American Welding Society Forum
I am trying to weld HSLA steels with 100% co2 shielding with GMAW process.
when we use 100% CO2 shielding, what Metallurgical changes comes in weld as compared to 75% Ar- 25% CO2 mixture?
Pl give me some information about this.
Welcome to the Forum Mohammed!
You may get many responses. None of them can be definitive without more information from you.
The exact base metals and carbon content would be important to know.
Thickness of base metals?
Filler wire to be used?
Filler wire diameter?
Wire feed speed/Amperage for the welds?
If you are making the change to C02 in order to save money, you probably will fail, due to other costs associated with the change, including spatter, tighter tolerances for fitup that are required and more.
On the other hand, in parts of the world where argon is unavailable or prohibitive, GMAW technology has adapted to do high volume automation of think steels and HSLA with pretty good success.
Say more about your project.
Sorry for being too late.
I am welding HY-80 Quench and tempered steels of 5mm thickness and 20 mm thickness with single Vee weld configuration.
The carbon percentage is 0.08 - 0.11 %
Filler wire is of ER70S for gmaw of 1.2 mm diameter.
I am using Amperage in range of 100-150 A & voltage 18-21 V.
For welding the 5mm plate the welders are saying they are getting stucked becasue if they keep high values of current Burn through is occuring in root & at lower currents proper fusion is not coming.
I am using Lincoln 450M power Source.
This is a link to some data on ER70S-6 mechanicals when various shield gasses are introduced as well as post weld stress relieved vs as welded conditions
The Lincoln Powerwave 455M has some built-in GMAWP parameters that can be useful for materials in the 5mm range. However they would require a 2 part gas mix, preferably 90/10 Ar/Co2 or 98/2 Ar/Oxygen.
While 5mm (3/16" for Yankees) is a reasonable thickness for short circuiting GMAW, it is also a reasonable thickness for Spray transfer or Pulsed spray transfer on fillets. Spray transfer offers much greater penetration and if fit-up is reasonably good, there should be zero burn thru on 5mm fillets.
HY-80 welded with ER70S filler metal? Do you know what the approx yield and tensile strength for HY-80 is???
Read this article and then tell me that you still think ER70S is the correct filler metal for welding HY-80 steel:http://www.thefabricator.com/article/consumables/from-a-to-w
And then surprising enough, read this page form Ed Craig's Weld Reality that shows how sometimes and especially considering the thickness of the base metal as well as other factors, there are some situations where an E70S 3-6 Filler metal can be used so that the need for preheating the base metal isn't required... Now this isn't the norm because most HY-80 plate is thicker than 12mm when applied to shipbuilding for example.. I know this because I have welded miles of HY-80 and 100 many moons ago... But I'm presuming that you're not doing this type of fabrication so I must consider the circumstances that would be present in your situation...
Under matching really isn't desirable with these types of steel however there are exceptions to the rule as in your case...
I'm curious as to why you're not using an HSLA- 80 or 100 steel instead... I mention this because the HSLA steels were initially developed so that preheat and strict controls regarding heat input, and these steels matched the yield and tensile strengths that HY-80 and 100 so it's really a win-win alternative...
Here's a more technical paper regarding the effects of welding processes on the mechanical properties
of HY 80 steel weldments:http://www.ewp.rpi.edu/hartford/~ernesto/F2014/MPT/MaterialsforStudents/Patella/Yayla2007-WeldingHY80.pdf
I also have a bridge to sell you if you're interested!
P.S. Hey Ken! Does that image look familiar to you in this article??? He's certainly not a pipefitter even though they still have to fit.
To be honest I would not be as concerned about gas induced metallurgical changes in the weld metal as I am heat induced metallurgical changes in the HAZ. The weld metal is rarely the weak link. Think about how and why these materials are made. How they get an HS from an LA.
Using straight CO2 and welding parameters similar to that used for spray transfer will produce globular transfer. The globular transfer can be characterized as producing a very fluid weld pool, deep penetration, high heat input, and limits the welding positions to flat grooves and fillets and horizontal fillets. One draw back is the amount of spatter that is produced. Depending on the application, the spatter may be a problem.
The draw back is that the welders will attempt to reduce the arc voltage and wire feed speed to make life easier for them. The result is the welders will be in the short circuiting transfer mode if someone doesn't monitor the welding parameters closely.
Powered by mwForum 2.29.2 © 1999-2013 Markus Wichitill