MIG Wire Selection Guide

Weldability


Welding performance of a MIG wire is described by the following:

Weld metal soundness
Weld puddle fluidity
Bead shape and edge wetting
Spatter tendency

Weld Metal Soundness

Soundness in weld metal is characterized by a lack of porosity, good fusion, and freedom from cracking. Porosity, the most frequently cited cause of poor weld soundness, is caused by excess oxygen from the atmosphere, the shielding gas, and any base plate contamination combining with carbon in the weld metal to form bundles of carbon monoxide (CO) gas. Some of the CO can become trapped as the weld cools forming pores called porosity. Typically, the MIG wire process is recognized as having very low hydrogen in the deposit. Factors, such as moisture in the shielding gas, atmospheric conditions, and plate condition, may have a varying degree of adverse effect on the actual diffusible hydrogen in the weld deposit.

Process
Control Of Porosity

Sufficient deoxidation of the weld puddle is needed to minimize CO formation and porosity. To accomplish this, Spoolarc wires contain elements with which oxygen combines in preference to carbon to form harmless slags. These elements, called deoxidizers, are manganese (Mn), silicon (Si), titanium (Ti), aluminum (Al), and zirconium (Zr). Aluminum, titanium and zirconium are very powerful deoxidizers — perhaps five times as effective as manganese and silicon.

Weld Puddle Fluidity, Bead Shape And Spatter

Fluidity of the molten weld puddle is important for several reasons. Fluid puddles tend to wet out smoothly at the edges and produce a flat, smooth bead shape, especially on fillet welds. This is important on multi-pass, short arc welds where lack-of-fusion defects can occur if bead shape is poor. Flat, well-wet-in beads are also desirable where appearance is a primary concern and where post weld grinding may be necessary to meet job requirements.

Caution: Excessive puddle fluidity can cause performance difficulties in out-of-position welding or in making concave horizontal fillets.
Influence Of Manganese And Silicon

Choosing the manganese and silicon content of a MIG wire is usually the major decision an operator must make. Increasing manganese and silicon affects puddle fluidity, bead shape and other factors. The Al, Ti and Zr deoxidizers in Spoolarc 65 wire tend to make its puddle somewhat sluggish. The “stiff” puddle characteristic makes this wire ideal for pipe - especially small diameter pipe - and many other out-of-position welding jobs.

Influence Of Shielding Gas and Arc Voltage

CO2 shielding causes more turbulent wire-to-base plate metal transfer and tends to create a more crowned bead with greater spatter loss.

Argon-based shielding gases provide more stable, uniform wire-to-base plate metal transfer, well-shaped beads, minimal spatter loss and a lower fume generation rate.

Increasing arc voltage tends to increase puddle fluidity, flatten the weld bead, increase edge wetting and increase spatter. Higher voltages also reduce penetration and may cause additional loss of alloying elements.

Spoolarc wires are processed either copper-coated using the proprietary ESAB HI DEP III manufacturing process, or as “bare” (uncoppered) product. Spoolarc wires are available in a variety of alloys, diameters and packages to meet the most demanding customer applications.

Spoolarc wires, either copper-coated or “bare,” provide excellent feedability and arc stability under the roughest shop conditions and most demanding applications even at high wire feed speeds…that means less downtime, greater productivity.

Note: Spoolarc “bare” wires are a standard product for customers requiring or preferring no copper coating.

Why Feedability Is So Improved With ESAB
Spoolarc Wires

All Spoolarc MIG wires are cleaned after the final drawing process to remove residual drawing lubricants and are then treated with a proprietary ESAB process to insure good feeding, arc stability and low weld deposit hydrogen.

Spoolarc HI DEP III (copper-coated) wire has a matte finish with a low (typically 0.05% wt.) copper coating that is thin and tightly adherent - eliminating troublesome copper flaking.

The matte-finish on the Spoolarc wire contrasts with many conventional MIG wires that are “shiny” in appearance. These “shiny” wires do not have any enhanced welding performance. In fact, these wires are generally higher in copper coating level (up to 0.30% wt.) and are prone to copper flaking which detracts from their performance.

Higher tensile strength wire has a greater resistance to “buckling” under compression. ESAB draws most MIG wires directly from rod to final size resulting in a high tensile strength product that resists “birdnesting” when restrictions in the feed system occur.
Excellent Arc Characteristics

Quick starting with Spoolarc wire from ESAB minimizes weld spatter - a common problem with other MIG wires.

Spoolarc wires produce excellent spray arcs at lower voltages, providing precise control of the welding process, lower weld metal hydrogen levels and better penetration.

Spoolarc wires increase contact tip life. ESAB’s proprietary manufacturing process results in better current transfer, less arcing, reduced contact tip erosion - especially at high current and wire feed speeds. Fewer worn out contact tips can mean a sizable saving not only in replacement parts but also in labor and downtime required to change them.

