Corporate America sold record-shattering amounts of stock in May. IPOs and other equity issuances were overshadowed this spring as stock markets tanked and corporates rushed to raised debt instead. But volatility has faded and markets have rebounded, thanks in part to stimulus from the Federal Reserve. Stock issuance is surging again, producing more than $70 billion in deals in May. Companies are stockpiling cash in case of another downturn — some to protect themselves in case revenues disappear, and others so they can pounce on M&A deals that may arise.