CN120400711A - Boron-containing austenitic stainless steel for thermal neutron absorption - Google Patents
Boron-containing austenitic stainless steel for thermal neutron absorptionInfo
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Abstract
本发明提供了一种热中子吸收用含硼奥氏体不锈钢，以质量分数计，包括B：0.8～2.3%，Cr：18.0～20.0%，Ni：12.0～15.0%，Si≤0.75%，Mn：1.0～2.0%，Mo：0.05～0.10%，Cu：0.05～0.08%，C：0.01～0.03%，Ce：≤0.10%，Al：≤0.3%，Ca：0.001～0.004%，Ti和V其中之一或复合添加，剩余部分由Fe和不可避免的杂质构成。本发明提供的一种热中子吸收用含硼奥氏体不锈钢，通过对含硼奥氏体不锈钢中合金元素的优化设计及对其含量的优化控制，可以在保证含硼奥氏体不锈钢具有良好铸造性能的基础上，能够提高含硼奥氏体不锈钢的热塑性、韧性和耐晶间腐蚀性能。
The present invention provides a boron-containing austenitic stainless steel for thermal neutron absorption, comprising, by mass fraction, 0.8-2.3% B, 18.0-20.0% Cr, 12.0-15.0% Ni, ≤0.75% Si, 1.0-2.0% Mn, 0.05-0.10% Mo, 0.05-0.08% Cu, 0.01-0.03% C, ≤0.10% Ce, ≤0.3% Al, 0.001-0.004% Ca, one of Ti and V or a combination thereof, with the remainder consisting of Fe and unavoidable impurities. The boron-containing austenitic stainless steel for thermal neutron absorption provided by the present invention improves the thermoplasticity, toughness, and intergranular corrosion resistance of the boron-containing austenitic stainless steel while ensuring good casting properties through optimized design of alloying elements in the boron-containing austenitic stainless steel and optimized control of their contents.
Description
Technical Field
The invention relates to the technical field of neutron absorbing materials in the nuclear industry, in particular to boron-containing austenitic stainless steel for thermal neutron absorption.
Background
With the rapid development of nuclear energy industry in China, the market demand of neutron absorbing materials is increased year by year, wherein boron stainless steel is used as a common neutron absorbing material, has excellent mechanical property, corrosion resistance and temperature resistance, and is widely applied to the fields of spent fuel storage and transportation, spent fuel post-treatment, reactor shielding and the like.
However, with the continuous improvement of the neutron absorption performance requirement of the material, more neutron absorber boron needs to be added into the material, but the addition of high-content boron has adverse effects on the hot/cold forming processability, mechanical properties and corrosion resistance of the boron stainless steel. Because after adding high boron content in steel, a net-shaped continuous hard and brittle boride eutectic structure is easy to form around matrix grains when the stainless steel is solidified, the thermoplastic property and mechanical property of the material are remarkably deteriorated, and the loss of matrix Cr element in the vicinity of the boride (Cr, fe) 2 B also weakens the corrosion resistance of the material along with the mass production of boride (Cr, fe) 2 B.
At present, the optimal design of alloy components is an effective way for improving the performance of the boron stainless steel material. Aiming at the problems of poor hot workability and the like of high-boron stainless steel, china patent CN102051531A discloses a high-boron austenitic stainless steel （Cr：18.5～21.0wt.%,Ni：12.5～15.0wt.%,B：1.7～2.0 wt.%,C：0.01～0.05 wt.%,Ti：0.06～0.15 wt.%,Mo≤0.5%,Si≤1.0%,Mn≤2.0%,Ce：0.07～0.15 wt.%） and a manufacturing method thereof, and by adding rare earth elements Ce and Ti, the morphology of inclusions can be effectively improved, the as-cast structure, boride size and distribution condition are refined, and a good foundation is laid for reducing or avoiding edge cracking in the hot working process and improving various properties of materials. In China patent CN115216690A（Cr：18.5～19.0wt.%,Ni：12.5～13.0wt.%,B：2.1～2.2 wt.%,C：0.03～0.05 wt.%,Ti：2.5～3.5 wt.%,Mn：1.5～1.7 wt.%,Si：0.50～0.60wt.%）, high-content Ti element is introduced, tiB 2 is promoted to be generated through the content regulation and control of Ti, cr and B elements, the effective control of the content of second-phase Cr 2 B in the boron stainless steel is realized, and the prepared material has good comprehensive performance. In order to further improve the corrosion resistance of the boron stainless steel, the Chinese patent CN115807197A（Cr：13.0～16.0wt.%,B：0.8～2.3wt.%,C：0.02～0.06wt.%,Ti：1.50～5.60wt.%,V：0.15～0.30wt.%,Mn：0.20～0.50wt.%,Ni：0.10～0.50wt.%,Al：0.10～0.50wt.%,W：0.01～0.10wt.%,Cu：0.05～0.15wt.%,Mo：0.02～0.06wt.%,Ce：≤0.25wt.%） realizes the further optimization of the intergranular corrosion resistance of the material by reducing the precipitation and precipitation of Cr 2 B at the grain boundary as much as possible through the proper addition of alloy elements such as W, cu, mo and the like on the basis of introducing high-content Ti element. JP06192792A adopts similar means, and by controlling the second phase component and the content, the introduction of rare earth elements, mo, W, V and other elements realizes the effective improvement of corrosion resistance and hot working performance of the boron stainless steel. The main alloy element of the boron stainless steel is one or the combination of ：C：≤0.02wt.%,Si：≤0.5wt.%,Mn：≤2wt.%,Ni：10～22wt.%,Cr：18～26wt.%,B：≤3.0wt.%,Mg：≤0.1wt.%,Al：≤0.5wt.%,Gd：0.05～1.0wt.%,0.1～5wt.% of Mo, W and V, cd is less than or equal to 1 wt%, sm is less than or equal to 1 wt% and Eu is less than or equal to 1 wt%, one or the combination of Ti, zr and Nb is 0.1-5 wt%, and the balance is iron and unavoidable impurities.
