70S-2 vs 70S-6

This is a battle I have pesonally fought several times while I was welding pipe.  The 70 S 6 wire is superior to the S 2 wire in regards to the actual welding.  The S6 wire is cleaner and flows much better, very similar to stainless steel.  The wall that I always hit was that the QC people were not capable of interpreting the code well enough accept the possibility that S6 did conform to the WPS.  According to the QW-442 A-numbers the Mn is listed in the Ferrous Weld Metal Analysis as 1.60.  This should mean that the 70-S 6 wire is acceptable as long as its Mn is 1.60 or less.  The actual certs on the wire used should show this.  If this argument is a reality then is means that one can list the A number for 70 S 6 wire as a A-1.  Qw 404.5 in the edition  states: "The weld composition may be determined by any of the following: (b) For SMAW, GTAW, and PAW-from the chemical analysis of the weld deposit prepared according to the filler metal specification, or from the chemical composition as reported either in the filler metal specification or the manufature's or supplier's certificate of compliance.

The reason to use 70 S 6 over 70 S 2 in my opinion as a welder and a CWI is for the quality of the weld.  In many projects that I was on the reject rate for welds being radiographed were higher while using the 70 S 2 wire.  When economics and schedules became in jepordy the management listened to the welders and qualified personel and switched to the 70 S 6 wire.  The results were improved welds with fewer rejects.

The key thing that I use when using 70 S 6 is the actual wire certs..  Keep the Mn at or under 1.6 and keep the Si at or under 1.0.   This has always been acceptable in situations that I encountered.

Good luck on this issue

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What is the difference between ER70S-2 and ER70S-6 Tig wire?

Type ER70S-2 is the most popular Tig rod for welding carbon and low alloy steels...It is a triple deoxidized steel welding wire used for both tig and mig welding applications.

Type ER70S-6 is a very popular mig welding wire that can also be purchased in cut lengths and used for Tig welding.

The differences are very subtle so that is what we are going to dive into in this video

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chemical composition of ER70S-2

AWS Chemical Composition Requirements...
C = 0.07 max    Ni = 0.15 max    Cu = 0.50 max
Mn = 0.90 &#; 1.40    Cr = 0.15 max    Ti = 0.05 &#; 0.15
Si = 0.40 &#; 0.70    Mo = 0.15 max    Zr = 0.02 &#; 0.12
P = 0.025 max    V = 0.03 max    Al = 0.05 &#; 0.15
S = 0.035 max

ER70S-6 Tig wire

Type ER70S-6 is a wire contains higher levels of Deoxidizers Manganese and Silicon (Mn & Si) compared to other carbon steel wires. The higher level of silicon can make this filler metal sightly more fluid than others and seems to float oxides to the surface...as seen in the photo below

AWS Chemical Composition Requirements...

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C = 0.06 &#; 0.15    Ni = 0.15 max
Mn = 1.40 &#; 1.85    Cr = 0.15 max
Si = 0.80 &#; 1.15    Mo = 0.15 max
P = 0.025 max    V = 0.03 max
S = 0.035 max    Cu = 0.50 max

so while er70s-6 does contain higher levels of silicon and manganese, er70s-2 contains other deoxidizers like titanium, zirconium, and aluminum

So which one is better?

For this video, I welded on hot rolled mill scale plates at 150 amps using both ER70S-2 and ER70S-6 filler rods.

Some of the plates were cleaned pretty well, and some were not&#;.and some were barely cleaned at all.
these were A36 structural steel plates that I was tack welding backing straps on for future videos.

( thank you to Triangle Engineering for donating the plates)

After welding with both ER70S2 and ER70S6 in several different scenarios, I have to say the differences between the two rods are very subtle.

ER70S-2 and ER70S-6
observations ...

• for some of the joints I welded for this video, there was very little detectable difference in the way the puddle flowed, or in the final weld appearance.
• when metal was properly cleaned, and when I was not penetrating thru exposing the puddle to oxides, there was very little difference in the way these two rods welded.
• the area where i did see a distinct difference was when I was penetrating thru the back side without a purge.
• when welding .048&#; (1.2mm) thick cold rolled steel, without argon on the back side, there was a noticeable difference in the final appearance of the back side&#;the penetration side of the weld.
• When welding over hot rolled steel that had not been cleaned, the ER70S-2 actually had a cleaner final weld appearance&#;.which is something I did not expect.

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