120103a-bB Wire Feed Welding Equipment and Consumables Part B Flashcards
Wire Feed Welding Equipment and Consumables : Part B
Define and describe the GMAW process in detail.
Answer: GMAW is an arc welding process that uses an arc between a continuous filler metal electrode and the weld pool. The process uses shielding gas from an externally supplied source.
Explanation: Gas Metal Arc Welding (GMAW), also known as MIG welding, involves creating an electric arc between a continuous wire electrode and the workpiece, which melts the wire to form a weld. Shielding gas protects the weld pool from atmospheric contamination, ensuring a clean weld.
What type of welding power source is most often used for GMAW?
Answer: Constant voltage (CV).
Explanation: GMAW typically uses a constant voltage power source, which maintains a steady voltage level during welding. This helps in creating a stable arc and consistent welding conditions, essential for quality welds.
List three advantages and three disadvantages of GMAW.
Any three (3) of the following advantages are correct.
a) Lower skill requirements than SMAW
b) Excellent for light gauge metals
c) Good arc control when working with poor fit-ups
d) Less heat input means less distortion than SMAW
e) High production rates
f) No slag to remove, little or no post-weld clean-up
Any three (3) of the following disadvantages are correct.
a) Special equipment required resulting in the higher initial cost
b) Equipment requires more maintenance and down time
c) Lack of fusion can be a problem
d) Cannot be used outdoors or in drafty locations
e) High radiant energy requires protection for the welder and others in the
vicinity
f) Wire feeder must be in close proximity to the welding
Explanation: GMAW offers several benefits like high efficiency and ease of use, but it also has limitations such as higher costs and specific environmental requirements. Understanding these can help in choosing the right welding process for different applications.
Interpret the B-G 49A 3 C G2 electrode classification.
Answer and Explanation:
B-G 49A 3 C G2 is a classification that breaks down into several components:
B: Indicates the electrode was classified by tensile strength and with an average 27-joule impact test.
G: Designates using a gas shielded metal arc welding process.
49A: Refers to the minimum tensile strength of the deposited weld metal in the as-welded condition in megapascals (MPa) divided by 10.
3: Indicates a minimum temperature of -30°C for impact tests.
C: Designates CO2 as the shielding gas.
G2: Specifies a particular chemical analysis of the designated filler metal.
This classification system provides detailed information about the properties and suitable applications of the electrode, crucial for selecting the right filler metal for specific welding tasks. Understanding these classifications ensures that welders use materials that meet the necessary strength, impact resistance, and shielding requirements for their specific welding applications.
Describe the operating principles of FCAW.
Answer: FCAW uses an arc established between a continuously fed consumable electrode and the workpiece. Appropriate settings made by the operator maintain a constant burn-off rate of the wire electrode. The arc length is maintained automatically depending on the power source and wire drive system used. Shielding gas can be externally applied and/or obtained from a flux within the hollow electrode core.
Explanation: Flux Cored Arc Welding (FCAW) combines the simplicity of MIG welding with the added efficiency of a flux core. This allows for increased penetration and a higher welding speed than MIG welding. The flux in the core of the wire automatically provides the shielding gas, making FCAW particularly useful for outdoor welding where wind can disperse the shielding gas in conventional MIG welding.
What is the electrode extension range for self-shielded FCAW?
Answer: For self-shielded electrodes, extensions range from 19 mm to 95 mm (¾” to 3¾”).
Explanation: The electrode extension in FCAW, especially in self-shielded applications, is important for ensuring proper arc stability and weld penetration. Longer extensions are typically used in self-shielded FCAW to allow for better flux coverage and gas shielding produced from the flux core.
List three advantages and three disadvantages of FCAW.
Any three (3) of the following advantages are correct.
a) The deposition rate is up to four times greater than with SMAW.
b) There is a high operating factor, so it is easily mechanized.
c) The visible arc is easy to use.
d) The weld metal deposits are high quality.
Any three (3) of the following disadvantages are correct.
a) The equipment is more expensive to purchase than that needed for SMAW.
b) More smoke and fumes are generated, which require suitable exhaust
removal equipment.
c) The wire feeder must be in close proximity to the welding.
d) Equipment is more complex than SMAW, requiring more maintenance.
Explanation: FCAW offers a high deposition rate, making it efficient for industrial uses, and its automated nature leads to consistent weld quality. However, the cost of equipment and maintenance, along with environmental considerations like fume extraction, can be challenging.
What are the primary functions of the flux in FCAW wires?
Answer: The primary functions include providing deoxidizers and scavengers to remove impurities, forming a slag cover to protect the weld metal from atmospheric contamination, acting as an arc stabilizer for a stable arc with less spatter, adding alloying elements for desired mechanical and metallurgical properties, and generating shielding gas to displace atmospheric air.
Explanation: The flux in FCAW wires serves multiple critical roles, from protecting the weld pool to stabilizing the arc and even contributing to the metallurgical properties of the weld. Its multifunctionality makes FCAW versatile and effective in various welding applications.
Name two FCAW wires that can be used without external gas shielding.
Answer: Any of the following types are correct: EXXXT-3, -4, -6, -10, -11, -13, or -14.
