Gray cast iron flywheel and table plate lost mold process for high-speed punch press.


HT300 flywheel for high-speed punch, diameter 820, thickness 210, middle spoke 140, actual weight 620Kg. The casting blanks shall be fully processed, and there shall be no obvious casting defects after processing. Requires dynamic balance <50g.

HT300 table plate for high-speed punch press is a device for punch press tightening. 750 × 350 × 140, the actual weight is 415Kg, the casting blank needs to be fully processed, and the large plane is processed into a clamping groove with a depth of 20mm. These two castings are used for high-speed 65-ton punching machines with large stress load and continuous operation of punching. Shrinkage and porosity are not allowed inside, and the internal structure must be dense.

In addition, the customer proposed that the material and mechanical properties must be guaranteed, so the lower carbon equivalent should be selected, C should not be more than 3.0, Si should not be more than 1.7, so for this thick gray iron piece with large section, the shrinkage tendency of molten iron is large, the success or failure of feeding is the decisive factor for the density of the structure, in addition, the riser of cast iron is difficult to clean, so the contact area should be controlled. Otherwise, even if the replenishment is successfully cleaned up, it is a difficult problem. This time, the insulation riser and external cold iron are used to achieve complete replenishment. After dissecting the whole casting, the internal tissue is dense.

White mold assembly gating system

 

Complete the white mold to install the gating system, as shown in the figure

Both castings adopt a stepped system to ensure that the cooling of the castings is close to uniform, to avoid heat concentration, local sand overheating and slow cooling, resulting in long local solidification time, prone to shrinkage, riser feeding effect is poor.

When making models and runners, foam continuity must be considered. The foam continuity is poor, and there are gaps between the foam beads after cutting, resulting in coating penetration, and slag defects after processing. Apply repair cream to the parts with large gap of foam beads on the model, and the way of sticking newspaper can be considered for large areas. Due to the high flow rate of molten iron, the coating is seriously scoured. The runner must be treated by sticking newspaper or applying repair paste.

Flywheel gating system dimensions: Sprue: 1100×40×40. Runner 800×40×40. Ingate 15×50×60 (high)×2,

Dimensions of table tray gating system: Sprue: 1000×40×40, runner 300×40×40. Ingate: 15×50×60 (high)×4. Note: The height of the crossover cup of the sprue shall be flush with the riser.

Size of riser: The riser of gray iron is calculated according to 15%-20% of the actual weight of the casting. Diameter according to experience: D = 1.5 times the thickness of the hot section or the diameter of the inscribed circle. For the above two castings, the design of riser neck is particularly important, which involves the problem of feeding effect and later cleaning cost. The contact width of riser neck is 60 length and 300 length. The reducing height is 70. Note: The right-angle part of the reducing cutting part must be cut with a blade to make a fillet too much.

The pouring system adopts hot glue bonding. On the premise of using less glue as much as possible, the bonding must be firm and there must be no batch seams. To prevent slag inclusion caused by paint infiltration.

All the pouring system and the right angle of the model must be polished into a rounded corner, there is stress at the right angle, where the coating is not good, the coating is thin, and the strength is low. It is easy to crack here during the pouring process, and the tendency of box collapse is large.

yellow area

The pouring time of these two castings is long, and the inner wall of the coating of the gating system is seriously washed. The coating must ensure sufficient high temperature strength. To prevent the molten iron in the flow process inside the runner, part of the coating on the inner wall of the coating peeling off.

Coating permeability is also an important indicator of the normal casting and casting quality. The coating has good air permeability, the gas generated by the combustion of the foam can be discharged from the cavity in time, the pouring is smooth, and the flow resistance of the molten iron is small. The black smoke and oily substances produced by foam combustion will be adsorbed to the outside through the coating, and the surface quality is better.

To sum up, in order to improve the high temperature strength and air permeability, 3% silica sol is added to the coating, and 15% quartz powder is 100.

 

During the drying process, bumping should be avoided, and deformation should be considered when placing. The flywheel should be placed horizontally, and the table plate should be placed sideways or upright when it is longer. Brush three times, the coating thickness of 2mm.

Buried box

The two castings are simple in structure and shockable in layers. Special attention should be paid to the large and high grade gray iron with large shrinkage tendency. During the burying process, external cold iron should be placed in the upper part of the casting. Note that the cold iron must be dry, and the thickness of the cold iron is 2/3 of the wall thickness of the hot section. The cold iron must be placed after the sand is compacted.

 

When the sand reaches the root of the riser, place an iron ring, the diameter of the iron ring is 100mm larger than the diameter of the riser, fill the thermal insulation material in the middle of the coating and the riser, mix the thermal insulation material in advance, mix the mixing method with coal ash mixed with 5% sodium bentonite mixed with 15% sodium silicate, fill the iron ring, after tamping, blow dry the stroke strength with carbon dioxide.

Pouring

target composition

W(C):2.9-3.0% W(Si):1.6-1.7% W(Mn):0.9-1.0.

Blast temperature: 1480 ℃-1490 ℃, pouring temperature: 1420 ℃-1430 ℃

Using 75SiFe inoculation, iron slot inoculation 0.6, pouring with flow inoculation 0.1.

Flow shall not be cut off during pouring, and pouring shall be as fast as possible.

After the molten iron enters, immediately use the cutting gun to point through the riser and increase the exhaust channel.

After pouring, wait for 20s and add iron liquid at the riser. The riser shall be sprinkled with insulating agent and covered with aluminum silicate board.

 

The photo of turning over the box is shown in the figure.

 

SummaryThe success or failure of the lost foam casting process should be fully considered. Factors such as foam continuity and coating high temperature strength must be considered. Each link is interlocked. If there is any flaw in any link, there will be quality problems.

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