Welding Basics
108 flashcards by MentisLibrary
Stick, MIG, and TIG compared honestly, plus electrode classifications, joint types, welding positions, blueprint symbols, and how to read a defect back to its cause. Cylinder and arc safety included throughout.
- What does the abbreviation SMAW stand for, and what is it commonly called?
- Shielded Metal Arc Welding, commonly called stick welding or manual metal arc welding.
- Why is stick welding still preferred for outdoor field work?
- Its shielding comes from the burning flux rather than a bottled gas, so wind does not blow the shield away.
- What does GMAW stand for, and what is its shop name?
- Gas Metal Arc Welding, known as MIG welding.
- What does GTAW stand for, and what is its shop name?
- Gas Tungsten Arc Welding, known as TIG welding or heliarc.
- What is FCAW and how does it differ from solid wire MIG?
- Flux Cored Arc Welding uses a tubular wire filled with flux instead of a solid wire.
- When would you choose self shielded flux core over solid wire MIG?
- Outdoors, in wind, or on dirty or rusty structural steel where a gas shield would be lost or contaminated.
- What is oxyfuel welding and cutting?
- A process that burns a fuel gas with oxygen to produce a flame hot enough to melt steel, or to preheat steel and then oxidize it away with a stream of pure oxygen.
- How does plasma arc cutting work?
- Compressed gas is forced through a constricted nozzle and ionized by an arc, producing a very hot high velocity plasma jet that melts the metal and blows it out of the kerf.
- What is the difference between a constant current and a constant voltage welding power supply?
- Constant current holds amperage roughly steady as arc length varies, while constant voltage holds voltage steady and lets current change with wire feed speed.
- What does DCEN mean, and what is its effect on the weld?
- Direct Current Electrode Negative, also called straight polarity. The electrode is negative and the work is positive.
- What does DCEP mean, and when is it used?
- Direct Current Electrode Positive, also called reverse polarity. The electrode is positive and the work is negative.
- Why is AC used for TIG welding aluminum?
- The electrode positive half cycle blasts off the tenacious aluminum oxide layer while the electrode negative half cycle puts heat into the base metal.
- What is duty cycle on a welding machine?
- The percentage of a ten minute period that a machine can weld at a given output without overheating.
- What is open circuit voltage (OCV)?
- The voltage present at the output terminals when the machine is on but no arc is drawn.
- In the electrode classification E7018, what does the 70 mean?
- A minimum tensile strength of 70,000 psi in the deposited weld metal.
- In E7018, what does the third digit (1) indicate?
- The welding positions the electrode is suitable for. A 1 means all positions.
- In E7018, what does the fourth digit (8) indicate?
- The coating type and the current the electrode runs on. An 8 is a low hydrogen potassium iron powder coating that runs on AC or DCEP.
- What makes E7018 a low hydrogen electrode, and why does that matter?
- Its coating is formulated and baked to contain very little moisture, so little hydrogen enters the weld metal.
- What is E6010 known for, and where is it used?
- A deep penetrating, fast freezing cellulosic electrode that runs on DCEP and digs through mill scale and light contamination.
- What does ER70S-6 designate?
- A solid steel MIG wire with 70,000 psi minimum tensile strength; the S means solid and the 6 identifies the chemistry.
- What is the practical difference between E71T-1 and E71T-11 flux cored wire?
- E71T-1 is a dual shield wire that requires an external shielding gas, while E71T-11 is self shielded and needs no gas.
- Which tungsten electrode type is the general purpose modern choice for both AC and DC TIG?
- Lanthanated tungsten, usually 2 percent lanthanated with a blue band.
- Why has 2 percent thoriated tungsten fallen out of favor despite its good DC performance?
- Thorium is mildly radioactive, so grinding it produces radioactive dust.
- Which way should a tungsten electrode be ground, and why?
- Lengthwise, with the grinding marks running along the axis of the electrode toward the point.
- What tungsten tip shape is used for DC steel TIG versus AC aluminum TIG?
- DC work uses a sharpened point for a focused arc. AC aluminum work uses a blunted point or a balled end because the electrode gets much hotter.
- What shielding gas is used for TIG welding, and why?
- Pure argon, because it is completely inert and will not react with the tungsten or the puddle.
- What is the effect of using 100 percent CO2 as a MIG shielding gas?
- Deeper penetration and lower cost, but a harsher globular arc with much more spatter and no true spray transfer.
- What does a 75/25 argon carbon dioxide blend give you in MIG welding?
- A stable arc with far less spatter than straight CO2 and a flatter bead, at the cost of some penetration.
- Why must you use pure argon rather than an argon CO2 blend when MIG welding aluminum?
- CO2 breaks down at arc temperature and its oxygen contaminates the aluminum weld, and aluminum needs the fully inert shield.
- Name the five basic joint types in welding.
- Butt, lap, tee, corner, and edge.