CN107843509B - Method for estimating residual endurance life of supercritical unit T/P92 heat-resistant steel based on room-temperature Brinell hardness prediction - Google Patents
Method for estimating residual endurance life of supercritical unit T/P92 heat-resistant steel based on room-temperature Brinell hardness prediction Download PDFInfo
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Abstract
本发明涉及钢铁材料剩余持久寿命评估领域,尤其涉及一种基于室温布氏硬度预测超临界机组T/P92耐热钢剩余持久寿命评估方法。本发明通过以材料高温抗拉强度为桥梁,对持久断裂寿命和不同老化状态下室温布氏硬度HB建立对应关系,从而建立P92钢在给定温度和应力条件下室温布氏硬度与持久断裂时间之间关系的数学解析式。本发明通过简单便捷、无损的硬度测试即可快速、准确的预测当前材料在特定蒸汽参数下的剩余持久寿命,可直接免去因停机或管道切割等带来的经济损失,因其方便快捷的特点可以及时的评估T/P92耐热钢的剩余寿命可有效预防因材料老化失效导致的事故发生。The invention relates to the field of residual durable life evaluation of iron and steel materials, in particular to a residual durable life evaluation method of supercritical unit T/P92 heat-resistant steel based on room temperature Brinell hardness prediction. The invention establishes a corresponding relationship between the permanent fracture life and the room temperature Brinell hardness HB under different aging states by using the high temperature tensile strength of the material as a bridge, so as to establish the room temperature Brinell hardness and the permanent fracture time of P92 steel under given temperature and stress conditions. Mathematical analysis of the relationship between. The invention can quickly and accurately predict the remaining lasting life of the current material under specific steam parameters through a simple, convenient and non-destructive hardness test, and can directly avoid economic losses caused by downtime or pipe cutting. Features The remaining life of T/P92 heat-resistant steel can be evaluated in a timely manner, which can effectively prevent accidents caused by material aging and failure.
Description
技术领域technical field
本发明涉及钢铁材料剩余持久寿命评估领域,尤其涉及一种基于室温布氏硬度预测超临界机组T/P92耐热钢剩余持久寿命评估方法。The invention relates to the field of residual durable life evaluation of iron and steel materials, in particular to a residual durable life evaluation method of supercritical unit T/P92 heat-resistant steel based on room temperature Brinell hardness prediction.
背景技术Background technique
基于安全和经济性考虑,高温蠕变寿命的评估一直是耐热钢研发的重要课题。运行在实际条件下的金属材料往往受力很小,温度也较低,用这样的条件做实验,虽然可以直接得到在服役条件下的使用寿命,但要耗掉大量的时间,有时是几年,甚至十几年。为了缩短时间,必须提高实验应力或温度,即采用加速实验法,然后用外推的方法确定使用条件下的剩余寿命。所得结果是否可靠,除了与实验技术有关外,很大程度上取决于外推方法。目前应用较为广泛的方法有:等温线外推法,时间-温度参数法(Larson-Miller参数法)和最少约束法。Based on safety and economic considerations, the evaluation of high temperature creep life has always been an important topic in the research and development of heat-resistant steel. Metal materials operating under actual conditions are often subjected to very small forces and low temperatures. Using such conditions for experiments, although the service life under service conditions can be directly obtained, it will consume a lot of time, sometimes several years. , even ten years. In order to shorten the time, the experimental stress or temperature must be increased, that is, the accelerated experimental method is used, and then the remaining life under the service conditions is determined by extrapolation. The reliability of the results obtained depends largely on the method of extrapolation, in addition to being related to the experimental technique. At present, the widely used methods are: isotherm extrapolation method, time-temperature parameter method (Larson-Miller parameter method) and least constraint method.
