Re: [MW:27824] Aluminum MIG Welding - failed PQR

Cleaning prior to welding

To achieve low porosity levels for x-ray quality welds, it is important to understand the methods available for the effective removal of hydrocarbons and moisture from the weld area, and to incorporate the appropriate methods into the welding procedure. If these contaminants are present in the weld area during welding, they will produce hydrogen and significantly contribute to porosity problems.

When designing welding procedures intended to produce low levels of porosity, it is important to incorporate degreasing and oxide removal. Typically, you can achieve this through a combination of chemical cleaning and/or the use of solvents to remove hydrocarbons followed by stainless steel wire brushing to remove contaminated aluminum oxide.

so what is this methods in your point of view? 

Regards,

H.A 

On Tue, May 8, 2018 at 1:00 PM, George Dilintas <dilintas@gmail.com> wrote:

http://www.esabna.com/us/en/education/blog/porosity-problems-with-5086-5356-alloys.cfm

2018-05-08 9:11 GMT+03:00 'c sridhar' via Materials & Welding <materials-welding@googlegroups.com>:

Your photos clearly shows endless amount pores in the weld

The main cause for porosity in aluminum is hydrogen, which       has very high solubility in molten aluminum but very low            solubility in solid. Hydrogen gas is therefore evolved as the weld   pool solidifies. If the cooling rate is too high, the gas remains in      the metal in the form of porosity. Thus, any compound containing hydrogen and contaminating the filler wire or work surface can cause porosity.

Oil, moisture or other contaminants may be present on the        filler wire. In addition, the oxide layer of aluminum tends to get    hydrated and improper cleaning of the oxide layer immediately preceding welding could be a cause for porosity. Ensuring that     the plate is clean before welding and switching to clean, high   quality electrodes will reduce the likelihood of forming porosity.

The amount of porosity depends on how fast the weld pool  solidifies. Increasing the welding current and/or decreasing          the travel speed will increase the heat input, and help retard the cooling rate allowing gases to escape from the weld pool and  thereby reducing the risk of porosity.

Filler wires should ideally be kept in their packaging until      needed; wire that is left out ion open workshop conditions will absorb moisture into its oxide layer. It is advisable when welding aluminum to wipe each wire prior to use with a clean cloth dipped in acetone.

Pre heat the weld and HAZ area to mimnimum150 deg. C to eliminate hydrogen pores. Once you overcome it, the tests
will pass through.

Sridhar.

On Monday, 7 May, 2018, 4:16:16 PM IST, Hani Al Masry <hanyonalfy@gmail.com> wrote:

Dear experts 

regarding A/M Subject kindly advice why the PQR Test had been failed two times even this WPS/PQR Approved before and we just tried to copy it 

all welders 2 times failed in root bend / tension some times not reach 250 MPA as required  (2 root bend + 2 root face + 2 tensile testing are required)

the lab said first time there are porosity
and inclusions but even 2nd test was failed  (attached photos for your reference) 

BASE METAL       :  AA 5083 H 321  

FILLER METAL       :  ER 5356  

Joint Preparation: -              Single V CPJ

Weld Layer

WELDING PROCESS

WELDING POSITION / DIRECTION

ELECTRODE(S)

GAS SHIELD

GAS FLOW RATE lit/min.

AMPS

VOLTS

WELDING SPEED mm./min.

FLUX

WFS M/Min.

Mode of Metal transfer for MAW

SIZE mm

TRADE NAME

POLARITY

1

GMAW

3G

1.2

AUTO ROD 5356

DCEP

ARGON 99.99%

15-25

120-180

18-26

12-20

NA

8.5

Pulse transfer

2

GMAW

3G

1.2

AUTO ROD 5356

DCEP

ARGON 99.99%

15-25

120-180

18-26

120 - 140

NA

8.5

Pulse transfer

Back weld

GMAW

3G

1.2

AUTO ROD 5356

DCEP

ARGON 99.99%

15-25

120-180

18-26

100 - 110

NA

8.5

Pulse transfer

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Dr. Georgios Dilintas,

Dipl. Ing. In Aeronautic and Space Engineering

Ph.D in Mechanics of Solids - Computational Mechanics

A.I.S, A.N.I, IRCA Lead Auditor

Welding, Stress Analysis, Corrosion, QA/QC, Failure Analysis, Risk Analysis

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