JP2868681B2 - High resolution steel segregation state, solidification structure transfer method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for clearly detecting the segregation state and solidification structure of steel over a wide inspection area, and recording and storing them at high resolution.

[0002]

2. Description of the Related Art Conventionally, sulfur printing has been widely used as a simple and economical method for detecting the segregation state and solidification structure of steel. In this method, the segregation state and solidification structure are recorded and stored on sulfur print paper. Is done.

In the method of detecting and transferring the segregation state of a specific element such as the sulfur print, the resolution is lower than that in the case of observing the structure and segregation by corrosion treatment, and a print of sufficient quality can be obtained depending on the sample. May not be. For example, when a sulfur print is performed on a sample having porosity, white spots appear at the site due to gas generated from the porosity, and a high-quality print cannot be obtained. In a method of detecting the segregation state of a specific element such as sulfur print, when the content of the element is low or when the element and a compound are formed with another element, the segregation state or solidification structure is reduced. There was a disadvantage that it could not be detected.

In addition, a method of taking a picture in a state in which the polished surface is corroded with a corrosive solution that reveals the segregation state or solidification structure of steel, for example, hydrochloric acid or an overhoffer solution to reveal the segregation state or solidification structure, is also common. However, in this method, when observing a wide range of segregation state and solidification structure, the target range is restricted when trying to maintain the resolution, and conversely, when the target range is widened, the resolution decreases. There's a problem.

As a printing method for observing a solidification structure and segregation other than sulfur printing, an etch print (Kitamura et al .: Iron and Steel, 68 (1982), S217) is known.
A method has been developed in which a polishing powder is filled in a corrosion hole, and the powder is transferred to a tape to copy a solidified structure and segregation. Tokunosho 64
No. 2212 discloses an invention relating to this method.
In this method, the resolution is greatly improved compared to the sulfur printing method, and the solidification structure and segregation can be clearly detected and recorded, but in some cases, the segregation state and solidification structure of the transferred steel due to discoloration of the print may be unclear. In this method, the polishing powder is filled into the corrosion holes by finish polishing, and the polishing powder is sufficiently generated for the method of transferring the segregated state and the solidified structure to the tape, and a highly viscous material such as petrolatum applied before polishing is used. It is necessary to remove the liquid organic matter except for the corrosion holes, and the polishing operation requires a considerable amount of time and labor, and also has a high work load.

[0006]

SUMMARY OF THE INVENTION In the present invention, when detecting and recording the segregation state and solidification structure of steel as described above, the target range cannot be sufficiently detected by the conventional method, and the resolution is low or the resolution is to be maintained. It is intended to solve the problem that the detection image becomes unclear due to the deterioration of the print, the detection and transfer require a lot of time and labor, and the work load is high.

[0007]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and is characterized by the fact that the surface to be inspected of a polished metal sample is subjected to a strong acidic corrosion which appears in a segregated state. After corrosion using a liquid, the surface was immersed in an alkaline solution, washed with water, and dried.
m, and then applying an organic high-viscosity liquid substance mixed with black powder of less than m to the surface, wiping it off, and further polishing the surface using a fine-grained abrasive paper. The transparent thin film that is in close contact with the surface is peeled off, and this transparent thin film is attached to a mount or base plate to easily detect a segregated state with high resolution, solidified structure, and transfer over a wide range of inspection surfaces. This is a method that can be recorded.

[0008]

The reason why the corrosion, polishing, and transfer methods described in the above section are adopted in the present invention will be described. A hot hydrochloric acid-based corrosive solution or a picric acid-based corrosive solution can be considered as a strongly acidic corrosive solution that shows a segregation state on the surface to be inspected of a polished metal sample. The etchant is better.

The reason for immersing the sample surface in an alkaline solution after washing with a strongly acidic etchant, washing with water, and drying is that if the strongly acidic etchant remains on the sample surface, it is corroded in the subsequent polishing step by the etchant. The abrasive powder filled in the holes is oxidized, which causes discoloration of the print and makes the appearance of segregation and solidified structure unclear. Therefore, it is necessary to control the pH of the sample surface to 7 or more by immersing it in an alkaline solution. Further, the subsequent washing with water and drying are performed to remove the alkali solution to some extent to prevent the segregation state and the deterioration of the transparent thin film that transfers the solidified structure.

[0010] As shown in Table 1 below, in the conventional method of not immersing in an alkaline solution, 25%
Had to be reprinted, but the method reduced the percentage of reprints to 0%. In the case of reprinting, it was necessary to start over again from corrosion, so the time loss due to reprinting was greatly reduced by applying this method.

After the above-mentioned corrosion treatment, an organic high-viscosity liquid substance mixed with black powder having a particle size of 20 μm or less is applied to the surface, wiped off, and the surface is polished using a fine-grain abrasive paper. The reason will be described. The principle of the appearance of the segregation state and solidification structure of the present invention is that the corroded concave portion is filled with a high-viscosity liquid organic substance mixed with black powder, and the polishing powder generated by the subsequent polishing is filled in the concave portion, and the concave portion is formed. A high-viscosity liquid organic substance mixed with abrasive powder and black powder is removed from other parts, and a transparent thin film having an adhesive glued to one surface is closely adhered to the surface and peeled off. This is because a mixture of viscous liquid organic substances is transferred to a thin film. Therefore, the point of the present method is how to efficiently fill the corrosive holes with the highly viscous liquid organic matter mixed with the abrasive powder or the black powder and remove them from the portions other than the corrosive holes.

