Unknown levels of boron added to reinforced steel bars exported from China could spell a disaster waiting to happen
A report in the UK’s Telegraph newspaper claims that ‘Chinese steel being imported into the UK could be putting lives and buildings at risk’. And the UK is importing more and more reinforced bars – or rebar – from China: up from 2 per cent of construction requirements in 2013 to 39 per cent today.
The problem has arisen because in order to gain export tax rebates, Chinese steel makers sometimes add unspecified amounts of boron to their product, which then qualifies as an alloy - and is more prone to cracking.
According international engineering institution, The Welding Institute rebar that has in excess of 5 ppm boron requires different welding techniques to be employed. However, the only way to know how much boron rebar contains, every bar needs to be individually tested.
A paper produced by trade body, UK Steel explains that a ‘significant, but unknown’ proportion of the Chinese rebar sold in the UK contains ‘boron in excess of 8 parts per million’. In some instances, tests have shown levels of boron as high as 30 ppm.
UK Steel offers this guidance: “Our advice to any fabricator with stocks of Chinese rebar is that they should urgently identify any bars containing more than 5 ppm of boron and segregate them. These bars should not be used in structures requiring welding until staff have been trained in the specific welding techniques required.”
The paper concludes that there is therefore ‘a real, but unquantifiable, risk that welded structures using Chinese rebar could fail’.
According to the Telegraph, UK Steel is in the process of asking the British Standards Institute to ‘make a simple amendment to regulations, which would ensure that consumers of rebar know what they are buying.”
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