WO2021147271A1 - Interphase-precipitation-enhanced low-activation ferritic steel and preparation method therefor - Google Patents

Abstract

Disclosed are a low-activation ferritic steel and a preparation method therefor. The low-activation ferritic steel comprises, by mass percentage: 0.04% to 0.07% of C, 8.5% to 9.5% of Cr, 0.5% to 1.5% of W, 0.15% to 0.25% of V, 0.1% to 0.2% of Si, 0.3% to 0.6% of Mn, and 0.16% to 0.28% of Ti, with the balance being Fe. The method comprises: preparing an alloy material containing the defined mass percentages of C, Cr, W, V, Si, Mn, Ti and Fe; austenitizing the alloy material; subjecting the austenitized alloy material to isothermal ferrite phase transformation; and after the isothermal ferrite phase transformation is completed, cooling same. The low-activation ferritic steel has a good structure stability and high-temperature creep resistance, and is expected to meet requirements of structural materials for the design of a next-generation fusion experimental reactor serving at a high temperature and a high radiation intensity. The preparation method therefor is simple in terms of process and high in operability.

Description

Low activation ferrite steel strengthened by interphase precipitation and preparation method thereof Technical field

This application relates to but not limited to the field of preparation of low activation ferritic steel, and particularly relates to but not limited to a new type of interphase precipitation strengthening low activation ferritic steel and a preparation method thereof.

Background technique

Fusion reactor materials are one of the three major bottlenecks restricting the realization of commercialized controlled nuclear fusion. Low-activated martensite/ferritic steel has excellent performance in terms of radiation swelling resistance, thermal expansion coefficient, high thermal conductivity, better resistance to liquid metal corrosion, etc., and has become the fusion reactor cladding and first wall/divertor. Candidate materials. At present, the low-activation steel materials for fusion reactors in domestic and foreign research and development tests are usually improved on the basis of traditional heat-resistant steels. The quenching-tempering process is used to form a large number of dispersed carbide precipitations in the martensite matrix. The pinning effect of carbides on dislocations and martensite lath boundaries improves the service performance of the material. Studies have shown that there are a variety of carbide precipitation phases in the tempered martensite, including M ₂₃ C ₆ , MX and so on. In the service process, there is an obvious positive correlation between the structural stability of the material and the service performance of the material. The coarsening speed of MX is much lower than that of M ₂₃ C ₆ , that is, its stability is higher. On the other hand, the tempered martensite slats also tend to merge, which is not conducive to the development of creep performance. It is worth noting that due to the further increase in the service temperature and radiation intensity of the reactor (the service temperature to be overcome in the next stage is 650℃), the existing low-activated martensite/ferritic steel is resistant to creep and Irradiation and other properties can no longer meet the demand, so it is urgent to propose new material design ideas.

Summary of the invention

The following is an overview of the topics detailed in this article. This summary is not intended to limit the scope of protection of the claims.

This application provides a nanophase precipitation-strengthened low activation ferrite steel and a preparation method thereof. The low activation ferrite steel has good structure stability and high temperature creep resistance, and is expected to meet the structure of the next generation fusion experimental reactor The material is designed for service under high temperature and high radiation intensity, and its preparation method is simple in process and high in operability.

The present application provides a low-activated ferritic steel. The low-activated ferritic steel includes C: 0.04% to 0.07%, Cr: 8.5% to 9.5%, and W: 0.5% to 1.5% in terms of mass percentage. , V: 0.15% to 0.25%, Si: 0.1% to 0.2%, Mn: 0.3% to 0.6%, Ti: 0.16% to 0.28% and the balance Fe.

In the embodiment of this application, the low activation ferritic steel provided by this application can be made from C: 0.04% to 0.07%, Cr: 8.5% to 9.5%, W: 0.5% to 1.5%, V : 0.15% to 0.25%, Si: 0.1% to 0.2%, Mn: 0.3% to 0.6%, Ti: 0.16% to 0.28% and the balance Fe.

