CN1247175A - Dry pressing technology for integrally forming Si-Mo rod - Google Patents
Dry pressing technology for integrally forming Si-Mo rod Download PDFInfo
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A dry pressing technology for integrally forming Si-Mo rod includes preparing MoSi2 as basic material, preparing high-temp electrothermal material composed of high-smelting-point non-oxide (MoSi2) as main crystal phase and ceramic-glass phase (high-temp ceramic additive) in weight ratio of (11-14) : 1, adding alcohol, granulating, press shaping, removing adhesive, high-temp solid-phase sintering, removing hydrogen and gas, initial vitrification, high-temp impaction ageing, blasting sand and spraying aluminium electrode. Its advntages are no stress centralization, no mutation of components, high electrothermal impaction strength, long service life and low plastic deformation at high-temp.
Description
The present invention relates to the high temperature resistance furnace Heating element, particularly a kind of production technique of integrated dry-pressing formed Si-Mo rod.
Molybdenum disilicide is a kind of high temperature resistant, anti-oxidant, low aged special ceramic material.The molybdenum disilicide heating element is a kind of Heating element of high temperature resistance furnace, can make shapes such as bar-shaped, U-shaped, W shape, screwed pipe shape, so-called " Si-Mo rod ".The thicker part in rod two ends is " cold junction ", and the aluminium-plated part in termination is terminals, and part thinner in the middle of the rod is in " hot junction " as heating.Pass through the conical part transition between this cool and heat ends.Si-Mo rod is a kind of cermet material of densification, by MoSi
2Crystal phase and metallic glass phase composite.Under the oxygenous condition of high temperature, its surface can generate the extremely strong semiconductor alloy glassivation that has automatic cleaning action again of one deck antioxidant property.The spendable body of heater top temperature of Si-Mo rod is 1600 ℃～1900 ℃, is the optimal high temperature exothermic material that uses in oxidizing atmosphere.Si-Mo rod can be widely used in metallurgy, steel-making, glass, pottery, crystalline manufacturing and sintering, is used in particular for producing high-performance ceramic, precision metallic pottery, glass fibre, photoconductive fiber and high-grade alloy steel.
Existing Si-Mo rod all is by the pug mill extrusion molding that mixes, between its cool and heat ends by being welded to connect.Weld material component sudden change, crystalline phase stress and internal stress are big, contact resistance is bigger, therefore cause bulk strength to reduce inevitably, and local superheating is unable to undergo electric heating and is impacted, and the weld fragility very easily ruptures.
When this extrusion molding Si-Mo rod is made U-shaped, W shape rod; the hot junction curved part all adds hot-bending forming with localised protection again after straight excellent sintering is finished; therefore can cause local-crystalized body to change inevitably; destroyed the continuity of original barred body crystalline structure; seriously reduce the physical strength of barred body, caused the crooked position more main hidden danger that in use ruptures.The extrusion molding heating bar belongs to the mixed crystal phase structure, and degree of aging is bigger.
The purpose of this invention is to provide a kind of new dry pressing technology for integrally forming Si-Mo rod, form by powder transition compacting between its cool and heat ends, melt between the cool and heat ends and be one integrated mass, even transition.
Technical solution of the present invention is as follows:
A kind of dry pressing technology for integrally forming Si-Mo rod:
The first step prepares MoSi
2Basestocks: adopt highly purified raw metal Mo powder, Si powder, W powder, Ta powder,, make the basic component raw material of Si-Mo rod goods by spreading synthetic thermopositive reaction certainly; Mo powder, Si powder, W powder, Ta powder are added mixed, ball milling in the ball grinder, and by material: ball=4: 9 (weight ratio) adds the wolfram varbide abrading-ball, ball milling 20～24 hours together behind the inflated with nitrogen; Again from spreading building-up reactions, with the powder logical H in the reactor that packs into
2Gas, logical low-voltage and high-current between the carbon dioxide process carbon electrode of reactor and molybdenum electrode, discharge beginning when electric current increases to 10～25A, at this moment in the exit of reactor hydrogen is caught fire and send basket look flame, temperature of reaction is the heat release accelerated reaction greater than 2000 ℃, and reaction continues 3～5 minutes, reaction finishes when flame is rubescent, and logical water quench is 30～45 minutes from reactor outer wall interlayer; Reactant is taken out from still, pulverize under nitrogen protection with the wolfram varbide Dry-crusher, sieved by sieve in the pulverizer, particle reaches 0.5～1mm level; Then in material: ball=4～5: 1 ratio ball milling 24～36 hours.
