KR100992696B1 - Method for analyzing boron distribution of alloy steel - Google Patents

Abstract

The present invention relates to a method for analyzing the distribution of boron (B) elements contained in the boron alloy steel, the process of attaching a film-type detector on the specimen inspection surface after the sampling and mounting of the specimen, processing the inspection surface, The present invention relates to a method for analyzing the distribution of boron elements in the process of irradiating, washing, drying, and observing with a light microscope on a film detector separated from a specimen after neutron irradiation. In the present invention, by providing the standardized optimal analysis method as described above, it is possible to minimize the analysis error by excluding the difference of the method according to the tester's experience, skill difference, it is possible to improve the reliability of the test.

Boron, distribution, neutron irradiation, film detector, optical microscope

Description

Method for analyzing boron distribution of alloy steel

The present invention relates to a method of analyzing boron (B) distribution of boron alloy steel, which can minimize an error of analysis by excluding a difference of a method according to a tester's experience and skill level, and improves the reliability of analysis. It relates to an analysis method.

In general, gearboxes for automobile transmissions include processes such as material → hot or cold forging → cooling (air cooling or furnace cooling) → annealing or normalizing → processing (shaving & hobbing) → carburizing heat treatment → post-processing (polishing, honing) It is manufactured after.

As an alloy steel material for manufacturing a gear for transmission, it is an optimal alloy steel material having excellent forging property and workability, suitable price, and excellent mechanical properties (for example, fatigue characteristics and impact characteristics) after heat treatment.

Currently, chromium-molybdenum (Cr-Mo) alloy steel is widely used as an alloy steel material of a gear for transmission, and such chromium-molybdenum alloy steel (hereinafter referred to as SCM steel) is functional in automobiles such as a driving device, a transmission, and a steering device. It is widely used as a material for parts.

The SCM steel is subjected to heat treatment for strength improvement and grain refinement, and is quenched and annealed according to the required mechanical properties by heating the SCM steel to a solidifying treatment temperature of more than transformation points (AC3, AC1, Acm). Annealing, normalizing, tempering, etc.

On the other hand, when boron (B) element is added to carbon steel as boron steel in the range of 10 to 50 PPM (0.001 to 0.005 wt%), mechanical properties similar to those of chromium alloy steel (SCr) and chromium-molybdenum alloy steel (SCM steel) can be obtained.

In particular, even when a small amount of boron in an amount of 10 to 50 ppm (0.001 to 0.005% by weight) is inexpensive as a characteristic of boron steel, the hardenability can be improved to about 10 mm during the heat treatment (hardness improvement). And toughness and wear resistance are improved by the precipitation strengthening effect due to grain boundary precipitation. Due to these characteristics, the application of boron steel to driving parts of automobiles is gradually increasing.

In the case of boron steel, the above-mentioned heat treatment is performed in order to satisfy the required mechanical properties.Boron is precipitated in the grains and grain boundaries of the boron steel by the heat treatment temperature and the retention time, and is distributed in the boron steel. Among the many factors that dominate, the most important role is the distribution of boron.

That is, boron distribution not only determines the strength and toughness of boron steel but also greatly influences chemical and physical properties such as grain embrittlement, reduction of cracks and thermal deformation during heat treatment, improvement of stress resistance and corrosion cracking properties.

Therefore, in order to verify the heat treatment requirements for the boron steel and to confirm the chemical composition, it is necessary to analyze the boron distribution precisely, and above all, to solve the quality problems of the heat treated boron steel generated in the durability and the field. Accurate analysis of boron distribution is essential.

If boron is uniformly distributed in the boron steel, mechanical properties such as strength and toughness may be satisfied. Otherwise, many mechanical properties such as strength, toughness, and stress resistance decrease.

In the prior art, there was no standardized analysis method for analyzing the boron distribution of boron steel, but only the amount of boron added was analyzed by analyzing boron elements of boron steel with a device.

Therefore, it is necessary to establish and systemize the boron distribution analysis method of boron alloy steel and the method of manufacturing specimens for boron distribution analysis at each step.

Therefore, the present invention has been invented to solve the above problems, it is possible to minimize the analysis error by eliminating the difference of the method according to the tester's experience, skill differences, boron alloy steel that can improve the reliability of the analysis The purpose of this paper is to provide a method for analyzing the distribution of boron.

