CN1522987A

CN1522987A - Collosol injection molding process for large-scale ceramic plate

Info

Publication number: CN1522987A
Application number: CNA031144926A
Authority: CN
Inventors: 成来飞; 徐永东; 张立同
Original assignee: Northwestern Polytechnical University
Current assignee: Northwestern Polytechnical University
Priority date: 2003-02-17
Filing date: 2003-02-17
Publication date: 2004-08-25

Abstract

The present invention relates to a ceramic sol mould-injecting forming method, and it is mainly used for formation of industrial kiln equipment of large-scale non-oxide shack plate. Said ivnention uses silica sol as binding agent uses ammonium salt as gelling agent, and utilizes the regulation of sidica sol concentration and added quantity of ammonium salt to control gelling time of silica sol, and utilizes the regulation of solid-liquid ratio of ceramic slurry and stirring process to control mould-injecting time, and selects proper demoulding process and drying process so as to ensure completion of mould injection before the ceramic slurry is gelled, and the blank body has a certain wet strength in a certain time after mould injection, and the blank body can not be cracked in the course of drying process.

Description

A kind of large size ceramic sheet material colloidal sol injection moulding forming method

Technical field

The present invention relates to a kind of ceramic sol injection moulding forming method, be mainly used in the moulding of large-scale non-oxide ceramics sheet material, also can be used for the moulding of other simple shape and oxide ceramics member, be specially adapted to the moulding of industrial kiln furnitures such as refractory slab.

Background technology

Existing casting is divided into and directly solidifies casting and directly solidify casting two classes.The core of directly solidifying casting is to utilize in the water base ceramic suspension liquid enzymic catalytic reaction of biological alcohol and substrate, active injection molding when low of enzymic catalytic reaction at low temperatures, and at room temperature enzymic catalytic reaction is active solidifies when higher.The advantage of directly solidifying casting is: (1) does not need to add binding agent, has avoided the degreasing link of time consumption and energy consumption; (2) the suspension original position is solidified, and has the dead size forming ability of complicated shape ceramic component; (3) good uniformity of base substrate, the stability and the reliability height of pottery; (4) the relative density height of base substrate, sintering shrinks little.But the wet base intensity of directly solidifying casting is low, demoulding difficulty, and processing condition are complicated harsh, are unfavorable for large-scale production, and the chemical reagent of control enzymic catalytic reaction can not satisfy environmental requirement.Therefore, directly solidify the small serial production that casting is mainly used in small-sized high reliability ceramic component.Directly solidify the binding agent that casting uses the cement class, before adhesive cures, carry out injection molding, after adhesive cures, carry out the demoulding.The advantage of directly solidifying casting is: (1) blank strength height, be convenient to the demoulding; (2) technology is simple, is beneficial to large-scale production; (3) member only need fully solidify, and does not need to carry out sintering.But the ceramic component that directly solidifies casting can not carry out sintering, and intensity and use temperature are all lower.Therefore, directly solidify the batch process that casting is mainly used in the lower large-scale Fire resistant ceramic part of performance requriements.

Large size ceramic sheet material is a kind of common used in industry kiln furnitures.Has plastic oxide ceramics sheet material for the mullite that uses at lesser temps, trichroite etc., main applying pressure or vibration pressure moulding.Because the non-oxide ceramics kiln furniture material that high temperature such as silicon carbide, silicon nitride use does not have plasticity-fully, the bounce that release produces after the pressure forming produces damage to base substrate, and the base substrate size macrolesion is serious more more.Therefore, though pressure or vibration pressure moulding efficient height are inapplicable to the moulding of large-scale non-oxide ceramics sheet material.Obviously, the moulding of carrying out large-scale non-oxide ceramics sheet material with above-mentioned two kinds of injection moulding forming methods also is inappropriate.

Summary of the invention

The present invention proposes a kind of colloidal sol casting novel method, Fig. 1 is seen in technical process.It comprises following core link:

(1) prepares ceramic size with water base silicon sol;

(2) ammonium salt is added ceramic size as the colloidal sol setting accelerator;

(3) casting of ceramic size, the demoulding and drying.