The second step batching: prepare a kind ofly by the refractory oxide high-temperature electric heat material that to be principal crystalline phase formed mutually with glass-ceramic, filling a prescription is MoSi
2Powder: pyroceramic additive=11～14: 1 (weight ratio) adds right amount alcohol again; In material: the ratio (weight ratio) of ball=1: 3, will prepare burden with vibratory milling 6 hours, again with rotary mill ball milling 24～36 hours; Powder behind the ball milling is spread out in clean enamel tray, put into the vacuum drying machine with 50 ℃～60 ℃ oven dry that heat up gradually, will constantly stir midway, dusting cover is crossed in the oven dry back; Add-on type tackiness agent then, weigh up paraffin by 1%～2% of powder weight, weigh up polyvinyl alcohol or stearic acid by 0.5%～1% of powder weight, be equipped with an amount of solvent and alcohol, mentioned component is heated to water bath dissolves, impurity is incorporated in mixing in the powder that fills in the nitrogen agitation and filtration machine, oven dry again, is crossed dusting cover by the silk screen elimination.
The 3rd step granulation: granulation for the first time, powder that forming adhesive mix grinding baking the sieved particular manufacturing craft group of packing into will be added with, dry-pressing formed with three axial compression machines greater than 80MPa, in dry type is pulverized filter, pound then and grind into fragment, in filling nitrogen grinding rotary pelleting machine, carefully grind granulation by 30～40 mesh sieves; Granulation for the second time repeats granulating working procedure for the first time, successively crosses 40～50 mesh sieves and 60～70 mesh sieves, makes granularity between 40～70 orders.
The 4th step compression moulding: with granularity is that 40～70 purpose powders divide the another name powder; With powder be respectively charged into the corresponding position seals that feeds intake in the set of molds, vacuumize, inflated with nitrogen; Again the ultrasonic transducer group is placed in the working position, is communicated with pressure, the system for detecting temperature of hot pressing unit, and be communicated with microwave-ultrasonic generation instrument unit output, detection system; Open microwave-ultrasonic generation instrument unit, frequency is exported between 900～3000MHz, power output is changed between 5～450kW on request; Open the hot pressing unit, dry-pressing formed by press operation program and operation code parameter; Latex barrel is immersed in the demoulding then, finishes excellent base latex film sealing; Latex rubber bag is lifted in the isostatic pressing machine, presses the processing of isostatic pressing machine working specification and operation code parameter; Tear latex film at last off, be flat in the graphite boat.
The 5th step was got rid of forming adhesive: the base substrate after dry-pressing formed is removed the organic binder bond that helps moulding by pyrolysis, stays the due material component of Heating element, prepares sintering reaction; Logical H
2Gas by 50 ℃ heat-up rate to 650 ℃ per hour～700 ℃, is incubated 2～3 hours in stove.
The 6th step high temperature solid-phase sintering: workpiece is fully reacted under high temperature and protective atmosphere generate MoSi
2Principal crystalline phase and glass-ceramic and are got rid of the specialty metal stupalith that pore becomes a kind of densification mutually as far as possible, make the high temperature Heating element; Open ammonia by working specification and send out the hydrogen nitrogen equipment, make it enter normal operating conditions; The earlier logical nitrogen of high temperature sintering furnace unit, the cleaning burner hearth, and remove air; When ammonia was sent out hydrogen nitrogen equipment hydrogen supply gas, in the igniting of sintering oven hydrogen outlet place, and control hydrogen output pressure was 0.15MPa; Press the energising of high temperature sintering furnace unit operation rules and heat up, sintering temperature is pressed the product sintering curve and is determined; At any time monitor the high-temperature zone furnace temperature with optical pyrometer, and the reading that the temperature digital of frequent and high temperature sintering furnace unit equipment shows is proofreaded; Regularly advance a graphite boat at regular intervals in stove, end to end with last boat, sintering time is pressed the product sintering curve and is determined; Every graphite boat is through each section of whole shaft, and the place regularly takes out by stove exit.
The 7th step dehydrogenation degassing processing: remove institute's excellent intravital hydrogen that remains in and other gas in the sintering process, will burn till product Si-Mo rod and place and be put on the graphite boat in the vacuum oven, open unit to vacuumize, make the interior vacuum tightness of stove remain 10
-2MmHg progressively was warming up to 650 ℃ of insulation fidelity skies 60～80 minutes, kept vacuum, turn-offed heating power supply, turn-offed vacuum unit power supply when making it naturally cool to below 100 ℃, exitted in stove, opened fire door, took out Si-Mo rod.
The 8th step initial glassization: generate one deck SiO on finished silicon molybdenum bar surface
2-MoSi
2Vitreum, cleaning in the Si-Mo rod continuous tunnel furnace is clean, insert oxygen in high temperature section, keep weather gage pressure to be shown as 0.15～0.2MPa, body of heater is heated up, the high-temperature zone top temperature reaches 1580 ℃, the empty burning more than 2 hours is flat on the Si-Mo rod after the dehydrogenation degasification on the silicon molybdenum grid boat, and order pushes in the continuous tunnel furnace, kept 2～4 hours at 1480 ℃～1530 ℃～1580 ℃ warm areas, progressively release combustion flue.
