Preheating Temperature & Aluminium Butt Joint
49. Name the weld defect which will occur if a No. 3 nozzle is used for welding a 3 mm thick brass sheet
A. undercut   
B. burn through   
C. porosity   
D. lack of penetration

50. The size of nozzle used to gas weld 3.15 mm thick aluminium butt joint is…
A. 13   
B. 10   
C. 7   
D. 5

51. Nozzle size used for welding a 2 mm thick stainless steel sheet as a butt joint is…
A. 2   
B. 3    
C. 5   
D. 7

52. What is the value of preheating temperature for gas welding of aluminium?
A. 100 to 120◦C   
B. 150 to 180◦C   
C. 180 to 200◦C   
D. 210 to 250◦C

53. In soldering operation the base metal is…
A. not heated   
B. heated to 200◦C   
C. heated to 650◦C   
D. heated to red hot condition

54. For welding dissimilar metals, the following property of both the metals should not have wide variations
A. ductility   
B. tensile strength   
C. thermal expansion    
D. wear resistance

55. Name the flux used for brazing of M.S. sheets
A. hydrochloric acid    
B. zinc chloride   
C. tallow resin   
D. borax

56. In progressive gouging to what angle the gouging torch angle is reduced from the starting angle of 30◦?
A. 20 to 25◦    
B. 15 to 20◦  
C. 10 to 15◦   
D. 5 to 10◦

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