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In recent years, some small and medium-sized enterprises have urgently needed the resin sand process in order to improve the quality of steel castings. However, due to their limited economic capacity, they are unable to purchase resin sand recycling equipment, and the old sand cannot be recycled and reused, resulting in high production costs. In order to find an effective way to improve the quality of castings but not excessively increase the cost, we can combine the process characteristics of CO2 blow-hardening water glass sand and CO2 blow-hardening basic phenolic resin sand, using CO2 blow-hardening water glass-alkaline phenolic Resin sand composite process, using basic phenolic resin sand as surface sand, using water glass sand as back sand, while blowing CO2 hardening. The phenolic resin used for CO2-basic phenolic resin sand is made by polycondensation of phenol and formaldehyde under the action of a strong alkaline catalyst and adding a coupling agent. Its PH value ≥13, viscosity ≤500mPa•s. The amount of phenolic resin added in the sand is 3%~4% (mass fraction).

When the CO2 flow rate is 0.8~1.0m3/h, the best blowing time is 30~60s; if the blowing time is too short, the hardening strength of the sand core is low; if the blowing time is too long, the strength of the sand core does not increase, and it is wasted gas. CO2-alkaline phenolic resin sand does not contain harmful elements such as N, P, S, etc. Therefore, casting defects such as pores and micro-cracks on the surface caused by these elements are eliminated; harmful gases such as H2S and SO2 are not released during pouring, which is beneficial to environmental protection ; Good collapsibility, easy to clean; high dimensional accuracy; high production efficiency. The CO2 blowing hardening water glass-alkaline phenolic resin sand composite process can be widely used in steel castings, iron castings, copper alloys and light alloy castings. The composite process is a convenient process. The process is as follows: firstly mix resin sand and water glass sand separately, and then put them into two sand hoppers; then add the mixed resin sand as surface sand to the sand box And solidify, the thickness of the surface sand layer is generally 30~50mm; then add water glass sand as the brass gear Suppliers back sand to fill and compact; finally blow CO2 gas into the mold to harden.

The diameter of the blowpipe is generally 25mm, and the hardenable range is about 6 times the diameter of the blowpipe. The blowing time depends on the size and shape of the sand mold (core), gas flow, and the size of the exhaust plug area. Generally, the blowing time is controlled at 15~40s. The mold can be taken after blowing the hard sand mold (core). The strength of the sand mold (core) rises fast. Brush the paint within half an hour after taking the mold, and it can be poured into the box after 4 hours. The composite process is particularly suitable for steel casting plants that have no resin sand recycling equipment and need to produce high-quality castings. The process is easy to operate and easy to control. The quality of the castings produced is the same as that of other resin sands. CO2 blow-hardened sodium silicate sand can also be combined with CO2 blow-hardened sodium polyacrylate resin sand for the production of high-quality castings.


# by nxsahuw | 2020-06-09 14:57