) lt, 5 [mu] m, Dv (90) lt, 20 [mu] m) through physical accurate grinding, and then adopting an improved two-step acid dissolution and digestion process: firstly, destroying main crystal lattices of minerals by using mixed acid, then, carrying out targeted dissolution on a residual insoluble phase by using aqua regia, and finally, carrying out chlorine removal treatment to obtain a solution to be detected. Through the synergistic effect of physical accurate grinding and secondary acid dissolution, almost complete decomposition of chromite is achieved, especially the extraction efficiency of key indissolvable elements such as Sc and Zn is improved by 20% or above, the accuracy and precision of ICP-MS analysis results are remarkably improved, and the problem that microelement measured value systematicness is low due to incomplete dissolution in a traditional method is solved.

The invention provides a recovery method of chromite, and relates to the field of mineral processing. The chromite recycling method comprises the steps that chromite raw ore is subjected to first crushing, and a first crushed product is obtained; performing first screening on the first crushed product to obtain a first oversize product and a first undersize product; the first oversize product is subjected to photoelectric pre-selection, and photoelectric pre-selected concentrate and photoelectric pre-selected tailings are obtained; the first screen underflow is subjected to rolling treatment, and a rolled product is obtained; carrying out second screening on the rolled product to obtain second screen underflow, and carrying out third screening on the second screen underflow to obtain third screen underflow; carrying out desliming treatment on the third screen underflow to obtain fine silt and coarse grain reselection feed ore; coarse grain gravity separation is conducted on the coarse grain gravity separation feed ore, and first chromite concentrate, second chromite concentrate and gravity separation fine grain feed ore are obtained; and the gravity separation fine grain feeding ore is subjected to grading treatment and fine grain gravity separation, and third chromite concentrate and tailings are obtained. According to the method, high-quality chromite concentrate can be obtained, and the high recovery rate is achieved.

The application discloses a method for determining different forms of chromium in soil in a high geological background area and application thereof. The method can sequentially extract the same soil sample and analyze the chromium content in the soil after each step of extraction, so that the distribution of chromium in different forms is obtained, including extracting the adsorbed hexavalent chromium in the soil by using an NH4H2PO4 solution, extracting the iron oxide state chromium therein by using a hot ascorbic acid-ammonium oxalate solution, and extracting the silicate state chromium by using hot concentrated hydrochloric acid, so that the chromium in the chromium iron ore can be fully separated, and accurate results of the chromium form distribution in the high geological background soil are obtained.

The invention belongs to the field of crude sand of quartz sand for casting, and particularly relates to composite quartz sand which is low in cost, low in energy consumption, low in linear thermal expansion rate and high in refractoriness and a preparation method of the composite quartz sand. The preparation method of the composite quartz sand comprises the following steps: 1) uniformly mixing quartz sand, bauxite, zircon powder, olivine powder, chromite powder, calcium carbonate, magnesium oxide, silicon phosphate and dextrin in a bowl-shaped sand mixer; (2) adding one or more adhesives such as phosphate, water glass, hydrated silicon dioxide and dextrin, and uniformly mixing; and 3) roasting the mixed material at the temperature of less than or equal to 400 DEG C to obtain the composite quartz sand.

The invention discloses an investment casting shell-making process of a stainless steel part, which comprises the following steps of: dipping a layer of slurry on the surface of a module, spraying a layer of sand on the surface of the module, performing high-temperature dewaxing after five layers are reached to form a shell, filling a mixture of chromite sand and water glass in an inner hole of the shell, and introducing carbon dioxide gas, so that an inner hole sand mold is quickly hardened; and roasting the treated shell, and carrying out vacuum pouring, cooling molding, cutting and polishing treatment on the shell to obtain a casting. The inner hole of the shell is filled with the mixture of the chromite sand and the water glass, the carbon dioxide is introduced into the inner hole to react with the water glass, and finally generated silicic acid gel enables the sand mold at the inner hole to be rapidly hardened, so that the problem that the plane of the shell is expanded due to expansion generated by wax melting in the dewaxing process is solved; and meanwhile, the chromite sand has the characteristic of rapid heat dissipation and is used as an internal chilling block, so that the problem of shrinkage porosity of the shell caused by slow heat dissipation of the bottom plane of the inner hole in the pouring process is solved.

