SUMMERY OF THE UTILITY MODEL
The utility model aims at overcoming the problems of inhomogeneous sintering heat, abnormal ceramic chip edge color and dispersed sintering resistance at different positions in the prior art.
Therefore, the utility model provides a PTC ceramic sintering sagger, include: the graphite bowl comprises a bowl body, an upper cover plate and a plurality of graphite strips; wherein the edge of the opening at the top of the bowl body and the bottom of the upper cover plate are respectively provided with a plurality of preformed holes which correspond one to one; and the plurality of graphite strips are respectively inserted between the preformed holes in one-to-one correspondence.
Specifically, the bottom of the upper cover plate is provided with a protruding part matched with the opening of the pot body, and when the graphite strips are pulled away, the upper cover plate falls down and forms a sealing structure with the pot body.
Specifically, the upper cover plate is a mullite upper cover plate or an alumina upper cover plate.
Specifically, the pot body is a mullite pot body or an alumina pot body.
Specifically, the bottom layer of the pot body is padded with a zirconia plate.
Specifically, the thickness of the zirconia plate is more than or equal to 6 mm.
Compared with the prior art, the utility model has the advantages of it is following and beneficial effect:
the PTC ceramic sintering sagger provided by the utility model ensures the air permeability of the sintering sagger in the glue discharging stage by utilizing the graphite strips which play a supporting role between the upper cover plate and the sagger body, so that organic matters added in the granulation process can be fully discharged after thermal decomposition; after the glue discharging stage is finished, the temperature is raised, the graphite strips are gradually oxidized and consumed, the upper cover plate falls down to form a sealing structure with the pot body, and after the graphite strips enter the sintering high-temperature zone, the sealed sintering saggar ensures the consistency of the internal temperature, avoids the abnormal color of the edge of the PTC ceramic piece caused by the heat radiation of the high-temperature zone, and improves the concentration of the sintering resistance.
The present invention will be described in further detail with reference to the accompanying drawings.
Detailed Description
The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative efforts belong to the protection scope of the present invention.
In the description of the present invention, it is to be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like, indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplicity of description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore, should not be construed as limiting the present invention; in the description of the present invention, "a plurality" means two or more unless otherwise specified.
Referring to fig. 1 to 4, the present invention provides a PTC ceramic sintering sagger, comprising: the device comprises an upper cover plate 1, a bowl body 5 and a plurality of graphite strips 4; wherein the edge of the opening 6 at the top of the bowl body 5 and the bottom of the upper cover plate 1 are respectively provided with a plurality of preformed holes 3 which correspond one to one; the graphite strips 4 are respectively inserted between the preformed holes 3 which are in one-to-one correspondence. During actual use, stacking the formed PTC blank sheets in the pot body 5, spraying 50-80-mesh zirconium powder in gaps between the blank sheets in order to prevent the blank sheets from reacting with the pot body 5, blocking the contact surfaces of the blank sheets and the pot body 5 by using zirconium oxide plates with the thickness of 2-3mm, installing graphite strips 4 with corresponding specifications into the preformed holes 3 at the top of the pot body 5, and closing the upper cover plate 1 according to the positions of the corresponding preformed holes 3; after the blank sheets are placed, putting the PTC ceramic sintering sagger into a sintering furnace, raising the temperature to a thermal decomposition area at a constant speed, and preserving the temperature for a period of time to ensure that the organic additive is fully heated and decomposed; then heating to a glue discharging temperature area at a constant speed, preserving heat for a period of time, and discharging glue, wherein a gap is formed between the upper cover plate 1 and the pot body 5 due to the supporting effect of the graphite strips 4, so that the thermal decomposition product of the organic additive can be discharged out of the sintering sagger through the gap; after the binder removal, the temperature is continuously increased, so that the graphite strips 4 are completely oxidized and consumed at high temperature, the upper cover plate 1 forms a sealing structure with the pot body 5 after falling under the action of the gravity of the upper cover plate, and after entering a sintering high-temperature area, the sealed sintering sagger ensures the consistency of the internal temperature; and after the PTC ceramic is sintered, naturally cooling, and opening the sintering sagger to obtain a ceramic finished product.
Furthermore, the bottom of the upper cover plate 1 is provided with a protruding part 2 which is matched with the opening 6 of the pot body 5, when the graphite strips 4 are completely oxidized and consumed at high temperature, the upper cover plate 1 falls down under the action of self gravity, and the protruding part 2 is buckled into the opening 6 of the pot body 5 to form a sealing structure with the pot body 5, so that the sealing performance of the sagger in the sintering process is improved.
Specifically, the upper cover plate 1 and the bowl body 5 may be made of a refractory material such as mullite or alumina.
In order to avoid the PTC green compact from reacting with the bottom of the pot body 5 under the condition of ultrahigh temperature, affecting the product quality and causing sagger loss, before the PTC green compact is stacked into the green compact, a zirconia plate is stacked on the bottom layer of the pot body 5 to support the green compact, and the thickness of the zirconia plate is preferably more than or equal to 6 mm.
