I need a strong way to connect chains to have enough strength. A 1/2 inch chain has a working load of 11,300 pounds but 1/2 inch quick links are only 6,500 pounds working load.
No.
Instead of one spot with a 6500-lb working load in your chain you now have two spots with 6500-lb working load in your chain.
Strength does not appear by adding two weak links.
Sounds like you have 2 shorter chains and need 1 longer so the quick link is needed? Cut open a link from an end, connect the 2 shorter ones and have a local welder close the link.