The 9th step high temperature impact is aging: detect the implicit defective of Si-Mo rod, eliminate initial failure, with the Si-Mo rod after the initial glassization, place on the silicon molybdenum grid boat horizontal sliding fast to go into to be warming up to 1650 ℃ and be incubated among above cabinet-type electric furnace burner hearth half an hour, close fire door, open fire door after 15 minutes and take out Si-Mo rod, make it naturally cool to room temperature, with its surface of metallography microscope sem observation, visible damage and crackle can not be arranged; After the Si-Mo rod cold junction sandblasting behind the high temperature impact, twine and use the special carrier clamping with aluminium foil, and vertically be suspended in the burner hearth of no Si-Mo rod, connect rated operational voltage and cut off the power supply after half an hour, open fire door immediately, connect rated operational voltage again every half an hour, power cutoff after continuing half an hour is opened fire door and is taken out Si-Mo rod, cooling back measured resistance value, its considerable change that do not have, can not there be visible damage on the surface.
The tenth step sandblast, aluminium-plated electrode: as electrode outlet line,, repair with the silicon carbide dedicated tool earlier and remove the overlap that is occurred when suppressing, and polish both ends of the surface for guaranteeing good looking appearance at Heating element two cold-end coating aluminium conductive layers; Sandblast hacking cold junction two is drawn line end, to improve aluminium conductive layer sticking power; By aluminium-plated and working specification cold junction two outlet line end faces and side are sprayed.
Integrated dry-pressing formed Si-Mo rod heating element of the present invention is to mix with ceramic additive behind self-propagating reaction less than the metal molybdenum powder of 1 μ m, silica flour, tungsten powder, tantalum powder etc. with granularity, dispersion and fining, through behind the pre-metallization respectively ultrasonic and wait under the static pressure dry-pressing formedly, make through regional sintering and aging, aftertreatment, initial glassization, coating electrode.Integrated dry-pressing formed Si-Mo rod had both been eliminated stress concentration, did not also have the material component sudden change; Can tolerate electric heating and impact, intensity also greatly improves.
Owing to adopted special powder metallurgy and cermetology, crystalline structure is complete, orderly, and therefore, physical strength improves greatly, and prolong work-ing life, and initial strength is big.No phase transformation influence and damaging below maximum operation (service) temperature, the pyroplastic deformability is little, does not have the peeling off of Watch glass body, disintegrating tablet or bursts phenomenon, heats up rapidly, allows the thermal load height.
Below in conjunction with drawings and Examples the present invention is described in detail.
Fig. 1 is existing extrusion molding Si-Mo rod manufacturing process flow diagram.
Fig. 2 is an integrated dry-pressing formed Si-Mo rod manufacturing process flow diagram of the present invention.
Dry pressing technology for integrally forming Si-Mo rod is as follows:
The first step prepares MoSi
2Basestocks: adopt highly purified raw metal Mo powder, Si powder, W powder, Ta powder,, make the basic component raw material of Si-Mo rod goods by spreading synthetic thermopositive reaction certainly.Its technological process is as follows:
1. ball milling.Ratio in operation code is determined adds mixed, ball milling in the ball grinder with Mo powder, Si powder, W powder, Ta powder, and by material: ball=4: 9 (weight ratio) adds the wolfram varbide abrading-ball, ball milling 20～24 hours together behind the inflated with nitrogen.
2. spread building-up reactions certainly.With the powder logical H in the reactor that packs into
2Gas, logical low-voltage and high-current between the carbon dioxide process carbon electrode of reactor and molybdenum electrode, at this moment the discharge beginning can make hydrogen catch fire in the exit of reactor and send basket look flame when electric current increases to 10～25A, and temperature of reaction is the heat release accelerated reaction greater than 2000 ℃.Reaction continues 3～5 minutes, and reaction finishes when flame is rubescent, and logical water quench is 30～45 minutes from reactor outer wall interlayer.
3. pulverize.
Reactant is taken out from still, pulverize under nitrogen protection with the wolfram varbide Dry-crusher, sieved by sieve in the pulverizer, particle reaches 0.5～1mm level.
4. ball milling.
In expecting: ball=4～5: 1 ratio ball milling 24～36 hours.
The second step batching: prepare a kind of by the refractory oxide high-temperature electric heat material that to be principal crystalline phase formed mutually with glass-ceramic.Various powders, paraffin, polyvinyl alcohol and alcohol are arranged in the prescription.Its technological process is as follows:
1. by prescription and operation code requirement batching, MoSi
2Powder: pyroceramic additive=11～14: 1 (weight ratio) adds right amount alcohol again.
2. in material: the ratio (weight ratio) of ball=1: 3, will prepare burden with vibratory milling 6 hours, again with rotary mill ball milling 24～36 hours.
3. the powder behind the ball milling is spread out in clean enamel tray, put into the vacuum drying machine with 50 ℃～60 ℃ oven dry that heat up gradually, will constantly stir midway, dusting cover is crossed in the oven dry back.
