阅读说明：本技术 一种基于微观析出物的重轨凝固过程微观偏析表征方法 (Heavy rail solidification process microsegregation characterization method based on microcosmic precipitates ) 是由 李红光 陈天明 陈亮 黎建全 于 2020-06-03 设计创作，主要内容包括：本发明涉及钢铁冶金技术领域,公开了一种基于微观析出物的重轨凝固过程微观偏析表征方法。该方法包括：(1)对钢轨轧材按垂直于轧制方向进行切割并获得检验面；(2)按非金属夹杂金相显微评级检验标准对检验面进行制样；(3)制样结束后,采用Aspex对检验面的非金属夹杂进行扫描统计；(4)扫描结束后,对数据进行筛选提取,重点筛选MnS非金属夹杂,并统计MnS非金属夹杂尺寸；(5)结合MnS非金属夹杂的Map结果比较区域宏观分布。该方法可以更为全面的评价钢材凝固过程微观偏析控制情况,进一步结合轧制过程遗传性研究可以有效回溯到铸坯较大区域进行控制工艺分析,开展工艺效果平行比较,进而科学指导工艺优化改进研究。(The invention relates to the technical field of ferrous metallurgy, and discloses a heavy rail solidification process micro segregation characterization method based on micro precipitates. The method comprises the following steps: (1) cutting a steel rail rolled material in a direction perpendicular to a rolling direction to obtain a test surface; (2) preparing a sample of the inspection surface according to a nonmetal inclusion metallographic microscopic grading inspection standard; (3) after sample preparation is finished, carrying out scanning statistics on nonmetal impurities on the inspection surface by adopting Aspex; (4) after scanning is finished, screening and extracting data, mainly screening MnS non-metallic inclusions, and counting the sizes of the MnS non-metallic inclusions; (5) the macroscopic distribution of the regions was compared in combination with Map results for MnS non-metallic inclusions. The method can more comprehensively evaluate the microcosmic segregation control condition in the steel solidification process, and further combine with the rolling process hereditary research to effectively backtrack to a larger area of the casting blank for control process analysis and develop parallel comparison of process effects, thereby scientifically guiding the process optimization and improvement research.)

1. A micro segregation characterization method based on a micro precipitate in a heavy rail solidification process is characterized by comprising the following steps:

(1) cutting a steel rail rolled material in a direction perpendicular to a rolling direction to obtain a test surface;

(2) preparing a sample of the inspection surface according to a nonmetal inclusion metallographic microscopic grading inspection standard;

(3) after sample preparation is finished, carrying out scanning statistics on nonmetal impurities on the inspection surface by adopting Aspex;

(4) after scanning is finished, screening and extracting data, mainly screening MnS non-metallic inclusions, and counting the sizes of the MnS non-metallic inclusions;

(5) the macroscopic distribution of the regions was compared in combination with Map results for MnS non-metallic inclusions.

2. The method according to claim 1, wherein in step (1), the check surface is a cross section perpendicular to the rolling direction.

3. The method according to claim 1, wherein in the step (2), when Aspex is used to perform scanning statistics on non-metallic inclusions on the inspection surface, the scanning area is the horizontal width dimension x the height dimension.

4. The method of claim 3, wherein in step (2), the scan area is 120-130mm²。

5. The method of claim 4, wherein in step (2), the scan area is 121-128mm²。

6. The method of claim 3, wherein in step (2), the horizontal width dimension is 3.5-4 mm.

7. The method of claim 3, wherein in step (2), the height dimension is 30-35 mm.

8. The method according to claim 1, wherein in step (2), the distance between the inspection area and the tread is 3-4mm when Aspex is used to perform scanning statistics on non-metallic inclusions on the inspection surface.

9. The method of claim 1, wherein in step (4), the MnS non-metallic inclusion sizes include single particle length, mean particle area, and precipitation two-dimensional area ratio.

10. The method according to claim 1, wherein in the step (4), the solidification process microsegregation control evaluation is mainly determined in terms of a precipitated two-dimensional area ratio, and a higher precipitated two-dimensional area ratio indicates that the microsegregation occurring in the solidification process is more serious.

Technical Field

The invention relates to the technical field of ferrous metallurgy, in particular to a micro segregation characterization method based on micro precipitates in a heavy rail solidification process.

