Because of some inherent shortcomings of sodium silicate sand, for example, the amount of sodium silicate added is high, which generally reaches 7%~8%, resulting in poor collapsibility of molding sand and difficult cleaning of castings after pouring; The second is sodium silicate sand. The old sand has low film removal rate, difficult regeneration of old sand, a large number of old sand emissions, and serious environmental pollution. These shortcomings have not been effectively improved or solved for a long time. With the introduction of resin sand after the 1970s, the application of sodium silicate sand has been greatly impacted, and the use share of sodium silicate sand has been continuously reduced.
| Project | Sodium silicate sand | Resin sand |
| Main components | Raw sand, water glass binder and hardener | Raw sand, synthetic resin binder, curing agent |
| Advantage | High fire resistance and good working conditions Low cost, fast hardening speed The production site is non-toxic and tasteless | The surface quality of castings is good High dimensional accuracy of mold The collapsibility and regeneration performance of old sand are good |
| Disadvantage | Poor collapsibility of old sand The regeneration and reuse performance of old sand is poor It is relatively difficult to clean the falling sand | The odor pollution of resin sand is serious High cost |
| Scope of application | Thin wall castings with low added value and high crack tendency, pump and valve castings | Castings with high added value, Castings with low crack tendency |
Since the 1990s, due to the prohibition of water blasting sand cleaning process in some industries, in order to solve the problem of sand falling and cleaning of steel castings, inspired by the success of furan resin sand technology in iron castings, some factories have tried to use furan resin sand technology in the production of steel castings, but the results are not satisfactory. After the production of steel castings from sodium silicate sand to furan resin sand, due to some inherent characteristics of furan resin sand, such as poor high-temperature concession, high cost, and obvious increase of crack defects of steel castings, although the crack defects have been reduced after taking some technological measures, they are difficult to completely eliminate, and sometimes good or bad, very unstable, which is more than the problems encountered when using sodium silicate sand. Many years later, many factories have adopted sodium silicate sand technology again. However, in European and American countries, there are many reports on the production of steel castings with alkaline phenolic resin sand. Compared with acid hardened furan resin sand, the crack defects of steel castings produced with alkaline phenolic resin sand tend to be greatly reduced, but the amount of resin added is greatly increased, the cost of castings is increased, and the recycling performance of alkaline phenolic resin used sand is reduced.
In recent years, there have been different views on which molding sand is better for steel castings in China’s business and academic circles. The two processes have their own characteristics in performance, and there are also some problems.