In the step of applying an organic high-viscosity liquid substance mixed with black powder having a particle size of 20 μm or less to the surface and then wiping the surface, the use of the organic high-viscosity liquid substance is as follows.
This is for assisting the polishing powder to remain in the corrosion hole. If not used, the polishing powder remaining in the corrosion hole is insufficient, and the segregation state and the solidified structure do not appear clearly.

The reason that black powder having a particle size of 20 μm or less is mixed into an organic high-viscosity liquid substance is that the amount of abrasive powder required to clearly show segregation and solidified structure by mixing the black powder is considered. Can be greatly reduced as compared with the case where no is mixed, and the working time and load of polishing can be greatly reduced. In addition, by using a material mixed with an organic substance in advance, the efficiency of filling the corrosion holes is improved, which also contributes to a reduction in polishing time and a reduction in polishing work load. Further, in order to efficiently fill the corrosion holes, the particle size of the black powder used is preferably set to 20 μm or less. The reason why the mixture is applied to the surface of the sample and then wiped off is that if the mixture is excessively attached, it takes time to remove the mixture from portions other than the corrosion holes. For black powder,
Although the type is not limited, for example, magnetic powder having a uniform particle size distribution is suitable for use.

The polishing of the surface is performed using a disc-shaped abrasive paper having a number of 500 or more and 2000 or less using a polishing paper of 10 rpm or more and 10,000 rp or less.
It is preferable to perform polishing by giving an eccentric rotation of not more than m. 50
Polishing with abrasive paper coarser than No. 0 or 500-20
Even in the case of using abrasive paper of No. 00, if it is polished at 10,000 rpm or more, unevenness caused by corrosion disappears, segregation state and solidified structure do not appear clearly, and it is polished with abrasive paper finer than No. 2000. 1 using abrasive paper
When the polishing is performed at a speed of 0 rpm or less, the generation amount of the polishing powder is small, and a considerable amount of time is required for filling the polishing powder and removing the highly viscous liquid organic substance mixed with the polishing powder and the black powder from other than the corrosion holes.

The reason for giving eccentric rotation to the disc-shaped abrasive paper is as follows.
If the rotation is not eccentric, the polishing is always performed at the same location on the abrasive paper, so the polishing conditions and removal of the liquid organic matter tend to be uneven due to the effects of the abrasive, etc. The position and the contact state of the sample and the polishing paper are changed, so that it is hard to be affected by the peeling of the abrasive and the like, and more uniform and efficient polishing and removal of organic substances can be performed.

The segregation state and solidified structure revealed by the above-mentioned finish polishing are peeled off after a transparent thin film having an adhesive adhered to one surface thereof is brought into close contact with the surface, and the transparent thin film is mounted on a mount or a base plate. The film is transferred by sticking. The thin film is suitable for the purpose of the present invention as long as it is a transparent thin film having one surface coated with an adhesive. In addition, as for the mount or the base plate on which the transparent thin film is to be attached, preferably, a white one is well observed in a segregation state and a solidified structure.

[0017]

EXAMPLES Table 1 shows the results of applying this method to the evaluation of the segregation state and solidification structure of continuous cast slabs of steel in comparison with the results of applying other methods. In the present example, when alkali treatment was performed using a picric acid-based etching solution, the sample was immersed in an aqueous solution of calcium hydroxide for 30 minutes. The inspected surface is 162
mm × 200 mm. The conventional method is a method disclosed in Japanese Patent Publication No. 64-2122. The comparative method is based on the method of the present invention, without alkali treatment, or with a black powder having a particle size of more than 20 μm.

As is clear from Table 1, in the print obtained by the method of the present invention, the segregation state and the solidified structure are clear, no discoloration occurs, and the work time required for the print is greatly reduced. FIG. 1 shows the segregation and solidification structure at the center of the continuous cast slab obtained by applying the method of the present invention. Segregated and solidified structures are clearly transferred.

[0019]

[Table 1]

[0020]

According to the method of the present invention, the detection ability is greatly improved over the conventional method easily and without a large workload.
It can detect and record the segregation state and solidification structure of a wide range of steels with high resolution and contribute to speeding up the quality control of continuous cast slabs and developing technology for improving segregation, and its industrial significance is great.

[Brief description of the drawings]

FIG. 1 shows the segregation and solidification structure at the center of a continuous cast slab transferred to a print by the method of the present invention.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Akio Takahashi 12 Nakamachi, Muroran-shi, Hokkaido Nippon Steel Corporation Muroran Works (56) References JP-A-58-2657 (JP, A) (58) Surveyed field (Int.Cl. ⁶ , DB name) G01N 1/28 G01N 33/20

Claims (1)

(57) [Claims] 1. A surface to be inspected of a polished metal sample,
After corroding using a strong acidic corrosive liquid that shows a segregation state,
The surface is immersed in an alkaline solution, washed with water, dried, and thereafter, an organic high-viscosity liquid substance mixed with black powder having a particle size of 20 μm or less is applied to the surface, and then the surface is wiped off. After polishing using a fine-grained abrasive paper, a transparent thin film having an adhesive glued to one surface is brought into close contact with the surface and then peeled off, and the transparent thin film is attached to a mount or a base plate. The method of transferring the segregation state and solidification structure of steel with high resolution.