The exhaust emission of automobiles is a major environmental problem faced by the whole society. At present, a domestic research institute has developed a precious metal-containing slurry that is applied to a honeycomb ceramic substrate in an exhaust gas discharge device of an automobile to catalytically convert the exhaust gas into a non-toxic and harmless gas. This slurry has a high viscosity and is acidic, l! About m suspension. In order to promote the application of this technology, the first new type of vacuum coating machine in the country emerged.
2 Current Status of Domestic Honeycomb Ceramic Substrate Coating Methods Currently, most of the traditional coating methods in China are natural dipping methods. The slurry is slowly coated along many small channels in the axial direction of the ceramic substrate under the action of the capillary pores of the honeycomb ceramic substrate. The disadvantage of this method is that the coating cycle is long, the entire coating takes several minutes, the production efficiency is low, and it is not suitable for large-scale production.
The coating effect is poor, the interior of the substrate is pot-shaped at the coating height, the middle is low, and the surrounding is high, and the center core cannot be coated with a slurry. In addition, slurry deposition and clogging of channel holes can occur during coating.
The coating cost is high. The outer wall of the pottery base is coated with the slurry during the coating process several times. In the normal use of the honeycomb carton basement, the car exhaust does not come into contact with the outer surface of the pottery base body, and the outer surface is greatly exposed. The coated precious metals are wasted in vain, resulting in an excessively high price of exhaust emission devices.
3 Advantages and Features of the New Vacuum Coating Machine Compared with the traditional coating equipment, the new vacuum coating machine has the following advantages: It can make all channel pore walls inside the honeycomb ceramic substrate coated uniformly and thinly. A layer of catalyst slurry, repeated coating or leak coating in the matrix is ​​very rare or even does not occur. Holes will not be blocked, nor will the outer wall of the base be coated with a slurry over a large area.
All honey-comb hole channels are kept unblocked, which ensures that the important indexes of the ceramic substrate are good ventilation performance and the catalytic treatment of exhaust gas is good.
Slurry deposition does not occur inside the substrate, so there is no need to clean the substrate and the coating process is simplified.
The amount of slurry is just right, and the coated product is cost-effective and easy to use.
The vacuum generation system does not use a vacuum pump, but uses a plurality of vacuum generators for reasonable combination, and can easily perform switching of multiple vacuum degrees. The vacuum generation system acts on the workpiece (ceramic substrate) after passing through the vacuum storage tank, and the degree of vacuum is stable.
Coating time is short, only a few seconds + more than ten seconds, high productivity.
The machine tool has a compact structure, low noise, easy installation of the workpiece, simple operation of the machine tool, and low operator requirements.
The unique design of the vacuum system is very low due to the vacuum requirements of several vacuum levels, between 0 and -4 kPa, and the "vacuum level" vacuum level is >1 level vacuum level, and the fluctuation is very small. The vacuum system consists of a gas pressure stabilization section (gas multi-stage filtration, precision pressure regulator, etc.), a vacuum generation section (vacuum generator, vacuum regulator), and a vacuum stabilization section (vacuum storage tank).
Convenient and flexible vacuum adjustment The vacuum generation section is a multi-set device that can be switched automatically with coating requirements. The vacuum storage tank is equipped with a (0~-5kPa) vacuum sensor and its (-0.01kPa) scale digital display, which allows the operator to understand the coating process and its process.
Advanced and reliable mechanical structure combined equipment The moving parts use linear guides to make the movements smooth and reliable. The rotary clamping device can not only automatically center the workpiece but also flip the workpiece 180* in the clamped state. The lifting device can not only Lifting and rotating the clamping device and the workpiece together can lift the sealing taper separately to achieve the sealing and vacuum of the workpiece.
The multifunctional vacuum storage tank vacuum energy storage tank not only has the main function of stabilizing the vacuum degree, but also holds a small amount of slurry extracted during rapid suction of the workpiece under the vacuum degree in the tank, thereby realizing the recovery and utilization of the expensive slurry.
Stir the homogenous liquid holding tank and the slurry in the impregnation dish until the precious metal particles are evenly dispersed in the suspension medium with high viscosity. The slurry remains in a liquid state without becoming fluid. Bad jelly status. The liquid tanks, dip tanks, and pipes and valves that are in contact with the slurry are all made of anti-corrosion materials.
