MIG WELDING
Metal inert gas (MIG) or Gas metal arc welding (GMAW) are widely used to join long work pieces. Continuously feed wire is deposited on a base metals. The weld pool is shielded by inert gases. Hence weld joint can be prevented by the atmospheric contamination. MIG welding can be used with several metals and alloys like carbon steel, Aluminum, Nickel, stainless steel etc. The biggest limitation of MIG welding is that it cannot be used for overhead or vertical weld position.
MIG WELDING ELECTRODES:
While choosing proper MIG welding electrode one have to keep the following points in mind:
(1) Properties of electrode and metals to be weld should match
(2) Resistance to the abrasion
(3) Position of weld
Several electrodes used in MIG welding and its code are as below:
(1) ER 70S-6 MIG
This type of electrode is used to weld Carbon steel or mild steel. Carbon or Argon gases are used as a shielding gases. Either 100% Carbon Dioxide gas or C25 gas that is mixture of 25% Carbon Dioxide and 75% Argon are often used during welding process. Designation is as below:
ER– Stands for an electrode or filler rod
70- A minimum of 70,000 psi of tensile strength
S –Solid wire
6- Amount of deoxidizing agent on the electrode. This is a copper coating on the electrode and there are different types to
(2) ER308L and ER308LSi
These are stainless electrodes and mostly used for lower grade stainless steels 301, 302, 304, 305, and 308. Designation is as below:
ER- Stands for an electrode or filler rod
308– The grade of the Stainless Steel Electrode
L –Low Carbon
Si-(Optional) Sometime “Si” is added . Basically it helps the weld wash into the metal better.
(3) ER309L and ER309Si
The 309 series used to weld stainless steel to mild or stainless to carbon or low alloy steels. It welds stainless steel grades 304 through 310 when needed. The gas used most of the time is the same C2 or 2% carbon dioxide and 98% Argon. The designation for the ER309L and ER309Si are as below:
ER- Stands for an electrode or filler rod
309– The grade of the Stainless Steel Electrode
L –Low Carbon
Si-(Optional) Sometime “Si” is added . Basically it helps the weld wash into the metal better
(4) ER3016L and ER316LSi
These stainless electrodes are mostly used for higher grade stainless steels mainly in the food industries and marine applications. The base metals the ER316 welds are stainless grades 304,305, 308, 310, 312, 314, 316, 317, 321, 347 and 348. The wire designation for the ER316L and the ER316LSI are as follows:
ER- Stands for an electrode or filler rod
316– The grade of the Stainless Steel Electrode. This is food grade and true marine grade
L –Low Carbon. Carbon content is what gets the rust spots on stainless
Si- (Optional) Sometime “Si” is added . Basically it helps the weld wash into the metal better
Aluminum Electrodes selection for MIG welding is pretty straight forward. There are two typical choices and they are:
ER4043
ER5350
(5) ER4043
The ER4043 is the most commonly used MIG filler wire. It welds aluminum grades 2014, 3003, 3004, 4043, 5052, 6061, 6062 and 6063. It may also be used to weld cast aluminum grades 43, 214, 355 and 356. The electrodes designation is as follows:
ER- Stands for an electrode or filler rod
4– The series of the aluminum. This electrode is made from a 4000 series aluminum
043 –This number indicates the amount of silicone added to the electrode. 4000 series of aluminum alloys have silicone added to make that grade
(6) ER5350
The ER4043 is the most commonly used MIG filler wire. It welds aluminum grades 5050, 5052, 5056, 5083, 5086, 5154, 5356, 5454, 5456.The gas used is always 100% Argon and in rare cases a helium/Argon mix may the electrodes designation is as follows:
ER- Stands for an electrode or filler rod
5– The series of the aluminum. This electrode is made from a 5000 series aluminum
356 –This number indicates the amount of Magnesium added to the electrode
5000 series of aluminum alloys have Magnesium added to make this alloy
