Free Certified Welder Base and Filler Metals Questions and Answers 1 — Questions and Answers
Question 1: In the AWS classification E7018 for a shielded metal arc welding (SMAW) electrode, what does the '1' signify?
- The type of flux coating and current.
- The minimum tensile strength in ksi.
- The welding position capability. (Correct answer)
- Its suitability for AC current only.
Correct answer: The welding position capability.
In the AWS A5.1 standard for carbon steel electrodes, the third digit indicates the welding position. A '1' signifies the electrode is suitable for all positions (Flat, Horizontal, Vertical, Overhead). The '70' indicates 70,000 psi tensile strength, and the '8' indicates the coating type (low-hydrogen, iron powder) and current.
Question 2: A welder is tasked with joining a 1-inch thick A36 carbon steel plate to an equal thickness of 304 stainless steel plate. Which filler metal is specifically designed for this type of dissimilar metal application?
- E6010
- ER4043
- ER309L (Correct answer)
- E70S-2
Correct answer: ER309L
ER309L is specifically formulated for welding austenitic stainless steels to carbon or low-alloy steels. Its higher alloy content prevents the formation of brittle microstructures at the weld interface, which would occur if a carbon steel filler were used. ER4043 is for aluminum, and E6010/E70S-2 are for carbon steel.
Question 3: Which of the following is the primary reason for storing E7018 low-hydrogen electrodes in a temperature-controlled oven after opening the sealed container?
- To burn off any oil or grease contaminants from manufacturing.
- To prevent the flux coating from absorbing atmospheric moisture. (Correct answer)
- To make the electrodes easier to strike an arc with.
- To increase the electrical conductivity of the flux coating.
Correct answer: To prevent the flux coating from absorbing atmospheric moisture.
The flux coating on low-hydrogen electrodes is hygroscopic, meaning it readily absorbs moisture. This moisture can introduce hydrogen into the weld pool, leading to hydrogen-induced cracking, a serious weld defect. Storing them in a heated rod oven keeps them dry and maintains their low-hydrogen properties.
Question 4: What is the primary effect of increasing the carbon content in a steel base metal on its weldability?
- It improves corrosion resistance, making the weld cleaner.
- It decreases the metal's melting point, requiring lower amperage.
- It increases hardness and strength, making it more susceptible to cracking. (Correct answer)
- It makes the metal more ductile and forgiving of procedural variations.
Correct answer: It increases hardness and strength, making it more susceptible to cracking.
Carbon is the principal hardening element in steel. As carbon content increases, the steel becomes harder and stronger but also less ductile. This increased hardness makes it more prone to cracking in the heat-affected zone (HAZ) during the rapid cooling cycle of welding, thus decreasing its overall weldability and often requiring preheat.
Question 5: A welder must perform a repair on a heavy cast iron machine housing. To ensure a successful weld and prevent the base metal from cracking, what is the MOST critical step?
- Applying a significant preheat to the area around the repair. (Correct answer)
- Using a high travel speed to minimize heat input.
- Cooling the weld rapidly with a water quench.
- Selecting a filler metal with a lower tensile strength than the base metal.
Correct answer: Applying a significant preheat to the area around the repair.
Cast iron has high carbon content, making it brittle and highly susceptible to cracking from thermal stresses induced by welding. Preheating the base metal to a specific temperature before welding slows the cooling rate of the weld and the heat-affected zone, which significantly reduces thermal stress and helps prevent cracking.
Question 6: In the common GMAW filler metal classification ER70S-6, what do the 'S' and the '-6' signify respectively?
- Submerged arc, 60 psi shielding gas pressure.
- Stainless, requires 6% carbon dioxide in the shielding gas.
- Shielded, for use on steel with 0.6% silicon.
- Solid wire, and the chemical composition/level of deoxidizers. (Correct answer)
Correct answer: Solid wire, and the chemical composition/level of deoxidizers.
In the AWS A5.18 classification, 'ER' means the filler can be used as an Electrode or a Rod. '70' is the minimum tensile strength (70,000 psi). 'S' indicates it is a Solid wire. The final digit, '-6', indicates the chemical composition, specifically the amount of silicon and manganese deoxidizers. The -6 wire has higher levels of these deoxidizers than a -2 or -3, making it better for welding over light rust or mill scale.
Free Certified Welder Base and Filler Metals Questions and Answers 1
In the AWS classification E7018 for a shielded metal arc welding (SMAW) electrode, what does the '1' signify?