Porosity due to rust

Date 06-15-2001 13:13

I am repairing a truck cab. Although I am removing metal and wire brushing to eliminate as much rust as possible, there are some areas that have rust on the other side of the original sheetmetal. Cutting it all back is not always practical, particularly where there is a hard to duplicate shape. When I weld into these areas using MIG, E70s with a C25 shielding gas, I sometimes get a bubble in the center of the weld puddle. Would I get better results using a double-shielded flux core wire?

By pipewelder_1999 (****)

Date 06-15-2001 13:34

I thisnk some of the ER70 wires are better than others for welding on surfaces with contamination. I'm not sure which ones they are but here is some sales data from esab. These all are better than ER70S 3 for rust.

AWS Class ER70S-2
Code and Specification Data:
AWS A5.18, ASME SFA 5.18
Military - MIL 70S-2, MIL-E-23765/1
ABS - ER70S-2
CWB-CSA W48.4-M, ER480S-2

Description:
Spoolarc 65 is a triple deoxidized (aluminum, titanium, zirconium) welding wire designed for welding over rust and mill scale. The less fluid weld puddle of Spoolarc 65 makes it easy to control when used out of position.

Description:
Spoolarc 85 contains more manganese and silicon for greater deoxidation capability when compared to ER70S-3 wire. The higher level of deoxidizers provides for better rust and scale tolerance and it also improves bead wetting.

Spoolarc 85 is typically used for applications including welding of farm machinery, material handling equipment and piping..

AWS Class ER70S-6
Code and Specification Data: AWS A5.18, ASME SFA 5.18
Military - MIL 70S-6, MIL-E-23765/1
ABS - ER70S-6
Lloyds - 3SA, 3YSA
CWB-CSA W48.4-M, ER40S-6

Description:
Spoolarc 86 contains higher levels of manganese and silicon than the other standard grades of MIG wire. This wire features excellent tolerance of rust and scale, produces the highest deposit strength of all the carbon steel MIG wires.

Spoolarc 86 is used for butt and fillet welding of sheet and plate of a variety of thickness. Applications include general carbon steel fabrication.

Also be sure that you are getting adequate gas coverage at the joint and that no leaks exist on your gas hoses etc.

Here is a link to some information on solid wires from esab. Other manufacturers have similar data on the internet but I like esabs best since technical data such as welding parameters and deposition rates are available.

http://www.esab.com/ESAB/Category.cfm?&DID=8&User_ID=63502&st=6327&st2=43192463&st3=-31399788&CATID=22

I hope it works out for you.

Gerald Austin

Weldinginspectionsvcs.com