HOT-ROLLED STEEL PLATE WITH HIGH RATIO BETWEEN YIELD STRENGTH AND ULTIMATE STRENGTH, WITH HIGH CHARACTERISTICS OF IMPACT ENERGY ABSORPTION AT LOW TEMPERATURE, AND SOFTENING RESISTANCE OF HEAT-AFFECTED ZONE (HAZ), AND METHOD OF ITS MANUFACTURING Russian patent published in 2015 - IPC C22C38/14 C22C38/12 C21D8/02 C23C2/02 C23C2/28 

FIELD: metallurgy.

SUBSTANCE: plate is made from steel containing in wt %: C: from 0.04 to 0.09, Si: 0.4 or less, Mn: from 1.2 to 2.0, P: 0.1 or less; S: 0.02 or less; Al: 1.0 or less, Nb: from 0.02 to 0.09, Ti: from 0.02 to 0.07, N: 0.005 or less; Fe and inevitable admixtures - rest. For steel components the following ratio is met 2.0 ≤ Mn+8[%Ti]+12[%Nb] ≤ 2.6. The plate has microstructure where fraction in percents of pearlite area is 5% or less, total are of martensite and residual austenite is 0.5% or less, other structure is presented by ferrite and/or beinite. Average grain size of ferrite and beinite is 10 mcm or less, and average grain size of carbonitrides of the alloying metals with incoherent interphase boundaries containing Ti and Nb is 20 nm or less.

EFFECT: manufactured plates have maximum tensile strength 600 MPa or over, yield strength to ultimate strength ratio is 0,85 or over, and high characteristics of impact energy absorption at low temperature, and resistance against HAZ softening.

10 cl, 3 dwg, 3 tbl, 1 ex