Effect of boron on microstructure and properties of ultra-low carbon steel

Abstract

The effect of boron on microstructure, mechanical property and conductivity of ultra-low carbon steel wire rod with diameter 6.5 mm was studied. The results show that boron has little influence on the grain size and mechanical property of ultra-low carbon steel wire rod when adding 0.0020% boron alone and under the same process conditions; but when 0.0055% boron is added, the ASTM grain size number of the wire rod is coarsened from the 7.5 grade to 6 grade, at the same time, the tensile strength is reduced by 20 MPa and the electrical conductivity is increased from 16.2%IACS to 16.3%IACS. The effect of Boron on tensile strength is mainly caused by coarsening grain diameter. The effect of boron on grain diameter is related to [B]/[N], when the [B]/[N] is relatively high(for example 1.34), the grain diameter growth is obvious, conversely, when the [B]/[N] is relatively low(for example 0.44), the grain diameter growth is not obvious.