4. add-on type tackiness agent, weigh up paraffin by 1%～2% of powder weight, weigh up polyvinyl alcohol or stearic acid by 0.5%～1% of powder weight, be equipped with an amount of solvent and alcohol, mentioned component is heated to water bath dissolves, impurity is incorporated in mixing in the powder that fills in the nitrogen agitation and filtration machine, oven dry again, is crossed dusting cover by the silk screen elimination.
The 3rd step granulation: be the base substrate density height that heating is shaped, borrow mechanical force to make grain group cracked, and make particle redistribute maximum closely packing arrangement, adhesive distribution evenly and as far as possible to discharge adsorbed gas, need carry out granulation densification repeatedly.Its technological process is as follows:
1. granulation for the first time.With being added with powder that the forming adhesive mix grinding baking sieve particular manufacturing craft group of packing into, dry-pressing formed with three axial compression machines greater than 80MPa, in dry type pulverizing filter, pound then and grind into fragment, in filling nitrogen grinding rotary pelleting machine, carefully grind granulation and pass through 30～40 mesh sieves.
2. granulation for the second time.Repeat granulating working procedure for the first time, successively cross 40～50 mesh sieves and 60～70 mesh sieves, make granularity between 40～70 orders.
The 4th step compression moulding: to obtain the base substrate of desired shape and size.The material that utilizes is powder and the oleic acid that last process transmits.Its technological process is as follows:
1. be that 40～70 purpose powders divide the another name powder with granularity.
2. powder is respectively charged into the corresponding position seals that feeds intake in the set of molds, vacuumizes, inflated with nitrogen.
3. the ultrasonic transducer group is placed in the working position, is communicated with pressure, the system for detecting temperature of hot pressing unit, and be communicated with microwave-ultrasonic generation instrument unit output, detection system.
4. open microwave-ultrasonic generation instrument unit, frequency is exported between 900～3000MHz, power output is changed between 5-450kW on request.
5. open the hot pressing unit, dry-pressing formed by press operation program and operation code parameter.
6. latex barrel is immersed in the demoulding, finishes excellent base latex film sealing.
7. latex rubber bag is lifted in the isostatic pressing machine, presses the processing of isostatic pressing machine working specification and operation code parameter.
8. tear latex film off, be flat in the graphite boat.
The 5th step was got rid of forming adhesive: the base substrate after dry-pressing formed is removed the organic binder bond that helps moulding by pyrolysis, stays the due material component of Heating element, prepares sintering reaction.Its technological process is as follows:
1. logical H
2Gas is in stove.
2. by 50 ℃ heat-up rate to 650 ℃ per hour～700 ℃, be incubated 2～3 hours.
The 6th step high temperature solid-phase sintering: workpiece is fully reacted under high temperature and protective atmosphere generate MoSi
2Principal crystalline phase and glass-ceramic and are got rid of the specialty metal stupalith that pore becomes a kind of densification mutually as far as possible, make the high temperature Heating element, are MoSi
2The rod base substrate.Its technological process is as follows:
1. open ammonia by working specification and send out the hydrogen nitrogen equipment, make it enter normal operating conditions.
2. the earlier logical nitrogen of high temperature sintering furnace unit cleans burner hearth, and removes air etc.
3. when ammonia was sent out hydrogen nitrogen equipment hydrogen supply gas, in the igniting of sintering oven hydrogen outlet place, and control hydrogen output pressure was 0.15MPa.
4. press the energising of high temperature sintering furnace unit operation rules and heat up, sintering temperature is pressed the product sintering curve and is determined.
5. monitor the high-temperature zone furnace temperature at any time with optical pyrometer, and the reading that the temperature digital of frequent and high temperature sintering furnace unit equipment shows is proofreaded.
6. in stove, regularly advance a graphite boat at regular intervals, end to end with last boat.Sintering time is pressed the product sintering curve and is determined.
7. every graphite boat is through each section of whole shaft, and the place regularly takes out by stove exit.
Wherein, the high temperature sintering furnace unit preferably adopts high-frequency induction tubular type sintering oven-regional microwave tunnel sintering oven unit.
The 7th step dehydrogenation degassing processing: remove institute's excellent intravital hydrogen that remains in and other gas in the sintering process.Its technological process is as follows:
To burn till the product Si-Mo rod and place and be put on the graphite boat in the vacuum oven, and open unit and vacuumize, make that vacuum tightness remains 10 in the stove
-2MmHg progressively was warming up to 650 ℃ of insulation fidelity skies 60～80 minutes, kept vacuum, turn-offed heating power supply, turn-offed vacuum unit power supply when making it naturally cool to below 100 ℃, exitted in stove, opened fire door, took out Si-Mo rod.
