阅读说明：本技术 一种高碳钢坯加热过程裂纹缺陷氧化脱碳的模拟试验方法 (Simulation test method for oxidation decarburization of crack defects in heating process of high-carbon steel billet ) 是由 郭大勇 高航 王秉喜 潘阳 马立国 张博 于 2021-09-14 设计创作，主要内容包括：本发明涉及一种高碳钢坯加热过程裂纹缺陷氧化脱碳的模拟试验方法,包括金相试样制备过程及金相试样观察过程；所述金相试样制备过程包括如下步骤：1)试样加工；2)缺陷加工；3)试样压缩；4)试样热处理；5)制备金相试样；6)金相试样处理；采用本发明所述方法能够更加准确的模拟高碳钢坯表面裂纹缺陷的氧化脱碳过程,为揭示高碳钢缺陷的遗传规律提供了更为科学有效的方法。(The invention relates to a simulation test method for oxidation decarburization of crack defects in a high-carbon steel billet heating process, which comprises a metallographic specimen preparation process and a metallographic specimen observation process; the preparation process of the metallographic specimen comprises the following steps: 1) processing a sample; 2) processing defects; 3) compressing the sample; 4) carrying out heat treatment on the sample; 5) preparing a metallographic specimen; 6) processing a metallographic sample; the method can more accurately simulate the oxidation decarburization process of the crack defect on the surface of the high-carbon steel billet, and provides a more scientific and effective method for revealing the genetic rule of the high-carbon steel defect.)

1. A simulation test method for oxidation decarburization of crack defects in a high-carbon steel billet heating process is characterized by comprising a metallographic specimen preparation process and a metallographic specimen observation process; the preparation process of the metallographic specimen comprises the following steps:

1) processing a sample; processing a high-carbon steel blank into a cylindrical sample;

2) processing defects; adopting linear cutting to process the defect with the depth of 1-5 mm on the axial middle part of the cylindrical sample and parallel to the upper and lower surfaces;

3) compressing the sample; compressing the sample with the processed defects along the axial direction, wherein the compression amount is 10% -40%, the compression speed is 3-10 mm/min, and the sample is kept for 30-60 s after compression;

4) carrying out heat treatment on the sample; heating at 1000-1150 deg.c for 5-40 min, and air cooling to room temperature;

5) preparing a metallographic specimen; cutting the sample subjected to heat treatment in a direction perpendicular to the length direction of the defect by adopting linear cutting, and then inlaying the cut part into a metallographic sample;

6) processing a metallographic sample; and grinding, polishing and corroding the metallographic specimen.

2. The method for simulating oxidation decarburization of a crack defect during heating of a high carbon steel billet as recited in claim 1, wherein the method is characterized in that

3. The method for simulating oxidation decarburization of a crack defect during heating of a high-carbon steel billet as recited in claim 1, wherein in the step 6), 5% nital is used as the corrosive liquid during the corrosion.

Technical Field

The invention relates to a simulation test method for oxidation and decarburization of crack defects in a high-carbon steel billet heating process.

Background

The high-carbon steel wire rod is widely applied to the fields of automobiles, communication, buildings and the like. Surface defects of high carbon steel billets are an important source of surface defects of high carbon steel wire rods. The oxidation round points, the iron scale and the decarburization on the surface of the billet can be directly transmitted to the wire rod, so that the wire rod is broken in the drawing process, and the quality of metal products is reduced. Therefore, many documents develop the research on the defect forming rule of the wire rod and the billet, and lay the foundation for determining the genetic rule of the defect.

