Home  /  News

What precautions should be paid attention to when welding stainless steel tubes?

Aug. 27, 2019

Matters needing be paid attention to whenn welding Stainless steel pipe:

1. Adopt the power source with vertical external characteristics, and adopt the positive polarity (welding wire to negative electrode) for dc.

2. Generally suitable for the welding of thin plates under 6mm, with the characteristics of beautiful welding seam formation and small welding deformation.

3. The shielding gas is argon with a purity of 99.99%. When the welding current is 50~50A, the argon flow is 8~0L/min, and when the current is 50~250A, the argon flow is 2~5L/min.

4. The length of the tungsten electrode protruding from the gas nozzle is 4~5mm, which is better. It is 2~3mm in areas with poor shielding such as fillet welding, and 5~6mm in places with deep grooves.

5. Welded steel pipes factory shares that in order to prevent the appearance of welding holes, rust and oil stains must be cleaned on the welding parts.

6. The arc length of welding is 2~4mm for common steel, and 3mm for stainless steel, but too long is not good for protection.

7. Gas protection shall be implemented on the back of the bottom pass to prevent oxidation of the back of the bottom pass during butt laying.

Stainless Steel Tee

Stainless Steel Tee

8. In order to protect the welding pool with argon gas and facilitate welding operation, the Angle between the center line of tungsten pole and the workpiece at the welding place should be maintained at 80~85°, and the included Angle between the filler wire and the surface of the workpiece should be as small as possible, usually around 0°.

9. Windbreak and ventilation. In windy areas, take precautions to block the net, and take proper ventilation measures indoors. (1) to control the size of stainless steel pipe fitting joint groove, thoroughly clean the welding root, choose the appropriate welding current and welding speed. For example, single-side welding double-sided formed butt joint, the group of clearance should be equal to the diameter of the electrode, the height of the blunt edge is about 1/2 of the diameter of the electrode.

(2) in the stainless steel pipe fitting welding quality standard, double-side welding or single-side welding with backing plate is not allowed to have incomplete welding defects. For one side welding without backing plate, the allowable defect of lack of penetration is related to the importance of weld seam. Non-penetration on one side is not allowed for important welds; For more important welds, the allowable penetration depth shall not exceed 10% to 15% of the base material thickness (depending on the weld grade), and shall not exceed 2M, and the length of non-penetration shall not exceed the total slag length allowed for the welds of the same grade; Generally, the depth of the final penetration of the weld shall be less than 20% of the thickness of the base material, and no more than 3mm, and the length shall be less than the allowable edge-clamping total length.

(3) in order to prevent the inclusion of other slag, should strictly clean up the base material groove of stainless steel pipe fittings and the nearby surface of dirt, oxidation slag, thoroughly clean the slag of the previous welding pass.

(4) in order to make the stainless steel pipe slag fully surfaced, to choose the medium welding current, so that the pool to reach a certain temperature, prevent the weld metal cooling too fast.

(5) master the operation technology proficiently, keep the molten metal clear at all times, and promote the good separation of slag and molten iron.

(6) neutral flame is used for gas welding, and welding wire is used to remove slag from the molten pool during operation.