The 8th step initial glassization: generate one deck SiO on finished silicon molybdenum bar surface
2-MoSi
2Vitreum.Its technological process is as follows:
With cleaning in the Si-Mo rod continuous tunnel furnace totally, insert oxygen in high temperature section, keep weather gage pressure to be shown as 0.15～0.2MPa, body of heater is heated up, the high-temperature zone top temperature reaches 1580 ℃, and empty burning is more than 2 hours.Si-Mo rod after the dehydrogenation degasification is flat on the silicon molybdenum grid boat, and order pushes in the continuous tunnel furnace, keeps 2～4 hours at 1480 ℃～1530 ℃～1580 ℃ warm areas, progressively releases combustion flue.
The 9th step high temperature impact is aging: detect the implicit defective of Si-Mo rod, eliminate initial failure.Its technological process is as follows:
1. with the Si-Mo rod after the initial glassization, place on the silicon molybdenum grid boat horizontal sliding fast to go into to be warming up to 1650 ℃ and be incubated among above cabinet-type electric furnace burner hearth half an hour, close fire door, open fire door after 15 minutes and take out Si-Mo rod, make it naturally cool to room temperature, with its surface of metallography microscope sem observation, visible damage and crackle can not be arranged.
2. with after the Si-Mo rod cold junction sandblasting behind the high temperature impact, twine and use the special carrier clamping with aluminium foil, and vertically be suspended in the burner hearth of no Si-Mo rod, connect rated operational voltage and cut off the power supply after half an hour, open fire door immediately, connect rated operational voltage again every half an hour, power cutoff after continuing half an hour is opened fire door and is taken out Si-Mo rod, cooling back measured resistance value, its considerable change that do not have, can not there be visible damage on the surface.
The tenth step sandblast, aluminium-plated electrode: at Heating element two cold-end coating aluminium conductive layers as electrode outlet line.Its technological process is as follows:
1. for guaranteeing good looking appearance, repair with the silicon carbide dedicated tool earlier and remove the overlap that is occurred when suppressing, and polish both ends of the surface.
2. sandblast hacking cold junction two is drawn line end, to improve aluminium conductive layer sticking power.
3. by aluminium-plated and working specification cold junction two outlet line end faces and side are sprayed.
Carry out aging and detection then, print encapsulation at last and dispatch from the factory.
The present invention has adopted multinomial modern powder metallurgy and sintering metal technology and technology in the process of making molybdenum disilicide high temperature heating element.In the powder process operation, adopted and spread building-up reactions certainly, in granulating working procedure, adopted strong pressure typing secondary granulation greater than 80MPa, in suppression process, adopt microwave-ultrasonic thermocompression and isostatic pressing, in sintering circuit, adopted high-frequency induction formula sintering and regional microwave tunnel sintering.
On selecting materials, select raw material powder such as metal molybdenum powder less than 1 μ m, silica flour, tungsten powder, tantalum powder for use, and in powder handling, accomplish super-refinement, in granulating working procedure, reach molecular process as far as possible, in additive, select MgO, SiO for use
2, Al
2O
3, B
2O
3, Mo and in self-propagating reaction, add Ta, W, improved sintering character and material property.
Following table is the main electromechanical properties (comparing with the world-renowned brand of extrusion molding) of the integrated dry-pressing formed Si-Mo rod of U-shaped of the present invention:
Annotate: " correlative value " picks up from KANTHAL CORP.Sweden. specification sheets in the table.
This shows the characteristics of integrated dry-pressing formed Si-Mo rod of the present invention:
1. physical strength improves greatly.
Between the cool and heat ends of existing extrusion molding Si-Mo rod all by being welded to connect, because weld material component sudden change, crystalline phase stress and internal stress are bigger, contact resistance is bigger, therefore cause bulk strength to reduce inevitably, local superheating is unable to undergo electric heating and is impacted, and the weld fragility very easily ruptures.And be to form by powder transition compacting between the cool and heat ends of integrated dry-pressing formed Si-Mo rod of the present invention, melt between the cool and heat ends and be one integrated mass, even transition.Both eliminate stress concentration, also do not had the material component sudden change; Can tolerate electric heating and impact, intensity also greatly improves.
When the extrusion molding Si-Mo rod is made U-shaped, W shape rod; the hot junction curved part all is after straight excellent sintering is finished; add hot-bending forming with localised protection again; therefore can cause local-crystalized body to change inevitably; destroyed the continuity of original barred body crystalline structure; seriously reduce the physical strength of barred body, caused the crooked position more main hidden danger that in use ruptures.And the curved part of integrated dry-pressing formed Si-Mo rod forms when blank is suppressed, and generates the successive crystalline structure through sintering, has eliminated the easily broken hidden danger of crooked position.
2. initial strength is big.