The literature, "research on 45 steel notch evolution behavior under simulated high-temperature oxidation atmosphere" (special steel technology, No. 2 of 2020) introduces the formation characteristic of a defect-oxidation dot in steel, and the test process is as follows: the gap is prefabricated by 45 steel grooving, and the oxidation process of the crack is simulated through different heating temperatures and time. According to observation, the prefabricated gap not only forms various conventional iron oxides in the heating process, but also forms round point-shaped internal oxides and tortoiseshell-shaped oxides on the steel base on the side of the gap. According to the test phenomenon, the point-shaped oxide at the edge of the 45 steel crack is a high-temperature oxidation product, the higher the temperature is, the longer the heating time is, the denser the point-shaped oxide at the edge of the crack is, and the point-shaped internal oxide is difficult to form in a short time below 950 ℃, so that the crack forming stage can be judged according to the forming characteristics of the point-shaped oxide.

The above document uses a wire cutting method to prepare the defects in advance, and then performs a simulation of the formation of oxidized dots. However, in practical production, the billet used for rolling the high carbon steel wire rod is generally subjected to continuous rolling, and the width of the surface defect of the billet is very small and is far smaller than the width of the defect formed after linear cutting. The defects are prefabricated in a linear cutting mode, oxidizing atmosphere enters the defects quickly, oxidation and decarburization are sufficient, and the oxidation and decarburization rules of the actual billet defects in the heating process are difficult to simulate.

In order to overcome the defects of the test method, a preparation method of a sample needs to be redesigned, which is used for simulating the oxidation and decarburization processes of the defect of small surface width of the billet, accurately mastering the oxidation and decarburization rules of the surface defect of the billet in the heating process, and providing a more effective basis for the improvement of the field production process.

Disclosure of Invention

The invention provides a simulation test method for oxidation and decarburization of crack defects in a high-carbon steel billet heating process, which can more accurately simulate the oxidation and decarburization processes of the crack defects on the surface of the high-carbon steel billet and provides a more scientific and effective method for revealing the genetic rule of the high-carbon steel defects.

In order to achieve the purpose, the invention adopts the following technical scheme:

a simulation test method for oxidation decarburization of crack defects in a high-carbon steel billet heating process comprises a metallographic specimen preparation process and a metallographic specimen observation process; the preparation process of the metallographic specimen comprises the following steps:

1) processing a sample; processing a high-carbon steel blank into a cylindrical sample;

2) processing defects; adopting linear cutting to process the defect with the depth of 1-5 mm on the axial middle part of the cylindrical sample and parallel to the upper and lower surfaces;

3) compressing the sample; compressing the sample with the processed defects along the axial direction, wherein the compression amount is 10% -40%, the compression speed is 3-10 mm/min, and the sample is kept for 30-60 s after compression;

4) carrying out heat treatment on the sample; heating at 1000-1150 deg.c for 5-40 min, and air cooling to room temperature;

5) preparing a metallographic specimen; cutting the sample subjected to heat treatment in a direction perpendicular to the length direction of the defect by adopting linear cutting, and then inlaying the cut part into a metallographic sample;

6) processing a metallographic sample; and grinding, polishing and corroding the metallographic specimen.

The size of the cylindrical sample is

In the step 6), 5% nitric acid alcohol is adopted as the corrosive liquid during corrosion.

Compared with the prior art, the invention has the beneficial effects that:

by adopting the method, the defect width of the billet is obviously reduced compared with that of the billet after linear cutting, and the defect width, depth and decarburization condition on the final metallographic specimen are closer to the defect condition of the actual billet; therefore, the oxidation and decarburization process of the crack defects on the surface of the high-carbon steel billet can be simulated more accurately, and a more scientific and effective method is provided for revealing the genetic rule of the high-carbon steel defects.

Drawings

FIG. 1 is a schematic view of a cylindrical test piece according to the present invention.