(1)等温线法外推持久强度(1) Extrapolation of durable strength by isotherm method
这种方法是指在同一实验温度下,用较高的不同应力进行短期试验的数据,建立应力和断裂时间的关系,来外推在该试验温度下长期的持久强度值。对大量实验数据进行分析发现,在某一恒定温度下对材料进行持久强度试验时,试样的断裂时间与应力之间存在一定的关系。广泛应用的有下列两种经验关系式:This method refers to the data of short-term tests with higher different stresses at the same experimental temperature, to establish the relationship between stress and fracture time, and to extrapolate the long-term durable strength value at the test temperature. The analysis of a large number of experimental data shows that there is a certain relationship between the fracture time of the specimen and the stress when the material is subjected to a permanent strength test at a constant temperature. The following two empirical relations are widely used:
τ=Aσ-B τ=Aσ- B
τ=Ce-Dσ τ=Ce -Dσ
上式表明断裂时间τ的对数值与应力σ的对数值之间呈线性关系或断裂时间τ的对数值与应力σ之间呈线性关系。两者中以前者(双对数坐标关系)应用较普遍。但必须指出,持久强度直线外推法,无论是用双对数坐标关系或半对数坐标关系,都是近似的。在常用的双对数坐标中,试验点并不真正符合线性关系,实际上是一条具有二次转折的曲线,只是曲线的某些区域比较接近于直线,才近似地用线性方法处理。对于不同材料和不同温度,转折的位置和形状是各不相同的。在高温下的长期试验表明:具有较高组织稳定性的钢,转折不明显,或在更长时间的试验以后才出现。对于某些组织较不稳定的钢,转折就非常明显,因此直线外推的方法比较粗略。但由于等温线外推法简单易行,在一定条件下,尚能获得比较接近实际的外推值,因而仍得到较广泛的应用。但应限制其外推时间不得超过试验时间的10倍,以保证外推值的相对准确性。The above formula shows that there is a linear relationship between the log value of fracture time τ and the log value of stress σ or the log value of fracture time τ and stress σ. There is a linear relationship. Of the two, the former (double logarithmic coordinate relationship) is more commonly used. It must be pointed out, however, that the linear extrapolation of persistent strength, whether using a double logarithmic or semi-logarithmic coordinate relationship, is approximate. In the commonly used double logarithmic coordinates, the test point does not really conform to the linear relationship, but is actually a curve with a quadratic inflection, only some areas of the curve are closer to a straight line, so the approximate linear method is used. For different materials and different temperatures, the position and shape of the inflection are different. Long-term tests at high temperatures have shown that in steels with higher structural stability, the transition is not obvious, or only appears after a longer period of time. For some steels with less stable structures, the turning point is very obvious, so the method of straight line extrapolation is rough. However, because the isotherm extrapolation method is simple and easy to implement, under certain conditions, it can still obtain the extrapolated value that is relatively close to the actual value, so it is still widely used. However, the extrapolation time should be limited to no more than 10 times the test time to ensure the relative accuracy of the extrapolated value.
(2)时间-温度参数法(2) Time-temperature parameter method
这种方法是五十年代发展起来的一种外推持久强度的方法,它指出温度和时间的相互关系,可找到某一参数P的数学表达式来表示。它是这一过程联系温度和时间的函数,参数P本身又是应力的函数,即只要金属材料所承受的应力σ不变,对于温度T的时间τ的各种组合,参数P始终保持不变,即P=P(σ)=II。参数式可以写成如下的一般形式:This method is a method of extrapolating persistent strength developed in the 1950s. It points out the relationship between temperature and time, and can find a mathematical expression for a parameter P to represent it. It is a function of the process linking temperature and time, and the parameter P itself is a function of stress, that is, as long as the stress σ of the metal material remains unchanged, for various combinations of temperature T and time τ, the parameter P always remains unchanged. , that is, P=P(σ)=II. The parametric expression can be written in the following general form:
P=P(σ)=f(T,τ)P=P(σ)=f(T, τ)
具体的参数关系式很多,L-M参数法是一种应用最广泛的外推法,它是1952年由Larson-Miller提出的,基本思想认为温度T(K)与断裂时间有补偿关系,即对一定的断裂应力,温度与时间是等效的于也就是说,对于一定断裂应力,只对应一个P。这个关系可以用L-M参数PL-M来表示。利用加速实验条件下的蠕变断裂数据进行应力外推,获得使用条件下的PL-M,然后计算出断裂时间。There are many specific parameter relations. The LM parameter method is the most widely used extrapolation method. It was proposed by Larson-Miller in 1952. The basic idea is that the temperature T(K) has a compensation relationship with the fracture time, that is, for a certain The fracture stress of , temperature and time are equivalent, that is to say, for a certain fracture stress, there is only one P. This relationship can be represented by the LM parameter P LM . Stress extrapolation was performed using creep rupture data under accelerated experimental conditions to obtain P LM under service conditions, and the rupture time was then calculated.