In the embodiment of the present application, the low activation ferritic steel may include C: 0.055% to 0.065%, Cr: 8.5% to 9%, W: 0.9% to 1%, and V: 0.2 in terms of mass percentage. % To 0.25%, Si: 0.13% to 0.15%, Mn: 0.4% to 0.5%, Ti: 0.18% to 0.23% and the balance Fe.

In the embodiment of the present application, in terms of mass percentage, the low activation ferritic steel may be C: 0.055% to 0.065%, Cr: 8.5% to 9%, W: 0.9% to 1%, V: 0.2 % To 0.25%, Si: 0.13% to 0.15%, Mn: 0.4% to 0.5%, Ti: 0.18% to 0.23% and the balance Fe.

In the embodiment of the present application, the mass ratio of Ti to C may be 3 to 4:1.

In the embodiment of the present application, in terms of mass percentage, the low activation ferritic steel can be composed of C: 0.06%, Cr: 9%, W: 1%, V: 0.2%, Si: 0.15%, Mn: Composition of 0.45%, Ti: 0.2% and the balance Fe.

In the embodiment of the present application, the low activation ferritic steel is a ferritic steel with an interphase precipitation morphology, there is basically no M ₂₃ C ₆ precipitation phase, and only the MX precipitation phase is used as the precipitation strengthening phase.

In the embodiment of the present application, the MX precipitated phases may be arranged in rows inside the grains of the low activation ferritic steel.

This application also provides a method for preparing the low activation ferritic steel as described above, including:

Preparing an alloy material containing C, Cr, W, V, Si, Mn, Ti and Fe in said mass percentage;

Austenitizing the alloy material;

The austenitized alloy material undergoes isothermal ferrite transformation;

After completing the isothermal ferrite transformation, cooling is performed.

In the embodiment of the present application, the temperature of the isothermal ferrite phase transformation may be 650° C. to 675° C., and the time may be 2.5 hours to 4 hours.

In the embodiment of the present application, the austenitizing temperature may be 980° C. to 1080° C., and the time may be 30 min or more.

This application introduces Ti element into the low activation ferrite steel, and deforms into a ferrite structure with interphase precipitation morphology through isothermal ferrite phase deformation. The characteristics of the structure are: (1) The matrix is a ferrite structure; (2) There is basically no M ₂₃ C ₆ precipitated phase in the structure (that is, no dense or continuous M ₂₃ C ₆ precipitated phase can be observed in the light microscope), Only the MX phase is used as the precipitation strengthening phase; (3) The precipitated MX phase has a typical interphase precipitation morphology, arranged in columns within the ferrite grains, and the arrangement density of the precipitated MX phase is much higher than that of the traditional quenched -Low activation ferritic steel obtained by tempering process. The existence of the above-mentioned interphase precipitation morphology improves the structural stability of low-activated ferritic steel under high-temperature service, thereby greatly improving its high-temperature creep resistance.

After testing, the room temperature hardness of the low activation ferritic steel of the present application is equivalent to that of the traditional low activation steel, and the high temperature strength and creep properties are better than or equivalent to the traditional low activation steel.

Other features and advantages of the present application will be described in the following description, and partly become clearer from the description, or understood by implementing the present application. Other advantages of the present application can be realized and obtained through the solutions described in the specification and the drawings.

Brief description of the drawings

The accompanying drawings are used to provide an understanding of the technical solution of the present application, and constitute a part of the specification. Together with the embodiments of the present application, they are used to explain the technical solution of the present application, and do not constitute a limitation to the technical solution of the present application.

