Engineering news
Low-grade Chinese steel imports which risk crack propagation during processing are entering the UK, a trade body has warned.
UK Steel, the trade body for the UK steel industry, said the imports failed to meet certain standards, and had a heightened risk of catastrophic failure in certain applications.
Ian Rodgers, director of UK Steel, said: “For the past few months it has become increasingly clear that some imported steel plates and sections from China are being supplied into the UK market which are not fully compliant with the requirements of the relevant standard.”
The EU specification for structural steel explicitly states that it applies only to 'non-alloy steels'. To qualify as 'non-alloy', a steel must comply with strict limits on the quantity of other metallic elements it contains. This 'non-alloy' classification amongst other things ensures that the steel is readily weldable without the need to apply any special welding parameters.
However instances have been reported of Chinese steel containing elevated levels of elements such as boron and chromium, said UK Steel. Chinese producers add these elements in order to qualify the steel as 'alloy' because alloy steel exports benefit from a tax rebate. However alloy steel plates and sections do not comply with the European standard for structural steel.
More importantly, these alloy additions can significantly affect the steel when being welded. Additions at these levels can cause the steel to crack on welding, a problem which may not show up until 48 hours later.
A similar problem can arise with copper-alloyed steel. Again, Chinese imports have been discovered with elevated levels of copper.
Rodgers added: “It is imperative that structural steel plates and sections with elevated alloy levels are treated with great care and where possible avoided totally for applications where welding is required, as there is a heightened risk of catastrophic failure.
“Our advice is that customers should carefully check the alloy content of Chinese structural steel before processing it.”