lgσ=f(PL-M)=f[10-3T(C+lgτ)]lgσ=f(PL-M)=f[10 -3 T(C+lgτ)]
这种外推法主要优点是使用方便、适用范围广、比较准确。不足之处在于:必须对构件进行破坏性实验,耗时费力;当构件出现明显的空洞及微裂纹之后,很难测得准确的实验数据;受化学成分、显微组织及运行中工况条件不均匀性的影响,实验数据分散度较大;对一种新材料需要做大量实验确定C值,且C值与应力有关。The main advantages of this extrapolation method are that it is easy to use, has a wide range of applications and is relatively accurate. The shortcomings are: destructive experiments must be carried out on the components, which is time-consuming and labor-intensive; when the components have obvious voids and microcracks, it is difficult to measure accurate experimental data; it is affected by chemical composition, microstructure and operating conditions. Due to the influence of inhomogeneity, the dispersion of experimental data is large; a large number of experiments are needed to determine the C value for a new material, and the C value is related to stress.
发明内容SUMMARY OF THE INVENTION
本发明的发明目的在于提供一种基于室温布氏硬度预测超临界机组T/P92耐热钢剩余持久寿命评估方法,通过简便捷、无损的硬度测试即可快速、准确的预测当前材料在特定蒸汽参数下的剩余持久寿命,可直接免去因停机或管道切割等带来的经济损失,因其方便快捷的特点可以及时的评估材料剩余寿命可有效预防因材料老化失效导致的事故发生。The purpose of the invention is to provide a method for predicting the remaining durable life of T/P92 heat-resistant steel of a supercritical unit based on Brinell hardness at room temperature, which can quickly and accurately predict the current material in a specific steam through a simple, convenient and non-destructive hardness test. The remaining durable life under the parameters can directly avoid the economic loss caused by downtime or pipe cutting, etc. Because of its convenient and fast characteristics, it can evaluate the remaining life of the material in time and effectively prevent the accident caused by the aging and failure of the material.
为实现本发明目的,本发明采用的技术方案如下:For realizing the purpose of the present invention, the technical scheme adopted in the present invention is as follows:
一种基于室温布氏硬度预测超临界机组T/P92耐热钢剩余持久寿命评估方法,具体包括如下步骤:A method for evaluating the remaining durable life of T/P92 heat-resistant steel for a supercritical unit based on Brinell hardness at room temperature, which specifically includes the following steps:
(1)热处理获得不同老化损伤的试件(1) Heat treatment to obtain specimens with different aging damage
对未服役过得T/P92耐热钢,实际工作的温度和时间,采用等效加速时效老化热处理后获得不同老化损伤级别的工件,将材料冷却到室温,取一部分制成若干个硬度测试试件;For the T/P92 heat-resistant steel that has not been in service, the actual working temperature and time are used to obtain workpieces with different levels of aging damage after equivalent accelerated aging aging heat treatment, and the material is cooled to room temperature. piece;
(2)硬度测定(2) Hardness determination
采用标准硬度仪测量材料在不同老化损伤下的硬度,对硬度测试试件按照国标GB/T 231.4-2009在实验室进行硬度测试,每组试件3~5个,每一种老化状态下试验至少3次,取平均值;A standard hardness tester is used to measure the hardness of the material under different aging damages, and the hardness test specimens are tested in the laboratory according to the national standard GB/T 231.4-2009. There are 3 to 5 specimens in each group, and each aging state is tested. At least 3 times, take the average value;
(3)高温抗拉强度测定(3) Determination of high temperature tensile strength
选取特征布氏硬度值试样5组进行材料在不同老化损伤下的高温抗拉强度测试,温度包括773K、823K、873K、923K,并建立对应数学关系模型,其关系式如下:Five groups of samples with characteristic Brinell hardness values were selected to test the high temperature tensile strength of the material under different aging damages. The temperatures included 773K, 823K, 873K, and 923K, and the corresponding mathematical relationship model was established.
