Companies tapped the credit markets for more than $21 billion in new bond issues last week. Nearly half the total was companies headquartered overseas visiting the U.S. credit markets to swap their bonds for greenbacks -- lots of greenbacks.

Mining giant BHP Billiton (NYSE: BHP) led the credit charge with $5.25 billion spread across five bond issues. Bond coupons ranged from 1% on three-year notes to 4.125% on 30-year paper. The "Use of Proceeds" section in the SEC filing states, "We intend to use the net proceeds from the offering of the notes for general corporate purposes, including repayment of commercial paper and repayment of US$625 million global bonds due March 29, 2012 and 1,250 million [euros] medium-term notes due April 4, 2012." It's interesting that BHP would opt to borrow dollars to repay euro-denominated paper.

Steel giant ArcelorMittal (NYSE: MT) rolled out $3 billion of new paper with maturity ranging from three to 10 years. A credit rating that isn't quite as tough as steel meant ArcelorMittal needed to pay up a bit. Coupons ranged from 3.75% for the three-year paper to 6.25% for the 10-year stuff. About half of the new cash will be used to buy back higher rate debt.

Honda's American Honda Finance drove off with $1.75 billion in a two-tiered private deal.

Brazil's Banco Bradesco (NYSE: BBD) and Singapore's DBS Bank each snuck in at the billion-dollar borrowing mark. Banco Bradesco's offering was a private placement and DBS didn't offer anything beyond general business purposes as a use for the money.

Not all the big borrowers were overseas companies. Wells Fargo (NYSE: WFC) rolled out $1.25 billion of five-year floating rate notes. This shareholder wonders why the bank chose floating rate notes rather than locking in record low rates. Wells didn't provide any use of proceeds information beyond "general corporate purposes." Cargill and John Deere's (NYSE: DE) finance subsidiary borrowed a billion each.

Top quality bond yields continue to be very low. It's hard to imagine many scenarios where a 30-year bond at 4-ish percent turns out to be a bargain (for the purchaser). There are higher rates out there, but higher credit risks typically come along for the ride. I'm underweight bond funds in my portfolio and don't see any reason for that to change in the near future.