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10B21冷镦钢(/%:0.18~0.23C,≤0.10Si,0.60~0.90Mn,≤0.030P,≤0.035S,0.000 8~0.003 0B,≥0.02A1)的生产流程为50 t顶底复吹转炉-LF-280 mm×325 mm连铸坯-连轧成中12 mm材。通过检测得出,当钢中氮含量为0.004 6%时,该钢淬火后的HRC硬度值为41~43,而当钢中氮含量为0.008 1%时,其淬火后HRC硬度值为21~27,小于技术条件要求HRC值38。通过试验得出Ti/N≤8时,随Ti/N增加,钢中硼的收得率显著增加,如钢中氮含量0.004 6%时,Ti/N为7.4,硼收得率达90%,钢中氮含量0.008 1%时,Ti/N为4.3,硼的收得率不到70%,造成钢中B含量低,淬火后HRC值降低。通过改进BOF和LF操作,使钢中氮含量控制在0.005%以下(0.003 9%~0.004 1%),Ti/N为7.5~8.1,钢材心部淬火HRC值为40~42,达到用户要求。
10B21 Cold heading steel (/% 0.18 ~ 0.23C, ≤ 0.10Si, 0.60 ~ 0.90Mn, ≤ 0.030P, ≤ 0.035S, 0.000 8 ~ 0.003 0B, ≥ 0.02A1) The production process is 50 t top and bottom blow Converter -LF-280 mm × 325 mm slab - Continuous rolling into 12 mm material. The results showed that when the content of nitrogen in steel is 0.004 6%, HRC hardness of this steel after quenching is 41 ~ 43, while when the content of nitrogen in steel is 0.008 1%, the hardness of HRC after quenching is 21 ~ 27, less than the technical requirements of HRC 38. The experimental results show that with the increase of Ti / N, the yield of boron in steel increases obviously when Ti / N≤8. For example, when the content of nitrogen in steel is 0.004 6%, the Ti / N is 7.4 and the boron yield is 90% , The content of nitrogen in steel is 0.008 1%, Ti / N is 4.3, boron yield is less than 70%, resulting in low content of B in steel and lower HRC after quenching. By improving the operation of BOF and LF, the nitrogen content in the steel is controlled below 0.005% (0.003 9% -0.004 1%) and the Ti / N is 7.5 to 8.1. The HRC value of heart quenching of steel is 40-42, meeting the requirements of users.