The most common welding method for stainless steel
Mainly manual welding (MMA), followed by metal gas shielded welding (MIG/MAG) and tungsten inert gas shielded welding (TIG).
1. Preparation before welding
The thickness of 4mm is not required to be broken, and it can be directly welded and single-sided welded once. 4 to 6 mm thickness butt welds can be double-sided welded without breaking joints. 6 mm or more, generally open V or U, X-shaped groove. Secondly, the weldment and the filler wire are degreased and descaled. To ensure the quality of welding.
2 welding parameters
Including welding current, tungsten diameter, arc length, arc voltage, welding speed, protective airflow, nozzle diameter, etc.
(1) Welding current is a key factor in determining weld formation. Usually determined by the weldment material, thickness, and groove shape. (2) The diameter of the welding pole is determined according to the welding current. The larger the current, the larger the diameter. (3) Welding arc and arc film, the arc length ranges from about 0.5 to 3 mm, and the corresponding arc voltage is 8 to 10V. (4) Welding speed: The selection should take into account the current magnitude, the material sensitivity of the weldment, the welding position and the operation mode.
1 manual welding (MMA)
Manual soldering is a very common and easy to use soldering method. The length of the arc is adjusted by the human hand and is determined by the size of the gap between the electrode and the workpiece. At the same time, when used as an arc carrier, the electrode is also a weld filler material. This welding method is simple and can be used to weld almost any material. For outdoor use, it is very adaptable, even if it is used underwater. 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 arc. In most cases, the welding uses direct current, the electrode acts as both the arc carrier and also as Weld fill material. The electrode consists of an alloy or non-alloy metal core wire and a welding rod coating. This layer protects the weld from air and stabilizes the arc. It also causes the formation of a slag layer and protects the weld from forming it. The electrode can be either a titanium electrode or an alkaline layer, depending on the thickness and composition of the coating. The titanium electrode is easy to weld, the weld is flat and beautiful, and the weld slag is easy to remove. If the electrode is stored for a long time, it must be re-baked because moisture from the air will quickly build up in the electrode.
Stainless steel flux cored wire welding points and precautions
(1) The flat characteristic welding power source is used, and the reverse polarity is used for the DC welding. The welding can be carried out using a general CO2 welder, but the pressure of the wire feed wheel should be slightly loosened.
(2) The shielding gas is generally carbon dioxide gas, and the gas flow rate is preferably 20 to 25 L/min.
(3) The distance between the tip and the workpiece is preferably 15~25mm.
(4) Dry elongation: A general welding current is about 15 mm when it is 250 A or less, and about 20 to 25 mm when it is 250 A or more.
This is an automatic gas shielded arc welding method. In this method, the arc is stably heated between the current carrier wire and the workpiece under the shielding of the shielding gas, and the wire fed by the machine acts as an electrode and melts under its own arc. Due to the versatility and particularity of the MIG/MAG welding method, she is still the most extensive welding method in the world and is suitable for steel, non-alloy steel, low alloy steel and high alloy based materials. This makes it an ideal welding method for production and repair. When welding steel, MAG can meet the requirements of thin gauge steel plates with a thickness of only 0.6 mm. The shielding gas used herein is a reactive gas such as carbon dioxide or a mixed gas.
Stainless steel MIG welding points and precautions
(1) The flat characteristic welding power source is used, and the reverse polarity is used in the direct current (the welding wire is connected to the positive electrode).
(2) Generally, pure argon (purity of 99.99%) or Ar+2%O2 is used, and the flow rate is preferably 20~25L/min.
(3) Arc length: MIG welding of stainless steel is generally applied under the condition of jet transition, and the voltage should be adjusted to an arc length of 4-6 mm.
(4) Windproof: MIG welding is easily affected by wind, and sometimes breeze creates pores. Therefore, wind speed should be taken at a place where the wind speed is above 0.5 mc.
(5) Moisture proof: When welding outdoors, the workpiece must be protected from moisture to maintain the gas protection effect.
The arc is generated between the refractory tungsten welding wire and the workpiece. The commonly used shielding gas is pure argon. The supplied welding wire is not charged, and can be sent by hand or mechanically, and some special applications do not need to be sent. Into the wire. The material to be welded determines whether DC or AC is used: when DC is used, the tungsten wire is set to the negative pole because it has a deep penetration capability and is suitable for different types of steel, but for weld pools. There is no “cleaning effect”. The main advantage of the TIG welding method is that it can weld a wide range of materials, including workpieces with a thickness of 0.6mm or more. The materials include alloy steel, aluminum, magnesium, copper and its alloys, gray cast iron, ordinary dry, various bronzes, Nickel, silver, titanium and lead. The main areas of application are the welding of thin and medium-thickness workpieces, which are used as weld root welds on thicker sections.
Stainless steel TIG welding points and precautions
(1) A power supply with a vertical external characteristic is used, and a positive polarity (a negative electrode is connected to the negative electrode) is used for direct current.
(2) It is generally suitable for the welding of thin plates of 6mm or less, and has the characteristics of beautiful weld bead formation and small welding deformation.
(3) The shielding gas is argon and the purity is 99.99%. When the welding current is 50~150A, the argon flow rate is 8~10L/min. When the current is 150~250A, the argon flow rate is 12~15L/min.
(4) The length of the tungsten electrode protruding from the gas nozzle is preferably 4~5mm, 2~3mm in the place where the shielding property is poor, such as angle welding, 5~6mm in the deep groove, the distance from the nozzle to the working is generally not More than 15mm.
(5) In order to prevent the occurrence of welding air holes, the welding parts must be cleaned such as rust and oil.
(6) Welding arc length, when welding ordinary steel, 2~4mm is better, and when welding stainless steel, 1~3mm is better, too long, the protection effect is not good.
(7) When the bottom of the butt weld is prevented from being oxidized, the back side also needs to be protected by gas.
(8) In order to make the argon gas protect the weld pool well and facilitate the welding operation, the tungsten center line and the welding workpiece should generally maintain 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 °.
(9) Wind and ventilation. In windy places, take measures to block the net, and indoors should take appropriate ventilation measures.
Stainless steel welding process requirements
Pre-weld preparation: 4mm thickness is not required to open the gap, direct welding, single-sided one-time penetration. 4 to 6 mm thickness butt welds can be double-sided welded without breaking joints. 6 mm or more, generally open V or U, X-shaped groove.
Secondly, the weldment and the filler wire are degreased and descaled. To ensure the quality of welding.
Welding parameters: including welding current, tungsten diameter, arc length, arc voltage, welding speed, protective airflow, nozzle diameter, etc.
1, welding current is a key factor in determining weld formation. Usually determined by the weldment material, thickness, and groove shape.
2, the diameter of the welding pole is determined according to the welding current, the larger the current, the larger the diameter.
3, welding arc and arc film, arc length range of about 0.5 to 3mm, the corresponding arc voltage is 8~10V.
4, welding speed: the selection should take into account the current size, weldment material sensitivity, welding position and operation mode and other factors.