JP2005114626A - Corrosive liquid for exposing austenitic grain boundary - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a corrosive liquid capable of exposing precisely and easily an austenitic grain boundary of a boron steel or a quenching material for a high-carbon chromium bearing steel or the like instead of a conventional corrosive liquid. <P>SOLUTION: This corrosive liquid for exposing the austenitic grain boundary of the boron steel or the austenitic grain boundary of the quenching material for the high-carbon chromium bearing steel is prepared by dissolving picric acid 15-25 g in water 400 ml, adding thereto 20-40 ml of detergent 'LIPON F'(R), and adding thereto 4-10 g sodium dodecyl benzenesulfonate as a surfactant. The figure shows 400-power and 1,000-power microphotographs of the austenitic grain boundary of the boron steel exposed by the corrosive liquid. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a corrosive solution for a steel surface used for revealing grain boundaries such as hardened materials of boron steel or high carbon chromium bearing steel, particularly austenite grain boundaries.

  It is indispensable to reveal the solidification structure of steel or the metal structure such as hardened material in order to understand the solidification state of steel and the structure of hardened material. Very important. As a method for revealing such a solidified structure of steel, for example, a. For ordinary steel, including low-carbon steel, etc., heat a corrosive solution containing 2 to 3 drops of detergent such as Raipon F (trade name: Lion Oil) to 1 liter of a saturated aqueous solution of picric acid to 80 ° C. A method of immersing a sample taken from a steel piece and mirror-polished for 1 to 3 minutes is known. (See Non-Patent Document 1 and Non-Patent Document 2). b. On the other hand, as a method for revealing dendrites of ultra low carbon steel slabs having a carbon concentration of 50 ppm or less, a sample is heated to 700 ° C. or more and 780 ° C. or less, and then the cooled sample is etched by etching with a corrosive liquid. Is known (see Patent Document 1).

  Furthermore, the applicant dissolved 6-8 g of picric acid in 500 ml of hot water at 60 to 80 ° C. as a corrosive solution for revealing the dendrite of the solidified structure of the carbon steel or low alloy steel slab. 3-5 ml of this detergent is added, and 2-4 g of sodium dodecylbenzenesulfonate is added as a surfactant (see Patent Document 2).

  By the way, etching for revealing the austenite grain size is usually performed with a saturated picric acid aqueous solution and Lipon F, but austenite grain boundaries such as hardened materials of boron steel or high carbon chromium bearing steel are sufficiently revealed. However, there was a problem of chemical corrosion by chemicals through trial and error.

JP-A-7-120457 JP 2001-289839 A Yoshiki Gunji and Taira Okamoto, “Iron and Steel” 61 (1975), p. 886 Edited by the Japan Iron and Steel Institute, “Iron Handbook 1 Basics”, S56, published by Maruzen, p. 207

  Therefore, the appearance of austenite grain boundaries such as a hardened material of boron steel or high carbon chromium bearing steel is corroded with a corrosive solution composed of a boiling picric acid aqueous solution, sodium dodecylbenzenesulfonate and hydrogen peroxide. When this corrosive solution is used, the crystal grains can be clearly revealed. However, since the corrosive liquid is a boiling type, the consumption of the corrosive liquid and the change in composition are severe, and the corrosive time is as short as 30 seconds. Therefore, it is difficult to control the degree of corrosion and it is difficult to use.

  Therefore, the problem to be solved by the present invention is to replace the corrosive liquid with a corrosive liquid capable of accurately and easily revealing austenite grain boundaries such as a hardened material of boron steel or high carbon chromium bearing steel. Is to provide.

The means of the present invention for solving the above-mentioned problems is that, in the invention of claim 1, picric acid is used for 400 ml of H ₂ O in a corrosive solution that reveals the austenite grain boundaries of the hardened material of boron steel. It is characterized by adding 15 to 25 g of detergent, adding 20 to 40 ml of detergent Rypon F (trade name: manufactured by Lion Oil), and adding 4 to 10 g of sodium dodecylbenzenesulfonate as a surfactant. This is a corrosive solution for revealing austenite grain boundaries. In addition, the boron steel in this invention has pointed out the steel for machine structures which consists of steel which contains B 0.0005% or more by mass%.

