Promoting Green Casting is the Development Trend of Valve Casting Industry in the Future

At present, people have very high quality requirements for precision valve steel castings, so during the process , valve manufacturers also pay great attention to the selection of process methods and production processes, so as to ensure that the production of steel castings can reach higher application standards. First of all, we should be more cautious when choosing raw materials. Although many steel castings do not have much difference in appearance, due to the different selection of raw materials, there will be differences in quality and service life of steel castings in the process of using, so the selection method of raw materials needs special attention.

Making a correct and reasonable production process is the key to reduce the cost of resin sand casting valve. Whether it is reasonable or not directly affects the yield, quality and cost of castings.

1. Determining the LOI value of suitable reclaimed sand, i.e. burning reduction, is an important index to measure the defilm rate of reclaimed sand. It is also closely related to the amount of gas generated by sand and the porosity defects produced by castings. Castings are generally produced with furan resin sand. Practice has proved that the LOI value controlled at about 3% can fully meet the production requirements. However, some enterprises require that the LOI value be controlled below 2.5%. To achieve this goal, we need to increase equipment, or increase the number of sand reclamation, or add more new sand. This will undoubtedly increase equipment investment, reclamation cost and raw material cost.

2. Determining appropriate casting process parameters

(1) To determine the appropriate final strength, generally, after the resin sand is mixed and self-hardened for about 24 hours, the high strength, i.e. the final strength, can be achieved. Because of the different production conditions and scale of each enterprise, the time interval between moulding and pouring does not necessarily exceed 24 hours, so the final strength should be determined according to the enterprise. Small-scale enterprises with one stove in a few days may adopt the 24-hour final strength standard; enterprises with solidification time of casting less than 24 hours shall take the strength reached before pouring as the final strength standard. At the same time, there are two tendencies to be overcome in production: on the one hand, blindly increasing the strength to ensure the quality, increasing the casting cost and causing waste; on the other hand, pressing down the strength to ensure the cost, resulting in unstable quality and large fluctuation range, so that the quality of castings is greatly affected by raw materials and operators. Each enterprise should determine the appropriate final strength according to its own situation, so as to save resin and curing agent and reduce casting cost on the premise of guaranteeing casting quality.

(2) Determining the yield of castings with appropriate moulding technology directly affects the casting cost. The appropriate moulding technology can not only ensure the quality of castings, but also reduce the casting cost, and reduce the rejection rate of castings is one of the direct measures to reduce the casting cost. When determining the moulding technology, we should make special sand box and box wall with more air holes, make solid model and use template moulding, use ceramic pipe and inner gate in the pouring system with more and more dispersed, paint painting is uniform, no leakage, and more air outlets are set up to ensure the smooth exhaust of core.

With the increasing enforcement of environmental protection law in valve foundry industry in China in recent years, some small valve foundries have been forced to attach importance to environmental protection technology. It is evident that some far-sighted valve entrepreneurs have taken the initiative to invest heavily in cleaner production technology and development of “green” foundry products, and to implement international enterprise standards. Improving casting quality and promoting green casting are the development trend of valve casting industry in the future.

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