Welding Common Joints Using Flux Core Wire MIG Welder
Introduction:
Flux core wire welder, introduced in 1935, follows the similar technique of a MIG welder. Both use similar equipment and continuous wire feeding. Both get the power supply from the same machine. They run semi-automatically and have a very high production rate of common welding joints. The key difference lies between them is in terms of shielding the electrode from the air. Unlike MIG welding, it gets shielding from the flux core that exists within the hollow wire electrode that helps you not to carry a gas tank for the welding. One of the major advantages of the flux core welding is you can use it for outdoor purposes even in any windy environment. You can say, this is a MIG welder with an attribute of SMAW welder.
How Fast is This?
The Flux core wire MIG welder is the most productive of all available manual welding processes. It can weld common joints for more than 25 pounds per hour. Furthermore, it can weld ½ inch plates in a single pass on both sides with full level of penetration. That is why Flux core welder is the first choice for use in the shipbuilding industry. Even in windy situation it provides a fast, reliable, and quality weld.
Guide to Flux Core Wire MIG Welding:
Safety Preparation:
Before starting any welding project, you need to ensure you possess the required safety apparels ad you have removed the probable fire hazards from the project area. You need to have leather boots or shoes, long-sleeve & flame resistant jacket, full-length pants without cuff, leather gloves. Safety glasses, bandana or skull cap, and welding helmet that will protect you from spatter and sparks.
Metal Preparation:
Although flux core welding is highly tolerant of surface contamination, you should clean the surface thoroughly beforehand so that no rust or scale can contaminate the final weld. You can use either a metal brush or a grinder for cleaning. Apart from cleaning the surface of the metal, you need to clean the portion of the metal where ground clamp gets attached. For complete fusion of both parts of materials over ¼ inch, you should always bevel the edges.
Equipment Preparation:
Before you strike the arc, check all the equipment properly that there are tight connections of all cables, and they are free of any damage or wear & tear. The Flux core wire MIG welding requires either a straight polarity or a negative DC electrode. So you need to select the polarity of the electrode perfectly. You have to use the right drive rolls as the flux core wire is softer than the solid one. Right drive rolls don’t let the wire to become compressed or deformed. You should check and adjust the wire tension by following the owner’s manual. You may experience a poor wire feeding performance if the wire tension on the drive pools or the sire spool hub is too high or too little. Furthermore, you need to check the consumables so that there is no excess spatter on the contact tips, no wearing on the contact tips & liners, and rust on the wire.
Selection of Wire:
If you apply the flux core wire MIG weld on mild steel, then you can conveniently use the E71T-11 designated wire for any position. It is available in different sizes and suitable for outstanding welding features for both thin and thick metal. The wire diameter of 0.30 inches is good for applying for a variety of metal thicknesses. If you need to weld a thick metal at a high level of heat, it is better to use wire with diameter ranging from 0.35-0.45 inch.
Voltage and Ampere:
Depending on the factors like metal thickness, welding position, wire diameter, and joint configuration, you can determine the voltage and amperage requirement of a weld. The power source has a reference chart that dictates the necessary level of voltage. It also sets the speed of the wire feed based on metal thickness and wire diameter. Welding calculator available with this welder is a great help for fine-tuning the final parameters based on some few taste welds.
Wire Stick-out:
It is the length of the un-melted electrode from the contact tube tip, excluding arc length. Experts recommend a stick-out of ¾ inch for the flux core welding.
Push or Pull Technique:
Experts suggest that you always use a pull technique for the flux core welding. In this technique, you can tip the gunpoint at the weld pool and pull away on time. According to a rule of thumb, you pull when there is slag.
Travel Angle:
The travel angle denotes the relative angle at which you should hold the welding gun in a perpendicular position within the level of the weld joint. 5-15 degrees is perfect for normal welding at all positions. If the travel angle is beyond 20-25 degrees, you will experience less penetration, more spatter, and general arc instability.
Work Angle:
Work angle is the position at which you hold the gun relative to the level of the welding joint. Depending on the joint configuration and position work angle will vary. At flat position, for butt weld (a 180 degree joint) 90 degree is a perfect work angle; for fillet weld (a 90 degree joint) 45 degree of work angle is suitable; and for a fillet weld (a lap joint) 60-70 degree of work angle of the gun is great for the outcome. For horizontal position, your work angle of the gun should be between 0 and 15 degrees. Vertical welding both up and down is quite difficult. You need to more cautiously pre-setting up of welding for getting the desired outcome. In vertical position, you have to face the challenge of gravity for which you will need to reduce the voltage & ampere by 10-15%. Overhead weld position is the most difficult part of the job, and you should avoid it if possible. Otherwise, use the smallest wire and lower the welding parameters by 15-20%.
Conclusion:
For the desired outcome on common joints weld from the flux core wire MIG welding, you have to practice more and more since this method requires you memorizing the correct parameters and gun travel guidelines.