ESAB Spoolarc Wires For Low Hydrogen Welds

Hydrogen normally gets into welds through moisture on the electrode surface, particularly when stick electrodes are used. Spoolarc MIG wires have no absorbent coating and no moisture pickup. Tight control of surface residuals results in a high quality weld with no hydrogen problems. There is no need for drying ovens to recondition electrodes that may have absorbed moisture.
CAUTION: Don’t Forget to Test The Weld
Most of the data in this guide are based on AWS tests performed under standard conditions. In normal practice, however, the results usually differ to the extent that the job conditions differ from the standard. The following factors can affect the results produced by any wire/gas combination:
Base plate chemistry

Base plate thickness

Weld bead size

Dilution of base plate with weld metal

Heat input (affects weld cooling rate)

That is why it is important to test the selected wire/gas combination in the same joint and under the same condition to be used during actual production. Depending on the job, the test may simply be to evaluate welding performance. It may also involve a full check on the weld’s service properties.

Information

Electrodes/Quivers
• Ensure your quivers are always connected to the power supply to avoid moisture pick-up.
• If you find cold electrodes in your quiver please return them to store and take new electrodes.
• Check the condition of the quiver shall be always hot, if not change the quiver. (Temp shall 70 Deg.C)
• Due to the weather the electrodes pick-up moisture and thereby giving weld defects Mainly porosity
• Be sure to return all remaining electrodes after the day work to main store.
• Storing of consumables in toolboxes which is not required for use on the same the day is totally forbidden and not allowed.
• Consumption of filler wire and electrodes should be monitored by each of the welding inspector and welding supervisor.
• During welding always keep your quiver closed for moisture control and for filler wire keep your packet closed for filler wire rust control.

Consumables mix up for Stainless steel electrodes
• The grades of SS materials are being used in the project SS 304,316L and 321(Stamping on the pipe.
• The respective Filler wire/electrodes are SS 308, 316L and 347
• Check always the grade of the material and the filler wire/electrode are matching
• In case doubts ask the inspector available with you on the site.

Earthing and grounding for welders.
• Ensure that the welder use the right earthing as per the material to be welded.
• Do not attach the earthing by welding direct to the pipe.
• Avoiding arc strike is mandatory, if happened doing PT/MT after grinding the affected area.

Seam weld orientation

• check before make any fit up that the seam weld of the pipe more than 45 degree from the bottom of the pipe specially for field run avoiding the seam to intersect with any support will be install later and avoid corrosion of pipe.
• Check the distance between to seam welds is 2 times the thickness of the thicker member at least.

Arc Strike
• Arc strike leads to localize heating and sudden cooling, leading to cracking, which is not acceptable.
• If flange raised face is damaged, the flange will leak during hydro test. The flanged need to be discarded during fabrication and replaced by new one.

Remedies:
• Shall be ground immediately
• Check by “MPI” for defect specially for cracks
• If it is too deep, refer to engineer

Porosity
• Keep a good shield against wind,
• Groove face must be kept clean from grease and liquid.
• All electrodes must be kept inside quivers
• (Quiver is connected to electricity and closes the cover),
• If you use GTAW you must use the suitable gas flow rate
(10 to 20L/min as per WPS)
• Check the Arc Length (Arc length should be within the value of used consumable diameter) and Welding Amperage.

-Handling of the spools.

Improper handling of the spools leads to spool damage (dents, distortion, paint damage …etc) so, we need to avoid such cases that waste the work time if it happened.

A: Handling of painted spools.
Precautions
1) Always use protect wraps while tying lifting belts with D-shackles
2) Use only lifting belts (no wire rope slings shall be used)
3) Place rubber packing on the tie beams where the pipe is going to be erected to avoid damage to painting, while dragging them in to the position.
4) Avoid dragging the pipes on the racks as far as possible to minimize the damage
5) Avoid hitting the pipe in the beams during erection or storing to avoid dents.
6) Place wooden planks tied to the beams while dragging the SS spools to avoid contamination of the pipes.

-Root Inspection by Welder
1) Check the root continuously and request the check by Welding Inspector to check before closing the root.
2) If any fault is noticed, please do the rectification (from inside), if accessible.
3) The availability of the lighting torch with the welders is mandatory for checking.

-Quivers
Due to the summer season we should pay more attention of the quivers.

1) Ensure your quivers are always connected to the power supply to avoid moisture pick-up.
2) If you find cold electrodes in your quiver please return them to store and take new electrodes.
3) Check the quiver is has hot electrodes and quiver is also hot, if not change the quiver.
Due to the weather the electrodes pick-up moisture and thereby giving weld defects such as porosity.

