75 Questions
What creates the arc in shielded metal arc welding?
The flow of electricity between the electrode and the workpiece
What is the function of the slag in shielded metal arc welding?
To cover the solidified weld metal
What do American Welding Society Specifications A5.1 and A5.5 describe?
Requirements for carbon and low alloy steel electrodes
What assists the flux in shielding the molten metal in the arc region?
Shielding gas produced from the electrode coating
What type of power source is used for shielded metal arc welding?
Constant current power source with a 'drooping' characteristic
What is connected to the piece to be welded in shielded metal arc welding?
Grounding clamp
What is one of the limitations of shielded metal arc welding?
Speed due to the need to periodically stop welding and replace the consumed electrode
What causes porosity in the finished weld in shielded metal arc welding?
Presence of moisture or contamination in the weld region
What is the role of the alpha-numeric suffix in SMAW electrodes for low alloy steels?
Addition to the standard designation
What equipment is included in shielded metal arc welding?
Transformer-rectifier and inverter power supply
Which welding process uses a solid wire electrode fed through a welding gun to create an arc?
Gas metal arc welding (GMAW)
What is the common problem in manual welding caused by the development of a magnetic field when electric current passes through a conductor?
Arc blow
When does the resistance in the welding circuit increase in shielded metal arc welding?
As the welder increases arc length
What can gas metal arc welding (GMAW) use for welding, often using carbon dioxide alone due to its lower cost?
Inert and reactive gases
What is a limitation of shielded metal arc welding related to the layer of solidified slag?
The layer of solidified slag must be removed after welding
What are the alternatives to reduce the effects of arc blow in shielded metal arc welding?
Changing from DC to AC, holding a short arc, reducing welding current, and angling the electrode
What can arc blow cause in addition to porosity?
All of the above
Why is shielded metal arc welding still popular in many industries?
Due to its simplicity, versatility, and portability
What can occur in shielded metal arc welding due to the flux system used for weld protection?
Slag inclusions
What is the characteristic of the magnetic field in shielded metal arc welding?
Strongest when contained entirely within a magnetically permeable material
How are gas metal arc welding electrodes identified?
By the letters 'ER'
What has shielded metal arc welding been replaced by in many applications?
Other processes due to increased productivity
What does the prefix 'ER' denote in gas metal arc welding electrode identification?
Electrode and a rod
What is gas metal arc welding commonly referred to as?
MIG welding
What type of power source does gas metal arc welding use?
Constant voltage
What type of current is normally used for gas metal arc welding?
Direct current, electrode positive (DCEP)
What do the letters 'ER' followed by numbers indicate in gas metal arc welding electrodes?
Minimum tensile strength and chemical composition
What does the 'E' in electrode designation stand for?
Electrode
What does the first two or three digits in electrode designation represent?
Tensile strength in thousands of pounds per square inch
What does the last digit in electrode designation signify?
Characteristics determined by the composition of the coating
What does the number following the tensile strength designation indicate?
Positions in which the electrode can be used
What does the dry electrode coating decompose to form when an arc is struck?
Gaseous shield
How are the metal droplets transferred across the arc?
Magnetic pinch effect
What is the significance of the last digit in the Shielded Metal Arc Welding (SMAW) electrode identification system?
Classifications and corresponding current, arc, and covering & slag characteristics
How should 'low hydrogen' type electrodes be stored to maintain low moisture content?
In their original factory-sealed metal container or an acceptable storage oven
What is the welding arc created between?
The end of the electrode and the workpiece
Why is it crucial to note that electrodes other than those specified may be damaged if placed in the oven?
Their operating characteristics depend on a certain moisture level
What type of core wire is used for all carbon and low alloy steel electrodes?
Low carbon, rimmed steel core wire
What does the number '4' following the tensile strength designation indicate?
Suitability for welding in a downhill progression
What are the primary deoxidizers found in gas metal arc electrodes?
Manganese, silicon, and aluminum
What components are included in a complete gas metal arc welding setup?
Power source, wire feeder, gas source, and welding gun
What happens to the welding current as the wire feed speed is increased in gas metal arc welding?
It increases
What controls the melt-off rate of the electrode in gas metal arc welding?
Wire feed speed
Why is it important to store the gas metal arc welding wire properly when not in use?
To prevent contamination with rust, oil, moisture, or other materials
What type of metal transfer is considered to be the hottest in gas metal arc welding?
Spray transfer
Which metal transfer mode is best for welding of sheet metal and joints with excessive gaps?
Short circuiting transfer
What characteristic makes pulsed arc gas metal arc welding a semi-automatic type of process?
The alternating high and low currents
What is the primary contribution of the core of metal cored welding wire to the deposited weld metal?
Almost entirely to the deposited weld metal
What happens when the gun is moved closer to the workpiece in gas metal arc welding?
Reduces the electrical resistance and produces an instantaneous increase in current
What effect does shielding gas have on the type of metal transfer in gas metal arc welding?
Significant effect
What is the primary advantage of spray transfer in gas metal arc welding?
Best for heavier sections and full penetration weld joints
Which equipment is NOT included in gas metal arc welding setup?
Flux
What is the primary function of deoxidizers like manganese, silicon, and aluminum in gas metal arc electrodes?
