The most commonly used welding method of stainless steel
Preparation before welding:
The thickness below 4mm does not need to be broken, and it can be directly welded, penetrating one side at a time. Four to six? Butt weld with a thickness of mm can be welded on both sides without damaging the joint. 6? Mm or more, generally open V-shaped or U, X-shaped groove.
Secondly, degreasing and derusting are carried out on the welding wire filled in the welding position. So as to ensure the welding quality.
Welding parameters: including welding current, tungsten electrode diameter, arc length, arc voltage, welding speed, shielding gas flow, nozzle diameter, etc.
(1) welding current is the key factor to determine weld formation. It is usually determined by the material, thickness and groove shape of the weldment.
(2) The electrode diameter is determined according to the welding current, and the larger the current, the larger the diameter.
(3) For welding arc and arc film, the arc length is about 0.5 ~ 3mm, and the corresponding arc voltage is 8~ 10V.
(4) Welding speed: Current, sensitivity of weldment material, welding position and operation mode should be considered when selecting.
way
1. Manual welding (MMA):
Manual welding is a very common and easy-to-use welding method. The length of the arc is adjusted by hand, depending on the gap between the electrode and the workpiece. Meanwhile, when used as an arc carrier, covered electrode is also a welding filler.
This welding method is simple and can be used to weld almost all materials. Outdoor use, good adaptability, even underwater use. In electrode welding, the arc length depends on the human hand: when you change the gap between the electrode and the workpiece, you also change the arc length. In most cases, direct current is used for welding, and the electrode is used as both arc carrier and weld filler. Covered electrode is composed of alloy or non-alloy metal core wire and coated covered electrode coating, which protects the weld from air, stabilizes the arc, and also causes the formation of slag layer, protecting the weld and shaping it. The electrode can be a titanium-coated electrode or an alkaline electrode, depending on the thickness and composition of the coating. Titanium covered electrode is easy to weld, the weld is smooth and beautiful, and the welding slag is easy to remove. If covered electrode is stored for a long time, it must be baked again, because the moisture in the air will quickly accumulate in covered electrode.
Welding points and precautions of stainless steel flux-cored wire;
(1) adopts flat welding power supply, and DC welding adopts reverse polarity. Ordinary CO2 welder can be used for welding, but the pressure of wire feeder should be slightly adjusted.
(2) The protective gas is generally carbon dioxide gas, and the gas flow rate is 20~25L/min.
(3) The distance between the welding nozzle and the workpiece shall be 15~25mm.
(4) Dry elongation: generally, the welding current is about 15mm when it is below 250A, and about 20~25mm when it is above 250 A. ..
2.？ MIG/MAG welding:
This is an automatic gas shielded arc welding method. In this method, the arc generates heat between the current-carrying wire and the workpiece under the protection of protective gas, and the wire fed by the machine is used as the covering electrode and melted under its own arc. Because of the universality and particularity of MIG/MAG welding method, it is still the most widely used welding method in the world, which 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 maintenance. When welding steel, MAG can meet the requirements of thin steel plate with a thickness of only 0.6 mm. The protective gas used here is active gas, such as carbon dioxide or mixed gas.
Key points and precautions of stainless steel MIG welding;
(1) adopts flat welding power supply, and DC adopts reverse polarity (the welding wire is connected to the positive electrode).
(2) Generally, pure argon (purity is 99.99%) or Ar+2%O2 is used, and the flow rate is 20~25L/min.
(3) Arc length: MIG welding of stainless steel is generally carried out under the condition of spray transition, and the voltage should be adjusted to the extent of arc length of 4~6mm.
(4) Windproof: MIG welding is easily affected by wind, and sometimes the breeze will produce pores, so windproof measures should be taken wherever the wind speed is above 0.5m/sec.
(5) Moisture-proof: During outdoor welding, the workpiece must be moisture-proof to maintain the protective effect of gas.
3.？ TIG welding:
An arc is generated between the refractory tungsten welding wire and the workpiece. The shielding gas is generally pure argon, and the welding wire is not charged, so it can be sent manually or mechanically, and there are some special uses that do not need to be sent. The material to be welded determines whether DC or AC is used: when DC is used, tungsten welding wire is designated as the negative electrode, because it has strong penetration ability and is suitable for different kinds of steel, but it has no "cleaning effect" on the molten pool.
The main advantage of TIG welding method is that it can weld a wide range of large materials, including workpieces with a thickness of more than 0.6 mm. Materials include alloy steel, aluminum, magnesium, copper and its alloys, gray cast iron, common valve stem, various bronzes, nickel, silver, titanium and lead.
Key points and matters needing attention in TIG welding of stainless steel;
(1) adopts vertical external characteristic power supply, and DC adopts positive polarity (welding wire is connected to negative electrode).
(2) It is generally suitable for welding thin plates below 6mm, and has the characteristics of beautiful weld formation and small welding deformation.
(3) The shielding gas is argon with a purity of 99.99%. When welding current is 50~ 150A, argon flow rate is 8~ 10L/min, and when welding current is 150A, argon flow rate is 12~ 15L/min.
(4) The length of the tungsten electrode protruding from the gas nozzle is preferably 4~5mm, the place with poor shielding performance such as fillet welding is 2~3mm, the place with deep groove is 5~6mm, and the distance from the nozzle to the workpiece is generally not more than15 mm. ..
(5) In order to prevent welding blowholes, the welding parts must be cleaned up if there is rust and oil stain.
(6) When welding ordinary steel, the welding arc length is 2~4mm, and when welding stainless steel, it is1~ 3 mm.. If it is too long, the protection effect is not good.
(7) When backing the butt weld, in order to prevent the back of the bottom bead from being oxidized, the back should also be protected by gas.
(8) In order to protect the welding pool with argon and facilitate the welding operation, the center line of tungsten electrode should generally keep an angle of 80 ~ 85 with the workpiece at the welding place, and the angle between the filler wire and the workpiece surface should be as small as possible, generally about10.
(9) Wind and ventilation. In windy places, please take measures to block the net, while indoors, appropriate ventilation measures should be taken.
With the increasing application of stainless steel products in the market, stainless steel, as a product that has been widely used in industry and life, not only provides convenience for people's lives as an electric kettle, but also plays a certain role in improving work efficiency in some industrial and electrical industries. The method of stainless steel has gradually become an aspect that we need to understand. I believe that the introduction of the above stainless steel methods can help you better understand stainless steel.