Method for judging influence of residual boron on hardenability in carburized steel

Abstract

The application relates to a method for judging the influence of residual boron in carburized steel on hardenability, which comprises the following steps: after a sample blank is subjected to structure homogenization treatment, the sample blank is processed into two end-quenching samples; the two end-quenching samples are subjected to end-quenching treatment under first and second conditions respectively; a measuring surface is ground on the end-quenching samples, and a plurality of measuring points distributed along the axial direction of the end-quenching samples are selected on the measuring surface; the hardness values of the measuring points are measured; the hardness difference of the measuring points with equal distances from the quenched end on the two end-quenching samples is calculated; and the influence of residual boron in carburized steel on hardenability is obtained based on the hardness difference. The two end-quenching samples are subjected to end-quenching treatment under two different end-quenching treatment conditions, and then the hardness values at different positions are measured, and whether the residual boron in the carburized steel has an influence on the hardenability is judged by obtaining the hardness difference of the measuring points with equal distances from the quenched end on the two end-quenching samples. The method provided by the application is simple and reliable in detection means without measuring the boron content.

Description

Technical Field

[0001] This application relates to the field of carburizing steel smelting technology, and in particular to a method for judging the influence of residual boron on hardenability in carburizing steel. Background Technology

[0002] Boron in steel exists in both solid solution and non-solid solution forms (such as boron-containing phases and boron oxynitrogen compounds). Solid solution boron often affects hardenability through non-equilibrium segregation at grain boundaries. This non-equilibrium segregation of boron reduces grain boundary energy, prevents carbon atoms from diffusing at grain boundaries, and increases volume stress at the nodal sites. Therefore, more phase transformation free energy is required, which affects the nucleation of new phases at austenite grain boundaries, prolongs the austenite decomposition incubation period, and achieves the goal of improving the hardenability of the material.

[0003] The non-equilibrium segregation of dissolved boron at grain boundaries is influenced by factors such as the content of dissolved boron, the segregation rate, and the material composition. In steel, dissolved boron precipitates along grain boundaries, forming a non-dissolved boron-containing phase, which is related to the precipitation temperature and the content of dissolved boron.

[0004] To quickly determine whether residual boron in a material affects its hardenability, precise detection of the residual boron content in the steel is generally used for confirmation. For example, with the development of direct-reading spectroscopy and ICP-AES (inductively coupled plasma atomic emission spectrometry, a spectral analysis method using inductively coupled plasma as the excitation source), various direct-reading spectroscopy and ICP-AES methods for detecting boron content in steel have been developed both domestically and internationally. These methods have a detection limit of 0.00030% and a sample spike recovery rate in the range of 99.0% to 103.1%, demonstrating very high precision. Since boron exists in steel in both solid-solid and non-solid-solid forms, and the main factor affecting hardenability is the segregation of solid-solid boron at grain boundaries, the quantitative determination is affected by the content of non-solid-solid boron. Therefore, only the total residual boron content in the steel can be determined, and it is impossible to determine whether the residual boron element affects hardenability.

[0005] Existing technologies often have the following problems:

[0006] ① The total boron content in steel is detected by precise means, but it cannot reflect the non-equilibrium segregation characteristics of residual boron at the grain boundaries, and therefore it is impossible to determine whether it affects hardenability.

[0007] ② Conventional hardenability tests can only reflect the hardenability characteristics of materials and cannot confirm whether the hardenability characteristics are due to the influence of residual B. Summary of the Invention

[0008] This application provides a method for determining the effect of residual boron on hardenability in carburized steel, thereby solving the problem in related technologies that cannot reflect whether residual boron affects hardenability.

[0009] This application provides a method for determining the effect of residual boron on hardenability in carburized steel, which includes the following steps:

[0010] After the sample blank is homogenized, it is processed into two end-quenched samples.

[0011] The two end-quenched samples were subjected to end-quenching treatment under the first and second conditions, respectively.

[0012] The end-quenched sample is ground to create a measuring surface parallel to the axis of the end-quenched sample, and several measuring points distributed along the axis of the end-quenched sample are selected on the measuring surface.

