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Up Topic Welding Industry / Technical Discussions / Moisture in metal or chemical reaction?
- - By S. WINAI (**) Date 09-05-2012 03:29
Dear, Senior AWS welding forum

I  try to heating steels difference surface in the morning time. one surface is primer coating paint and other one is bare steel surface.( pls view photograph attend). When during heating water observed.

My question is. Where this water come from. Come from base metal? Come from primer coating paint? Or come from chemical reaction between the fuel (typically a hydrocarbon) and the oxygen?

Some of my colleague said' come from moisture in base metal. Steel absorb moisture in the night time  when do  preheating in the morning moisture will come out.
Some said' that moisture come from primer coating. Who is correct? Both of them is a degree holder. But im not.

Pls help to share the correct answer.

Thanks in advance

winai
Parent - By Lawrence (*****) Date 09-05-2012 03:32
Byproduct of oxyfuel heating....  There are a number of excellent threads on this issue that are fresh on the forum..  Try the search function and you will be pleased I think.

Steel is not sponge  :)
Parent - - By welderbrent (*****) Date 09-05-2012 03:37 Edited 09-05-2012 03:50
Interesting, one of the best threads recently covering this was started by....YOU.  Now you are covering some of the same ground again?  Here's the link:

http://www.aws.org/cgi-bin/mwf/board_show.pl?tid=30882#tid30882

And, here is another that is probably even more complete:

http://www.aws.org/cgi-bin/mwf/topic_show.pl?tid=30753

Have a Great Day,  Brent
Parent - By Shane Feder (****) Date 09-05-2012 04:38
K.Winai,
Sawasdee khrab.

You have received a very good response to this question on the eng-tips forum by the same person who has given a very good description on this forum.
You will not get a better explanation than what has been given by this gentleman,
Cheers,
K. Dek Dee
Parent - - By S. WINAI (**) Date 09-05-2012 04:42
Hi, Thanks

i have search and reading a lot in this AWS welding forum. im believe this byproduct combustion.but  i still  like to hear more from senior experience members here. i have mention before. they r degree holder but im not. im looking forward to get some reference book to make they believe what we said here in the forum.

any one have link or where i can find it. pls help to share.

Thanks

winai
Parent - By js55 (*****) Date 09-05-2012 14:19
Try the book, "Welding Steels Without Hydrogen Cracking".  The list of contributors are very distinguished.
Parent - By DaveBoyer (*****) Date 09-06-2012 05:58
As has been posted many times before, the moisture You see when heating with a flame is the water vapor from combustion condensing on the cold steel.

Rust does absorb some moisture, but that is not what You are seeing.

Some paint, particularly loose paint may absorb or trap moisture, but that is not what You are seeing.

Paint, oil, rust or other debris on the steel can be a source of hydrogen that may contribute to weld cracking, but that does not cause the moisture You are seeing when You preheat.

Sound steel with no porosity absorbs no water.
Parent - - By 357max (***) Date 09-05-2012 14:07
AWS' Ninth Edition Welding Handbook Volume 2 Welding Processes, Part 1 page 476 ~ "The complete combustion of acetylene is theoretically represented by the following chemical equation: C2H2 + 2.5 O2 -> 2 CO2 + H2O
This equation indicates that one volume of acetylene (C2H2) and 2.5 volumes of oxygen (O2) react to produce two volumes of carbon dioxide (CO2) and one volume of water vapor (H2O), The volumetric ratio of oxygen to acetylene is 2.5 to 1."
ps sorry didn't use the subscript for the equation.
Parent - - By S. WINAI (**) Date 09-06-2012 09:29 Edited 09-06-2012 13:21
Hi, Thanks all
Again confusing!:confused:
how to consideration between cold and warm steels. because when heating with a flame is the water observed  on the cold steel surface.but warm steel not.
So! how much temperature we can call cold steel and how much temperature we should call warm steel. Example if room temperture is 25 degree C. some one said is hot. some one said cold. other said just nice. but this is a human feeling. back to the question! how to justify steels is cold or warm?

Best regards,
winai
Parent - - By Tyrone (***) Date 09-06-2012 10:37
Winai,
Heating up the steel (preheat) is done to safely weld without cracking issues.  What does your weld procedure say for preheat before welding? The Weld Engineer should be performing calculations to determine the min/max temperature.
Tyrone
Parent - - By S. WINAI (**) Date 09-08-2012 04:54
Tyrone,
Because WPS state minimum preheat: preheat to remove moisture. so now i need to find out what is mean of this moisture. i need to remove by preheat and how much temperature steel can collect moisture. if i not miss understanding the moisture should be evidence can see by naked eye, vapor or water then i should remove it.

do u believe that steel can absorb moisture?if did then i need to do the preheat every part or every joint before start welding even plate is1/8"(3 mm) thick.follow the WPS state!
if i do that. oh god! my welding job should be always delay and i will not got any profit bonus. oh No!:cry:
Parent - - By electrode (***) Date 09-08-2012 17:03
Sir,

"do u believe that steel can absorb moisture?"

