Method for displaying and evaluating phosphorus segregation of high-carbon steel wire rod

Abstract

The invention provides a method for displaying and evaluating phosphorus segregation of a high-carbon steel wire rod, which comprises the detailed steps of preparing a sample, preparing a phosphorus segregation etching solution, displaying and evaluating the phosphorus segregation of the high-carbon steel wire rod, detecting a standard map and the like. Distilled water and ethyl alcohol are sequentially added, finally FeCl3 and CuCl2 are added, and the mixture needs to be heated to 400 DEG C on a heating plate; in the detection process, the prepared etchant is used for etching a detection sample by adopting a wiping method, an optical microscope is used for observation, the position, with the most serious white band shape, of the longitudinal section of the sample serves as a measurement position, and the grade is evaluated according to the comparison between the percentage of the white linear part and the manufactured standard map. The phosphorus segregation condition of the high-carbon steel wire rod can be clearly displayed, so that the phosphorus segregation detection process of the high-carbon steel wire rod is standardized and normalized, and the method can be widely applied to phosphorus segregation detection of various high-carbon steel wire rods.

Description

Technical Field

[0001] The invention relates to the technical field of phosphorus segregation detection of high carbon steel wire rods, in particular to a method for displaying and evaluating phosphorus segregation of high carbon steel wire rods. Technical Background

[0002] Phosphorus is an element that solid solution strengthens ferrite. The radius of a phosphorus atom is much larger than the radius of the interstitial space of austenite octahedron, and the radius difference between it and the metal ion is also large. Therefore, whether phosphorus exists in the alloy in an interstitial or substitutional manner, it will cause great lattice distortion. Lattice distortion increases the resistance to dislocation movement and makes slip difficult, thereby increasing the strength and hardness of the alloy solid solution, while its toughness and plasticity decrease. To a certain extent, "brittle fracture" may occur.

[0003] When phosphorus exists in steel, it will repel carbon. Therefore, where the phosphorus content is high, the carbon content is low. Therefore, it can form ferrite band segregation with high solid solution phosphorus in steel, also known as "ghost line". In view of these characteristics of phosphorus in steel, it is often difficult to find its segregation during chemical analysis. Sometimes, although the phosphorus content in steel is within the specified range, the cold brittleness of the steel is extremely significant. At this time, it is necessary to detect and evaluate phosphorus segregation.

[0004] At present, the standards for testing the center segregation of high carbon steel wire rods include ISO16120-1 and YB / T4413. These standards have good characterization and evaluation of center carbon segregation, but are not suitable for center phosphorus segregation. Existing literature, textbooks, national or industry standards use sodium thiosulfate etchant to test the phosphorus segregation of high carbon steel wire rods, but the detection effect is general, the reproducibility is poor, and there is no unified evaluation method. There are human differences and the guiding significance for actual production is not strong. Summary of the invention

[0005] The present invention provides a method for displaying and evaluating phosphorus segregation of high carbon steel wire rods. A phosphorus segregation etching agent is prepared to display the phosphorus segregation area, and its grade is evaluated by using the phosphorus segregation ratio. At the same time, an evaluation standard map is prepared to facilitate rapid detection and improve detection efficiency, so as to solve the problems that the existing method cannot clearly display the phosphorus segregation of high carbon steel wire rods and there is no unified method for evaluating the phosphorus segregation grade.

[0006] The method for displaying and evaluating phosphorus segregation of high carbon steel wire rod provided by the present invention comprises the following steps in sequence:

[0007] (1) Cutting samples: Use a cutting machine to cut samples to prepare metallographic samples to be observed and measured;

[0008] (2) Grinding the sample: Use a grinder to remove the burrs on the cross sections of both ends of the sample perpendicular to the rolling direction to facilitate mounting;

[0009] (3) Mounting the sample: Place the sample vertically on the mounting machine for mounting;

[0010] (4) Rough grinding of the sample: Use a fully automatic plane pre-grinding machine to grind the sample to the core;

[0011] (5) Water-grinded specimen: Use water-grinded sandpaper to roughly grind one end of the test surface of the specimen on a grinding and polishing machine;

