JPS61280564A - Method for analyzing carbide in steel - Google Patents

Abstract

PURPOSE:To perform the quantitative analysis classified by form of carbide contained in steel, by decomposing the carbon extraction residue in steel while changing heating temp. to analyze the generated gas. CONSTITUTION:The carbide of the specimen 9 in a reaction furnace is decomposed under heating in an oxygen stream introduced from an oxygen inlet 14 to be sent to a reaction completion furnace 2 as decomposed gas and again heated to be perfectly converted to CO2 which is, in turn, sent to an analyser through a CO2 outlet 28 to measure the amount of CO2. Therefore, by investigating the decomposition temps. of carbides different in decomposition temp. by a form by other measuring means, each carbide contained in an extraction residue can be quantitatively analyzed in a separated state in the thermal decomposition of the reaction furnace 1 by regulating the temp. in the furnace. In this case, the temp. of the reaction completion furnace 2 is set to 350 deg.C or more.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for quantifying carbides contained in steel according to its profile.

BACKGROUND OF THE INVENTION C in conventional steel forms various forms of carbide depending on the metal components constituting the steel and the heat treatment, each of which has a different effect on the properties of the steel. Therefore, G4 ¥ of C in Steel! In order to quantitatively evaluate the influence on t, a method for quantifying carbides in steel depending on their form is required.

Conventionally, total C in steel has been analyzed by burning a steel sample at high temperature in an oxygen stream, converting C into CO, and measuring changes in the amount of infrared absorption and ms degrees due to the CO.

On the other hand, as a method for quantifying carbides in G4 by type, for example, as reported in Iron and Steel, GO (+974>, P., 1962), carbides are separated and extracted from the matrix using a wet chemical separation method. Many methods are used to analyze the metal elements that form carbides, and recently, electrolytic extraction methods using non-aqueous electrolytes have been developed, making it possible to extract even highly unstable carbides with high precision. Ta.

In addition, instead of the above-mentioned wet chemical separation method, there is a method in which C in steel is extracted as CH by heating a steel sample in a hydrogen stream.
Reported in Tetsu to Hagane, 69 (1983), p. 153.

Purpose of the Invention However, in the conventional methods described above, in most cases the wet chemical separation method involves separating the carbide from the matrix and then quantifying the metal elements forming the carbide. Furthermore, in the case of heating in a hydrogen stream, there is a problem that solid solution C and cementite cannot be distinguished.

It is an object of the present invention to solve the above-mentioned conventional problems and to quantify carbides contained in steel by type and deafness.

Structure of the Invention The present invention provides a method for determining the amount of C by burning C in the extraction residue of carbides in steel in an oxygen stream and quantifying the CO, in which the extraction residue of carbides in steel is
In steel, the heating temperature is changed depending on the decomposition temperature of the carbide contained in the residue to decompose it, and then the gas generated by the decomposition is heated to 350°C or higher to convert it into COs, and then analyzed. Concerning methods for analyzing carbides.

FIG. 1 is an explanatory diagram showing an example of the configuration of an apparatus for implementing the present invention, in which a reactor (1) for decomposing carbides and a decomposition gas generated in the reactor (1) are converted into COl. It is composed of reaction completion class (2).

The reactor (indigo) consists of a reactor core tube aυ that opens the sample inlet (13, oxygen population 04, and cracked gas outlet 09), and a heating furnace Oz installed around the reactor core tube aD.
) can be adjusted to the end. 6 Reaction completion class (2) is the cracked gas population (27) and CO8 outlet (28
) and a heating furnace (22) provided around the furnace core tube (26),
is communicated with via cracked gas outlet 09 and cracked gas port (27).

In the analyzer configured as described above, a reactor (f
) The carbide in the crab family (9) was thermally decomposed in the oxygen stream introduced from the oxygen population Q4, sent to the reaction completion group (2) as a decomposed gas, heated again, and completely converted to COl. c via the rear CO3 outlet (28).

2 analyzer (not shown) and GO and ffi are measured. In an apparatus with such a configuration, if the decomposition temperature of each carbide, which has a different decomposition temperature depending on the shape of the decoy, is determined in advance using other measuring means, the temperature inside the furnace can be adjusted when thermally decomposed in the reactor (1). By adjusting the amount, it is possible to separate and quantify each carbide contained in the oil extraction residue.

