Two more major American steel producers, including U.S. Steel Crp., the nation's largest, announced yesterday they are joining an industry-wide move to raise prices 5.5 per cent beginning Feb. 1 - cementing a price-boosting effort that began last week end.

The increase is a line with 5.5 per cent price rise announced Monday by Bethlehem Steel Corp., the second-biggest producer. A smaller steel maker, the Wheeling-Pittsburgh Steel Corp., immediately rolled back a 7 per cent boost it had proposed on Sunday.

The action by U.S. Steel and the National Steel Corp., another large producer, means those 5.5 per cent increase will become a standard for the entire industry, unless the steel makers find they're unable to sell at those prices - a prospect most analysts view as unlikely.

Both firms scheduled price boosts for all sheet, rods, carbon wire and plate products for Feb. 1, with a second increase - to cover tin-mill products, oil-country tubular goods and structual shapes and piling - to become effective March 1.

A few hours after the U.S. Steel announcement, the Lukens Steel Co., of Coastesville, Pa., said it would raise prices on alloy steel plate by about 2.6 per cent and prices of carbon steel by 5 per cent. both effective on Feb. 6. Other firms were expected to follow suit.

U.S. Steel offered no justification for its decision to go along with the industry-wide boost. However, David M. Roderick, the company's president, predicted the increase earlier this month on grounds of sharply rising labor and energy costs.

Wheeling-Pittsburgh said it was "very disappointed" that other sheet-steel producers did not follow its earlier proposal for a 7 per cent price rise effective Jan. 3. However, Dennis J. Carney, the company's president, said the firm would "remain competitive" with the rest of the industry.

Ironically, the price boost is expected to reduce the protection the industry will receive against imports under the Carter administration's new minimum pricing plan. Under the new program, the more domestic steel makers raise prices, the more imports the government allow in.

The White House indicated yesterday it was relieved by the U.S. Steel action in undercutting the Wheeling-Pittsburgh boost. The Council on Wage and Price Stability had conceded some price increases were justified, but had decried the 7 per cent proposal as excessive.

Yesterday, Barry M. Bosworth, the Council's director, said the 5.5 per cent price boost would be "not all that disturbing if it represents the major price increase for the year." However, he added, "if it is representative of further increases to come, steel will be a serious inflation problem."