How to choose the right rods, wire, tungsten, stick electrodes and compressed gases for your welding jobs
In welding, consumables are those materials that are used up quickly and need to be replaced. And since scores of product lines exist, along with a variety of classification systems, ordering these items can be something of an adventure. Regardless, several important variables will factor into your selection process:
- Type of metal being welded (steel, aluminum, etc.)
- The objects to be welded (pipe, plates, etc.)
- Type and size of the weld (groove, fillet, etc.)
- Code and structural requirements
- Welding position (vertical, overhead, etc.)
- Location environment (extreme cold, underwater, etc.)
- Available sizes of the appropriate rod/wire/electrode
The American Welding Society (AWS), American Society of Mechanical Engineers (ASME), and other industry associations have tried to simplify the welder’s job of choosing the right consumables by establishing various product classifications. Following these standards should insure selecting the right product to meet the welding code. While manufacturers produce their own proprietary brands and models of products, they nonetheless bear the identification of the appropriate industry classification. So always be on the lookout for this info when shopping around.
Due to the multitude of choices out there, an experienced welder, technician, purchaser or welding engineer maintains a binder or database containing the current product lines from different manufacturers and suppliers. These reference aids should likewise include product spec sheets that describe in detail the properties of each item and its compliance with AWS and ASME codes (if any). If you’re a student, it will save you time and headaches to put together your own binder based on the work you’re doing in school.
On-the-job, entry-level welders should be versed in the standard classifications of common filler rods, wire and electrodes used by the companies they work for; otherwise, a lot of time may be wasted on research. For instance, you may be asked to fetch supplies from the storeroom or drive over to a local welding supply store to purchase consumables for a job that needs to be finished soon. So mastering the labyrinth of products is a must.
Stick Welding Electrodes
If you’re new to the profession, you might be a little confused about the difference between an electrode and a filler rod. In stick welding, the filler rod and the electrode are one and the same. Electricity supplied by a welding machine energizes the rod, which is attached to a metal clamp. (See photo below.) An electric arc is produced, generating intense heat. This melts the tip of the rod into the molten pool within the joint on the base metal.
Stick welding on a pipe is one of the more difficult processes to learn, but once you master it, you’ll be eligible for a ton of high-paying jobs worldwide.
(If you’re still confused about welding processes, take a moment to read the Skills to Learn section.)
Stick Electrode Classification
Stick electrodes are sold for the following metals:
- Mild steel
- Stainless steel
- Low-alloy steel
- Cast iron
AWS classifies stick electrodes according to several codes, depending on the metal type. One of the most common is AWS A5.1/A5.1M: Specification for Carbon Steel Electrodes for Shielded Metal Arc Welding. E-7018 and E-6010 are examples of rods used by pipe welders. Here’s what the numbers indicate:
E – Electrode
70 – Tensile strength of the weld metal, measured in Pounds per Square Inch (PSI). Note: some countries substitute a metric unit for PSI.
1 – This single digit number tells you the most difficult welding position you can use the electrode in (1 = any position 2 = horizontal and flat; 3 = flat only; 4 = overhead, horizontal, vertical down and flat)
8 – Since this last digit is sometimes combined with the third number to derive information about an electrode, it can cause some confusion. The goal here is to communicate the flux/deoxiders and other ingredients used in the electrode coating. Coatings are designed for both the polarity of the power source and the welding position. Thus, you have to read the two digits together to know what’s in the coating. The chart below gives you the recipe for all- position (1) and horizontal/flat (2) welding, along with the current types/polarties available for each rod designation.
On occasion, you’ll also come across numbers like E-8018-C1. The suffix at the end usually indicates that alloys have been added to the electrode. The most common are molybdenum, chromium and nickel. Here are a few examples:
A1 – Carbon Moly
B1 – 1/2 CR, 1/2 MO
B2 – 1-1/4 CR, 1/2 MO
B3 – 1-1/4 CR, 1 MO
C1 – 2-1/2 Nickel
C2 – 3-1/2 Nickel
C3 – 1 Nickel
D1 – 1-1/2 MN, 1/4 MO
D2 – 1 MN, 1/4MO
M – conforms to military specs.
Here’s a chart that describes six standard electrodes used for welding mild steel:
Notice how the ingredients in the coating of the rod affect how the filler metal gets deposited in the weld, as well as the polarity required from the power source. (Incidentally, the weld metal in the center of the rod is the same for all these products.)