The invention discloses a casting method for prolonging the service life of a metallurgical slag pot, and relates to the technical field of metallurgical casting. According to the method, the material ratio is optimized, and low-alloy heat-resistant steel containing Cr, Ni, Mo, V and Ti is adopted as a matrix; the casting process is optimized, quartz sand and chromite sand composite sand is adopted, lost foam casting and stepped cooling are adopted, and casting defects are reduced; through quenching and tempering heat treatment and Al2O3-TiO2 ceramic coating surface strengthening, the high-temperature erosion resistance, corrosion resistance and thermal shock resistance of the slag ladle are improved. The prepared slag ladle is complete in structure and stable in performance, the service life is prolonged to 1500 heats or above and is improved by 60% or above compared with the prior art, the technology is mature and controllable, the slag ladle is suitable for industrial batch production, the production cost of metallurgical enterprises can be effectively reduced, and the slag ladle has important industrial application value.

The invention discloses a method for preparing ferrochrome pre-reduced pellets through hydrogen-solid carbon coupling reduction, and belongs to the technical field of ferrochrome alloy metallurgy. The method comprises the steps that chromite, solid carbon, a binder and water are mixed for pelletizing, obtained wet pellets are sequentially subjected to drying, preheating and reduction roasting, and ferrochrome pre-reduced pellets are obtained; the reduction roasting comprises two stages of reduction processes: the first stage of reduction process is as follows: hydrogen is introduced from the outside at the temperature of 900-1100 DEG C, and the hydrogen and solid carbon are used for reduction; and the second-stage reduction process comprises the following steps: stopping introducing hydrogen at the temperature of 1200-1350 DEG C, and reducing by using solid carbon. According to the method, by designing a hydrogen-solid carbon coupling reduction system, the reduction efficiency and the alloying rate of chromite can be improved, meanwhile, the consumption of solid carbon is reduced, the purposes of energy conservation and emission reduction are achieved, and the method has the beneficial effects of being simple in process, low in energy consumption, small in carbon emission and the like.

The invention discloses a method for producing a high-precision corrosion-resistant casting through shell mold casting and application of the method, and belongs to the technical field of casting. The method comprises the steps of shell mold manufacturing, shell boxing, melting casting and casting taking-out, specifically, precoated sand containing chromite sand, modified phenolic resin and the like is prepared, after shell manufacturing, steel shots are filled for compaction, molten iron containing C, Si, Ni, rare earth and the like is cast at the temperature of 1350-1400 DEG C, and after cooling, the casting is taken out and cleaned. According to the method, the corrosion resistance, the precision and the mechanical property of the casting are improved through material component collaboration and process optimization, and the method is suitable for the fields of pump valves, marine equipment and the like.

The invention discloses a beneficiation method for recovering chromium from laterite-nickel ore, and belongs to the technical field of beneficiation of laterite-nickel ore. According to the characteristics of products with different size fractions in the laterite-nickel ore, a targeted separation process path is adopted; for settled sand with a relatively large particle size, a process of firstly performing gravity separation and then performing magnetic separation is adopted, and a common spiral chute and a low-speed spiral chute are combined for use in equipment type selection; and for overflow with fine granularity and low grade, a process of magnetic separation and reselection is adopted, a low-speed spiral chute is used for pre-enrichment and waste throwing in advance, and after the selected grade is improved, a slime shaking table is used for separation. According to the method, the recovery efficiency of the low-grade micro-fine particle chromite in the overflow of the cyclone is remarkably improved, the grade of ore pulp flowing into a slurry shaking table is ensured, the content of chromium finally entering a nickel smelting system is effectively reduced, and the method has the advantages of being high in recovery rate, high in Cr2O3 grade and the like.

The invention belongs to the field of iron and steel smelting, and particularly relates to a method for preparing iron and chromium by reducing chromium-containing raw materials through electromagnetic induction heating. The method comprises the following steps: (1) carrying out first pelletizing on raw materials comprising chromium-containing metallurgical solid waste, first chromite, a first carbon source, metal iron particles and a first additive to obtain primary pellets containing the metal iron particles; (2) the primary pellets are subjected to first reduction, and a slag-iron mixture is obtained; (3) crushing and grinding the slag-iron mixture, and carrying out electromagnetic separation to obtain chromium-rich slag and iron particles; (4) the chromium-rich slag, second chromite, a second carbon source, ferrochrome alloy particles, a second additive and a slag former are subjected to second pelletizing, and secondary pellets containing ferrochrome alloy particles are obtained; (5) secondary reduction is conducted on the secondary pellets, and ferrochromium alloy melt and refining slag are obtained; and (6) casting the ferrochrome alloy melt into an alloy ingot, cooling, crushing, and screening to obtain a ferrochrome alloy product. The method can improve the recovery rate of Cr.

