MIG Welding Basics: Techniques and Tips for Success
It’s important for new welding operators to establish proper MIG techniques in order to achieve good weld quality and maximize productivity. Safety best practices are key, too. It’s just as important, however, for experienced welding operators to remember the fundamentals in order to avoid picking up habits that could negatively impact welding performance.
From employing safe ergonomics to using the proper MIG gun angle and welding travel speeds and more, good MIG welding techniques provide good results. Here are some tips.
A comfortable welding operator is a safer one. Proper ergonomics should be among the first fundamentals to establish in the MIG welding process (along with proper personal protective equipment, of course). Ergonomics can be defined, simply, as the “study of how equipment can be arranged so that people can do work or other activities more efficiently and comfortably.”1 The importance of ergonomics for a welding operator can have far reaching effects. A workplace environment or task that causes a welding operator to repetitively reach, move, grip or twist in an unnatural way, or even stay in a static posture for an extended period of time without rest, can lead to repetitive stress injuries with life-long impacts.
Proper ergonomics can protect welding operators from injury while also improving productivity and profitability of a welding operation by reducing employee absences.
Some ergonomic solutions that can improve safety and productivity include:
1. Using a MIG welding gun with a locking trigger to prevent “trigger finger,” which is caused by applying pressure to a trigger for an extended period of time.
2. Using a MIG gun with a rotatable neck to help the welding operator move more easily to reach a joint with less strain on the body.
3. Keeping hands at elbow height or slightly below while welding.
4. Positioning work between the welding operator’s waist and shoulders to ensure welding is being completed in as close of a neutral posture as possible.
5. Reducing the stress of repetitive motions by using MIG guns with rear swivels on the power cable.
6. Using different combinations of handle angles, neck angles and neck lengths to keep the welding operator’s wrist in a neutral position.
Proper work angle, travel angle and movement
The proper welding gun or work angle, travel angle and MIG welding technique depends on the thickness of the base metal and the welding position. Work angle is “the relationship between the axis of the electrode to the welders work piece”. Travel angle refers to employing either a push angle (pointing in the direction of travel) or a drag angle, when the electrode is pointed opposite of travel. (AWS Welding HandBook 9th Edition Vol 2 Page 184)2.
When welding a butt joint (a 180-degree joint), the welding operator should hold the MIG welding gun at a 90-degree work angle (in relation to the work piece). Depending on the thickness of the base material, push the gun at a torch angle between 5 and 15 degrees. If the joint requires multiple passes, a slight side-to-side motion, holding at the toes of the weld, can help fill the joint and minimize the risk of undercutting.
For T-joints, hold the gun at a work angle of 45 degrees and for lap joints a work angle around 60 degrees is appropriate (15 degrees up from 45 degrees).
In the horizontal welding position, a work angle of 30 to 60 degrees works well, depending on the type and size of the joint. The goal is to prevent the filler metal from sagging or rolling over on the bottom side of the weld joint.
For a T-joint, the welding operator should use a work angle of slightly greater than 90 degrees to the joint. Note, when welding in the vertical position, there are two methods: weld in an uphill or a downhill direction.
The uphill direction is used for thicker material when greater penetration is needed. A good technique for a T-Joint is call the upside-down V. This technique assures the welding operator maintains consistency and penetration in the root of the weld, which is where the two pieces meet. This area is the most important part of the weld.The other technique is downhill welding. This is popular in the pipe industry for open root welding and when welding thin gauge materials.
The goal when MIG welding overhead is to keep the molten weld metal in the joint. That requires faster travel speeds and work angles will be dictated by the location of the joint. Maintain a 5 to 15 degree travel angle. Any weaving technique should be kept to a minimum to keep the bead small. To gain the most success, the welding operator should be in comfortable position in relation to both the work angle and the direction of travel.
Wire stickout and contact-tip-to-work distance
Wire stickout will change depending on the welding process. For short-circuit welding, it is good to maintain a 1/4- to 3/8-inch wire stickout to reduce spatter. Any longer of a stickout will increase electrical resistance, lowering the current and leading to spatter. When using a spray arc transfer, the stickout should be around 3/4 inch.
Proper contact-tip-to-work distance (CTWD) is also important to gaining good welding performance. The CTWD used depends on the welding process. For example, when using a spray transfer mode, if the CTWD is too short, it can cause burnbacks. If it’s too long, it could cause weld discontinuities due to lack of proper shielding gas coverage. For spray transfer welding, a 3/4-inch CTWD is appropriate, while 3/8 to 1/2 inch would work for short circuit welding.
Welding travel speed
The travel speed influences the shape and quality of a weld bead to a significant degree. Welding operators will need to determine the correct welding travel speed by judging the weld pool size in relation to the joint thickness.
With a welding travel speed that’s too fast, welding operators will end up with a narrow, convex bead with inadequate tie-in at the toes of the weld. Insufficient penetration, distortion and an inconsistent weld bead are caused by traveling too fast. Traveling too slow can introduce too much heat into the weld, resulting in an excessively wide weld bead. On thinner material, it may also cause burn through.
When it comes to improving safety and productivity, it’s up to the experienced veteran welding operator as much as the new welding to establish and follow proper MIG technique right. Doing so helps avoid potential injury and unnecessary downtime for reworking poor quality welds. Keep in mind that it never hurts for welding operators to refresh their knowledge about MIG welding and it’s in their and the company’s best interest to continue following best practices.
1. Collins Dictionary, “ergonomics,” collinsdictionary.com/dictionary/english/ergonomics.
2. Welding Handbook, 9th ed., Vol. 2, Welding Processes, Part 1. American Welding Society: Miami, Fla., p. 184.