In order to achieve the above object, the present invention, in the method for analyzing the distribution of boron elements contained in the boron steel, (a) cutting the specimen from the material to be measured using a cutting machine, and (b ) Mounting the collected specimens to resin to make the size and shape easy for subsequent processing and processing; (c) polishing the resin and the specimen using a polishing machine to obtain the surface-treated specimen inspection surface; d) attaching the film detector to the surface-treated specimen inspection surface and mounting the sample holder to the sample holder; (e) mounting the sample holder equipped with the specimen and film detector to the holder fixing case, and (f) the sample. Irradiating a neutron to the film detector attached to the specimen of the holder, (g) detaching the sample holder to peel off the film detector from the specimen, and then developing; and (h) washing and cleaning the developed film detector.Johann Du characterized in that it comprises the step of observation using an optical microscope.

In a preferred embodiment, the step (b) comprises the step of compressing and molding at the same time by applying heat and then wrapped around the specimen taken in the step (a) with a resin in the form of a mounting press equipment It features.

In addition, the resin in the form of a powder is used as a black bakelite powder, wherein the black bakelite powder in the heating press 10 ~ 15 minutes, heating temperature 180 ℃, pressure 40kN, cooling time 7 ~ 10 minutes It characterized in that the molding.

In addition, while irradiating the thermal neutron in the step (f), the neutron flux density Irradiation is preferably performed under conditions of 1 × 10 ⁹ n / cm 2s or more, a Cd ratio of 104 or more, and an exposure time of 4 hours.

In addition, after removing the specimen from the sample holder in the step (g), the film-type detector attached to the test surface of the specimen is separated, and the film-type detector is developed by a method of dipping and soaking in aqueous sodium hydroxide solution. At this time, the film-type detector is preferably dipped in an aqueous solution of sodium hydroxide at a concentration of 2.2N and maintained at 50 ° C. for 12 minutes.

In addition, the step (h) is characterized in that for washing the developed film-type detector in distilled water and hot air drying to observe the corroded position with an optical microscope, wherein the developed film-type detector in distilled water for 2 to 3 minutes After washing, hot air drying is preferably performed at a temperature of 40 to 50 ° C. for 3 to 5 minutes.

In the method of analyzing the boron distribution of boron alloy steel according to the present invention, a film-type detector is attached to an inspection surface of a processed specimen after collecting, mounting and inspecting the specimen, and attaching the film detector to the sample holder, and fixing the sample holder equipped with the specimen. After fixing to the case and irradiating the neutron, the film-type detector is separated from the specimen, developed and washed.Then, after improvement, the optical microscope is used to observe traces of nuclear reaction between the neutron and the specimen in the film-type detector. Therefore, the measurement error can be minimized and the reliability of the test can be improved.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

The present invention relates to a method for analyzing the distribution of boron (B) elements contained in a steel material, and after collecting and mounting a specimen, processing a test surface, and attaching a film detector to the test surface of the specimen, The present invention relates to a method for analyzing the distribution of boron elements in the process of irradiating, washing, drying, and observing with a light microscope on a film detector separated from a specimen after neutron irradiation. In the present invention, by providing the standardized optimal analysis method as described above, it is possible to minimize the analysis error by excluding the difference of the method according to the tester's experience, skill difference, it is possible to improve the reliability of the test.

Hereinafter, the specimen collection and pretreatment method and analysis method according to the present invention will be described in more detail step by step as follows. 1 is a flowchart illustrating a boron distribution analysis process according to the present invention, and may be classified into a specimen processing step and a distribution analysis step.

1) Specimen Collection Step

First, the boron steel material to be measured is cut using a cutting machine to obtain a specimen having a suitable shape and size from the boron steel material.

At this time, the cutting wheel of the cutting machine (cutting wheel) uses a material made of zirconium (Zr) as a material.

In addition, the cutting speed of the cutting wheel and the feed rate of the specimen is maintained at 1800 ~ 2500 rpm, 0.5 ~ 1.5 mm / min, respectively, and if the rotational speed of the cutting wheel and the feed rate of the specimen faster than the above range, The problem of oxide film formation may occur as well as tissue deformation of the specimen, which is not preferable.

In addition, the size of the specimen should be 5 to 20 mm in width, 10 to 30 mm in length, and 10 to 20 mm in thickness. desirable.