The concentration of silicon sol and the solid-to-liquid ratio of ceramic size are the important indicators of pulp preparation.In order to improve blank density, reduce the dry shrinkage of base substrate, the solid-to-liquid ratio of ceramic size is high more good more.But solid-to-liquid ratio is high more, and the flowability of slurry is poor more, and casting is difficult more.The concentration of silicon sol is high more, and the ceramic size gelation rate is fast more behind the injection molding.If collosol concentration is too high, local gelling not only may take place in ceramic size in whipping process, and whole gelling may take place before injection molding is finished.Can adjust the concentration of silicon sol by the method for thin up, need consider the volatilization of silicon sol moisture in the slurry whipping process during adjustment.Slurry need carry out abundant stirring degassing, to improve flowability.The slurry air content is low more, and it is good more to flow, and solid-to-liquid ratio is high more.

The key of colloidal sol casting is to adjust the gelation time of silicon sol, and the add-on of the ammonium salt most important influence factor that is gelation time.Because ammonium salt and silicon sol speed of response are very fast, the easy moisture absorption caking of ammonium salt directly adds ammonium salt and causes local gelling easily simultaneously.One of component of ammonium salt and ceramic powder or powder is mixed and made into ammonium salt mixture, not only can prevents the moisture absorption, and can reduce the speed of response of ammonium salt and silicon sol, thereby improve ammonium salt and add and the agglomerative homogeneity.Adopt before ammonium salt adds to stir at a slow speed to prevent to wrap up in gas, adopt to stir fast after ammonium salt adds to prevent gelling.

Should be injection molded rapidly after the ammonium salt adding stirs, injection molding is finished certain hour disposed slurry generation gelling and is formed base substrate.In order to improve injection molding speed, generally should vibrate in the injection molded process.Because moisture still is wrapped in the base substrate after the gelling, the wet tenacity of base substrate is very low.The increase of blank strength is directly proportional with the evaporation rate of moisture in the drying process, thereby drying process must adapt with the evaporation rate of moisture.General adopt dry in the shade, the drying process of air-dry and ladder oven dry.The moisture evaporation excessive velocities if intensity is lower, base substrate will ftracture.Because the drying process moisture evaporation makes base substrate that certain contraction be taken place, reduce friction resistance between base substrate and the supporting plate for preventing that blank cracking from being very important, particularly important for large-sized sheet material.Improve the surface smoothness of supporting plate and between base substrate and supporting plate, add lubricant and all can accomplish this point.

Adopting silicon sol is the advantage that binding agent has three aspects: (1) silicon sol is the common used in industry binding agent, low cost and availability; (2) oven dry back blank strength height is convenient to the carrying and the loading and unloading of large size ceramic sheet material; (3) produce small amounts silicon after the silicon sol gelling, can promote the sintering of non-oxide ceramics kiln furnitures.

In sum, the colloidal sol casting requires injection molding speed fast, and blank strength is very low brings very big difficulty to the demoulding, thereby mainly is suitable for the moulding of simple shape ceramic components such as sheet material.But because the colloidal sol injection molding and forming technology is simple, and is not subjected to the restriction of appointed condition, compare, have tangible technology and economic advantages aspect the moulding of large size ceramic sheet material with other forming methods.

Description of drawings

Fig. 1 is the technical process of colloidal sol injection moulding forming method.

Embodiment

Below, be further described of the present invention in conjunction with the accompanying drawings and embodiments.

