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 TB 55-1900-201-45/1
discontinuities. Half-round installations which disturb the smooth, unnotched edge of the sheer strake should be avoided.
High strength steels require very special handling during fabrication. Great care must be excercised in adhering to the
procedures recommended by the steel manufacturer, in the care and use of the correct welding elect- rodes, and in the
proper identification of the steel. The usual shipyard practices suitable for working with conventional ship steel are not
adequate when it comes to high strength steel. Among the more important reasons for this are the following:
(1) Steels look the same, but when used in the design of a ship, much greater loads are imposed on the special
steels; loads which probably could not be sustained if conventional steel was substituted by mistake.
(2) Welding electrodes which are satisfactory for conventional steel would not provide strength, in way of the
welded con- nection, equivalent to the strength of the plates joined. In most cases, low hydrogen electrodes are recom-
mended for welding high strength steels in order to avoid underbead cracking.
(3) In some high strength steels; for example, the quenched and tempered steels, a heat input during welding
which would be acceptable for conventional steel, would drastically reduce the toughness of the special steel in the heat
affected zone (HAZ).
(4) Also, in some of these steels, the installation of temporary clips or even arc strikes on the plate can have a
serious, detrimental effect.
b. In view of the above, renewal or repairs involving high strength steels should not be undertaken without recourse
to plans and procedures which have been approved for the specific installa- tion. Further information on the welding of
high strength steel is available from the Commandant (MMT) or the field (mmt) office.
E-31.
Filler Metal.
a. Electrodes should be suited to the steel to be welded. Except when special steels are involved or specific elec-
trodes are indicated on approved plans, the welding electrodes should be among those listed in the current American
Bureau of Shipping approved list, "Approved Welding Electrodes Wire-Flux and Wire-Gas Combinations."
b. This list is distributed to all Marine Inspection Offices by the Commandant whenever new issues are published. It
is to be noted that most of the approved welding electrodes are listed in Equipment Lists, CG-190, but this listing will be
discontinued beginning with the 1968 edition.' Electrodes should be kept dry while in storage. Where low hydrogen elec-
trodes are used, it is especially important that they be dehydrated before use. Otherwise,
E-21
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