σR=1.58HB+547.80-0.61T (1)σ R = 1.58HB+547.80-0.61T (1)
式中,σR是材料在某温度:773K≤T≤923K时T/P92钢的抗拉强度,HB是材料任一组织状态下的室温布氏硬度,T是应用温度;In the formula, σ R is the tensile strength of T/P92 steel when the material is at a certain temperature: 773K≤T≤923K, HB is the room temperature Brinell hardness of the material in any structure state, and T is the application temperature;
(4)持久强度实验(4) Enduring strength test
利用上述5组特征硬度值不同老化损伤状态试样进行高温持久实验并获得断裂时间参数,高温包括550℃、600℃、650℃,每组在3种不同实验温度至少进行2个不同应力条件下的持久实验;Using the above 5 groups of samples with different aging and damage states to carry out high temperature endurance experiments and obtain fracture time parameters. enduring experimentation;
(5)构建等温线外推法数学模型(5) Constructing mathematical model of isotherm extrapolation
等温线外推公式:Isotherm extrapolation formula:
tr=Aσ-B (2)t r =Aσ -B (2)
式中,A是与材料组织状态相关的参数,也称之为材料的“抗力”,即抵抗材料变形的能力参数,B是与温度相关的参数;In the formula, A is a parameter related to the tissue state of the material, also known as the "resistance" of the material, that is, the ability parameter to resist deformation of the material, and B is a parameter related to temperature;
对式(2)取对数得:Taking the logarithm of equation (2), we get:
lgtr=lgA-Blgσ (3)lgt r =lgA-Blgσ(3)
由于材料加速老化组织状态差异明显,由此A是随老化程度改变的参量;这就是说对于在同一老化参数和同一温度下利用多组应力及其对应持久断裂时间即求出在当前条件下参数A和B;Due to the obvious difference in the microstructure state of the accelerated aging of the material, A is a parameter that changes with the degree of aging; that is to say, for the use of multiple sets of stresses and their corresponding permanent fracture times under the same aging parameters and the same temperature, the parameters under the current conditions can be obtained. A and B;
(6)建立材料高温抗拉强度与参数A,持久实验温度与参数B对应数学关系,得出如下关系式:(6) Establish the corresponding mathematical relationship between the high temperature tensile strength of the material and the parameter A, the long-term experimental temperature and the parameter B, and obtain the following relationship:
A=2.7*106σR 9.03+16.71 (4)A=2.7*10 6 σ R 9.03 +16.71 (4)
B=0.1T-75.68 (5)B=0.1T-75.68 (5)
(7)拟合硬度-剩余寿命等参数的函数式(7) Fitting the functional formula of parameters such as hardness-remaining life
结合式(1)、(2)、(4)、(5)即得在T/P92钢中任意温度和应力条件下室温布氏硬度预测和当前材料剩余寿命的数学关系解析式:Combining formulas (1), (2), (4), and (5), the analytical formula of the mathematical relationship between the prediction of Brinell hardness at room temperature and the remaining life of the current material under any temperature and stress conditions in T/P92 steel can be obtained:
tr=[2.7*106(1.58HB+547.80-0.61T)9.03+16.71]σ75.68-0.1T (6)t r =[2.7*10 6 (1.58HB+547.80-0.61T) 9.03 +16.71]σ 75.68-0.1T (6)
式中,tr为当前材料剩余寿命,HB为材料室温布氏硬度,T为预测寿命所用温度,σ为预测寿命所用应力。In the formula, t r is the remaining life of the current material, HB is the Brinell hardness of the material at room temperature, T is the temperature used to predict the life, and σ is the stress used to predict the life.
