CN104211407A - Process for forming large-size complex-shaped silicon carbide ceramic biscuit - Google Patents
Process for forming large-size complex-shaped silicon carbide ceramic biscuit Download PDFInfo
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- CN104211407A CN104211407A CN201410454161.8A CN201410454161A CN104211407A CN 104211407 A CN104211407 A CN 104211407A CN 201410454161 A CN201410454161 A CN 201410454161A CN 104211407 A CN104211407 A CN 104211407A
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Abstract
The invention relates to a process for forming large-size complex-shaped silicon carbide ceramic biscuits and belongs to the field of forming processing of materials. In the process, SiC powder is used as a main raw material and absolute ethyl alcohol is used as a solvent, the process comprises the following steps of: mixing raw materials, drying, granulating, carrying out dry pressing and cold isostatic compaction; drying a green body, and then processing into a complex shape on a digital milling machine by adopting a special cutter; then unsticking a completely processed biscuit. The process disclosed by the invention prevents the process problems of complication in process, difficulty in process control, high demoulding and drying difficulty, long drying time, low efficiency and the like when the large-size complex-shaped silicon carbide ceramic biscuits are prepared through the traditional gel casting process and other processes and solves the problems of high machining difficulty since sintered silicon carbide ceramics have high rigidity and friability, thereby greatly enhancing the qualification rate and production efficiency of the large-size complex-shaped silicon carbide ceramic biscuits.
Description
Technical field
The invention belongs to technical field of material formation, particularly relate to a kind of moulding process of big-size complicated shape ceramics biscuits of carbonized bricks.
Background technology
SiC ceramic is the premium properties such as specific rigidity is large, Heat stability is good owing to having, and thus can become Recent study focus as the basal body of reflector material in the fields such as aerospace through optical manufacturing rear surface excellent performance.For increasing the specific rigidity of reflector body as far as possible, needing to remove the mirror base material not participating in optical imagery in body material, thus high light-weighted loss of weight requirement is proposed to body material.Because the hardness and fragility that sinter rear SiC ceramic are comparatively large, mechanical processing difficulty is higher, therefore needs badly and finds a kind of simply shaping and complete processing that can realize sintering front SiC ceramic biscuit near net-shape.Big-size complicated shape SiC ceramic biscuit common at present generally adopts Gel-casting process.It is very unfavorable to industrial production that how wayward, the dry demoulding difficulty of Gel-casting process restraining factors due to SiC ceramic biscuit be large, time of drying is long, yield rate is low etc.
Summary of the invention
The object of the present invention is to provide a kind of moulding process of big-size complicated shape ceramics biscuits of carbonized bricks, solve the moulding process of existing big-size complicated shape ceramics biscuits of carbonized bricks, avoid adopting gel injection molding and forming technology complicated, that be difficult to demoulding drying, inefficiency, and adopt special isostatic cool pressing, drying and process for machining, realize the precisely shaping of the complicated ceramics biscuits of carbonized bricks (500mm ~ 1m) of large size.
The present invention adopts isostatic cool pressing+drying+mach process means, greatly can improve the shaping efficiency of big-size complicated shape SiC ceramic biscuit.Cold isostatic compaction after SiC powder batch mixing can be ensured on the one hand the homogeneity of SiC biscuit, improve biscuit density and intensity; Coordinate special drying system on the other hand, SiC biscuit can be made to reach machinable intensity, numerically-controlled machine is adopted to process SiC biscuit, coordinate specific machined parameters, to ensure base substrate flawless and internal stress in the whole course of processing, and SiC biscuit can be made to obtain higher shape-holding property not available for other molding mode.
The invention provides silicon carbide component forming of green body and the complete processing of big-size complicated shape, adopt this technique can obtain near net-shape, flawless and defect, ceramics biscuits of carbonized bricks that the accuracy of shape is high.