In patent CN115216690A, CN115807197a and JP06192792a, by introducing high content of Ti element, massive formation of hard and brittle boride eutectic structure is avoided, and the comprehensive properties of the prepared boron stainless steel are effectively improved. However, in the process of casting and shaping the boron stainless steel, the introduced Ti element optimizes boride structure and simultaneously generates a large amount of high-melting-point titanium compound so as to easily cause the viscosity increase of molten steel, and the quality of the manufactured billet is difficult to be effectively ensured. In addition, the large amount of titanium boride particles in the matrix can also cause the surface hardness of the boron stainless steel to be obviously increased, and the processing difficulty and the manufacturing cost of the material are increased. In addition, the proper amount of Si and Al elements is introduced as important alloy elements in the stainless steel, which plays an important role in optimizing the comprehensive performance of the boron stainless steel material, and the boron stainless steel of the patent lacks control over the content of the Si and Al alloy elements and does not deeply discuss the influence of the content control of the Si and Al on the technological performance and corrosion performance of the material.
Accordingly, there is currently a need to further optimize the respective alloying element content for boron-containing austenitic stainless steel to obtain higher quality boron stainless steel materials.
Disclosure of Invention
The invention aims to solve the technical problem of providing the boron-containing austenitic stainless steel for thermal neutron absorption with high performance, and the thermoplastic property, toughness and intergranular corrosion resistance of the boron-containing austenitic stainless steel are improved on the basis of ensuring good casting performance of the boron-containing austenitic stainless steel by optimizing design and content control of alloy elements in the boron-containing austenitic stainless steel.
In order to solve the technical problems, the invention provides boron-containing austenitic stainless steel for thermal neutron absorption, which comprises B：0.8～2.3%,Cr：18.0～20.0%,Ni：12.0～15.0%,Si≤0.75%,Mn：1.0%～2.0%,Mo：0.05～0.10%, Cu：0.05～0.08%,C：0.01～0.03%,Ce≤0.10%,Al≤0.3%,Ca：0.001～0.004%,Ti or/and V less than or equal to 0.1 percent by mass and the balance of Fe and unavoidable impurities.
Further, the content of the Ce element is 0.03-0.08%.
Further, the content of Si element is 0.1-0.4%.
Further, the content of the Al element is 0.1-0.3%.
Further, the Ti element content, the V element content or the sum of the Ti element and the V element content is not higher than 0.1%.
Further, the ratio of Mn to Si element content is controlled to be 3.0-5.0.
Further, the impurity comprises N, co, O, S, P elements, and the sum of the impurity contents is less than or equal to 0.5%.
Further, the content of N element is less than or equal to 0.08%, the content of Co element is less than or equal to 0.20%, the content of O element is less than or equal to 0.01%, the content of S element is less than or equal to 0.01%, and the content of P element is less than or equal to 0.04%.
Further, the preparation raw materials of the boron-containing austenitic stainless steel comprise pure iron, metallic chromium, electrolytic nickel and ferroboron, wherein the Co content in the electrolytic nickel is less than or equal to 0.08%, the boron content in the ferroboron is more than or equal to 20%, and the 10 B abundance is more than or equal to 19.6%.
Further, the boron-containing austenitic stainless steel is prepared into billets by a method comprising casting and spray forming, or is prepared into boron-containing austenitic stainless steel profiles by a method comprising powder preparation by an air atomization method and powder metallurgy.
According to the boron-containing austenitic stainless steel for thermal neutron absorption, the grain size of matrix grains and boride can be thinned through the optimization design and control of alloy elements and content of the boron-containing austenitic stainless steel, and the comprehensive performance of the boron stainless steel material is effectively improved. By introducing proper amounts of Al, mo and Cu elements into the boron-containing austenitic stainless steel and reasonably controlling the contents of Si and C, the intergranular corrosion resistance of the material can be improved. Meanwhile, the solidification forming performance of the material can be improved by controlling the forms of inclusions, primary crystal structures and the like in the boron-containing austenitic stainless steel. Specifically, the composition mechanism of the boron-containing austenitic stainless steel for thermal neutron absorption provided by the invention is as follows:
Cr and Ni are main alloy elements in austenitic steel, and the control of the content of the Cr and Ni elements plays an important role in controlling the crystal structure of stainless steel and ensuring that the material has good corrosion resistance and plasticity. But at the same time, the manufacturing cost of the boron stainless steel material is avoided from being increased due to the excessively high Cr and Ni contents. Therefore, the boron-containing austenitic stainless steel for thermal neutron absorption provided by the invention has the Cr content controlled to be 18.0-20.0% and the Ni content controlled to be 12.0-15.0%.