[0013] Measure the hardness value at the measurement point on the end-quenched sample;

[0014] Calculate the hardness difference between two end-quenched specimens at measurement points equidistant from the quenching end;

[0015] Based on the various hardness differences, the effect of residual boron in carburized steel on hardenability was obtained.

[0016] This method involves end-quenching two samples under two different end-quenching conditions, and then measuring the hardness values ​​at different locations. By obtaining the hardness difference at measurement points equidistant from the quenched ends on the two end-quenched samples, it is possible to determine whether residual boron in the carburized steel affects hardenability. The method provided in this application does not require measuring boron content, and the detection method is simple and reliable.

[0017] In some embodiments, the effect of residual boron in carburized steel on hardenability is obtained based on various hardness differences, specifically including the following steps:

[0018] The hardness differences are sorted in ascending order of the distance from the measurement point corresponding to the hardness difference to the quenching end.

[0019] Starting from the hardness difference of the preset serial number, compare the hardness difference of a preset number of consecutive numbers with the hardness threshold to determine whether the hardness difference of the preset number of consecutive numbers of numbers is greater than or equal to the hardness threshold.

[0020] If the hardness difference of a consecutive preset number is greater than or equal to the hardness threshold, the residual boron in the carburized steel has an effect on hardenability that exceeds the requirements.

[0021] Otherwise, residual boron in carburized steel has no effect on hardenability.

[0022] In some embodiments, the preset sequence number is 3.

[0023] In some embodiments, the preset quantity is 3.

[0024] In some embodiments, when the hardness is Rockwell hardness, the hardness threshold is 3 HRC;

[0025] When the hardness is Vickers hardness, the hardness threshold is 30HV.

[0026] In some embodiments, the end quenching treatment under the first condition includes: holding at 925–935°C for 25–35 minutes;

[0027] The end-quenching treatment under the second condition includes: holding at 925–935℃ for 280–320 min.

[0028] In some embodiments, the tissue homogenization process includes holding at 940–960°C for 25–35 minutes.

[0029] In some embodiments, the grinding depth of the measuring surface is 0.4 to 0.5 mm from the surface of the end-quenched sample.

[0030] In some embodiments, the end-quenched sample has two measuring surfaces, and the two measuring surfaces are parallel to each other;

[0031] Measuring the hardness value at the measurement point on the end-quenched sample specifically includes the following steps:

[0032] Measure the hardness values ​​of the measurement points on the two measurement surfaces of the end-quenched sample, calculate the average value of the hardness values ​​of the measurement points that are equidistant from the quenched end, and use the average value as the hardness value of the measurement point.

[0033] In some embodiments, before subjecting the end-quenched sample to end-quenching under the second condition, the determination method further includes the following steps:

[0034] The end-quenched sample is installed in the hardenability sample heating tank, and cast iron is placed at the bottom of the hardenability sample heating tank. The cast iron is ductile iron plate or gray cast iron sheet.

[0035] The end-quenched sample is separated from the oil-impregnated paper used for casting iron.

[0036] The beneficial effects of the technical solution provided in this application include:

[0037] This application provides a method for determining the influence of residual boron on hardenability in carburized steel. Two end-quenched samples are subjected to end-quenching under two different conditions, and the hardness values ​​at different locations are measured. By obtaining the hardness difference at measurement points equidistant from the quenched ends on the two end-quenched samples, it can be determined whether residual boron in the carburized steel affects hardenability. The method provided in this application does not require measuring boron content, and the detection method is simple and reliable. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 A flowchart illustrating the method for determining the effect of residual boron on hardenability in carburized steel, as provided in this application embodiment;

[0040] Figure 2 This is a schematic diagram of an end-quenched sample provided in an embodiment of this application;

[0041] Figure 3 A schematic diagram of an end-quenched specimen installed in a hardenability test specimen heating tank according to an embodiment of this application;

[0042] Figure 4 A schematic diagram of the measurement surface provided in an embodiment of this application;

[0043] Figure 5 Hardness curves of two end-extraction samples provided for embodiments of this application (residual boron affects hardenability);

[0044] Figure 6 Hardness curves of two end-extraction samples provided for embodiments of this application (residual boron has no effect on hardenability);

[0045] Figure 7 A flowchart illustrating the effect of residual boron on hardenability in carburized steel based on various hardness differences is provided in this application embodiment.