Figure 2 shows the temperature inside the furnace of the reaction completed class ① and the C that forms carbide.
This is a graph showing the relationship between the rate of conversion to C0Ill (hereinafter referred to as CO8 conversion rate). In the figure, when the furnace temperature is 350° C. or higher, the CO1 conversion rate is 100%. Therefore, if the set temperature of the reactor (1) is low, C will not completely become COl, and the cracked gas will be converted into CO as it is.
Since CO and ffi cannot be accurately quantified even if they are sent to an analyzer, it is necessary to set the temperature of the reaction completion stage (2) to 350°C or higher.

EXAMPLES The present invention will be specifically explained by taking cementite as an example of the carbide in steel.

Steel samples having the compositions shown in Table wE1 were subjected to the heat treatments shown in Table 2 to form Samples A and B, respectively. Show! ! As a result of thermal analysis, comparatively unstable cementite with a decomposition temperature of around 200°C was precipitated in sample A, and a decomposed layer 1 was observed in sample B.
It was confirmed that stable cementite was precipitated around 11j 450''C.

Using the above sample and using 10% acetylacetone-1% tetramethylammonium chloride methyl alcohol solution as the electrolyte, cement it! * was electrolytically extracted, and C was quantified by the method of the present invention.

The equipment used has the configuration shown in Figure ii, and the reactor and reactor core tubes for the reaction completion type both have an inner diameter of λ5° and a length of 3.
A heating furnace was placed around each quartz tube with a soaking area of 10 am. The amount of oxygen gas supplied to the reactor was 1, d/win. As a CO2 analyzer, a Carmhomat Cot analyzer manufactured by Vosthoff was used. The set temperatures of the reactor-furnace were 270°C and 550°C. In other words, two samples are used, one with 27
Set at 0℃, the other one was treated at 400℃ and then 550℃
It was set to 270℃ is the temperature at which relatively unstable cementite, which has a decomposition temperature of around 200℃, is decomposed, and 550℃
℃ is a temperature at which stable cementite, which has a decomposition temperature of around 450 ℃, is decomposed. The temperature of the reaction completion furnace was set at 1000°C. This is because CO1 analyzers are greatly affected by temperature changes.
! Since this is based on conductivity measurement, this is to make the C08 analysis less susceptible to differences in reactor temperature.

The measurement results are converted into the ratio of C (ms+) to the sample (g) and are shown in Table 3. The table also includes the amount of C calculated by the conventional method from the metal component analysis results of the extraction residue after electrolytically extracting carbides. Also shown.

Table 3 shows that while it is not possible to separate and quantify unstable cementite and stable cementite using the conventional method, the method of the present invention allows the separation and quantitative determination of these cementites, and the annealing temperature is 500°C. In sample A, unstable cementite was formed, whereas the annealing temperature was 70°C.
7 shows that most of the B sample at 0°C is stable cementite.

Table 1 Table 2 Table 3 Detailed description of the invention As described above, when analyzing carbides in steel, the carbide extraction residue is thermally decomposed at around the decomposition temperature of the carbides contained therein, and then the cracked gas is converted to COl. By the method of the present invention, which analyzes CO after conversion, it is possible to quantify carbides according to their shape, and it is possible to quantitatively evaluate the influence of C in steel on steel quality with high accuracy.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an example of the configuration of an apparatus for implementing the present invention, and FIG. 2 is a graph showing the relationship between furnace temperature and CO8 conversion rate. 1... Reaction furnace 2... Reaction completion furnace] 1...
・Furnace core tube 12.22... Heating furnace I3...
Sample population 14...Oxygen inlet +5...Cracked gas outlet 26...Furnace tube 27...Cracked gas population
28...CO8 outlet 9...Sample applicant Sumitomo Metal Industries, Ltd. Figure 1'$2 Figure 4 (H)

Claims (1)

[Claims] The carbon in the carbide extraction residue in steel is combusted in an oxygen stream to produce CO.
In this method, the amount of C is determined by converting CO_2 into The gas generated by
A method for analyzing carbides in steel, which comprises heating and converting into CO_2 and then analyzing.