4 The structure and operating procedure of the vacuum coating machine are as shown in the figure. The vacuum coating machine consists of a table 8, a workpiece shelf 6, a lateral movement device 3, a rotary clamping device 7, a lifting device 4 and a sealing taper sleeve 5, and operation. Taiwan 1, liquid tank 2, dip tank 9, vacuum generation system and vacuum tank 10, air control system and electronic control system and other components.
The procedure for the application of the vacuum coater to ceramic substrate workpieces is as follows: New method for thermowell protection sleeve closure Xue Fulian (Liaozhong Chemical Plant, Shenyang, Liaoning, Liaoning 110200) In the chemical refining production, the thermocouple thermometer was The most widely used temperature measurement instrument. The thermocouple's working end is susceptible to corrosion damage due to reducing gases, so a heat-resistant alloy protection sleeve must be used.
In the past, the thermowell's protective casing head was welded and closed into a spherical body, and the inner and outer surfaces of the casing were not smooth. Due to the inconsistent welding rod and casing material and poor welding, blisters and missing welds occurred. The casing is ablatively damaged in a short period of time. In general, in the high temperature range of 1200 or above, the average service life of the casing is only about 60 to 70 days. The damaged casing had to be shortened and used for degraded use.
One affects normal production operations, and the other causes great waste.
Recently, the instrument shop of our factory used ordinary C6140 lathes to process thermocouple protection bushings with a reinforced and closed (see) process method and achieved good results.
After the thermocouple protection sleeve is clamped on the lathe, it is axially aligned with the special tool 5 (the end of the thermocouple protection sleeve at the end of the workpiece is welded at a 87° angle with a ¥8,125-tungsten-cobalt alloy block of 311111181111110.5). In contrast, when the lathe rotates at a speed of 700r/min, the special tool simultaneously moves to the working end of the casing. After contact, the high-speed rotating casing and the cemented carbide frictionally generate heat, gradually plastically softening, and form a working end. The ball cone "turns over" as shown in (a).
Return the special tool and use the turning tool to cut the "overturned head" into a spherical surface.
Using this lathe-enhanced sealing process, 16 thermowells of different materials and specifications were processed. And at room temperature, they were each subjected to a pressure test with a pressure rise of 50 MPa, and no leakage of oil was found.
The method is simple and easy to process, requires only one-third of the required man-hours for the original welding process, and has smooth inner and outer surfaces of the casing after the car machining. The accuracy of the temperature measurement is high and the service life is long, which overcomes the blistering, missed welding, etc. caused by the welding process. Malady, greatly extending the use of time. Thermowells processed using this new process have now been put into production.
(Editing Huang Hao) 1- Operation platform 2 Liquid tank lateral movement device 4- Lifting and loading Drilling tool sets Shelves Rotary clamps Violet devices Workbench collapse Vacuum W tanks | Place workpieces on the workpiece rack 6 ,The two hands press the "start" button, the rotary clamping device 7 clamps the workpiece (the honeycomb base), the lifting device 4 lifts the rotary clamping device 7 together with the workpiece, and the lateral movement device 3 moves the workpiece to the left in place. . The sealing taper 5 descends and covers the upper part of the workpiece. The lifting device 4 descends. The lower end of the workpiece is immersed in the slurry for several millimeters. The upper end of the workpiece is subjected to vacuum degree I, and the lower half of the workpiece is coated. After the coating reaches half the height of the workpiece, the lifting device 4 rises and the vacuum degree is switched to the "vacuum level" and the workpiece is forcibly drawn; then the sealing taper 5 rises and the workpiece flips 180*; the sealing taper 5 descends over the workpiece, lifting The device 4 is lowered again, and the other end of the workpiece is immersed in a slurry, and the other half of the workpiece is coated under vacuum. When the required coating height is reached, the lifting device 4 is lifted, and the vacuum degree is switched to the “vacuum level†and the workpiece is forcibly pumped. After the suction is completed, the lateral movement device 3 moves rightward to return to the starting position, the sealing taper sleeve 5 is lifted into position, the lifting device 4 is lowered and the workpiece is placed on the workpiece rack 6, the rotary clamping device 7 is released, and the workpiece is manually removed. The entire coating process is over.
When coating different products, the clamping blocks and the corresponding sealing sleeves on the rotary clamping device 7 need to be replaced according to the corresponding specifications. 5. Concluding remarks The successful development of a new vacuum coating machine can greatly reduce vehicle exhaust emission devices. The manufacturing cost enables a well-performing, economical and practical vehicle exhaust emission device to be widely promoted and used in the market. (Edit Liming) Brief introduction of the release, male, senior engineer, mainly engaged in engineering and technical consulting work.
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