[0046] Figure 8 Hardness curves of samples A and C in Example 1 of this application;

[0047] Figure 9 The hardenability hardness curves of samples A and B in Example 1 of this application;

[0048] Figure 10 The hardenability curves of samples D and E in Example 2 of this application are shown.

[0049] In the figure: 1. End-quenched sample; 2. Measuring surface; 3. Quenched end; 4. Heating tank for hardenability sample; 5. Cast iron. Detailed Implementation

[0050] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0051] Based on the non-equilibrium segregation mechanism of boron (B) at grain boundaries during cooling, under certain isothermal treatment conditions, non-equilibrium boron segregation, which is more complex than equilibrium segregation, often occurs at grain boundaries. As the holding time increases, the boron segregation at grain boundaries gradually disappears, partially disappears, or does not disappear. These differences mainly depend on the occurrence and development of non-equilibrium segregation and the precipitation process of boron-containing phases during isothermal treatment. Due to the numerous influencing factors, simply detecting the dissolved boron content in the material cannot reflect whether residual boron affects the hardenability of the steel.

[0052] Therefore, this application provides a method for determining the effect of residual boron on hardenability in carburized steel, which can solve the problem in related technologies that cannot reflect whether residual boron has an effect on hardenability.

[0053] See Figure 1 As shown in the embodiments of this application, a method for determining the influence of residual boron on hardenability in carburized steel is provided, which includes the following steps:

[0054] 101: After the sample blank is homogenized, it is processed into two end-quenched samples 1.

[0055] In step 101, the bar can be cut into a sample blank or the bar can be forged into a sample blank.

[0056] The dimensions of the sample blank can be determined according to the test requirements. For example, in this embodiment, the dimensions of the sample blank are: φ30mm, length ≥120mm.

[0057] The homogenization treatment includes holding the sample blank at 940–960°C for 25–35 minutes. Under these conditions, the sample blank can be fully austenitized, thereby achieving microstructure homogenization.

[0058] After heating the sample blank to 940–960℃ and holding it at that temperature for 25–35 minutes, the normalizing treatment can homogenize the microstructure of the sample blank and eliminate interference from uneven microstructure or other abnormal microstructures.

[0059] The sample blank was then machined into two standard end-quenched sample 1s, as follows: Figure 2 and Figure 3 As shown.

[0060] 102: The two end-quenched samples 1 are subjected to end-quenching treatment under the first and second conditions, respectively.

[0061] In step 102, the end-quenching conditions of the two end-quenched samples 1 are different.

[0062] One of the end-quenched specimens 1 is heat-treated according to the requirements of the "GBT225-2006 Standard for End-Quenching Test Method (Jominy Test) of Hardenability of Steel". That is, the end-quenched specimen 1 is end-quenched under the first condition, which specifically includes: holding at 925-935℃ for 25-35 minutes.

[0063] Another end-quenched sample 1 was subjected to end-quenching treatment under the second condition. Specifically, the end-quenching treatment under the second condition included holding at 925–935°C for 280–320 min. By extending the holding time, the non-equilibrium segregation of boron elements at the grain boundaries was reduced or eliminated, and the boron elements dissolved into the steel, thereby affecting the hardenability results.

[0064] Among them, the two end-quenched samples 1 were subjected to the same temperature but different holding times during the end-quenching treatment.

[0065] It should be noted that, in order to prevent surface oxidation, decarburization, or carbonization, for the end-quenched sample 1 subjected to the second end-quenching treatment, before performing the second end-quenching treatment on the end-quenched sample 1, please refer to... Figure 3 As shown, the judgment method further includes the following steps: installing the end-quenched sample 1 into the hardenability sample heating tank 4, and placing cast iron 5 at the bottom of the hardenability sample heating tank 4, wherein the cast iron 5 is a ductile iron plate or a gray cast iron sheet; separating the end-quenched sample 1 from the cast iron 5 with oil-impregnated paper.

