Steel production is heavily subsidised by the Chinese government and, because of these huge subsidies, manufacturers can afford to dump steel at or below the actual cost of production. Once China has a virtual monopoly on steel production and our own and other EU steel industries have got rid of their own steel production industry, perhaps China will no longer choose to subsidise the industry since we and other countries will have almost no option but to buy from China, even if the cost rises substantially.
Also, in 2013 the New York Times carried an article that was critical of the US's over-dependence on Chinese steel, referring in particular to the many safety scandals that have arisen with all sorts of products manufactured in China:
"In the case of bridges, six have collapsed in China since July 2011. The official Zinhua News Agency has acknowledged that shoddy construction and inferior building materials were contributing factors".
"When California bought Chinese steel to renovate and extend the San Francisco-Oakland Bay Bridge, problems like faulty welds by a Chinese fabricator delayed the project for months and led to huge cost overruns. These deals eroded much of the expected savings."
In 2015, ABC Australia expressed similar concerns:
".... The Australian Steel Institute and the Welding Technology Institute of Australia say some of the fabricated steel entering the country has serious quality defects" - and the article goes on to give several examples.