Can you provide a detailed explanation of the alloy compositions and mechanical properties of some of the most commonly used low-alloy high-strength steel plate grades?

TAGS: grade | strength | minimum |

Low-alloy high-strength steel (LAHSS) is a popular choice for structural and heavy engineering applications where strength, toughness, and weldability are required. LAHSS typically contains less than 0.2% carbon and 1% manganese, with small amounts of other alloying elements such as vanadium, niobium, and titanium. The following are some of the most commonly used LAHSS plate grades, with their alloy compositions and mechanical properties:

1. ASTM A572 Grade 50: This grade is the most commonly used LAHSS plate grade in the United States. It has a minimum yield strength of 50 ksi (345 MPa) and a minimum tensile strength of 65 ksi (450 MPa). The alloy composition includes 0.23% carbon, 1.35% manganese, 0.04% phosphorus, 0.05% sulfur, 0.30% silicon, 0.20% copper, 0.05% niobium, and 0.02% vanadium.

2. ASTM A514 Grade B/E/F/H/Q: This grade is a quenched and tempered LAHSS plate used for high-stress applications such as construction machinery and off-highway vehicles. It has a minimum yield strength of 100 ksi (690 MPa) and a minimum tensile strength of 110-130 ksi (760-900 MPa). The alloy composition includes 0.12-0.21% carbon, 0.45-0.70% manganese, 0.035% phosphorus, 0.04% sulfur, 0.20-0.35% silicon, 0.003-0.008% boron, and 0.005-0.050% vanadium.

3. ASTM A656 Grade 80: This grade is a thermomechanical controlled process (TMCP) LAHSS plate used for bridge and building construction applications. It has a minimum yield strength of 80 ksi (550 MPa) and a minimum tensile strength of 90 ksi (620 MPa). The alloy composition includes 0.18% carbon, 1.65% manganese, 0.025% phosphorus, 0.035% sulfur, 0.60% silicon, 0.10% niobium, 0.08% vanadium, and 0.005% nitrogen.

4. ASTM A572 Grade 60: This grade is a commonly used LAHSS plate grade similar to Grade 50, but with slightly higher strength and ductility. It has a minimum yield strength of 60 ksi (415 MPa) and a minimum tensile strength of 75 ksi (520 MPa). The alloy composition includes 0.26% carbon, 1.35% manganese, 0.04% phosphorus, 0.05% sulfur, 0.30% silicon, 0.20% copper, 0.05% niobium, and 0.02% vanadium.

5. ASTM A572 Grade 65: This grade is a high-strength low-alloy (HSLA) LAHSS plate used for welded construction applications such as bridges and buildings. It has a minimum yield strength of 65 ksi (450 MPa) and a minimum tensile strength of 80-90 ksi (550-620 MPa). The alloy composition includes 0.23% carbon, 1.65% manganese, 0.04% phosphorus, 0.05% sulfur, 0.30% silicon, 0.20% copper, 0.04-0.05% niobium, and 0.015-0.060% vanadium.

In summary, LAHSS plate grades are designed to provide high strength and toughness with good weldability for heavy engineering applications. The alloy compositions and mechanical properties vary depending on the specific grade and application, but all LAHSS plate grades contain low levels of carbon and manganese, with small amounts of other alloying elements to enhance strength and toughness.