Figure 1 is a light microscope picture of the low activation ferritic steel prepared in Example 1 of this application;

Figure 2 is a transmission electron microscope picture of the low activation ferritic steel prepared in Example 1 of the application;

Figure 3 is a light microscope picture of the low activation ferritic steel prepared in Example 2 of the application;

Fig. 4 is a transmission electron microscope picture of the low activation ferritic steel prepared in Example 2 of the application;

Figure 5 is a light microscope picture of the ferritic steel produced in Comparative Example 1 of the application;

Figure 6 is a light microscope picture of the ferritic steel produced in Comparative Example 2 of the application;

Fig. 7 is a curve of the high temperature strength of the low-activated ferritic steel prepared in Example 1 of the application and the current mainstream steel materials with temperature;

Fig. 8 is a comparison of the high-temperature creep performance of the low-activation ferritic steel prepared in Example 1 of the application and the current mainstream steel materials at a service temperature of 650°C;

Fig. 9 is the microhardness curve at room temperature of low-activated ferritic steel prepared at different isothermal ferrite transformation temperatures in the examples of the application.

Detail

In order to make the objectives, technical solutions, and advantages of the present application clearer, the embodiments of the present application will be described in detail below in conjunction with the accompanying drawings. It should be noted that the embodiments in the application and the features in the embodiments can be combined with each other arbitrarily if there is no conflict.

Example 1

In terms of mass percentage, the low activation ferritic steel of this embodiment is composed of 0.06% C, 9% Cr, 1% W, 0.2% V, 0.15% Si, 0.45% Mn, 0.2% Ti And the remainder of Fe matrix composition.

The low activation ferritic steel of this embodiment is prepared by the following method:

(1) Through smelting to obtain alloy materials containing the said mass percentage of C, Cr, W, V, Si, Mn, Ti and Fe, including using cast steel ingots for hot rolling after forging, and controlling the final rolling temperature at 840°C To 950°C, water cooled to room temperature after rolling;

(2) Put the alloy material obtained in step (1) into a muffle furnace, and hold it at 1050°C for 1 hour for austenitization;

(3) Holding the alloy material obtained in step (2) in a muffle furnace at 665° C. for 2.5 hours for isothermal ferrite transformation;

(4) The material after isothermal ferrite transformation is taken out from the muffle furnace and cooled to room temperature naturally.

The low-activation ferritic steel produced in Example 1 was commissioned by the Steel Research Institute of Nake Material Testing Center to test the element content in it, and the test method adopted was the spectroscopic method. The test results are shown in Table 1.

Table 1

element C Cr W V Si Mn Ti Fe Content, mass% 0.063 9.0 0.97 0.20 0.13 0.47 0.21 margin

It can be seen that the content of each element actually measured is equivalent to the design value.

Example 2

Embodiment 2 The difference of embodiment 1 is only:

The temperature of isothermal ferrite transformation in step (3) is 650°C, and the holding time is 3.5 hours.

Comparative example 1

The difference between this comparative example and Example 1 is only:

In terms of mass percentage, the ferritic steel of this comparative example consists of 0.1% C, 9% Cr, 1% W, 0.2% V, 0.15% Si, 0.45% Mn, 0.2% Ti and the rest The amount of Fe matrix composition; and

The temperature of isothermal ferrite transformation in step (3) is 650°C to 700°C.

Comparative example 2

The difference between this comparative example and Example 1 is only:

In terms of mass percentage, the ferritic steel of this comparative example consists of 0.1% C, 9% Cr, 1% W, 0.2% V, 0.15% Si, 0.45% Mn, 0.4% Ti and the rest The amount of Fe matrix composition.

Figure 1 is a light microscope picture of the low activation ferrite steel prepared in Example 1 of the application, and it can be seen that the alloy structure at room temperature is almost all ferrite. There are no coarse carbides precipitated inside the ferrite and on the grain boundaries.

Figure 2 is a transmission electron microscope picture of the low-activated ferritic steel prepared in Example 1 of the application. It can be seen that the low-activated ferritic steel has high-density nano-precipitated phases arranged in rows with a spacing of about 30nm. It has the typical characteristics of interphase precipitation. It is roughly estimated that the precipitation density of the nano-precipitated phase in Figure 2 is about 10 ²¹ /m ³ or above, which is much higher than the precipitation density in the tempered martensite documented in the literature of 10 ¹⁹ /m ³ -10 ²⁰ /m ³ (Reference [1]C.Dethloff,E.Gaganidze,J.Aktaa,Quantitative TEM analysis of precipitation and grain boundary segregation in neutron irradiated Eurofer97,J.Nucl.Mater.2014(454):323-331.[2 ]P.He, On the Structure-property Correlation and the Evolution of Nano-features in 12-13.5% Cr Oxide Dispersion Strengthened Ferritic Steels, Karlsruher Institute für Technology, 2014). After further characterization by EDS and 3DAP, it can be confirmed that the nano-precipitated phase in Figure 2 is TiC.