Existing extrusion molding Si-Mo rod, makes barred body be mingled with a large amount of big scales and seals air mass again because squeeze pressure can not be very high because principal crystalline phase and glassy phase are assembled distribution in flakes, and internal stress is bigger, makes initial tensile strength (＜100Nmm
2), initial bending strength (＜400Nmm
2), initial impact strength (＜0.7Nmcm
2) all can not improve, barred body is not only firmly but also crisp, and is very high in transportation and the spoilage when electric furnace is installed, so need SC, brings very big trouble to installing and using.Distribute and form continuous inclusion between the principal crystalline phase of integrated dry-pressing formed Si-Mo rod and glassy phase, internal stress is very little, adds the pre-metallization technological measure again, and barred body sealing gas phase content is few and yardstick is minimum, makes barred body initial tensile strength (＞190Nmm
2), initial bending strength (＞540Nmm
2), initial impact strength (＞3Ncm
2) all be greatly improved, barred body is the metal sense, has greatly reduced the initial spoilage of transportation, installation and use, has obviously reduced use cost.
3. long service life.
The high-temperature machinery intensity that depends on heating element the work-ing life of Si-Mo rod.Therefore, the Si-Mo rod that physical strength is low in use can not have the very long life-span.In the use of frequent switch fire door and power on/off, thermal stresses can cause the destruction of breaking of the cold and hot end of extrusion molding Si-Mo rod weld and U-shaped rod heating element crooked position.And the physical strength of integrated dry-pressing formed Si-Mo rod makes to obtain widely its work-ing life prolonging far above the Si-Mo rod of extrusion molding.In addition, integrated dry-pressing formed Si-Mo rod is fine and closely woven because of its crystal grain, and it is outer mutually that glassy phase evenly is wrapped in crystal, and the temperature factor difference is minimum, in the current load that allows, can allow blow-on continually, close stove, intensification, cooling, and be damaged never again or rupture.
4. no phase transformation influence and damage below maximum operation (service) temperature.
Existing extrusion molding Si-Mo rod is when being lower than 800 ℃, because of SiO
2Crystal conversion can cause the thermal expansion of barred body outer protective film to destroy, and has a strong impact on the work-ing life of Si-Mo rod, and in the existence of 1350 ℃～1470 ℃ molybdenum silicide principal crystalline phase transformation temperature, makes existing Si-Mo rod be subjected to great restriction in the use of transition temperature area.And integrated dry-pressing formed Si-Mo rod adopts pre-metallization technology in the mill, overcome the phase transformation influence of low temperature, middle temperature, and barred body coefficient of linear expansion and volume coefficient are minimum, but all can steady in a long-term, use freely between the arbitrary temp section below the highest use temperature.
5. the pyroplastic deformability is little.
Existing extrusion molding Si-Mo rod is because glassy phase is abundant in heaps, producing high-temperature softening deformation more than 1300 ℃, make the Si-Mo rod stove in use have to dwindle the workspace operating range, with elongation and the distortion of dealing with Si-Mo rod, thus reduced electric furnace production efficiency, reduced plant factor and energy utilization rate.Distribute and form continuous inclusion between the principal crystalline phase of integrated dry-pressing formed Si-Mo rod and glassy phase, the intergranular layer is very thin even inclusion glassy phase crystal boundary, and the distortion when high temperature is very little, also can not be out of shape, soften or elongation so use under 1800 ℃ of conditions; Even level lays, and uses under 1700 ℃ of high temperature for a long time, also can flexural deformation.
6. there are not the peeling off of Watch glass body, disintegrating tablet or burst phenomenon.
Existing Si-Mo rod is owing to form the very thick vitreum of one deck outside barred body, in the temperature-fall period that repeats to heat up, because the barred body internal-external temperature difference causes vitreum to come off in a large number, can pollute heated material thus.And integrated dry-pressing Si-Mo rod forms continuous thin film shape vitreum outside molybdenum silicide crystal grain, there is not the segregation of excess glass body in the barred body surface, the barred body internal-external temperature difference is minimum, again because the fine and closely woven principal crystalline phase of crystallization becomes inclusion texture mutually with the film like crystal boundary, so the polar expansion of body material and surfacing, volume coefficient are very approaching, thereby eliminated coming off and bursting apart of barred body surface mass effectively.
7. heat up rapidly, allow the thermal load height.
Integrated dry-pressing formed Si-Mo rod has overcome low, middle temperature effects of phase transition because the barred body internal-external temperature difference is minimum, does not have cold and hot end welding and post-treatment bending defect again, and has very high physical strength, thereby possessed the ability to bear of higher surface thermal load.So can resemble the extrusion molding Si-Mo rod needs when heating and cooling meticulously, but can in the short period of time temperature be elevated to calibration value.
