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Loss modulus and negative pressure casting wheel castings feeding system design

Update time:2015-02-03 17:28:09Hit:4658
Design in many literatures vanish mould negative pressure cast steel feeding system, is from the cavity casting evolved, less detailed narration, mostly with a pen. Although the two have similarities, on the former previous theories are not applicable. How to correctly design EPC negative casting steel parts feeding system?
A vertical casting, casting products, take unified feeding system design:
The structure has three parts: the wheel rim, the spokes and the wheel hub.
General sand casting is flat, placed risers and chills in the rim and hub. But disappear process mode negative differs from cast iron and nonferrous metal. Wheel type feeding system of gating and Risering principle is: unified process. The riser on the rims of the circular arc surface, and with round light heat insulating riser, modeling stand, from the top riser gating only, after pouring riser weight with no less than 15% heating agent covered riser, added in 2 times, and pouring the riser 1-3. In the shaft hole at the hub in the filled resin chromite rims or iron sand, if the hot section is relatively large, can be placed in the cold iron, if the hub hot section of more than 200mm mandatory cooling, in order to achieve the purpose of solidification and spoke at the same time. After pouring hot day according to size, vacuum keep 10 - more than 20 minutes.
Two, vertical pouring, pouring take goods uniform feeding system design the following advantages:
1 the disappearance of dry sand mold cavity mode, low thermal conductivity, is not conducive to the formation of dense crystalline structure of steel castings. Place the cold iron in the lower half of the rim, while reducing the riser, the process yield can be increased by 80 - 85%, grain refinement of the initial crystallization, optimize the quality of the casting.
2 open fast counter, in the non occurrence of reverse jet case, the sooner the better. The burning wreckage floating on the liquid steel surface with circular arc was pushed riser, no stagnant dead angle, reduce slag defect rim and hub parts.
Inhalation of 3 pouring air, make the most of EPS combustion, free carbon generated CO.CO2 and a little, then with high temperature gas discharge cavity, reducing the probability of increasing carbon steel castings, two oxidation type reducing gas cavity prevents the liquid steel and occurs as a result of pouring splash.
4.EPS combustion release a lot of heat, slows down the steel liquid temperature drop. The pouring temperature and the actual sand process is almost the same, avoids negative pressure casting defects caused by the increase of pouring temperature.
Three, feeding the matters needing attention in the implementation of the system:
1 appearance with EPS do not put any flame retardant additive.
Double wheel this process applies.
2 to two times more effectively prevent the oxidation of molten steel, molten liquid steel during the implementation of refining, purification, combined deoxidation measures. The adding amount of deoxidizing agent is increased by 0.05%, which should contain: RE, Al, Ca, Ba, and other elements.
3.EPS solutions produced 10 times as large specific heat of combustion gas, to prevent the reverse jet, breathable coating should be in 40%-60%, there is also a 60%-40% gas escaping from the riser.
How to make the coating to achieve this performance? Wheel size, thermal Festival is big, high temperature erosion coating and at the same time, impact resistance and long time. Derived from the practice of hot section: rim below 100 mm, about 200 items of the aggregate with paint, paint in about 2 mm. Hot section in the 100 - 200 meters, with 180 - 200 head, 120 - 160 orders two kinds of aggregate mix, coating between 2 - 6 mm. Hot day in more than 200 mm, or weight more than 1500 kg, with a 180 - 200 head, 120 - 160 head, 60 - 100 orders three kinds of aggregate with coating in 6 millimeter above. Modeling of dry sand with chrome ore or nfs.
4 more than 1000 millimeters in diameter wheel, set up another ladder shaped pouring system, the ingate and the work vertically, shall not open in the hub. On the root of the riser a ingate from the workpiece at 50 mm. The gating system must be hard binding and casting.
5 the process of coating thick, formulated coating permeability, using aluminum oxide powder, quartz powder with each size aggregate. In the paint to use air permeability, organic matter that less is more. Most theoretical tendency: organic compounds in the coating can increase the high temperature permeability. Coating but is only applicable to 2 mm below the. Coating thickening, in the fast gating, organic matter in the coating did not come and decomposition of liquid steel, has filled the cavity. If the organic matter too much, in the high temperature, high pressure and the formation of a large number of micro vacuum under the action of liquid steel, with micropores were out of cavity formation, and difficult to remove the iron ladle sand.
Four, other technology measure
Such as mass production, the following two methods can also obtain satisfactory castings.
The 1 increase in organic coatings in improving the amount of coating dry strength, first boil after casting, coating in 4 millimeter above.
2 silica gel coating, coated 3-4 times, besmear again put a layer of dry sand, coating should be greater than 20 mm, at 950 degrees Celsius after calcination, submerged shell of vacuum casting.
(Author:dong)
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