The welding trade also divides stick electrodes into four general groups. These are based on chemical additives designed to shield the weld pool, not only to prevent oxidation, porosity or some other potential weld defect, but to meet the existengies of the welder’s position:
Fast Freeze (0,1) – Used for overhead welding
Fill Freeze (2,3,4)
Fast Fill (21-27) – Limited to flat and horizontal position
Low Hydrogen (18, 28) – Limits porosity
These four categories are not easy for welding students to grasp at first, due perhaps to the lack of creativity in the naming conventions. Yet it helps to become familiar with the terminology, and to remember that not all stick rods work for every situation.
Another confusing concept concerns polarity in welding. Notice in the two charts shown earlier that there are three choices available under “Current”. AC represents the familiar alternating current, which is an acceptable option for all the electrodes listed there, except E-6010. The other two options, which pertain to DC (direct current), require a little explanation.
DCEP or DC+ “Electrode Positive” – This is also known as “reverse polarity”and is the choice for most stick welding. Although electrons inevitably flow through a circuit from its negative to positive sides, you can effectively reverse the current by switching the connections of your electrode holder and the work clamp. (On most industrial sticking welding machines nowadays, DCEP is either the default setting or accomplished by manipulating the controls to choose AC, DCEP or DCEN.
The objective for using DCEP is to put 70% of the heat (that’s generated by the electric arc) at the tip of the electrode, which can melt it with a vengeance into the joint. The other 30% ends up dispersed around the work piece.
DCEN or DC- “Electrode Negative” – This is “straight polarity”. Now 70% of the heat gets focussed on the work plates, and only 30% reaches the tip of the electrode. This situation is desirable when working with thin metal stock or a joint that doesn’t require deep penetration. DCEN is also the choice of polarity for most TIG welding on metals other than aluminum, which prefers AC as its current polarity.
Beware, there’s a lot of confusion about DCEN and DCEP. If you ever have questions, consult a reputable source, like the Miller or Lincoln Electric websites, or read a textbook on the subject. As a general rule of thumb, TIG likes DCEN, while Stick Welding likes DCEP.
Although stick welding is primarily used on carbon steel, you can purchase rods to weld some stainless steels and aluminum. The most common rod for stainless steel is 308, which works for base metals that are classified as either 304 or 308 using the AISI standard. As you’ll learn elsewhere on this website, the metal alloy known as stainless steel has a myriad of classifications based on the blend of metals used. Each blend of stainless steel is classified by a three-digit number, with the majority falling in the 200, 300 and 400 range. Thus, stainless steel stick electrodes are identified in part by these same numbers.
Aluminum electrode classifications, on the other hand, are identified by AISI 4000, 5000 and 6000 series numbers.For instance, a common rod is 4043.
To learn more about general metal classification systems, click here.
Aluminum stick welding with an E4043 rod.
Once a welder has decided on an acceptable electrode, that leaves two more decisions. What size (diameter) of electrode should be used? And what current range is right for this diameter?
Companies that sell consumables usually provide a chart that lists allowable amperage, based on rod diameter, to help you choose. Here’s an example:
Here’s a more general range of current settings for a variety of stick welding rods. Notice that the table recommends less current when welding in the vertical or overhead position.
As for choosing the right diameter of the rod, that depends on the type of weld you’re creating and the thickness of the base metal. (The coating around the electrode doesn’t count as part of its diameter, just the weld metal inside.) Since larger-diameter electrodes produce larger-sized welds, you wouldn’t want to use a 3/16″ rod on sheet metal that’s 1/8″ thick. Lap joints, as you’ll learn in school, require a lot less penetration and weld metal buildup than a beveled groove joint. Finally, heat is a major concern when welding metals other than carbon steel, so the allowable current range factors heavily into choosing the right rod. This is especially the case for welding on stainless steel, aluminum and other alloys.
Check out the Lincoln Electric consumables guide (PDF) to learn more about brands, specifications and other characteristics.
Care and Storage of Electrodes
Low-hydrogen stick electrodes (e.g. E-7018) require a special storage environment because of their coatings. Welders have to keep these rods dry, since moisture contains hydrogen.
So long as the rods remain sealed inside the box where they were originally packed, no special handling is required. But once the seal is broken, extra care must be taken. In a warehouse, or out in the field, it’s common practice to warm batches of them in a rod oven at 250 degrees about 30 minutes to an hour before use. In addition, the welder should fetch only a handful of warm rods from the oven at one time, placing them in an electrode pouch to stay warm until it’s time to go to work. (Keep in mind that these rods shouldn’t be heated more than three times in an oven, so only fill the oven with what you estimate needing each day.)
Next: MIG Wire