SLAG INCLUSIONS


CAUSES
• when two adjacent beads are deposited without proper over lap
• multi-pass welding with excessive undercuts in weld toe
• uneven profile of the preceding weld runs
• poor welding technique and type of flux (properties)
• access restrictions in doing a weld and cleaning the flux
• poor convex weld bead profile

PREVENTION
• clean the slag between runs by using circular wire brush (cup brush not allowed)
• use correct welding techniques to produce a smooth bead
• plan your sequence of the deposits with proper over lap
• Use the correct current and travel speed to avoid undercutting.

LACK OF FUSION

CAUSES
• narrow joint preparation
• incorrect welding parameter setting
• poor welding technique
• magnetic arc blow
• insufficient cleaning of oily or scaled surface
• LOF mainly appears in the vertical position

PREVENTION
• ensure the joint preparation is wide enough as per joint geometry
• ensure the correct welding parameters(high current, high speed, short arc length is used
• ensure the correct electrode/torch angle is used for manipulation of the arc in the joint
• Use the correct weaving limits

Seam weld orientation
• -check before make any fit up that the seam weld of the pipe at least more than 45 degree from the bottom of the pipe specially for field run avoiding the seam to intersect with any support will be install later.
• -check the distance between to seam welds is 2 times the thickness of the thicker member at least

Deciphering Weld Symbols

Deciphering Weld Symbols


When welds are specified on engineering and fabrication drawings, a cryptic set of symbols is used as a sort of shorthand for describing the type of weld, its size, and other processing and finishing information. The purpose of this page is to introduce you to the common symbols and their meaning. The complete set of symbols is given in a standard published by the American National Standards Institute and the American Welding Society: ANSI/AWS A2.4, Symbols for Welding and Nondestructive Testing.

The structure of the welding symbol

The horizontal line--called the reference line--is the anchor to which all the other welding symbols are tied. The instructions for making the weld are strung along the reference line. An arrow connects the reference line to the joint that is to be welded. In the example above, the arrow is shown growing out of the right end of the reference line and heading down and to the right, but many other combinations are allowed.

Quite often, there are two sides to the joint to which the arrow points, and therefore two potential places for a weld. For example, when two steel plates are joined together into a T shape, welding may be done on either side of the stem of the T.

The weld symbol distinguishes between the two sides of a joint by using the arrow and the spaces above and below the reference line. The side of the joint to which the arrow points is known (rather prosaically) as the arrow side, and its weld is made according to the instructions given below the reference line. The other side of the joint is known (even more prosaically) as the other side, and its weld is made according to the instructions given above the reference line. The below=arrow and above=other rules apply regardless of the arrow's direction. The flag growing out of the junction of the reference line and the arrow is present if the weld is to be made in the field during erection of the structure. A weld symbol without a flag indicates that the weld is to be made in the shop. In older drawings, a field weld may be denoted by a filled black circle at the junction between the arrow and the reference line.

The open circle at the arrow/reference line junction is present if the weld is to go all around the joint, as in the example below.

The tail of the weld symbol is the place for supplementary information on the weld. It may contain a reference to the welding process, the electrode, a detail drawing, any information that aids in the making of the weld that does not have its own special place on the symbol.


Types of welds and their symbols

Each type of weld has its own basic symbol, which is typically placed near the center of the reference line (and above or below it, depending on which side of the joint it's on). The symbol is a small drawing that can usually be interpreted as a simplified cross-section of the weld. In the descriptions below, the symbol is shown in both its arrow-side and other-side positions.

   Fillet Welds                                                

                                                                     


   Groove Welds                       

                                                            





 Plug Welds and SlotWelds

Fillet Welds

 
 
 
The fillet weld (pronounced "fill-it") is used to make lap joints, corner joints, and T joints. As its symbol suggests, the fillet weld is roughly triangular in cross-section, although its shape is not always a right triangle or an isosceles triangle. Weld metal is deposited in a corner formed by the fit-up of the two members and penetrates and fuses with the base metal to form the joint. (Note:for the sake of graphical clarity, the drawings below do not show the penetration of the weld metal. Recognize, however, that the degree of penetration is important in determining the quality of the weld.)

The perpendicular leg of the triangle is always drawn on the left side of the symbol, regardless of the orientation of the weld itself. The leg size is written to the left of the weld symbol. If the two legs of the weld are to be the same size, only one dimension is given; if the weld is to have unequal legs (much less common than the equal-legged weld), both dimensions are given and there is an indication on the drawing as to which leg is longer.
 
                      
 
 
 

The length of the weld is given to the right of the symbol.
 

If no length is given, then the weld is to be placed between specified dimension lines (if given) or between those points where an abrupt change in the weld direction would occur (like at the end of the plates in the example above).


