阅读说明：本技术 定量表征中高碳盘条中心偏析的方法 (Method for quantitatively characterizing center segregation of medium-high carbon wire rod ) 是由 鲁修宇 夏艳花 仇东丽 郭磊 周勇 于 2021-06-22 设计创作，主要内容包括：本发明公开了一种定量表征中高碳盘条中心偏析的方法,该方法包括如下步骤：1)对盘条横截面进行前处理；2)对盘条横截面进行显微硬度测量,记录盘条横截面的显微硬度测量结果；3)统计硬度测量结果的均值、极大值,根据均值、极大值计算偏差率；4)根据偏差率来表征盘条横截面的中心偏析级别。本发明的定量表征中高碳盘条中心偏析的方法借助显微硬度手段来科学定量表征盘条的偏析程度,结果具有可量化特点,能够进行准确的评价,而且,测量结果不易受到外界因素的干扰,稳定性好。(The invention discloses a method for quantitatively characterizing center segregation of a medium-high carbon wire rod, which comprises the following steps: 1) pre-treating the cross section of the wire rod; 2) carrying out microhardness measurement on the cross section of the wire rod, and recording the microhardness measurement result of the cross section of the wire rod; 3) counting the mean value and the maximum value of the hardness measurement result, and calculating the deviation rate according to the mean value and the maximum value; 4) and characterizing the center segregation level of the cross section of the wire rod according to the deviation rate. The method for quantitatively characterizing the center segregation of the medium-high carbon wire rod scientifically and quantitatively characterizes the segregation degree of the wire rod by means of microhardness, has the characteristic of quantifiability in result, can perform accurate evaluation, is not easily interfered by external factors in the measurement result, and has good stability.)

1. A method for quantitatively characterizing center segregation of a medium-high carbon wire rod is characterized by comprising the following steps: the method comprises the following steps:

1) pre-treating the cross section of the wire rod;

2) carrying out microhardness measurement on the cross section of the wire rod, and recording the microhardness measurement result of the cross section of the wire rod;

3) counting the mean value and the maximum value of the hardness measurement result, and calculating the deviation rate according to the mean value and the maximum value; the deviation ratio is calculated as follows:

4) characterizing the center segregation level of the cross section of the wire rod according to the deviation rate; if the deviation rate is less than or equal to 9 percent, the central segregation grade of the wire rod is 1 grade; if the deviation rate is more than 9% and less than or equal to 14%, the central segregation grade of the wire rod is 2 grades; if the deviation rate is more than 14% and less than or equal to 24%, the central segregation grade of the wire rod is 3 grades; if the deviation rate is more than 24% and less than or equal to 32%, the central segregation grade of the wire rod is 4 grades; if the deviation rate is more than 32%, the center segregation grade of the wire rod is 5 grades.

2. The method for quantitatively characterizing the center segregation of medium-high carbon wire rods according to claim 1, wherein the method comprises the following steps: in the step 1), the pretreatment comprises the steps of inlaying the cross section of the wire rod, grinding the metallographic abrasive paper step by step and mechanically polishing.

3. The method for quantitatively characterizing the center segregation of medium-high carbon wire rods according to claim 1, wherein the method comprises the following steps: in the step 2), microhardness measurement is carried out by taking the geometric center of the cross section of the wire rod as a central point, N line segments passing through the geometric center of the cross section of the wire rod are selected as measurement line segments at the measurement position, and the number N of the measurement line segments is more than or equal to 2.

4. The method for quantitatively characterizing the center segregation of medium-high carbon wire rods according to claim 3, wherein the method comprises the following steps: the included angle between the measuring line segments is 180 degrees/N, wherein N is the number of the measuring line segments.

5. The method for quantitatively characterizing the center segregation of medium-high carbon wire rods according to claim 4, wherein the method comprises the following steps: and selecting a plurality of measuring points on the measuring line segment.

6. The method for quantitatively characterizing the center segregation of medium-high carbon wire rods according to claim 5, wherein the method comprises the following steps: the interval between two adjacent measuring points is 0.5-1 mm.

7. The method for quantitatively characterizing the center segregation of medium-high carbon wire rods according to claim 6, wherein the method comprises the following steps: the measuring line segment starts from the cross section surface of the wire rod, passes through the geometric center of the cross section of the wire rod and ends at the cross section surface of the wire rod at the other symmetrical side.

8. The method for quantitatively characterizing the center segregation of medium-high carbon wire rods according to claim 7, wherein: the distance between the measurement starting point and the measurement ending point of the measurement point and the surface of the wire rod is 1-2 mm.

Technical Field

The invention relates to the technical field of wire rod center segregation detection, in particular to a method for quantitatively characterizing center segregation of a medium-high carbon wire rod.