所述的评估方法,该利用室温硬度预测剩余寿命的实验方法仅适用于预测T/P92钢使用在773K~923K之间内的剩余持久寿命。The described evaluation method, the experimental method for predicting the remaining life by using room temperature hardness is only suitable for predicting the remaining permanent life of T/P92 steel used between 773K and 923K.
所述的评估方法,该利用室温硬度预测剩余寿命的经验公式拥有自精确功能,在适用温度范围的任意T/P92耐热钢的硬度、持久数据进一步精确该经验方程。In the evaluation method, the empirical formula for predicting the remaining life by using room temperature hardness has a self-accurate function, and the hardness and durability data of any T/P92 heat-resistant steel in the applicable temperature range are further accurate to the empirical formula.
本发明的设计思想是:The design idea of the present invention is:
本发明通过以材料高温抗拉强度为桥梁,对持久断裂寿命和不同老化状态下室温布氏硬度HB建立对应关系,从而建立P92钢在给定温度和应力条件下室温布氏硬度与持久断裂时间之间关系的数学解析式。The invention establishes a corresponding relationship between the permanent fracture life and the room temperature Brinell hardness HB under different aging states by using the high temperature tensile strength of the material as a bridge, so as to establish the room temperature Brinell hardness and the permanent fracture time of P92 steel under given temperature and stress conditions. Mathematical analysis of the relationship between.
本发明的优点及有益效果是:The advantages and beneficial effects of the present invention are:
本发明通过简单便捷、无损的硬度测试即可快速、准确的预测当前材料在特定蒸汽参数下的剩余持久寿命,可直接免去因停机或管道切割等带来的经济损失,因其方便快捷的特点可以及时的评估T/P92耐热钢的剩余寿命可有效预防因材料老化失效导致的事故发生。The invention can quickly and accurately predict the remaining lasting life of the current material under specific steam parameters through a simple, convenient and non-destructive hardness test, and can directly avoid economic losses caused by downtime or pipe cutting. Features The remaining life of T/P92 heat-resistant steel can be evaluated in a timely manner, which can effectively prevent accidents caused by material aging and failure.
附图说明Description of drawings
图1为P92耐热钢在不同时效时间下室温布氏硬度变化图。图中,横坐标agedtime为老化时间(h);纵坐标为布氏硬度HB。Figure 1 shows the change of Brinell hardness at room temperature of P92 heat-resistant steel under different aging times. In the figure, the abscissa agedtime is the aging time (h); the ordinate is the Brinell hardness HB.
图2为P92耐热钢在特征硬度值时不同时效时间下高温抗拉强度图。图中,横坐标aged time为老化时间(h);纵坐标Tensile Strength为抗拉强度(MPa)。Figure 2 shows the high temperature tensile strength diagram of P92 heat-resistant steel under different aging times at the characteristic hardness value. In the figure, the abscissa aged time is the aging time (h); the ordinate Tensile Strength is the tensile strength (MPa).
图3为高温抗拉强度与室温硬度对应关系图。图中,横坐标为布氏硬度HB;纵坐标σR为抗拉强度(MPa)。Figure 3 is a graph showing the corresponding relationship between high temperature tensile strength and room temperature hardness. In the figure, the abscissa is the Brinell hardness HB; the ordinate σ R is the tensile strength (MPa).
图4为lgσ-lgtr双对数坐标图。图中,横坐标lgσ代表预测寿命所用应力的对数;纵坐标参数lgtr代表当前材料剩余寿命的对数。Figure 4 is a double logarithmic plot of lgσ-lgt r . In the figure, the abscissa lgσ represents the logarithm of the stress used to predict the life; the ordinate parameter lgt r represents the logarithm of the remaining life of the current material.
