Hi,
I have a small 200 amp AC welder and I'm welding boat frames with that ie. butt joining 3/8 x 3 flat bar. I'm using 6013 rods because 7018AC isn't available here in Finland and the output voltage of my welder is too low for regular 7018. Now I'm worried about the hydrogen embrittlement of the 6013 and also notch toughness in low temperatures. Do you think this is an issue? I will use a mig machine (that I will purchase later) with solid wire for the hull plating. Do you think this will lead to a strong enough structure? Or should I be worried about the frames welded with 6013? The boat will be used for serious offshore cruising.
Esa
Get thee a good welding engineer or metallurgical engineer if you are resposible for these designs.
There is as much to be concerned about with the base material as there is with the filler metal with regards to notch toughness and low temperature. I speak from the experience of having an electroslag procedure rejected by the Navy for "unacceptable toughness at minus XX deg F" - until we politely pointed out that our weld metal had 4-5 ft lbs higher toughness than the crappy casting that had been specified.
Without more information as to design temperatures, base metal specification, etc., it isn't possible to provide a good answer - except that if you are concerned about notch toughness and hydrogen embrittlement, stay away from 6013.
Esa,
Have you looked at www.esab.fi ? It doesn't make much sense to me, but hopefully it will to you! Esab in the US has the following Atom-Arc 7018AC rod (W48.1, E48019, AWS A5.1):
http://www.esabna.com/main.cfm?category=03&pageId=catalog.cfm&category_desc=Products
They should be able to get you set up.
-dseman
By Esa
Date 11-03-2003 09:11
Yes, I have looked. It says there: "Atom Arc 7018AC is a product specifically designed to optimum arc characteristics when used with AC power sources having 75 to 80 open circuit voltage."
The problem is my machine only has 55 V open circuit voltage.
For example Lincoln promises that their 7018AC works also with these low open circuit voltage machines. I just wonder how is the Esab rod different when it requires more voltage.
When using an E-6013 electrode, the main thing to be concerned about is its poor penetration, not hydrogen embrittlement.
E-6013 has a rutilic coating and does not contain hydrogen, as the cellulosic electrodes do. Rutile is the chemical name of titanium dioxide.
As long as you keep the electrodes in an oven at the temperature specified on the containing box, moisture (and thus hydrogen) will be kept off.
A more important concern about E-6013 is that its penetration is poor, and you'll have to design the joints so as to overcome that limitation.
Many American engineering and construction companies, such as M.W. Kellogg (one of the largest), don't accept E-6012/6013 electrodes for pressure containing parts. However, years ago, I worked in a large fertilizer plant project where the Engineer was M.W. Kellogg. The plant was located in an European country. Well, Kellogg issued an instruction saying that, as E-6012/6013 electrodes are largely used in Europe, even for pressure containg parts, that prohibition was released for that particular project.
Of course, it didn't mean that, due to a miracle from Heaven, E-6012/6013 electrodes (also called rutilic) changed all of a sudden their poor penetration properties. So, take all precautions to ensure that a good penetration is obtained. This begins with the proper design of the welding ends, followed by a proper welding procedure.
As for the notch toughness (also called impact strength) of the electrodes, you'll find it written on the containing box.
And now let me ask a curious question: you live in Finland, a metric and ISO country. How it comes that the electrodes sold in Finland follow the AWS designation instead of the ISO one?
Giovanni S. Crisi
Sao Paulo - Brazil
By Esa
Date 11-12-2003 12:44
They don't follow the AWS designation. They do follow the ISO one but almost all manufacturers print both on the containing box. And I think most people here in this forum deals with the AWS one so it's better to use it here. I also like it more because it's more simple. Do you think anybody would have answered if I'd asked something about E 43 3 R 11? By the way most people in Finland use the "Esab designation". The most popular rods are Esab OK48.00 and OK46.00 in that order. So people just say "fortyeight" and "fortysix". The first one is 7018 and second 6013 according to AWS.
I have done some tests with the "46" and I can get quite good penetration.(At least I think so.) I just have to use quite high current say 150 amps.
Esa
Hydrogeon embrittlement is very much a factor if you welded under conditions that would create this type of weld defect. E-7018 low hydrgeon electrodes, combined with other parameters such as weld fit-up; cleanliness of the weld joint; cleanliness of the root weld; and cleanliness of subsequent weld passes. Additionally, weld rod control measures, such as using dry electrodes, would certainly help. As for the thin material you've welded with a E60 series rod, the notch toughness will be affected if you welded a A-36 or equivalent grade steel. If you are concerned, do a charpy impact test and forget about it. If it falls below the recommended values of ASTM it's questionable.
