QuickLinks -- Click here to rapidly navigate through this document

Exhibit 23.1

CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

        We consent to the incorporation by reference in Registration Statement No. 33-46824 of Quanex Corporation on Form S-8 of our report dated June 23, 2004, appearing in this Annual Report on Form 11-K of the Quanex Corporation Hourly Bargaining Unit Employees Savings Plan for the year ended December 31, 2003.

/s/  DELOITTE & TOUCHE, LLP DELOITTE & TOUCHE, LLP

Houston, Texas
June 23, 2004

QuickLinks

Exhibit 23.1

CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM