JPS58225353A - Method for rapidly inspecting central segregation of continuously cast material - Google Patents

Abstract

PURPOSE:To inspect the central segregation of a continuously cast material simply and rapidly on the scene without necessitating the cutting of a special test pieces, by directly coating the cross area of the continuously cast material with a solvent solution prepared by dissolving a non-oxidative acid in a non- oxidative solvent low in vapor pressure to precipitate carbon. CONSTITUTION:When a continuously cast material 1 is cooled to an appropriate temp., for example, 100-150 deg.C, a surface 2 to be inspected is conditioned by a grinding means 3. A place to be inspected is directly coated with a solvent prepared by dissolving a non-oxidative acid high in iron dissolving power, having a high b.p. and low in vapor pressure such as sulfuric acid or phosphoric acid in a non-oxidative solvent well dissolving a reaction product such as polyhydric alcohols, having a high b.p. and low in vapor pressure. When the solvent 4 is coated by a spray means 5, the dissolution of steel on the surface to be inspected and the decomposition of carbon or carbide are simultaneously and amorphous carbon 8 is precipitated. The segregation of this precipitated carbon in recorded by a visual observing camera 6 or the fabrication of carbon print due to a sticky tape 7 to inspect central segregation.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for rapidly inspecting continuous cast material for central segregation.

Central segregation of continuous cast pieces of steel is a cause of various material deterioration in steel materials. There has been a growing need to inspect continuously cast materials to determine the degree of central segregation.

Conventionally, chemical methods such as sulfur print method and hydrochloric acid macro method, and physical methods using K such as electron beam analysis are known as methods for inspecting central segregation of steel materials. However, in these inspection methods, it is necessary to wait for the manufactured casting material to cool sufficiently before cutting out the test piece, surface processing the cut out test piece, and transporting it to the inspection room, which takes a long time. Generally, it lasts about 3 hours. Furthermore, about 1 to 2 hours are required for inspection after processing the test piece. Therefore, the work is complicated, and the efficiency of inspecting central segregation of continuously cast material is very poor.

1. Among chemical methods, the hydrochloric acid macro method involves immersing the test piece in an equal mixture of water and earth acid, which generates a large amount of harmful acid vapor and pollutes the working environment. To avoid contamination and avoid this! This had the disadvantage of requiring a room with separate heating and exhaust equipment for each row. In addition, since the sulfur print method is a method for investigating the segregation of sulfur in steel, it has the disadvantage that it cannot detect the degree of segregation at all for extremely low sulfur copper, which has been produced in large quantities in recent years.
These methods cannot meet the demand for quickly and reliably inspecting commercial-grade steel with low central segregation and quickly turning it into a product.

The present invention was devised through repeated research in view of the above-mentioned circumstances, and its purpose is to directly perform on-site testing without the need to cut out special specimens or transport them to a laboratory. It is an object of the present invention to provide a method for inspecting the center segregation of a continuous cast piece by which the center segregation of a continuous cast piece can be inserted extremely easily, quickly and accurately.

In order to achieve this objective, the present invention precipitates carbon by directly coating the cross section of continuously cast material with a special solution containing a non-oxidizing acid dissolved in a solvent. The central segregation is made clearly visible and recorded using an appropriate method.

The present invention will be specifically described below based on Examples.

Figures 1 and 2 schematically show the rapid central segregation inspection method for continuously cast materials according to the present invention, where 1 is a continuous cast material that has been cut into predetermined dimensions and is in the cooling process. In the present invention, when the continuously cast material 1 is cooled to an appropriate temperature, the whole or at least the middle of the surface 2 to be inspected of the continuous cast piece 1 shown in FIG.
) The central segregation occurrence area is adjusted by the polishing means 3.

In the present invention, since it is only necessary to confirm the uneven distribution of carbon, there is no need for advanced surface processing in Test J1, which was performed in conventional inspection methods, and at most grinding with a grinder and polishing with an 80+ polishing cloth is sufficient. It is.

After polishing the surface 2 to be tested of the continuously cast material 1 in this way, the
As shown in I)), a coating 4 containing a non-oxidizing acid dissolved in a solvent is directly applied to the inspection portion of the surface 2 to be inspected.

Here, the non-oxidizing acid should be one with physical properties that have a strong ability to dissolve iron, a high boiling point, and a low vapor ratio. Typical examples include sulfuric acid and cynic acid. .

In addition, a suitable solvent is one that can dissolve the reaction product of non-oxidizing acid and iron well, is non-oxidizing, has a high boiling point, and has low vapor pressure.A typical example of this is ethylene glycol. Examples include polyhydric alcohols such as Dissolution in water is not preferable because it will be dispersed during application.

The volumes of the non-oxidizing acid and the solvent may be appropriately set depending on the reaction rate, the material of the continuously cast material, the temperature, etc.

As for the method of applying the coating to the surface 2 to be inspected on the side 4, it is generally preferable to use a spraying method such as a spray nozzle or a spray gun 5, since it is necessary to apply the coating quickly and uniformly to the inspection area. However, in this case, the agent does not necessarily need to be made into fine particles like mist, and may be sprayed in the form of droplets.The medium for spraying may be air, but heated air or heated gas may be used for spraying. It's okay.

In this way, when the coating material 4 is applied to the surface to be inspected 2, the non-oxidizing acid in the preparation simultaneously dissolves the steel on the surface to be inspected and decomposes the carbon and carbides in the steel. Amorphous carbon 8 is precipitated. This reaction is rapid, and central segregation immediately and clearly appears from the uneven distribution of precipitated carbon. In this case, since the method of the present invention uses an acid with a low vapor pressure for melting steel 1, continuous casting #
Even if the temperature of l is relatively high, a large amount of acid vapor is not generated as seen in the hydrochloric acid macro method, and therefore there is no fear of contamination of the working environment. Furthermore, there is no need for a special locally ventilated room for inspection.

- After the central segregation appears as shown in (1), the non-oxidizing acid is washed away with a solvent such as water so as not to wash away the precipitated carbon 8, and the surface 2 to be tested is dried (1'). In this state, test surface 2
By visually observing the distribution of central segregation, it is possible to understand the distribution of central segregation. To record central segregation, use Figure 2 (
Either take a photograph of the inspection surface 2 with a camera 6 such as an instant camera that can take close-up pictures as shown in a), or
As shown in Figure (1)), it is better to use an adhesive chip 17, bring it into close contact with the surface 2 to be inspected, extract the precipitated carbon, and then turn it over to create a carbon print.

After this operation, if the test surface 2f is lightly rubbed with abrasive paper, for example, about 1000≠, washed with water, and dried, it is possible to reveal the coagulated structure at the same time as central segregation. However, when carrying out the appearance of this solidified structure, polishing of the test surface 2 before spraying the roughening agent 4 should be performed with a finer polishing material than when only central segregation is revealed.

The continuous cast material temperature suitable for carrying out the present invention depends on the type of non-oxidizing acid and solvent, but is generally Zo.

It can be said that a temperature of about 150°C to 150°C is preferable. If the temperature of the continuously cast material is too high, the solvent will be decomposed by the non-oxidizing acid, and conversely, if the temperature of the continuously cast material is low, the reaction rate will slow down, causing central segregation. This is because it takes time to get out. If the continuous casting material 1 is approximately 150°C or higher, the temperature tW
It is better to carry out the present invention by waiting until the temperature drops, or by cutting the continuously cast piece 1 with gas and cooling it forcedly or naturally at about 150°C. This case is also easy to perform since it does not require the movement of the sample. If the continuously cast material 1 has not cooled down to near room temperature, it is sufficient to heat the surface 2 to be inspected using a hot air dryer or the like after polishing before applying the roughening agent. Since the reaction temperature is raised by t7, central segregation appears quickly.

Next, specific examples of the present invention will be described below.

1 chemical component is (: : 0.01%, 8i: 0.1
6%, λ4n: 229 ratio, P: (1,00q ratio,
s: o, ooi%, 80tA1. : 0.022%,
Ca: 0.0034% The balance consists of iron and unavoidable impurities, and the cross section is y(r160(lnm% t20
When the 0 mm 0 continuous casting moon has cooled to about 1 () 0 °C, the surface to be inspected is polished with a glider] 7. Finally, it is polished with emery paper of about 500≠ for secondary polishing.

Next, the central part of the surface to be inspected is 200 w (W) x 50
Approximately 200 cc of a solubilizing agent mixed with 2 volumes of sulfuric acid and 5 cups of ethylene glycol was applied to the range of +mn (1) using a souffle, immediately washed with water, and after drying, the surface was hand polished with emery paper of about 11 and 1000≠. I took a photo. The time required was approximately 20 minutes, which was significantly shorter than the 4 to 6 hours required by the conventional method.

The photograph of FIG. 3 shows the results of the central segregation test according to the present invention described above. For comparison, central segregation inspection was performed on the continuously cast material using the hydrochloric acid macro method and the Harry Lenoir print method. Since the continuously cast material is a low-sulfur steel, no center segregation can be detected using the Yarso-flint method, and the solidification structure is clearly visible using the hydrochloric acid macro method, as shown in the 4th test. In contrast, the method of the present invention clearly shows central segregation and solidified structure, indicating that it is a rapid testing method and can provide good data.

According to the present invention described above, when inspecting the central segregation of continuously cast materials, a roughening agent is used in which a non-oxidizing acid is dissolved in a non-oxidizing solvent with a low vapor pressure such as polyalcohol. This was applied directly to the continuously cast material to precipitate carbon, and its uneven distribution caused the central part fi to appear.
Central segregation can be directly inspected from the manufactured continuous casting strip without the need for cutting out test pieces, advanced surface processing, or moving to special equipment for inspection, as in the past. Therefore, according to the present invention, the work is extremely simple and the inspection time F9'+9 is extremely short.

