Free CWI Fundamentals Tech Questions and Answers — Questions and Answers
Question 1: Which of the following metals cannot be cut using OFC in an efficient manner?
- low-carbon steel
- high-carbon steel
- cast iron
- stainless steel (Correct answer)
- tempered steel
Correct answer: stainless steel
Oxy-fuel cutting (OFC) relies on the rapid oxidation of iron, where molten iron oxide is blown away by an oxygen jet. Stainless steel contains a high percentage of chromium, which forms a refractory chromium oxide layer that resists oxidation and has a higher melting point than the base metal. This protective layer prevents the continuous oxidation process necessary for efficient OFC, making it unsuitable for cutting stainless steel effectively.
Question 2: Which NDE method's fundamental requirement is a part's electrical conductivity?
- UT
- ET (Correct answer)
- RT
- PT
- VT
Correct answer: ET
Eddy Current Testing (ET) is a non-destructive examination method that uses electromagnetic induction to detect flaws in conductive materials. It works by inducing eddy currents in the test piece using an alternating magnetic field. The presence of discontinuities or changes in material properties alters these eddy currents, which are then detected by the probe, making electrical conductivity a fundamental requirement for this method.
Question 3: Carbon steel has a melting point that is roughly:
- 3333° F
- 2250° F
- 2375° F
- 2780° F (Correct answer)
- 3005° F
Correct answer: 2780° F
The melting point of carbon steel varies slightly depending on its carbon content and other alloying elements, but it generally falls within a specific range. 2780° F (approximately 1527° C) is a commonly accepted average or representative melting point for various grades of carbon steel. This temperature is a critical parameter for understanding welding processes, heat treatment, and material behavior at high temperatures.
Question 4: Which NDE approach is the term "decibel" related with?
- ET
- UT (Correct answer)
- RT
- MT
- PT
Correct answer: UT
The term 'decibel' (dB) is primarily associated with Ultrasonic Testing (UT). In UT, decibels are used to express the ratio of two sound intensities or amplitudes, often to quantify the attenuation of ultrasonic waves as they travel through a material or to compare the amplitude of a reflected signal (echo) to a reference. This measurement helps in evaluating the size and nature of discontinuities within a material.
Question 5: Which GMA W metal transfer mode has the lowest penetration rate?
- short circuiting (Correct answer)
- globular
- pulsed spray
- spray
- globular spray
Correct answer: short circuiting
Short circuiting transfer (GMAW-S) operates at lower voltages and amperages compared to other GMAW modes. The wire electrode repeatedly touches the weld puddle, creating a short circuit that extinguishes the arc and melts the wire. This results in a cooler weld puddle and less arc force, leading to the shallowest penetration among GMAW transfer modes, making it ideal for thin materials and out-of-position welding.
Question 6: Which gas or gases from the list below are frequently employed as a shielding gas for GTA W?
- Tri-mix
- argon (Correct answer)
- carbon dioxide
- oxygen
- argon/carbon dioxide
Correct answer: argon
Argon is the most commonly used shielding gas for Gas Tungsten Arc Welding (GTAW), also known as TIG welding. Its inert nature prevents atmospheric contamination of the weld puddle and tungsten electrode, ensuring a stable arc and high-quality welds. While helium or argon-helium mixtures can be used for increased heat input, pure argon is the primary choice due to its excellent arc starting characteristics and cost-effectiveness.
Question 7: The welding inspector should do the following once the rejected weld has been rectified, reinspected, and determined to be acceptable:
- mark directly on the part
- change the original inspection report to indicate the part's acceptance
- tell the foreman to have the part moved o its next operation
- fill out a second inspection report (Correct answer)
- no further action is required
Correct answer: fill out a second inspection report
Proper documentation is crucial in welding inspection to maintain a clear and accurate record. When a rejected weld is repaired and then reinspected, a new inspection report must be generated to document the repair work and its subsequent acceptance. This ensures a complete audit trail, indicating that the original non-conformance was addressed and the part now meets specifications, without altering the historical record of the initial rejection.
Question 8: How are the alloy's atoms integrated into the native metal lattice structure when a metal is alloyed?
- by casting
- by inclusion or exclusion
- substitutionally or interstitially (Correct answer)
- by diffusion
- be becoming martensitic
Correct answer: substitutionally or interstitially
When metals are alloyed, the atoms of the alloying element are incorporated into the crystal lattice of the base metal in two primary ways. In substitutional alloying, the solute atoms are roughly the same size as the solvent atoms and replace them in the lattice. In interstitial alloying, smaller solute atoms fit into the spaces (interstices) between the larger solvent atoms, forming a solid solution and altering the material's properties.
Question 9: Which NDE approach uses a wire IQI?
- PT
- UT
- ET
- RT (Correct answer)
- MT
Correct answer: RT
A wire IQI (Image Quality Indicator), also known as a penetrameter, is a device specifically used in Radiographic Testing (RT) to assess the quality of the radiographic image. It contains wires of varying diameters that must be discernible on the radiograph to confirm that the image has sufficient sensitivity to detect relevant discontinuities. IQIs ensure the radiographic technique is capable of revealing defects of a certain size.
Question 10: Which of the following is not frequently employed as a semiautomatic procedure in general?
- MIG
- GMAW
- FCAW
- SMAW (Correct answer)
- SAW
Correct answer: SMAW
Shielded Metal Arc Welding (SMAW), commonly known as stick welding, is primarily a manual welding process where the welder manually controls the electrode and arc length. Unlike GMAW (MIG), FCAW, or SAW, which involve continuous wire feeding mechanisms, SMAW does not typically employ semiautomatic wire feeding. Therefore, it is not generally classified as a semiautomatic procedure in the same way as the other options.
Question 11: Which of the following test procedures is least influenced by high part temperatures in terms of performance?
- RT
- ET (Correct answer)
- UT
- PT
- VT
Correct answer: ET
Eddy Current Testing (ET) is generally less affected by high part temperatures compared to other NDE methods. Unlike Ultrasonic Testing (UT) which can be affected by changes in sound velocity, or Liquid Penetrant Testing (PT) and Magnetic Particle Testing (MT) which have temperature limitations for penetrants/developers and magnetic properties, ET can often be adapted for hot surfaces, though probe design and calibration become critical.