Here, if the size of the specimen is large, the reliability of the analysis result is improved, and if the size of the specimen is small, the representativeness is reduced and the reliability of the analysis result is reduced.

2) Psalms Mounting  step

Next, the specimen collected in the previous specimen collection step has a small size, so that the specimen is not easy to be mounted during subsequent processing and processing such as inspection surface processing, so that the specimen may be mounted on resin for further processing and Steps are made to size and shape that are easy to process.

This step involves molding the specimen (1) into a resin (2), which is powdered around the specimen (1) taken from the boron steel using a mounting press equipment. After wrapping with a resin (2) of the form is a process of molding by applying heat and at the same time.

In this step, black bakelite powder may be used as the powder resin, in which the heating time in the mounting press equipment is 10 to 15 minutes, the heating temperature is 180 ° C., the pressing pressure is 40 kN, and the cooling time. Set it to 7 to 10 minutes.

In addition, as described above, it is preferable that the entire size of the specimen mounted on the resin is 45 to 50 mm in diameter and 20 to 35 mm in height, and if it is larger than this, the time required for the subsequent polishing step is unnecessarily long. Not good

3) Inspection Surface Processing Step of Specimen

Next, as a step of obtaining the test surface of the specimen by grinding the resin and the specimen, using a polishing machine, using a sand paper (line paper) and the process of pre-processing, the end finishing process of the polishing cloth ( Polishing cloths) are used to classify the post-processing process.

In the process of sand paper processing, the sanding speed of # 200 → # 400 → # 600 → # 800 → # 1000 is processed step by step with the rotation speed of the polishing machine as 200 ~ 250 rpm, and the processing time is 5 ~ It is carried out for 10 minutes.

In addition, in the polishing cloth processing, a diamond abrasive is used. In this case, the diamond abrasive is subjected to stepwise machining in the order of 6 μm → 3 μm → 1 μm.

Here, in order to obtain the optimum processing surface, it is preferable to use the abrasive cloth separately according to the abrasive grain size (the same abrasive cloth is not used continuously), and the machining time is performed at 5 to 10 minutes for each step.

2 is a photograph showing a state in which the test surface is processed after mounting the specimen by molding with black bakelite powder resin.

4) Specimen Cleaning and Drying Steps

Next, the specimen is placed in a beaker containing a volatile organic solvent in order to remove foreign substances formed at the grain boundary of the specimen, and then washed for a predetermined time using an ultrasonic cleaner.

Methanol, ethanol or ether may be used as the volatile organic solvent.

In addition, it is preferable to clean for 8 to 12 minutes by using an ultrasonic cleaner. If the cleaning time is exceeded, the preparation time of the specimen is long. have.

When the cleaning is completed to some degree, the specimen should be removed.If the specimen is removed while the ultrasonic cleaner is stopped, foreign matters may be attached to the specimen. Therefore, it is preferable to remove the specimen from the volatile organic solvent while the ultrasonic cleaner is in operation. Do.

As described above, in the present invention, by completely removing the impurities present in the test surface of the specimen by using an ultrasonic cleaner, it is possible to increase the cleanliness of the specimen, thereby minimizing the occurrence of errors in the analysis due to the impurities.

Thereafter, the washed specimens are dried at a temperature of 60 to 80 ° C. in a blow dryer to completely remove the volatile organic solvent.

Drying of the specimen should be done with caution to ensure that the volatile organic solvent is completely removed to prevent staining on the surface.

5) Attach the film detector and attach the sample holder

First, a film detector (SSNTD: Kodak State Film CN85) is attached to the inspection surface of the processed specimen, and a specimen (1) (molded with resin 2) to which the film is attached is attached. It is attached to the sample holder 4 shown in FIGS.

The sample holder 4 is manufactured in the form of a cylindrical case, which is divided into an upper case 6 having an inspection hole 6a formed on an upper surface thereof, and a lower case 6 assembled with the upper case 6 ( 3 and 4).

When the specimen is mounted, the specimen 3 is molded with the resin 2 while the spring 7 is inserted into the lower case 5 and the film detector 3 is attached thereto. Then, the upper case 6 ) Is assembled by closing from above.

