Jose,
you're from Argentina, so you'll understand what I'll tell you.
Back in 1972, I was in charge of the construction of the Gaviotas natural gas compressing station located in the southeast corner of La Pampa province in Argentina. Our client was Gas del Estado, which no longer exists because it's been privatized.
Well, the client requested us to weld the API 5L X52 12,7 mm wall thickness (little difference with X60 15 mm) with E 6010 for the root pass and E 7018 for the subsequent ones.
So, the type of welding you're talking about has been known for the past 40 years. It's possible that the compressing is still there, working fine.
Giovanni S. Crisi
Sao Paulo - Brazil
According to ASME Section IX, API 5L Grade X60 has a minimum tensile strength of 75ksi, and the E7018 only has a minimum tensile strength of 70ksi. You should be using the next higher tensile strength consumables to match the strength of the base metal. You might consider E8018-C3. There are also higher tensile strength E7010 and E8010 available.