In the invention of claim 2, 15-25 g of picric acid is dissolved in 400 ml of H ₂ O in a corrosive solution that reveals the austenite grain boundaries of the hardened material of high-carbon chromium bearing steel, and a detergent No. Raipon F (trade name: manufactured by Lion Yushi) 20-40 ml, and 4-10 g of sodium dodecylbenzenesulfonate as a surfactant is further added. Corrosive solution for revealing austenite grain boundaries It is. In addition, the high carbon chromium bearing steel in this invention means SUJ steel prescribed | regulated by JIS.

  By using the austenite grain boundary revealing corrosion liquid of the present invention, the hardened material of the high carbon chromium bearing steel, which is a boron steel or non-boron steel, which has been difficult to reveal only with the above-described boiling type. Appearance of austenite grain boundaries can be obtained accurately and easily with the same operation as in the case of conventional Lipon F and saturated picric acid aqueous solution used for the appearance of dendrites of low carbon steel slabs. It became so.

The best mode for carrying out the present invention will be described with reference to the drawings. FIG. 1 (a) is a photomicrograph showing the austenite grain boundary of boron steel revealed by the corrosive solution for revealing austenite grain boundaries in the present invention at 400 times, and FIG. 1 (b) is a diagram in the present invention. It is a microscope picture which shows the austenite grain boundary of boron steel revealed with the corrosive liquid for austenite grain boundary appearance by 1000 time. FIG. 2 (a) is a photomicrograph showing the austenite grain boundary of boron steel revealed by a corrosive liquid having a composition different from that of the present invention at a magnification of 400, and FIG. The corrosive liquid is a photomicrograph showing the austenite grain boundary of boron steel revealed by a corrosive liquid having a different composition at a magnification of 1000 times. FIG. 3 is a photomicrograph showing the austenite grain boundary of the high carbon chromium bearing steel 1000 times as revealed with the austenite grain boundary revealing liquid in the present invention. FIG. 4 is a photomicrograph showing the austenite grain boundary of the high carbon chromium bearing steel 1000 times as revealed by a corrosive liquid having a different composition from the above corrosive liquid of the present invention.
The best mode for carrying out the present invention will be described in comparison with Comparative Example 1 and Comparative Example 2 through Example 1 and Example 2 below.

  The corrosive liquid of the present invention for revealing the austenite grain boundaries of the hardened boron steel is obtained by dissolving 20 g of picric acid, 30 ml of Raipon F, and 6 g of sodium dodecylbenzenesulfonate in 400 ml of water, did.

  The boron steel to which this corrosive liquid is applied is, for example, in mass%, C: 0.20%, Si: 0.11%, Mn: 0.28%, P: 0.012%, S: 0.015% , Cr: 1.05%, Mo: 0.01%, B: 0.0015%, Al: 0.009%, N: 0.0052%, O: 0.0018%, the balance Fe and inevitable Steel made of impurities. The steel specimen made of boron steel is polished to a mirror surface, and then the mirror surface obtained by immersing and polishing in a solution of the above-mentioned corrosion solution at 63 ° C. is etched for 4 minutes to reveal the austenite grain boundaries of boron steel. I put it out. A photograph of the exposed etched surface taken at a magnification of 400 with a microscope is shown in FIG. 1A, and a photograph taken at a magnification of 1000 times is shown in FIG. As can be seen from these micrographs, the austenite grain boundaries of boron steel were clearly revealed without using the conventional boiling type.

  In contrast to this, as Comparative Example 1, the corrosive liquid that reveals the dendrite of the solidified structure of the carbon steel or low alloy steel slab described in Patent Document 2 is applied to the hardened material of boron steel. A preferred austenite grain boundary could not be revealed. Moreover, the effect was confirmed as a comparative example by changing the composition of the corrosive liquid of the present invention. First, 15 g of picric acid was dissolved, 10 ml of detergent such as Lipon F was added thereto, and dissolved in 400 ml of water to obtain a corrosive solution. Next, a mirror surface obtained by polishing a steel specimen of boron steel having the same composition as above to a solution in which the above corrosive solution was heated to 70 ° C. was immersed in the same manner as above and etched for 4 minutes to obtain a microscope specimen. . FIG. 2A shows a photograph taken at 400 times the etched surface of this specimen with a microscope, and FIG. 2B shows a photograph taken at a magnification of 1000 times. As can be seen from these micrographs, the austenite grain boundaries of boron steel could not be clearly revealed with the corrosion solution of this comparative example.

