The commonly used welding method for stainless steel is manual welding（MMA), followed by metal inert gas welding (MIG/MAG) and tungsten inert gas welding (TIG).

    Preparation before welding:For thicknesses below 4mm, there is no need to open a gap and welding can be carried out directly, with one side welded through at a time. Butt welds with a thickness of 4 to 6 mm can be welded on both sides of a non cracked joint. Above 6mm, generally with V or U, X-shaped grooves.

    Secondly, remove oil and remove oxide skin from the welding parts and fill the welding wire. To ensure welding quality.

Welding parameters: including welding current, tungsten electrode diameter, arc length, arc voltage, welding speed, protective airflow, nozzle diameter, etc.

    （1) The welding current is a key factor determining the formation of the weld seam. It is usually determined based on the material, thickness, and groove shape of the weldment.

    （2) The diameter of the welding electrode is determined by the welding current, and the larger the current, the larger the diameter.

    （3) Welding arc and arc film, with an arc length range of approximately 0.5 to 3mm, corresponding to an arc voltage of 8--10V。

    （4) Welding speed: When selecting, factors such as current level, sensitivity of welding material, welding position, and operation mode should be considered.

    1. Manual Welding (MMA):

    Manual welding is a very common and easy to use welding method. The length of the arc is adjusted by human hands and depends on the size of the gap between the welding electrode and the workpiece. Meanwhile, when used as an arc carrier, the welding electrode is also the filler material for the weld seam.

    This welding method is very simple and can be used to weld almost all materials. For outdoor use, it has good adaptability and even underwater use is not a problem. In electrode welding, the length of the arc is determined by the human hand: when you change the gap between the electrode and the workpiece, you also change the length of the arcIn most cases, welding uses direct current, with electrodes serving as both arc carriers and weld filler materials. The electrode is composed of alloy or non alloy metal core wires and electrode coating, which protects the weld seam from air damage and stabilizes the arc. It also causes the formation of a slag layer, protecting the weld seam and shaping it. Welding electrodes can be either titanium type or alkaline, depending on the thickness and composition of the coating. Titanium type welding rods are easy to weld, with flat and beautiful welds, and easy to remove welding slag. If the welding rod is stored for a long time, it must be baked again because moisture from the air can quickly accumulate in the welding rod.

    Key points and precautions for stainless steel flux cored wire welding:

    （1) Use a flat polarity welding power source, and use reverse polarity during DC welding. A regular CO2 welding machine can be used for welding, but please loosen the pressure of the wire feeding wheel slightly.

    （2) The protective gas is generally carbon dioxide gas, with a gas flow rate of 20--25L/min is more suitable.

    （3) The distance between the welding nozzle and the workpiece is 15--25mm is recommended.

    （4) Dry extension length: Generally, when the welding current is below 250A, it is about 15mm, and when it is above 250A, it is about 20--25mm is more suitable.

    2. MIG/MAG welding:

    This is an automatic gas shielded arc welding method. In this method, the arc generates stable heat between the current carrier wire and the workpiece under shielding gas, and the metal wire fed by the machine serves as the welding rod, which melts under its own arc. Due toThe advantages of the universality and specificity of MIG/MAG welding method still make it a widely used welding method today, suitable for materials based on steel, non alloy steel, low alloy steel, and high alloy. This makes it an ideal welding method for production and repair. When welding steel, MAG can meet the requirements of only 0.6mm thick thin gauge steel plates. The protective gas used here is an active gas, such as carbon dioxide or a mixture of gases.

    Stainless steelKey points and precautions for MIG welding:

    （1) Use a flat polarity welding power supply, and use reverse polarity (welding wire connected to the positive electrode) for DC.

    （2) Generally, pure argon gas (with a purity of 99.99%) or Ar+2% O2 is used, with a flow rate of 20--25L/min is appropriate.

    （3) Arc length: MIG welding of stainless steel is generally carried out under spray transfer conditions, and the voltage should be adjusted to an arc length of 4--6mm degree.

    （4) Wind proof: MIG welding is easily affected by wind, and sometimes slight winds can cause air holes. Therefore, wind proof measures should be taken in places with wind speeds above 0.5m/sec.

    （5) Moisture proof: When welding outdoors, it is necessary to protect the workpiece from moisture to maintain the protective effect of the gas.

    3. TIG welding:

    An arc is generated between the refractory tungsten welding wire and the workpiece. The general protective gas used is pure argon, and the welding wire fed is not charged. It can be manually or mechanically fed, and there are also some specific applications where the welding wire does not need to be fed. The material being welded determines whether to use direct current or alternating current: When using direct current, the tungsten wire is set as the negative electrode because it has a deep penetration ability, which is suitable for different types of steel, but has no effect on the weld poolCleaning effect.

    The main advantage of TIG welding method is that it can weld a wide range of materials, including workpieces with a thickness of 0.6mm and above, including alloy steel, aluminum, magnesium, copper and its alloys, gray cast iron, ordinary dry, various bronze, nickel, silver, titanium, and lead. The main application area is to weld thin and medium thickness workpieces, which are used as root passes on thicker sections.

     Stainless steelKey points and precautions for TIG welding:

    （1) A power supply with vertical external characteristics is used, and positive polarity (welding wire connected to negative electrode) is used for DC.

    （2) It is generally suitable for welding thin plates below 6mm, with the characteristics of beautiful weld formation and small welding deformation.

    （3) The protective gas is argon with a purity of 99.99%. When the welding current is 50--At 150A, the argon flow rate is 8--10L/min, when the current is 150--At 250A, the argon flow rate is 12--15L/min。

    （4) The length of the tungsten electrode protruding from the gas nozzle is 4--5mm is preferred, but in areas with poor shielding such as fillet welding, it is 2--3mm, where the groove depth is 5--6mm, the distance from the nozzle to the working position generally does not exceed 15mm.

    （5) To prevent the occurrence of welding pores, any rust, oil stains, etc. on the welding area must be cleaned thoroughly.

    （6) Welding arc length, when welding ordinary steel, takes 2--4mm is preferred, while when welding stainless steel, 1--3mm is preferred, but if it is too long, the protection effect is not good.

    （7) To prevent oxidation on the back of the bottom weld bead during butt welding, gas protection is also required on the back.

    （8) In order to effectively protect the welding pool with argon gas and facilitate welding operations, the center line of the tungsten electrode and the workpiece at the welding site should generally be kept at 80%--At an angle of 85 °, the angle between the filler wire and the surface of the workpiece should be as small as possible, usually around 10 °.

（9) Wind protection and ventilation. In windy areas, it is important to take measures to block the grille, while indoors, appropriate ventilation measures should be taken.