Detailed Description

The invention relates to a simulation test method for oxidation decarburization of crack defects in a high-carbon steel billet heating process, which comprises a metallographic specimen preparation process and a metallographic specimen observation process; the preparation process of the metallographic specimen comprises the following steps:

1) processing a sample; processing a high-carbon steel blank into a cylindrical sample;

2) processing defects; adopting linear cutting to process a defect (shown in figure 1) with the depth of 1-5 mm on the axial middle part of the cylindrical sample and parallel to the upper and lower surfaces;

3) compressing the sample; compressing the sample with the processed defects along the axial direction (the compression direction is shown in figure 1), wherein the compression amount is 10-40%, the compression speed is 3-10 mm/min, and the sample is kept for 30-60 s after compression;

4) carrying out heat treatment on the sample; heating at 1000-1150 deg.c for 5-40 min, and air cooling to room temperature;

5) preparing a metallographic specimen; cutting the sample after heat treatment by linear cutting in a direction perpendicular to the length direction of the defect (the cutting processing direction is shown in figure 1), and then inlaying the cut part into a metallographic sample;

6) processing a metallographic sample; and grinding, polishing and corroding the metallographic specimen.

The size of the cylindrical sample is

In the step 6), 5% nitric acid alcohol is adopted as the corrosive liquid during corrosion.

The following examples are carried out on the premise of the technical scheme of the invention, and detailed embodiments and specific operation processes are given, but the scope of the invention is not limited to the following examples.

[ examples ] A method for producing a compound

In the embodiment, the simulation test method for the oxidation and decarburization of the crack defects in the heating process of the high-carbon steel billet comprises the following specific processes:

1. processing by using high-carbon steel blankCylindrical sample of (2).

2. As shown in FIG. 1, a defect with a depth of 1-5 mm is machined parallel to the upper and lower surfaces by wire cutting at the axial middle position (height of 1/2) of the cylindrical sample (the specific values of each example are shown in Table 1).

3. And (3) placing the cylindrical sample with the processed defects on a compression tester for axial compression, wherein the compression amount is 10-40%, the compression speed is 3-10 mm/min (the specific numerical values of each embodiment are shown in table 1), and the cylindrical sample is kept for 30-60 s after compression. The width of the surface defects of the compressed sample is reduced.

The reason for controlling the compression parameters is: the sample is easily crushed due to overlarge compression amount of the sample; if the compression amount of the sample is too small, the defect width after compression will be inconsistent with the actual situation. The compression speed of the sample is too fast and defects caused by compression may occur. The process of gradually compressing the surface defects of the continuous casting billet in the continuous rolling process is simulated by adopting the process, so that the simulation test is closer to the actual situation on site. After the width of the surface defect of the sample is reduced, the oxidizing atmosphere is not easy to directly enter the inside of the defect, so that the influence of the oxidizing atmosphere on the oxidation and decarburization of the defect part is weakened.

4. The compressed sample was heat treated. The heating temperature of the heat treatment is 1000-1150 ℃, the heat preservation time is 5-40 min (the specific numerical values of each embodiment are shown in table 1), and the method is used for simulating the oxidation and decarburization processes during the heating of the steel billet. And air cooling to room temperature after the heat preservation is finished.

5. The heat treated sample was cut perpendicular to the length direction of the defect by wire cutting (as shown in FIG. 1). Then inlaying the cut part into a metallographic specimen;

6. and grinding, polishing and corroding the metallographic specimen, wherein the corrosive liquid adopts 5% nitric acid alcohol.

7. And carrying out metallographic observation on the prepared metallographic specimen, and judging the internal oxidation and decarburization conditions of the defects of the high-carbon steel specimen under the condition of the specimen.

TABLE 1

According to the observation, the defect width, the defect depth and the decarburization condition of the billet are closer to the defect condition of the actual billet because the defect width on the billet is obviously reduced by adopting the embodiment of the method. The comparative example only adopts a linear cutting method to prepare the defects, and has larger difference with the actual situation no matter from the aspects of width, appearance and oxidation and decarburization conditions of the defects. The method provided by the invention is closer to the actual situation on site, and provides a powerful basis for researching the oxidation and decarburization of the billet heating on the surface defects.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered to be within the technical scope of the present invention, and the technical solutions and the inventive concepts thereof according to the present invention should be equivalent or changed within the scope of the present invention.