Introduction of the hottest ultra-fine grain steel

Introduction of ultra-fine grain steel (Part 1)

compared with traditional steel with the same strength, the main characteristic of ultra-fine grain steel is its low carbon content, which is conducive to improving its weldability. Therefore, its strengthening means is not to increase the carbon content and alloy element content, but to improve the strength and toughness through the combination of grain refinement, phase transformation strengthening, precipitation strengthening and so on. Grain refinement (including deformation refinement and transformation refinement) is the only method that can improve the strength and toughness of steel at the same time, so it has become the best strengthening mechanism of ultra-fine grain steel. Precipitation strengthening by using second phase particles is another strengthening mechanism adopted by ultra-fine grain steel. Although particles formed in austenite at high temperature are effective in controlling grain growth, they will not cause strengthening. Strengthening particles are formed in austenite or ferrite at low temperature. Dislocation and substructure strengthening is also an effective strengthening method

1 classification

in traditional steel, the grain size below 100 m is called fine grain steel, that is, traditional fine grain steel. With the continuous progress of metallurgical technology and production process, the size of fine crystal continues to shrink, even reaching micron and submicron. Although China's mechanical products have a certain international comparative advantage. The ultra-fine grain steel mentioned in this paper does not include the traditional fine grain steel

according to the development process and size of ultra-fine grain steel, it can be divided into the following categories

(1) TMCP Steel

the steel manufactured by accelerating cooling immediately after controlled rolling is called TMCP (thermo mechanical control process) steel. Using TMCP process, the grain size can reach several microns in the laboratory, but in the actual industrial production, the grain size of the obtained steel is less than 50 m, and the minimum can reach 10 m. This kind of steel meets the needs of the oil and gas industry. Its high strength, high toughness and low carbon equivalent provide it with excellent welding adaptability

(2) new generation of iron and steel materials

integrate the successful experience of continuous progress of low-alloy high-strength steel, make full use of the advantages of the combination of alloying and production technology progress, develop a new generation of iron and steel products and carry out its basic theoretical research. The main characteristics of the new generation of steel materials currently in the development stage: under the condition of full consideration of economy, the steel has the characteristics of high cleanliness, ultra-fine grain and high uniformity, and the strength is higher than that of common steel. Follow the technicians of our company to learn how to install and operate the concrete pressure testing machine, and the service life of the steel is doubled. High cleanliness refers to the total content of elements s, P, O, N and h. However, using a large range of equipment to test objects with low compression requirements less than 80 can not only improve the original performance of steel, but also sometimes give new performance to steel; Ultrafine structure, grain size between 0.1 ~ 10 m, grain refinement is the only way to improve strength without reducing toughness or even improving toughness; High uniformity refers to that the composition, structure and performance are very uniform, and the system can automatically realize the calibration of indication accuracy; The fluctuation range is very small. In the relationship between chemical composition, process structure and properties of steel, the dominant position of structure is emphasized, that is, its ultra-fine microstructure shows excellent comprehensive properties