Background

The wire rod is a coiled small-diameter round steel, is mainly used for wire drawing or cold heading deep processing, and can also be directly used as a building material, and typical products represent: prestressed wires, spring wires, tire meridian wires, ribbed steel bars, and the like. The wire rod has a plurality of varieties, and can be divided into low carbon, medium carbon and high carbon steel according to the carbon content.

The center segregation of the wire rod refers to the abnormal aggregation of partial alloy elements, which can cause the local structural abnormality of the wire rod under the same cooling control condition, and even cause the reticular carbide of medium and high carbon steel wire rods. Uneven structure of the wire rod can form stress concentration in the later deep processing process, and the processing performance is obviously deteriorated. The wire rod has wide application fields, the influence of center segregation on medium and high carbon wire rods is large, for example, spring steel, bridge cable steel, cord steel and the like, the center segregation can cause fatigue fracture of the spring steel wire, poor torsion performance of the bridge cable steel wire, stranded wire breakage of the cord steel wire and the like seriously, and the center segregation of the wire rod is a very important index for the medium and high carbon steel. With the increase of the carbon content of the wire rod, the degree of center segregation can be greatly increased, and the influence on downstream products is larger.

At present, no quantitative evaluation method and standard aiming at the center segregation of a wire rod exist in the industry, and GB/T424242.1-2009, part 1 of non-alloy steel wire rod for wire making: general requirements, the standard divides the segregation of the wire rod into 1-5 levels according to the inverse differential color of the macroscopic morphology of the corroded cross section of the wire rod, the higher the segregation degree is, the higher the level is, the more the level is, the specific operation process needs to be compared by referring to a standard map, no quantitative data exists, and accurate comparison cannot be carried out; in addition, the rating result of the current standard is mainly influenced by the degree of corrosion by virtue of the contrast of the cross section after corrosion, and is easily influenced by factors such as experience, habits, working states and the like of a rater, and the rating result is different from person to person.

In the prior art, the chinese patent application No. CN 201210418952.6 discloses a method for quantitatively characterizing the center segregation of a wire rod, which comprises the steps of firstly distinguishing a carburized phase and a ferrite phase, measuring the carbon content of different positions of a high-carbon steel wire rod by using 3DAP, at least comprising a place with serious segregation and a place without segregation, and comparing and evaluating the center segregation of the high-carbon steel wire rod. The method can quantitatively evaluate the carbon segregation of the pearlite high-carbon steel hot-rolled wire rod, but needs to identify the metallographic structure of the wire rod, and relates to a 3DAP means.

Chinese patent application No. CN201110241961.8 discloses a quantitative test method for center segregation of wire rod, which utilizes the spectral analysis of characteristic X-ray of element to perform the line analysis and measurement of the intensity of X-ray of carbon and manganese elements on the full width of the sample, and records the intensity with curve, then converts the intensity of X-ray in the curve into the concentration content, and obtains the maximum and average values of concentration from the curve, and further obtains the center segregation value. The method has complicated sample preparation process and needs X-ray spectrum analysis.

The Chinese patent with the application number of CN201310624451.8 discloses a quantitative detection method for carbon segregation of a wire rod, which comprises the following steps: 1) cutting a cross section sample of the wire rod, and preparing a metallographic sample; 2) performing carbon element line scanning along the diameter of the sample of the cross section of the wire rod; 3) respectively carrying out point measurement on a group of iron-based carbon standard samples, recording the obtained characteristic X-ray intensity, and establishing a working curve of the relation between the X-ray intensity and the carbon content of the standard samples; 4) carrying out quantitative correction calculation on the line scanning result of the sample by using the working curve; 5) and calculating to obtain the maximum carbon content Cm at the center and the average value Ca of the carbon content on the whole diameter, wherein the wire rod carbon segregation index P of the sample is Cm/Ca. The method is based on element line scanning and X-ray intensity detection means.

Therefore, there is a need to find a new measuring method which can accurately and quantitatively characterize the degree of center segregation of the wire rod.

Disclosure of Invention

The invention aims to overcome the defects of the background technology and provide a method for quantitatively characterizing the center segregation of a medium-high carbon wire rod. .

In order to achieve the aim, the invention provides a method for quantitatively characterizing center segregation of a medium-high carbon wire rod, which comprises the following steps:

1) pre-treating the cross section of the wire rod;

2) carrying out microhardness measurement on the cross section of the wire rod, and recording the microhardness measurement result of the cross section of the wire rod;

3) counting the mean value and the maximum value of the hardness measurement result, and calculating the deviation ratio according to the mean value and the maximum value, wherein the calculation method of the deviation ratio comprises the following steps:

4) characterizing the center segregation level of the cross section of the wire rod according to the deviation rate; if the deviation rate is less than or equal to 9 percent, the central segregation grade of the wire rod is 1 grade; if the deviation rate is more than 9% and less than or equal to 14%, the central segregation grade of the wire rod is 2 grades; if the deviation rate is more than 14% and less than or equal to 24%, the central segregation grade of the wire rod is 3 grades; if the deviation rate is more than 24% and less than or equal to 32%, the central segregation grade of the wire rod is 4 grades; if the deviation rate is more than 32%, the center segregation grade of the wire rod is 5 grades.