Since the appearance of center segregation is clear, it can be grasped reliably, and as a result, it is possible to quickly respond to continuous casting operating conditions, so it is possible to quickly produce iA class steel pipes with less center segregation, which will have an excellent effect. can get.

41V (7) Explanation wJ1 and 2 are explanatory diagrams schematically showing one embodiment of the method for central segregation inspection of continuous castings according to the present invention, and FIG. Figure 4 is a photograph showing the results of a medium heat segregation test using the conventional hydrochloric acid macro method.

l... continuous @ phase, 2... test subject ++7i, 4... state side, 6... camera, 7... adhesive tape, 8... precipitated carbon.

Patent applicant: Nippon Kokan Co., Ltd. Inventor: Takashi Takayoshi Item
Katsuhiko Murakami 1st
Figures (a) (b) Procedural amendment (Director General of the Patent Office) Mr. Kazuo Sugi (Patent 1
1 examination'1)
3 Relationship with the old case for which supplementary IF is to be made 臂 p″1 Applicant (412) Nippon Kokan Co., Ltd. 1 4. Agent 5 Supplement 1 Page 9, line 18 to page 10, line 9 are corrected as follows.

The results of the above-mentioned central segregation test according to the present invention clearly show the central segregation and solidified structure, and it has been demonstrated that the method is a rapid test method and can yield good data.For comparison, I tried the hydrochloric acid macro method and sulfur print method on the continuously cast material, but since the continuously cast material is low sulfur steel, the sulfa print method could not detect any center segregation, and the hydrochloric acid macro method detected no solidified structure. was unclear.'' Lines 8 to 13 of page 11 of the circular are written as follows:
Press fJ.

``Figures 1 and 2 are explanatory diagrams schematically showing one embodiment of the central segregation inspection method for continuously cast materials according to the present invention.'' 3 Figures 3 and 4 have been deleted from the accompanying drawings of this application. do.

Procedural amendment (UNA) Showa <; 2177 July] 4 rivers,, □, ¥1 Waka A':; r-no (special examiner) 1,
Display of the case 3 Relationship between the supplementary IE and the case 1.1 Interview with the applicant
Item F':;ii'i1' i Zhu Shiyunsha 4 Agent 5 Amendment Order 11i = 1 Amendment Contents 1 The "Percentage Allowed Claims" of the present application is corrected as follows.

1. A rapid method for testing central segregation of continuously cast materials, which is characterized by applying a solvent containing a non-oxidizing acid dissolved in the solvent directly to the steel material to make central segregation appear.

2. The rapid central segregation inspection method on the continuous casting side according to claim 1, wherein the non-oxidizing acid is selected from sulfuric acid or phosphoric acid.

3. The rapid central segregation inspection method for continuous cast material according to claim 1, wherein the solvent is selected from polyhydric alcohols such as ethylene glycol.

4. The method for central segregation inspection of continuous cast material according to claim 1, wherein the solvent is applied by a spraying method.

5. When the method of recording the central segregation in the bowl is a photographic method or a carbon printing method using an adhesive tape, the range of r + request is the rapid central segregation test method described in paragraph 1. 2 Specification V of the present application :In the 5th line of page 41, replace ``state side'' with ``
Correct it to solvent J.

3 In the same book, page 5, line 6, the phrase “state side (4)” has been replaced with “solvent (
4) Correct it as J.

In lines 1 and 10 of page 6 of Da Doso, the words ``r agent (4)'' are corrected to ``solvent (4) J.''

Left circular, page 6, line 6, beginning K, ``state side'' is corrected to ``solvent.''

A same book #! Page 7, line 19, correct the phrase ``state side (4)'' in the opening to say ``solvent (4)''.

7 In the same book, page 10, line 13, the words ``state side'' are corrected to read ``solvent.''

On page 11, line 14 of the same book, the phrase ``(4)...State side,'' is corrected to ``(4)...Solvent.''

Claims (1)

[Claims] l. A rapid method for inspecting central segregation of continuously cast materials, characterized in that a non-oxidizing acid dissolved in a solvent is applied directly to the steel material to reveal central segregation. 2. A rapid central segregation test method for continuously cast material according to claim 1, wherein the non-oxidizing acid is selected from sulfuric acid or Fissic acid. 3. Polyhydric alcohols including solvent ethylene glycol A rapid central segregation inspection method for a continuous casting iron according to claim 1, which is selected from the following. 4. A rapid central segregation inspection method for continuous cast material according to claim 1, wherein the coating on the central side is a spray method. 5. The method for rapidly inspecting central segregation of continuous cast materials according to claim 1, wherein the method for recording the central segregation that has appeared is a photography method or a carbon printing method using an adhesive tape.