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Title:Formability of New High Performance A710 Grade 50 Structural Steel
Author(s):Vaynman, Semyon; Fine, Morris E.; Hahin, Christopher
Subject(s):Steel
Formability
Yield strength
Ultimate tensile strength
ductility
ASTM A710 Grade B
Abstract:Northwestern University and the Illinois Department of Transportation, with ASTM A606 Type 4 weathering steel used in Illinois and many other states for sign and signal structures, light poles, and other highway structures. ASTM E290 Type 1 free-bend 180° guided-bend test was used to evaluate formability, with side clearances as per ASTM E190. Bend and tensile specimens were cut in longitudinal and transverse directions from plates and sheets of numerous thicknesses (from 0.38" down to 0.10" thick). Mandrels of three diameters (0.25", 0.313", and 0.375") were used, each having a rounded nose with radius of bend equal to ½ of the mandrel diameter. All specimens of A710 and A606 steels of all thicknesses passed the guided-bend tests. No cracks, side tears, or fractures were observed. Tensile tests showed excellent ductility in both longitudinal and transverse rolling directions, making the modified ASTM A710 steel very suitable for use in sign and signal structures, light poles, and highway structures, along with structural tubing and other applications requiring weathering steel sheets and plates. Comparable A606 Type 4 steel had a yield strength range of 65 to 73 ksi and an ultimate tensile strength range of 79 to 89 ksi. The elongation to failure for the A606 steel sheets was in the range of 41% to 49%, averaging 43% ± 2.5% based on a 1" gage length. The microstructure of A606 steel is primarily ferrite with a limited amount of pearlite. The grain size of A606 in thinner plates was much smaller; grains were more rounded in thicker plates. Two heats of modified A710 Grade B steel were tested. Variations in mechanical properties were a function of steel composition, hot-rolling procedures, and thickness of the plates or sheets. In the first heat, yield strength varied in a range of 48 to 119 ksi, and tensile strength ranged from 64 to 119 ksi. The variation in the strength in the first heat was most likely caused by excessive section reduction during hot-rolling. The microstructure of the A710 steel was fine-grained ferrite and was significantly smaller than the A606 steel grains of similar thickness, which accounted for the higher strengths of the A710 steel in the first heat. Some bands of pearlite and fine-grained ferrite were observed in the modified A710 sheets, but did not affect the formability of the steel. Copper, nickel and manganese contents were decreased and better rolling procedures were used in the second heat, which had a uniform 49 to 56 ksi yield strength range. The second heat also had a uniform yield to tensile ratio of 0.74, high ductility and formability, making this alloy a very attractive weathering steel for many transportation and structural applications. An optimized 50 ksi minimum yield strength composition with an ASTM G101 index of 6.0 or more was developed for A710 sheet steel, and is proposed for general use in transportation and other construction applications.
Issue Date:2014-01
Publisher:Illinois Center for Transportaton
Series/Report:Illinois Center for Transportation Series No. 14-002
Genre:Technical Report
Type:Text
Language:English
URI:http://hdl.handle.net/2142/47234
ISSN:0197-9191
Publication Status:published or submitted for publication
Peer Reviewed:not peer reviewed
Sponsor:Illinois Department of Transportation (R27-106)
Rights Information:No restrictions. This document is available to the public through the National Technical Information Service, Springfield, VA 22161
Date Available in IDEALS:2014-02-24


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