The manufacture method of silicon nitride heat generating body
Technical field
The present invention relates to the technical field of the manufacture method of electric heating element, specifically is a kind of manufacture method of silicon nitride heat generating body.
Background technology
Silicon nitride is a kind of covalent bond pottery, pure Si
3N
4Powder can't sintering, must add a small amount of sintering agent and form liquid phase at high temperature, carries out liquid-phase sintering, just can obtain the silicon nitride material of excellent performance.Additive commonly used comprises: Al
2O
3, MgO, SiO
2Deng metal oxide, Y
2O
3, La
2O
3, CeO
2Deng rare earth oxide, and AlN, Mg
3N
2, TiN, nitride such as ZrN.The high-performance silicon nitride ceramics has excellent electricity, calorifics and mechanical property such as insulation, high-strength, high temperature resistant, resistance to oxidation, heat shock resistance and high-termal conductivity.
Silicon nitride heating sheet is a kind of device in conjunction with high-performance silicon nitride ceramics matrix and powerful high-temperature metal heating wire of long-life.It is little to have volume, characteristics such as the big and heat efficiency height of power, and the while also is proved to be a kind of safe and reliable heating system.Directly after the energising, temperature is done on the surface can reach 1200 degrees centigrade, and working life reached more than 5000 hours.High-temperature metal heating wire material comprises, materials such as tungsten filament, molybdenum filament and various tungsten-molybdenum alloy silks.
At present, there is the phenomenon of carburizing in the silicon nitride in market heating sheet material more, from outside watch surface distributed that phenomenons such as bulk blackspot, black patch are arranged, color and luster is inhomogeneous.Pure Si
3N
4The true qualities of dense sintering material should be canescence, and existing product exists matrix black mostly, and the even or uneven distribution pore in surface more has surface distributed that phenomenons such as bulk blackspot, black patch are arranged.This mainly be in the hot pressed sintering process since biscuit directly contact with graphite, carbon infiltrates along liquid channel, dissolve in the liquid phase, or with silicon nitride react the generation.The insulation property of the infiltration meeting deterioration material of carbon reduce fail safe and reliability.Simultaneously because the hot pressed sintering time is short, rely on mechanical pressure to strengthen fine and close effect, the material that obtains exists that boundary stress is big, the inadequate microstructure of liquid phase crystallization, influences the useful life of basis material.
Summary of the invention
The technical problem to be solved in the present invention provides the manufacture method of the simple silicon nitride heat generating body of a kind of technology, to produce the silicon nitride heat generating body with higher reliability and fail safe.
For solving the problems of the technologies described above, the manufacture method of silicon nitride heat generating body provided by the invention comprises:
Step 1, silicon nitride powder and high-temperature liquid-phase sintering agent inserted in the absolute ethyl alcohol by weight 0.96: 0.04 to 0.80: 0.20 mix, after batch mixing 10-72 hour, make formulation material through mist projection granulating;
Step 2, with described formulation material dry-pressing formed after, by the further compression moulding of the isostatic cool pressing of 180-220MPa, and pressurize 3-10 minute, to make biscuit;
Step 3, after evenly applying one deck boron nitride separator, described biscuit surface dries;
Step 4, carry out hot pressed sintering then, sintering pressure 20-30MPa, sintering temperature 1600-1900 ℃, temperature retention time 0.5-4 hour, to make blank;
Step 5, described blank is put into vacuum atmosphere oven, keep 1300-1600 ℃ constant temperature 10-24 hour, naturally cool to room temperature then.
Further, described boron nitride separator is the thick shape slurry that reconciles into absolute ethyl alcohol after being mixed by boron nitride powder and silicon nitride powder; Wherein, the part by weight of silicon nitride powder and boron nitride powder is: 0.10: 0.90 to 0: 1.00.
Further, in the described step 4, when carrying out hot pressed sintering, scribble the described boron nitride separator of one deck on the hot pressing graphite jig and contact-making surface biscuit of employing.