[0012] (6) Hand-grinded specimen: Use metallographic sandpaper to manually grind one end of the specimen test surface;

[0013] (7) Polishing the sample: Use a polishing machine to polish one end of the test surface of the sample;

[0014] (8) Wiping method for corrosion of samples: Use absorbent cotton to dip into the prepared tin-iron-copper etching solution to wipe and corrode one end of the sample test surface; the tin-iron-copper etching solution is prepared by SnCl2, FeCl3, CuCl2, hydrochloric acid, distilled water, and anhydrous ethanol;

[0015] (9) Cleaning the sample: Rinse the sample surface with anhydrous ethanol and blow dry to remove impurities on the sample surface;

[0016] (10) Observe the sample: Place the sample under an optical microscope for observation;

[0017] (11) Phosphorus segregation assessment

[0018] 11.1. Determine the test position: Under an optical microscope at 50X magnification, find the position where the white band-like part shown on the longitudinal section of the etched sample is the most serious as the test position;

[0019] 11.2. Determine the degree of phosphorus segregation: The evaluation principle is to evaluate based on the proportion P (%) of the white linear part of phosphorus segregation shown in the longitudinal section of the sample.

[0020] If the proportion P of the white linear part of phosphorus segregation is 0, the grade is 0;

[0021] If 0<P≤30, the level is 1;

[0022] If 30<P≤50, the level is 2;

[0023] If 50<P≤70, the level is 3;

[0024] If 70<P≤90, the level is 4;

[0025] If 90<P≤100, the level is 5;

[0026] (12) Preparation of standard graphs: Use an optical microscope to take metallographic images of the sample at 50X magnification, and prepare standard images of corresponding levels as test graphs.

[0027] Preferably, the ratio of SnCl2, FeCl3, CuCl2, hydrochloric acid, anhydrous ethanol and distilled water in the tin-iron-copper etching solution is 1:60:2:120:790:1000.

[0028] Preferably, the tin-iron-copper etching solution is prepared by dissolving SnCl2 in hydrochloric acid, then sequentially adding distilled water and ethanol, and finally adding FeCl3 and CuCl2, and the whole process is heated to 400°C on a heating plate.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] ① Compared with the method of measuring the phosphorus content of the cross section using a scanning electron microscope spectrometer, the hydrochloric acid, tin chloride, copper alcohol aqueous solution corrosion technology of the present invention can directly and clearly display the phosphorus-rich area of ​​the inspection surface under an optical microscope. At the same time, the evaluation principles are stipulated and the detection standard atlas is prepared, so that the detection process is standardized, normalized, simple and convenient, and a new phosphorus segregation evaluation method is proposed, and the controversy caused by inconsistent standards is avoided;

[0031] ② This patent innovatively proposes a method and principle for evaluating the grade of phosphorus segregation, and realizes scientific evaluation of phosphorus segregation. According to a large amount of test data and the service status of wire rods used by users, it is found that the evaluation of phosphorus segregation is to find the most serious position of the white band shown on the longitudinal section of the etched sample under an optical microscope with a magnification of 50X as the measurement position. The evaluation is most scientific and accurate according to the proportion (%) of the white linear part of phosphorus segregation, which is most beneficial to quality control. After consulting a large amount of literature, it is found that when phosphorus exists in steel, it will repel carbon, so the carbon content is high in places with high phosphorus content. Low, causing great lattice distortion, lattice distortion increases the resistance of dislocation movement, making it difficult to slip, thereby increasing the strength and hardness of the alloy solid solution, while its toughness and plasticity decrease. To a certain extent, "brittle fracture" may occur. When doing chemical analysis, it is often difficult to find that it has segregation. Sometimes, although the phosphorus content in the steel is within the specified range, the cold brittleness of the steel is extremely significant. At this time, it can be revealed by the test showing phosphorus segregation. Based on a large number of comparisons and explorations, it is concluded that when the phosphorus segregation is greater than level 3, it is easy to cause brittle fracture of wire rod drawing;

