Double Side Argon Arc Welding Process for Stainless Steel Tank

1. Summary of double-sided argon arc welding process

Stainless steel storage tanks are generally atmospheric vessels with large volume and thin design wall plates.

The commonly used welding process is manual electrode welding.

During welding, the spatter is large, the welding internal stress is large, and the single side welding deformation is large.

It is difficult to control the welding quality.

Argon arc welding can just overcome the above shortcomings.

There is no spatter and slag in the welding process.

Double Side Argon Arc Welding Process for Stainless Steel Tank 1

However, due to the strong oxygen affinity of stainless steel, it is easy to oxidize at high temperature, and the “slag weld” is easy to appear in the single-sided argon arc welding primer, leading to “poor chromium” in the welding joint area and premature failure in the corrosive medium.

Moreover, single side welding is greatly affected by groove assembly, and is prone to welding defects such as incomplete penetration and root fusion.

In order to overcome the above defects of single-sided argon arc welding and the deformation caused by uneven internal stress of single-sided argon arc welding, and improve the qualification rate of NDT film, it is recommended to use two people to weld both sides of the weld at the same time, that is, double-sided argon arc welding process.

2. Specific process parameters

1. Weld groove type and size

Welding position

Wall thickness

Groove type

Groove size

interval

truncated edge

groove angle

 

 

Longitudinal weld of tank wall

5~8

Single V

1~2

1~2

65~75

Tank wall circumferential weld

5~8

Single V

1~2

1~2

45~55

Note: The groove shall be machined. Before welding, the pollutants on the groove surface and within 100mm around must be cleaned up.

If necessary, dry it with a dry rag. The alignment and misalignment of the inner weld shall not exceed 0.5mm.

2. Welding process parameters

Welding processWelding zoneWelding material specificationPower polarityWelding current (A)Welding voltage (V)Welding speed (mm/min)Argon flow (L/min)
GTAWDouble sided primingΦ2.4positive pole70~10010~1270~11010~14
SMAWFilling coverΦ3.2negative pole90~12020~2460~80/

3. Recommended Welding Materials

1) Argon should be 99.99% pure argon with product certificate attached.

2) For different austenitic stainless steels, the recommended welding materials are as follows

Material nameWelding wireFiller rod
0Cr18Ni9(304)ER308 (H0Cr21Ni10)A102
00Cr19Ni10(304L)ER308L (H00Cr21Ni10)A002
0Cr17Ni12Mo2(316)ER316 (H0Cr19Ni12Mo2)A202
00Cr17Ni14Mo2(316L)ER316L (H00Cr19Ni12Mo2)A022
0Cr18Ni10Ti(321)ER347 (H0Cr21Ni10Ti)A132
1Cr18Ni9Ti(321HTB)ER347 (H0Cr21Ni10Ti)A132

Note: Welding materials must have quality certificates or certificates with red seals.

3. Welding diagram

Double Side Argon Arc Welding Process for Stainless Steel Tank 2
Double Side Argon Arc Welding Process for Stainless Steel Tank 3
Double Side Argon Arc Welding Process for Stainless Steel Tank 4

Note: This process has been successfully piloted by relevant companies.

4. Precautions for the application of this process

1. Strictly control the processing quality of the weld groove and weld assembly size (clearance, unfitness, etc.).

2. The groove and heat-affected parts must be cleaned and kept dry.

3. The welding process on the main welding side is the same as that of single-sided argon arc welding.

The welder on the auxiliary side must cooperate with the welder on the main welding side and maintain the same welding speed.

The wire feeding speed depends on the shape of the weld pool and the welder’s experience to ensure that the inner wall weld is beautiful (auxiliary side).

4. The specification of magnetic nozzle of argon arc welding gun shall be reasonably selected according to the thickness of base metal and the size of weld groove, and the argon flow shall be controlled to ensure that the weld pool and heat affected zone are fully protected.

5. Two welders start and extinguish the arc at the same time, and argon will protect the arc crater for 1~2min after welding and extinguishment.

6. The wall panel tack welds must be mechanically cleaned before formal welding.

5. Advantages of this process

1. The welding quality is good, the qualification rate of radiographic is high, and the weld in the tank wall is beautiful.

2. The welding deformation is small, and the external weld of the tank wall is well-formed.

3. The work efficiency has been significantly improved (the labor force in the same working face has been increased).

4. Reduce construction costs.

It is unnecessary to weld the back for argon filling protection and back gouging and polishing, saving argon and labor.

6. Disadvantages of this process

1. The difficulty of welding is increased. Each group of welders is required to cooperate with each other to maintain the same welding speed.

2. The requirements for weld alignment are high, and the weld alignment clearance is strictly controlled.

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