MODULE 20, CWB: STRUCTURE and PROPERTIES of METALS fully solved 2023/2024

MODULE 20, CWB: STRUCTURE and PROPERTIES of METALS1 The electron can be shared between two atoms. - correct answer 1. COVALENT BOND, pg 6 2. In a welding arc a large number of ions are created, certain elements with low ionization potential can be added to facilitate establishing a stable arc, or plasma. Among all these elements which one is the most presence in many electrode coatings? a. Helium b. Oxygen c. Aluminum d. Potassium - correct answer 2. answer D, table 3.1 3. An atom in the charged state is called ? - correct answer 3. Ion sect.3.1 4. Which one these material that has the lowest "work function" ? a. Tungsten b. Nickel c. Iron d. Thoria - correct answer 4. answer d,Thoria Table 3.2 5. Some metals, notable iron, can exist in different crystal forms depending on the temperature. These are termed allotropic forms. What is the iron structure between 910 C - 1390 C ? a. BCC b. FCC c. Liquid d. HCP - correct answer 5. answer b, FCC, sect 4.2 6. Most metals are chemically unstable as pure elements, and exist in their natural state as oxide or sulphide ores. Iron for example, exists in the natural state in typical ores such as ? - correct answer 6. Magnetite and hematite. Pg2 7. The places where the regular crystal pattern of atoms breaks down and there is a local distortion as the surrounding atoms try to fit the proper pattern. a. Dislocations b. Slips c. Yields d. Distortions - correct answer 7. a. Dislocations, sec.5.1.1 8. These three elements, H, C and N are particularly important in welding because they are soluble in many metals and can be the cause of cracking, embrittlement and other problems. a. Solid Solutions b. Interstitial Solutions c. Both a and b - correct answer 8. b Interstitial Solutions, sect 6.1.2 9. What is the graphics of relationship of work hardening coefficient between strain and stess ? a. Parabolic b. Straight line c. Flat Line d. Constant value - correct answer 9. a. Parabolic. fig.7.1 10. A eutectoid reaction is similar to eutectic reaction, but it occurs in the ---------- rather than --------? a. solid, gas b. solid, liquid c. liquid, gas d. liquid, solid - correct answer 10. answer b; sect 6.2.2.1 11. Which alloy elements used in steel that has the highest strengthening effect ? a. Chromium b. Copper c. Carbon d. Nickel - correct answer 11. answer C, fig 8.2 12. Of all the strengthening methods available which one that simultaneously improves strength and toughness ? a. Grain refinement b. Precipitation hardening c. Strain aging d. Solid solution stregthening - correct answer 12. answer A, sect 8.4.1 13. Effect of thickness on cooling rate on the thick plate does not depend on the thickness. True or False ? - correct answer 13. asnwer True. sect 11.3.2.4 14. Heat input on a 12 mm steel plate cools ----------times more quickly than one for 6 mm plate. a. the same rate b. two c. four d. a few - correct answer 14. answer C, sect 11.3.2.4 15. Fluxes or mixtures of compounds that do not mix with metals in the molten state are commonly used to shield weld metal. The composition of a flux depends on the metal for which it is being used, and usually designed to have a melting point -----------that of the metal. ly the same b. lower c. higher d. depends on the carbon content - correct answer 15. answer B, sect 10.2