1. Summary of double-sided argon arc welding process
Stainless steel storage tanks typically feature large volumes and thin-walled plates, making them atmospheric containers. Manual stick welding is the most commonly used welding process.
However, this welding process can result in significant spatter, internal stress during welding, and substantial deformation on a single side of the weld, making it difficult to control the quality of the weld.
To solve these problems, argon arc welding can be used. This process eliminates spatter and slag during welding, overcoming the shortcomings of manual electrode welding.
Stainless steel has a strong affinity for oxygen, making it susceptible to oxidation at high temperatures. As a result, one-sided argon arc welding primer often leads to the appearance of “slag weld”, resulting in “poor chromium” in the welding joint area and premature failure in corrosive environments.
Furthermore, one-sided welding is strongly influenced by the groove assembly and can result in welding defects such as incomplete penetration and root melting.
To solve the above defects associated with one-sided argon arc welding and the deformation caused by uneven internal stresses, as well as to increase the qualification rate of NDT film, it is recommended to use the two-sided argon arc welding process. This involves having two people welding both sides of the weld simultaneously.
2. Specific process parameters
1. Weld groove type and size
|
Welding position |
Wall thickness |
Groove type |
Slot Size |
||
|
interval |
truncated edge |
groove angle |
|||
|
Longitudinal welding of the tank wall |
5~8 |
Single V |
1~2 |
1~2 |
65~75 |
|
Tank wall circumferential welding |
5~8 |
Single V |
1~2 |
1~2 |
45~55 |
Note: The groove must be machined before welding. Before welding, all pollutants on the groove surface and within 100 mm must be removed. If necessary, the area should be dried with a dry cloth. Internal weld alignment and misalignment should not exceed 0.5 mm.
2. Welding process parameters
| Welding process | Welding zone | Welding material specification | Energy polarity | Welding current (A) | Welding voltage (V) | Welding speed (mm/min) | Argon flow (L/min) |
| GTAW | Double-sided primer | Φ2.4 | positive pole | 70~100 | 10~12 | 70~110 | 10~14 |
| SMAW | Filler cap | Φ3.2 | negative pole | 90~120 | 20~24 | 60~80 | / |
3. Recommended welding materials
1) Argon must be at least 99.99% pure and a product certificate must be attached to confirm its purity.
2) The recommended welding materials for various austenitic stainless steels are as follows:
| Material name | Welding Wire | Filler 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
Note: This process has been successfully tested by relevant companies.
4. Care when applying this process
1）It is important to strictly control the processing quality of the weld groove and the size of the weld assembly, including clearance and inadequacy.
2）The groove and heat-affected parts must be cleaned and kept dry.
3) The welding process on the main side of welding is the same as single-side argon arc welding. The welder on the auxiliary side must work in coordination with the welder on the main side and maintain the same welding speed. The wire feed speed should be adjusted based on the shape of the weld pool and the welder's experience to ensure that the inner wall weld has an aesthetically pleasing appearance (on the auxiliary side).
4) The specification of the magnetic nozzle of the argon arc welding gun should be selected reasonably based on the thickness of the base metal and the size of the welding groove. The argon flow must be controlled to ensure that the weld pool and heat affected zone are fully protected.
5) Both welders must start and extinguish the arc at the same time. After welding and extinguishing, argon should protect the arc crater for 1-2 minutes.
6) Wall panel welds must be mechanically cleaned before formal welding.
5. Advantages of this process
1）Welding quality is excellent with a high qualification rate in radiographic testing. The welding on the tank wall is also aesthetically pleasing.
2) The welding deformation is minimal and the external weld on the tank wall is well crafted.
3）Work efficiency has improved significantly with the increase of the workforce in the same work area.
4）Construction costs have been reduced.
By eliminating the need for post welding for argon fill protection, post gouging and polishing, argon and labor are saved.
6. Disadvantages of this process
1) The welding process has become more challenging and now requires welders to work together as a team to maintain a consistent welding speed.
2）Weld alignment standards are strict and the weld alignment clearance is closely monitored.