The mechanical strength of the stainless steel can be improved by introducing the C element into the matrix alloy. However, with further increase of the C content, a large amount of carbide is precipitated at the grain boundary, and the corrosion resistance and hot workability of the material are remarkably deteriorated. Therefore, the boron-containing austenitic stainless steel for thermal neutron absorption provided by the invention controls the C content to be 0.01-0.03%.
Si is a ferrite forming element and plays a role in deoxidization in the alloy smelting process. When the Si content is lower than 0.8%, the activity of C in the matrix is increased along with the addition of Si element, and the precipitation of chromium carbide at the crystal boundary is initiated, so that Cr element at the crystal boundary is depleted, and the corrosion resistance and mechanical property of the alloy are deteriorated. Further, as Si element is introduced, it is necessary to consider the problem that the high melting point inclusion SiO 2 formed causes significant decrease in the fluidity of molten steel. Therefore, the boron-containing austenitic stainless steel for thermal neutron absorption provided by the invention controls the Si content to be 0.1-0.4%.
Mn is used as a weak austenite element, and Mn element is added into a matrix to play a role in stabilizing austenite. And the Mn element can form solid solution in the alloy, so that the hardness and strength of the stainless steel are optimized. At the same time Mn can also react with oxygen to form stable oxides. When the Mn-Si alloy is used together with Si, liquid manganese silicate can be formed by controlling the content of Mn and Si elements, and the influence of solid SiO 2 generated in molten steel on the fluidity of the molten steel is effectively avoided. However, when the Mn content is > 2.0%, the tendency of intermetallic compounds increases while the corrosion resistance of the material is lowered. Therefore, the boron-containing austenitic stainless steel for thermal neutron absorption provided by the invention controls the Mn content to be 1.0% -2.0%.
When a proper amount of Al element is introduced into the matrix alloy to deoxidize, most of Al is dissolved in the matrix, and Al 2O3 with good electrochemical stability is formed in the stainless steel corrosion process to form a surface passivation film together with chromium-rich oxide, so that the corrosion resistance of the stainless steel can be effectively improved. However, excessive addition of Al element brings about a decrease in the stability of matrix austenite, which adversely affects the mechanical properties of the material. Therefore, the boron-containing austenitic stainless steel for thermal neutron absorption provided by the invention controls the Al content to be 0.1-0.3%.
The molten steel is deoxidized to form Al 2O3 due to the introduction of Al element, so that the fluidity of the molten steel is poor. Therefore, the addition of Ca element in proper amount in the smelting process can effectively promote the denaturation of aluminum-rich solid inclusion in molten steel to form liquid inclusion which is easy to float upwards, purify molten steel and improve the fluidity of molten steel. However, excessive addition of Ca causes deterioration of mechanical properties of the material while adversely affecting its weldability. Therefore, the boron-containing austenitic stainless steel for thermal neutron absorption provided by the invention controls the Ca content to be 0.001-0.004%.
And a proper amount of rare earth element Ce is added in the smelting process, so that harmful substances such as oxygen, sulfur, phosphorus and the like in molten steel can be effectively removed, and the molten steel is purified. Meanwhile, ce forms a tiny high-melting-point compound (such as Ce 2O2 S) with elements such as oxygen and sulfur, so that the Ce becomes a heterogeneous nucleation core during solidification, is favorable for obviously refining a matrix grain structure, has the effect of improving boride morphology and distribution, and further realizes the improvement of hot processing performance, mechanical performance and corrosion resistance of the material. In addition, in the forming process of the boron stainless steel, the rare earth Ce can reduce the flow resistance of the alloy by refining primary crystal tissues while optimizing the morphology and distribution of inclusions, so that the fluidity of molten steel is further optimized. However, the manufacturing cost of the boron-containing austenitic stainless steel material is also considered, so that the Ce content of the boron-containing austenitic stainless steel for thermal neutron absorption is controlled to be 0.03-0.08%.
Ti or V is used as a stabilizing element and is added into a matrix to be easily combined with N element to form nitride, and is used as a non-spontaneous core to promote nucleation and refine solidification structures, meanwhile, ti and V can react with C, crC at a grain boundary is avoided, cr element loss in the matrix is reduced, and the method has certain beneficial effects on optimizing the hot processing performance, mechanical performance and corrosion resistance of the material. However, the addition of a large amount of Ti and V elements will result in the formation of a large amount of boride particles with a high melting point, resulting in an increase in the viscosity of molten steel, and therefore, the boron-containing austenitic stainless steel for thermal neutron absorption provided by the present invention controls the Ti element content, V element content, or the sum of the Ti element and V element content to not more than 0.1%.