Hope this helps,
Vonash
Hi Esa
I would think that in Norway, you will be seeing very low temperatures on a "serious" off-shore boating application. (Possibly substantially below 0°C.) Under this situation, you need to ensure that both your steel being used for the boat frames and the filler metal will meet the required low temperature impact properties. If you have the correct steel, for the low temperature application, then I would definately not go with the E6013 electrode. The reason being that these electrodes are not manufactured and supplied to meet ANY given impact properties. As such, you may end up with a batch of electrodes that have rather high Ductile to Brittle Transition Temperatures. (DBTT's) This is not something you want to find out one very cold stormy night. (Remember the Liberty ships?)
Regarding the hydrogen embrittlement, I would not worry too much, because the sections you are welding seem rather thin. This is however only of theoretical significance, because I believe your bigger problem lies with the impact properties.
Regards
Niekie Jooste
Fabristruct Solutions
Niekie:
there's a statement on your answer I don't understand. At a "substantially below zero Celsius" temperature, water has long frozen up, and Eas's boats won't be able to navigate on pure ice.
The lowest possible temperature of the Baltic sea (Esa lives in Finland, not Norway) that Esa can put his boats to navigate on is a few tenths of degrees Celsius above, never below zero.
Another thing. You make reference to the Liberty ships. At least here in Brazil, it's not clear why the sank during World War II. One author wrote on his book that it was because of brittleness, as you say. But another author wrote that it was because of residual stresses after welding, which in those days (early 40'ies) were not clearly known and that caused the welds to break up during rough sea. What's the truth?
Giovanni S. Crisi
Prof. Crisi,
This one got me to thinking.
Atlantic sea water actually won't freeze until it reaches at least -1.91 Degrees (C). The Salinity keeps water from freezing, the tempurature for freezing drops as the salt increases. http://www.mit.edu/~goodmanj/madsci/888588209.Es.r.html
Also I was thinking that as ship hulls go, only a portion is submerged and that much of the ship could indeed be exposed to sub zero temperatures.
Of course you're right, Lawrence, and I don't need to go the the MIT site to give you credit.
I must confess, though, that I didn't imagine that sea water salinity (3 to 4% depending on the location and period of the year) was sufficient to lower its freezing point by as much as 2 degrees C. I thought (erroneously, as you pointed out) that the freezing point lowering was just a few tenths of degree C.
Lesson to be taken: Don't rely on your imagination. Check the Data!
Giovanni Crisi
Hi Prof Crisi
I live in sunny South Africa, so please forgive me if my visions of Scandenavia are incorrect, but I would think that if a particularly cold wintery arctic wind was blowing, the ambient temperature must surely be substantially below zero celcius. (Maybe -10 or even -20°C?) Certainly the fact that the water would not be much below zero would help the submerged section to be at around this same temperature, but the rest of the boat must surely be experiencing much lower temperatures.
Keeping this in mind, a fractured critical structural member, even if not submerged, will surely lead to the loss of the vessel in a stormy sea?
Regarding the Liberty ships, I can only go with the information that I have, which is that they were made from steel with poor impact properties. (Poor fracture toughness.) This caused them to crack in half due to the cold temperatures they experienced at sea. In their case, I understand that the DBTT was even substantially above zero celcius.
Residual stresses by themselves should not lead to the steel fracturing, if the steel had good fracture toughness. It will just distort. As such, I do not believe that their failure could be ascribed to residual stresses alone.
Regards
Niekie Jooste
Fabristruct Solutions
Of course you're right, Niekie. Living in a tropical country, I forgot that close to the polar circle, outdoor temperatures can go down to 30 degrees C below.
By the way, what does DBTT mean? You know, English is not my mother language.
Giovanni Crisi
DBTT = Ductile to Brittle Transition Temperature
John Wright
So those guys got to cross the north atlantic- freezing cold, big storms, big waves, floating ice, u-boats, and then to top it off their boats were defective. Wow...
Bill
I found out that basic A-36 grade steel has notch toughness guaranteed to be 27 J in 20 C temperature. In any case notch toughness of E60 series rod will be better. So the weld wouldn't be the weakest point in the structure. Correct me if I'm wrong.
Esa
Hi Esa
A-36 steel has NO requirement for impact testing. Impact testing is a suplementary requirement that will only be carried out if specifically called for.
Are you sure about the 27J at 20°C, because that is not a great value. This same steel at -20°C will have almost no toughness.
Keeping in mind that the E6013 electrodes also have no defined impact requirements, you are in the same boat (excuse the pun) with the electrodes as you are with the A36 steel. - Maybe it is OK, but maybe not. Are you prepared to risk this?
If I was you, I would try to get hold of somebody in the commercial boat building industry around your part of the world, and find out what they are doing. For a boat to be used in a nice tropical location, I would have little problems with your approach. For a rather cold part of the world, I would be rather uncomefortable with the approach.
Hope this helps.
Regards
Niekie Jooste
Fabristruct Solutions
Here is just about everything you wanted to know about toughness and 6013 electrodes that I just happened to stumble on today.
http://www.aws.org/wj/supplement/07-2002-DERISSONE-s.pdf