The invention discloses high-self-opening-rate stuffing sand based on gradient sintering and a micro-valve effect. The stuffing sand comprises a compact sealing layer, a weak combination transition layer and a loose maintaining layer which are arranged in sequence. Wherein the compact sealing layer comprises the following raw materials in parts by weight: 50-70 parts of chromite sand, 20-30 parts of zircon sand, 5-8 parts of potassium feldspar powder, 2-4 parts of boron glass powder, 2-3 parts of high-purity graphite and 0.5-1 part of metal silicon powder; the weak bonding transition layer comprises the following raw materials in parts by weight: 50-70 parts of zircon sand, 20-30 parts of low-chromium magnesia, 3-5 parts of potassium feldspar powder, 2-3 parts of boron glass powder, 1-3 parts of inert microbeads, 2-3 parts of high-purity graphite, 0.5-1 part of metal silicon powder and 0.1-0.5 part of organic fibers; the loose maintaining layer comprises the following raw materials in parts by weight: 97-99 parts of high-purity fused magnesite and 1-3 parts of high-purity graphite. During preparation, all layers of granules are prepared according to a formula, and then the granules are sequentially laid at the bottom of a furnace layer by layer. The production efficiency is high, the self-opening rate of the obtained ladle filler sand is stably larger than or equal to 99.4%, and the ladle filler sand is suitable for preparing high-quality steel such as high-oxygen steel and clean steel and also has a good effect on steel ladles with the use time longer than 60 minutes.

This invention relates to a manufacturing method for large ball valve castings for pumped storage power stations, belonging to the field of large-scale high-end cast steel parts manufacturing technology. It solves the problems of shrinkage porosity, cracks, inclusions, and uneven mechanical properties that easily occur inside large valve castings in existing technologies. The method includes: a smelting step: smelting molten steel using an electric furnace, LF furnace, and VD vacuum treatment while controlling the carbon equivalent; a casting step: using a composite mold and chromite sand, baking and argon protection of the mold cavity, and employing a stepped casting process of converting from a double-gate to a single-gate and then point-to-point replenishment; and a heat treatment step: sequentially performing pretreatment and a water-cooling-air-cooling-water-air-cooling-water-air-cooling process followed by high-temperature tempering. This method achieves high-quality, high-density, high-performance, and stable manufacturing of large ball valve castings for pumped storage power stations.

The invention relates to the technical field of iron smelting, in particular to a slag-iron separation optimization method for high-carbon chromite hot slag. The method comprises the steps that the molten iron temperature and the slag temperature are obtained, instantaneous density values of molten iron and slag are estimated respectively, and the density ratio of the molten iron to the slag is obtained; based on the density ratio of the molten iron to the slag, an interface height dynamic positioning model is constructed, and the layered interface height is obtained; a layered shear disturbance intensity calculation formula is introduced to quantify the shear force, and the shear disturbance intensity is obtained; and based on the shear disturbance intensity, the molten iron and slag outlet opening ratio is adjusted in combination with the layered interface height, and separation optimization is conducted based on the molten iron and slag outlet opening ratio. The problem that in the slag separation process, dynamic response control over the layered interface height cannot be achieved mainly depending on operator experience and fixed structure adjustment is solved; and layering failure and frequent mixed flow phenomena are caused by the influence of factors such as interface disturbance and temperature gradient.

The application provides a method for determining the Re-Os isotope of chromite, comprising the following steps: weighing the chromite sample and adding it into a Carius tube; transferring the accurately weighed mixed diluent to the Carius tube under a refrigerated condition by using HCl; after freezing, adding HNO3 and H2O2 into the Carius tube in sequence and continuing to freeze, wherein the volume ratio of HNO3, HCl and H2O2 in the Carius tube is 4:4:1; after the Carius tube is closed, it is placed in an oven for heating for a preset time to dissolve the sample; the Re and Os in the sample solution are separated by using a direct distillation method; and the Re in the residual solution after distillation and the Os in the distillation absorption solution are enriched and purified, and high-precision Re-Os isotope determination is performed. The method has a lower overall process blank, can ensure high-precision analysis of chromite samples with extremely low Re content, and reduces the problems of Os cross contamination and sample loss.