Hardener of Sodium Silicate-Magnesium Chloride

Keywords:

binder

Source: internal company

Hardener of Sodium Silicate-Magnesium Chloride

1. Selection of hardener
The common hardeners of sodium silicate binder are ammonium chloride, magnesium chloride, alumina, etc. In order to reduce the dosage of ammonium chloride, ammonium chloride-magnesium chloride composite hardener scheme is selected. In this scheme, only ammonium chloride is used to harden the first two layers and magnesium chloride is used to harden the reinforced layer, thus significantly reducing the usage of ammonium chloride.

2. Ammonium chloride-magnesium chloride composite hardening experiment
The preparation of ammonium chloride hardener only needs to be prepared according to a certain concentration under the condition of detection conditions. Under the condition of no detection, only a small amount of solid ammonium chloride needs to be kept in the tank solution.
The density of magnesium chloride solution is only 1.22 g/cm3. From the shell pouring experiment, it can be seen that the surface quality profile of the casting is clear and the surface is smooth.

3. Analysis of practical value of magnesium chloride hardener
(1) The shell strength of magnesium chloride hardener is relatively high, and the original shell is generally 6-8 layers. Thick and large castings are coated with 8 layers and need to be reinforced with iron wires. After magnesium chloride hardener is used, only 5 layers are required for general castings and 6 layers are required for thick and large castings, and no iron wire reinforcement is required.
(2) Magnesium chloride hardened shell, ammonium chloride in dewaxing tank solution only needs to be prepared by 2%-3%. According to the tank liquid consumption, only 2%-3% is added. The supplement amount of ammonium chloride should be controlled below 0.5 kg per day on average. The reduction of ammonium chloride consumption will save a lot of expenses every year.
(3) Hardening with magnesium chloride takes only 10 minutes for natural drying due to the short hardening time, which is much shorter than that of ammonium chloride, thus improving the production efficiency.
(4) Utilization of recovered sand. The hardened shell with magnesium chloride has high strength, and 90% of recovered sand can be used. Only a small amount of crushed powder cannot be used, which is difficult to achieve by ammonium chloride hardened shell.