Figures 3 and 4 are the light microscope pictures and transmission electron microscope pictures of the low activation ferritic steel prepared in Example 2 of this application, respectively. It can be seen that there are also high-density nano-precipitates arranged in rows inside the sample, with interphase Typical characteristics of precipitation. In view of the great similarity between its structure and Example 1, it can be considered that the low activation ferritic steel prepared in Example 2 has the same performance as the low activation ferritic steel prepared in Example 1.

Fig. 5 is a light microscope picture of a ferritic steel prepared by ferritic phase transformation at 650°C in Comparative Example 1 of the application. It can be seen that a large amount of continuous and coarse M ₂₃ C ₆ precipitates at the ferrite grain boundary. Therefore, the ferrite material becomes brittle and has poor performance. The light microscope pictures at 675°C and 700°C are similar to those shown in Figure 5. The inventor of the present application believes that the reason for this phenomenon is that the C/Ti ratio is too high, resulting in that C cannot be completely consumed by Ti during the phase transition to generate TiC, and the remaining C can only be precipitated at the grain boundary in the form of _{M 23} C ₆ .

Fig. 6 is a light microscope picture of the ferritic steel prepared in Comparative Example 2 of the application, and it can be seen that a large amount of coarse TiC/N precipitates at the ferrite grain boundary. The inventor of the present application believes that the reason for this phenomenon is that although the C/Ti ratio of the material is 1:4, which is more suitable, the content of Ti is too high, and the affinity of Ti with C and N elements is extremely high, so If the Ti content is too high, a large amount of coarse TiC/N precipitation will inevitably form during the smelting process. This kind of precipitated phase is large in size and extremely high in melting point, which cannot be eliminated by subsequent heat treatment, which is extremely unfavorable to material properties.

Figure 7 shows the high-temperature strength of the low-activated ferritic steel produced in Example 1 of the application and the current mainstream steel materials at different temperatures. Figure 8 shows the low-activated ferritic steel produced in Example 1 of the application and the current mainstream steel materials. High temperature creep properties of steel materials at 650℃ service temperature. Among them, CLAM, EUROFER97, and F82H are structural steels for tempered martensitic fusion reactors developed by China, the European Union, and Japan, respectively, and P91 is the current mainstream engineering high-temperature steel (mainly used for thermal power generation equipment). It can be seen that the high temperature performance of the low activation ferritic steel of Example 1 of the present application is close to or even better than other mainstream similar materials at present, and has excellent application prospects.

Figure 9 is the microhardness curve at room temperature of low-activated ferrite steel prepared at different isothermal ferrite transformation temperatures, where the isothermal ferrite transformation temperature of 650°C corresponds to that produced in Example 2 Low-activated ferritic steels, low-activated ferritic steels corresponding to other temperatures are obtained by only changing the isothermal ferrite transformation temperature on the basis of Example 1. It can be seen that the room temperature hardness of the low-activated ferritic steel obtained by isothermal ferrite phase transformation at 650°C to 675°C is above 200HV, which is equivalent to the room temperature hardness of the traditional tempered martensitic low-activated steel.

