DHT is a mandatory requirement in the industries which everyone has to do just after the finishing of the welding, the hydrogen when came out from the weld at room temperature cause delayed cracking or cold cracking (it might take around 72 hours). While hydrogen comes out from the weld at a degree temperature of around 350 to 400 degree C, it will not cause cracking. So why does cracking occur at room temperature and not at the DHT temperature?