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Analysis of Casting Production Technology of Pump Body Castings

Issuing time:2021-01-15 09:55Author:momo

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The dredging pump is a professional pump in the dredging industry. The material of the flow parts is mainly wear-resistant steel and wear-resistant white cast iron. The pump casing is the main part of the dredging pump and the largest wear-resistant material casting.There are certain difficulties in casting production, and defects such as shrinkage cavity, shrinkage porosity, pores and cracks are prone to occur. This article analyzes the technological characteristics of this type of castings,adopts a series of technological measures, and has received good results.

Structural characteristics of castings

Dredger pump body castings are thick-walled castings with outline dimensions above 2000mm ×2000mm, total height 600~1000mm, and wall thickness 60~120mrn. The material used is mostly wear-resistant white cast iron to adapt to the greater wear of industrial and mining media.

Casting process analysis

The body shrinkage and linear shrinkage of wear-resistant white cast iron are both large, and the principle is to adopt a casting process similar to that of cast steel. At the same time, combined with the characteristics of thicker castings,in order to improve the feeding effect, the top riser feeding is generally preferred, and the runners are appropriately enlarged.

A. Opening of the pouring system

The pouring system is made of sprue cups, flow steel bricks, four-hole hexagonal bricks and formed ceramic pipes. The double pouring system is adopted, and the upper and lower layers are symmetrically separated from each pair of upper and lower mouth rings. The sprue cup is made of Φ270/Φ90mm ceramics, the sprue is a series of flow steel bricks of different diameters, and the inner runner adopts a series of formed ceramic sprues of different diameters.

B. Riser settings

According to the established feeding principle, combined with the volute shape of the pump body, a mixing process is adopted that uses side risers at small sections and top risers for other parts. The side riser should be increased to the same height as the top riser. The size of the riser is determined by the modulus method combined with the proportional method.

C. Arrangement of cold iron

Place a circle of cold iron on the bottom surface of the lower box, usually in a manner of separating multiple pieces. The partition tongue (the junction between the water outlet and the main body) is a typical hot spot of this type of casting,and it is not easy to feed it with a riser. Generally, sand-coated conformal cold iron is used for chilling to reduce shrinkage defects.

The remaining process parameters can be selected according to the manual.

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Typical casting process

Production process measures and implementation

A. Paint and brushing

For general pump body sand mold (core), alcohol-based zircon powder coating for steel castings is used. The sand mold (core) of the large dredging pump body adopts alcohol-based zircon powder or water-based zircon powder coating for steel castings.

B. Handling of casting marks

In order to ensure the clear and beautiful markings of the characters, it is better to use zirconium sand to cover the characters, or to use professionally manufactureds and cores. After styling, use a less dense paint to paint to prevent "dust accumulation" in dead corners.

C. Exhaust measures

a. Tie a straw rope on the core iron to form an airway-no less than 6 strands of straw rope-and come out from the core. Use a Φ60mm hole outside the core to lead out the air.

b. Use Φ60mm holes to form 2~3 air passages at the center core of the sand mold upper box.

D. Other related measures

a. When making the core, put several straw ropes in the core to enhance the exhaust and core retreat.

b. The neck of the riser is made of refined quartz sand or special sand with high refractoriness.

c. The lifting hole core of the pump body is made of zircon sand.

E. Melting and pouring

a. Before being out of the furnace, add 0.6%Al+0.2%CaSi to degas in the molten iron ladle. Use iron slag mixing method to tap iron.

b. The refractory lining of the ladle must be fully dried and baked to dark red orred. The plugs and seat bricks used for the ladle should be carefully selected,and the formed bricks with compact contact surface and uniform clay quality should be selected to prevent the ladle hole from opening during pouring.

c. The temperature of the furnace is 1450~1480, and the pouring temperature is1400~1430. It can be adjusted appropriately according to the specific structure of the casting.

d. After the molten iron comes out of the furnace, let it stand in the ladle for a while before pouring.

F. Casting pressure box

The pressing time depends on the conditions of the castings to ensure that the casting sand falling temperature is within 200.

G. Cleaning procedure: sand falling. Riser removal, batch seam removal, heat treatment,grinding and repairing, grinding, painting, and storage.

H. The heat treatment adopts quenching + tempering treatment.

Conclusion

Such castings include the pump body of the single pump casing of the dredging pump, the sheath of the double pump casing (also called the inner liner, the bladder guard, and the inner shell), etc., which account for a large proportion of the dredging pump castings and solve the technological problems. After mass production,better economic benefits can be obtained. We started with the analysis of its structural characteristics and material process performance, and proposed a mature casting process and field process measures. The castings produced have a smooth surface and good internal quality. They have been successfully applied to dredgers in major domestic waterway bureaus, providing a powerful technological guarantee for enterprises to occupy the dredging market.



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