Construction machinery casting process characteristics


Release time:

2022-06-27

The mass production, type and structure of construction machinery castings are complex, and the strength of core sand is required. Furan resin self-hardening sand technology is mature, equipment serialization, standardization, raw and auxiliary materials market is broad, binder resin addition amount is less than 1.0, low cost, old sand regeneration is good, recovery rate is 90%, therefore, construction machinery castings should consider manufacturability, cost control, environmental, furan resin self-inclined is a good choice for modeling materials. With furan resin sand production of castings, point shooting, perforation, subcutaneous pores and other defects are significantly reduced, especially complex selfishness, no heart bone, can be modeled, core operation, productivity greatly improved.

First of all, the selection of engineering machinery casting materials

工程机械铸件

The mass production, type and structure of construction machinery castings are complex, and the strength of core sand is required. Furan resin self-hardening sand technology is mature, equipment serialization, standardization, raw and auxiliary materials market is broad, binder resin addition amount is less than 1.0, low cost, old sand regeneration is good, recovery rate is 90%, therefore, construction machinery castings should consider manufacturability, cost control, environmental, furan resin self-inclined is a good choice for modeling materials. With furan resin sand production of castings, point shooting, perforation, subcutaneous pores and other defects are significantly reduced, especially complex selfishness, no heart bone, can be modeled, core operation, productivity greatly improved.

Process Characteristics of Different Types of 2. Construction Machinery Castings

Box casting

The wall thickness of the casting is generally about 10mm, which belongs to the "thin skin and large cattle" casting. The sand-iron ratio is high, and it is easy to produce pores and cold strike defects. Therefore, in the process design of these castings, the principle of "top injection" is given priority. Open pouring system is adopted, inclined pouring, overflow inlet is set on the opposite side of the gate for exhaust, and cold molten iron is collected. The core head is designed as much as possible at the top plane inlet to ensure that the gas in the sand core is discharged from the top core. Make full use of the through hole as the support point of the sand core, greatly reduce the use of core support, reduce the cold barrier defects.

Flywheel casting

The diameter of the flywheel castings is about 500mm, and the wall thickness is about 40mm. These castings are thick solid castings. The castings are prone to shrinkage and shrinkage defects, so the focus of the process is to supplement.

The caulking method is to use riser caulking, using hot riser or edge riser, square riser, "flat, thin, wide" inclined pipe, but for pressure edge riser, the pressure edge width cannot be too small. According to the author's experience, 12~16mm is appropriate, can effectively supplement. Secondly, by adding cold iron, make full use of graphite expansion for self-contraction. These two measures are combined to control the quality of thick flow castings. However, to determine the number of cold iron use, to prevent the cold iron surface oxidation caused by the decline in cold capacity and choking phenomenon. In general, cold iron surface oxidation layer and graphitization layer reached 0.2~0.4mm, cold iron should stop using. The recommended number of uses is 15.

Cylinder block casting

Cylinder castings also belong to ring castings, but due to the presence of induction and ring removal, castings are prone to porosity and shrinkage defects, and the process is more difficult. In the process design, the exhaust of the oil core should be fully considered, the nylon diagram should be added to the oil core, and the core head should be increased. In addition, the number of main channels is set in accordance with the size of the casting diameter in consideration of the shrinkage range of the main channel. Castings made of HT250 do not require cold iron, but for ink cast iron, cold iron needs to be added to the bottom of the cylinder to prevent shrinkage defects. Transmission body casting

The typical characteristics of this kind of engineering machinery castings are large aspect ratio, small wall thickness, and the principle of "top priority" is still adopted in process design, which is convenient for the smooth discharge of the fuselage from the mold and sand core. For gray cast iron boxes, the self-shrinkage ability of the castings is very strong. Regardless of the patching riser, the ductile iron box is generally equipped with a top riser on the top surface, which can effectively shrink in the lower part of the casting. The casting process parameters need to adjust the amount of shrinkage in different directions. Normal length, width direction is 1%, height direction is 0.5. In order to overcome the difficulties of high casting and difficult molding, when molding, the molding slope is positive and negative, and the core box slope is consistent with the outer skin to ensure uniform wall thickness. The casting has a fast cooling speed, and the sand core hinders shrinkage and is prone to cracks. Therefore, the sand core should be provided with materials to improve the concession, or a hollow wick should be manufactured. It can also delay the time of hitting the box to prevent the casting from cracking.