Physics supplies only little to believe.

After all what's being said and done here along this thread; may I kindly ask what sort of evidence is needed more than even already provided?

Some of the most experienced individuals in this forum have openly shared both their personal practical and theoretical knowledge to clear the muddy water.

Is it I who's overlooking something or is it really that difficult to get your head around the reasonable and meaningful statements made?

As for being the latter the case; have fun in preheating your 3 mm thick workpieces - whatever the material grade shows!

Again. The most signicficant statement, in my eyes straightforward hitting the nail, comes from Mr Lawrence who was saying: "Steel is not a sponge!"
Parent - - By 46.00 (****) Date 09-08-2012 20:52
I have deliberately refrained from posting on this thread, and indeed this forum for quite a while because of negative feelings and replies. BUT BY GOD MR S.WINAI, HOW MANY TIMES DO YOU NEED TELLING?
Parent - By Superflux (****) Date 09-08-2012 21:11
In all fairness to the OP, I think Mr. S. Wanai is up against superiors that don't have a clue (they supposedly have college degrees?).
Unfortunately, there is nothing else we can give him with which to battle these forces of gross ignorance.
Parent - - By electrode (***) Date 09-09-2012 10:35
46.00,

"I have deliberately refrained from posting on this thread, and indeed this forum for quite a while because of negative feelings and replies."

I see the truth of it.

I for myself was also hesitating to post something on this.

Nonetheless, and with all due respect; I finally couldn't resist since I was suspecting to really overlook something crucial along this thread.

However, I seem to derive from yours and SUPERFLUX' response, I did rather not.
Parent - - By ssbn727 (*****) Date 09-10-2012 06:02
Gentlemen,

I believe there's a problem with the lack of language communication skills from the OP which is why the posts are rather confusing yet not too hard enough to interpret most of the post... This happens a lot in the forum as we get a lot of queries from different parts of the world... Sometimes the posts can be frustrating and sometimes they're totally hilarious:lol::yell::lol::wink: Enjoy!:roll::cool:

Respectfully,
Henry
Parent - - By Shane Feder (****) Date 09-10-2012 11:14
electrode / 46.00,
I have over the years fired both barrels at persons who are too lazy to do research and they come on here and want us to do it for them.
As I always say, when you have exhausted all channels and then still can't find the answer come on here and there are some very experienced people who are more than willing to assist with their time freely to help.
I think this is a little different.
K.Winai is getting grief from his "degree qualified" superiors who do not appear to have a clue.
He needs something definitive to throw on the table to shut them up.
Al's description was brilliant, detailed and yet easy to understand but in the end it is only someones opinion from a welding forum.

K.Winai,
Print out Al's posts and give them to your superiors - may not shut them up but will at least put some doubts in their minds,
Regards,
Shane
Parent - By welderbrent (*****) Date 09-10-2012 15:09
And that is why I included the posts from two earlier threads about this very topic.  I felt they went so very far into all aspects of this question that it was not necessary to repeat the process.  There are many good explanations and examples that fully explain the moisture condition, pre-heat, and code application. 

All K.Winai needs to do is print those out and present his case.  And, if these guys are educated with degrees they should at least know how to read and be able to be challenged as to their current line of thinking.  Don't they teach having an open mind and to always be prepared to learn new things?

Just my two tin pennies worth.

Have a Great Day,  Brent
Parent - By 46.00 (****) Date 09-10-2012 18:45
Hi Shane, I completely understand what you are saying and I agree that to just expect answers without performing any research is the completely wrong way to go about these types of problems. Believe me, this question is on several other forums that I frequent and he has had the same answer on all, sometimes from the same person on two different forums. Alas what's more worrying is if a 'degree qualified' person/Engineer thinks solid steel can soak up water like a sponge? One would need to ask what these people have degrees in, 'cause it aint in any of the science/engineering subjects..................
Parent - By electrode (***) Date 09-16-2012 17:57
I see.

I should like to agree with "Al's description was brilliant, detailed and yet easy to understand..." what's been the root cause for my comments.

If these were considered rude - that certainly was not my intention.
Parent - By jwright650 (*****) Date 09-06-2012 11:43
Just for a reference and to give you a place to start...AWS D1.1 Table 3.2 shows several grades of materials and the associated welding processes and the recommended minimum preheat to help reduce cold cracking and hydrogen induced cracking. Take notice that these are mild steels with low tensile/yeild steels, but it should give you a place to start. You can also use Annex I in the back of D1.1 for higher strength steels that do not show up in Table 3.2 to determine the preheat and interpass temperature depending on the chemical composition(mainly carbon content) of the steel to be welded.
Parent - By DaveBoyer (*****) Date 09-07-2012 00:58 Edited 09-07-2012 01:03
The steel has to be above the dew point of the combustion byproducts of the flame to avoid condensation.

You won't have any condensation above 100c or 212f at sea level, that is for damn sure.
Up Topic Welding Industry / Technical Discussions / Moisture in metal or chemical reaction?

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