[0066] 103: Grind the end-quenched sample 1 to create a measuring surface 2 parallel to the axis of the end-quenched sample 1, and select several measuring points distributed along the axis of the end-quenched sample 1 on the measuring surface 2.

[0067] See Figure 4 As shown, in step 103, the end-quenched sample 1 is ground to form a measuring surface 2 that can be used to measure the hardness value. When grinding the measuring surface 2, care must be taken to prevent grinding burns from affecting the hardness test.

[0068] When grinding the measuring surface 2, the grinding depth of the measuring surface 2 can be determined according to the actual measurement needs. For example, the grinding depth of the measuring surface 2 is 0.4 to 0.5 mm from the surface of the end-quenched sample 1.

[0069] It should be noted that one end of the end-quenched sample 1 is the quenched end 3. Several measurement points selected on the measurement surface 2 are arranged in a straight line, parallel to the axis of the end-quenched sample 1, and preferably located in the middle of the measurement surface 2.

[0070] The number of measurement points on the measurement surface 2 of the end-quenched sample 1 can be determined according to actual testing needs.

[0071] The distance from each measurement point on the measurement surface 2 to the quenched end 3 of the end-quenched sample 1 can also be determined according to actual testing needs.

[0072] For example, see Figure 2 As shown, there are 12 measuring points on measuring surface 2, and their distances from the quenching end 3 are 1.5mm, 3mm, 5mm, 7mm, 9mm, 11mm, 13mm, 15mm, 20mm, 25mm, 30mm, and 35mm, respectively. These measuring points can be labeled J1.5, J3, J5, J7, J9, J11, J13, J15, J17, J20, J25, J30, and J35.

[0073] The measurement points on the measurement surface 2 of the two end-quenched specimens 1 should be selected at the same location.

[0074] For example, if the measurement points on the measurement surface 2 of one end-quenched sample 1 are J1.5, J3, J5, J7, J9, J11 and J13, then the measurement points on the measurement surface 2 of the other end-quenched sample 1 are also J1.5, J3, J5, J7, J9, J11 and J13.

[0075] For example, as another example, if the measurement points on the measurement surface 2 of one end-quenched sample 1 are 1.5mm, 3mm, 5mm, 7mm, 9mm, 11mm, 13mm, 15mm, 20mm, 25mm, 30mm and 35mm, then the measurement points on the measurement surface 2 of another end-quenched sample 1 are also 1.5mm, 3mm, 5mm, 7mm, 9mm, 11mm, 13mm, 15mm, 20mm, 25mm, 30mm and 35mm.

[0076] Furthermore, it should be noted that the deviation of the selected measurement points should not exceed a deviation threshold. This deviation threshold can be determined based on actual testing needs; for example, it can be set to 0.2 mm. Taking measurement points J1.5 and J3 as examples, the deviation of measurement point J1.5 from the quenching end 3 should not exceed 0.2 mm. In other words, the actual distance between measurement point J1.5 and the quenching end 3 can be 1.3–1.7 mm. Similarly, the deviation of measurement point J3 from the quenching end 3 should not exceed 0.2 mm. In other words, the actual distance between measurement point J3 and the quenching end 3 can be 2.8–3.2 mm.

[0077] 104: Measure the hardness value at the measuring point on the end-quenched sample 1.

[0078] Hardness values ​​at different locations can be measured using a Vickers hardness tester or a Rockwell hardness tester.

[0079] It should be noted that the number of measuring surfaces 2 can be adjusted by grinding according to actual needs. For example, to improve the accuracy of hardness value measurement, see [reference needed]. Figure 4 In the process, there are two measuring surfaces 2, and these two measuring surfaces 2 are parallel to each other. At this time, the hardness value of the measuring point on the end-quenched sample 1 is measured, which specifically includes the following steps:

[0080] The hardness values ​​of the measuring points on the two measuring surfaces 2 of the end-quenched sample 1 are measured, and the average value of the hardness values ​​of the measuring points that are equidistant from the quenched end 3 is obtained. The average value is then used as the hardness value of the measuring point.

[0081] By measuring the hardness values ​​at the measurement points on the two measurement surfaces 2 of the end-quenched sample 1 and calculating the average value, the measurement error during measurement can be avoided, thereby improving the measurement accuracy.