For intermittent welds, the length of each portion of the weld and the spacing of the welds are separated by a dash (length first, spacing second) and placed to the right of the fillet weld symbol.

Notice that the spacing, or pitch, is not the clear space between the welds, but the center-to-center (or end-to-end) distance.

Groove Welds

The groove weld is commonly used to make edge-to-edge joints, although it is also often used in corner joints, T joints, and joints between curved and flat pieces. As suggested by the variety of groove weld symbols, there are many ways to make a groove weld, the differences depending primarily on the geometry of the parts to be joined and the preparation of their edges. Weld metal is deposited within the groove and penetrates and fuses with the base metal to form the joint. (Note: for the sake of graphical clarity, the drawings below generally do not show the penetration of the weld metal. Recognize, however, that the degree of penetration is important in determining the quality of the weld.)


The various types of groove weld are:

Square Groove Welds


The "groove" is created by either a tight fit or a slight separation of the edges. The amount of separation, if any, is given on the weld symbol.

V-Groove Welds


The edges of both pieces are chamfered, either singly or doubly, to create the groove. The angle of the V is given on the weld symbol, as is the separation at the root (if any).

If the depth of the V is not the full thickness--or half the thickness in the case of a double V--the depth is given to the left of the weld symbol.

If the penetration of the weld is to be greater than the depth of the groove, the depth of the effective throat is given in parentheses after the depth of the V.

Bevel Groove Weld

The edge of one of the pieces is chamfered and the other is left square. The bevel symbol's perpendicular line is always drawn on the left side, regardless of the orientation of the weld itself.The arrow points toward the piece that is to be chamfered. This extra significance is emphasized by a break in the arrow line. (The break is not necessary if the designer has no preference as to which piece gets the edge treatment or if the piece to receive the treatment should be obvious to a qualified welder.) Angle and depth of edge treatment, effective throat, and separation at the root are described using the methods discussed in the V-groove section.

U-Groove Weld

The edges of both pieces are given a concave treatment. Depth of edge treatment, effective throat, and separation at the root are described using the methods discussed in the V-groove section.

J-Groove Weld

The edge of one of the pieces is given a concave treatment and the other is left square. It is to the U-groove weld what the bevel groove weld is to the V-groove weld. As with the bevel, the perpendicular line is always drawn on the left side and the arrow (with a break, if necessary) points to the piece that receives the edge treatment. Depth of edge treatment, effective throat, and separation at the root are described using the methods discussed in the V-groove section.

Flare-V Groove Weld

Commonly used to join two round or curved parts. The intended depth of the weld itself are given to the left of the symbol, with the weld depth shown in parentheses.

Flare Bevel Groove Weld
Commonly used to join a round or curved piece to a flat piece. As with the flare-V, the depth of the groove formed by the two curved surfaces and the intended depth of the weld itself are given to the left of the symbol, with the weld depth shown in parentheses. The symbol's perpendicular line is always drawn on the left side, regardless of the orientation of the weld itself.

Common supplementary symbols used with groove welds are the melt-thru and backing bar symbols. Both symbols indicate that complete joint penetration is to be made with a single-sided groove weld. In the case of melt-thru, the root is to be reinforced with weld metal on the back side of the joint. The height of the reinforcement, if critical, is indicated to the left of the melt-thru symbol, which is placed across the reference line from the basic weld symbol.

When a backing bar is used to achieve complete joint penetration, its symbol is placed across the reference line from the basic weld symbol. If the bar is to be removed after the weld is complete,an "R" is placed within the backing bar symbol. The backing bar symbol has the same shape as the plug or slot weld symbol, but context should always make the symbol's intention clear.

Plug and Slot Welds

Plug welds and slot welds are used join overlapping members, one of which has holes (round for plug welds, elongated for slot welds) in it. Weld metal is deposited in the holes and penetrates and fuses with the base metal of the two members to form the joint. (Note: for the sake of graphical clarity, the drawings below do not show the penetration of the weld metal. Recognize, however, that the degree of penetration is important in determining the quality of the weld.) For plug welds, the diameter of each plug is given to the left of the symbol and the plug-to-plug spacing (pitch) is given to the right. For slot welds, the width of each slot is given to the left of the symbol, the length and pitch (separated by a dash) are given to the right of the symbol, and a detail drawing is referenced in the tail. The number of plugs or slots is given in parentheses above or below the weld symbol. The arrow-side and other-side designations indicate which piece contains the hole(s). If the hole is not to be completely filled with weld metal, the depth to which it is to be filled is given within the weld symbol.

For more information, see ANSI/AWS A2.4, Symbols for Welding and Nondestructive Testing.


SOURCE FROM
Weld Procedures Article Directory