Further, in the step 1), the pretreatment includes embedding the cross section of the wire rod, grinding the metallographic abrasive paper step by step and mechanically polishing.

Further, in the step 2), microhardness measurement is performed by taking the geometric center of the cross section of the wire rod as a central point, N line segments passing through the geometric center of the cross section of the wire rod are selected as measurement line segments at the measurement position, and the number N of the measurement line segments is more than or equal to 2.

Further, the included angle between the measuring line segments is 180 degrees/N, wherein N is the number of the measuring line segments.

Furthermore, a plurality of measuring points are selected from the measuring line segment.

Further, the interval between two adjacent measuring points is 0.5-1 mm.

Still further, the measuring line segment starts from the cross-sectional surface of the wire rod, passes through the geometric center of the cross-sectional surface of the wire rod, and ends at the cross-sectional surface of the wire rod at the other symmetrical side.

Furthermore, the distance between the measurement starting point and the measurement ending point of the measurement point and the surface of the wire rod is 1-2 mm.

Compared with the prior art, the invention has the following advantages:

firstly, the method scientifically and quantitatively represents the segregation degree of the wire rod by means of microhardness, the result has the characteristic of quantification and can be accurately evaluated, the measurement result has a corresponding relation with the traditional evaluation level, the evaluation result can correspond to the traditional central segregation level and has consistency with the original standard, and understanding is facilitated.

Secondly, the measurement result of the method for quantitatively characterizing the center segregation of the medium-high carbon wire rod is not easily interfered by external factors (detection personnel and measurement instruments), the stability is good, the evaluation result can be quantized, and the accurate comparison can be carried out between the same center segregation levels.

Thirdly, the method for quantitatively characterizing the center segregation of the medium-high carbon wire rod does not need to carry out steps on the sample, the picture evaluation of the traditional method is easily influenced by the integral corrosion degree of the wire rod, and the stability of the measuring result of the method is good.

Drawings

Fig. 1 is a schematic diagram of the selection of a cross-section measurement line segment of a wire rod in embodiment 1 of the present invention;

FIG. 2 is a schematic diagram of the selection of a cross-section measurement line segment of a wire rod in embodiment 2 of the present invention;

in the figure, the cross section 1 of the wire rod, the line segment 2 is measured.

Detailed Description

The following describes the embodiments of the present invention in detail with reference to the embodiments, but they are not intended to limit the present invention and are only examples. While the advantages of the invention will be apparent and readily appreciated by the description. The invention discloses a method for quantitatively characterizing center segregation of a medium-high carbon wire rod, which comprises the following steps:

1) the cross section of the wire rod is pretreated, the cross section of the wire rod is inlaid, and metallographic abrasive paper is gradually ground and mechanically polished, so that the cross section of the wire rod is free of visible scratches, and nitric acid and alcohol corrosion is not required.

2) Carrying out microhardness measurement on the cross section of the wire rod, and recording the microhardness measurement result of the cross section of the wire rod; and (3) carrying out microhardness measurement by taking the geometric center of the cross section of the wire rod as a central point, selecting N line segments passing through the geometric center of the cross section of the wire rod as measurement line segments at the measurement position, wherein the number N of the measurement line segments is more than or equal to 2. The included angle between the measuring line segments is 180 degrees/N, wherein N is the number of the measuring line segments. And selecting a plurality of measuring points on the measuring line segment. The interval between two adjacent measuring points is 0.5-1 mm. The measuring line starts from the cross section surface of the wire rod, passes through the geometric center of the cross section of the wire rod and ends at the cross section surface of the wire rod at the other symmetrical side. The distance between the measurement starting point and the measurement ending point of the measurement point and the surface of the wire rod is 1-2 mm. The microhardness measuring method adopts HV10, the measuring indentation is small, the measuring area is small, and the result is stable.

3) Counting the mean value and the maximum value of the hardness measurement result, and calculating the deviation rate according to the mean value and the maximum value; the deviation ratio is calculated as follows:

4) representing the center segregation level of the cross section of the wire rod according to the deviation rate, wherein if the deviation rate is less than or equal to 9%, the center segregation level of the wire rod is 1 level; if the deviation rate is more than 9% and less than or equal to 14%, the central segregation grade of the wire rod is 2 grades; if the deviation rate is more than 14% and less than or equal to 24%, the central segregation grade of the wire rod is 3 grades; if the deviation rate is more than 24% and less than or equal to 32%, the central segregation grade of the wire rod is 4 grades; if the deviation rate is more than 32%, the center segregation grade of the wire rod is 5 grades. The specific correspondence between the microhardness of the wire rod and the center segregation level is shown in table 1.

