SAISC FEATURE
Chinese Boron Steel:
A few words of
warning for our fabricators
By Spencer Erling, Education Director, SAISC
The hardness of the heat affected zone goes up with steel with Boron in, even at fairly low percentages( 1 to 4 parts per million or. 0004 %)
Background It is relatively common knowledge that Chinese steel mills added some Boron to their chemical composition of export steels.
The reasoning behind this was the export tax that China imposed on Carbon steel( the full name of the steel we use). But if the mill added some Boron( as low as. 0008 %) the steel was considered an alloy steel with a substantial reduction in the export tax or effectively an export subsidy.
Whilst some changes have been brought about to the Boron steel tax reduction, some Chinese mills are now adding( apparently with some difficulty) Chromium into the mix.
The impact on fabrication due to adding Boron to steel It is common knowledge that the Boron hardens the steel, generally without affecting the ability of the steel to meet the requirements of specifications such as S355JR.
Does the Boron have an impact on welding? The answer is probably yes.
Some of the information I found on Google is clear that the hardness of the heat affected zone goes up with steel with Boron in even at fairly low percentages( 1 to 4 parts per million or. 0004 %). Boron percentages in steel exported is a minimum of. 0008 %.
Conclusion Talk to your friendly welding engineer. Show him material certificates of steel from China with Boron in the steel. Let him confirm that your Weld Procedure Specifications are still suitable. The speed of cooling has a big impact on this hardness, so pre-heating requirements could be affected.
PS If your steel contains chromium the question to your welding advisor is just as valid.
Ed. A special thanks to Bruce Saxby for alerting us to this issue during his talks presented at the Basics of Steel course 2016.
8 Steel Construction Vol. 40 No. 3 2016