Q9: Welding procedure

MMA - correct, it is possible to use MMA welding however it would not give as consistent (due to it being a manual process) or clean a weld as an alternative process suggested in the list which would result in poorer final properties. Try again to find the other answer.

SAW - incorrect, SAW would probably not be used on the final assembly site since it is generally a highly automated process that is difficult and expensive to set up for a relatively small production run. Try again.

MIG - correct, MIG welding will give a good quality weld, however if welding is to be carried out at the bridge construction site an alternative welding procedure may be used as MIG welding requires protection from rain and wind (e.g. use of sheets / covers) to prevent water ingress and the gas shield being disrupted. Try again to find the other answer.

Friction welding - incorrect, it is not possible to join two steel plates together by friction welding. Try again.

Laser welding incorrect, laser welding is too expensive, currently, to use for this type of application especially as a high power laser would be required to weld the typical plate thicknesses used for bridge plate. There would also be difficulties in trying to locate the laser unit for on site welding. However, for higher production, single site, applications such as ship building laser welding can be used. Try again.

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NOTEPAD

The 3 most important properties for plate steel for structural applications:
Strength, Toughness and Weldability

Typical yield strength level for a family saloon car panel (roof or wing) is: 350 - 500 MPa (more accurately 400 MPa)

Maximum pearlite content in the steel:23%

Yield strength and tensile strength levels in the candidate steel: 238 MPa and 502 MPa respectively.

Strengthening mechanisms to increase the yield strength of the candidate steel in order of preference: Grain size refinement, precipitation strengthening, solid solution strengthening, dislocation strengthening, microstructural strengthening

Grain size require to achieve a 400 MPa yield strength in the candidate steel: 4.4 �m

Carbon equivalent of the steel and processing route to obtain a fine ferrite grain size:C^D_equiv of 0.21 and (TMCR)

DBTT of the HSLA steel:-81 �C.

Welding process used for on site joining of two bridge plates: MIG or MMA
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