The preferred Al of described high-temperature liquid-phase sintering agent
2O
3, MgO, SiO
2Deng metal oxide, Y
2O
3, La
2O
3, CeO
2Deng rare earth oxide, AlN, Mg
3N
2, TiN, nitride such as ZrN, addition are 4wt%-20wt%.Wherein, the addition of described metal oxide is 0-20wt%, and the addition of rare earth oxide is 0-20wt%, and the addition of nitride is 0-5wt%.The common metal oxide can reduce sintering temperature, and rare earth oxide and a small amount of nitride can increase the viscosity of high-temperature liquid-phase and help high temperature crystallization.
The technique effect that the present invention has: (1) silicon nitride heat generating body of the present invention adopts high purity silicon nitride (Si
3N
4) powder, a small amount of liquid phase sintering agent and high-temperature metal heating wire form, and through forming of green body, makes compact silicon nitride base heater after hot pressed sintering and the high-temperature heat treatment.This heater has the characteristics of high-strength, high thermal conductance, high reliability.Wherein the biscuit surface has boron nitride powder (BN) coating, and this technology has been eliminated the infiltration of carbon in the production process.High-temperature heat treatment process has been eliminated material stress, has promoted the crystallization of crystal boundary glassy phase, has improved the reliability and the fail safe of device greatly.(2) in the manufacture method of silicon nitride heat generating body of the present invention, as medium, ball milling mixing 10-72 hour had both guaranteed that batch mixing was even, had reduced oxidative phenomena again with absolute ethyl alcohol (99.9% purity).Do not add any macromolecule modifier in the manufacturing process of the present invention.Some polymeric additive can improve the performance of biscuit and improve the shaping finished product rate, yet the biscuit of this technological forming must be got rid of polymeric additive through the sticking technology of row.In general, the sticking carbon that can get rid of to greatest extent and burn in the polymeric additive of row under oxygen atmosphere.And that silicon nitride can only be arranged under vacuum or nitrogen protection atmosphere is sticking, thoroughly eliminates relatively difficulty of carbon, is evenly distributed in the biscuit so always stay the residue of some carbon containings, can reduce insulated with material and reliability.The present invention does not adopt any macromolecule additive, but relies on dry-pressing and the high-intensity biscuit of isostatic cool pressing prepared.(3) among the present invention, the biscuit surface evenly is coated with the BN separator, can stop biscuit to contact with the direct of graphite, has eliminated the possibility of high temperature case-carbonizing element.(4) the present invention is behind hot pressed sintering, and the material stress of silicon nitride heat generating body is bigger, slowly cools to room temperature after at high temperature annealing in process 10-24 hour, can eliminate the stress of material.In addition, in high-temperature process, make the glassy phase crystallization in the material, can further eliminate remaining carbon and reduce material stress.(5) silicon nitride heating matrix of the present invention contains high-purity Si 3N4 powder and a small amount of high-temperature liquid-phase sintering agent.Initial substrate raw material and heating wire are made biscuit, biscuit surface-coated BN material through dry-pressing and isostatic cool pressing.Biscuit hot pressed sintering under HTHP becomes blank.Sintering blank high-temperature heat treatment process is eliminated material stress and glass ceramics mutually, has the characteristics of higher reliability and fail safe.
Description of drawings
For the easier quilt of content of the present invention is clearly understood, below the specific embodiment and in conjunction with the accompanying drawings of basis, the present invention is further detailed explanation, wherein
Fig. 1 is the structural representation of the silicon nitride heat generating body among the embodiment.
Reference numeral: 1--silicon nitride heat generating body, 2--metal heating wire, 3--electrode.
Embodiment
The present invention is described in detail below in conjunction with drawings and Examples:
(embodiment 1)
The silicon nitride heat generating body of present embodiment is made up of silicon nitride heating and the high-temperature metal heating wire be located in the silicon nitride heat generating body.The metal heating wire is a tungsten filament, molybdenum filament or tungsten-molybdenum alloy silk.
