SAISC TECHNICAL
released – which is bad news because steel and hydrogen are mortal enemies . By the way we do not cover underwater welding at all .
This next explanation takes the prize for the most entertaining comment ( probably ever ) to the otherwise very boring job of exam marker :
” MIG / MAG welding protects the molten pool by running a gas excretion before the weld – something akin to stomach problems ”
In this article , as we share with you some of their ideas , our grateful thanks go out to the 200 or so students who attended my course in the last year either at the University of KZN or University of Witwatersrand who produced these out of the box ( into the fire ) suggestions .
Welding related issues The course devotes at least two hours to welding issues . It covers subjects like the main welding processes used in structural steel fabrication ( SMAW , GMAW , FCAW and SAW – and if you do not know what these acronyms stand for we suggest you read up some background information on welding which is summarised in the Red Book , Chapter 7 ), weld positions , defects NDT and the like .
One of my quite often used questions is to name 3 of the 4 welding processes and allow them to use the recognized acronyms . Maybe if we used the SABS welding process to weld some mouths shut we may be able to improve the financial position of this SOE . Other unacceptable answers offered include SABS and believe it or not , even SAISC .
Just to confuse them more during their first field visit they go to tube makers to see how they go about their business . Our grateful thanks go out to Mactubing and Robor who for many tears now have been good enough to allow us to bring 50 invading students to get to grips with their processes . During this visit they see induction welding methods used to join the 2 open ends of the newly shaped circular profile ( which literally melts the 2 surfaces and squashes the molten edges together ).
To see if the students even notice that this is not one of the methods discussed in the lecture theatre , I ask them to comment on the difference between the tube welding process and the other 4 normal structural welding processes . I expect answers to include the words “ induction welding without the addition of additional welding rod material ”. Clearly one of the tube makers has an edge on the others because he has a source of tiny welders so that they can “… send the man on the inside of the tube to do a smooth weld ”.
I guess additional confusion is caused by the process of scarfing ( a chisel like removal of the welds externally and for liquid carrying pipes internally )
When asked to name some of the defects that can occur in welding ( e . g . cracks , porosity , overlap , undercut , poor shape etc .) how on earth can we overcome this one “… when iron is strong it eats up metal itself ” ?
I guess our scientists will just have to find a way of putting a stop to this cannibalistic behaviour . Or what about this one : “ A non-zero relative speed between welder and item being welded ”
Wow maybe he has discovered a magic increase in productivity of welder ’ s technique ?
Lastly on welding , the latest method of protecting the weld pool ( I am expecting [ maybe I expect too much , perhaps that word should be hoping for !] something like a gas shield as in GMAW or flux and a chemical reaction to create a gas shield around the molten weld pool as in SMAW ). “ Continuously run water over the welding section during weld ”.
That is after I explain how moisture ( water ) is H 2 0 and in a chemical reaction like we get at the welding arc , hydrogen will be
... I guess that ’ s what he thought about the course .
( Passive ) fire protection issues
A complete lecture is spent on the reasons we passively fire protect some steel structures , which types of structures are exempt , how long the steel must be protected and what the common methods of passive protection are . Ultimately I explain carefully that if steel reaches a temperature of 600 ° C it loses 70 % of its strength .
So no prizes for guessing what one of my favourite questions is ? I expect the answers to include the words “ 600 ° C ” and “ loses 70 % of its strength ”.
Some of the gems we received this year are :
• “ 450 ° C – The steel expands which can cause it to crack and buckle ”.
• “ 450 ° C – It is not easy to melt steel ”. ( I guess all those steel mills going out of business in the current poor demand situation would have saved $ Billions if they could get this one right !)
• “ 600 ° C – Steel can cause things around it to catch alight if it becomes too hot ”. ( And there I was thinking that it was the “ things around it ” burning that caused the steel to get hot !)
• “ 30 ° C – The reason is that steel contains chemical elements that will cause explosions at this temperature ”. ( Move over Mr Alfred Nobel , what was all the fuss about making unstable dynamite , you should have done more research into hot steel !)
And then let ’ s use the atom bomb to swot the proverbial fly ... “ 3000 ° C – It is suitable for any failure during the fire ”. That for sure is right , it will nuke anyone or anything near or in that fire !
Steel Construction Vol . 40 No . 2 2016 21