Low Hydrogen Consumables

One thing that is often overlooked is the amount of total heat induced by the weld and the total heat affected area. The more heat you put into a weld the more the base metal is affected and often that is where you get cracking and distortion. This is why you want to weld with the fewest number of passes and the largest filler rod possible. You will get a much better weld by welding with a single pass of 1/4 inch ER7018 than multiple passes of 1/8 inch. In the real world TIG welding tends to put more heat into the base metal than stick or wire feed welding.

Rich Hurd

This is my original question from before I signed up for a profile. The question comes from a perception by others here that the ER70S-2 is not to be considered of the same quality as the E7018. And that the process in which it is applied makes it an inferior consumable.

I am simply looking for opinions on the subject to further the discussion ! thank you for any input on the subject! SJA

ER 70S-2 is considered as a filler wire for use in TIG and MIG welding processes.

While comparing to E 7018 electrode, you have raised two important points.

1. Mechanical properties apart from its weld metal chemistry &

2. Whether it could be considered equivalent to a low hydrogen consumable as required.

The answer for first query is YES. The deposit or composition of this filler metal is in the same grade as E7018, which is used in SMAW process.

For the second point, we have to analyze few points:

E 7018 is considered to have less than 15 cc of difusible hydrogen level per every 100 gms. of weld deposit. This is due to use of Calcium Carbonate and fluoride.(forms basic slag) in place of rutile used in E 6013 and Cellulosic E 6010 electrodes.

Hence, H₂ level in E 7018 is much lower compared to E 6013 (Rutile) where the dif. H₂ level is more than 15 cc / per every 100 gms of weld deposit and E 6010 (Cellulosic) where the difusible H₂ level is more than 30 cc / per every 100 gms of weld deposit. (See AWS SFA 5.1/ BS 539-1976)).

Now compare it to ER 70 S- family of wires, including ER 70S-2 or S3 or S6 and S-G. In all the types the wire is not coated, but a bare one. Further when used with Argon or Argon + CO₂ or pure CO₂ gas, as shielding during welding (See ASME. Sec. II part C. SFA 5.18).

Due to above facts, the Hydrogen level comes down to barest minimum in the weld deposit, i.e.,the dif. H₂ is less than 3 to 5 cc per 100 gms of weld deposit and does not induce hydrogen or cold cracks in the HAZ or weld area.

And its mechanical properties are also equal to E 7018 or slightly higher when used with CO₂ gas due to carbon enticement during welding.

We can conclude that,

1. ER 70 S-2 / ER 70 S-6 etc., are not inferior to E 7018 in any respect.

2. Both ER 70S-6 and E 7018 minimises the risk of hydrogen induced caracks /cold cracks.

3. ER 70 S-2 with its additional triple deoxidisers in the wire chemistry ( Ti, Al, Zn) gives 100 % Radiographic quality welds and also meets sub zero impacts up to -51⁰C and used for steels up to UTS. 520 N/mm². Compared to it, E 7018 gives CVN impact value only up to -29⁰ C..

4. E 7018 requires pre baking /drying to achieve X-ray quality welds which is not so for ER 70S-2 type wire.

Sridhar.

E=Electrode

R= Rod (GTAW/GMAW)

70 = UTS in KSI

S= Bare solid electrode

2= Chemical composition as per AWS

And this is low hydrogen too. Infact I don't see much difference except the application.

Yes thank you for your input as well, this is in fact the info that I have brought to the attention to others . It seems that I am in fact arguing to an empass, It has been my belief that GTAW had been percieved as the superior application method to most. The deposit or composition of this filler metal is in the same grade as the classic 7018. Im not sure where to go from here other than to shrug it off. The application with a grade 70 electrode should in fact leave you with the same deposit no matter what the procedure used yes ? SJA

Are they aware that ER70S-2 is recommended by AWS for AISI4340 (low alloy CrMo Steel)

Hi

both numbers are telling you the same or similar information but they are used in two completely different applications E7018 is a general low hy rod used for repair welding and plate welding. the other tig rod is used for welding medium high carbon steels and the reason that it is low hy is to cut down on the cracking to do the same thing with a rod you would want 11018 or equiv.

karl

• Low Hydrogen family of filler metals as per ASME code, Section II, Part C, SFA-5.1, Table 1 is only: E7015, E7016, E7018, E7018M, E7028 & E7048.

• For more informatins, see CR4 Thread Welding by 7018 Electrode Without Heating.

The ER family are for GTAW/GMAW. (ER70S-2)

ER70 is AWS listed electrode.

There is no information to suggest that this is a PV.

AWS 70 grade electrode: this is what was given as a mfg requirement for the repair in question... Just the Grade of material to be used, nothing given about procedure. The procedure that was used was left up to the certified welder doing the repair.

It appears as though there is still a little difference of opinion on the subject as I read these posts. It has been my experience that heat build up in your base metal is both better controlled and less an issue with GTAW. Your preheat in both cases reflect prep for these applications. The smaw process, while very reliable process in itself, is being called into question by the advances in both Gmaw and Gtaw as to which is actually the better of the three.

Production is one thing, but actual quality and dependability in a repair is sometimes another . This of course is not to counter any specified standards, but I am seeing a possible lapse in regulations and standards as the quality of alloys and welding consumables advances. Thank you all for your input on the subject, I am enjoying the information / discussion along the way.

Among SMAW, GTAW, GMAW or any of the welding processes, it is not the question - which is better .

The use of the process is need based, depending upon the material, end application, structural- sheetmetal or plate, pressure joint or has static flow, position of welding etc.

For example, for welding SS, Alloy steel piping we prefer GTAW for root application for better finish and defect free joints followed by GTAW, SMAW or GMAW for filler / cap passes. For CS, it could be SMAW all the way or GTAW followed by SMAW or GMAW.

Again, for AS pipes, we can not use GMAW even for F/C passes. There FCAW replaces GMAW due to additions of Cr, Mo, Ni elements inthe core flux.

GMAW can not be used for root run because of process limitations. We can not get consistancy for its Radiographic quality welds. Here GTAW & SMAW are the only alternatatives.

Similarly for repair welding GTAW is better than SMAW as the subsequent weld metal layers gets normalised due to constant heat input and grain growth could be avoided. It helps to get better impact properties compared to use of SMAW for repair welds.

Again to counter heat input, GMAW better compared to other two processes because of its higher travel speeds. But limitation is with its wire size. Even 1.20 mm can not give consistance results in OH postion. 1.60 mm size cannot be used for vertical postion.

Similarly we prefer GMAW (MIG) in place of GTAW for AL plate welding due its easiness of the operation and less defects & better distortion control.

That way every process has its own advantages and limitations. In the present day fabrication we have to look at the Techno-commercial aspects of the process and at some places ( SS, Cupro nickel pipes) small bore tubes/pipes, we have to live with GTAW inspite of its high cost factor.

Sridhar.

Most likely, depending on what you are repairing, it will be GTAW or GMAW.There are definite advantages of the GMAW and GTAW in certain applications.

GTAW: low heat, best for thin section, weld quality and aestetics is highest. The grains are refined during the welding to have far better strength than other types of welds (even with similar electrodes), at the cost of loss of toughness (the charpy is typically lower)

GMAW: fastest (may reach upto 3 to 4 times of SMAW), with the added advantage of continuous wire feed. Easy to weld. Very sensitive to air flow (unless you use Flux cored wire), no cleaning, no slag entrapment in welds,...