The manufacture method of above-mentioned silicon nitride heat generating body comprises:
Step 1, silicon nitride powder and high-temperature liquid-phase sintering agent inserted in the absolute ethyl alcohol by weight 0.96: 0.04 to 0.80: 0.20 mix (specifically can adopt the ball milling mixer to mix), after batch mixing 10-72 hour, make formulation material through mist projection granulating;
Step 2, the metal heating wire is imbedded in the described formulation material dry-pressing formed, the further compression moulding of isostatic cool pressing by 180-220MPa then, and pressurize 3-10 minute is to make biscuit;
Step 3, after evenly applying one deck boron nitride separator, described biscuit surface dries;
Step 4, carry out hot pressed sintering then, sintering pressure 20-30MPa, sintering temperature 1600-1900 ℃, temperature retention time 0.5-4 hour, to make blank;
Step 5, described blank is put into vacuum atmosphere oven, keep 1300-1600 ℃ constant temperature 10-24 hour, naturally cool to room temperature then, at last at metal heating wire two ends welding electrode.
Described boron nitride separator is the thick shape slurry that reconciles into absolute ethyl alcohol after being mixed by boron nitride powder and silicon nitride powder; Wherein, the part by weight of silicon nitride powder and boron nitride powder is: 0.10: 0.90 to 0: 1.00.
In the described step 4, when carrying out hot pressed sintering, scribble the described boron nitride separator of one deck on the hot pressing graphite jig and contact-making surface biscuit of employing.
(embodiment 2)
On the basis of embodiment 1, the manufacture method of the silicon nitride heat generating body of present embodiment comprises:
With the silicon nitride powder of 92wt%, the Al of 3wt%
2O
3, the Y of 3wt%
2O
3, the MgO of 1wt%, the AlN of 1wt% add 99.9% absolute ethyl alcohol and evenly mixed 72 hours, insert in the explosion-proof mist projection granulating tower mist projection granulating then and make formulation material.
Formulation material is poured in the mould, again the metal heating wire is imbedded in the powder dry-pressing formedly, be of a size of 120*20*10.With dry-pressing formed biscuit encapsulation, put into isostatic cool pressing equipment and wait static pressure to handle again, the pressure that waits static pressure is 200MPa, dwell time 3-10 minute.Reconcile into thick shape slurry with high-pure anhydrous ethanol and boron nitride fine powder, adopt knife coating, at biscuit surface-coated layer of even boron nitride separator, oven dry is handled.Also be coated with one deck boron nitride separator at hot pressing graphite jig and biscuit contact-making surface, the biscuit of handling well is put into mould.Mould is put into hot pressing furnace, and at 1800 degrees centigrade, 25MPa compacting 2 hours is cooled to 50 degrees centigrade naturally and comes out of the stove with interior.Blank behind the sintering is put into heat-treatment furnace, flowing nitrogen protection, 1300-1500 degree centigrade be incubated 15 hours altogether after, slowly be cooled to room temperature and come out of the stove.The heating sheet blank of making is processed through surfacing, and subsequent techniques such as soldering are made the silicon nitride heating sheet of high-performance and high reliability.
Relevant isostatic cool pressing: under the normal temperature, powder is placed in the middle of the airtight liquid environment, liquid transfer superhigh pressure makes powder compacting.Because pressure is what to equate in the liquid everywhere, so static pressure such as be.Again owing to being under the normal temperature, so be isostatic cool pressing.Working temperature is static pressure such as temperature in the time of 100-200 ℃.Working temperature is higher then to be high temperature insostatic pressing (HIP).What have reaches 2000 ℃
Traditional spray granulation all is to feed hot blast in drying tower, by contacting with feed liquid is large-area, and transpiring moisture, and obtain the particle of moulding.
Hot pressed sintering is that dry powder is filled in the model, adds the flanging heating again from single shaft direction limit, a kind of sintering method that moulding and sintering are finished simultaneously.Hot-press equipment: hot press commonly used mainly is made up of heating furnace, pressue device, mould and thermometric pressure tester.
Obviously, the foregoing description only is for example of the present invention clearly is described, and is not to be qualification to embodiments of the present invention.For those of ordinary skill in the field, can also make other changes in different forms on the basis of the above description.Here need not also can't give exhaustive to all execution modes.And these belong to conspicuous variation or the change that spirit of the present invention extended out and still are among protection scope of the present invention.