[0032] ③ This patent innovatively produces a standard detection map for phosphorus segregation, which enables rapid detection of phosphorus segregation. Under a 50X magnification of an optical microscope, the most severe position of the white band displayed on the longitudinal section of the etched sample is found and a metallographic image is taken. A standard image of the corresponding grade is produced as a detection map, which enables rapid detection of phosphorus segregation through the comparison method. It plays an important role in providing data support for the optimization of the high-carbon steel wire rod production process and the formulation of the best production process, and plays a positive role in product quality control. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The present invention is a flow chart of the phosphorus segregation detection method of the embodiment;

[0034] Figure 2 For the example steel cord C72D2 tin-iron-copper immersion reagent wiping method phosphorus segregation display effect, 50X;

[0035] Figure 3 The phosphorus segregation display effect of the steel cord C72D2 sodium thiosulfate etchant wiping method is shown in the example, 50X;

[0036] Figure 4 This is a scanning electron microscope verification image showing the phosphorus segregation effect of the steel cord C72D2 in the embodiment of the present invention by the wiping method using tin-iron-copper immersion reagent;

[0037] Figure 5 This is the detection spectrum of the 0-level phosphorus segregation degree;

[0038] Figure 6 This is the detection spectrum of level 1 phosphorus segregation degree;

[0039] Figure 7 It is the detection spectrum of the second level phosphorus segregation degree;

[0040] Figure 8 It is the detection spectrum of level 3 phosphorus segregation degree;

[0041] Fig. 9 It is the 4-level phosphorus segregation degree detection spectrum;

[0042] Fig.10 This is a 5-level phosphorus segregation degree detection spectrum. DETAILED DESCRIPTION

[0043] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0044] Example

[0045] See also Figure 1 This embodiment provides a method for displaying and evaluating phosphorus segregation in high carbon steel wire rods, and the specific implementation steps are as follows:

[0046] (1) Cutting samples: Use a cutting machine to cut steel cord C72D2 samples of about 20 mm to prepare metallographic samples to be observed and measured;

[0047] (2) Grinding the sample: Use a grinder to remove the burrs on the cross sections of both ends of the sample perpendicular to the rolling direction to facilitate mounting;

[0048] (3) Mounting the sample: Place the sample vertically on the mounting machine for mounting;

[0049] (4) Rough grinding of the specimen: Use a fully automatic surface pre-grinding machine to grind the specimen to the center (grind half the circumference);

[0050] (5) Water-grinded specimen: Use 600# or 1000# water-grinded sandpaper to roughly grind one end of the test surface of the specimen on a grinding and polishing machine;

[0051] (6) Hand-grinded specimen: Use 400# or 600# metallographic sandpaper to manually grind one end of the specimen test surface;

[0052] (7) Polishing the sample: Use a polishing machine to polish one end of the test surface of the sample;

[0053] (8) Wiping method for corrosion of samples: Use absorbent cotton to dip into the prepared tin-iron-copper etching solution to wipe and corrode one end of the sample test surface; the etching agent is prepared using SnCl2, FeCl3, CuCl2, hydrochloric acid, distilled water, and anhydrous ethanol. The ratio of SnCl2, FeCl3, CuCl2, hydrochloric acid, anhydrous ethanol, and distilled water is 1:60:2:120:790:1000. The preparation method is to dissolve SnCl2 in hydrochloric acid, then add distilled water and ethanol in sequence, and finally add FeCl3 and CuCl2. The whole process is heated to 400°C on a heating plate;

[0054] (9) Cleaning the sample: Rinse the sample surface with anhydrous alcohol and blow dry to remove impurities on the sample surface;

[0055] (10) Observing the sample: placing the sample under an optical microscope for observation;

[0056] (11) Characterization method of phosphorus segregation degree

[0057] 11.1. Determine the test position: Under an optical microscope at 50X magnification, find the position where the white band on the longitudinal section of the etched sample is the most serious as the test position, such as Figure 2 The display effect of the steel cord C72D2 in this embodiment is shown;

[0058] 11.2. Determine the degree of phosphorus segregation: The evaluation principle is to evaluate based on the proportion P (%) of the white linear part of phosphorus segregation shown in the longitudinal section of the sample.