Mo element is added into the matrix alloy, so that the passivation performance of the stainless steel can be improved, the intergranular corrosion tendency of the stainless steel is reduced, and meanwhile, the method has a certain beneficial effect on improving the heat resistance of the steel. However, excessive addition of Mo tends to increase ferrite in stainless steel, and decreases toughness of steel, and at the same time, the increase in Mo content affects viscosity of molten steel, deteriorating casting performance of the material. Therefore, the boron-containing austenitic stainless steel for thermal neutron absorption provided by the invention controls the Mo content to be 0.05-0.10%.
The strength and corrosion resistance of the steel can be improved by adding a small amount of Cu element into the matrix alloy. Therefore, the boron-containing austenitic stainless steel for thermal neutron absorption provided by the invention controls the Cu content to be 0.05-0.08%.
Besides O, S, P and other common impurities, N, co element is also an unavoidable impurity element in the boron stainless steel, and the content of the N, co element is strictly controlled. The method avoids the generation of a hard and brittle phase by the reaction of impurity N and B elements, deteriorates the mechanical property and the hot processing property of the material, reduces the content of Co element by controlling the material source item, and avoids the generation of secondary gamma rays after the material is irradiated by neutrons, thereby bringing harm to equipment and personnel safety. Therefore, the boron-containing austenitic stainless steel for thermal neutron absorption provided by the invention controls the total content of impurity elements including N, co, O, S, P and the like to be not higher than 0.5%.
The boron-containing austenitic stainless steel for thermal neutron absorption provided by the invention has the following advantages and beneficial effects:
Firstly, the boron-containing austenitic stainless steel for thermal neutron absorption provided by the invention can effectively refine the grain structure of a matrix, improve the morphology and distribution conditions of inclusions and boride and improve the thermal processing performance, mechanical performance and corrosion resistance of the material by adding elements such as Ce, ti, V and the like into the matrix alloy in proper quantity. By controlling the content of C and Si elements in the matrix alloy, a large amount of carbide particles are prevented from precipitating at the grain boundary. Meanwhile, al, mo and Cu elements are properly introduced, so that the corrosion resistance of the material is further optimized.
Secondly, according to the boron-containing austenitic stainless steel for thermal neutron absorption, provided by the invention, the form and the distribution condition of inclusions in molten steel are effectively optimized by adding elements such as Ca, mn, ce and the like in a proper amount and controlling the Mn/Si ratio, so that adverse effects on the flow property of materials caused by the generation of a large number of high-melting-point inclusions are avoided. Meanwhile, elements such as Ce, ti, V and the like are properly introduced into the matrix alloy to refine the primary crystal structure, so that the casting forming performance of the boron stainless steel is further optimized. The high-quality billet can be prepared by the boron stainless steel through the modes of casting, spray forming and the like, and the boron stainless steel section can also be prepared by the modes of powder preparation by an air atomization method, powder metallurgy and the like.
Furthermore, the boron-containing austenitic stainless steel for thermal neutron absorption provided by the invention can strictly control the impurity content of N, S, P, O and the like while regulating and controlling the base alloy components, and can effectively reduce the adverse effects of the generation of high-melting-point nonmetallic inclusions on the material technological properties, mechanical properties and corrosion resistance. By controlling the content of Co impurity in the alloy, the secondary gamma rays generated after the material is irradiated by neutrons can be avoided, and the harm to equipment and personnel safety is brought.
Therefore, the boron-containing austenitic stainless steel for thermal neutron absorption improves the thermoplasticity, toughness and intergranular corrosion resistance of the boron-containing austenitic stainless steel on the basis of ensuring good casting performance of the boron-containing austenitic stainless steel through the optimized design of alloy elements in the boron-containing austenitic stainless steel and the optimized control of the element content of the boron-containing austenitic stainless steel.
Drawings
FIG. 1 is a diagram showing the metallographic structure of a boron-containing austenitic stainless steel ingot obtained in comparative example 1 provided by the present invention;
FIG. 2 is a diagram showing the metallographic structure of a boron-containing austenitic stainless steel ingot obtained in comparative example 2, provided by the present invention;
FIG. 3 is a diagram showing the metallographic structure of a boron-containing austenitic stainless steel ingot obtained in comparative example 3, provided by the present invention;
FIG. 4 is a scanning electron microscope image of a boron-containing austenitic stainless steel sheet material obtained in comparative example 4, provided by the present invention;
FIG. 5 is a graph of the energy spectrum analysis of the boron-containing austenitic stainless steel sheet material obtained in comparative example 4 provided by the present invention;
FIG. 6 is a diagram showing the metallographic structure of a boron-containing austenitic stainless steel ingot obtained in example 3 provided by the present invention;
FIG. 7 is a metallographic structure of a boron-containing austenitic stainless steel sheet obtained in example 4 provided by the present invention;
FIG. 8 is a scanning electron microscope image of a boron-containing austenitic stainless steel sheet material obtained in example 4 provided by the present invention;
FIG. 9a is a view showing a metallographic structure of a boron-containing austenitic stainless steel sheet obtained in comparative example 4 according to the present invention after intergranular corrosion;
FIG. 9b is a view showing a metallographic structure of a boron-containing austenitic stainless steel sheet obtained in comparative example 5 according to the present invention after intergranular corrosion;
FIG. 9c is a view showing a metallographic structure of a boron-containing austenitic stainless steel sheet obtained in comparative example 6 according to the present invention after intergranular corrosion;
FIG. 9d is a diagram showing the metallographic structure of a boron-containing austenitic stainless steel sheet obtained in example 4 according to the present invention after intergranular corrosion;
fig. 10 is a graph showing the surface distribution of chromium element in the boron-containing austenitic stainless steel sheet obtained in example 4 provided by the present invention.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the present invention more apparent, the present invention will be further described in detail with reference to the following comparative examples, examples and drawings, the illustrative embodiments of the present invention and the descriptions thereof are only for explaining the present invention and are not limiting the present invention.
