CEMP-E
TI 809-26
1 March 2000
c. Cold Weather Applications. Steel toughness requirements should be considered for major load-
carrying components of structures exposed to extreme cold environments. When structural components
in a low-temperature environment are not subject to significant impact loads or fatigue conditions, it is
generally more cost effective to specify a type of steel with inherently good fracture toughness, and
avoid a requirement for specific CVN toughness at a reference temperature. High-strength low alloy
(HSLA) steels that are manufactured using fine grain practice have improved toughness at low
temperature, compared to conventional carbon steels such as A36 steel. AISC-approved steels requiring
production to fine-grain practice are A588, A709 (grades 50W, 70W, 100, 100W), A852, and A913
(grades 60, 65 and 70), although higher strength structural steels present additional welding difficulties
and should not be specified unless necessary for weight savings. Fine-grain practice can optionally be
specified using ASTM Supplemental Requirement S91 for A36, A572, A992, A709 (grades 36 and 50),
and A913 (grade 50). It is not available for A529, A242, or A283 steels. Steels that require killing, which
also improves toughness, include A992 and A709 (grades 100, 100W), but the higher strength grades
should be avoided because of other welding difficulties. Nitrogen has a significant effect upon CVN
transition temperatures, and limitations on nitrogen may be considered. A992 steels place a limit on
nitrogen of 0.012%, unless nitrogen binders are added. A572, Type 4 steel has a limit on nitrogen of
0.015%.
d. High Stress / Strain / Restraint Applications. When welded joints are made to the side of a member,
creating through-thickness shrinkage stresses and strains, consideration should be made for the risk of
lamellar tearing. Lamellar tearing is a separation or tearing of the steel on planes parallel to the rolled
surface of the member. There is no specific through-thickness at which lamellar tearing will or will not
occur, nor specific values for weld size, stresses or strains that will induce tearing. Generally, lamellar
tearing is avoided through using one or more of the following techniques: improved design or redesign of
the joint, welding procedure controls, weld bead placement selection, sequencing, the use of preheat
and/or postheat, the use of low-strength, high-ductility filler metals, "buttering," and peening. However,
steels with improved through-thickness properties may also be specified. The most common method of
improving through-thickness properties, to reduce the risk of lamellar tearing, is through the specification
of low-sulfur or controlled sulfur-inclusion steels. See 3.e.
5. AVAILABILITY OF STRUCTURAL STEELS. All AISC-approved structural steels are available from
domestic steel mills, with the exception of A913. The AISC Manual of Steel Construction, Table 1-1,
provides general information regarding availability of shapes, plates and bars in various steel
specifications, grades and strengths. Table 1-4 provides similar information for round and rectangular
sections, including availability as either steel service center stock or in mill order quantities only. Table 1-
3 lists the producers of specific structural shapes, and Table 1-5 provides similar information for round
and rectangular sections. This list is updated semi-annually in Modern Steel Construction magazine,
published by AISC, in the January and July issues.
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