How to deal with the blackening of the welds in 304 stainless steel pipes

Pre-delivery of gas 

Before welding, supply the gas first, then proceed with the welding of the workpiece to ensure that the argon gas protects the welding area and prevents oxidation. 

2. Delayed gas supply 

After attaching the welding gun, do not remove the gun nozzle from the welding area of the workpiece. Continue to supply gas to ensure that the weld seam and the surrounding areas of the workpiece are not oxidized by high temperature. 

3. Control of the welding gun switch 

For 304 stainless steel pipes, during welding, it is not advisable to use a high current for long periods of continuous welding. Instead, more spot welding should be employed. Excessive current and slow welding speed can both cause the weld seam to turn black. 

Therefore, when welding, the current should be selected based on the thickness of the pipe material, the tungsten needle should be chosen according to the current, the porcelain nozzle should be selected based on the tungsten needle, and the gas flow rate should be chosen according to the porcelain nozzle. The welding speed should be fast and the technique should be precise. 

4. Techniques 

The distance between the tip of the tungsten needle and the welding piece: when the tungsten needle touches the welding piece, the weld becomes black; if the tungsten needle is too far away from the welding piece, the weld also turns black. 

The main reason for this is to ensure the stability and strength of the welding arc during the welding process. 

5. Selection of Tungsten Needles 

① Try to select tungsten needles that have yellow and white markings. The quality of the tungsten needles should be reliable. 

② During use, the tungsten needle must be kept sharp. The reason for this is that if the tungsten needle becomes blunt, the current cannot be concentrated, making it difficult to maintain the stability of the electric arc during welding and causing it to spread. 

6. Control of the molten pool temperature at the solder joints 

It is related to the welding operator's technique and the speed of the welding gun. The temperature of the molten pool is closely related to the welding of the component and the current size. However, ensuring that there is no oxidation before cooling is related to the speed of the welding gun. While welding, it is necessary to cool continuously. The speed of the welding gun must ensure that the argon gas can protect the previous molten pool and prevent it from being oxidized by high temperature. 

7. Welding wire material 

The welding wire material should be selected based on 304 stainless steel pipes to ensure uniformity in material and avoid blackening of the welds due to material differences. 

8. Solder joints and protection on the backside 

Ar gas can be supplied to the back of the weldment for protection, or a protective coating can be applied.