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