图5为高温抗拉强度与参数A对应关系图。图中,横坐标σR为抗拉强度(MPa)纵坐标A代表与材料组织状态相关的参数。Figure 5 is a graph showing the corresponding relationship between high temperature tensile strength and parameter A. In the figure, the abscissa σ R is the tensile strength (MPa) and the ordinate A represents the parameters related to the microstructure state of the material.
图6为持久实验温度与参数B对应关系图。图中,横坐标T为温度(K);纵坐标参数B代表与温度相关的参数。Figure 6 is a graph showing the corresponding relationship between the persistent experimental temperature and parameter B. In the figure, the abscissa T is the temperature (K); the ordinate parameter B represents the parameters related to temperature.
具体实施方式Detailed ways
为了能够更清楚地理解本发明的技术内容,特以此材料为例作进一步说明。应理解,一下实施例仅用于说明的目的,而并非用于限定本发明的范围。In order to understand the technical content of the present invention more clearly, this material is taken as an example for further description. It should be understood that the following embodiments are for illustrative purposes only, and are not intended to limit the scope of the present invention.
实施例Example
利用某电厂未服役P92耐热钢实现本发明所述的基于室温布氏硬度预测超临界机组T/P92耐热钢剩余持久寿命评估方法,具体的实现方式如下:Utilizing P92 heat-resistant steel not in service in a power plant to realize the method for evaluating the remaining lasting life of T/P92 heat-resistant steel of a supercritical unit based on room temperature Brinell hardness prediction according to the present invention, the specific implementation method is as follows:
(1)热处理获得不同老化损伤的试件(1) Heat treatment to obtain specimens with different aging damage
对未服役过得T/P92耐热钢,实际工作的温度和时间,采用等效加速时效老化热处理后获得不同老化损伤级别的工件,将材料冷却到室温,取一部分制成若干个硬度测试试件;For the T/P92 heat-resistant steel that has not been in service, the actual working temperature and time are used to obtain workpieces with different levels of aging damage after equivalent accelerated aging aging heat treatment, and the material is cooled to room temperature. piece;
本实施例中,等效加速时效老化热处理是指:选用AC1点以下30~40℃的温度下进行时效,时间为5~1000h;老化完成再在650℃下进行二次时效,以保证快速析出Laves相,最终实现等效于实际工况不同时期下的老化组织。In this embodiment, the equivalent accelerated aging aging heat treatment refers to: aging at a temperature of 30-40°C below the AC1 point for 5-1000h; after the aging is completed, perform secondary aging at 650°C to ensure rapid precipitation Laves phase, the final realization is equivalent to the aging structure under different periods of actual working conditions.
(2)硬度测定(2) Hardness determination
采用标准硬度仪测量材料在不同老化损伤下的硬度,对硬度测试试件按照国标GB/T 231.4-2009在实验室进行硬度测试,每组试件3~5个,每一种老化状态下试验至少3次,取平均值;A standard hardness tester is used to measure the hardness of the material under different aging damages, and the hardness test specimens are tested in the laboratory according to the national standard GB/T 231.4-2009. There are 3 to 5 specimens in each group, and each aging state is tested. At least 3 times, take the average value;
(3)高温抗拉强度测定(3) Determination of high temperature tensile strength
选取特征布氏硬度值试样5组进行材料在不同老化损伤下的高温(包括773K、823K、873K、923K)抗拉强度测试,并建立对应数学关系模型,其关系式如下:Select 5 groups of samples with characteristic Brinell hardness values to test the tensile strength of materials at high temperature (including 773K, 823K, 873K, 923K) under different aging damage, and establish the corresponding mathematical relationship model, the relationship is as follows:
σR=1.58HB+547.80-0.61T (1)σ R = 1.58HB+547.80-0.61T (1)
式中,σR是材料在某温度T(773K≤T≤923K)时T/P92钢的抗拉强度,HB是材料任一组织状态下的室温布氏硬度,T是应用温度。In the formula, σ R is the tensile strength of T/P92 steel when the material is at a certain temperature T (773K≤T≤923K), HB is the room temperature Brinell hardness of the material in any structure state, and T is the application temperature.
