STEEL FIRMS STUDY USX <X> UNIT PRICE HIKE Two major steel companies said they were studying a price increase announced yesterday by USX Corp's USS steelmaking division. Spokesman for Armco Inc <AS> and Bethlehem Steel Corp <BS> said the proposed price hike was under study. Yesterday, USS said it plans to raise base prices on plate products by 20 dlrs a ton, or about five pct, effective with shipments October 4. A spokesman for LTV Steel Co, a unit of LTV Corp <QLTV>, declined comment, adding that the company does not make heavy plate and makes few other plate products. A spokesman for <National Steel Corp>, a joint venture of National Intergroup Inc <NII> and Nippon Kokan K.K., said the company is not in the product lines affected. Reached later, an Inland Steel Industries Inc <IAD> spokesman said the company was studying the pricing move. USX said the increase will be on all plate products, including carbon, high-strength low-alloy, strip mill and alloy plates. It also said it planned 20-dlr-a-ton increases on some special plate widths and thicknesses. Analysts have said firm prices for steel should contribute to better results at the nation's major steelmakers.