Welding E7010/8010 versur E7018 1

[jsobilo1354]

Can someone tell me if there is a specific advantage regarding the use of E7010/E8010 versus E7018 for CS and under what conditions are they preferred over one another. Also, regarding hydrogen underbead cracking (delayed cracking), is there a tensile strength or material thickness where low hydrogen electrodes become a factor in lowering the liklihood for underbead cracking? Thanks.

 

[metengr]

The E70XX and E80XX are two different strength filler metals are indicated by the numeric prefix. The XX is used to designate the desired position for welding (1 - all position, 2-horizontal and flat, 3-flat and 4-flat, overhead, horizontal and vertical down.

The last prefix in the XX has to do with rod covering and slag type from welding. You have various coverings depending on end use - cellulose, low hydrogen iron powder, sodium, potassium, etc.

Click on the link below to obtain information on the various types of coatings for covered electrodes. This handbook is fairly decent on providing covered electrode selection.

http://www.esabna.com/EUWeb/FM_handbook/577fm1_8.htm

Underbead cracking has more to do with base metal chemical composition and selection of proper preheat requirements to assure adequate diffusivity of hydrogen and to avoid the formation of harmful martensite in the base metal HAZ. My advice is to use low hydrogen, covered electrodes for welding medium to higher strength carbon and low alloy steels with the SMAW process. The low hydrogen covered electrode needs to be specified by the suffix designator H4 or H8 per AWS A5.1.

 

[jsobilo1354]

Thank you. One other clarification please. Since I am rather new to this and may be irrelavant, but how do I know what steel is mild, med. or high strehgth? What is the cut off or difference in them?

 

[metengr]

jsobilo1354;
Good question. I would suggest that you calculate the carbon equivalent (or CE) for the base metals that you are interested in joining. It is a good exercise in using the CE equation, as mentioned in the FAQ below.

faq330-1077

Typically, medium to higher strength steels will contain alloy elements that must be considered when welding. Using the CE will provide you to determine preheat requirements from published sources. Any steel with a CE that is above 0.45 should be welded with low hydrogen electrodes to avoid delayed cracking.

 

[jsobilo1354]

Thank-you for the clarification. Your knowledge of the subject matter and response is greatly appreciated.

 

[stanweld]

The principal advantage of using the E7010/E8010 electrodes over E7018 type electrodes is their ability to make full penetration, single side groove welds without backing (by a skilled welder). It's disadvantage is the high hydrogen content induced into the weld, which requires added preheating (added cost) to prevent hydrogen induced (cold) cracking (still greater cost if preheating is inadequate and cold cracking occurs). It also has a distinct advantage in reducing weld porosity when welding over coated sheet steels.

 

[SJones]

Would the principal advantage of the XX10s not be in their general ability to go very fast downhill as opposed to relatively few XX18s that can do the same? Apart from the low hydrogen versus cracking issue, the XX18s will give higher toughness values if this is an issue.

With respect to cracking (and its avoidance), take a look at ISO TR 17844

Steve Jones
Materials & Corrosion Engineer

http://www.pdo.co.om/pdo/

 

[stanweld]

Due to its "fast freeze" characteristics, availability in smaller diameters and lower operating amperage range, the EXX10 electrode has a distinct advantage over EXX18 electrodes when welding steel sheet materials, whether coated or not.

 

[deanc]

7010 makes an excellent pipeline root pass(open groove). Burn thru the joint and run downhill. Have used 7018 for roots but you will get better results with 7010. Find an old(in the PC sense of course) pipeliner/fitter and ask them.

stanweld refers to the main advantage.