(4)持久强度实验(4) Enduring strength test
利用上述5组特征硬度值不同老化损伤状态试样进行高温(包括550℃、600℃、650℃)持久实验并获得断裂时间参数,每组在3种不同实验温度需至少进行2个不同应力条件下的持久实验,结果如表1所示。Use the above 5 groups of samples with different aging and damage states to carry out high temperature (including 550 ° C, 600 ° C, 650 ° C) endurance experiments and obtain fracture time parameters. Each group needs at least 2 different stress conditions at 3 different experimental temperatures. The results of the persistent experiments are shown in Table 1.
表1 P92不同老化级别持久性能Table 1 Persistence performance of P92 at different aging levels
(5)构建等温线外推法数学模型(5) Constructing mathematical model of isotherm extrapolation
常用的等温线外推公式:Commonly used isotherm extrapolation formula:
tr=Aσ-B (2)t r =Aσ -B (2)
式中,A是与材料组织状态相关的参数,也可称之为材料的“抗力”,即抵抗材料变形的能力参数,B是与温度相关的参数。In the formula, A is a parameter related to the organizational state of the material, which can also be called the "resistance" of the material, that is, the ability parameter to resist deformation of the material, and B is a parameter related to temperature.
对式(2)取对数得:Taking the logarithm of equation (2), we get:
lgtr=lgA-Blgσ (3)lgt r =lgA-Blgσ(3)
由于材料加速老化组织状态差异明显,由此A是随老化程度改变的参量。这就是说对于在同一老化参数和同一温度下可以利用多组应力及其对应持久断裂时间即可求出在当前条件下参数A和B,结果如表2所示。Due to the obvious difference in the tissue state of accelerated aging of materials, A is a parameter that changes with the degree of aging. That is to say, for the same aging parameters and the same temperature, the parameters A and B under the current conditions can be obtained by using multiple sets of stresses and their corresponding permanent fracture times. The results are shown in Table 2.
表2 P92中材料参数A和温度参数BTable 2 Material parameter A and temperature parameter B in P92
(6)建立材料高温抗拉强度与参数A,持久实验温度与参数B对应数学关系,得出如下关系式:(6) Establish the corresponding mathematical relationship between the high temperature tensile strength of the material and the parameter A, the long-term experimental temperature and the parameter B, and obtain the following relationship:
A=2.7*106σR 9.03+16.71 (4)A=2.7*10 6 σ R 9.03 +16.71 (4)
B=0.1T-75.68 (5)B=0.1T-75.68 (5)
(7)拟合硬度-剩余寿命等参数的函数式(7) Fitting the functional formula of parameters such as hardness-remaining life
结合式(1)、(2)、(4)、(5)即可得在T/P92钢中任意温度和应力条件下室温布氏硬度预测和当前材料剩余寿命的数学关系解析式:Combining formulas (1), (2), (4) and (5), the analytical formula of the mathematical relationship between the prediction of Brinell hardness at room temperature and the remaining life of the current material under any temperature and stress conditions in T/P92 steel can be obtained:
tr=[2.7*106(1.58HB+547.80-0.61T)9.03+16.71]σ75.68-0.1T (6)t r =[2.7*10 6 (1.58HB+547.80-0.61T) 9.03 +16.71]σ 75.68-0.1T (6)
式中,tr为当前材料剩余寿命,HB为材料室温布氏硬度,T为预测寿命所用温度,σ为预测寿命所用应力。In the formula, t r is the remaining life of the current material, HB is the Brinell hardness of the material at room temperature, T is the temperature used to predict the life, and σ is the stress used to predict the life.
实验选取P92耐热钢硬度为HB148的样品进行600℃/140MPa的持久实验,其持久断裂时间为1397.42h;利用公式(6)计算预测相应持久条件下该试样的剩余持久寿命为1357.59h,误差为2.9%,这一结果很好的证明了本发明的预测方法的准确性。In the experiment, a sample of P92 heat-resistant steel with a hardness of HB148 was selected for the endurance test at 600°C/140MPa, and its permanent fracture time was 1397.42h; using formula (6) to calculate and predict the remaining endurance life of the sample under the corresponding endurance conditions was 1357.59h, The error is 2.9%, which well proves the accuracy of the prediction method of the present invention.