Comparative example 1
The boron-containing austenitic stainless steel for thermal neutron absorption provided in this comparative example contains B：1.16%,Cr：18.6%,Ni：12.7%,Si：0.72%,Mn：1.07%,Mo：0.07%,Cu：0.06%,C：0.05%,Ce：0.08%,Al：0.20%,Ca：0.003%,Ti：0.06%, in mass fraction, the remainder consisting of Fe and unavoidable impurities.
Wherein, in the boron-containing austenitic stainless steel, the mass percentage of Mn and Si is 1.5.
Wherein, the content of impurities in the boron-containing austenitic stainless steel is less than or equal to 0.20 percent by mass percent, wherein, the content of N, O, S and P elements is less than 0.01 percent, and the content of Co element is less than 0.1 percent.
When the smelting process is adopted to prepare the boron stainless steel ingot and the casting temperature is 1570+/-10 ℃, casting defects such as certain air holes, shrinkage cavities and the like exist in the prepared ingot.
The metallographic structure of the boron-containing austenitic stainless steel ingot obtained in the comparative example of the present invention is shown in fig. 1.
Comparative example 2
The boron-containing austenitic stainless steel for thermal neutron absorption provided by the comparative example comprises, by mass, 1.19% of B, 18.7% of Cr, 12.3% of Ni, 0.30% of Si, 1.34% of Mn, 0.08% of Mo, 0.07% of Cu, 0.03% of C, 0.07% of Ce, 0.18% of Al, 0.05% of Ti, and the balance of Fe and unavoidable impurities.
Wherein, in the boron-containing austenitic stainless steel, the mass percentage of Mn and Si is 4.5.
Wherein, the content of impurities in the boron-containing austenitic stainless steel is less than or equal to 0.20 percent by mass percent, wherein, the content of N, O, S and P elements is less than 0.01 percent, and the content of Co element is less than 0.1 percent.
When the smelting process is adopted to prepare the boron stainless steel ingot and the casting temperature is 1570+/-10 ℃, casting defects such as certain air holes, shrinkage cavities and the like exist in the prepared ingot.
The metallographic structure of the boron-containing austenitic stainless steel ingot obtained in the comparative example of the present invention is shown in fig. 2.
Comparative example 3
The boron-containing austenitic stainless steel for thermal neutron absorption provided by the comparative example comprises, by mass, 1.46% of B, 18.8% of Cr, 12.3% of Ni, 0.31% of Si, 1.34% of Mn, 0.08% of Mo, 0.07% of Cu, 0.03% of C, 0.13% of Al, 0.003% of Ca, 0.06% of Ti, and the balance of Fe and unavoidable impurities.
Wherein, in the boron-containing austenitic stainless steel, the mass percentage of Mn and Si is 4.3.
Wherein, the content of impurities in the boron-containing austenitic stainless steel is less than or equal to 0.20 percent by mass percent, wherein, the content of N, O, S and P elements is less than 0.01 percent, and the content of Co element is less than 0.1 percent.
The boron stainless steel ingot is prepared by adopting a smelting process, and when the casting temperature is 1550+/-10 ℃, the prepared ingot has better internal quality.
The metallographic structure of the boron-containing austenitic stainless steel ingot obtained in the comparative example of the present invention is shown in fig. 3.
Comparative example 4
The boron-containing austenitic stainless steel for thermal neutron absorption provided in this comparative example contains B：1.71%,Cr：18.6%,Ni：12.8%,Si：0.32%,Mn：1.38%,Mo：0.08%,Cu：0.06%,C：0.08%,Ce：0.07%,Al：0.13%,Ca：0.003%,Ti：0.05%, in mass fraction, the remainder consisting of Fe and unavoidable impurities.
Wherein, in the boron-containing austenitic stainless steel, the mass percentage of Mn and Si is 4.3.
Wherein, the content of impurities in the boron-containing austenitic stainless steel is less than or equal to 0.20 percent by mass percent, wherein, the content of N, O, S and P elements is less than 0.01 percent, and the content of Co element is less than 0.1 percent.
The boron stainless steel cast ingot is prepared by adopting a smelting process, and the prepared cast ingot has good quality when the casting temperature is 1540+/-10 ℃.