[0082] It should be noted that the distance from the measurement point to the quenched end 3 can be used as the abscissa, and the hardness value as the ordinate. By plotting the measurement points and hardness values ​​on the measurement surface 2 of the two end-quenched samples 1 on the same coordinate system, two hardenability hardness curves can be obtained, such as... Figure 5 and Figure 6 As shown, where, Figure 5 and Figure 6 The vertical axis is in HRC units, and the horizontal axis is in mm units.

[0083] 105: Calculate the hardness difference between the two end-quenched specimens 1 at measurement points equidistant from the quenched end 3.

[0084] For example, as an example, calculate the hardness difference between the hardness values ​​of J1.5 on one end-quenched sample 1 and J1.5 on another end-quenched sample 1; calculate the hardness difference between the hardness values ​​of J3 on one end-quenched sample 1 and J3 on another end-quenched sample 1; calculate the hardness difference between the hardness values ​​of J5 on one end-quenched sample 1 and J5 on another end-quenched sample 1; calculate the hardness difference between the hardness values ​​of J7 on one end-quenched sample 1 and J7 on another end-quenched sample 1; calculate the hardness difference between the hardness values ​​of J9 on one end-quenched sample 1 and J9 on another end-quenched sample 1; calculate the hardness difference between the hardness values ​​of J11 on one end-quenched sample 1 and J11 on another end-quenched sample 1; calculate the hardness difference between one end-quenched sample... Calculate the hardness difference between the hardness value of J13 on one end-quenched sample 1 and the hardness value of J13 on another end-quenched sample 1. Calculate the hardness difference between the hardness values ​​of J15 on one end-quenched sample 1 and the hardness values ​​of J15 on another end-quenched sample 1. Calculate the hardness difference between the hardness values ​​of J20 on one end-quenched sample 1 and the hardness values ​​of J20 on another end-quenched sample 1. Calculate the hardness difference between the hardness values ​​of J25 on one end-quenched sample 1 and the hardness values ​​of J25 on another end-quenched sample 1. Calculate the hardness difference between the hardness values ​​of J30 on one end-quenched sample 1 and the hardness values ​​of J35 on another end-quenched sample 1. Calculate the hardness difference between the hardness values ​​of J35 on one end-quenched sample 1 and the hardness values ​​of J35 on another end-quenched sample 1. And so on, to calculate the hardness difference of all the measurement points.

[0085] 106: Based on various hardness differences, the effect of residual boron in carburized steel on hardenability is obtained.

[0086] See Figure 7 As shown, in step 106, based on various hardness differences, the effect of residual boron in carburized steel on hardenability is obtained, specifically including the following steps:

[0087] 201: Sort the hardness differences in order of increasing distance from the measurement point corresponding to the hardness difference to the quenching end 3.

[0088] For example, the measurement points are sequentially numbered J1.5, J3, J5, J7, J9, J11, J13, J15, J17, J20, J25, J30 and J35.

[0089] 202: Starting from the hardness difference of the preset serial number, compare the hardness difference of the preset number of consecutive numbers with the hardness threshold, and determine whether the hardness difference of the preset number of consecutive numbers of ...

[0090] It should be noted that the above preset serial number can be determined according to actual testing needs. For example, as an example, the preset serial number is 3, that is, starting from J5.

[0091] It should be noted that the above preset quantity can be determined according to actual testing needs. For example, as an example, the preset quantity is 3, which means comparing three consecutive hardness differences with the hardness threshold.

[0092] For example, when the preset sequence number is 3 and the preset quantity is 3, it is to determine whether the hardness difference corresponding to J5, J7 and J9 is greater than or equal to the hardness threshold.

[0093] During hardenability testing, due to errors in hardness measurement, data at the same location may exceed the hardness threshold, leading to misjudgment. Therefore, judging multiple consecutive data points can avoid this. In other words, the larger the preset number, the more accurate the result.

[0094] It should be noted that the above hardness threshold can be determined according to actual testing needs. For example, when the hardness is Rockwell hardness, the hardness threshold is 3HRC; when the hardness is Vickers hardness, the hardness threshold is 30HV.