The present invention selects SiC powder to be main raw material, take dehydrated alcohol as solvent, through batch mixing, oven dry, granulation, dry-pressing, cold isostatic compaction, will in CNC milling machine, special tool after green compact drying, be adopted to process complicated shape, the base substrate unsticking then will processed.Present invention, avoiding that the complex process existed when the techniques such as traditional gel injection prepare big-size complicated shape ceramics biscuits of carbonized bricks is wayward, the dry difficulty of demoulding is large, time of drying length, the technological problems such as inefficiency, and after solving sintering silicon carbide ceramics due to hardness, fragility is large and problem that mechanical processing difficulty is large, greatly can improve qualification rate and the production efficiency of big-size complicated shape ceramics biscuits of carbonized bricks.Specifically comprise the steps:
(1) batch mixing: take dehydrated alcohol as solvent, proportionally puts into the slurry that ball grinder mixing 3-10h obtains solid load 46 ~ 52% successively by SiC powder and sintering aid, binding agent etc.;
(2) spraying dry: after the slip that ball milling is good is poured out, de-bubble also adds appropriate organic bases to carry out adjust ph is between 8 ~ 11; Spray-dired inlet temperature is at 140-270 DEG C, and air outlet temperature is at 55-85 DEG C, and rotating speed 18000-30000rpm spraying dry obtains powder;
(3) shaping: powder is put into rubber coating, adopt cold isostatic compaction technique, pressurize 5-15min, then release under the pressure of 120-200MPa, obtain SiC ceramic green compact;
(4) dry: the SiC ceramic green compact that isostatic cool pressing obtains to be put into loft drier and is slowly evenly warming up to 100 ~ 300 DEG C, insulation 2-6h;
(5) drawing also machining: adopt the graphics softwares such as AutoCAD to draw out the dimensioned drawing of silicon carbide green part, after grinding machine polishes, adopt numerically-controlled machine to carry out machining to silicon carbide ceramics green compact according to this figure;
(6) unsticking: the base substrate after machining is put into unsticking stove and carries out unsticking.
Preferably, binding agent described in step (1) is the mixture of PVA and PEG of molecular weight between 1500-4000, its molecular weight should not be too high or too low, its blending ratio is (1 ~ 2): (0.5 ~ 1), add-on is 1.5% ~ 5.0%, more preferably 0.3%-2%, effect is the plasticity-ensureing powder, reduce the friction between powder granule, increase the mobility of pelletizing, to ensure filling ratio and the loose density of powder in cold isostatic compaction process, general powder loose density is at 0.7-1.0g/cm
3between, thus ensure that shaping rear SiC green compact can reach mach intensity.
Preferably, the organic bases described in step (2) adopts the one of Tetramethylammonium hydroxide or Trimethylamine 99 or thanomin, and adjust ph is to 8-11 scope, and then adopt spray-drying tower mist projection granulating, the powder loose density of acquisition should at 0.7 ~ 1.0g/cm
3;
Preferably, the isostatic cool pressing technique described in step (3), the large palpulus of pressure of isostatic cool pressing is moderate: it is large that pressure just causes too greatly base substrate to shrink, and after release, bounce-back is serious; Too small pressure can make SiC ceramic biscuit density and intensity lower, cause in mechanical processing process and occur collapsing the problem such as limit, crackle, generally within the scope of 120-210MPa.Dwell time generally gets 5-10min and is advisable; After isostatic cool pressing technique, green density controls at 1.7-2.0g/cm
3.
Preferably, in described step (5), green compact are polished after finding reference plane accurately, different process tools is selected according to different die cavities, the design parameter of numerically-controlled machine processing will be determined according to blank shape, wall thickness, and the general depth of cut should not be too fast, not higher than 2mm/min, and according to processing stage, processing speed is adjusted in good time, as the processing speed that just slows down during thin-walled.
Preferably, the drying system described in step (4) and base substrate size, paste composition (comprising sintering aid) are relevant, and general requirement slowly heats up (being no more than 5 DEG C/min);
Preferably, the unsticking system described in step (6) is 600-800 DEG C of insulation 2-6h.