The present disclosure is an example of the principles of the embodiments of the present application, and does not limit the present application in any form or substance, or limit the present application to specific embodiments. For those skilled in the art, it is obvious that the elements, methods, and systems of the technical solutions of the embodiments of the present application can be changed, changed, modified, and evolved without departing from the embodiments and technical solutions of the present application as described above. , As defined in the claims, the principle, spirit and scope. The implementation schemes of these changes, changes, modifications, and evolutions are all included in the equivalent embodiments of the present application, and these equivalent embodiments are all included in the scope defined by the claims of the present application. Although the embodiments of the present application can be embodied in many different forms, some embodiments of the present application are described in detail here. In addition, the examples of the present application include any possible combination of some or all of the various embodiments described herein, and are also included in the scope of the present application defined by the claims. All patents, patent applications and other cited materials mentioned in this application or anywhere in any cited patent, cited patent application or other cited materials are hereby incorporated by reference in their entirety.

The above disclosure is provided as illustrative rather than exhaustive. For those skilled in the art, this description will suggest many changes and alternatives. All these alternatives and variations are intended to be included within the scope of the claims, where the term "including" means "including, but not limited to."

This completes the description of the alternative implementations of the present application. Those skilled in the art may recognize other equivalent transformations of the embodiments described herein, and these equivalent transformations are also encompassed by the claims attached herein.

Claims (11)

A low-activated ferritic steel, in terms of mass percentage, the low-activated ferritic steel comprises C: 0.04% to 0.07%, Cr: 8.5% to 9.5%, W: 0.5% to 1.5%, and V: 0.15 % To 0.25%, Si: 0.1% to 0.2%, Mn: 0.3% to 0.6%, Ti: 0.16% to 0.28% and the balance Fe. The low activation ferritic steel according to claim 1, wherein, in terms of mass percentage, the low activation ferritic steel consists of C: 0.04% to 0.07%, Cr: 8.5% to 9.5%, and W: 0.5% To 1.5%, V: 0.15% to 0.25%, Si: 0.1% to 0.2%, Mn: 0.3% to 0.6%, Ti: 0.16% to 0.28% and the balance Fe. The low activation ferritic steel according to claim 1, wherein the low activation ferritic steel comprises C: 0.055% to 0.065%, Cr: 8.5% to 9%, and W: 0.9% in terms of mass percentage To 1%, V: 0.2% to 0.25%, Si: 0.13% to 0.15%, Mn: 0.4% to 0.5%, Ti: 0.18% to 0.23% and the balance Fe. The low-activated ferritic steel according to any one of claims 1 to 3, wherein, in terms of mass percentage, the low-activated ferritic steel ranges from C: 0.055% to 0.065%, and Cr: 8.5% to 9. %, W: 0.9% to 1%, V: 0.2% to 0.25%, Si: 0.13% to 0.15%, Mn: 0.4% to 0.5%, Ti: 0.18% to 0.23% and the balance Fe. The low-activated ferritic steel according to any one of claims 1 to 4, wherein, in terms of mass percentage, the low-activated ferritic steel can be composed of C: 0.06%, Cr: 9%, and W:1 %, V: 0.2%, Si: 0.15%, Mn: 0.45%, Ti: 0.2% and the balance Fe. The low activation ferritic steel according to any one of claims 1 to 4, wherein the mass ratio of Ti to C is 3 to 4:1. The low-activated ferritic steel according to any one of claims 1 to 6, wherein the low-activated ferritic steel is a ferritic steel with an interphase precipitation morphology, and there is substantially no M ₂₃ The C ₆ precipitated phase, and only the MX precipitated phase was used as the precipitation strengthening phase. The low-activation ferritic steel according to claim 7, wherein the MX precipitated phases are arranged in rows inside the crystal grains of the low-activation ferritic steel. The method for preparing low-activated ferritic steel according to any one of claims 1 to 8, comprising: Preparing an alloy material containing C, Cr, W, V, Si, Mn, Ti and Fe in said mass percentage; Austenitizing the alloy material; The austenitized alloy material undergoes isothermal ferrite transformation; After completing the isothermal ferrite transformation, cooling is performed. The preparation method according to claim 9, wherein the temperature of the isothermal ferrite transformation is 650°C to 675°C, and the time is 2.5 hours to 4 hours. The preparation method according to claim 9 or 10, wherein the austenitizing temperature is 980°C to 1080°C, and the time is more than 30 minutes.

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