Background

Based on the development requirements of the infrastructure of China, railway transportation is developing at a rapid speed and is continuously tending to high speed and heavy loading. This undoubtedly puts more stringent requirements on rail quality. The rails are the main components of the railroad track, and provide effective support and guidance for the locomotive during railroad transportation, and are subject to significant vertical pressure from the wheels. When the steel rail is in contact with the wheels, the steel rail bears the reciprocating and variable load of the locomotive loop, and the purity of the steel rail has an important influence on the fatigue life of the steel rail. Due to the blocking effect of the inclusions in the steel on the continuity of the steel matrix structure, the steel is separated from the inclusions in the rolling processing, heat treatment and use processes, so that gaps are generated, and indexes such as mechanical property, corrosion resistance and the like of the steel are negatively influenced.

The quality of the steel rail is improved to a certain extent in the quality control level of the steel, such as high homogeneity, high cleanliness and high component precision. The homogeneity of the steel rail (the smaller the segregation degree, the higher the homogeneity of the steel rail) affects the uniformity of steel structure, and the serious segregation affects the welding performance of the steel rail base metal and the steel rail, thereby affecting the service and use of the steel rail. In the metallurgical industry, a large number of expert scholars have conducted detailed studies on the segregation of casting blanks, and the studies indicate that: in the process of molten steel solidification, due to redistribution of solute elements in solid and liquid phases, chemical components of successively solidified areas of a casting blank are not uniform, and macroscopic segregation is generated. Meanwhile, researches indicate that solid phase components crystallized from liquid successively are different in the process of molten steel solidification, so that chemical components in one crystal grain are not uniform, the phenomenon is called intragranular segregation, and the intragranular segregation belongs to micro segregation. In addition, when solute elements in the crystal grains are continuously precipitated and aggregated from a liquid phase to a solid phase, a large amount of solute elements are enriched on the crystal dry surface of the crystal grains, grain boundary (or intercrystalline) segregation is generated, and the serious intercrystalline segregation scale can reach a semi-macroscopic scale.

At present, the majority of the homogeneity tests of the solute element distribution of steel products are macroscopic tests (the test scale is phi 2-phi 8mm), the more mature technical means for the test of the microscopic homogeneity are EPMA (electronic probe) and thermal field emission scanning electron microscope, but because the microscopic segregation tests have high magnification (mostly dozens to hundreds of mum 2) of the field of view of the detection micro-region, and more researches are that the parallel comparison is carried out in the same region of samples of different experimental processes, the guiding significance of the analysis result is very limited, and the natural optimization guiding significance to the experimental process is insufficient. The microsegregation of steel materials is frequently studied, and most of the studies are focused on controlling the microsegregation and numerical simulation calculation studies. For example:

chinese patent CN110508763A discloses a microcosmic segregation control method for heavy rail steel with an ultra-large section in the field of ferrous metallurgy, which emphasizes the control by adopting the following steps in the continuous casting stage, wherein the continuous casting electromagnetic stirring adopts a mode of combining electromagnetic stirring with secondary cooling electromagnetic stirring, and the stirring magnetic field intensity of the electromagnetic stirring is 30 × 10^-4～40×10^-4T, the specific installation position of the secondary cooling electromagnetic stirring is within 7.0-8.0 m from the steel liquid level of the crystallizer, the stirring current frequency is 6.0-7.5 Hz, and the magnetic field intensity is 200 × 10^-4～250×10^-4T; the superheat degree of the tundish casting molten steel is executed according to 35-40 ℃; the continuous casting secondary cooling section needs a secondary cooling area to cover 17.0m away from the molten steel surface of the crystallizer. The local solidification rate of the large square billet of the heavy rail steel with the oversized section is improved by controlling the parameters, so that the solidification structure composition of the casting blank is improved and controlled, the columnar crystal is developed, the crystal bar is thin and compact, the shape of the isometric crystal grain is changed, the crystal bar is thin, compact and clear, the distance between secondary dendrite arms is reduced, and the microsegregation degree is well controlled. The method mainly focuses on the research of control process technology, but does not relate to the 'micro segregation characterization method based on the heavy rail solidification process of micro precipitates'.