Based on the alloy components, a smelting, forging and rolling process is adopted to prepare the boron stainless steel plate.
Scanning electron microscope images and energy spectrum analysis images of the boron-containing austenitic stainless steel plate obtained in the comparative example are shown in fig. 4 and 5.
The boron-containing austenitic stainless steel plate obtained in the comparative example of the invention is subjected to an intergranular corrosion test in an H 2SO4+CuSO4 medium, and after 15 hours of the corrosion test, the metallographic structure of the plate is shown in figure 9 a.
Comparative example 5
The boron-containing austenitic stainless steel for thermal neutron absorption provided by the comparative example comprises, by mass, 1.68% of B, 18.8% of Cr, 13.1% of Ni, 0.33% of Si, 1.32% of Mn, 0.06% of Mo, 0.06% of Cu, 0.02% of C, 0.07% of Ce, 0.06% of Ti, and the balance of Fe and unavoidable impurities.
Wherein, in the boron-containing austenitic stainless steel, the mass percentage of Mn and Si is 4.0.
Wherein, the content of impurities in the boron-containing austenitic stainless steel is less than or equal to 0.20 percent by mass percent, wherein, the content of N, O, S and P elements is less than 0.01 percent, and the content of Co element is less than 0.1 percent.
The boron stainless steel cast ingot is prepared by adopting a smelting process, and the prepared cast ingot has good quality when the casting temperature is 1540+/-10 ℃.
Based on the alloy components, the boron stainless steel plate is prepared by adopting smelting, forging and rolling processes.
The boron-containing austenitic stainless steel plate obtained in the comparative example of the present invention is subjected to an intergranular corrosion test in a H 2SO4+CuSO4 medium, and after 15 hours of the corrosion test, the metallographic structure of the plate is shown in FIG. 9 b.
Comparative example 6
The boron-containing austenitic stainless steel for thermal neutron absorption provided by the comparative example comprises, by mass, 1.66% of B, 19.0% of Cr, 13.5% of Ni, 0.60% of Si, 1.82% of Mn, 0.06% of Mo, 0.06% of Cu, 0.02% of C, 0.06% of Ce, 0.05% of Ti, and the balance of Fe and unavoidable impurities.
Wherein, in the boron-containing austenitic stainless steel, the mass percentage of Mn and Si is 3.0.
Wherein, the content of impurities in the boron-containing austenitic stainless steel is less than or equal to 0.20 percent by mass percent, wherein, the content of N, O, S and P elements is less than 0.01 percent, and the content of Co element is less than 0.1 percent.
The boron stainless steel cast ingot is prepared by adopting a smelting process, and the prepared cast ingot has good quality when the casting temperature is 1540+/-10 ℃.
Based on the alloy components, the boron stainless steel plate is prepared by adopting smelting, forging and rolling processes.
The boron-containing austenitic stainless steel plate obtained in the comparative example of the invention is subjected to an intergranular corrosion test in an H 2SO4+CuSO4 medium, and after 15 hours of the corrosion test, the metallographic structure of the plate is shown in figure 9 c.
Example 1
The boron-containing austenitic stainless steel for thermal neutron absorption provided in this example 1 contains B：1.24%,Cr：18.8%,Ni：13.0%,Si：0.31%,Mn：1.23%,Mo：0.08%,Cu：0.07%,C：0.02%,Ce：0.07%,Al：0.12%,Ca：0.003%,Ti：0.06%,, the remainder consisting of Fe and unavoidable impurities, in mass fraction.
Wherein, in the boron-containing austenitic stainless steel, the mass percentage of Mn and Si is 4.0.
Wherein, the content of impurities in the boron-containing austenitic stainless steel is less than or equal to 0.20 percent by mass percent, wherein, the content of N, O, S and P elements is less than 0.01 percent, and the content of Co element is less than 0.1 percent.
The boron stainless steel cast ingot is prepared by adopting a smelting process, and the prepared cast ingot has good quality when the casting temperature is 1570+/-10 ℃.
Example 2
The boron-containing austenitic stainless steel for thermal neutron absorption provided in this example 2 contains B：1.18%,Cr：18.7%,Ni：12.8%,Si：0.30%,Mn：1.21%,Mo：0.08%,Cu：0.06%,C：0.01%,Ce：0.06%,Al：0.15%,Ca：0.002%,V：0.05%, in mass fraction, the remainder consisting of Fe and unavoidable impurities.
Wherein, in the boron-containing austenitic stainless steel, the mass percentage of Mn and Si is 4.0.
Wherein, the content of impurities in the boron-containing austenitic stainless steel is less than or equal to 0.20 percent by mass percent, wherein, the content of N, O, S and P elements is less than 0.01 percent, and the content of Co element is less than 0.1 percent.
The boron stainless steel cast ingot is prepared by adopting a smelting process, and the prepared cast ingot has good quality when the casting temperature is 1570+/-10 ℃.