  The corrosive liquid of the present invention for revealing the austenite grain boundaries of the hardened material of SUJ2 steel, which is a high carbon chromium bearing steel, is 20 g picric acid, 30 ml rypon F, sodium dodecylbenzene sulfonate as in Example 1. 6 g was dissolved in 400 ml of water to obtain a corrosive solution for etching.

  SUJ2 steel, which is a high carbon chromium bearing steel to which this corrosion solution is applied, is, for example, in mass%, C: 1.00%, Si: 0.30%, Mn: 0.25%, P: 0.015% , S: 0.015%, Cr: 1.40%, and the balance Fe and inevitable impurities. A steel specimen made of a hardened material of this high carbon chromium bearing steel is polished to a mirror surface, and then the mirror surface obtained by polishing in a solution of the above corrosive solution at 65 ° C. is immersed and etched for 40 seconds to obtain an austenite crystal. The grain boundary was revealed. A photograph of the exposed etched surface taken with a microscope at a magnification of 1000 is shown in FIG. As can be seen from this micrograph, the austenite grain boundaries of the hardened material of high carbon chromium bearing steel were clearly revealed.

  In contrast, the corrosive liquid that reveals the dendrite of the solidified structure of the carbon steel or low alloy steel slab described in Patent Document 2 is not suitable for the quenching material of boron steel. The effect was investigated with a corrosive solution. First, 15 g of picric acid was dissolved, 10 ml of detergent such as Lipon F was added thereto, and dissolved in 400 ml of water to obtain a corrosive solution. Next, a steel specimen made of a hardened material with a high carbon chromium bearing steel having the same composition as described above was polished in a solution in which the above corrosive solution was heated to 70 ° C. in the same manner as described above, and the obtained mirror surface was immersed in 4 Etching for a minute to obtain a microscope specimen. FIG. 4 shows a photograph of the etched surface of this specimen taken with a microscope at a magnification of 1000 times. As can be seen in this micrograph, the austenite grain boundaries of the hardened material of the high carbon chromium bearing steel could not be clearly revealed with this corrosion solution.

a) is a micrograph showing 400 times the austenite grain boundary of boron steel revealed by the corrosion liquid for austenite grain boundary revealing in the present invention, and (b) is for austenite grain boundary revealing in the present invention. It is the microscope picture which shows the austenite grain boundary of boron steel revealed with the corrosion liquid of 1000 times. (A) is a photomicrograph showing the austenite grain boundary of boron steel revealed by a corrosive liquid whose composition is changed from that of the present invention at 400 times, and (b) is a composition of the corrosive liquid of the present invention. It is a microscope picture which shows the austenite crystal grain boundary of boron steel revealed with the changed corrosive liquid by 1000 time. It is a microscope picture which shows the austenite crystal grain boundary of the high carbon chromium bearing steel revealed with the corrosive liquid for austenite crystal grain boundary appearance in this invention by 1000 time. The corrosive liquid of the present invention is a photomicrograph showing the austenite grain boundary of a high carbon chromium bearing steel revealed by a corrosive liquid having a different composition at a magnification of 1000 times.

Claims (2)

In a corrosive solution that reveals the austenite grain boundaries of the hardened material of boron steel, 15-25 g of picric acid is dissolved in 400 ml of H ₂ O, and this is the detergent Lipon F (trade name: manufactured by Lion Oil) ) An austenite grain boundary revealing corrosion solution characterized by adding 20 to 40 ml and further adding 4 to 10 g of sodium dodecylbenzenesulfonate as a surfactant. In a corrosion solution that reveals the austenite grain boundaries of the hardened material of high carbon chromium bearing steel, 15 to 25 g of picric acid is dissolved in 400 ml of H ₂ O, and the detergent Lipon F (trade name: A caustic solution for revealing austenite grain boundaries, comprising 20 to 40 ml of Lion Fats and Fats, and 4 to 10 g of sodium dodecylbenzenesulfonate as a surfactant.