Embodiment one:

Selection is of a size of 800 * 600 * 20mm ³Large-scale silicon nitride combined silicon carbide pottery refractory slab be that typical members describes the colloidal sol injection moulding forming method.Silicon nitride is to use silica flour process nitrogenizing reaction to generate, thereby ceramic powder is the compound of carborundum powder and silica flour.The weight ratio of carborundum powder is 70% in the compound, and the weight ratio of silica flour is 30%.Wherein the particle diameter of silica flour is 325 orders, and the particle diameter of carborundum powder has three kinds in 46 orders, 90 orders and 180 orders, and weight ratio is respectively 20%, 50% and 30%.With ceramic raw material by forming and after granularity carried out proportioning, mixed grind obtained uniform ceramic powder in 30 minutes in the mulling stone roller.The silicon sol of selecting commercially available silicon oxide-containing 28～30% is a binding agent, is that 1: 1 water dilutes with weight ratio before using.Selecting commercially pure ammonium chloride is jelling agent, is mixed and made into mixing gelling agent with silica flour before using.To mix in 1: 3 ratio with silica flour through exsiccant ammonium chloride, and roll evenly and be placed in the loft drier.The ceramic powder of weighing 20Kg places L shaped stirrer, stirs with 60 rev/mins rotating speeds, adds the silicon sol through dilution while stirring.After stirring 30 fens, the rotating speed of stirrer is increased to 100 rev/mins, adds mixing gelling agent simultaneously, add-on is 1.5% of a ceramic powder weight.Stir and to pour into a mould rapidly in the mould of ceramic size on being installed on shaking table afterwards in 5 minutes, vibration while pouring into a mould.Cast finishes to carry out the demoulding after about 30 minutes.The method of the demoulding is: mould and shaking table will be of a size of 900 * 700 * 5mm after breaking away from ³Simple glass cover on mould, cover wood frame again; The whole counter-rotating of mould and supporting plate is removed mould after placing mould and base substrate on the glass supporting plate.At room temperature dried in the shade respectively earlier after the demoulding 8 hours and air-dry 8 hours, then 60 ℃ of oven dry 8 hours, at last 80 ℃ of oven dry 8 hours, the oven dry face that must change base substrate with supporting plate counter-rotating in each road drying process once, dry back base substrate can satisfy the requirement of carrying and loading of kiln.Adopt above-mentioned drying process and glass and the compound supporting plate of wooden frame, can guarantee that base substrate does not ftracture substantially.The effect of glass is to reduce the base substrate deflation resistance, and the effect of wooden frame is a carry load.The relative linear shrinkage ratio of dry back base substrate is 0.6%, and the absolute linear shrinkage amount of length direction is 5mm.Through after nitridation sintered, refractory slab can use more than 100 heats in 1100 ℃～1300 ℃ Industrial Stoves.

Claims

1, a kind of colloidal sol injection moulding forming method of large size ceramic sheet material, it is characterized in that: use silicon sol as binding agent, use ammonium salt as jelling agent, control the gelation time of silicon sol by the add-on of adjusting thickness of silica gel and ammonium salt, by solid-to-liquid ratio and the stirring technique control injection molding time of adjusting ceramic size, select suitable releasing process and drying process, the assurance ceramic size is finished injection molding before gelling, base substrate has one wet tenacity in the certain hour behind injection molding, base substrate does not ftracture in drying process, realizes the moulding of low-cost and high-strength large-scale ceramic board base substrate.

2, the method for claim 1 is characterized in that: use silicon sol as binding agent, making water is the concentration of thinner control silicon sol, guarantees that local gelling does not take place in whipping process ceramic size.

3, the method for claim 1 is characterized in that: use ammonium salt as jelling agent, use ceramic powder to prevent the conglomeration of the ammonium salt moisture absorption as dispersion agent, guarantee that ammonium salt adds and the agglomerative homogeneity.

4, the method for claim 1 is characterized in that: ceramic size adopts before and after ammonium salt adds at a slow speed and quick two kinds of different stirring techniques, guarantees that ceramic size has the competent injection molding time.

5, the method for claim 1 is characterized in that: use glass and wooden frame composite pallet and add lubricant between base substrate and supporting plate, reduce the deflation resistance of body drying process, prevent blank cracking.

6, the method for claim 1 is characterized in that: use that room temperature is dried in the shade, the technology of air-dry and ladder oven dry, it is synchronous that the moisture evaporation that guarantees base substrate and intensity increase, and prevents blank cracking.