TABLE 1

Example 1:

1) a1 # wire rod (with the diameter of 12.0mm and the concentration of 0.72 percent C) is taken to be inlaid, and metallographic abrasive paper is gradually ground and mechanically polished, so that the section of the wire rod has no visible scratches, and is not corroded by nitric acid and alcohol.

2) The microhardness measurement is carried out on the cross section 1 of the wire rod by means of microhardness (HV10), the measurement is carried out by taking the geometric center of the wire rod as a central point, two perpendicular line segments passing through the geometric center of the cross section of the sample are selected as measurement line segments 2 at the measurement positions, the included angle between the measurement line segments is 90 degrees, the interval between the measurement points is 0.5mm, the distance between the measurement starting point and the measurement ending point and the surface of the wire rod is 1.0mm, the measurement quantity on a single measurement line segment 2 is 21 points, and the total of the two measurement line segments of the cross section of the wire rod is 42 points. The cross-sectional microhardness (HV10) of the # 1 wire rod was measured as follows:

TABLE 2

3) Counting the measurement result of microhardness of the cross section of the wire rod: the microhardness has an average value of 386.8 and a maximum value of 431. And calculating to obtain: (difference of maximum and mean) is 44.2 and [ (difference of maximum and mean)/(mean) ] is 11.4%.

4) Comparing with the table 1, the center segregation grade of the cross section of the obtained 1# wire rod is 2 grades.

Example 2:

1) a2 # wire rod (with the diameter of 5.5mm and the concentration of 0.82 percent C) is taken to be inlaid, and metallographic abrasive paper is gradually ground and mechanically polished, so that the section of the wire rod is free from visible scratches, and nitric acid and alcohol corrosion are avoided.

2) The microhardness measurement is carried out on the cross section 1 of the wire rod by means of microhardness (HV10), the measurement is carried out by taking the geometric center of the wire rod as a central point, three perpendicular line segments passing through the geometric center of the cross section of the sample are selected as measurement line segments 2 at the measurement positions, the included angle between the measurement line segments is 60 degrees, the interval between the measurement points is 0.5mm, the distance between the measurement starting point and the measurement ending point and the surface of the wire rod is 1.0mm, the measurement quantity on a single measurement line segment 2 is 8 points, and the total of the three measurement line segments of the cross section of the wire rod is 24 points. The measured microhardness (HV10) of the cross-section of the 2# wire rod is shown in table 3 below:

TABLE 3

Measuring line segment 1	526、551、584、604、612、591、562、531
		Measuring line segment 2	534、558、594、624、618、586、554、541
Measuring line segment 3	538、561、584、621、608、584、567、544

3) Counting the measurement result of microhardness of the cross section of the wire rod: the microhardness has an average value of 574.0 and a maximum value of 624. And calculating to obtain: (difference of maximum and mean) is 50.0 and [ (difference of maximum and mean)/(mean) ] is 8.7%.

4) Comparing with the table 1, the center segregation grade of the cross section of the 2# wire rod is 1 grade.

Example 3:

1) a3 # wire rod (with the diameter of 7.0mm and the concentration of 0.77 percent C) is taken to be inlaid in the cross section, and the cross section of the wire rod is ground and mechanically polished step by using metallographic abrasive paper, has no visible scratches on the cross section of the wire rod, and is not corroded by nitric acid and alcohol.

2) The microhardness measurement is carried out on the cross section 1 of the wire rod by means of microhardness (HV10), the measurement is carried out by taking the geometric center of the wire rod as a central point, two perpendicular line segments passing through the geometric center of the cross section of the sample are selected as measurement line segments 2 at the measurement positions, the included angle between the measurement line segments is 90 degrees, the interval between the measurement points is 0.5mm, the distance between the measurement starting point and the measurement ending point and the surface of the wire rod is 1.0mm, the measurement quantity on a single measurement line segment 2 is 11 points, and the total of the two measurement line segments of the cross section of the wire rod is 22 points. The measured microhardness (HV10) of the cross section of the # 3 wire rod is shown in table 4 below:

TABLE 4

Measuring line segment 1	448、481、502、537、559、582、561、511、474、452、441
		Measuring line segment 2	455、476、498、524、542、565、551、533、512、486、462

3) Counting the measurement result of microhardness of the cross section of the wire rod: microhardness has an average value of 506.9 and a maximum value of 582. And calculating to obtain: (difference of maximum and mean) is 75.1 and [ (difference of maximum and mean)/(mean) ] is 14.8%.

4) Comparing with the table 1, the center segregation grade of the cross section of the 3# wire rod is 3 grades.

The above description is only an embodiment of the present invention, and it should be noted that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the protection scope of the present invention, and the rest that is not described in detail is the prior art.