Structural characteristics and mechanical properties of carbon steel with niobium and vanadium

Abstract

1. The addition of 0.6% V and 0.6% Nb to steel with 0.6% C (steel 60BF) resulted, after preliminary normalization at 850°, in an austenite grain size of 2.7 μ (grade 14) that was stable during heating to 850–1050° at rates of 20–60 deg/sec. Isothermal holding for as long as 180 sec at 950° does not lead to grain growth. 2. The austenite grain size of steel 60BF after quenching from 850–1050° is 2.5–2.0 μ. The austenite grain size remains essentially unchanged for the steel subjected to preliminary quenching or normalization. 3. The effect of tempering temperature on the mechanical properties of steel 60BF and 60 in relation to the austenite grain size was investigated. The steels with smaller grains have better properties at all tempering temperatures with the exception of 500–650°. Due to aging processes at these temperatures the ultimate and yield strengths and the modulus of elasticity are higher for steel 60BF with coarse grains than for the steel with fine grains.