[0095] 203: See also Figure 5 As shown, if the hardness difference of a consecutive preset number is greater than or equal to the hardness threshold, the residual boron in the carburized steel has an effect on hardenability that exceeds the requirements. In other words, the residual boron in the carburized steel has a significant effect on hardenability. At this time, the carburized steel does not meet the production requirements and can be returned.

[0096] 204: Otherwise, see Figure 6 As shown, residual boron in carburized steel has no effect on hardenability.

[0097] For step 204, if the number of consecutive data points with a hardness difference greater than or equal to the hardness threshold is less than the preset number or the data points are not continuous, it indicates that the residual boron in the carburized steel has no effect on hardenability.

[0098] The residual boron in the carburized steel has no effect on hardenability. This may be because it has no effect, or it may be due to testing errors. Therefore, steps 101 to 106 can be repeated to perform another test. If the hardness difference of the preset number of consecutive tests is still not greater than or equal to the hardness threshold, then it is true that the residual boron in the carburized steel has no effect on hardenability.

[0099] Example 1

[0100] The chemical composition of a certain type of steel is:

[0101] C: 0.22%, S: 0.022%, Si: 0.29%, P: 0.014%, Mn: 0.98%, Cr: 1.20%, Ti: 0.025%, Residual B: 0.0005%, Ni: 0.11%, O content 13ppm, N content 76ppm.

[0102] Except for O and N, which are expressed in ppm, the other elements are expressed as mass percentages.

[0103] The above-mentioned steel grades were made into sample blanks and treated at 950℃ for 30 minutes to homogenize the microstructure.

[0104] Then, it was processed into three end-quenched specimens, which were designated as specimen A, specimen B, and specimen C, respectively.

[0105] Sample A was subjected to heat treatment at 930℃ for 30 minutes to achieve end quenching.

[0106] Sample B was held at 930℃ for 240 minutes to achieve end quenching.

[0107] Sample C was held at 930℃ for 300 minutes to achieve end quenching.

[0108] Subsequently, samples A, B, and C are ground to create a measurement surface 2 parallel to the axis of the end-quenched sample 1. Twelve measurement points are then selected on measurement surface 2, distributed along the axial direction of the end-quenched sample 1. These measurement points can be labeled J1.5, J3, J5, J7, J9, J11, J13, J15, J17, J20, J25, J30, and J35.

[0109] Measure the hardness values ​​at the measurement points on specimens A, B, and C.

[0110] See measurement results Figure 8 and Figure 9 As shown, where, Figure 8 and Figure 9 The vertical axis is in HRC and the horizontal axis is in mm.

[0111] exist Figure 8 In the figure, represents the hardness values ​​of samples A and C. Figure 9 The values ​​in the middle are the hardness values ​​of sample A and sample B.

[0112] As can be seen, when the same raw material is sampled and heat-treated for 300 minutes, the test results are more obvious and it is easier to determine whether the residual boron in the carburized steel affects the hardenability.

[0113] Example 2

[0114] The chemical composition of a certain type of steel is:

[0115] C: 0.21%, S: 0.025%, Si: 0.20%, P: 0.015%, Mn: 0.95%, Cr: 1.00%, Ti: 0.023%, Residual B: 0.00045%, Ni: 0.11%, O content 11ppm, N content 70ppm.

[0116] Except for O and N, which are expressed in ppm, the other elements are expressed as mass percentages.

[0117] The above-mentioned steel grades were made into sample blanks and treated at 950℃ for 30 minutes to homogenize the microstructure.

[0118] Then, it was processed into two end-quenched specimens, denoted as specimen D and specimen E, respectively.

[0119] Sample D was subjected to heat treatment at 930℃ for 30 minutes to achieve end quenching.

[0120] Sample E was held at 930℃ for 300 minutes to achieve end quenching.

[0121] Subsequently, samples D and E are ground to create a measurement surface 2 parallel to the axis of the end-quenched sample 1. Twelve measurement points are then selected on measurement surface 2, distributed along the axis of the end-quenched sample 1. These measurement points can be labeled J1.5, J3, J5, J7, J9, J11, J13, J15, J17, J20, J25, J30, and J35.