The casting properties of the resulting boron stainless steels of comparative example 1, example 1 and example 2 were compared for different Mn/Si ratios at similar boron contents. Under the same temperature condition, when the Mn/Si ratio of the embodiment 1 and the embodiment 2 is more than 3.0, the fluidity in the molten steel pouring process is better, and the prepared cast ingot has good solidification molding quality. Whereas when the Mn/Si ratio of comparative example 1 was 1.5, the fluidity of molten steel was relatively poor, and significant void defects were observed in the produced boron stainless steel ingot, as shown in fig. 1.
At similar boron content, comparative example 2, example 1 and example 2 were compared for the effect on the quality of the produced boron stainless steel ingot when Ca element was introduced. It can be seen that the cast ingots produced in comparative example 2 had more casting defects inside compared with examples 1 and 2, as shown in fig. 2. The defects of shrinkage cavity, air hole and the like in the solidification shrinkage process of the molten steel are caused by poor molten steel fluidity in the casting process of the cast ingot. The Ca element is introduced to improve the fluidity of the molten steel and further improve the solidification forming quality of the molten steel.
Example 3
The boron-containing austenitic stainless steel for thermal neutron absorption provided in this example 3 contains B：1.48%,Cr：18.7%,Ni：13.3%,Si：0.32%,Mn：1.38%,Mo：0.06%,Cu：0.07%,C：0.02%,Ce：0.08%,Al：0.10%,Ca：0.003%,Ti：0.05%, in mass fraction, the remainder consisting of Fe and unavoidable impurities.
Wherein, in the boron-containing austenitic stainless steel, the mass percentage of Mn and Si is 4.3.
Wherein, the content of impurities in the boron-containing austenitic stainless steel is less than or equal to 0.20 percent by mass percent, wherein, the content of N, O, S and P elements is less than 0.01 percent, and the content of Co element is less than 0.1 percent.
The boron stainless steel cast ingot is prepared by adopting a smelting process, and the quality of the prepared cast ingot is good when the casting temperature is 1550+/-10 ℃.
The metallographic structure of the boron-containing austenitic stainless steel cast ingot obtained by the embodiment of the invention is shown in figure 6.
Comparing the ingot tissue obtained by adding the rare earth element in the embodiment of the invention with the ingot tissue obtained by not adding the rare earth element in the comparative example 3, it can be seen that the addition of the Ce element in the embodiment of the invention can effectively refine the matrix grains and boride tissue, and the distribution condition of the boron-containing phase is further improved.
Example 4
The boron-containing austenitic stainless steel for thermal neutron absorption provided in this example 4 contains B：1.89%,Cr：19.90%,Ni：13.40%,Si：0.29%,Mn：1.05%,Mo：0.06%,Cu：0.06%,C：0.01%,Ce：0.05%,Al：0.13%,Ca：0.002%,V：0.06%, in terms of mass fraction, and the remainder is composed of Fe and unavoidable impurities.
Wherein, in the boron-containing austenitic stainless steel, the mass percentage of Mn and Si is 3.6.
Wherein, the content of impurities in the boron-containing austenitic stainless steel is less than or equal to 0.20 percent by mass percent, wherein, the content of N, O, S and P elements is less than 0.01 percent, and the content of Co element is less than 0.1 percent.
The boron stainless steel cast ingot is prepared by adopting a smelting process, and the prepared cast ingot has good quality when the casting temperature is 1530+/-10 ℃.
Based on the alloy components, a smelting, forging and rolling process is adopted to prepare the boron stainless steel plate.
The metallographic structure of the boron-containing austenitic stainless steel plate obtained by the embodiment of the invention is shown in figure 7. The fine boride in the plate is uniformly dispersed in a stainless steel matrix, and the prepared plate has room temperature tensile strength of 589 MPa, yield strength of 406 MPa and elongation of 12.5 percent, and has good plasticity and toughness.
The boron-containing austenitic stainless steel plate obtained by the embodiment of the invention is subjected to an intergranular corrosion test in an H 2SO4+CuSO4 medium, and after 15 hours of the corrosion test, the metallographic structure of the plate is shown as a figure 9 d.
Comparison of the intergranular corrosion properties of the boron-containing austenitic stainless steel sheets obtained in example 4 of the present invention and comparative examples 4, 5 and 6, the effect of C, si content differences and Al element addition on the corrosion properties of the boron stainless steel was examined.
The boron-containing austenitic stainless steel plates obtained in the examples 4, 5 and 6 of the present invention were subjected to an intergranular corrosion test in a medium H 2SO4+CuSO4, and after 15 hours of the corrosion test, metallographic structure observation was performed on the cross section of the sample of the boron-containing austenitic stainless steel plate after corrosion, and the experimental results are shown in FIG. 9.
The results show that the sample of the boron-containing austenitic stainless steel plate of the comparative example 4 has obvious intergranular corrosion, the section of the sample forms continuous crack defects along the grain boundary, the crack defects formed by the intergranular corrosion can be observed in the local area near the surface of the section of the sample of the boron-containing austenitic stainless steel plate of the comparative example 5 and the sample of the boron-containing austenitic stainless steel plate of the comparative example 6, and the sample of the boron-containing austenitic stainless steel plate of the embodiment has no obvious intergranular corrosion and has good corrosion resistance.