Explanation: These specific types of FCAW wires are designed to produce their own shielding gas from the flux, making them suitable for outdoor applications or in environments where external gas shielding is impractical.
Explain the E491T-9CH FCAW electrode wire classification.
Answer: ‘E’ indicates electrode. ‘49’ indicates tensile strength measured in megapascals divided by 10. ‘1’ refers to all-position application. ‘T’ indicates tubular wire. ‘9’ indicates the slag system, current, polarity, and shielding gas. ‘CH’ refers to controlled hydrogen.
Explanation: This classification system provides detailed information about the electrode’s characteristics, including its mechanical strength, suitable positions for welding, type of wire (tubular), and the specific slag system and shielding gas requirements. Understanding these classifications is essential for selecting the appropriate wire for a given welding task.
Explain the E491C-6 MCAW electrode wire classification.
Answer: E indicates electrode. 49 refers to the minimum tensile strength of the deposited weld metal in the as-welded condition in megapascals (MPa) divided by 10. 1 refers to all-position application. C indicates metal-cored wire. 6 indicates the slag system, current, polarity, and shielding gas.
Explanation: The classification E491C-6 for MCAW electrode wire provides detailed information about the electrode’s characteristics:
E for electrode.
49 for the tensile strength of the weld metal.
1 for its suitability for all-position welding.
C signifies that it’s a metal-cored wire.
6 relates to the wire’s slag system, current requirements, polarity, and the type of shielding gas to be used.
List three (3) advantages and three (3) disadvantages of MCAW.
Any three (3) of the following advantages are correct.
a) The deposition rate is up to four times greater than with SMAW.
b) There is a high operating factor, so it is easily mechanized.
c) There is no slag or inter-pass cleaning.
d) The weld metal deposits are high quality.
Any three (3) of the following disadvantages are correct.
a) The equipment is more expensive to purchase than that needed for SMAW.
b) More smoke and fumes are generated, which require suitable exhaust
removal equipment.
c) The wire feeder must be in close proximity to the welding.
d) Equipment is more complex than SMAW, requiring more maintenance.
Explanation: Metal Cored Arc Welding (MCAW) is known for its high efficiency and quality of welds, but it comes with higher equipment costs and maintenance needs. The wire feeder’s proximity can also be a limitation in certain welding setups.
What is the recommended mix of shielding gases for the C-3 and C-6 electrode classifications used for MCAW?
Answer: The recommended mix for both classifications is 85% Argon and 15% CO2.
Explanation: This particular mix of Argon and CO2 is commonly used in MCAW for the C-3 and C-6 classifications. It provides a good balance between weld quality, arc stability, and cost-effectiveness.
What need is increased when using shielding gases for wire feed processes?
a) The need for good lighting.
b) The need for good ventilation.
c) The need for heat shielding.
d) The need for eye protection.
b) The need for good ventilation. (Correct Answer)
Explanation: Good ventilation is essential when using shielding gases to prevent the build-up of harmful fumes and gases in the welding area, ensuring a safe working environment.
High ultraviolet radiation emissions from an open arc can cause atmospheric oxygen in the vicinity of the arc to convert to which of the following?
a) Ozone.
b) Carbon monoxide.
c) Carbon dioxide.
d) Argon.
a) Ozone. (Correct Answer)
What is a potential source of poisonous chemical fumes when welding?
a) Inert shielding gases.
b) Chlorinated degreasing solvents.
c) Carbon dioxide extinguishers.
d) Anti-spatter nozzle sprays.
b) Chlorinated degreasing solvents. (Correct Answer)
Explanation: Chlorinated degreasing solvents can release poisonous chemical fumes when exposed to the high temperatures of welding, posing health hazards.
What is the gas metal arc welding process also known as?
a) MIG welding.
b) Flux cored arc welding.
c) Self-shielding process.
d) Shielded metal arc welding.
a) MIG welding. (Correct Answer)
Explanation: Gas Metal Arc Welding (GMAW) is commonly known as MIG (Metal Inert Gas) welding, a term that originated from its use of inert gases like argon and helium.
GMAW is recommended for use on which of the following metals?
a) Stainless steel.
b) Aluminum.
c) Copper alloys.
d) Carbon and low alloy steels.
e) All the above.
e) All the above. (Correct Answer)
Explanation: GMAW is versatile and effective for a wide range of metals, including stainless steel, aluminum, copper alloys, and carbon and low alloy steels.
What is the gas generated from that is used for self-shielded FCAW?
a) The base metal.
b) An external source.
c) The flux.
d) A paste flux applied to the base metal before welding.
c) The flux. (Correct Answer)
Explanation: In self-shielded Flux-Cored Arc Welding (FCAW), the flux within the wire generates the shielding gas necessary for the welding process.
The MCAW process uses the same equipment as which process?
a) SMAW.
b) GTAW.
c) FCAW.
d) OAW.
c) FCAW. (Correct Answer)
Explanation: Metal-Cored Arc Welding (MCAW) uses similar equipment to Flux-Cored Arc Welding (FCAW), including wire feeders, power sources, and gun and cable assemblies.
What is the gun shown in Figure 16 primarily used for?
Answer: Welding aluminum.
Explanation: The specific design and features of the gun shown in Figure 16 make it ideal for welding aluminum, a metal that requires particular handling due to its properties.
