GMAW WELDING

[RKGI]

Dear Experts,

Why Co2 Gas(100% Pure) is preheated in GMAW welding? And what are the effects of not heating the Gas before supplying it to MIG Torch?

 

[Dhurjati Sen]

Dear RKGI,

CO₂ is pre-heated to prevent it from cooling and forming dry ice. Better explained in the link below.

Link

Regards.

DHURJATI SEN
Kolkata, India

 

That is the correct answer, but my question would be 'why weld anything with 100% CO2?'

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[DVWE]

That is the correct answer, but my question would be 'why weld anything with 100% CO2?'

When considering carbon steel and compared to argon based mixes:

Very economical cost-wise.

When set-up properly, welds are visually appealing, and penetration is much more substantial.

The devil is in the details; she also wears prada.

 

[weldstan]

100% CO2 is used extensively in FCAW welding of structural steels and carbon steel pipe due to cost savings.

 

I love CO2 for FCAW, and with the quality of wires available these days there is no reason to pay more for gas.

I was referring to solid wire, based on GMAW mentioned in the OP. GMAW is only FCAW in ASME IX space.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[weldstan]

Agreed, I would not recommend for solid wire GMAW either.

 

[gtaw]

GMAW and FCAW are two different welding processes.

GMAW uses solid bare electrode or metal cored electrodes. FCAW contains flux components inside a tubular electrode. ASME section IX differentiates between the two processes by the electrode product form when qualifying the WPS.

Nonferrous metals are typically welded using an inert shielding gas or a mixture of inert shielding gases when welded with GMAW. Ferrous metals are often welded using CO2 or mixed gases containing some percentage of CO2. The CO2 changes the surface tension to produce a weld with less convexity, i.e., a better profile, and it reduces the tendency to produce undercut when compared to a shielding gas composed of 100% Ar.

Flux cored electrodes can often be used with 100% CO2 or a mixture of CO2 and Ar. Increased amounts of Ar in the gas mix will increase the amount of Mn and Si alloyed with the base metal since less is utilized for the purpose deoxidizing the weld pool.

Best regards - Al

 

IMO, ASME IX should have split FCAW out from GMAW a long time ago.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."