Referring to fig. 4, the original sample of the boron-containing austenitic stainless steel sheet of comparative example 4 was characterized by a scanning electron microscope, and at a carbon content of 0.8%, the boron stainless steel sample was able to observe a large amount of precipitation of chromium carbide particles along grain boundaries, forming chromium-depleted regions near the grain boundaries, resulting in a difference in corrosion potential at the grain boundaries and an intra-grain potential, thereby causing intergranular corrosion.
The original sample of the boron-containing austenitic stainless steel plate in the embodiment 4 of the present invention is characterized by using a scanning electron microscope, and a scanning electron microscope diagram of the boron-containing austenitic stainless steel plate obtained in the embodiment of the present invention is shown in fig. 8.
FIG. 8 shows that at a carbon content of 0.01wt.%, no chromium carbide particle formation was observed inside the boron stainless steel sample of inventive example 4.
Comparison of the present example 4 and the comparative example 4 shows that the difference of carbon content is a main factor causing the difference of the intergranular corrosion performance of the boron stainless steel, and that the strict control of the carbon content (C≤0.03 0.03 wt%) in the stainless steel is an effective way to optimize the corrosion resistance of the material.
And, under the same low carbon content condition, the intergranular corrosion performance of the boron-containing austenitic stainless steel plates obtained in the comparative examples 4,5 and 6 can be seen that the higher silicon content has a certain adverse effect on the intergranular corrosion performance of the boron-containing austenitic stainless steel, and the proper introduction of the aluminum element can further optimize the corrosion resistance of the boron-containing austenitic stainless steel material.
The boron-containing austenitic stainless steel obtained in example 4 of the present invention was subjected to surface scanning analysis using an electron probe, and the surface distribution diagram of chromium element in the sheet is shown in fig. 10.
As can be seen from fig. 10, cr element is uniformly distributed in the stainless steel matrix, no formation of chromium-depleted zone is observed, and rapid development of corrosion in the stainless steel grain boundary zone is avoided.
According to the boron-containing austenitic stainless steel for thermal neutron absorption, the thermoplastic property, the toughness and the intergranular corrosion resistance of the boron-containing austenitic stainless steel can be improved on the basis of ensuring good casting performance of the boron-containing austenitic stainless steel through the optimized design of alloy elements in the boron-containing austenitic stainless steel and the optimized control of the content of the alloy elements.
Finally, it should be noted that the above-mentioned embodiments are only for illustrating the technical solution of the present invention, and not for limiting the same, and although the present invention has been described in detail with reference to examples, it should be understood by those skilled in the art that modifications and equivalents may be made to the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention, and all such modifications and equivalents are intended to be encompassed in the scope of the claims of the present invention.
Claims (10)
1. The boron-containing austenitic stainless steel for thermal neutron absorption is characterized by comprising B：0.8～2.3%,Cr：18.0～20.0%,Ni：12.0～15.0%,Si≤0.75%,Mn：1.0%～2.0%,Mo：0.05～0.10%, Cu：0.05～0.08%,C：0.01～0.03%,Ce≤0.10%,Al≤0.3%,Ca：0.001～0.004%,Ti or/and V less than or equal to 0.1 percent by mass and the balance of Fe and unavoidable impurities.
2. The boron-containing austenitic stainless steel for thermal neutron absorption according to claim 1, wherein the Ce element content is 0.03-0.08%.
3. The boron-containing austenitic stainless steel for thermal neutron absorption according to claim 1, wherein the Si element content is 0.1 to 0.4%.
4. The boron-containing austenitic stainless steel for thermal neutron absorption according to claim 1, wherein the content of Al element is 0.1-0.3%.
5. The boron-containing austenitic stainless steel for thermal neutron absorption according to claim 1, wherein the Ti element content, the V element content or the sum of the Ti element and V element content is not more than 0.1%.
6. The boron-containing austenitic stainless steel for thermal neutron absorption according to claim 1, wherein the ratio of Mn to Si element content is controlled to 3.0-5.0.
7. The boron-containing austenitic stainless steel for thermal neutron absorption according to claim 1, wherein the impurities include N, co, O, S, P elements, and the sum of the impurity contents is not more than 0.5%.
8. The boron-containing austenitic stainless steel for thermal neutron absorption according to claim 1, wherein the content of N element is not more than 0.08%, the content of Co element is not more than 0.20%, the content of O element is not more than 0.01%, the content of S element is not more than 0.01% and the content of P element is not more than 0.04%.
9. The boron-containing austenitic stainless steel for thermal neutron absorption according to claim 1, wherein the raw materials for preparing the boron-containing austenitic stainless steel comprise pure iron, metallic chromium, electrolytic nickel and ferroboron, wherein the Co content in the electrolytic nickel is less than or equal to 0.08%, the boron content in the ferroboron is more than or equal to 20%, and the 10 B abundance is more than or equal to 19.6%.
10. The boron-containing austenitic stainless steel for thermal neutron absorption according to claim 1, wherein the boron-containing austenitic stainless steel is prepared into billets by means of casting and spray forming, or is prepared into boron-containing austenitic stainless steel profiles by means of powder preparation by means of gas atomization and powder metallurgy.
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