1、 Preparation before welding

1. Groove processing

Use alumina grinding wheel to polish the groove and avoid overheating and discoloration of the base material.

2. Surface cleaning

Mechanical polishing and acetone cleaning are required within 50mm on both sides of the groove.

The welding wire needs to be wiped with acetone and stored in a dedicated box, and the operator should wear clean gloves.

2、 Welding Process Specification

1. Welding method: GTAW is recommended, and ERTi-2 welding wire is used.

2. Parameter control

Small line energy, interlayer temperature ≤ 200 ℃.

After arc interruption, argon filling should be delayed until the temperature is below 300 ℃.

3. Gas protection

The main protective gas is 99.995% argon gas, and the back protective flow rate is 8-12L/min.

When the pipe diameter is ≥ 450mm, partial argon filling is required, and when the pipe diameter is smaller, argon filling is required as a whole.

3、 Post weld treatment

1. Testing requirements

Radiographic testing and eddy current testing.

The microhardness gradient should be ≤ 50HV, and there should be no cracks in the bending test.

2. Defect prevention and control

Pore prevention: Vacuum baking before welding, using He Ar mixed gas.

4、 Special working condition handling

Heterogeneous metal welding: Titanium steel joints require a tantalum intermediate layer to reduce heat input by 30%.

Deep sea repair: simulated welding in high-pressure environment, followed by vacuum drying after welding.