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Stainless steel welding technology points and precautions


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

Before welding preparation: 4mm thickness at break not open, welded directly, one-sided first penetration. 4 mm to 6 mm thickness butt weld joints can not open the break-sided welding. 6 mm or more, generally open V or U, X-shaped groove.

Second: weldments, filler wire degreasing and descaling. In order to ensure the welding quality.

Welding parameters: welding current comprises tungsten electrode diameter, arc length, arc voltage, welding speed, protection gas stream, the nozzle diameter and the like.

(1) The weld welding current is a key factor in the decision. Usually based weldment material, thickness and shape of the groove to decide.

(2) the diameter of the welding electrode according to the welding current size of the decision, the greater the current, the greater diameter.

(3) the arc and arc movies, arc length range of about 0.5 to 3mm, corresponding arc voltage 8 ~ 10V.

(4) welding speed: select when you want to take into account the current size, the sensitivity of the weldment material, welding position and method of operation and other factors.

 

1 SMAW (MMA):

Manual welding is a very common welding method is easy to use. Arc length adjusted by human hands, it depends on the size of the gap between the welding electrodes and the workpiece. Meanwhile, when the carrier as an arc, welding the weld filler material is.

This welding method is very simple and can be used to weld almost all materials. For outdoor use, it has a good adaptability, even under water use is also no problem. Electrode welding, arc length depends on the person's hand: When you change the gap electrode and the workpiece, you also change the length of the arc, in most cases, welding using DC arc electrode both as a carrier, but also as a. weld filler material. Electrode made of a metal alloy or non-alloy core wire and the electrode coating composition, this layer of skin to protect the weld from air drug abuse, while stabilizing the arc, it also causes the formation of slag layer to protect the weld it shape. Welding can be either titanium electrodes, can also be alkaline, depending on the coating thickness and composition. Ease of titanium type electrode welding, weld flat appearance and easy slag removal. If the electrode storage for a long time, must be re-baking, because the moisture from the air will soon accumulate in the electrode.

 

Stainless steel flux cored wire welding points and notes:

(1) with flat characteristic welding power source using reverse polarity DC welding. The use of general CO2 welding can be welding, but the pressure wire wheels Please slightly loosen.

(2) shielding gas is generally carbon dioxide gas, the gas flow rate to 20 ~ 25L / min more appropriate.

(3) the distance between the tip and the workpiece to 15 ~ 25mm is appropriate.

(4) Dry elongation: general welding current is 250A below about 15mm, at 250A above about 20 ~ 25mm is appropriate.

 

2 MIG / MAG welding:

This is an automatic gas shielded arc welding methods. In this method, the protective gas shielded arc stable heat between the current carrier wire and workpiece, the machine into the wire as the electrode, melts in its own arc. Because of the versatility MIG / MAG welding and specificity advantages, so far she is still the world's most widely used welding method for steel, non-alloy steel, low alloy steel and high alloy as the base material. This makes it ideal for production and repair welding methods. When welding steel, MAG can meet only 0.6mm thick, thin-gauge steel requirements. As used herein, the protective gas is a reactive gas, such as carbon dioxide or a mixed gas.

 

Stainless steel MIG welding points and notes:

(1) with flat characteristic welding power source using reverse polarity (wire connected to positive) dc.

(2) generally use pure argon gas (purity of 99.99%) or Ar + 2% O2, the flow rate to 20 ~ 25L / min is appropriate.

(3) Arc length: stainless steel MIG welding, spray conditions generally in the transition down welding, arc voltage to be adjusted to the extent of 4 ~ 6mm.

(4) Wind: MIG welding susceptible to wind, and sometimes the breeze and have holes, so wind speed at 0.5m / sec over the place, all their precautions should be taken.

(5) proof: outdoor welding, the workpiece must be protected from moisture, in order to maintain the protective effect of the gas.

 

3 TIG welding:

Refractory arc between the wire and the workpiece W, shielding gas generally used is pure argon, into the wire not charged, either bypass, and to be a mechanical transmission, there is no need to send a number of specific purposes into the wire. Materials to be welded is decided with DC or AC: When using direct current, tungsten electrode wire is set to negative, because it has a deep penetration ability, for different types of steel is very appropriate, but the weld puddle There is no "clean effect."

The main advantage of TIG welding is a wide range of materials can be welded large, including the thickness of 0.6mm and above the workpiece materials, including steel, aluminum, magnesium, copper and its alloys, gray cast iron, ordinary dry, a variety of bronze in, nickel, silver, titanium and lead. The main application areas are welding thin and medium thickness of the workpiece, it is used as the root pass welding on thicker sections.

 

Stainless steel TIG welding points and notes:

(1) The vertical external characteristics of power DC when positive polarity (wire then negative).

(2) is generally suitable for welding thin 6mm or less, having a weld appearance, a small amount of welding deformation characteristics.

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

(4) from the gas tungsten nozzle protruding length to 4 ~ 5mm preferably, in fillet welding and other places with poor shielding is 2 ~ 3mm, where the grooving depth is 5 ~ 6mm, the distance to the nozzle is generally not work more than 15mm.

(5) In order to prevent weld porosity of welded parts such as rust, oil, etc. Be sure to clean up.

(6) the length of the welding arc when welding ordinary steel, preferably to 2 ~ 4mm, and the welding of stainless steel, preferably to 1 ~ 3mm, then the protective effect is too long is not good.

(7) docking base, in order to prevent the back of the bottom bead is oxidized, the back also need to implement a gas protection.

(8) For the argon weld pool well protected, and easy welding operation, TIG welding workpiece center line and should generally be maintained 80 ~ 85 ° angle, the angle between the filler wire and the workpiece surface should be as small as possible , usually about 10 °.

(9) windproof and ventilation. Windy place, be sure to take measures to block network, and in the indoor ventilation should take appropriate measures.

 

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