Claims (2)
1. a dry pressing technology for integrally forming Si-Mo rod is characterized in that,
The first step prepares MoSi
2Basestocks: adopt highly purified raw metal Mo powder, Si powder, W powder, Ta powder,, make the basic component raw material of Si-Mo rod goods by spreading synthetic thermopositive reaction certainly; Mo powder, Si powder, W powder, Ta powder are added mixed, ball milling in the ball grinder, and by material: ball=4: 9 (weight ratio) adds the wolfram varbide abrading-ball, ball milling 20～24 hours together behind the inflated with nitrogen; Again from spreading building-up reactions, with the powder logical H in the reactor that packs into
2Gas, logical low-voltage and high-current between the carbon dioxide process carbon electrode of reactor and molybdenum electrode, discharge beginning when electric current increases to 10～25A, at this moment in the exit of reactor hydrogen is caught fire and send basket look flame, temperature of reaction is the heat release accelerated reaction greater than 2000 ℃, and reaction continues 3～5 minutes, reaction finishes when flame is rubescent, and logical water quench is 30～45 minutes from reactor outer wall interlayer; Reactant is taken out from still, pulverize under nitrogen protection with the wolfram varbide Dry-crusher, sieved by sieve in the pulverizer, particle reaches 0.5～1mm level; Then in material: ball=4～5: 1 ratio ball milling 24～36 hours;
The second step batching: prepare a kind ofly by the refractory oxide high-temperature electric heat material that to be principal crystalline phase formed mutually with glass-ceramic, filling a prescription is MoSi
2Powder: pyroceramic additive=11～14: 1 (weight ratio) adds right amount alcohol again; In material: the ratio (weight ratio) of ball=1: 3, will prepare burden with vibratory milling 6 hours, again with rotary mill ball milling 24～36 hours; Powder behind the ball milling is spread out in clean enamel tray, put into the vacuum drying machine with 50 ℃～60 ℃ oven dry that heat up gradually, will constantly stir midway, dusting cover is crossed in the oven dry back; Add-on type tackiness agent then, weigh up paraffin by 1%～2% of powder weight, weigh up polyvinyl alcohol or stearic acid by 0.5%～1% of powder weight, be equipped with an amount of solvent and alcohol, mentioned component is heated to water bath dissolves, impurity is incorporated in mixing in the powder that fills in the nitrogen agitation and filtration machine, oven dry again, is crossed dusting cover by the silk screen elimination;
The 3rd step granulation: granulation for the first time, powder that forming adhesive mix grinding baking the sieved particular manufacturing craft group of packing into will be added with, dry-pressing formed with three axial compression machines greater than 80MPa, in dry type is pulverized filter, pound then and grind into fragment, in filling nitrogen grinding rotary pelleting machine, carefully grind granulation by 30～40 mesh sieves; Granulation for the second time repeats granulating working procedure for the first time, successively crosses 40～50 mesh sieves and 60～70 mesh sieves, makes granularity between 40～70 orders;
The 4th step compression moulding: with granularity is that 40～70 purpose powders divide the another name powder; With powder be respectively charged into the corresponding position seals that feeds intake in the set of molds, vacuumize, inflated with nitrogen; Again the ultrasonic transducer group is placed in the working position, is communicated with pressure, the system for detecting temperature of hot pressing unit, and be communicated with microwave-ultrasonic generation instrument unit output, detection system; Open microwave-ultrasonic generation instrument unit, frequency is exported between 900～3000MHz, power output is changed between 5～450kW on request; Open the hot pressing unit, dry-pressing formed by press operation program and operation code parameter; Latex barrel is immersed in the demoulding then, finishes excellent base latex film sealing; Latex rubber bag is lifted in the isostatic pressing machine, presses the processing of isostatic pressing machine working specification and operation code parameter; Tear latex film at last off, be flat in the graphite boat;
The 5th step was got rid of forming adhesive: the base substrate after dry-pressing formed is removed the organic binder bond that helps moulding by pyrolysis, stays the due material component of Heating element, prepares sintering reaction; Logical H
2Gas by 50 ℃ heat-up rate to 650 ℃ per hour～700 ℃, is incubated 2～3 hours in stove;
The 6th step high temperature solid-phase sintering: workpiece is fully reacted under high temperature and protective atmosphere generate MoSi
2Principal crystalline phase and glass-ceramic and are got rid of the specialty metal stupalith that pore becomes a kind of densification mutually as far as possible, make the high temperature Heating element; Open ammonia by working specification and send out the hydrogen nitrogen equipment, make it enter normal operating conditions; The earlier logical nitrogen of high temperature sintering furnace unit, the cleaning burner hearth, and remove air; When ammonia was sent out hydrogen nitrogen equipment hydrogen supply gas, in the igniting of sintering oven hydrogen outlet place, and control hydrogen output pressure was 0.15MPa; Press the energising of high temperature sintering furnace unit operation rules and heat up, sintering temperature is pressed the product sintering curve and is determined; At any time monitor the high-temperature zone furnace temperature with optical pyrometer, and the reading that the temperature digital of frequent and high temperature sintering furnace unit equipment shows is proofreaded; Regularly advance a graphite boat at regular intervals in stove, end to end with last boat, sintering time is pressed the product sintering curve and is determined; Every graphite boat is through each section of whole shaft, and the place regularly takes out by stove exit;