[0059] If the proportion P of the white linear part of phosphorus segregation is 0, the grade is 0;

[0060] If 0<P≤30, the level is 1;

[0061] If 30<P≤50, the level is 2;

[0062] If 50<P≤70, the level is 3;

[0063] If 70<P≤90, the level is 4;

[0064] If 90<P≤100, the level is 5;

[0065] (12) Preparation of standard graphs: Use an optical microscope to take metallographic images of the sample at 50X magnification, and prepare standard images of corresponding levels as test graphs, such as Figure 5-10 The figure shows the detection spectrum of phosphorus segregation degree from 0 to 5. Figure 2 and Figure 5-10 By comparison, it can be determined that the phosphorus segregation degree of the steel cord C72D2 sample in this embodiment is level 2. Figure 3 To show the phosphorus segregation effect of steel cord C72D2 sample wiped by traditional sodium thiosulfate etchant wiping method, and Figure 2 By comparison with the method in this embodiment, it can be seen that the method in this embodiment has a better effect and can more clearly and truly display the degree of phosphorus segregation. Figure 4 This is a scanning electron microscope verification diagram of the phosphorus segregation display effect of the tin-iron-copper leaching reagent wiping method for steel cord C72D2. Figure 4 Left) and light-colored matrix area ( Figure 4 (right) Electron microscope energy spectrum detection was carried out. From the results, it can be seen that the dark strip area is richer in phosphorus than the matrix, that is, phosphorus segregation.

[0066] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

Claims

1. A method for displaying and evaluating phosphorus segregation in high carbon steel wire rod, characterized in that: The method comprises the following steps in sequence: (1) Cutting samples: Use a cutting machine to cut samples to prepare metallographic samples to be observed and measured; (2) Grinding the sample: Use a grinder to remove the burrs on the cross sections of both ends of the sample perpendicular to the rolling direction to facilitate mounting; (3) Mounting the sample: Place the sample vertically on the mounting machine for mounting; (4) Rough grinding of the sample: Use a fully automatic plane pre-grinding machine to grind the sample to the core; (5) Water-grinded specimen: Use water-grinded sandpaper to roughly grind one end of the test surface of the specimen on a grinding and polishing machine; (6) Hand-grinded specimen: Use metallographic sandpaper to manually grind one end of the specimen test surface; (7) Polishing the sample: Use a polishing machine to polish one end of the test surface of the sample; (8) Wiping method for corrosion of samples: Use absorbent cotton to dip into the prepared tin-iron-copper etching solution to wipe and corrode one end of the sample test surface; the tin-iron-copper etching solution is prepared by SnCl2, FeCl3, CuCl2, hydrochloric acid, distilled water, and anhydrous ethanol; (9) Cleaning the sample: Rinse the sample surface with anhydrous ethanol and blow dry to remove impurities on the sample surface; (10) Observe the sample: Place the sample under an optical microscope for observation; (11) Phosphorus segregation assessment 11.

1. Determine the test position: Under an optical microscope at 50X magnification, find the position where the white band-like part shown on the longitudinal section of the etched sample is the most serious as the test position; 11.

2. Determine the degree of phosphorus segregation: The evaluation principle is to evaluate based on the proportion P (%) of the white linear part of phosphorus segregation shown in the longitudinal section of the sample; If the proportion P of the white linear part of phosphorus segregation is 0, the grade is 0; If 0<P≤30, the level is 1; If 30<P≤50, the level is 2; If 50<P≤70, the level is 3; If 70<P≤90, the level is 4; If 90<P≤100, the level is 5; (12) Preparation of standard graphs: Use an optical microscope to take metallographic images of the sample at 50X magnification, and prepare standard images of corresponding levels as test graphs.

2. The method for displaying and evaluating phosphorus segregation in high carbon steel wire rod according to claim 1, characterized in that: The ratio of SnCl2, FeCl3, CuCl2, hydrochloric acid, anhydrous ethanol and distilled water in the tin-iron-copper etching solution is 1:60:2:120:790:1000.

3. The method for displaying and evaluating phosphorus segregation in high carbon steel wire rod according to claim 1, characterized in that: The tin-iron-copper etching solution is prepared by dissolving SnCl2 in hydrochloric acid, then sequentially adding distilled water and ethanol, and finally adding FeCl3 and CuCl2, and the whole process is heated to 400° C. on a heating plate.

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