Casting method of nodular cast iron piston ring blank

1. Casting method of single nodular cast iron piston ring blank

Single piece casting method is generally used in minicars with small cylinder diameter, especially motorcycle piston ring. The diameter of the ring is Φ Below 65mm, in order to prevent the shrinkage and looseness of the center, in the formwork design, three to four short risers shall be placed in the inner circle of the elliptical ring mold to collect the cold iron water, which can reduce or eliminate the shrinkage and looseness of the center. “The molding is to use 2145 top box shock molding machine, or three station semi-automatic high-pressure molding machine for stacking pouring.

2. Casting method of double piece nodular cast iron piston ring

The nodular cast iron piston ring die is designed into elliptical double pieces, the concave positioning mark is designed in the inner circle of the opening, and the 2145 molding machine or three station semi-automatic high-pressure molding machine is used for molding and box stacking pouring. This is the most commonly used casting method at present. German gerz company has applied this technology since the 1970s, Since the mid-1980s, domestic piston ring manufacturers have basically adopted double piece casting technology to produce double piece nodular cast iron piston rings in large quantities.

The introduction of foreign advanced double piece casting technology and the digestion and absorption of production enterprises have accumulated a lot of practical experience in production and technological innovation, which has greatly improved the technical level and product quality of nodular cast iron piston rings in the domestic piston ring industry.

The nodular cast iron piston rings of RIKEN, NPR and imperial piston rings (strain) in Japan are also mainly produced by double piece elliptical casting, which also reflects that the double piece elliptical casting process is the most mature process at present. The outstanding advantage of this process is that the machining allowance of the inner and outer circles and end faces is small. The shrinkage of the center produced by the double blank is cut off during slicing to obtain a single blank without shrinkage defects. The elliptical blank directly carries out the profiling of the inner and outer circles. The pressure curve distribution of the ring is reasonable, and the thermal stability and use reliability are high, This is a method that is being popularized and applied at home and abroad.

3. Casting method of cylinder nodular cast iron piston ring

(1) Manual molding method of sand mold cylinder

Under the condition of no machine modeling, the cylinder nodular cast iron piston ring is produced by manual sand casting, which is only suitable for the production of small varieties and small batches. Manual molding has low production efficiency, high casting scrap rate and poor casting accuracy. At present, there are few factories using this casting method.

(2) centrifugal cylinder casting method

Centrifugal casting machine is used to produce centrifugal cylinder nodular cast iron piston ring casting, which is the same as the process of producing alloy cast iron centrifugal cylinder liner, which is also a mass production method. The casting has a large machining allowance for the inner and outer circles. The machining allowance for the inner and outer circles is about 5mm respectively, and part of the two ends need to be cut off respectively. Therefore, the slicing efficiency is low.

(3) Automatic production line of sand mold cylinder

The sm-50v, sm-60v of Japan Guangyang machinery (strain) or the automatic molding production line of Desa company are used to produce cylinder nodular cast iron piston rings. This is an efficient box free vertical parting molding method. The sand mold thickness is adjustable, the thinnest thickness is 100mm, and the productivity is very high. 500 boxes can be molded per hour, and there are 10-30 castings per box.

Such casting production lines are available in RIKEN, NPR and the metallurgical branch of gaz automobile factory in Russia, and the production cylinder diameter is Φ 70- Φ 110 between the short cylinder ductile iron piston ring, suitable for less varieties! The production mode with large production volume, of course, requires a lot of efficient special slicing machines to match this production line.

(4) Casting method of lost foam casting cylinder nodular cast iron piston ring

Lost foam casting method is only suitable for minicars with small cylinder diameter and nodular cast iron piston rings of motorcycles. The application of special production line for lost foam casting molding has high production efficiency. Especially, the sand treatment system is simple and the investment is less. The disadvantage of this process is that the casting has shrinkage and looseness in the center. Considering the machining allowance, machining efficiency and cost, it is not easy to eliminate this defect.

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