Connecting the liquid hydrogen and liquid oxygen tanks, the intertank is built differently from the rest of the core stage. It is bolted together, not welded, with ribs on the outside for strength.
NASA
<a rel="nofollow" class="external free" href="https://www.nasa.gov/exploration/systems/sls/multimedia/hardware.html">https://www.nasa.gov/exploration/systems/sls/multimedia/hardware.html</a>