Companies are borrowing $74 billion in the U.S. investment-grade bond market this week, the most for any comparable period since records began in 1972. Since Tuesday, corporations including Coca-Cola Co., Walt Disney Co., and Apple Inc. have sold notes as yields have dropped. And the frenzy isn't letting up.

At least another $50 billion is projected for the rest of the month, and the activity is spilling over to junk bonds and leveraged loans as well. With more than $16 trillion of bonds in Europe and Asia paying negative yields, investors worldwide are snatching up debt that offers relatively higher returns, keeping demand strong in the United States.

"This is a great time for companies to refinance," Christian Hoffmann, a portfolio manager at Thornburg Investment Management, said. "Financing costs are near all-time lows, so I would not be surprised to see better high-yield companies coming to market and treating debt capital markets like a cheap buffet."