The effect of the sintered PTC ceramic sagger of the present invention will be studied by the following specific examples.
Example 1:
the using method of the PTC ceramic sintering sagger comprises the following steps:
s1, manufacturing an upper cover plate and a pot body of the square PTC ceramic sintering sagger by using mullite, wherein the four sides of the opening at the top of the pot body are respectively provided with a preformed hole, and the bottom of the upper cover plate is provided with the preformed holes corresponding to the preformed holes of the pot body.
S2, stacking a zirconia plate with the thickness of 6mm on the bottom layer of the pot body;
s3, stacking the molded PTC blank sheets in the pot body, spraying 50-80-mesh zirconium powder in gaps between the blank sheets, blocking the contact surfaces of the blank sheets and the pot body by using zirconium oxide plates with the thickness of 2-3mm, installing graphite strips with corresponding specifications into preformed holes in the top of the pot body, and closing an upper cover plate according to the positions of the corresponding preformed holes;
s4, in order to obtain PTC ceramics with compact structure and uniform grain size, the following temperature rise process is adopted for glue removal and sintering: putting the PTC ceramic sintering sagger into a sintering furnace, uniformly heating to 350 +/-10 ℃ at a speed of 3-5 ℃/min, and preserving heat for 32 +/-5 min to fully heat and decompose the organic additive; heating to 600 + -5 deg.C at constant speed of 3-5 deg.C/min, and maintaining for 120 + -5 min; heating to 850 + -5 deg.C at constant speed of 3-5 deg.C/min, and maintaining for 45 + -5 min; heating to 1100 + -5 deg.C at constant speed of 3-5 deg.C/min, and maintaining for 45 + -5 min; raising the temperature to 1265-; uniformly cooling to 1240 +/-5 ℃ at the speed of 2-3 ℃/min, and preserving heat for 45 +/-5 min; and uniformly cooling to 1140 +/-5 ℃ at the speed of 3-5 ℃/min, preserving heat for 45 +/-5 min, finishing sintering the PTC ceramic, and naturally cooling to obtain a finished product.
Comparative example 1:
the same procedure as in example 1 was followed except that a conventional non-sealing type PTC ceramic sintering sagger was used in step S1.
The finished PTC ceramics obtained by firing in example 1 and comparative example 1 were examined for resistance, Curie temperature, pressure resistance and appearance. The withstand voltage is as an example that the resistance value is 0.3-0.4K omega, the withstand voltage performance of the finished products of the embodiment 1 and the comparative example 1 is required to pass 380VAC, 3min, and the Curie temperature @ 2R 25 is between 250 ℃ and 260 ℃; the results of the resistance distribution are shown in Table 1.
TABLE 1 PTC ceramic finished product resistance distribution
Although the ceramic products of example 1 and comparative example 1 both satisfied the pressure resistance and the curie temperature, as can be seen from table 1, the resistance values of the products fired by the sintered sagger of PTC ceramic provided by the present invention in example 1 and example 2 were all within 0.2-0.9k Ω, which satisfied the requirements of PTC ceramic, and the resistance values of more than 80% of the products in example 1 were between 0.53-0.60k Ω, while the resistance value of 0.67% of the products in comparative example 1 was 0.90k Ω, which did not satisfy the production requirements, and the sintered resistance values of different parts were more dispersed than that of example 1; statistics of the number of the ceramic products with abnormal edges in the embodiment 1 and the comparative example 1 shows that the ceramic product in the embodiment 1 has no abnormal edge color basically, while the color abnormal rate in the comparative example 1 is as high as about 3 percent, so that the PTC ceramic sintering sagger provided by the invention can reduce the color abnormal rate of the edges of the PTC sheets when the ceramic is sintered.
In conclusion, the PTC ceramic sintering sagger provided by the invention utilizes the graphite strips which play a supporting role between the upper cover plate and the sagger body to make gaps for the sintering sagger, so that the air permeability of the sintering sagger in the glue discharging stage is ensured, and organic matters added in the granulating process can be fully discharged after thermal decomposition; after the glue discharging stage is finished, the temperature is raised, so that the graphite strips are gradually oxidized and consumed, the upper cover plate falls down to form a sealing structure with the pot body, and after the graphite strips enter a sintering high-temperature region, the sealed sintering sagger ensures the consistency of the internal temperature, avoids the color abnormality of the edge of the PTC sheet caused by the heat radiation of the high-temperature region, and improves the concentration of the sintering resistance; the use method of the PTC ceramic sintering sagger ensures that organic additives are discharged through sectional heating, the sagger forms a closed structure in a high-temperature area after graphite is oxidized and consumed, the sintering block is subjected to high sintering temperature and then is subjected to heat preservation at low temperature, rapid movement of a crystal boundary is inhibited, a sintering block with fine and uniform crystal grains can be obtained, and finally the PTC ceramic with compact structure, uniform crystal grain size, uniform resistance distribution and low edge color abnormal rate is obtained.
The above illustration is merely an illustration of the present invention, and does not limit the scope of the present invention, and all designs identical or similar to the present invention are within the scope of the present invention.