SEOUL, July 22 (Reuters) - South Korean steelmaker POSCO (005490.KS) posted its highest ever quarterly profit on Thursday, as strong industrial demand and surging steel prices boosted its revenue. Reporting by Joyce Lee; Additional reporting by Heekyong Yang; Editing by Sherry Jacob-Phillips and Subhranshu Sahu You have reached your article limit Register for FREE to continue using Reuters.com Free registration gives you access to: Unmatched, global, round-the-clock news Hand-picked insights that are easy to find and use Our Daily Briefing newsletter, delivering the day"s headlines right to your inbox