Research and Development of 10B38 Boron Containing Cold Heading Steel

Abstract

The strength and plasticity of 10B38 boron containing cold heading steel under different high temperature condi⁃ tions were studied using high-temperature tensile testing method. The results showed that the tensile strength decreased significantly from 124. 8 MPa to 22. 9 MPa at temperatures ranging from 700 to 950 ℃； At 950 to 1 150 ℃， the tensile strength was 12. 7 to 25. 5 MPa. In terms of thermoplastic properties， the cross-sectional shrinkage rate at 700-750 ℃ was 56%-72%； When the temperature was between 800 and 1 050 ℃， the cross-sectional shrinkage rate was ≥ 75%； When the temperature was between 1 050 and 1 150 ℃， the cross-sectional shrinkage rate was greater than 65%. Based on the above experimental data， the strength of the secondary cooling water in continuous casting was optimized from a specific water content of 1. 35 L/kg to a specific water content of 1. 25 L/kg. After optimization， the crack index of the continuous casting slab was significantly reduced. The dynamic CCT curves of 10B38 boron containing cold heading steel were mea⁃ sured， The experimental results showed that when the cooling rate was 0. 2-1 ℃/s， the test steel was mainly composed of softer ferrite structure； When the cooling rate was 3-10 ℃/s， the experimental steel was mainly composed of pearlite struc⁃ ture； When the cooling rate was 20 ℃/s and 30 ℃/s， the structure of the test steel was flat noodles martensite+pearlite； When the cooling rate was 50 ℃/s， a complete martensitic structure was formed at room temperature. The experimental re⁃ sults showed that by reducing the cooling rate to 0. 5-2 ℃/s， ideal ferrite and pearlite hot-rolled structures can be obtained.

Keywords

• 10b38 cold heading steel； high-temperature tensile； cct curves