At this time, since the inspection hole 6a is formed in the upper surface of the upper case 6, the film-type detector 3 attached to the inspection surface of the specimen 1 in the state of being mounted on the resin 2 is the inspection hole 6a. Will be exposed through (see FIG. 5).

6) Sample holder fixing step

In the state where the specimen is mounted on the sample holder, the sample holder 4 is inserted into the mounting groove 11 of the holder fixing case 10 and fixed. 6 is a view illustrating a holder fixing case, wherein the holder fixing case 10 is manufactured in a structure in which a plurality of mounting grooves 11 are formed at an upper portion thereof, and a sample holder 4 is disposed in each of the mounting grooves 11. It is inserted and fixed.

7) Neutron irradiation stage

A neutron is one of the particles that together with the proton form the nucleus. The neutron's greatest characteristic is that it is electrically neutral and its magnetic moment and mass are about 1840 times larger than the former. In addition, neutrons are mass particles and also have wave characteristics. This is called the DeBrow wavelength.

Neutrons of various energy bands are classified according to their energy range. Usually, neutrons are mainly used in four areas, and types can be classified according to the amount of energy.

Neutrons with energy above 100 ev are called fast neutrons, which have very small reaction cross sections and have good penetration, but are not easy to distinguish different objects.

In addition, a neutron having an energy of 0.5 to 100 ev is called an epithermal neutron, and a neutron having an energy of 0.01 to 0.5 ev is called a thermal nuntron. Thermal neutrons are the energy domain of neutrons, which are mainly used in a wide range, and because they have a large reaction cross section, they are most suitable for analyzing the distribution of boron in boron steel.

Finally, neutrons with energy below 0.01 ev are called cold neutrons, and because of their large reaction area, it is easy to distinguish between different objects, but it is not easy to produce cold neutrons. Is the most produced and used.

In the present invention, the sample holder is fixed to the holder fixing case and irradiated with a thermal neutron to the film-type detector (attached to the test surface of the test piece exposed through the test hole) through the test hole of the upper case boron of the test piece Induces nuclear reactions of elements and neutrons.

Thermal neutron irradiation is carried out under the following conditions. Neutron Flux Density, Irradiation Condition of Thermal Neutrons for Optimal Neutron Distribution Analysis Neutrons are irradiated to the specimen under conditions of 1 × 10 ⁹ n / cm 2s or more, a Cd ratio of 104 or more, and an exposure time of 4 hours. Here, if the neutron flux density is low, the probability of nuclear reaction with boron (B) element is low, so accurate analysis is impossible.

In addition, the cadmium ratio (Cd ratio) represents the quality of the thermal neutrons, it is an index of the production of high quality thermal neutrons by shielding other neutrons with a cadmium filter (Cd filter).

The irradiation time of the thermal neutrons was estimated to be about 4 hours for the most efficient analysis of the boron distribution. If the time is too short, the nuclear reaction between the neutron and the specimen is not sufficient, so that it is difficult to measure the exact boron distribution and the time is too long. Longer test times are less effective, so it is most desirable to investigate for 4 hours.

When irradiating thermal neutrons to the boron-containing boron steel material, a nuclear reaction occurs as shown in FIG. 7 and the following reaction equation. Particles (α, Li) generated in the reaction closely adhere to the test surface of the specimen (1). A trace is left on the film detector (SSNTD) 3 thus made.

¹⁰ B + ¹ n → ⁴ α + ⁷ Li + e

8) Film-type detector separation and development step

The upper case 6 of the sample holder 4 is separated from the lower case 5 to remove the specimen from the sample holder, and then the film detector 3 attached to the test surface of the specimen is separated.

Thereafter, as shown in the accompanying FIG. 8, the process of developing is carried out. That is, the container 12 containing water is placed on a heating plate (not shown), and then the temperature of the water is maintained at a temperature of 50 ° C. using the heating plate. Then, the container 13 containing the aqueous sodium hydroxide solution is placed in water, and the film-type detector 3 is immersed in the aqueous sodium hydroxide solution and developed.

As described above, development is carried out using a 2.2 N sodium hydroxide solution in a bath-shaped structure, and the etching time is 12 minutes while the temperature of the sodium hydroxide solution is maintained at 50 ° C. by a bath.

