MTTC Welding Trade Test flashcards
MTTC Welding Trade Test · Build recall with a focused review session.
32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Acetylene pressure limit
- Acetylene cylinders must not be used at pressures above 15 psig because free acetylene can decompose explosively at higher pressures.
- Hexavalent chromium TLV
- The threshold limit value for hexavalent chromium fume is 0.005 mg/m3 as an 8-hour time-weighted average; welding stainless steel can produce this fume.
- Confined space oxygen range
- Atmospheric oxygen in a confined space must be between 19.5% and 23.5% before entry; outside this range, entry is prohibited without respiratory protection.
- Constant-current power source
- A constant-current (drooping) power source maintains a relatively steady amperage as voltage varies; it is used for SMAW and GTAW.
- Constant-voltage power source
- A constant-voltage power source maintains a steady voltage while amperage varies with wire feed speed; it is used for GMAW and FCAW.
- Duty cycle
- The duty cycle is the percentage of a 10-minute period that a welding machine can operate at its rated output without overheating; a 60% duty cycle allows 6 minutes of welding.
- Spray transfer transition current
- Spray transfer in GMAW occurs above a transition current, typically 200-250 A for 0.035 in. wire, where metal transfers as fine droplets.
- Arrow side vs other side
- On a welding symbol, a weld symbol below the reference line indicates the arrow side; a symbol above the reference line indicates the other side.
- All-around weld symbol
- A circle placed at the junction of the reference line and arrow line indicates that the weld is to be made all around the joint.
- Field weld symbol
- A flag at the junction of the reference line and arrow line indicates a field weld, meaning the weld is to be made at the job site rather than in the shop.
- Fillet weld symbol dimensions
- On a fillet weld symbol, the leg size is placed to the left of the triangle, and the length and pitch are placed to the right.
- Carbon equivalent formula
- Carbon equivalent (CE) = %C + %Mn/6 + (%Cr + %Mo + %V)/5 + (%Ni + %Cu)/15; a CE above 0.40 increases hardenability and cracking risk.
- Heat-affected zone
- The heat-affected zone (HAZ) is the base metal that has been metallurgically altered by welding heat but not melted; it is often the weakest region in high-strength steels.
- Sensitization of stainless steel
- Austenitic stainless steel is sensitized when heated between 800°F and 1500°F, causing chromium carbide precipitation at grain boundaries and reducing corrosion resistance.
- Hydrogen-induced cracking
- Hydrogen-induced cracking (cold cracking) occurs when diffusible hydrogen, residual stress, and a susceptible microstructure such as martensite are present; low-hydrogen electrodes and preheat reduce risk.
- Five basic joint types
- The five basic joint types are butt, lap, tee, corner, and edge; each describes the configuration of the members being joined.
- Single-V groove angle
- A single-V groove weld typically has an included groove angle of 60° to 75° and a root opening of 1/16 to 1/8 in. for complete penetration.
- Root face (land)
- The root face, or land, is the unmelted portion of the groove face at the root; it is typically 1/16 to 1/8 in. and helps prevent burn-through.
- Backing gas
- A backing gas, such as argon, is used on the root side of a GTAW weld in stainless steel or titanium to prevent oxidation of the hot root surface.
- WPS and PQR
- A Welding Procedure Specification (WPS) is a written document providing welding parameters; it must be supported by a Procedure Qualification Record (PQR) that documents the qualification test.
- Essential variable
- An essential variable is a welding parameter, such as process, base metal thickness, or filler metal classification, that requires requalification of the WPS if changed.
- AWS D1.1 scope
- AWS D1.1 Structural Welding Code-Steel governs welding of carbon and low-alloy steel structures and defines prequalified joints and qualification requirements.
- Welder performance qualification
- A welder performance qualification (WPQ) tests a welder's ability to produce sound welds; it is separate from the WPS/PQR procedure qualification.
- Liquid penetrant testing
- Liquid penetrant testing (PT) detects surface-breaking discontinuities in nonporous materials; it is not suitable for porous materials such as cast iron.
- Magnetic particle testing
- Magnetic particle testing (MT) detects surface and near-surface discontinuities in ferromagnetic materials; it cannot be used on austenitic stainless steel or aluminum.
- Ultrasonic testing
- Ultrasonic testing (UT) uses high-frequency sound waves to detect internal discontinuities; it requires a coupling medium and a skilled operator.
- Charpy V-notch test
- The Charpy V-notch impact test measures the toughness of a weld or HAZ at a specified temperature; it is required where brittle fracture is a concern.
- Oxyfuel cutting preheat
- Oxyfuel cutting uses a preheat flame to bring steel to its ignition temperature, approximately 1600°F (870°C), before an oxygen jet oxidizes the metal.
- Plasma arc cutting
- Plasma arc cutting uses a constricted arc and high-velocity gas to cut electrically conductive materials, including stainless steel and aluminum.
- Brazing temperature range
- Brazing occurs at temperatures above 840°F (450°C) but below the melting point of the base metals; the filler metal melts and flows into the joint by capillary action.
- Hierarchy of controls
- The hierarchy of controls is elimination, substitution, engineering controls, administrative controls, and personal protective equipment (PPE), in order of effectiveness.
- Heat input formula
- Heat input (J/in.) = (voltage × amperage × 60) / travel speed (in./min); it is used to control cooling rates and mechanical properties.