Why Can’t Stainless Steel Be Welded With Carbon Steel Electrode?

Welding is a process in which the material of the workpiece to be welded (the same or different) is heated or pressurized or both, and whether to use filler materials is selected to make the material of the workpiece achieve the combination between atoms and form a permanent connection.

Related reading: The Ultimate Guide to Welding

What are the key points and precautions for stainless steel welding?

Why Can’t Stainless Steel Be Welded With Carbon Steel Electrode? 1

What electrode is used for welding stainless steel

Stainless steel welding rods can be divided into chromium stainless steel welding rods and chromium nickel stainless steel welding rods.

All welding rods meeting the national standard shall be examined according to the national standard GB/T983-2012.

Chromium stainless steel has certain corrosion resistance (oxidizing acid, organic acid, cavitation) and heat resistance, and is usually selected as equipment and materials for power plants, chemicals, petroleum, etc.

However, the weldability of chrome stainless steel is poor in general, so attention should be paid to the welding process, heat treatment conditions and the selection of appropriate welding electrodes.

Chromium nickel stainless steel electrode has good corrosion resistance and oxidation resistance, and is widely used in chemical, fertilizer and petroleum fields.

In order to prevent intergranular corrosion due to heating, the welding current should not be too large, about 20% smaller than that of carbon steel electrode, the arc should not be too long, and the interlayer should be cooled quickly, so it is better to narrow the weld bead.

Key points and precautions for stainless steel welding

1. The power supply with vertical external characteristics shall be adopted, and the positive polarity shall be adopted in DC (the welding wire shall be connected to the negative electrode)

1. It is generally suitable for the welding of thin plates less than 6mm, with beautiful weld formation and small welding deformation.

2. The shielding gas is argon with a purity of 99.99%.

When the welding current is 50~150A, the argon flow is 8~10L/min;

When the current is 150~250A, the argon flow is 12~15L/min.

3. The length of tungsten electrode protruding from the gas nozzle shall be 4-5mm.

2~3mm in places with poor shielding such as fillet welding, 5~6mm in places with deep grooves, and the distance from the nozzle to the work is generally not more than 15mm.

4. In order to prevent the occurrence of welding pores, the welding parts must be cleaned up if there are rust, oil stains, etc.

5. When welding ordinary steel, the length of welding arc should be 2~4mm;

When welding stainless steel, 1~3mm is better, and if it is too long, the protection effect is not good.

6. During butt priming, gas protection is also required on the back of the bottom weld bead to prevent oxidation.

7. In order to protect the welding pool well with argon and facilitate welding operation, the center line of tungsten electrode and the workpiece at the welding point should generally be kept at an angle of 80 °~85 °, and the angle between the filler wire and the workpiece surface should be as small as possible, generally about 10 °.

8. Wind protection and ventilation.

In windy places, please take measures to block the net, and take appropriate ventilation measures indoors.

2. Key points and precautions of stainless steel MIG welding

1. The flat welding power supply is adopted, and the reverse polarity is adopted in DC (the welding wire is connected to the positive electrode)

2. Generally, pure argon (99.99% purity) or Ar+2% O2 is used, and the flow rate is 20~25L/min.

3. Arc length

MIG welding of stainless steel is generally conducted under the condition of spray transfer, and the voltage should be adjusted to the arc length of 4~6mm.

4. Windproof.

MIG welding is easy to be affected by wind, and air holes are easy to occur in windy places, so wind protection measures should be taken in places with wind speed above 0.5m/s.

Related reading: MIG vs TIG Welding

3. Key points and precautions for stainless steel flux cored wire welding

1. The flat welding power supply is adopted, and the reverse polarity is adopted in DC welding.

The general CO2 welding machine can be used for welding, but the pressure of the wire feeder should be slightly adjusted.

2. The protective gas is generally carbon dioxide, and the gas flow rate is 20~25L/min.

3. The distance between the welding nozzle and the workpiece should be 15~25mm.

4. Generally, the dry extension length is about 15mm when the welding current is below 250A, and about 20~25mm when the welding current is above 250A.

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