What welding rod is used for welding stainless steel? How to weld stainless steel?

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Welding is a process in which the materials of the workpieces to be joined (either the same type or different types) are brought together through heating or pressure, or both, with or without the use of filler material, thereby achieving atomic-level bonding between the materials and forming a permanent connection. So, what are the key points and precautions for welding stainless steel? What kind of electrodes should be used for welding stainless steel? Stainless steel electrodes can be divided into chromium stainless steel electrodes and chromium-nickel stainless steel electrodes; those that meet national standards are evaluated in accordance with the national standard GB/T983-2012. Chromium stainless steel possesses certain corrosion resistance (against oxidizing acids, organic acids, and cavitation), as well as heat and corrosion resistance. It is commonly chosen as material for equipment in power plants, the chemical industry, oil, and other sectors. However, chromium stainless steel generally has poor weldability, so attention should be paid to the welding process, heat treatment conditions, and the selection of appropriate welding electrodes. Chromium-nickel stainless steel welding electrodes possess excellent corrosion resistance and oxidation resistance, and are widely used in the chemical, fertilizer, petroleum, and medical equipment manufacturing industries. To prevent intergranular corrosion caused by heating, the welding current should not be too high; it should be about 20% lower than that used with carbon steel electrodes. The arc length should also be kept short, rapid cooling between layers is necessary, and narrow weld beads are preferred. Key points and precautions for stainless steel welding. 1. Use a power source with a vertical external characteristic; when using DC, set it to positive polarity (the welding wire is connected to the negative pole). 1. This method is generally suitable for welding thin plates under 6 mm in thickness. It results in aesthetically pleasing weld seams and minimal welding deformation. 2. The shielding gas is argon with a purity of 99.99%. When the welding current is 50–150 A, the argon flow rate is 8–10 L/min; when the current is 150–250 A, the argon flow rate is 12–15 L/min. 3. The length by which the tungsten electrode protrudes from the gas nozzle is preferably 4–5 mm; it is 2–3 mm in areas with poor shielding such as corner welding, and 5–6 mm in areas with deep grooves. The distance between the nozzle and the workpiece generally should not exceed 15 mm. 4. To prevent the occurrence of welding pores, any rust, oil, or other contaminants on the welding area must be thoroughly cleaned off. 5. Welding arc length: For welding ordinary steel, 2–4 mm is appropriate, while for welding stainless steel, 1–3 mm is suitable; an excessively long arc results in poor shielding effect. 6. When performing butt welding, in order to prevent the back side of the base weld bead from oxidizing, gas shielding is also required on that back side. 7. To ensure that argon provides effective protection for the welding pool and to facilitate welding operations, the center line of the tungsten electrode should form an angle of 80–85° with the workpiece at the welding site. The angle between the filler wire and the workpiece surface should be as small as possible, typically around 10°. 8. Wind protection and ventilation. In areas with wind, please install wind shields, while indoors appropriate ventilation measures should be taken. II. Key points and precautions for stainless steel MIG welding 1. Use a flat-characteristic welding power source; for DC welding, reverse polarity should be employed (the wire is connected to the positive pole). 2. Pure argon gas (with a purity of 99.99%) or Ar+2%O2 is generally used, with an airflow rate of 20–25 L/min being appropriate. 3. Arc length: For MIG welding of stainless steel, welding is generally carried out under a spray transition condition, with the voltage adjusted so that the arc length remains between 4 and 6 mm. 4. Wind protection. MIG welding is susceptible to the influence of wind; even a gentle breeze can cause porosity, so windproof measures should be taken in areas where the wind speed is 0.5 m/sec or higher. III. Key points and precautions for welding with stainless steel cored wire 1. Use a flat-characteristic welding power source; reverse polarity should be employed when welding with direct current. A regular CO2 welder can be used for welding, but please adjust the pressure on the wire feed wheel to be slightly looser. 2. The shielding gas is generally carbon dioxide, with a gas flow rate of 20~25 L/min being appropriate. 3. The distance between the welding tip and the workpiece should be 15~25 mm. 4. Dry elongation: Generally, it is around 15 mm when the welding current is 250 A or less, and around 20–25 mm when the current is above 250 A.