Chinese patent CN110508770A discloses a microsegregation control method for heavy rail steel in bloom in the field of ferrous metallurgy, emphasizing the control in the continuous casting stage by adopting the following steps that the continuous casting electromagnetic stirring adopts a mode of combining electromagnetic stirring with secondary cooling electromagnetic stirring, and the stirring magnetic field intensity of the electromagnetic stirring is 40 × 10^-4～50×10^-4T, secondary cooling electromagnetismthe installation position of the stirrer is 5.0-6.0 m away from the steel liquid surface of the crystallizer, the stirring current frequency is 6.0-8.0 Hz, and the magnetic field intensity is 180 × 10^-4～200×10^-4T; the superheat degree of the tundish casting molten steel is executed according to 35-45 ℃; in the continuous casting secondary cooling stage, a secondary cooling area is required to cover to a distance of 15.0m from the molten steel surface of the crystallizer. The method is controlled according to the parameters, the local solidification rate of the bloom heavy rail steel is improved, the solidification structure composition of the casting blank is improved and controlled, columnar crystals are developed, a crystal bar is thin and compact, the shape of isometric crystal grains is changed, the crystal bar is thin, compact and clear, the distance between secondary dendrite arms is reduced, and the microsegregation degree is well controlled. The method mainly focuses on the research of control process technology, but does not relate to the 'micro segregation characterization method based on the heavy rail solidification process of micro precipitates'.

Chinese patent CN110470687A discloses a method for rapidly positioning and evaluating the microsegregation of heavy rail steel in the field of ferrous metallurgy, which comprises the following steps: firstly, a metal in-situ detection analyzer is utilized to carry out micro segregation extreme value inspection and the primary positioning of an extreme value target area, then a sample which is subjected to metal in-situ scanning and then is positioned in the target area is subjected to linear cutting processing, a metallographic sample in the target area is cut, a sample is prepared on a detection surface of the sample according to a metallographic inspection standard, finally a thermal field emission scanning electron microscope is used for carrying out micro segregation surface scanning inspection on the target area, and the accurate positioning of a micro segregation extreme value point is completed. The microcosmic segregation extreme point obtained by the method is accurately positioned, and can provide important criterion reference for the optimization of heavy rail steel casting blanks and the steel rail homogeneity improvement process. The invention does not relate to the 'micro segregation characterization method based on the heavy rail solidification process of micro precipitates'.

Chinese patent CN110117761A discloses a method for reducing micro segregation during alloy solidification. The invention provides a method for reducing micro segregation in an alloy solidification process, which comprises the following steps: and in a steady magnetic field, directionally solidifying the Al-Cu alloy melt to obtain the Al-Cu alloy. According to the description of the embodiment, the amount of the nonequilibrium second phase (Al2Cu) of the Al-Cu alloy treated by the method is obviously reduced, the solute distribution is more uniform, and the micro segregation is improved. The invention does not relate to the 'micro segregation characterization method based on the heavy rail solidification process of micro precipitates'.

Chinese patent CN105466961A discloses an evaluation method for segregation of alloy elements of a continuously cast steel billet, belonging to the technical field of component analysis of continuously cast steel billets. Processing the continuous casting billet into a sample suitable for a sample table; carrying out surface scanning analysis on the continuous casting billet sample by using an electronic probe; defining a segregation degree A; writing an M program by utilizing Matlab software to calculate the value of A; comparing the segregation degree A and determining the segregation degree of the alloy elements of the continuous casting billet. The method has the advantage of providing basis for optimizing the continuous casting process. The invention does not relate to the 'micro segregation characterization method based on the heavy rail solidification process of micro precipitates'.

Disclosure of Invention

The invention aims to solve the problem that the heavy rail solidification process microsegregation characterization method based on microcosmic precipitates in the prior art is not researched, and provides the heavy rail solidification process microsegregation characterization method based on microcosmic precipitates.

In order to achieve the aim, the invention provides a micro segregation characterization method based on a micro precipitate heavy rail solidification process, which is characterized by comprising the following steps of:

(1) cutting a steel rail rolled material in a direction perpendicular to a rolling direction to obtain a test surface;

(2) preparing a sample of the inspection surface according to a nonmetal inclusion metallographic microscopic grading inspection standard;

(3) after sample preparation is finished, carrying out scanning statistics on nonmetal impurities on the inspection surface by adopting Aspex;

(4) after scanning is finished, screening and extracting data, mainly screening MnS non-metallic inclusions, and counting the sizes of the MnS non-metallic inclusions;

(5) the macroscopic distribution of the regions was compared in combination with Map results for MnS non-metallic inclusions.

Preferably, in step (1), the test surface is a cross section perpendicular to the rolling direction.

Preferably, in the step (2), when Aspex is used to perform scanning statistics on the non-metallic inclusions on the inspection surface, the scanning area is the horizontal width dimension x height dimension.

