Still remaining in the viscose, the viscose fiber is strongly reduced.
In addition, the metal elements such as manganese, cobalt, and iron in the pulp ash promote the aging of alkali fibers, affecting the aging time, and the calcium salts have a serious negative effect on the filtration performance, thus affecting the quality of the fibers and also directly Affects the stability of process parameters. The improvement of pulp quality will inevitably reduce its inherent inorganic and organic impurities.
Raising the purity of pulp can be achieved by strengthening mechanical and chemical impurity removal methods. Specific methods: 1 Strictly control the quality of good lint and various raw materials; 2 Ensure the quality of water; 3 Improve the alkali rate for cooking and improve the washing materials. Quality; 4 strengthen pickling, especially pre-acid treatment.
3. Pay attention to the quality of beating and improve the performance of alkali absorption Beating is another key process to control the alkali absorption performance of pulp. In order to achieve the best reaction performance of different pulps, in addition to various factors of chemical refining in the pulping process, the alkali absorption value and swelling index that reflect the alkali absorption performance of the pulp are used to filter the performance and spinnability of the viscose. There are also non-negligible effects. Only those pulps with good alkali absorption ability can undergo vigorous expansion under the action of the alkaline solution. The fibers become coarse, the internal surface area increases, and the number of active hydroxyl groups increases, making it easier for cellulose to interact with various chemicals. The obtained alkali fiber is more uniform and can also have higher reaction performance in the acidification. If the alkali absorption performance is not good, although chemical reactions can also occur, it is difficult, and the alkali fibers are not uniform, and the viscose filtration performance and spinnability of the resulting viscose are relatively poor.
The beating process can fully destroy the primary wall that is not completely destroyed during the cooking process. This mechanical action only increases the surface activity of the fibers without chemical reactions. Different lint, should use different beating methods. For the cooking method with poor cooking effect, hard-feeling material and type I and n types of velvet, it is better to use lower beating concentration, to keep abreast with the knife, to shorten the beating time, and to slow down the rate of increase in the degree of mitigation; And the method of beating the ideal material for cooking is to appropriately increase the beating concentration so that the beating is carried out in a slow and abundant time, and the degree of dehydration is appropriately increased to avoid excessive fiber cut-off.
In order to improve the alkali absorption performance of the pulp, the influence of the papermaking process cannot be ignored. Increasing the dewatering effect of the paper making machine can cause the cellulose to form a natural interweaving state during molding, and more small fibers can be easily removed from the fiber layer, which is beneficial to improvement. Pulp alkali absorption properties. To reduce the surface temperature of the dryer as much as possible, increase the pressure of the positive and main pressure, and increase the alkali absorption and swelling ability of the pulp.
To improve the quality of pulp, in addition to the above, the process parameters of each process should be comprehensively balanced in production.
Influence of Atmospheric Pressure on Viscosity Measurement of Viscose Deaeration Cui Dawei (Dandong Chemical Fiber Co., Ltd., Liaoning 118002) Deaeration is a link in the process of making glue in viscose fiber production with the aim of minimizing spun-bonding. The content of air bubbles in the glue, thereby reducing the production of wool in the viscose fiber. The quality of the defoaming quality is directly related to spinning spinnability, cheese strikeability, and thus product quality level.
In actual production, viscose uses either static deaeration or continuous deaeration. In addition to deaeration time, the degree of vacuum when vacuum is used is also an important measure of defoaming quality. The measurement method usually uses a vacuum gauge or U-type manometer direct measurement. When the vacuum degree indicated in the table is lower than the reading required by the process, the method of vacuum leak detection is generally adopted to solve the problem. This method sometimes works and sometimes it does not work. The degree of vacuum measured now is based on the relative value of the external atmospheric pressure constant or when the change is not significant. A non-true vacuum degree is negative pressure. The atmospheric pressure around us is changing at any time. For this purpose, I did a comparison measurement of atmospheric pressure (using an empty box-type barometer and a U-shaped mercury manometer). Take the example of Dandong District at 7:00 am everyday, indoor and outdoor. The highest pressure value. At the time (January 8, 1997) reached 104hpa, equivalent to 781mmHg column, the lowest value (June 9th) only 998hpa, equivalent to 748mmHg column, a difference of 33mmHg column; and the pressure value of the day is not the same, such as September 1997, September 17th: The early seven o'clock pressure is l13hpa, 1 o'clock noon is 1004hPa, the late seven o'clock is lOOlhpa, sooner or later the difference is 12hpa, namely 9mmHg column. The following shows the atmospheric pressure and U-type vacuum gauge display graphs (Figure 1) from August 15 to September 29, 1997.
It can be seen from Figure 1 that the two curves have very close variation, and the difference between the two is plotted in Figure 2, which is basically a constant straight line, and this value is the true vacuum-negative pressure. The representative is what we need to control in our actual production. The smaller the negative pressure, the closer the vacuum is to the atmospheric pressure, the better the defoaming effect. Therefore, we believe that the measurement of vacuum in actual production should introduce atmospheric pressure as a reference, and use the difference as a basis for measuring the effectiveness of defoaming.
After more than one year of practical application, when the difference deviates from the straight line, we find out the problems of the X equipment or the phenomenon of pipeline leakage. It is not surprising that we see “strange†when reading the vacuum gauge beyond 760 mmHg.