Beneficial effect of the present invention
The moulding process of big-size complicated shape ceramics biscuits of carbonized bricks of the present invention, different from Gel-casting process in the past, the slurry that binding agent obtains solid load 46 ~ 52% is added when ball mill mixing, adjust ph and after de-bubble spraying dry obtain powder, then pelletizing cold isostatic compaction is obtained silicon carbide biscuit; Adopt suitable drying system, biscuit intensity is reached can machining intensity; Draw biscuit drawing, and input CNC milling machine, special parameter is set machining is carried out to SiC biscuit; The SiC biscuit with complicated shape is put into stove unsticking; The flawless of the near net-shape finally obtained and the big-size complicated shape SiC ceramic biscuit of internal stress.Owing to adding suitable binding agent during batch mixing, and prepare the higher slurry of solid load, make spraying dry obtain the high spheroidal particle powder of intensity, the SiC ceramic biscuit obtained after isostatic cool pressing is more fine and close, and intensity is higher; Be equipped with rational drying system according to material component afterwards, make SiC ceramic green compact possess machinable intensity; By making after cold isostatic compaction, comparatively gel injection molding and forming technology is more simple, and the last biscuit shape obtained is more accurate.
Accompanying drawing explanation
Fig. 1 is preparation technology's schema of big-size complicated shape ceramics biscuits of carbonized bricks of the present invention.
Embodiment
Below in conjunction with specific embodiment, the present invention is further described in detail.
SiC raw material granularity D50=3-10 μm, purity is more than 98%; The various chemical reagent added in batch mixing and granulation process are analytical pure.
The moulding process flow process of the big-size complicated shape SiC ceramic biscuit according to Fig. 1, the process of specific embodiment is as follows:
By 4000g SiC powder, binding agent 60g PEG and 50g PVA, appropriate sintering aid and dispersion agent etc. add in ball grinder, and with SiC ball for mill is situated between, dehydrated alcohol is solvent, ball milling 6h, obtains slurry.
Poured out by the slurry obtained after batch mixing, add appropriate organic bases adjust ph to 9.5, slowly stir 2h de-bubble, spray-dired inlet temperature is set to 190 DEG C, and air outlet temperature is at 75 DEG C, and rotating speed 13000rpm, obtaining loose density after spraying dry is 0.86g/cm
3powder.
Then load in rubber coating by powder, buckle conformal cover, put into cold isostatic press, pressurize 8min under the pressure of 170MPa, the density obtaining SiC ceramic biscuit is 1.87g/cm
3;
SiC ceramic biscuit is inserted in loft drier in 180 DEG C of insulation 6h;
By SiC ceramic green compact dimensioned drawing input numerically-controlled machine, green compact are polished on grinding machine after finding processing datum accurately, carry out corresponding machining according to drawing, need to carry out controlled working speed according to the geomery of green compact in the course of processing, the processing depth of cut is no more than 1.2mm/min.
Then SiC ceramic biscuit is put into stove unsticking, temperature rise rate is 3 DEG C/min, is incubated 1h and 3h respectively 150 DEG C and 700 DEG C.Base substrate temperature can complete the unsticking of big-size complicated shape SiC ceramic biscuit after being down to room temperature from 700 DEG C.
Claims (5)
1. a moulding process for big-size complicated shape ceramics biscuits of carbonized bricks, is characterized in that, comprises the steps:
(1) batch mixing: take dehydrated alcohol as solvent, proportionally puts into the slurry that ball grinder mixing 3-10h obtains solid load 46 ~ 52% successively by SiC powder and sintering aid, binding agent;
(2) spraying dry: after the slip of step (1) is poured out, de-bubble also adds organic bases to carry out adjust ph is between 8 ~ 11; Spray-dired inlet temperature is at 140-270 DEG C, and air outlet temperature is at 55-85 DEG C, and rotating speed 18000-30000rpm spraying dry obtains powder;
(3) shaping: the powder of step (2) is put into rubber coating, adopt cold isostatic compaction technique, pressurize 5-15min, then release under the pressure of 120-200MPa, obtain SiC ceramic green compact;
(4) dry: the SiC ceramic green compact that isostatic cool pressing obtains to be put into loft drier and is warming up to 100 ~ 300 DEG C, insulation 2-6h;
(5) drawing also machining: adopt AutoCAD graphics software to draw out the dimensioned drawing of silicon carbide green part, after grinding machine polishes, adopt numerically-controlled machine to carry out machining to silicon carbide ceramics green compact according to this figure;
(6) unsticking: the base substrate after machining is put into unsticking stove and carries out unsticking.
