12. (a) What are some methods and marks of distinguishing steel from other metals?
(b) How is cast steel distinguished from cast iron?
13. (a) Name some of the qualifications of a good “filler-rod” for mild steel welding.
(b) In what manner does the “filler-rod” differ for the alloyed and high-carbon steels?
14. (a) In bringing the neutral flame in contact with the metal on a steel weld, should the cone bend and spread on the surface, or just lick it?
(b) Explain why.
15. (a) What is the principal cause for hard spots in steel welds?
(b) What causes some of the others?
16. (a) Is it rolled steel or cast steel that does not expand when heated?
(b) Name one other metal that does not expand when heated.