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A method for increasing the proportion of special grain boundaries in precipitation-strengthened austenitic heat-resistant steel
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A technology of austenitic heat-resistant steel and special grain boundaries, applied in the field of metals and alloys, can solve the problems of recrystallization lag, reduction of recrystallization energy, consumption of system energy, etc., to increase the content of special grain boundaries, save time and cost , the effect of optimizing the microstructure
Active Publication Date: 2018-06-19
ANYANG INST OF TECH
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[0005] The technical problem solved in the present invention is: to overcome the competitive process of precipitation and recrystallization that is not considered in the prior art, the precipitation process consumes system energy, reduces the energy used for recrystallization, recrystallization lags, and the existing grain boundary engineering design method poorly implemented
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Embodiment 1
[0023] Example 1. The improved 310 austenitic heat-resistant steel in the hot-rolled state is subjected to grain boundary optimization treatment, and its nominal chemical composition is: 25Cr, 20Ni, 0.1C, 0Mn, 2.0Mo, 0.65Si, 0.2Ti, 0.2Zr, 0.15W, 0.15V, the average grain size of the hot-rolled state is 30μm.
[0024] The first step is to keep warm at 1200°C for 40 minutes, and then carry out rolling deformation at room temperature on a two-roll rolling mill with a deformation amount of 30%, which is completed in two passes; the second step is to hold at 1120°C for 20 minutes and then quench water to cool to room temperature, and then kept at 1120°C for another 40 minutes, quenched and cooled to room temperature; in the third step, spot-polishing and EBSD tests were performed on the treated samples, and analyzed by HKL-Channel 5 software. The contents of different grain boundaries are shown in the table 1, the content of Σ≤29 special grain boundaries reaches 86.24%; its distribu...
Embodiment 2
[0025] Example 2 The above methods (1) to (3) were adopted, and after the sample was kept at 1230° C. for 30 minutes for solid solution, it was subjected to 40% room temperature cold rolling. This was followed by 2 cycles of recrystallization annealing at 1150°C. EBSD observation was carried out on the tissue, and the EBSD pictures were analyzed with the help of HKL-Channel 5 software. The results are as follows: image 3 shown. The distribution of different special grain boundaries is relatively uniform, and the content of grain boundaries whose content Σ≤29 is 83.15% (see Table 1, different grain boundary contents (number ratio, %) of each example steel).
Embodiment 3
[0026] Example 3 According to the above method, the improved 310 stainless steel was subjected to grain boundary optimization treatment. The nominal chemical composition of the steel is: Fe-25Cr-20Ni-0.2T-0.2Zr-0.1W-0.15V-2.0Mn-0.65Si-0.1C (wt.%), and the sample is solidified at 1250°C for 40 minutes Afterwards, 50% room temperature cold rolling was carried out. Subsequently, one cycle of recrystallization annealing was performed at 1200°C. EBSD observation was carried out on its tissue, and the results were as follows: Figure 4 shown. The uniformity of the microstructure is better, and the sum of the number percentages of different grain boundary types is higher, reaching 86.33%.
[0027] Table 1
[0028]
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Abstract
The invention belongs to the field of precipitation-strengthened austenite heat-resistant steel and relates to a method for increasing the proportion of special grain boundaries in precipitation-strengthened austenite heat-resistant steel. The optimized treatment process includes solution, cold rolling and annealing. It is characterized in that it is first subjected to solution treatment at 1150-1300°C for 20-60 minutes; then it is rolled at room temperature with a deformation of 20-60%, and the reduction in a single pass is not less than 15%, and then it is rolled at 1100-1250°C Periodic short-time annealing and water cooling at a certain temperature. After optimized treatment, the special grain boundaries in the microstructure of precipitation-strengthened austenitic heat-resistant steel are evenly distributed, and the proportion is higher than 80%. The invention improves the strain storage energy by increasing the deformation at room temperature, and promotes the occurrence of recrystallization in the precipitation-strengthened austenitic steel, thereby increasing the special grain boundary ratio in the precipitation-strengthened high-Cr and high-Ni austenitic heat-resistant steel, and optimizing its relationship with the grain boundary. Industry-relevant properties, especially corrosion resistance and radiation swelling resistance.
Description
technical field [0001] The invention is applicable to austenitic heat-resistant steel strengthened by dispersed precipitates and metals and alloys with a face-centered cubic (Face Centered Cubic, fcc) structure. In particular, a technical method is provided for increasing the grain boundary content of low ΣCSL (Coincidence Site Lattice, CSL) special structure in austenitic heat-resistant steel, and the invention belongs to the technical field of deformation and heat treatment. Background technique [0002] The development of clean and efficient fourth-generation supercritical water-cooled conceptual reactors and ultra-supercritical thermal power generation systems will contribute to the reduction of CO 2 It is of great significance to reduce emissions and alleviate the energy crisis. The service environment of high temperature, high pressure and water vapor puts forward higher requirements on the high temperature corrosion resistance and thermal strength of materials. At p...
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