Compared with ordinary carbon steel, the welding process of stainless steel and the technical requirements for welders should be stricter, and the color of the weld should be the best.
Let me share my personal views and opinions with you.
Through welding experiment verification (manual welding, automatic welding, argon arc welding), welds can be divided into:
1. Silver white
2. Golden yellow
3. Five colors (golden yellow+blue);
5. Dark blue;
6. Gray black (with luster);
7. Dead black ash.
The quality of weld color is inseparable from the welding process parameters and the technical level of welders.
The main problems are:
1. Cleanliness of groove before welding;
2. Purity and flow of shielding gas;
3. Size of welding current;
4. Quality of welding materials;
5. Number and layers of welds;
6. Welding speed;
7. Control of interlayer temperature;
8. Control of heat input.
When the welding process conditions are met, the weld should be silver white, and the physical and chemical values of the weld are also the best.
For automatic submerged arc welding equipment, welding parameters and heat input shall be strictly controlled.
In fact, the different thickness of each weldment makes the welding current, voltage, welding speed and wire feeding speed match reasonably.
In fact, welding is like acting. The leading actor and the supporting role must achieve 100% tacit understanding to achieve the highest effect.
For example, the welding parameters of workpieces with the same material and different wall thicknesses must be different.
If the parameters are too large, intergranular corrosion will occur, resulting in chromium depletion.
In severe cases, cracks will occur, and the color will be ugly.
According to experience, the above silvery white and yellow quality are acceptable, and silvery white is the best.
The multicolored welds have partially produced intergranular corrosion and poor chromium, which is the so-called chromium carbide, making stainless steel lose its stainless and corrosion resistance.
The color after blue and dark blue has no way to talk about the welding quality.
In actual work, welding process parameters cannot be rigidly applied.
Due to different ambient temperature, weldment thickness, weldment size and welding speed, applicable parameters are also different.
When welding large weldments with large wall thickness, of course, the current should be higher.
Related reading: Wire Feeding Speed and Welding Current
If necessary, multi-layer and multi pass welding should be used and the interpass temperature should be controlled.
Otherwise, the appearance quality of the weld may be very beautiful, and the interior cannot meet the real welding quality requirements.
When multi-layer and multi pass welding is adopted, the lower weld bead welding can be carried out after the previous weld bead is cooled, so that the effect will be better.
During automatic welding, the welding speed and wire feeding speed must also be matched with the corresponding current and voltage.
For the same weldment, the best welding effect must be achieved.
If the welding speed changes, the current and voltage or the speed of the wire feeder must be changed.
The faster the welding speed is, the greater the voltage is, and the faster the wire feeding speed is.
However, considering the metal melting and welding quality, an optimal welding speed, optimal current, voltage and optimal heat input should be selected to ensure the weld quality.
When argon arc welding is adopted, the following points shall be noted:
1. The cleaning before welding must be carried out in strict accordance with the welding procedure specification;
2. Argon must meet the requirements for welding stainless steel;
3. Properly increase the nozzle diameter to ensure the protection effect;
4. Adopt small current short arc rocker for fast welding;
5. Remove the welding gun after the arc is connected and the molten pool is completely cooled;
6. Strictly control the heat input. Secondly, the working environment is also an important link.
The air and dust in the welding environment will affect the cleanliness of the surface of the weldment, the technical level of the welder, and the quality of the welding wire.