WELDING OF ASTM A515 GRADE 70 AND ASTM A285 GRADE A

Date 01-31-2007 20:13

Both are low carbon steels for pressure vessels, easy to weld.
If you're going to use SMAW (stick welding) I'd suggest E-7018. The steel should be warm to the hand before start welding (important precaution in cold climates). After the weld is complete, backgouge the root from the inside of the vessel by means of carbon electrode and remake it (the root). Cleanliness of the whole operation is obvious.
Depending on the plate thickness and the Code the vessel was designed to, it will be necessary to PWHT the weld. Also depending on the design Code and customer requirements, radiograph tests will have to be performed.
By the way, which Code (or standard) the vessel was designed to?
Giovanni S. Crisi
Sao Paulo - Brazil

By GRoberts (***)

Date 02-01-2007 04:02

700C is very very hot for carbon steel. I assume that the carbon steel will not get near that temperature due to insulation?

When welding those two grades of carbon steel, any typical carbon steel filler will work. E7018 (as the esteemed Giovanni recommended), E71T-1, ER70S-6, or carbon steel SAW as well. If more strength at higher temp is needed than typcial carbon steel fillers is required, either look for a carbon steel filler metal with higher carbon content. Weld filler normally have a lower carbon content than the base metal. These could be electrodes specifically desined for stress relieving. Or you could look for an electrode with 1/2% Mo, such as 7018-A1 or E81T1-A1.

By G.S.Crisi (****)

Date 02-01-2007 18:38

Greg,
thankyou for your kind words regarding my person.
I assume that the vessel Pete is talking about (lead kettle, he says) will be used to melt lead. So, it'll be internally lined with refractory bricks or concrete, and the temperature the steel will be subject to won't be 700 degrees C. It'll be maybe 300 - 350 ºC, which A-515 withstands.
But this is an assumption that Pete should clear up.
Giovanni S. Crisi

By js55

Date 02-01-2007 19:12

This brings up an interesting question. When determining appropriate weld material is it necessary a welding engineer for a fabricator or repair contractor determine that the weld material to be used is acceptable per design or service, a result which may or may not be determinable. Or would it be more appropriate to determine if it equals or exceeds the properties of the existent base material, properties which may be analogous given matching fillers?
This may seem like a nit picky distinction but it may also be important.
This type of thing pops up a lot in corrosion services it seems to me. And often the base line info available isn't if the weld material is suitable for a particular service, which can be very specific, but if it has been proven in generalized corrosion testing to be relativley more resistent than the base material applied to the design.

By GRoberts (***)

Date 02-01-2007 20:36

When steel is being used for structural purposes where environment is not a factor (such as weathering steel, high temperatures, corrosion issues, etc), then generally matching the base metal properties will be acceptable. When things like corrosion/creep, etc come into play, the environment must be know to make a sound decision. For instance, if welding on 316 that is in high temperature service, it could be said that using a dual classified filler metal such as 316/316L will match the base metal. However, even though it meets the AWS spec for 316, it may not have enough carbon to resist creep, and could lead to early failure.

By js55

Date 02-01-2007 22:44

I suppose the answer should be that these things should be left to the design engineers and not the welding engineers. Or better, a welding engineer functioning in design. Corrosion services can be so unique that if it is an initial application actual service medium and conditions testing will be the only way to be sure. ASTM tests only provide alloy general ranking and rules of thumb. If it is an existing sevice then a successful BM base line will help.