2. technique according to claim 1, it is characterized in that, binding agent described in step (1) is the mixture of PVA and PEG of molecular weight between 1500-4000, its molecular weight should not be too high or too low, its blending ratio is (1 ~ 2): (0.5 ~ 1), and add-on is 1.5% ~ 5.0%.
3. technique according to claim 1, it is characterized in that, organic bases described in step (2) adopts the one of Tetramethylammonium hydroxide or Trimethylamine 99 or thanomin, and adopt spray-drying tower mist projection granulating, the powder loose density of acquisition should at 0.7 ~ 1.0g/cm
3.
4. technique according to claim 1, is characterized in that, after isostatic cool pressing technique, green density controls at 1.7-2.0g/cm
3.
5. technique according to claim 1, is characterized in that, the unsticking temperature described in step (6) is 600-800 DEG C, insulation 2-6h.
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| CN201410454161.8A CN104211407B (en) | 2014-09-05 | 2014-09-05 | A kind of moulding process of big-size complicated shape ceramics biscuits of carbonized bricks |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105984019A (en) * | 2015-02-13 | 2016-10-05 | 苏州博恩瑞科生物材料有限公司 | Pressing forming method of ceramic friction pair |
| CN106478106A (en) * | 2016-10-09 | 2017-03-08 | 北京钢研新冶精特科技有限公司 | Prepare the manufacture method of speculum silicon carbide granulating powder |
| CN107538603A (en) * | 2017-08-24 | 2018-01-05 | 北京钢研新冶精特科技有限公司 | A kind of processing method of carborundum biscuit |
| CN107932706A (en) * | 2017-10-27 | 2018-04-20 | 中国科学院长春光学精密机械与物理研究所 | Gel casting forming meter level ceramics biscuits of carbonized bricks non-resistance drying device and method |
| CN109016100A (en) * | 2018-06-29 | 2018-12-18 | 上海卡贝尼精密陶瓷有限公司 | Advanced ceramics green compact precision machining method and advanced ceramics product and making method |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1986492A (en) * | 2006-12-15 | 2007-06-27 | 武汉理工大学 | Preparing process of great size energy-storing dielectric ceramic |
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2014
- 2014-09-05 CN CN201410454161.8A patent/CN104211407B/en not_active Expired - Fee Related
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1986492A (en) * | 2006-12-15 | 2007-06-27 | 武汉理工大学 | Preparing process of great size energy-storing dielectric ceramic |
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105984019A (en) * | 2015-02-13 | 2016-10-05 | 苏州博恩瑞科生物材料有限公司 | Pressing forming method of ceramic friction pair |
| CN106478106A (en) * | 2016-10-09 | 2017-03-08 | 北京钢研新冶精特科技有限公司 | Prepare the manufacture method of speculum silicon carbide granulating powder |
| CN107538603A (en) * | 2017-08-24 | 2018-01-05 | 北京钢研新冶精特科技有限公司 | A kind of processing method of carborundum biscuit |
| CN107932706A (en) * | 2017-10-27 | 2018-04-20 | 中国科学院长春光学精密机械与物理研究所 | Gel casting forming meter level ceramics biscuits of carbonized bricks non-resistance drying device and method |
| CN107932706B (en) * | 2017-10-27 | 2018-12-04 | 中国科学院长春光学精密机械与物理研究所 | Gel casting forming meter level ceramics biscuits of carbonized bricks non-resistance drying device and method |
| CN109016100A (en) * | 2018-06-29 | 2018-12-18 | 上海卡贝尼精密陶瓷有限公司 | Advanced ceramics green compact precision machining method and advanced ceramics product and making method |
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