Strontium modifier has the same effect as the sodium salt modifier. Strontium modifier can achieve the purpose of improving material performance. Add some Sr modifier to the liquid metal. Form a large number of dispersed artificially produced non-spontaneous crystal nuclei in the molten metal, so as to obtain fine casting grains.
Features of Sr Modifier
1. Less oxidation, easy to add and control, less problem of over-deterioration.
2. Strontium is not volatile, so the effective time of deterioration can be extended.
3. Convenient treatment, no vapor precipitation.
4. The strontium modifier is easy to keep.
5. After treatment, the alloy has good fluidity and little sensitivity to the wall thickness of the casting.
Because the density of strontium is greater than that of aluminum liquid, it is precipitated in a suspended state. And the contact time with aluminum liquid is long, and the utilization rate can reach 60% to 90%. Strontium can absorb hydrogen and it needs to remove the hydrogen. Due to the intense reaction with chlorine, nitrogen should be used to remove hydrogen. In order to make the modification treatment more effective, there must be a certain retention time, which depends on the content of Al4Sr in the master alloy. After remelting, the aluminum alloy treated with strontium modifier will not have an obvious loss of modification effect, and can obtain permanent modification effect.