如图1所示,从P92耐热钢在不同时效时间下室温布氏硬度变化图可以看出,布氏硬度HB随着时效时间的延长不断降低,且初始降低的比较快,而后逐渐趋于平缓,这一结果与材料组织老化演变过程能够很好的对应,这也就说明用硬度来表征材料当前的组织特征是合适的。此外,利用不同等效加速老化温度试验验证了该材料在800℃条件下热处理时间更短、效果更佳。As shown in Figure 1, it can be seen from the Brinell hardness change diagram of P92 heat-resistant steel at room temperature under different aging times that the Brinell hardness HB decreases continuously with the aging time, and the initial decrease is relatively fast, and then gradually tends to This result can correspond well with the aging evolution process of the material structure, which means that it is suitable to use the hardness to characterize the current structure characteristics of the material. In addition, using different equivalent accelerated aging temperature tests, it was verified that the heat treatment time of the material was shorter and the effect was better at 800 °C.
如图2所示,从P92耐热钢在特征硬度值时不同时效时间下高温抗拉强度图可以看出,随着时效时间延长,材料的高温抗拉强度也发生了一定程度的降低且降低趋势与硬度变化基本保持一致。As shown in Figure 2, it can be seen from the high temperature tensile strength diagram of P92 heat-resistant steel under different aging times at the characteristic hardness value, as the aging time prolongs, the high temperature tensile strength of the material also decreases to a certain extent and decreases. The trend is basically consistent with the hardness change.
如图3所示,从高温抗拉强度与室温硬度对应关系图可以看出,不同老化程度的硬度与高温抗拉强度得到了很好的对应关系,这就可以建立不同老化条件下硬度与高温抗拉强度的数学关系,即利用硬度即可表征材料的高温抗拉强度。As shown in Figure 3, it can be seen from the corresponding relationship between high temperature tensile strength and room temperature hardness that the hardness of different aging degrees and high temperature tensile strength have a good corresponding relationship, which can establish the hardness and high temperature under different aging conditions. The mathematical relationship of tensile strength, that is, the high temperature tensile strength of a material can be characterized by hardness.
如图4所示,从lgσ-lgtr双对数坐标图可以看出,在同一老化参数和同一温度下可以利用多组应力及其对应持久断裂时间即可求出在当前条件下参数A和B,其中A为关系曲线的截距,B则为关系曲线的斜率的绝对值。As shown in Figure 4, it can be seen from the lgσ-lgt r double logarithmic coordinate diagram that under the same aging parameters and the same temperature, the parameters A and B, where A is the intercept of the relationship and B is the absolute value of the slope of the relationship.
如图5所示,从高温抗拉强度与参数A对应关系图可以看出,材料的高温抗拉强度与参数A建立了很好的对应关系,由于材料的高温抗拉强度可以表征材料不同老化特征下的组织状态,这也就是说参数A是等温线外推公式中材料的组织状态参数且可以用高温抗拉强度表征。As shown in Figure 5, it can be seen from the corresponding relationship between the high-temperature tensile strength and parameter A that the high-temperature tensile strength of the material has a good corresponding relationship with the parameter A. Because the high-temperature tensile strength of the material can characterize the different aging of the material The microstructure state under the characteristic, which means that the parameter A is the microstructure state parameter of the material in the isotherm extrapolation formula and can be characterized by the high temperature tensile strength.
如图6所示,从持久实验温度与参数B对应关系图可以看出,参数B只与温度相关而不与材料的老化状态相关,该参数在不同老化状态也趋于某一特定值。As shown in Figure 6, it can be seen from the graph of the corresponding relationship between the persistent experimental temperature and the parameter B that the parameter B is only related to the temperature and not to the aging state of the material, and this parameter tends to a certain value in different aging states.
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