World number one Nelly Korda has surged into the lead at the Women's Open at St Andrews, moving three shots clear of the field at the halfway point of the final major of the year.

High-profile Australians Hannah Green (7-over) and Minjee Lee (9-over) failed to make the cut.

Green shot three birdies but also recorded five bogeys to score a 2-over-par 74 in the second round on the Old Course.

Lee struggled in the second round with a 3-over 75.

Korda, a two-time major winner, posted a 4-under 68 in a windswept second round.

The American is 8-under for the tournament, with countrywoman and defending champion, Lilia Vu, and England's Charley Hull three strokes back in a share of second place.

"I'm just trying to stay very present and not think about anything other than one shot at a time," said Korda, who has never finished better than ninth in the Women's Open.

"And whatever golf and links golf throws at me, I'm going to take it head on."

Steph Kyriacou is the leading Australian after two rounds in a tie for 21st place at even-par.

Kyriacou balanced six birdies with two bogeys to produce a 4-under 68 in the second round.

Grace Kim scraped through to the weekend at 4-over.

She managed a 1-under 71in the second round.

AAP/ABC