Preferably, in step (2), the scan area is 120-130mm²。

More preferably, in step (2), the scan area is 121-128mm²。

Preferably, in step (2), the horizontal width dimension is 3.5 to 4 mm.

Preferably, in step (2), the height dimension is 30-35 mm.

Preferably, in the step (2), when Aspex is used for scanning and counting the non-metallic inclusions on the inspection surface, the distance between the inspection area and the tread is 3-4 mm.

Preferably, in the step (4), the MnS nonmetallic inclusion sizes include single-particle length, average particle area, and precipitation two-dimensional area ratio.

Preferably, in the step (4), the solidification process microsegregation control evaluation is mainly determined in terms of a precipitated two-dimensional area ratio, and a higher precipitated two-dimensional area ratio indicates that the microsegregation occurring in the solidification process is more serious.

The method can more comprehensively evaluate the microcosmic segregation control condition in the steel solidification process, further combine with the genetic research in the rolling process, effectively backtrack to a larger area of the casting blank for control process analysis, develop parallel comparison of process effects and further scientifically guide the process optimization and improvement research.

Drawings

FIG. 1 is a cross-sectional Map of MnS non-metallic inclusions.

Detailed Description

The following detailed description of embodiments of the invention refers to the accompanying drawings. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.

The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.

The invention discloses a micro segregation characterization method based on a micro precipitate in a heavy rail solidification process, which comprises the following steps of:

(1) cutting a steel rail rolled material in a direction perpendicular to a rolling direction to obtain a test surface;

(2) preparing a sample of the inspection surface according to a nonmetal inclusion metallographic microscopic grading inspection standard;

(3) after sample preparation is finished, carrying out scanning statistics on nonmetal impurities on the inspection surface by adopting Aspex;

(4) after scanning is finished, screening and extracting data, mainly screening MnS non-metallic inclusions, and counting the sizes of the MnS non-metallic inclusions;

(5) map results in combination with MnS non-metallic inclusions compare area macroscopic distribution (as shown in fig. 1).

In the method of the present invention, in the step (1), the test surface is a cross section perpendicular to the rolling direction. In the step (2), when Aspex is used to perform scanning statistics on the non-metallic inclusions on the inspection surface, the scanning area is the horizontal width dimension x height dimension.

In the step (2), the scanning area is 120-130mm²Specifically, for example, it may be 120mm²、121mm²、122mm²、123mm²、124mm²、125mm²、126mm²、127mm²、128mm²、129mm²、130mm²And any value in the range of any two of these point values. Preferably, in the step (2), theThe scanning area is 121-128mm²。

In step (2), the horizontal width dimension is 3.5 to 4mm, and specifically, may be, for example, 3.5mm, 3.6mm, 3.7mm, 3.8mm, 3.9mm, 3.5mm, and any value in the range of any two of these point values. Preferably, in step (2), the horizontal width dimension is 3.8 mm.

In step (2), the height dimension is 30 to 35mm, and specifically, may be, for example, 30mm, 31mm, 32mm, 33mm, 34mm, 35mm, and any value in the range of any two of these point values. Preferably, in step (2), the height dimension is 32 mm.

In the method of the present invention, in step (2), when the non-metallic inclusions on the inspection surface are scanned and counted by Aspex, the distance between the inspection area and the tread surface is 3 to 4mm, specifically, for example, 3mm, 3.2mm, 3.4mm, 3.6mm, 3.8mm, 4mm, or any value in the range of any two of these point values. Preferably, in the step (2), when the non-metallic inclusions on the inspection surface are scanned and counted by Aspex, the distance between the inspection area and the tread is 3.5 mm.

In the method of the present invention, in the step (4), the MnS nonmetallic inclusion sizes include a single particle length, an average particle area, and a precipitation two-dimensional area ratio. In the step (4), the micro segregation control evaluation judgment in the solidification process is mainly carried out according to the precipitated two-dimensional area proportion, and the higher the precipitated two-dimensional area proportion is, the more serious the micro segregation generated in the solidification process is.

The method can more comprehensively evaluate the microcosmic segregation control condition in the steel solidification process, further combine with the genetic research in the rolling process, effectively backtrack to a larger area of the casting blank for control process analysis, develop parallel comparison of process effects and further scientifically guide the process optimization and improvement research.

The present invention will be described in detail by way of examples, but the scope of the present invention is not limited thereto.