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Abstract The steel industry is a major source of CO2 emissions, and thus, the mitigation of carbon emissions is the most pressing challenge in this sector. In this paper, international environmental governance in the steel industry is reviewed, and the current state of development of low‐carbon technologies is discussed. Additionally, low‐carbon pathways for the steel industry at the current time are proposed, emphasizing prevention and treatment strategies. Furthermore, the prospects of low‐carbon technologies are explored from the perspective of transitioning the energy structure to a “carbon–electricity–hydrogen” relationship. Overall, steel enterprises should adopt hydrogen‐rich metallurgical technologies that are compatible with current needs and process flows in the short term, based on the carbon substitution with hydrogen (prevention) and the CCU (CO2 capture and utilization) concepts (treatment). Additionally, the capture and utilization of CO2 for steelmaking, which can assist in achieving short‐term emission reduction targets but is not a long‐term solution, is discussed. In conclusion, in the long term, the carbon metallurgical process should be gradually supplanted by a hydrogen–electric synergistic approach, thus transforming the energy structure of existing steelmaking processes and attaining near‐zero carbon emission steelmaking technology.

In this work, the effects of grain refinement on the tensile properties, dynamic strain aging (DSA) and twinning behavior of Fe–16Mn-0.6C steel, which has relatively low manganese content, were investigated using a room-temperature monotonic tensile test, OM, XRD, EBSD and TEM. Results show that the yield strength, tensile strength and elongation of the steel increase with the decrease of grain size. Grain refinement can significantly increase the serration amplitude and local strain concentration of DSA, thereby enhancing the DSA-strengthening effect. The microstructure observations show that with the formation of plentiful twins, the twinning capacity of coarse-grained steel is exhausted prematurely at initial strains. Although the twinning behavior of fine-grained steel is retarded in the early stage of deformation, a large number of fine and dense twinning structures can be produced continuously at high strains. This unique twinning behavior and enhanced DSA in the fine-grained steel maintain the strain-hardening capacity of the steel, which delays the plastic instability and hence brings about simultaneous increases in strength and ductility.

Introducing carbon diffusion is an effective method for fabricating composite steel with high strength and high ductility. Herein, three kinds of low-carbon martensite steels with different silicon contents were selected as high-strength layer materials. The effective mechanisms of the diffused content of carbon between the neighboring layers on the strength and ductility of martensite–austenite composite steel were researched. Results revealed that the martensite–austenite composite steel with different diffused contents of carbon was obtained by changing the silicon content in the martensite layer. Some carbon atoms diffused from the austenite layer into the neighboring martensite layers, resulting in an increased hardness of the martensite layer. With increasing the diffused content of carbon, the hardness of the martensite layer increased gradually. When the increment of carbon content within martensite layer was 0.16 wt%, 0.23 wt% and 0.25 wt%, respectively, the tensile strength increment of composite steel was 1, 23 and 110 MPa, respectively, as compared with the monolithic martensite steel. This indicated that the increased diffused content of carbon was beneficial for improving the tensile strength of composite steel. Accompanied with the decrement of carbon content inside the austenite layer, the elongation of composite steel was 13.6%, 17.3% and 17.9%, respectively. With decreasing the hardening ability of the austenite layer, the coordinated deformability between the neighboring layers was decreased. Consequently, the elongation of composite steel was reduced. This finding indicated that the slight diffusion of carbon atoms between neighboring layers was beneficial for improving the ductility of composite steel.

The effects of rolling temperature ranging from −55 to 300 °C on dislocation density, twinning behavior and correlative tensile properties of a high carbon high manganese steel were investigated. Results showed that the twinning behavior was enhanced at −55 °C but suppressed at 300 °C. The twin thickness and spacing increase with the rolling temperature. At low rolling reduction of 10%, the dislocation multiplication rate decreased with the increase in rolling temperature. However, the dislocation multiplication rate maintained high level when rolled at high rolling reduction and high temperature. At a given rolling reduction, the samples rolled at −55 °C possessed higher work hardening rate. Especially, the strength of −55°C-rolled-20% sample was higher than that of 300°C-rolled-30% sample and was equivalent to room temperature (RT)-rolled-30% sample. Concurrently, the elongation of the −55°C-rolled-20% sample was higher than the other two. The contributions of dislocation strengthening and twin strengthening to the yield strength of high carbon high manganese steel after rolling at different conditions were calculated by the parameter model. The dislocation strengthening effect played a dominant role under various deformation conditions. Twin strengthening effect showed a temperature sensitivity in the temperature range selected in the present study. Lower rolling temperature showed greater contribution of twin strengthening, whereas the dislocation strengthening effect was insensitive to temperature.