Prevent porosity
What do adjustments for voltage and wire feed speed control in gas metal arc welding?
Welding current and melt-off rate
What is the primary purpose of proper storage of the wire in gas metal arc welding?
Prevent contamination by rust, oil, or moisture
What drastically alters the operating characteristics of the power source in gas metal arc welding?
Machine adjustments
In gas metal arc welding, which mode of metal transfer provides the hottest heat to the workpiece?
Spray
What is pulsed arc gas metal arc welding suitable for?
Thin sheet metal welding
What significantly impacts the type of metal transfer in gas metal arc welding?
Shielding gases
What type of metal transfer is suitable for welding sheet metal and joints with excessive gaps due to poor fit up in gas metal arc welding?
Short circuiting
What type of power source is required for pulsed arc gas metal arc welding?
Capable of producing pulsing direct current output
In gas metal arc welding, what do shielding gases significantly impact?
Type of metal transfer
What is the primary role of the welding gun in gas metal arc welding?
Direct the electrode to the workpiece
What equipment is included in gas metal arc welding?
Power source, wire feeder, gas source, and welding gun
What do gas metal arc welding electrodes contain to prevent porosity?
Manganese, silicon, and aluminum
What does the wire feed speed determine in gas metal arc welding?
Welding current and melt-off rate of electrode
What is the hottest metal transfer mode in gas metal arc welding, suitable for heavier sections and full penetration weld joints?
Spray transfer
What is the coldest metal transfer mode in gas metal arc welding, suitable for sheet metal and joints with excessive gaps?
Short circuiting transfer
What does proper storage of wire in gas metal arc welding aim to prevent?
Contamination
What do machine adjustments significantly alter in gas metal arc welding?
Operating characteristics
What does the metal transfer mode in gas metal arc welding depend on?
Shielding gas, current, voltage levels, and power source characteristics
What does pulsed arc welding allow precise control over?
Heat and process flexibility
What has a significant impact on the type of metal transfer in gas metal arc welding?
Shielding gases
What is the equipment for gas metal arc welding that the welder adjusts to set up for welding?
Voltage at power source and wire feed speed at wire feeder
What determines the welding current and melt-off rate of the electrode in gas metal arc welding?
Wire feed speed
Study Notes
Shielded Metal Arc Welding Electrode Identification System
- Electrodes are identified by an "E" followed by four or five digits, where the first two or three digits represent the minimum tensile strength of the deposited weld metal in thousands of pounds per square inch.
- For example, E7018 indicates a minimum tensile strength of 70,000 psi, while E12018 represents a minimum tensile strength of 120,000 psi.
- The electrode is made up of a metal core wire covered with a layer of granular flux held in place by a bonding agent, and all carbon and low alloy steel electrodes use a low carbon, rimmed steel core wire.
- The last digit in the electrode designation signifies characteristics determined by the composition of the coating present on the electrode, such as operating characteristics and recommended electrical current.
- The number following the tensile strength designation indicates the positions in which the electrode can be used, with "1" indicating suitability for use in any position, "2" for flat and horizontal positions, and "4" for welding in a downhill progression.
- The dry electrode coating is a nonconductor of electricity, but when an arc is struck, it decomposes to form a gaseous shield, remove impurities, provide additional alloying elements, improve electrical characteristics, and provide an insulating blanket.
- The metal droplets are transferred across the arc by a magnetic pinch effect, induced by the circular magnetic field in the conductor as current is passed through it.
- The significance of the last digit of the Shielded Metal Arc Welding (SMAW) electrode identification system is detailed in Table 3.1, which includes classifications and corresponding current, arc, and covering & slag characteristics.
- Electrodes ending in "5," "6," or "8" are classified as "low hydrogen" types and must be stored in their original factory-sealed metal container or an acceptable storage oven to maintain low moisture content.
- Steel alloy suffixes for SMAW electrodes are listed in Table 3.2, along with the major alloy elements they represent.
- The welding arc is created between the end of the electrode and the workpiece, melting the metal when they are brought close together.
- It is crucial to note that electrodes other than those specified may be damaged if placed in the oven, as their operating characteristics depend on a certain moisture level.
Gas Metal Arc Welding Process Overview
- Gas metal arc electrodes contain deoxidizers like manganese, silicon, and aluminum to prevent porosity
- Equipment for gas metal arc welding includes power source, wire feeder, gas source, and welding gun
- Welder adjusts voltage at power source and wire feed speed at wire feeder to set up for welding
- Wire feed speed determines welding current and melt-off rate of electrode
- Proper storage of wire is crucial to prevent contamination
- Machine adjustments significantly alter operating characteristics
- Four basic modes of metal transfer in gas metal arc welding: spray, globular, pulsed arc, and short circuiting
- Metal transfer mode depends on factors like shielding gas, current, voltage levels, and power source characteristics
- Spray transfer is hottest and best for heavier sections and full penetration weld joints
- Pulsed arc welding allows precise control over heat and process flexibility
- Short circuiting transfer is the coldest and suitable for sheet metal and joints with excessive gaps
- Shielding gases have a significant impact on the type of metal transfer
Test your knowledge of Shielded Metal Arc Welding (SMAW) electrode identification with this quiz. Explore the system of electrode numbering, characteristics, and applications, and enhance your understanding of electrode types and storage requirements.
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