The 7th step dehydrogenation degassing processing: remove institute's excellent intravital hydrogen that remains in and other gas in the sintering process, will burn till product Si-Mo rod and place and be put on the graphite boat in the vacuum oven, open unit to vacuumize, make the interior vacuum tightness of stove remain 10
-2MmHg progressively was warming up to 650 ℃ of insulation fidelity skies 60～80 minutes, kept vacuum, turn-offed heating power supply, turn-offed vacuum unit power supply when making it naturally cool to below 100 ℃, exitted in stove, opened fire door, took out Si-Mo rod;
The 8th step initial glassization: generate one deck SiO on finished silicon molybdenum bar surface
2-MoSi
2Vitreum, cleaning in the Si-Mo rod continuous tunnel furnace is clean, insert oxygen in high temperature section, keep weather gage pressure to be shown as 0.15～0.2MPa, body of heater is heated up, the high-temperature zone top temperature reaches 1580 ℃, the empty burning more than 2 hours is flat on the Si-Mo rod after the dehydrogenation degasification on the silicon molybdenum grid boat, and order pushes in the continuous tunnel furnace, kept 2～4 hours at 1480 ℃～1530 ℃～1580 ℃ warm areas, progressively release combustion flue;
The 9th step high temperature impact is aging: detect the implicit defective of Si-Mo rod, eliminate initial failure, with the Si-Mo rod after the initial glassization, place on the silicon molybdenum grid boat horizontal sliding fast to go into to be warming up to 1650 ℃ and be incubated among above cabinet-type electric furnace burner hearth half an hour, close fire door, open fire door after 15 minutes and take out Si-Mo rod, make it naturally cool to room temperature, with its surface of metallography microscope sem observation, visible damage and crackle can not be arranged; After the Si-Mo rod cold junction sandblasting behind the high temperature impact, twine and use the special carrier clamping with aluminium foil, and vertically be suspended in the burner hearth of no Si-Mo rod, connect rated operational voltage and cut off the power supply after half an hour, open fire door immediately, connect rated operational voltage again every half an hour, power cutoff after continuing half an hour is opened fire door and is taken out Si-Mo rod, cooling back measured resistance value, its considerable change that do not have, can not there be visible damage on the surface;
The tenth step sandblast, aluminium-plated electrode: as electrode outlet line,, repair with the silicon carbide dedicated tool earlier and remove the overlap that is occurred when suppressing, and polish both ends of the surface for guaranteeing good looking appearance at Heating element two cold-end coating aluminium conductive layers; Sandblast hacking cold junction two is drawn line end, to improve aluminium conductive layer sticking power; By aluminium-plated and working specification cold junction two outlet line end faces and side are sprayed.
2. dry pressing technology for integrally forming Si-Mo rod according to claim 1 is characterized in that, described the 6th step during high temperature solid-phase sintering used high temperature sintering furnace unit preferably adopt high-frequency induction tubular type sintering oven-regional microwave tunnel sintering oven unit.
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| CN 98111073 CN1247175A (en) | 1998-09-10 | 1998-09-10 | Dry pressing technology for integrally forming Si-Mo rod |
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| CN 98111073 CN1247175A (en) | 1998-09-10 | 1998-09-10 | Dry pressing technology for integrally forming Si-Mo rod |
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1323820C (en) * | 2004-06-18 | 2007-07-04 | 武汉理工大学 | Functional ceramic low voltage discharge compression forming method |
| CN101531524B (en) * | 2009-04-23 | 2012-12-05 | 宜兴市荣利钨钼制品有限公司 | Method for manufacturing ultrahigh-temperature silicon-molybdenum bars |
| CN101565307B (en) * | 2009-01-21 | 2014-10-29 | 徐艳姬 | Microwave high-temperature heating heat-generating material containing MoSi2 and preparation method thereof |
| CN105803294A (en) * | 2015-06-04 | 2016-07-27 | 卞直先 | Electric heating piece generating biological waves after being electrified and preparing method of electric heating piece |
-
1998
- 1998-09-10 CN CN 98111073 patent/CN1247175A/en active Pending
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1323820C (en) * | 2004-06-18 | 2007-07-04 | 武汉理工大学 | Functional ceramic low voltage discharge compression forming method |
| CN101565307B (en) * | 2009-01-21 | 2014-10-29 | 徐艳姬 | Microwave high-temperature heating heat-generating material containing MoSi2 and preparation method thereof |
| CN101531524B (en) * | 2009-04-23 | 2012-12-05 | 宜兴市荣利钨钼制品有限公司 | Method for manufacturing ultrahigh-temperature silicon-molybdenum bars |
| CN105803294A (en) * | 2015-06-04 | 2016-07-27 | 卞直先 | Electric heating piece generating biological waves after being electrified and preparing method of electric heating piece |
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