Manufacture method with silicon nitride heat generating body of higher reliability and fail safe
The application divides an application, the application number of original application: 201010582116.2, the applying date: 2010-12-09, invention and created name: 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 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, the nitride such as ZrN.The high-performance silicon nitride ceramics has excellent electricity, calorifics and the mechanical property such as insulation, high-strength, high temperature resistant, resistance to oxidation, heat shock resistance and high-termal conductivity.
Silicon nitride heating plate is a kind of device in conjunction with high-performance silicon nitride ceramics matrix and powerful high-temperature metal heating wire of long-life.Have volume little, the large and heat efficiency high of power, the while also is proved to be a kind of safe and reliable heating system.After direct-electrifying, 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, the 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 heating sheet material in market more, and surface distributed has the phenomenons such as bulk blackspot, black patch from the appearance, and 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 surface uniform or uneven distribution pore more have surface distributed that the phenomenons such as bulk blackspot, black patch are arranged.This be mainly in the hot pressed sintering process because biscuit directly contacts with graphite, carbon infiltrates along liquid channel, dissolves in liquid phase, or reacts with silicon nitride and produce.The insulation property of the deteriorated material of infiltration meeting of carbon reduce safety 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 large, the inadequate microstructure of liquid phase crystallization, affects the useful life of basis material.
Summary of the invention
The technical problem to be solved in the present invention is to provide the manufacture method of the simple silicon nitride heat generating body of a kind of technique, 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 are inserted in 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, the metal heating wire is imbedded in described formulation material dry-pressing formed, then the isostatic cool pressing by 180-220MPa is further compressing, and pressurize 3-10 minute, to make biscuit; Described metal heating wire is molybdenum filament;
Step 3, apply one deck boron nitride separator post-drying at described biscuit surface uniform;
Step 4, then carry out hot pressed sintering, 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, then naturally cool to room temperature.
Further, described boron nitride separator is to mix thick shape slurry rear and that absolute ethyl alcohol reconciles into 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 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, the 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 and high-temperature metal heating wire form, and through forming of green body, makes compact silicon nitride base heater after hot pressed sintering and 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 technique 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 grain boundary glassy phase, has greatly improved device reliability and fail safe.(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 again oxidative phenomena with absolute ethyl alcohol (99.9% purity).Do not add any macromolecule modifier in 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 through the sticking technique of row, be got rid of polymeric additive.In general, under oxygen atmosphere row sticking can get rid of to greatest extent and burn polymeric additive in carbon.And that silicon nitride can only be arranged under vacuum or nitrogen protection atmosphere is sticking, thoroughly eliminates carbon more difficult, is evenly distributed in 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 isostatic cool pressing technique to prepare high-intensity biscuit.(3) in the present invention, the biscuit surface uniform 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 after hot pressed sintering, and the material stress of silicon nitride heat generating body is larger, is slow cooling 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 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 content of the present invention is more likely to be clearly understood, below the specific embodiment and by reference to 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 in 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 the present embodiment is comprised of silicon nitride heating and the high-temperature metal heating wire of being located in silicon nitride heat generating body.The metal heating wire is 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 are inserted in absolute ethyl alcohol by weight 0.96:0.04 to 0.80:0.20 mix (specifically can adopt ballmillmixer to mix), after batch mixing 10-72 hour, make formulation material through mist projection granulating;
Step 2, the metal heating wire is imbedded in described formulation material dry-pressing formed, then the isostatic cool pressing by 180-220MPa is further compressing, and pressurize 3-10 minute, to make biscuit;
Step 3, apply one deck boron nitride separator post-drying at described biscuit surface uniform;
Step 4, then carry out hot pressed sintering, 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, then naturally cool to room temperature, at last at metal heating wire two ends welding electrode.
Described boron nitride separator is to mix thick shape slurry rear and that absolute ethyl alcohol reconciles into 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 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 the 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 evenly to mix 72 hours, then insert in explosion-proof mist projection granulating tower mist projection granulating and make formulation material.
Formulation material is poured in mould, then the metal heating wire is imbedded in powder dry-pressing formed, 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 process 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 the uniform boron nitride separator of biscuit surface-coated one deck, drying and processing.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 naturally is cooled to 50 degrees centigrade and comes out of the stove with interior.Blank after sintering is put into heat-treatment furnace, flowing nitrogen protection, 1300-1500 degree centigrade be incubated altogether 15 hours after, slow cooling to room temperature is come out of the stove.The fever tablet blank of making is processed through surfacing, and the subsequent techniques such as soldering are made the silicon nitride heating plate of high-performance and high reliability.
Relevant isostatic cool pressing: under normal temperature, powder is placed in the middle of airtight liquid environment, liquid transfer superhigh pressure makes powder compacting.Because in liquid, pressure equates everywhere, so the static pressure such as be.Again owing to being under normal temperature, so be isostatic cool pressing.Working temperature is the static pressure such as temperature in the time of 100-200 ℃.Working temperature is higher is high temperature insostatic pressing (HIP).What have reaches 2000 ℃
Traditional spray granulation is all to pass into 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 model, then adds flanging heating, a kind of sintering method that moulding and sintering are completed simultaneously from single shaft direction limit.Hot-press equipment: hot press commonly used mainly is comprised of heating furnace, pressue device, mould and thermometric pressure tester.
Obviously, above-described embodiment is only for example of the present invention clearly is described, and is not to be restriction 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 all execution modes exhaustive.And these belong to apparent variation or the change that spirit of the present invention extended out and still are among protection scope of the present invention.