In the viscose defoaming process, in addition to adjusting the defoaming time based on the true value of the vacuum degree, the following points must also be taken into account in order to improve the quality of defoaming: Pay attention to ensure the tightness of the vacuum system, including piping, valves, and equipment And so on, only the seal is good enough to realize the true performance of vacuum equipment.
The use of more efficient vacuum equipment, the current domestic vacuum equipment, such as effective vacuum pump can increase the vacuum degree above the lOmraHg column. Its disadvantages are large energy consumption and high cost.
When the water ring vacuum pump and the water jet pump are used, the temperature of the medium water should also be as low as possible, because when the vacuum pump reaches a certain equilibrium, the direct factor affecting the vacuum (or negative pressure) is its saturation. Steam pressure, and its value is directly related to water temperature.
Now every country optimistic about the prospect of the magnesium alloy die castings,especially in auto,aviation,telecom,transportation and mechanical industry,
which adopt to use magnesium alloy die casting to replace steel casting for reducing weight effectively and then can save energy and reduce environment pollution. The car can decrease 0.4L oil consumption per kilometer if it can relieve every 100KGS. So America,Japan and European countries have enlarge use of magnesium alloy Die Casting Parts, for example, steering wheel, instrument panel, seat skeleton, crankcase, gearbox shell, wheel hub and so on. So magnesium alloy die castings grows at 20%~30% a year, 80% of them are die casting parts. Meanwhile magnesium alloy die castings expand use in appliance light industry and daily hardware, such as notebook shell, VCR box, mobile phone, power tool shell,camera shell, upholstery, mower shell etc. These magnesium alloy die casting parts with a series of advantages, not only greatly reduce weight, but also have the precise & steady dimension and smooth finish surface.
Die-cast magnesium alloy material:
Magnesium and aluminum have big differences in the chemical, physical properties, mainly in terms of chemical reactivity, surface oxidation of the liquid metal
material tightness, thermal effects during solidification, resistant to electricity chemical corrosion resistance capabilities.
Magnesium has a strong chemical reactivity than aluminum and the metal bath surface can not be formed as dense as molten aluminum alloy oxide protective film
to prevent oxidation reaction to proceed, so magnesium alloy flammable or explosive. Magnesium alloy is also easy to dissolve other metals, including magnesium
alloy severely reduce the ability of anti-electrochemical corrosion of nickel, copper and other elements. In addition, the same volume of liquid aluminum and magnesium alloy during solidification.
Magnesium alloy heat release was significantly lower than aluminum.
Magnesium alloy chemical elements:
Mechanical properties of pure magnesium is very poor, can not meet the requirements of industrial parts of the yield strength and tensile strength. By adding alloying elements can significantly improve the mechanical properties of magnesium, the magnesium alloy`s strength to weight than the titanium alloy in all kinds of alloying and ranked second, open up broad prospects for its application.
The effect of alloying element second is to improve the performance of magnesium alloy casting. Pure magnesium have high melting point, poor mobility, high shrinkage.
By alloying can reduce the temperature of the liquid, increase liquidity. According to the characteristics of magnesium alloy decreased significantly at temperature above 150degrees Celsius and the strength of the alloy,
the third role is to enhance the creep resistance of magnesium alloy.
Magnesium alloy commonly used alloying elements are aluminum and zinc. Alloying of aluminum alloy can improve the strength and casting properties. Zinc can also improve the performance of the alloy casting. In order to ensure the casting performance, the aluminum content should be more than 3% in the die casting magnesium alloy, zinc content is less than 2%. Otherwise it is easy to produce crack.
The commonly used magnesium alloy die-casting material
Common cold chamber die casting machine injection parts must be improved to meet the needs of the magnesium alloy die casting production as follows:
1) Fast injection speed increased from 4~5m/s to 6~10m/s.
2) Reduce the time of supercharging and build pressure.
3) Improve the injection speed and injection force control.
4) Equipped with a special furnace protection gas device
The aluminum die casting part production flow chart
Commonly used materials of magnesium alloy die casting: ADC12, ZL101, ZL102,A380, AlSi9Cu3, AlSi12(Fe);
The precision of the magnesium die casting: ±0.1mm;
Smoothness of surface of rough part: Ra1.6~Ra3.2;
Shrinkage rate of Mg alloy die casting products: 0.5%;
Material wastage rate: 5%;
General magnesium die-casting machining allowance: 0.5mm~0.7mm;
Surface preparation methods: Sand blasted, Shot blasting, Powder coating, Painting, Plating, Electrophoresis, Polishing
Our company's magnesium alloy die casting production equipment and management system
Aluminum Die casting production equipment: L.K brand die casting machine From 160T, 200T, 280T, 400T, 630T, 800T and 1250T;
CNC machining center: 8 sets;
CNC lathe machine: 6 Guangzhou Machines and 7 Shenyang Machines;
Work days of one week: From Monday to Saturday;
Shift work: 2 shift per day;
Working hours: From AM 8:00 to PM 5:00;
2D and 3D drawing Software: AutoCAD, UG, Pro/E, SolidWorks 2013;
QC control: New type NANO CMM, FPI M5000 desktop metal analyzer, Easson projector, Mechanical properties tester.
The production of Magnesium die casting and QC control
Magnesium Die Casting Part, Magnesium Alloy Die Casting Part, Magnesium Die-Casting Product, Magnesium Injection Part
NINGBO BEILUN LEMA MACHINERY TECHNOLOGY CO.,LTD , http://www.china-lema.com