9) Drying and distribution of film dryer

The film detector developed as described above was washed in distilled water for about 2 to 3 minutes, and then dried in a hot air drying oven (Dry Oven) at a temperature of 40 to 50 ° C. for 3 to 5 minutes, and then corroded with an optical microscope ( Boron distribution) is observed at a ratio of 100 times (x100).

9 is a photograph showing the distribution of boron at a ratio of 100 times.

In this way, it is possible to analyze the boron distribution of the boron steel by the above-described method, and according to the present invention, more accurate measurement is possible by systematically and standardizing the boron distribution analysis method, and the analysis data according to the boron distribution in the boron steel It can be used as a basic data for the study on the change of properties, and it can contribute much to the ointment of the behavior of boron element in the future heat treatment.

1 is a procedure showing a boron distribution analysis process according to the present invention,

Figure 2 is a photograph showing a state after processing the test surface after mounting the specimen by molding with a black bakelite powder resin in the present invention,

3 is a cross-sectional view showing a specimen and a sample holder in the present invention,

Figure 4 is a photograph showing the configuration of a sample holder in the present invention,

Figure 5 is a photograph showing a state in which the specimen is mounted on the sample holder in the present invention,

6 is a view showing a holder fixing case to which the sample holder is fixed in the present invention,

7 is a view showing that the nuclear reaction occurs as the neutron is irradiated on the specimen attached to the film-type detector in the present invention,

8 is a view showing a developing method of a film type detector in the present invention,

Figure 9 is a photograph showing the distribution of boron in the ratio of 100 times.

<Explanation of symbols for the main parts of the drawings>

1: Psalm 2: Resin

3: film type detector 4: sample holder

5: lower case 6: upper case

6a: inspection hole

Claims (9)

In the method of analyzing the distribution of boron elements contained in boron steel, (a) cutting and sampling the specimen from the material to be measured using a cutting machine, (b) mounting the collected specimen on a resin to make the size and shape easy for subsequent processing and processing, and (c) Polishing the resin and the specimen using a polishing machine to obtain a surface treated specimen inspection surface; (d) attaching a film detector to the surface treated specimen inspection surface and mounting the sample detector on the sample holder; Mounting a sample holder equipped with a film detector to a holder fixing case; (f) irradiating a neutron to a film detector attached to a specimen of the sample holder; and (g) removing the sample holder to remove the film detector. Peeling off from the specimen and developing; and (h) washing and drying the developed film type detector and observing by using an optical microscope. A method analysis. The method according to claim 1, In step (b), Method for analyzing the boron distribution of boron alloy steel, comprising the step of compressing and molding at the same time by applying heat and wrapping the surroundings of the specimen collected in the step (a) with a resin in the form of a mounting press equipment. The method according to claim 2, The method of analyzing the boron distribution of boron alloy steel, characterized in that the black bakelite powder is used as the powder form resin. The method according to claim 3, Method for analyzing the boron distribution of boron alloy steel, characterized in that the black bakelite powder is molded by mounting time 10-15 minutes, heating temperature 180 ℃, pressure 40kN, cooling time 7-10 minutes in the mounting press equipment. The method according to claim 1, Investigate the thermal neutron in the step (f), but the neutron flux density A method of analyzing the boron distribution of boron alloy steel, characterized in that the irradiation is carried out under conditions of 1 × 10 ⁹ n / cm 2s or more, a Cd ratio of 104 or more, and an exposure time of 4 hours. The method according to claim 1, Taking out the specimen from the sample holder in the step (g), separating the film detector attached to the test surface of the specimen, and developing the boron alloy steel by dipping the film detector in an aqueous sodium hydroxide solution. Method of analysis of boron distribution. The method according to claim 6, Method for analyzing the boron distribution of boron alloy steel, characterized in that the film-type detector is immersed in an aqueous solution of sodium hydroxide at a concentration of 2.2N concentration and developed for 12 minutes while maintaining the bath temperature at 50 ℃. The method according to claim 1, (H) step, Method for analyzing the boron distribution of the boron alloy steel, characterized in that to wash the developed film-type detector in distilled water and hot air dried to observe the corroded position with an optical microscope. The method according to claim 1 or 8, Method for analyzing the boron distribution of the boron alloy steel, characterized in that the hot-air drying for 3 to 5 minutes at a temperature of 40 to 50 ℃ after washing the film-type detector developed in step (h) for 2 to 3 minutes.

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