The curing rate of resin self hardening sand increases with the increase of ambient temperature (including raw sand temperature). When other conditions remain unchanged, the curing rate should be doubled for every 10 ℃ increase in sand temperature; For resin sand with the same curing agent content, the molding time will be shortened by 1 / 3 ~ 1 / 4 when the sand temperature increases by 5 ℃. When the relative humidity of the environment (including the humidity of raw sand) increases, the hardening speed of resin self hardening sand slows down, and the final strength usually decreases; When the ambient humidity is high, the water evaporation is blocked and the hardening speed is slowed down. In the modeling of, the generation of casting pores is greatly reduced by solving the influence of ambient temperature and humidity on curing speed. The main methods are as follows.
(1) When the ambient temperature increases or decreases by 10 ℃, the curing agent shall decrease or increase by 0.5% ~ 1.0% (mass fraction). If the relative humidity increases at the same time, the curing agent shall increase slightly. Generally, the interval can be adjusted according to the change of ambient temperature by 5 ℃ to eliminate casting pores.
(2) When the ambient temperature is above 10 ℃, only the amount of curing agent needs to be adjusted; When the ambient temperature is below 10 ℃, low temperature curing agent is used to eliminate casting pores.
(3) Under the condition of low temperature, by adjusting the sand temperature, increasing the temperature of resin and curing agent, combined with the use of high concentration and high activation curing agent, the purpose of eliminating casting porosity can be achieved.
(4) Increase the air permeability of the sand mold and pierce air holes above the sand mold; Making the sand core hollow can not only increase the gas emission, but also get good concession, so as to eliminate the casting pores.