[0122] Measure the hardness values ​​at the measurement points on specimens D and E.

[0123] See measurement results Figure 10 As shown, where, Figure 10 The vertical axis is in HRC and the horizontal axis is in mm. As can be seen from the figure, the residual boron in the carburized steel does not show any effect on hardenability.

[0124] In the description of this application, it should be noted that the terms "upper," "lower," etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Unless otherwise expressly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two elements. For those skilled in the art, the specific meaning of the above terms in this application can be understood according to the specific circumstances.

[0125] It should be noted that in this application, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0126] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for determining the effect of residual boron on hardenability in carburized steel, characterized in that, It includes the following steps: After the sample blank is homogenized, it is processed into two end-quenched samples (1). The two end-quenched samples (1) were subjected to end-quenching treatment under the first and second conditions, respectively; The end-quenched sample (1) is ground to create a measuring surface (2) parallel to the axis of the end-quenched sample (1), and several measuring points distributed along the axis of the end-quenched sample (1) are selected on the measuring surface (2). Measure the hardness value at the measuring point on the end-quenched sample (1); Calculate the hardness difference between two end-quenched specimens (1) at measurement points equidistant from the quenched end (3); Based on various hardness differences, the effect of residual boron in carburized steel on hardenability was obtained; Based on various hardness differences, the effect of residual boron in carburized steel on hardenability is obtained, specifically including the following steps: The hardness differences are sorted in order of increasing distance from the measurement point corresponding to the hardness difference to the quenching end (3); Starting from the hardness difference of the preset serial number, compare the hardness difference of a preset number of consecutive numbers with the hardness threshold to determine whether the hardness difference of the preset number of consecutive numbers of numbers is greater than or equal to the hardness threshold. If the hardness difference of a consecutive preset number is greater than or equal to the hardness threshold, the residual boron in the carburized steel has an effect on hardenability that exceeds the requirements. Otherwise, residual boron in carburized steel has no effect on hardenability; The end-quenching treatment under the first condition includes: holding at 925~935℃ for 25~35 min; The end-quenching treatment under the second condition includes: holding at 925~935℃ for 280~320 minutes.

2. The method for determining the effect of residual boron on hardenability in carburized steel as described in claim 1, characterized in that: The preset serial number is 3.

3. The method for determining the effect of residual boron on hardenability in carburized steel as described in claim 1, characterized in that: The preset quantity is 3.

4. The method for determining the effect of residual boron on hardenability in carburized steel as described in claim 1, characterized in that: When the hardness is Rockwell hardness, the hardness threshold is 3 HRC; When the hardness is Vickers hardness, the hardness threshold is 30HV.

5. The method for determining the effect of residual boron on hardenability in carburized steel as described in claim 1, characterized in that: The tissue homogenization process includes: holding at 940~960℃ for 25~35 minutes.

6. The method for determining the effect of residual boron on hardenability in carburized steel as described in claim 1, characterized in that: The grinding depth of the measuring surface (2) is 0.4~0.5 mm from the surface of the end-quenched sample (1).

7. The method for determining the effect of residual boron on hardenability in carburized steel as described in claim 1, characterized in that: The end-quenched sample (1) has two measuring surfaces (2), and the two measuring surfaces (2) are parallel to each other; Measuring the hardness value at the measuring point on the end-quenched sample (1) specifically includes the following steps: Measure the hardness values ​​of the measurement points on the two measurement surfaces (2) of the end-quenched sample (1), calculate the average value of the hardness values ​​of the measurement points that are equidistant from the quenched end (3), and use the average value as the hardness value of the measurement point.

8. The method for determining the effect of residual boron on hardenability in carburized steel as described in claim 1, characterized in that, Before subjecting the end-quenched sample (1) to end-quenching under the second condition, the judgment method further includes the following steps: The end-quenched sample (1) is installed in the hardenability sample heating tank (4), and cast iron (5) is placed at the bottom of the hardenability sample heating tank (4). The cast iron (5) is made of ductile iron plate or gray cast iron sheet. The end-quenched sample (1) is separated from the cast iron (5) by oil-impregnated paper.

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